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The Desert Tortoise

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					The Desert Tortoise

                   Who Couldn’t Love a
                    Face Like This?
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
Physical Characteristics
   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
   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

                     Desert Tortoises have no
                      real defined mating
                      season, but most mating
                      occurs in April
   Between mid-May and early July,
    females scoop out nests in soft soil,
    often at or near their burrow’s
   Depending on her size, the female
    lays between 3-14 hard-shelled
   Eggs are about the size and shape
    of ping-pong balls
   Young tortoises hatch
    between mid-August and
   They will reach sexual
    maturity between15-20
    years of age.
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
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
   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
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.
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-
                        Other surveys showed free-ranging desert
                         tortoises with URTD were widespread
                         across the western U.S.
Treatment of the Disease
   Antibiotic therapy with enroflaxin at 5mg/kg
    body weight every other day for 10
   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
    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
    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
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
   “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

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