The Desert Tortoise

1
The Desert Tortoise

• Who Couldnt 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
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

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 tortoises 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
  burrows 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 1970s, 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 tortoises 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 1970s, 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
  dont let captive tortoises out into the wild

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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

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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
  visitors 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

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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