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THE DESERT TORTOISE Gopherus agassazii. By Karen Bernstein. Introduction. State reptile of Nevada & California The largest reptile in Mojave Desert K-selected species Endangered species Conflicting data about if & why endangered. Characteristics. Shell is yellow-brownish to dark brown

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The desert tortoise gopherus agassazii l.jpg

THE DESERTTORTOISEGopherus agassazii

By Karen Bernstein


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Introduction

  • State reptile of Nevada & California

  • The largest reptile in Mojave Desert

  • K-selected species

  • Endangered species

  • Conflicting data about if & why endangered


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Characteristics

  • Shell is yellow-brownish to dark brown

  • Shell averages 15-37 cm in length

  • Avg weight: male=20 kg, female=13 kg


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Habitat

  • Found in NV, CA, UT, AZ & Mexico

  • Bajadas, alluvial fans, flats, & rocky terrain near scrub communities

  • Soil is determinant factor

  • Usually found between 1000-3000 feet


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Eating Habits

  • Herbivores

  • Diet largely depends on food availability

  • In spring, consume winter annuals

  • In summer, consume annual grasses (galleta grass)


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Reproduction

  • Mating period: March-June, Aug-Sept

  • Clutch size varies from 2-14 eggs

  • Incubation period highly variable


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  • Hatchling success commonly < 60%

  • Reach sexual maturity between 14-20 years of age

  • Lifespan estimated 60-100 years


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Estivation & Hibernation

  • Dig underground burrows

  • Summer burrows generally shorter than winter burrows


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Physiological Ecology & Adaptations

  • Do not maintain a daily internal homeostasis

  • Can tolerate large imbalances of water, energy, & salt

  • Mobile limbs & claws to dig burrows

  • Dig depressions in soil to catch rain


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Biogeography

  • 3 main populations: Sonoran Desert, Western Mojave Desert, & Eastern Mojave Desert


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Population Trends

  • Tortoise population has dropped 90% in the last 50 years

  • US Fish & Wildlife has challenged these estimates

  • no concrete evidence to support the idea of a major reduction throughout their range


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Endangered Species

  • First listed as threatened in 1990

  • Need a permit to kill or collect them


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Environmental Stresses

  • Urbanization: habitat loss, vandalism, construction of roads

  • Off-Road Vehicles (ORVs)

  • Upper Respiratory Tract Disease (URTD)

  • Raven Predation

  • Grazing

  • Habitat Fragmentation


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  • Source: http://www.cnn.com/EARTH/9704/23/tortoise/ Researchers voice hope for desert tortoiseFrom Correspondent Jim Hill


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Solutions

  • Relocation Potential

  • Habitat Conservation Planning (HCPs)

  • Desert Tortoise National Area (DTNA)


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Desert Tortoise in the Rain

His shell glistens with the moisture

of a early winter rain.

Small drops have drawn him

from his earth-dug bed

beneath porch steps-

all that remains of a house

washed away by fire.

The backyard fence,

which once kept him

from the sight ocean

or winding canyon,

has also been returned to ash.

The chirr of a wren

can now be heard

from camelia branches

which survived, somehow,

the red flow of flame

to hold new blossoms,

fluttering purple and red

as perfect as Chinese silk.

The tortoise, his head like a lump of lava,

takes one club foot step after another,

bumps his way across heaved red bricks.

He opens his mouth

to let his almost human tongue

loll out to lap up drops

of moisture dark as his eyes.


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The End

Thanks to Tom Stein!


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