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Desert Tortoises (Gopherus agassizii) Fact Sheet: Physical Characteristics

Desert Tortoise (Gopherus agassizii)

Physical Characteristics

Body measurements

Attribute Measurement
Weight 3.6-6.8 kg (8-15 lb)
Length 250-300 mm average; 400 mm maximum
(9.8-11.8 in; 15.7 in)

 

Sources: Bonin et al. (2006) [length]

General Appearance

  • Largest terrestrial turtle in the United States.
  • High-domed shell allows large space for lungs and efficient thermoregulation.
  • Front limbs shovel-like.
  • Prominent growth lines on scutes (also called scales or shields)
  • Carapace (top) brown or gray without a pattern, but often may be brown or orange in the center, especially in young.
  • Plastron (underside) yellowish or brownish and is not hinged.
  • Like most turtles, on the shell have 5 vertebral scutes, 4 pairs of costal (rib) scutes, 22 scutes around the margins and a single nuchal scute.
  • Like all turtles, good hearing, but no external ear; no teeth (have beak)

Sexual Dimorphism

  • Adults sexually dimorphic with males larger than females
  • Males have concave plastron (bottom shell), longer tail, and enlarged glands under chin
    • Glands possibly exude protein-like substance during breeding season
  • Female's plastron is flat, slightly expanded towards rear

Other Physical and Physiological Characteristics

  • Limbs stocky, elephantine
    • Forelimbs somewhat flattened, hindlimbs columnar
    • The turtles in this family (Testudinidae) have no connecting web of skin between digits
  • Large cone-shaped scales on limbs
  • Light eye ring
  • Iris of eye usually greenish yellow
  • Head relatively narrow; ridges on upper jaw meeting at a sharp angle
  • Forelimbs cover opening when drawn in
  • Forelimbs have five digits; hindlimbs, four
    • Claws on front limbs for digging burrows
    • Females use claws for digging nest
    • A spur present on the hind limb.
  • Gular area (part of plastron lying beneath the extended head) slightly forked (Bonin et al 2006)
  • A single scute underneath the armpits (axillary scute). (Ernst & Lovich 2009)

Hiding in the Desert

Desert Tortoise

A desert tortoise's coloration helps camoflauge it among rocks and sand.

Image credit: © San Diego Zoo Wildlife Alliance. All rights reserved.

Page Citations

Auffenberg (1974)
Bonin et al. (2006)
Ernst & Lovich (2009)
Stebbins (2003)

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