The Desert Tortoise

1. The Desert Tortoise • Who Couldn’t Love a Face Like This?

2. Getting to know him… • Otherwise known as Gopherus agassizzii • State status (CA): threatened (1989) • Federal Status: threatened (1990) • Threatened species are those that are likely to become endangered if acts are not taken to protect them • The desert tortoise was named the state reptile of California in 1972 • Only about 2-3 tortoises per 100 hatched live to become adults

3. Adult tortoises have a carapace length of about 8-14 inches Carapace color varies from light yellow-brown to dark grey-brown They have small heads that are rounded in the front Front limbs are flattened and heavily scaled for digging. Males are generally larger than females and have a larger chin and longer tail Their large hind feet distinguish the desert tortoise from other tortoises Physical Characteristics

4. Habitat • Desert tortoises inhabit river washes, rocky hillsides, and flat desert areas having sandy or gravelly soil • The tortoise will excavate a burrow under bushes, overhanging soil or rock formations, or dig into open soil • The creosote bush, which is native to most of the desert tortoise’s habitat, is often the preferred site for digging a burrow • Tortoises drink water where it collects in pools near rocks or in depressions • Tortoises eat a variety of wildflowers, including mojave asters, desert dandelions, and and various annual and perennial grasses

5. Reproduction!!!!!!! • Desert Tortoises have no real defined mating season, but most mating occurs in April

6. Between mid-May and early July, females scoop out nests in soft soil, often at or near their burrow’s entrance • Depending on her size, the female lays between 3-14 hard-shelled eggs • Eggs are about the size and shape of ping-pong balls

7. Young tortoises hatch between mid-August and October • They will reach sexual maturity between15-20 years of age.

8. Threats to the Desert Tortoise • Raven predation has caused serious reductions in the number of young tortoises surviving to adulthood • U.S. Fish and Wildlife Services bird surveys found a 500% increase in the raven population in the Mojave between 1968-1988 • Humans • Upper Respiratory Tract Disease

9. Human Influences • The tortoises are jeapordized by habitat transformation, degradation, and fragmentation caused by highways, utility rights-of-way, off-road vehicle use, human development, and grazing • In the 1970’s, the use of off road vehicles in desert areas became a major threat to the tortoise • In California, hundreds of thousands of dune-buggies, four-wheel-drive vehicles, and motorcycles traverse unpaved desert landscape each year • Some studies say that these areas had only one-half to one-third as many tortoises as in closed areas • Heavy traffic, besides causing fatal collisions, can collapse the tortoise’s burrows and destroy the vegetation in the area • Human expanding has brought in ravens, which were previously uncommon to the desert and have become a major predator of young tortoises. • Ravens are sustained by the human garbage dumps

10. Upper Respiratory Tract Disease (URTD) • Signs include a nasal discharge, puffy eyelids, eyes recessed into the orbits, and dullness to the skin • Until further evidence proves otherwise, it appears that all species of tortoise are susceptible • The disease is caused by a bacteria-like organism called mycoplasma • Once infected, the tortoise will carry the disease for life • Likely predisposing factors include poor nutrition due to habitat degradation, drought, and release of infected, captive desert tortoises into the wild.

11. History of the Disease • In the 1970’s, desert tortoises with signs of the disease were observed on the Beaver Dam Slope of Utah. • In 1988, desert tortoises at the Desert Tortoise Natural Area (CA) were seen with clinical signs of the illness • Surveys of the DTNA in 1989 and 1990 showed that many tortoises were ill with the disease, and several shells indicated that the population was dying • Some studies showed that more than 70% of all adult tortoises died between 1988-1992 • Other surveys showed free-ranging desert tortoises with URTD were widespread across the western U.S.

12. Treatment of the Disease • Antibiotic therapy with enroflaxin at 5mg/kg body weight every other day for 10 treatments • In addition, diluted enroflaxin is flushed in the nostrils of the tortoise for 1 month • Since enroflaxin is highly irritating to the mucous membranes surrounding the eyes, it is important to avoid contact • Tortoises may remain carriers of mycoplasma for life with recurrences of the disease, even after treatment • Much easier to treat captive rather than free-range tortoises • Best plan is to prevent spreading the disease: don’t let captive tortoises out into the wild

13. Desert Tortoise Recovery Plan • 6 recovery units, establish 14 reserves or Desert Wildlife Management Areas • Each DWMA cover 415-3367 sq. km • U.S. Fish and Wildlife Service followed up the plan by designating 26,087 sq. km as federally protected “Critical Habitat” in 1994 • Additional habitat protected within the Joshua Tree National Park (2574 sq. km) and Desert Tortoise National Research Area (100 sq. km) • Recovery Plan recommends the prohibition of several activities in the reserves, but said that limited human activities should be allowed • Within each DWMA, the team recommends that less than 10% of the habitat be deignated as “experimental management areas” where intrusive and experimental research can occur

14. Prohibited Activities • All vehicle activity off of designated roads • Habitat destructive military maneuvers, clearing for agriculture, landfills, and other disturbances that diminish the capacity of the land • Domestic livestock grazing and grazing by feral burros and horses • Vegetation harvest, except by permit • Collection of biological/geological specimens, except by permit • Dumping and littering • Deposition of captive of displaced desert tortoises or other animals • Uncontrolled dogs out of vehicles • Discharge of firearms, except for hunting big game or upland game birds from September through February

15. Allowed Activities • Non-intrusive monitoring of desert tortoise population dynamics and habitat • Limited speed travel on designate, signed roads and maintenance of the roads • Non-consumptive recreation (hiking, bird-watching, photography, etc.) • Parking and camping in designated areas • Permitted or otherwise controlled maintenance of existing utilities • Surface disturbances that will enhance the quality of habitat for wildlife (construction of visitor’s centers in appropriate places, camping facilities, etc.) • Selective mining, to be determined on a case by case basis • Non-manipulative, non-intrusive biological/geological research, by permit

16. Sources • www.tortoise-tracks.org • www.nwf.org • www.dfg.ca.gov • www.werc.usgs.org • www.tortoise.org • www.cdpr.ca.gov • “Desert Tortoise and Upper Respiratory Tract Disease” Elliot Jacobson, D.V.M., Ph. D. University of Florida, Gainsville rev. August 1992 • “The Desert Recovery Plan: An Ambitious Effort to Conserve Biodiversity in the Mojave and Colorado Deserts of the United States Kristin H. Berry U.S. Department of the Interior, Bureau of Land Management Current Agency: U.S. Geological Survey, Biological Resources Division