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Desert tortoise

January 01, 1970

Not to be confused with Sonoran Desert tortoise.

The desert tortoise (Gopherus agassizii) is a species of tortoise in the family Testudinidae. The species is native to the Mojave and Sonoran Deserts of the southwestern United States and northwestern Mexico, and to the Sinaloan thornscrub of northwestern Mexico.[4] G. agassizii is distributed in western Arizona, southeastern California, southern Nevada, and southwestern Utah.[4] The specific name agassizii is in honor of Swiss-American zoologist Jean Louis Rodolphe Agassiz.[5] The desert tortoise is the official state reptile in California and Nevada. [6]

Desert tortoise
Agassiz's desert tortoise, G. agassizii
CITES Appendix II (CITES)[2]
Scientific classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Order: Testudines
Suborder: Cryptodira
Superfamily: Testudinoidea
Family: Testudinidae
Genus: Gopherus
Species:
G. agassizii
Binomial name
Gopherus agassizii
(Cooper, 1863)
Synonyms[3]
  • Xerobates agassizii Cooper, 1863
  • Testudo agassizii — Cope, 1875
  • Xerobates agassizi [sic] Garman, 1884 (ex errore)
  • Gopherus agassizii — Stejneger, 1893
  • Testudo aggassizi [sic] Ditmars, 1907 (ex errore)
  • Testudo agassizi — Ditmars, 1907
  • Gopherus agassizi — V. Tanner, 1927
  • Testudo agasizzi [sic] Kallert, 1927 (ex errore)
  • Gopherus polyphemus agassizii — Mertens & Wermuth, 1955
  • Gopherus agassiz [sic] Malkin, 1962 (ex errore)
  • Gopherus polyphemus agassizi — Frair, 1964
  • Geochelone agassizii — Honegger, 1980
  • Scaptochelys agassizii — Bramble, 1982
  • Scaptochelys agassizi — Morafka, Aguirre & Murphy, 1994

The desert tortoise lives about 50 to 80 years;[7] it grows slowly and generally has a low reproductive rate. It spends most of its time in burrows, rock shelters, and pallets to regulate body temperature and reduce water loss. It is most active after seasonal rains and is inactive during most of the year. This inactivity helps reduce water loss during hot periods, whereas winter brumation facilitates survival during freezing temperatures and low food availability. Desert tortoises can tolerate water, salt, and energy imbalances on a daily basis, which increases their lifespans.[8]

Taxonomy edit

In 2011, on the basis of DNA, geographic, and behavioral differences between desert tortoises east and west of the Colorado River, it was decided that two species of desert tortoises exist: Agassiz's desert tortoise (Gopherus agassizii) and Morafka's desert tortoise (Gopherus morafkai).[9] The new species name is in honor of the late Professor David Joseph Morafka of California State University, Dominguez Hills, in recognition of his many contributions to the study and conservation of Gopherus. G. morafkai occurs east of the Colorado River in Arizona, as well as in the states of Sonora and Sinaloa, Mexico. The acceptance of G. morafkai reduced the range of G. agassizii by about 70%[10] In 2016, based on a large-scale genetic analysis, ecological and morphological data, researchers proposed a split between the Sonoran and Sinaloan populations. This southernmost member of the Gopherus genus was named G. evgoodei, Goode's thornscrub tortoise.[11]

Description edit

These tortoises may attain a length of 25 to 36 cm (10 to 14 in),[12] with males being slightly larger than females. A male tortoise has a longer gular horn than a female, his plastron (lower shell) is concave compared to a female tortoise. Males have larger tails than females do. Their shells are high-domed, and greenish-tan to dark brown in color. The high domes of their shells allow for space for their lungs, which helps them maintain thermoregulation, also known as maintaining internal temperature.[13] Desert tortoises can grow to 10–15 cm (4–6 in) in height. They can range in weight from 8 to 15 pounds, or 3.5 kg to 7 kg.[14] The front limbs have sharp, claw-like scales and are flattened for digging. Back legs are skinnier and very long.[citation needed]

Habitat edit

Desert tortoises can live in areas with ground temperatures exceeding 60 °C (140 °F)[15] because of their ability to dig burrows and escape the heat. At least 95% of their lives are spent in burrows. There, they are also protected from freezing winter weather while dormant, from November through February or March. Within their burrows, these tortoises create a subterranean environment that can be beneficial to other reptiles, mammals, birds, and invertebrates.

Scientists have divided the desert tortoise into three species: Agassiz's and Morafka's desert tortoises,[16] with a third species, Goode's thornscrub tortoise, in northern Sinaloan and southern Sonora, Mexico.[11] An isolated population of Agassiz's desert tortoise occurs in the Black Mountains of northwestern Arizona.[16] They live in a different type of habitat, from sandy flats to rocky foothills. They have a strong proclivity in the Mojave Desert for alluvial fans, washes, and canyons where more suitable soils for den construction might be found.[17] They range from near sea level to around 1,050 m (3,500 ft) in elevation. Tortoises show very strong site fidelity, and have well-established home ranges where they know where their food, water, and mineral resources are.

Desert tortoises inhabit elevations from below mean sea level in Death Valley to 1,600 m (5,300 ft) in Arizona, though they are most common from around 300 to 1,050 m (1,000 to 3,500 ft). Estimates of densities vary from less than 8/km2 (21/sq mi) on sites in southern California to over 500/km2 (1,300/sq mi) in the western Mojave Desert, although most estimates are less than 150/km2 (390/sq mi). The home range generally consists of 4 to 40 hectares (10 to 100 acres). In general, males have larger home ranges than females, and home range size increases with increasing resources and rainfall.[8]

Desert tortoises are sensitive to the soil type, owing to their reliance on burrows for shelter, reduction of water loss, and regulation of body temperature. The soil should crumble easily during digging and be firm enough to resist collapse. Desert tortoises prefer sandy loam soils with varying amounts of gravel and clay, and tend to avoid sands or soils with low water-holding capacity, excess salts, or low resistance to flooding. They may consume soil to maintain adequate calcium levels, and may prefer sites with higher calcium content.[8]

With the creation of off-road vehicles more humans are making their way in and out of the desert tortoises' home environment.[18]

Shelters edit

Desert tortoises spend most of their lives in burrows, rock shelters, and pallets to regulate body temperature and reduce water loss. Burrows are tunnels dug into soil by desert tortoises or other animals, rock shelters are spaces protected by rocks and/or boulders, and pallets are depressions in the soil. The use of the various shelter types is related to their availability and climate. The number of burrows used, the extent of repetitive use, and the occurrence of burrow sharing are variable. Males tend to occupy deeper burrows than females. Seasonal trends in burrow use are influenced by desert tortoise sex and regional variation. Desert tortoise shelter sites are often associated with plant or rock cover. Desert tortoises often lay their eggs in nests dug in sufficiently deep soil at the entrance of burrows or under shrubs. Nests are typically 8 to 25 centimetres (3 to 10 inches) deep.[8]

Shelters are important for controlling body temperature and water regulation, as they allow desert tortoises to slow their rate of heating in summer and provide protection from cold during the winter. The humidity within burrows prevents dehydration. Burrows also provide protection from predators. The availability of adequate burrow sites influences desert tortoise densities.[8]

Each desert tortoise uses about 5 to 25 burrows per year. Some burrows are used repeatedly, sometimes for several consecutive years. Desert tortoises share burrows with various mammals, reptiles, birds, and invertebrates, such as white-tailed antelope squirrels (Ammospermophilus leucurus), woodrats (Neotoma), collared peccaries (Dicolytes tajacu), burrowing owls (Athene cunicularia), Gambel's quail (Callipepla gambelii ), rattlesnakes (Crotalus spp.), Gila monsters (Heloderma suspectum), beetles, spiders, and scorpions. One burrow can host up to 23 desert tortoises – such sharing is more common for desert tortoises of opposite sexes than for desert tortoises of the same sex.[8]

Lifecycle edit

Reproduction edit

Tortoises mate in the spring and autumn. Male desert tortoises grow two large white glands around the chin area, called chin glands, that signify mating season. A male circles around female, biting her shell in the process. He then climbs upon the female and insert his penis (a white organ, usually only seen upon careful inspection during mating, as it is hidden inside the male and can only be coaxed out with sexual implication) into the cloaca of a female, which is located around the tail. The male may make grunting noises once atop a female, and may move his front legs up and down in a constant motion, as if playing a drum.[failed verification][19]

 
Hatching baby desert tortoise

Months later, the female lays a clutch of four to eight hard-shelled eggs,[20] which have the size and shape of ping-pong balls, usually in June or July. The eggs hatch in August or September. Wild female tortoises produce up to three clutches a year depending on the climate. Their eggs incubate from 90 to 135 days;[4] some eggs may overwinter and hatch the following spring. In a laboratory experiment, temperature influenced hatching rates and hatchling sex. Incubation temperatures from 27 to 31 °C (81 to 88 °F) resulted in hatching rates exceeding 83%, while incubation at 25 °C (77 °F) resulted in a 53% hatching rate. Incubation temperatures less than 31 °C (88 °F) resulted in all-male clutches. Average incubation time decreased from 124.7 days at 25 °C (77 °F) to 78.2 days at 31 °C (88 °F).[21]

The desert tortoise is one of the few known tortoises in existence that has been observed engaging in homosexual intercourse[22] Same-sex intercourse happens in many species, There is no one answer as to why this occurs. One possible explanation for this could be the social component of gaining and establishing dominance.[23]

Maturation edit

The desert tortoise grows slowly, often taking 16 years or longer to reach about 20 cm (8 in) in length. The growth rate varies with age, location, gender and precipitation. It can slow down from 12 mm/year for ages 4–8 years to about 6.0 mm/year for ages 16 to 20 years. Males and females grow at similar rates; females can grow slightly faster when young, but males grow larger than females.[8]

Desert tortoises reach their reproductive maturity at ages 15 to 20, when they become longer than 18 cm (7 in). However, it is possible for them to mature faster as 10-year-old females that are able to reproduce have been observed.[8]

Activity edit

Their activity depends on location, peaking in late spring for the Mojave Desert and in late summer to fall in Sonoran Desert; some populations exhibit two activity peaks during one year. Desert tortoises brumate during winters, roughly from November to February–April. Females begin brumating later and emerge earlier than males; juveniles emerge from brumation earlier than adults.[8][24]

Temperature strongly influences desert tortoise activity level. Although desert tortoises can survive body temperatures from below freezing to over 40 °C (104 °F), most activity occurs at temperatures from 26 to 34 °C (79 to 93 °F). The influence of temperature is reflected in daily activity patterns, with desert tortoises often active late in the morning during spring and fall, early in the morning and late in the evening during the summer, and occasionally becoming active during relatively warm winter afternoons. The activity generally increases after rainfall.[8]

Although desert tortoises spend the majority of their time in shelter, movements of up to 200 m (660 ft) per day are common. The common, comparatively short-distance movements presumably represent foraging activity, traveling between burrows, and possibly mate-seeking or other social behaviors. Long-distance movements could potentially represent dispersal into new areas and/or use of peripheral portions of the home range.[8]

Lifespan edit

The lifespan of a desert tortoise can vary from 50 to 80 years.[7] The main causes of mortality in desert tortoises include predators, human-related causes, diseases, and environmental factors such as drought, flooding, and fire.[8]

 
Desert tortoise with an estimated age of 63 years. Red Rock Canyon National Conservation Area, NV

The annual death rate of adults is typically a few percent, but is much higher for young desert tortoises. Only 2–5% of hatchlings are estimated to reach maturity. Estimates of survival from hatching to 1 year of age for Mojave Desert tortoises range from 47 to 51%. Survival of Mojave Desert tortoises from 1 to 4 years of age is 71–89%.[8]

Diet edit

 
 
 
A young desert tortoise

The desert tortoise is an herbivore. Grasses form the bulk of its diet, but it also eats herbs, annual wildflowers, and new growth of cacti, as well as their fruit and flowers. Rocks and soil are also ingested, perhaps as a means of maintaining intestinal digestive bacteria as a source of supplementary calcium or other minerals. As with birds, stones may also function as gastroliths, enabling more efficient digestion of plant material in the stomach.[8]

Much of the tortoise's water intake comes from moisture in the grasses and wildflowers they consume in the spring. A large urinary bladder can store over 40% of the tortoise's body weight in water, urea, uric acid, and nitrogenous wastes. During very dry times, they may give off waste as a white paste rather than a watery urine. During periods of adequate rainfall, they drink copiously from any pools they find, and eliminate solid urates. The tortoises can increase their body weight by up to 40% after copious drinking.[25] Adult tortoises can survive a year or more without access to water.[8] During the summer and dry seasons, they rely on the water contained within cactus fruits and mesquite grass. To maintain sufficient water, they reabsorb water in their bladders, and move to humid burrows in the morning to prevent water loss by evaporation.[25]

A desert tortoise can empty its bladder as one of its defense mechanisms.[26] This can leave the tortoise in a very vulnerable condition in dry areas, since the tortoise will no longer have a backup water supply. If a tortoise is seen in the wild, you should not handle, or pick them up unless they are in imminent danger. Handling of tortoises may have consequences for the animal, such as the development of upper respiratory tract infections.[26]

Predation and conservation status edit

Ravens, Gila monsters, kit foxes, badgers, roadrunners, coyotes, and fire ants are all natural predators of the desert tortoise. They prey on eggs, juveniles, which are 50–75 mm (2–3 in) long with a thin, delicate shell, or, in some cases, adults. Ravens are thought to cause significant levels of juvenile tortoise predation in some areas of the Mojave Desert – frequently near urbanized areas.[27] The most significant threats to tortoises include urbanization, disease, habitat destruction and fragmentation, illegal collection and vandalism by humans, and habitat conversion from invasive plant species (Brassica tournefortii, Bromus rubens and Erodium spp.).

Desert tortoise populations in some areas have declined by as much as 90% since the 1980s, and the Mojave population is listed as threatened under the Endangered Species Act of 1973 in 1990,[28] after being listed as endangered, or threatened in the case of the Beaver Dam Slope, Utah population, under an emergency rule in 1989.[29] All desert tortoises are protected under law of the United States based on similarity of appearance to tortoises of the protected Mojave population.[30] It is unlawful to touch, harm, harass, or collect wild desert tortoises. It is, however, possible to adopt captive tortoises through the Tortoise Adoption Program in Arizona, Utah Division of Wildlife Resources Desert Tortoise Adoption Program in Utah, Joshua Tree Tortoise Rescue Project in California, or through Bureau of Land Management in Nevada. When adopted in Nevada, they will have a computer chip embedded on their backs for reference. According to Arizona Game and Fish Commission Rule R12-4-407 A.1, they may be possessed if the tortoises are obtained from a captive source which is properly documented. Commission Order 43: Reptile Notes 3: one tortoise per family member.

The Fort Irwin National Training Center of the US Army expanded into an area that was habitat for about 2,000 desert tortoises, and contained critical desert tortoise habitat (a designation by the US Fish and Wildlife Service). In March 2008, about 650 tortoises were moved by helicopter and vehicle, up to 35 km away.[31] The Desert Tortoise Preserve Committee protects roughly 2,000 hectares (5,000 acres) of desert tortoise habitat from human activity. This area includes 1,760 hectares (4,340 acres) in Kern County, 290 hectares (710 acres) in San Bernardino County, and 32 hectares (80 acres) in Riverside County.[32]

Another potential threat to the desert tortoise's habitat is a series of proposed wind and solar farms.[33] As a result of legislation, solar energy companies have been making plans for huge projects in the desert regions of Arizona, California, Colorado, New Mexico, Nevada, and Utah. The requests submitted to the Bureau of Land Management total nearly 7,300 km2 (1,800,000 acres).[34]

While tortoises are made to withstand tough conditions and high temperatures, they are unable to cope with the dangers of human development, such as the use of off-roading vehicles. These vehicles that come along at high speeds have the potential to crush and kill tortoises, running over their eggs and burrows and significantly impacting their population. [35][verification needed]

Human development edit

Ivanpah solar power project edit

Concerns about the impacts of the Ivanpah Solar thermal project led the developers to hire some 100 biologists and spend US$22 million caring for the tortoises on or near the site during construction.[36][37] Despite this, in a 2011 Revised Biological Assessment for the Ivanpah Solar Electric Generating System, the Bureau of Land Management anticipated the loss or significant degradation of 1,420 hectares (3,520 acres) of tortoise habitat and the harm of 57–274 adult tortoises, 608 juveniles, and 236 eggs inside the work area, and 203 adult tortoises and 1,541 juvenile tortoises outside the work area. The Bureau of Land Management (BLM) expects that most of the juvenile tortoises on the project will be killed.[38][39]

Lawsuits edit

In the summer of 2010, Public Employees for Environmental Responsibility filed a lawsuit against the National Park Service for not having taken measures to manage tortoise shooting in the Mojave National Preserve of California. Biologists discovered numerous gunshot wounds (holes) on dead tortoise shells which could likely have been caused long after natural death as these shells can take five years to disintegrate and make useful targets for well intentioned target shooters. These shells left behind by nature, droughts, roadkill, or vandals may have attracted ravens and threatened the healthy tortoises as any predator bird need only feed once on a small tortoise to remember it as a viable food source.[40] The National Park Service did not take the measures they were urged to. They responded with "We simply do not believe that such regulations are warranted at this time." and no further action has been taken.[41]

Diseases edit

Reptiles are known to become infected by a wide range of pathogens, which includes viruses, bacteria, fungi, and parasites. More specifically, the G. agassizii population has been negatively affected by upper respiratory tract disease, cutaneous dyskeratosis, herpes virus, shell necrosis, urolithiasis (bladder stones), and parasites.[42][43][44]

Upper respiratory tract disease edit

Upper respiratory tract disease (URTD) is a chronic, infectious disease responsible for population declines across the entire range of the desert tortoise. It was identified in the early 1970s in captive desert tortoise populations, and later identified in the wild population.[42] URTD is caused by the infectious agents Mycoplasma agassizii and Mycoplasma testudineum, which are bacteria in the class Mollicutes and characterized by having no cell wall and a small genome.[45][46][47]

Mycoplasmae appear to be highly virulent (infectious) in some populations, while chronic, or even dormant in others.[48] The mechanism (whether environmental or genetic) responsible for this diversity is not understood. Infection is characterized by both physiological and behavioral changes: nasal and ocular discharge, palpebral edema (swelling of the upper and/or lower palpebra, or eyelid, the fleshy portion that is in contact with the tortoises eye globe) and conjunctivitis, weight loss, changes in color and elasticity of the integument, and lethargic or erratic behavior.[42][49][50][51] These pathogens are likely transmitted by contact with an infected individual. Epidemiological studies of wild desert tortoises in the western Mojave Desert from 1992 to 1995 showed a 37% increase in M. agassizii.[47] Tests were conducted on blood samples, and a positive test was determined by the presence of antibodies in the blood, defined as being seropositive.

Cutaneous dyskeratosis edit

Cutaneous dyskeratosis (CD) is a shell disease of unknown origin and has unknown implications on desert tortoise populations. Observationally, it is typified by shell lesions on the scutes. Areas infected with CD appear discolored, dry, rough and flakey, with peeling, pitting, and chipping through multiple cornified layers.[52] Lesions are usually first located on the plastron (underside) of the tortoises, although lesions on the carapace (upper side) and fore limbs are not uncommon. In advanced cases, exposed areas become infected with bacteria, fungi, and exposed tissue and bone may become necrotic.[50][52] CD was evident as early as 1979 and was initially identified on the Chuckwalla Bench Area of Critical Environmental Concern in Riverside County, California.[53] Currently, the means of transmission are unknown, although hypotheses include autoimmune diseases, exposure to toxic chemicals (possibly from mines, or air pollution), or a deficiency disease (possibly resulting from tortoises consuming low-quality invasive plant species instead of high-nutrient native plants).[43][48]

Impacts of disease edit

Two case studies outlined the spread of disease in desert tortoises. The Daggett Epidemiology of Upper Respiratory Tract Disease project, which provides supporting disease research for the Fort Irwin translocation project, lends an example of the spread of disease. In 2008, 197 health evaluations were conducted, revealing 25.0–45.2% exposure to M. agassizii and M. testudineum, respectively, in a core area adjacent to Interstate 15. The spread of disease was tracked over two years, and clinical signs of URTD spread from the core area to adjacent, outlying locations during this time. Overlaying home ranges and the social nature of these animals, suggests that disease-free individuals may be vulnerable to spread of disease, and that transmission can occur rapidly.[54] Thus, wild tortoises that are close to the urban-wildlife interface may be vulnerable to spread of disease as a direct result of human influence.

The second study indicated that captive tortoises can be a source of disease to wild Agassiz's desert tortoise populations. Johnson et al. (2006) tested blood samples for URTD (n = 179) and herpesvirus (n = 109) from captive tortoises found near Barstow, CA and Hesperia, CA. Demographic and health data were collected from the tortoises, as well from other reptiles housed in the same facility. Of these, 45.3% showed signs of mild disease, 16.2% of moderate disease, and 4.5% of severe disease, and blood tests revealed that 82.7% of tortoises had antibodies to mycoplasma, and 26.6% had antibodies to herpesvirus (which means the tortoises were seropositive for these two diseases, and indicate previous exposure to the causative agents). With an estimated 200,000 captive desert tortoises in California, their escape or release into the wild is a real threat to uninfected wild populations of tortoises. Projections from this study suggest that about 4400 tortoises could escape from captivity in a given year, and with an 82% exposure rate to URTD, the wild population may be at greater risk than previously thought.[55]

Domestic pets edit

Edwards et al. reported that 35% of desert tortoises in the Phoenix area are hybrids between either Gopherus agassizii and G. morafkai, or G. morafkai and the Texas tortoise, G. berlandieri. The intentional or accidental release of these tortoises could have dire consequences for wild tortoises.[56]

Before obtaining a desert tortoise as a pet, it is best to check the laws and regulations of the local area and/or state. Desert tortoises may not be captured from the wild. They may, however, be given as a gift from one private owner to another. Desert tortoises need to be kept outdoors in a large area of dry soil and with access to vegetation and water. An underground den and a balanced diet are crucial to the health of captive tortoises.

Management activities and spread of disease edit

 
Tortoise Monitoring and Research at Joshua Tree National Park

Research edit

Wild populations of tortoises must be managed effectively to minimize the spread of diseases, which includes research and education. Despite significant research being conducted on desert tortoises and disease, a considerable knowledge gap still exists in understanding how disease affects desert tortoise population dynamics. It is not known if the population would still decline if disease were completely absent from the system; are tortoises more susceptible to disease during drought conditions? How does a non-native diet impact a tortoise's ability to ward off pathogens? What are the causes of immunity exhibited by some desert tortoises? The 2008 USFWS draft recovery plan suggests that populations of tortoises that are uninfected, or only recently infected, should likely be considered research and management priorities. Tortoises are known to show resistance to disease in some areas, an effort to identify and maintain these individuals in the populations is essential. Furthermore, increasing research on the social behavior of these animals, and garnering a greater understanding of how behavior facilitates disease transmission would be advantageous in understanding rates of transmission. Finally, translocation of tortoises should be done with extreme caution; disease is typically furtive and moving individuals or populations of tortoises across a landscape can have unforeseen consequences.[48]

Education edit

As a corollary to research, education may help prevent captive tortoises from coming into contact with wild populations.[55] Education campaigns through veterinarians, government agencies, schools, museums, and community centers throughout the range of the desert tortoise could limit the spread of tortoise diseases into wild populations. Strategies may include encouraging people to not breed their captive tortoises, ensure that different species of turtles and tortoises are not housed in the same facility (which would help to prevent the spread of novel diseases into the desert tortoise population), ensure captive tortoises are adequately housed to prevent them from escaping into the wild, and to ensure that captive turtles and tortoises are never released into the wild.

Desert tortoises have been severely affected by disease. Both upper respiratory tract disease and cutaneous dyskeratosis have caused precipitous population declines and die-offs across the entire range of this charismatic species. Both of these diseases are extremely likely to be caused by people, and URTD is easily linked with people releasing captive tortoises into the wild. The combination of scientific research and public education is imperative to curb the spread of disease and aid the tortoise in recovery.

State reptile edit

The desert tortoise is the state reptile of California and Nevada.

  •  
    Closeup of desert tortoise at Red Rock Canyon National Conservation Area, 2020
  •  
    Same desert tortoise at Red Rock Canyon NCA showing habitat, 2020
  •  
    Front view closeup of desert tortoise at Red Rock Canyon NCA, 2020
  •  
    Photo showing rocky habitat of Desert tortoise at Red Rock Canyon NCA, 2020

References edit

  This article incorporates public domain material from Gopherus agassizii . United States Forest Service.

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  24. ^ Deane K. (2018). "The 'hibernation' process and post 'hibernation' care of tortoises". Veterinary Nursing Journal. 33 (7): 197–200. doi:10.1080/17415349.2018.1466670. S2CID 59535431.
  25. ^ a b Auffenberg, Walter (1969). Tortoise Behavior and Survival. Chicago: Rand McNally. OCLC 2583084.
  26. ^ a b "Desert Tortoise (Gopherus agassizii)". Mojave National Preserve California. National Park Service. March 21, 2022. Retrieved May 11, 2023.
  27. ^ Sahagun, Louis (June 10, 2019). "These tortoise-killing ravens are so smart, scientists must use drones to stop them". Los Angeles Times. Retrieved June 10, 2019.
  28. ^ Hohman, Judy; Stine, Peter; Bransfield, Ray; Kramer, Karla; U.S. Fish and Wildlife Service (1990). "Endangered and Threatened Wildlife and Plants; Determination of Threatened Status for the Mojave Population of the Desert Tortoise". Federal Register. 55 (63): 12178–12191. 55 FR 12178
  29. ^ Campbell, Jackie; U.S. Fish and Wildlife Service (1989). "Endangered and Threatened Wildlife and Plants; Emergency Determination of Endangered Status for the Mojave Population of the Desert Tortoise". Federal Register. 54 (149): 32326–32331. 54 FR 32326
  30. ^ "Desert tortoise (Gopherus agassizii)". Environmental Conservation Online System. U.S. Fish & Wildlife Service. Retrieved April 28, 2024.
  31. ^ Sahagun, Louis (2008-10-11) "Army suspends relocation of Ft. Irwin tortoises". Los Angeles Times
  32. ^ Connor, Michael J., and Mark Massar, "Megadump Initiative Threat to DTNA" and "2005 Annual Report Desert Tortoise Preserve Committee Accomplishments & Activities", "Tortoise Tracks." April 2006
  33. ^ Simon, Richard (2009-03-25) Feinstein wants desert swath off-limits to solar, wind projects, Los Angeles Times
  34. ^ Woody, Todd (2009-07-13) A Solar Land Rush, The New York Times
  35. ^ Glass-Godwin (April 2002). "DESERT SURVIVOR?". Science Reference Center.
  36. ^ Dini, Jack (2010-10-31) Desert Tortoises Get Trumped by California's Solar Plants. Hawaii Reporter
  37. ^ Desert Tortoise Care at the Ivanpah Solar Project 2012-06-09 at the Wayback Machine. ivanpahsolar.com (2012-03-06)
  38. ^ Bureau of Land Management (2011-4-19) Revised Biological Assessment for the Ivanpah Solar Electric Generating System (Ivanpah SEGS) Project 2013-10-21 at the Wayback Machine. U.S. Department of the Interior
  39. ^ Ertz, Brian (2011-4-29) Ivanpah solar project would disturb thousands of desert tortoises. The Wildlife News
  40. ^ Stade, Kristen (2010-07-28) Lawsuit to protect varmints in Mojave National Preserve October 21, 2013, at the Wayback Machine, Peer
  41. ^ Jarvis Mojave letter 2011
  42. ^ a b c Jacobson, E. R., J. M. Gaskin, M. B. Brown, R. K. Harris, C. H. Gardiner, J. L. Lapointe, H. P. Adams, and C. Reggiardo (1991). "Chronic upper respiratory tract disease of free ranging desert tortoises (Xerobates agassizii )". Journal of Wildlife Diseases. 27 (2): 296–316. doi:10.7589/0090-3558-27.2.296. PMID 2067052. S2CID 42473017.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  43. ^ a b Jacobson, E. R.; T. J. Wronski; J. Schumacher; C. Reggiardo & K. H. Berry (1994). "Cutaneous dyskeratosis in free ranging desert tortoises, Gopherus agassizii, in the Colorado Desert of Southern California". Journal of Zoo and Wildlife Medicine. 25 (1): 68–81. JSTOR 20095336.
  44. ^ Berry, K. H., E. K. Spangenberg, B. L. Homer, and E. R. Jacobson (2002). "Deaths of desert tortoises following periods of drought and research manipulation" (PDF). Chelonian Conservation and Biology. 4: 436–448.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  45. ^ Brown, M. B., I. M. Schumacher, P. A. Klein, K. Harris, T. Correll, and E. R. Jacobson (1994). "Mycoplasma agassizii causes upper respiratory tract disease in the desert tortoise". Infection and Immunity. 62 (10): 4580–4586. doi:10.1128/iai.62.10.4580-4586.1994. PMC 303146. PMID 7927724.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  46. ^ Berry, K. H. and J. Van Abbema. 1997. Demographic consequences of disease in two desert tortoise populations in California, USA. Proceedings: conservation, restoration, and management of tortoises and turtles – an international conference 11–16 July 1993, State University of New York, Purchase, New York, USA.: 91–99
  47. ^ a b Brown, M. B., K. H. Berry, I. M. Schumacher, K. A. Nagy, M. M. Christopher, and P. A. Klein (1999). "Seroepidemiology of upper respiratory tract disease in the desert tortoise in the western Mojave Desert of California". Journal of Wildlife Diseases. 35 (4): 716–727. doi:10.7589/0090-3558-35.4.716. PMID 10574531. S2CID 22509874.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  48. ^ a b c Draft revised recovery plan for the Mojave population of the desert tortoise (Gopherus agassizii ). U.S. Fish and Wildlife Service, California and Nevada Region, Sacramento, California (2008).
  49. ^ Schumacher, I. M.; M. B. Brown; E. R. Jacobson; B. R. Collins & P. A. Klein (1993). "Detection of antibodies to a pathogenic mycoplasma in desert tortoises (Gopherus agassizii ) with upper respiratory tract disease". Journal of Clinical Microbiology. 31 (6): 1454–1460. doi:10.1128/jcm.31.6.1454-1460.1993. PMC 265561. PMID 8314986.
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  51. ^ Berry, K. H.; M. M. Christopher (2001). "Guidelines for the field evaluation of desert tortoise health and disease". Journal of Wildlife Diseases. 37 (3): 427–450. doi:10.7589/0090-3558-37.3.427. PMID 11504217. S2CID 6952651.
  52. ^ a b Homer, B. L.; C. Li; K. H. Berry; N. D. Denslow; E. R. Jacobson; R. H. Sawyer & J. E. Williams (2001). "Soluble scute proteins of healthy and ill desert tortoises (Gopherus agassizii )". American Journal of Veterinary Research. 62 (1): 104–110. doi:10.2460/ajvr.2001.62.104. PMID 11197546.
  53. ^ Jacobson, E. R. (1994). "Causes of mortality and diseases in tortoises – A review". Journal of Zoo and Wildlife Medicine. 25 (1): 2–17. JSTOR 20095329.
  54. ^ Mack, J. and K. H. Berry. 2009. Development of an epidemiological model of upper respiratory tract disease (Mysoplasmosis) in desert tortoises using the Daggett study area: Year 2, 2008. Proceedings of the thirty-fourth annual meeting and symposium. The desert tortoise council
  55. ^ a b Johnson, A. J.; D. J. Morafka & E. R. Jacobson (2006). (PDF). Journal of Arid Environments. 67: 192–201. Bibcode:2006JArEn..67..192J. doi:10.1016/j.jaridenv.2006.09.025. Archived from the original (PDF) on May 16, 2013. Retrieved January 6, 2013.
  56. ^ Edwards, T., C. J. Jarchow, C. A. Jones, and K. E. Bonine (2010). "Tracing Genetic Lineages of Captive Desert Tortoises in Arizona". Journal of Wildlife Management. 74 (4): 801–807. Bibcode:2010JWMan..74..801E. doi:10.2193/2009-199. S2CID 86409153.{{cite journal}}: CS1 maint: multiple names: authors list (link)

External links edit

 
Wikimedia Commons has media related to Gopherus agassizii.
  • "Gopherus agassizii ". Integrated Taxonomic Information System. Retrieved February 6, 2006.
  • The Desert Tortoise
  • The Arizona-Sonora Desert Museum
  • Desert Tortoise, National Park Service
  • , Mojave Desert Ecosystem Program
  • Desert Tortoise documentary video: The Desert Tortoise: A Delicate Balance, NASA Dryden
  • Desert Tortoise Council

Further reading edit

  • Behler JL, King FW (1979). The Audubon Society Field Guide to North American Reptiles and Amphibians. New York: Alfred A. Knopf. 743 pp. ISBN 0-394-50824-6. (Gopherus agassizii, pp. 471–472 + Plate 328).
  • Boulenger GA (1889). Catalogue of the Chelonians, Rhynchocephalians, and Crocodiles in the British Museum (Natural History). New Edition. London: Trustees of the British Museum (Natural History). (Taylor and Francis, printers). x + 311p. + Plates I-III. (Testudo agasizii, p. 156).
  • Cooper JG (1861). "New California Animals". Proc. California Acad. Sci. 2: 118-123. (Xerobates agassizii, new species, pp. 120–121).
  • Goin CJ, Goin OB, Zug GR (1978). Introduction to Herpetology, Third Edition. San Francisco: W.H. Freeman. xi + 378 pp. ISBN 0-7167-0020-4. (Gopherus agassizi, p. 155).
  • Smith HM, Brodie ED Jr (1982). Reptiles of North America: A Guide to Field Identification. New York: Golden Press. 240 pp. ISBN 0-307-13666-3 (paperback), ISBN 0-307-47009-1 (hardcover). (Gopherus agassizi, pp. 62–63).
  • Stebbins RC (2003). A Field Guide to Western Reptiles and Amphibians, Third Edition. The Peterson Field Guide Series ®. Boston and New York: Houghton Mifflin. xiii + 533 pp. ISBN 978-0-395-98272-3. (Gopherus agassizii, pp. 255–257 + Plate 22 + Map 63).
  • Stejneger L, Barbour T (1917). A Check List of North American Amphibians and Reptiles. Cambridge, Massachusetts: Harvard University Press. 125 pp. (Gopherus agassizii, p. 121).

January 01, 1970
desert, tortoise, confused, with, sonoran, desert, tortoise, gopherus, agassizii, species, tortoise, family, testudinidae, species, native, mojave, sonoran, deserts, southwestern, united, states, northwestern, mexico, sinaloan, thornscrub, northwestern, mexico. Not to be confused with Sonoran Desert tortoise The desert tortoise Gopherus agassizii is a species of tortoise in the family Testudinidae The species is native to the Mojave and Sonoran Deserts of the southwestern United States and northwestern Mexico and to the Sinaloan thornscrub of northwestern Mexico 4 G agassizii is distributed in western Arizona southeastern California southern Nevada and southwestern Utah 4 The specific name agassizii is in honor of Swiss American zoologist Jean Louis Rodolphe Agassiz 5 The desert tortoise is the official state reptile in California and Nevada 6 Desert tortoise Agassiz s desert tortoise G agassizii Conservation status Critically Endangered IUCN 3 1 1 CITES Appendix II CITES 2 Scientific classification Domain Eukaryota Kingdom Animalia Phylum Chordata Class Reptilia Order Testudines Suborder Cryptodira Superfamily Testudinoidea Family Testudinidae Genus Gopherus Species G agassizii Binomial name Gopherus agassizii Cooper 1863 Synonyms 3 Xerobates agassizii Cooper 1863 Testudo agassizii Cope 1875 Xerobates agassizi sic Garman 1884 ex errore Gopherus agassizii Stejneger 1893 Testudo aggassizi sic Ditmars 1907 ex errore Testudo agassizi Ditmars 1907 Gopherus agassizi V Tanner 1927 Testudo agasizzi sic Kallert 1927 ex errore Gopherus polyphemus agassizii Mertens amp Wermuth 1955 Gopherus agassiz sic Malkin 1962 ex errore Gopherus polyphemus agassizi Frair 1964 Geochelone agassizii Honegger 1980 Scaptochelys agassizii Bramble 1982 Scaptochelys agassizi Morafka Aguirre amp Murphy 1994 The desert tortoise lives about 50 to 80 years 7 it grows slowly and generally has a low reproductive rate It spends most of its time in burrows rock shelters and pallets to regulate body temperature and reduce water loss It is most active after seasonal rains and is inactive during most of the year This inactivity helps reduce water loss during hot periods whereas winter brumation facilitates survival during freezing temperatures and low food availability Desert tortoises can tolerate water salt and energy imbalances on a daily basis which increases their lifespans 8 Contents 1 Taxonomy 2 Description 3 Habitat 3 1 Shelters 4 Lifecycle 4 1 Reproduction 4 2 Maturation 4 3 Activity 4 4 Lifespan 4 5 Diet 4 6 Predation and conservation status 5 Human development 5 1 Ivanpah solar power project 6 Lawsuits 7 Diseases 7 1 Upper respiratory tract disease 7 2 Cutaneous dyskeratosis 7 3 Impacts of disease 8 Domestic pets 8 1 Management activities and spread of disease 8 1 1 Research 8 1 2 Education 9 State reptile 10 References 11 External links 12 Further readingTaxonomy editIn 2011 on the basis of DNA geographic and behavioral differences between desert tortoises east and west of the Colorado River it was decided that two species of desert tortoises exist Agassiz s desert tortoise Gopherus agassizii and Morafka s desert tortoise Gopherus morafkai 9 The new species name is in honor of the late Professor David Joseph Morafka of California State University Dominguez Hills in recognition of his many contributions to the study and conservation of Gopherus G morafkai occurs east of the Colorado River in Arizona as well as in the states of Sonora and Sinaloa Mexico The acceptance of G morafkai reduced the range of G agassizii by about 70 10 In 2016 based on a large scale genetic analysis ecological and morphological data researchers proposed a split between the Sonoran and Sinaloan populations This southernmost member of the Gopherus genus was named G evgoodei Goode s thornscrub tortoise 11 Description editThese tortoises may attain a length of 25 to 36 cm 10 to 14 in 12 with males being slightly larger than females A male tortoise has a longer gular horn than a female his plastron lower shell is concave compared to a female tortoise Males have larger tails than females do Their shells are high domed and greenish tan to dark brown in color The high domes of their shells allow for space for their lungs which helps them maintain thermoregulation also known as maintaining internal temperature 13 Desert tortoises can grow to 10 15 cm 4 6 in in height They can range in weight from 8 to 15 pounds or 3 5 kg to 7 kg 14 The front limbs have sharp claw like scales and are flattened for digging Back legs are skinnier and very long citation needed Habitat editDesert tortoises can live in areas with ground temperatures exceeding 60 C 140 F 15 because of their ability to dig burrows and escape the heat At least 95 of their lives are spent in burrows There they are also protected from freezing winter weather while dormant from November through February or March Within their burrows these tortoises create a subterranean environment that can be beneficial to other reptiles mammals birds and invertebrates Scientists have divided the desert tortoise into three species Agassiz s and Morafka s desert tortoises 16 with a third species Goode s thornscrub tortoise in northern Sinaloan and southern Sonora Mexico 11 An isolated population of Agassiz s desert tortoise occurs in the Black Mountains of northwestern Arizona 16 They live in a different type of habitat from sandy flats to rocky foothills They have a strong proclivity in the Mojave Desert for alluvial fans washes and canyons where more suitable soils for den construction might be found 17 They range from near sea level to around 1 050 m 3 500 ft in elevation Tortoises show very strong site fidelity and have well established home ranges where they know where their food water and mineral resources are Desert tortoises inhabit elevations from below mean sea level in Death Valley to 1 600 m 5 300 ft in Arizona though they are most common from around 300 to 1 050 m 1 000 to 3 500 ft Estimates of densities vary from less than 8 km2 21 sq mi on sites in southern California to over 500 km2 1 300 sq mi in the western Mojave Desert although most estimates are less than 150 km2 390 sq mi The home range generally consists of 4 to 40 hectares 10 to 100 acres In general males have larger home ranges than females and home range size increases with increasing resources and rainfall 8 Desert tortoises are sensitive to the soil type owing to their reliance on burrows for shelter reduction of water loss and regulation of body temperature The soil should crumble easily during digging and be firm enough to resist collapse Desert tortoises prefer sandy loam soils with varying amounts of gravel and clay and tend to avoid sands or soils with low water holding capacity excess salts or low resistance to flooding They may consume soil to maintain adequate calcium levels and may prefer sites with higher calcium content 8 With the creation of off road vehicles more humans are making their way in and out of the desert tortoises home environment 18 Shelters edit Desert tortoises spend most of their lives in burrows rock shelters and pallets to regulate body temperature and reduce water loss Burrows are tunnels dug into soil by desert tortoises or other animals rock shelters are spaces protected by rocks and or boulders and pallets are depressions in the soil The use of the various shelter types is related to their availability and climate The number of burrows used the extent of repetitive use and the occurrence of burrow sharing are variable Males tend to occupy deeper burrows than females Seasonal trends in burrow use are influenced by desert tortoise sex and regional variation Desert tortoise shelter sites are often associated with plant or rock cover Desert tortoises often lay their eggs in nests dug in sufficiently deep soil at the entrance of burrows or under shrubs Nests are typically 8 to 25 centimetres 3 to 10 inches deep 8 Shelters are important for controlling body temperature and water regulation as they allow desert tortoises to slow their rate of heating in summer and provide protection from cold during the winter The humidity within burrows prevents dehydration Burrows also provide protection from predators The availability of adequate burrow sites influences desert tortoise densities 8 Each desert tortoise uses about 5 to 25 burrows per year Some burrows are used repeatedly sometimes for several consecutive years Desert tortoises share burrows with various mammals reptiles birds and invertebrates such as white tailed antelope squirrels Ammospermophilus leucurus woodrats Neotoma collared peccaries Dicolytes tajacu burrowing owls Athene cunicularia Gambel s quail Callipepla gambelii rattlesnakes Crotalus spp Gila monsters Heloderma suspectum beetles spiders and scorpions One burrow can host up to 23 desert tortoises such sharing is more common for desert tortoises of opposite sexes than for desert tortoises of the same sex 8 Lifecycle editReproduction edit Tortoises mate in the spring and autumn Male desert tortoises grow two large white glands around the chin area called chin glands that signify mating season A male circles around female biting her shell in the process He then climbs upon the female and insert his penis a white organ usually only seen upon careful inspection during mating as it is hidden inside the male and can only be coaxed out with sexual implication into the cloaca of a female which is located around the tail The male may make grunting noises once atop a female and may move his front legs up and down in a constant motion as if playing a drum failed verification 19 nbsp Hatching baby desert tortoise Months later the female lays a clutch of four to eight hard shelled eggs 20 which have the size and shape of ping pong balls usually in June or July The eggs hatch in August or September Wild female tortoises produce up to three clutches a year depending on the climate Their eggs incubate from 90 to 135 days 4 some eggs may overwinter and hatch the following spring In a laboratory experiment temperature influenced hatching rates and hatchling sex Incubation temperatures from 27 to 31 C 81 to 88 F resulted in hatching rates exceeding 83 while incubation at 25 C 77 F resulted in a 53 hatching rate Incubation temperatures less than 31 C 88 F resulted in all male clutches Average incubation time decreased from 124 7 days at 25 C 77 F to 78 2 days at 31 C 88 F 21 The desert tortoise is one of the few known tortoises in existence that has been observed engaging in homosexual intercourse 22 Same sex intercourse happens in many species There is no one answer as to why this occurs One possible explanation for this could be the social component of gaining and establishing dominance 23 Maturation edit The desert tortoise grows slowly often taking 16 years or longer to reach about 20 cm 8 in in length The growth rate varies with age location gender and precipitation It can slow down from 12 mm year for ages 4 8 years to about 6 0 mm year for ages 16 to 20 years Males and females grow at similar rates females can grow slightly faster when young but males grow larger than females 8 Desert tortoises reach their reproductive maturity at ages 15 to 20 when they become longer than 18 cm 7 in However it is possible for them to mature faster as 10 year old females that are able to reproduce have been observed 8 Activity edit Their activity depends on location peaking in late spring for the Mojave Desert and in late summer to fall in Sonoran Desert some populations exhibit two activity peaks during one year Desert tortoises brumate during winters roughly from November to February April Females begin brumating later and emerge earlier than males juveniles emerge from brumation earlier than adults 8 24 Temperature strongly influences desert tortoise activity level Although desert tortoises can survive body temperatures from below freezing to over 40 C 104 F most activity occurs at temperatures from 26 to 34 C 79 to 93 F The influence of temperature is reflected in daily activity patterns with desert tortoises often active late in the morning during spring and fall early in the morning and late in the evening during the summer and occasionally becoming active during relatively warm winter afternoons The activity generally increases after rainfall 8 Although desert tortoises spend the majority of their time in shelter movements of up to 200 m 660 ft per day are common The common comparatively short distance movements presumably represent foraging activity traveling between burrows and possibly mate seeking or other social behaviors Long distance movements could potentially represent dispersal into new areas and or use of peripheral portions of the home range 8 Lifespan edit The lifespan of a desert tortoise can vary from 50 to 80 years 7 The main causes of mortality in desert tortoises include predators human related causes diseases and environmental factors such as drought flooding and fire 8 nbsp Desert tortoise with an estimated age of 63 years Red Rock Canyon National Conservation Area NV The annual death rate of adults is typically a few percent but is much higher for young desert tortoises Only 2 5 of hatchlings are estimated to reach maturity Estimates of survival from hatching to 1 year of age for Mojave Desert tortoises range from 47 to 51 Survival of Mojave Desert tortoises from 1 to 4 years of age is 71 89 8 Diet edit nbsp nbsp nbsp A young desert tortoise The desert tortoise is an herbivore Grasses form the bulk of its diet but it also eats herbs annual wildflowers and new growth of cacti as well as their fruit and flowers Rocks and soil are also ingested perhaps as a means of maintaining intestinal digestive bacteria as a source of supplementary calcium or other minerals As with birds stones may also function as gastroliths enabling more efficient digestion of plant material in the stomach 8 Much of the tortoise s water intake comes from moisture in the grasses and wildflowers they consume in the spring A large urinary bladder can store over 40 of the tortoise s body weight in water urea uric acid and nitrogenous wastes During very dry times they may give off waste as a white paste rather than a watery urine During periods of adequate rainfall they drink copiously from any pools they find and eliminate solid urates The tortoises can increase their body weight by up to 40 after copious drinking 25 Adult tortoises can survive a year or more without access to water 8 During the summer and dry seasons they rely on the water contained within cactus fruits and mesquite grass To maintain sufficient water they reabsorb water in their bladders and move to humid burrows in the morning to prevent water loss by evaporation 25 A desert tortoise can empty its bladder as one of its defense mechanisms 26 This can leave the tortoise in a very vulnerable condition in dry areas since the tortoise will no longer have a backup water supply If a tortoise is seen in the wild you should not handle or pick them up unless they are in imminent danger Handling of tortoises may have consequences for the animal such as the development of upper respiratory tract infections 26 Predation and conservation status edit Ravens Gila monsters kit foxes badgers roadrunners coyotes and fire ants are all natural predators of the desert tortoise They prey on eggs juveniles which are 50 75 mm 2 3 in long with a thin delicate shell or in some cases adults Ravens are thought to cause significant levels of juvenile tortoise predation in some areas of the Mojave Desert frequently near urbanized areas 27 The most significant threats to tortoises include urbanization disease habitat destruction and fragmentation illegal collection and vandalism by humans and habitat conversion from invasive plant species Brassica tournefortii Bromus rubens and Erodium spp Desert tortoise populations in some areas have declined by as much as 90 since the 1980s and the Mojave population is listed as threatened under the Endangered Species Act of 1973 in 1990 28 after being listed as endangered or threatened in the case of the Beaver Dam Slope Utah population under an emergency rule in 1989 29 All desert tortoises are protected under law of the United States based on similarity of appearance to tortoises of the protected Mojave population 30 It is unlawful to touch harm harass or collect wild desert tortoises It is however possible to adopt captive tortoises through the Tortoise Adoption Program in Arizona Utah Division of Wildlife Resources Desert Tortoise Adoption Program in Utah Joshua Tree Tortoise Rescue Project in California or through Bureau of Land Management in Nevada When adopted in Nevada they will have a computer chip embedded on their backs for reference According to Arizona Game and Fish Commission Rule R12 4 407 A 1 they may be possessed if the tortoises are obtained from a captive source which is properly documented Commission Order 43 Reptile Notes 3 one tortoise per family member The Fort Irwin National Training Center of the US Army expanded into an area that was habitat for about 2 000 desert tortoises and contained critical desert tortoise habitat a designation by the US Fish and Wildlife Service In March 2008 about 650 tortoises were moved by helicopter and vehicle up to 35 km away 31 The Desert Tortoise Preserve Committee protects roughly 2 000 hectares 5 000 acres of desert tortoise habitat from human activity This area includes 1 760 hectares 4 340 acres in Kern County 290 hectares 710 acres in San Bernardino County and 32 hectares 80 acres in Riverside County 32 Another potential threat to the desert tortoise s habitat is a series of proposed wind and solar farms 33 As a result of legislation solar energy companies have been making plans for huge projects in the desert regions of Arizona California Colorado New Mexico Nevada and Utah The requests submitted to the Bureau of Land Management total nearly 7 300 km2 1 800 000 acres 34 While tortoises are made to withstand tough conditions and high temperatures they are unable to cope with the dangers of human development such as the use of off roading vehicles These vehicles that come along at high speeds have the potential to crush and kill tortoises running over their eggs and burrows and significantly impacting their population 35 verification needed Human development editIvanpah solar power project edit Concerns about the impacts of the Ivanpah Solar thermal project led the developers to hire some 100 biologists and spend US 22 million caring for the tortoises on or near the site during construction 36 37 Despite this in a 2011 Revised Biological Assessment for the Ivanpah Solar Electric Generating System the Bureau of Land Management anticipated the loss or significant degradation of 1 420 hectares 3 520 acres of tortoise habitat and the harm of 57 274 adult tortoises 608 juveniles and 236 eggs inside the work area and 203 adult tortoises and 1 541 juvenile tortoises outside the work area The Bureau of Land Management BLM expects that most of the juvenile tortoises on the project will be killed 38 39 Lawsuits editIn the summer of 2010 Public Employees for Environmental Responsibility filed a lawsuit against the National Park Service for not having taken measures to manage tortoise shooting in the Mojave National Preserve of California Biologists discovered numerous gunshot wounds holes on dead tortoise shells which could likely have been caused long after natural death as these shells can take five years to disintegrate and make useful targets for well intentioned target shooters These shells left behind by nature droughts roadkill or vandals may have attracted ravens and threatened the healthy tortoises as any predator bird need only feed once on a small tortoise to remember it as a viable food source 40 The National Park Service did not take the measures they were urged to They responded with We simply do not believe that such regulations are warranted at this time and no further action has been taken 41 Diseases editReptiles are known to become infected by a wide range of pathogens which includes viruses bacteria fungi and parasites More specifically the G agassizii population has been negatively affected by upper respiratory tract disease cutaneous dyskeratosis herpes virus shell necrosis urolithiasis bladder stones and parasites 42 43 44 Upper respiratory tract disease edit Upper respiratory tract disease URTD is a chronic infectious disease responsible for population declines across the entire range of the desert tortoise It was identified in the early 1970s in captive desert tortoise populations and later identified in the wild population 42 URTD is caused by the infectious agents Mycoplasma agassizii and Mycoplasma testudineum which are bacteria in the class Mollicutes and characterized by having no cell wall and a small genome 45 46 47 Mycoplasmae appear to be highly virulent infectious in some populations while chronic or even dormant in others 48 The mechanism whether environmental or genetic responsible for this diversity is not understood Infection is characterized by both physiological and behavioral changes nasal and ocular discharge palpebral edema swelling of the upper and or lower palpebra or eyelid the fleshy portion that is in contact with the tortoises eye globe and conjunctivitis weight loss changes in color and elasticity of the integument and lethargic or erratic behavior 42 49 50 51 These pathogens are likely transmitted by contact with an infected individual Epidemiological studies of wild desert tortoises in the western Mojave Desert from 1992 to 1995 showed a 37 increase in M agassizii 47 Tests were conducted on blood samples and a positive test was determined by the presence of antibodies in the blood defined as being seropositive Cutaneous dyskeratosis edit Cutaneous dyskeratosis CD is a shell disease of unknown origin and has unknown implications on desert tortoise populations Observationally it is typified by shell lesions on the scutes Areas infected with CD appear discolored dry rough and flakey with peeling pitting and chipping through multiple cornified layers 52 Lesions are usually first located on the plastron underside of the tortoises although lesions on the carapace upper side and fore limbs are not uncommon In advanced cases exposed areas become infected with bacteria fungi and exposed tissue and bone may become necrotic 50 52 CD was evident as early as 1979 and was initially identified on the Chuckwalla Bench Area of Critical Environmental Concern in Riverside County California 53 Currently the means of transmission are unknown although hypotheses include autoimmune diseases exposure to toxic chemicals possibly from mines or air pollution or a deficiency disease possibly resulting from tortoises consuming low quality invasive plant species instead of high nutrient native plants 43 48 Impacts of disease edit Two case studies outlined the spread of disease in desert tortoises The Daggett Epidemiology of Upper Respiratory Tract Disease project which provides supporting disease research for the Fort Irwin translocation project lends an example of the spread of disease In 2008 197 health evaluations were conducted revealing 25 0 45 2 exposure to M agassizii and M testudineum respectively in a core area adjacent to Interstate 15 The spread of disease was tracked over two years and clinical signs of URTD spread from the core area to adjacent outlying locations during this time Overlaying home ranges and the social nature of these animals suggests that disease free individuals may be vulnerable to spread of disease and that transmission can occur rapidly 54 Thus wild tortoises that are close to the urban wildlife interface may be vulnerable to spread of disease as a direct result of human influence The second study indicated that captive tortoises can be a source of disease to wild Agassiz s desert tortoise populations Johnson et al 2006 tested blood samples for URTD n 179 and herpesvirus n 109 from captive tortoises found near Barstow CA and Hesperia CA Demographic and health data were collected from the tortoises as well from other reptiles housed in the same facility Of these 45 3 showed signs of mild disease 16 2 of moderate disease and 4 5 of severe disease and blood tests revealed that 82 7 of tortoises had antibodies to mycoplasma and 26 6 had antibodies to herpesvirus which means the tortoises were seropositive for these two diseases and indicate previous exposure to the causative agents With an estimated 200 000 captive desert tortoises in California their escape or release into the wild is a real threat to uninfected wild populations of tortoises Projections from this study suggest that about 4400 tortoises could escape from captivity in a given year and with an 82 exposure rate to URTD the wild population may be at greater risk than previously thought 55 Domestic pets editEdwards et al reported that 35 of desert tortoises in the Phoenix area are hybrids between either Gopherus agassizii and G morafkai or G morafkai and the Texas tortoise G berlandieri The intentional or accidental release of these tortoises could have dire consequences for wild tortoises 56 Before obtaining a desert tortoise as a pet it is best to check the laws and regulations of the local area and or state Desert tortoises may not be captured from the wild They may however be given as a gift from one private owner to another Desert tortoises need to be kept outdoors in a large area of dry soil and with access to vegetation and water An underground den and a balanced diet are crucial to the health of captive tortoises Management activities and spread of disease edit nbsp Tortoise Monitoring and Research at Joshua Tree National Park Research edit Wild populations of tortoises must be managed effectively to minimize the spread of diseases which includes research and education Despite significant research being conducted on desert tortoises and disease a considerable knowledge gap still exists in understanding how disease affects desert tortoise population dynamics It is not known if the population would still decline if disease were completely absent from the system are tortoises more susceptible to disease during drought conditions How does a non native diet impact a tortoise s ability to ward off pathogens What are the causes of immunity exhibited by some desert tortoises The 2008 USFWS draft recovery plan suggests that populations of tortoises that are uninfected or only recently infected should likely be considered research and management priorities Tortoises are known to show resistance to disease in some areas an effort to identify and maintain these individuals in the populations is essential Furthermore increasing research on the social behavior of these animals and garnering a greater understanding of how behavior facilitates disease transmission would be advantageous in understanding rates of transmission Finally translocation of tortoises should be done with extreme caution disease is typically furtive and moving individuals or populations of tortoises across a landscape can have unforeseen consequences 48 Education edit As a corollary to research education may help prevent captive tortoises from coming into contact with wild populations 55 Education campaigns through veterinarians government agencies schools museums and community centers throughout the range of the desert tortoise could limit the spread of tortoise diseases into wild populations Strategies may include encouraging people to not breed their captive tortoises ensure that different species of turtles and tortoises are not housed in the same facility which would help to prevent the spread of novel diseases into the desert tortoise population ensure captive tortoises are adequately housed to prevent them from escaping into the wild and to ensure that captive turtles and tortoises are never released into the wild Desert tortoises have been severely affected by disease Both upper respiratory tract disease and cutaneous dyskeratosis have caused precipitous population declines and die offs across the entire range of this charismatic species Both of these diseases are extremely likely to be caused by people and URTD is easily linked with people releasing captive tortoises into the wild The combination of scientific research and public education is imperative to curb the spread of disease and aid the tortoise in recovery State reptile editThe desert tortoise is the state reptile of California and Nevada nbsp Closeup of desert tortoise at Red Rock Canyon National Conservation Area 2020 nbsp Same desert tortoise at Red Rock Canyon NCA showing habitat 2020 nbsp Front view closeup of desert tortoise at Red Rock Canyon NCA 2020 nbsp Photo showing rocky habitat of Desert tortoise at Red Rock Canyon NCA 2020References edit nbsp This article incorporates public domain material from Gopherus agassizii United States Forest Service Berry K H Allison L J McLuckie A M Vaughn M Murphy R W 2021 Gopherus agassizii IUCN Red List of Threatened Species 2021 e T97246272A3150871 doi 10 2305 IUCN UK 2021 2 RLTS T97246272A3150871 en Retrieved February 19 2022 Appendices CITES Convention on International Trade in Endangered Species of Wild Fauna and Flora May 4 2023 Retrieved May 11 2023 Note Protected as a member of the Testudinidae Uwe Fritz Peter Havas 2007 Checklist of Chelonians of the World Vertebrate Zoology 57 2 280 doi 10 3897 vz 57 e30895 S2CID 87809001 a b c Jones Mike Gopherus agassizii Cooper 1863 sic California Desert Tortoise Encyclopedia of Life Beolens Bo Watkins Michael Grayson Michael 2011 The Eponym Dictionary of Reptiles Baltimore Johns Hopkins University Press xiii 296 pp ISBN 978 1 4214 0135 5 Gopherus agassizii p 2 Gale Product Login galeapps gale com Retrieved December 10 2022 a b Desert Tortoise Life History a b c d e f g h i j k l m n o Gopherus agassizii United States Forest Service fs fed us Archived February 4 2018 at the Wayback Machine Genetic Analysis Splits Desert Tortoise into Two Species Archived January 2 2017 at the Wayback Machine US Geological Survey 2011 06 28 Retrieved on 2019 08 22 Murphy Robert Berry Kristin Edwards Taylor Leviton Alan Lathrop Amy Riedle J Daren June 28 2011 The dazed and confused identity of Agassiz s land tortoise Gopherus agassizii Testudines Testudinidae with the description of a new species and its consequences for conservation ZooKeys 113 39 71 Bibcode 2011ZooK 113 39M doi 10 3897 zookeys 113 1353 ISSN 1313 2970 PMC 3187627 PMID 21976992 a b Edwards T Karl AE Vaughn M Rosen PC Torres CM Murphy RW 2016 The desert tortoise trichotomy Mexico hosts a third new sister species of tortoise in the Gopherus morafkai G agassizii group ZooKeys 562 131 158 Bibcode 2016ZooK 562 131E doi 10 3897 zookeys 562 6124 PMC 4768471 PMID 27006625 Wilson Don E Burnie David 2005 Animal The Definitive Visual Guide to the World s Wildlife New York City DK Dorling Kindersley Publishing 624 pp ISBN 978 0 7894 7764 4 Jirik Kate LibGuides Desert Tortoises Gopherus agassizii Fact Sheet Physical Characteristics ielc libguides com Retrieved December 10 2022 Desert Tortoise The Nature Conservancy Retrieved December 10 2022 DROUGHT Lack of water threatens desert tortoise March 21 2014 a b Murphy Robert Berry Kristin Edwards Taylor Leviton Alan Lathrop Amy Riedle J Daren 2011 The dazed and confused identity of Agassiz s land tortoise Gopherus agassizii Testudines Testudinidae with the description of a new species and its consequences for conservation ZooKeys 113 39 71 Bibcode 2011ZooK 113 39M doi 10 3897 zookeys 113 1353 PMC 3187627 PMID 21976992 Federal agencies partner to conserve Mojave desert tortoises VVNG Victor Valley News Group December 28 2021 Retrieved December 29 2021 Glass Godwin Lenela April 2002 Desert Survivor Ranger Rick p 16 Tortoise Adoption Program Care and Husbandry Desertmuseum org Retrieved on 2013 01 06 Desert Tortoise wildlife information DesertUSA Retrieved on 2013 01 06 Lewis Winokur Vanessa Winokur Robert M 1995 Incubation temperature affects sexual differentiation incubation time and posthatching survival in desert tortoises Gopherus agassizii Canadian Journal of Zoology 73 11 2091 2097 doi 10 1139 z95 246 Biol Exuberance Desert Tortoise Bagemihl 1999 AD pages 232 664 Rodrigues Joao Fabricio Mota Liu Yuxiang May 1 2016 An overview of same sex mounting in turtles and tortoises Journal of Ethology 34 2 133 137 doi 10 1007 s10164 015 0456 2 ISSN 1439 5444 S2CID 254145807 Deane K 2018 The hibernation process and post hibernation care of tortoises Veterinary Nursing Journal 33 7 197 200 doi 10 1080 17415349 2018 1466670 S2CID 59535431 a b Auffenberg Walter 1969 Tortoise Behavior and Survival Chicago Rand McNally OCLC 2583084 a b Desert Tortoise Gopherus agassizii Mojave National Preserve California National Park Service March 21 2022 Retrieved May 11 2023 Sahagun Louis June 10 2019 These tortoise killing ravens are so smart scientists must use drones to stop them Los Angeles Times Retrieved June 10 2019 Hohman Judy Stine Peter Bransfield Ray Kramer Karla U S Fish and Wildlife Service 1990 Endangered and Threatened Wildlife and Plants Determination of Threatened Status for the Mojave Population of the Desert Tortoise Federal Register 55 63 12178 12191 55 FR 12178 Campbell Jackie U S Fish and Wildlife Service 1989 Endangered and Threatened Wildlife and Plants Emergency Determination of Endangered Status for the Mojave Population of the Desert Tortoise Federal Register 54 149 32326 32331 54 FR 32326 Desert tortoise Gopherus agassizii Environmental Conservation Online System U S Fish amp Wildlife Service Retrieved April 28 2024 Sahagun Louis 2008 10 11 Army suspends relocation of Ft Irwin tortoises Los Angeles Times Connor Michael J and Mark Massar Megadump Initiative Threat to DTNA and 2005 Annual Report Desert Tortoise Preserve Committee Accomplishments amp Activities Tortoise Tracks April 2006 Simon Richard 2009 03 25 Feinstein wants desert swath off limits to solar wind projects Los Angeles Times Woody Todd 2009 07 13 A Solar Land Rush The New York Times Glass Godwin April 2002 DESERT SURVIVOR Science Reference Center Dini Jack 2010 10 31 Desert Tortoises Get Trumped by California s Solar Plants Hawaii Reporter Desert Tortoise Care at the Ivanpah Solar Project Archived 2012 06 09 at the Wayback Machine ivanpahsolar com 2012 03 06 Bureau of Land Management 2011 4 19 Revised Biological Assessment for the Ivanpah Solar Electric Generating System Ivanpah SEGS Project Archived 2013 10 21 at the Wayback Machine U S Department of the Interior Ertz Brian 2011 4 29 Ivanpah solar project would disturb thousands of desert tortoises The Wildlife News Stade Kristen 2010 07 28 Lawsuit to protect varmints in Mojave National Preserve Archived October 21 2013 at the Wayback Machine Peer Jarvis Mojave letter 2011 a b c Jacobson E R J M Gaskin M B Brown R K Harris C H Gardiner J L Lapointe H P Adams and C Reggiardo 1991 Chronic upper respiratory tract disease of free ranging desert tortoises Xerobates agassizii Journal of Wildlife Diseases 27 2 296 316 doi 10 7589 0090 3558 27 2 296 PMID 2067052 S2CID 42473017 a href Template Cite journal html title Template Cite journal cite journal a CS1 maint multiple names authors list link a b Jacobson E R T J Wronski J Schumacher C Reggiardo amp K H Berry 1994 Cutaneous dyskeratosis in free ranging desert tortoises Gopherus agassizii in the Colorado Desert of Southern California Journal of Zoo and Wildlife Medicine 25 1 68 81 JSTOR 20095336 Berry K H E K Spangenberg B L Homer and E R Jacobson 2002 Deaths of desert tortoises following periods of drought and research manipulation PDF Chelonian Conservation and Biology 4 436 448 a href Template Cite journal html title Template Cite journal cite journal a CS1 maint multiple names authors list link Brown M B I M Schumacher P A Klein K Harris T Correll and E R Jacobson 1994 Mycoplasma agassizii causes upper respiratory tract disease in the desert tortoise Infection and Immunity 62 10 4580 4586 doi 10 1128 iai 62 10 4580 4586 1994 PMC 303146 PMID 7927724 a href Template Cite journal html title Template Cite journal cite journal a CS1 maint multiple names authors list link Berry K H and J Van Abbema 1997 Demographic consequences of disease in two desert tortoise populations in California USA Proceedings conservation restoration and management of tortoises and turtles an international conference 11 16 July 1993 State University of New York Purchase New York USA 91 99 a b Brown M B K H Berry I M Schumacher K A Nagy M M Christopher and P A Klein 1999 Seroepidemiology of upper respiratory tract disease in the desert tortoise in the western Mojave Desert of California Journal of Wildlife Diseases 35 4 716 727 doi 10 7589 0090 3558 35 4 716 PMID 10574531 S2CID 22509874 a href Template Cite journal html title Template Cite journal cite journal a CS1 maint multiple names authors list link a b c Draft revised recovery plan for the Mojave population of the desert tortoise Gopherus agassizii U S Fish and Wildlife Service California and Nevada Region Sacramento California 2008 Schumacher I M M B Brown E R Jacobson B R Collins amp P A Klein 1993 Detection of antibodies to a pathogenic mycoplasma in desert tortoises Gopherus agassizii with upper respiratory tract disease Journal of Clinical Microbiology 31 6 1454 1460 doi 10 1128 jcm 31 6 1454 1460 1993 PMC 265561 PMID 8314986 a b Homer B L K H Berry M B Brown amp G Ellis E R Jacobson 1998 Pathology of diseases in wild desert tortoises from California Journal of Wildlife Diseases 34 3 508 523 doi 10 7589 0090 3558 34 3 508 PMID 9706560 S2CID 2657867 Berry K H M M Christopher 2001 Guidelines for the field evaluation of desert tortoise health and disease Journal of Wildlife Diseases 37 3 427 450 doi 10 7589 0090 3558 37 3 427 PMID 11504217 S2CID 6952651 a b Homer B L C Li K H Berry N D Denslow E R Jacobson R H Sawyer amp J E Williams 2001 Soluble scute proteins of healthy and ill desert tortoises Gopherus agassizii American Journal of Veterinary Research 62 1 104 110 doi 10 2460 ajvr 2001 62 104 PMID 11197546 Jacobson E R 1994 Causes of mortality and diseases in tortoises A review Journal of Zoo and Wildlife Medicine 25 1 2 17 JSTOR 20095329 Mack J and K H Berry 2009 Development of an epidemiological model of upper respiratory tract disease Mysoplasmosis in desert tortoises using the Daggett study area Year 2 2008 Proceedings of the thirty fourth annual meeting and symposium The desert tortoise council a b Johnson A J D J Morafka amp E R Jacobson 2006 Seroprevalence of Mycoplasma agassizii and tortoise herpesvirus in captive desert tortoises Gopherus agassizii from the Greater Barstow Area Mojave Desert California PDF Journal of Arid Environments 67 192 201 Bibcode 2006JArEn 67 192J doi 10 1016 j jaridenv 2006 09 025 Archived from the original PDF on May 16 2013 Retrieved January 6 2013 Edwards T C J Jarchow C A Jones and K E Bonine 2010 Tracing Genetic Lineages of Captive Desert Tortoises in Arizona Journal of Wildlife Management 74 4 801 807 Bibcode 2010JWMan 74 801E doi 10 2193 2009 199 S2CID 86409153 a href Template Cite journal html title Template Cite journal cite journal a CS1 maint multiple names authors list link External links edit nbsp Wikimedia Commons has media related to Gopherus agassizii Gopherus agassizii Integrated Taxonomic Information System Retrieved February 6 2006 The Desert Tortoise The Arizona Sonora Desert Museum Desert Tortoise National Park Service Desert Tortoise data and information portal Mojave Desert Ecosystem Program Desert Tortoise documentary video The Desert Tortoise A Delicate Balance NASA Dryden Desert Tortoise CouncilFurther reading editBehler JL King FW 1979 The Audubon Society Field Guide to North American Reptiles and Amphibians New York Alfred A Knopf 743 pp ISBN 0 394 50824 6 Gopherus agassizii pp 471 472 Plate 328 Boulenger GA 1889 Catalogue of the Chelonians Rhynchocephalians and Crocodiles in the British Museum Natural History New Edition London Trustees of the British Museum Natural History Taylor and Francis printers x 311p Plates I III Testudo agasizii p 156 Cooper JG 1861 New California Animals Proc California Acad Sci 2 118 123 Xerobates agassizii new species pp 120 121 Goin CJ Goin OB Zug GR 1978 Introduction to Herpetology Third Edition San Francisco W H Freeman xi 378 pp ISBN 0 7167 0020 4 Gopherus agassizi p 155 Smith HM Brodie ED Jr 1982 Reptiles of North America A Guide to Field Identification New York Golden Press 240 pp ISBN 0 307 13666 3 paperback ISBN 0 307 47009 1 hardcover Gopherus agassizi pp 62 63 Stebbins RC 2003 A Field Guide to Western Reptiles and Amphibians Third Edition The Peterson Field Guide Series Boston and New York Houghton Mifflin xiii 533 pp ISBN 978 0 395 98272 3 Gopherus agassizii pp 255 257 Plate 22 Map 63 Stejneger L Barbour T 1917 A Check List of North American Amphibians and Reptiles Cambridge Massachusetts Harvard University Press 125 pp Gopherus agassizii p 121 Retrieved from https en wikipedia org w index php title Desert tortoise amp oldid 1221234110, wikipedia, wiki, book, books, library,

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