Desert tortoiseGopherus agassizii

Order TestudinesFamily TestudinidaeGenus GopherusSpecies agassizii

Geographic Range Mojave and Sonoran deserts of southwestern US and northwestern Mexico

Habitat Desert regions, canyon bottoms, rocky hillsides

Niche Terrestrial, diurnal, herbivorous, nomadic

Wild Diet Herbs, grasses, flowers, fruits, cacti. Most of the moisture they require comes from the food that they eat.

Life Span High mortality rate among young. If they survive to the age of 20, they typically live between 50 – 80 years.

Appearance Dull brown to dull yellow in color. Shell is 6 – 14 inches in length and weight is between 8 – 15 pounds. Males are generally larger than females.

Adaptations Long spade-like nails for digging in sand. Males also have a gular shield – a bony plate on their plastron – which aids in flipping rivals when competing for mates.

Fun Facts The desert tortoise is the official reptile of the state of California. Males will fight for breeding rights, which includes ramming, chasing and trying to flip opponents. Breeding takes place from spring to fall, and females can store sperm for up to 18 months, generally laying eggs after winter hibernation. An average size clutch is 3-5 eggs, laid in a nest scooped from the desert sand. Incubation lasts between 90 – 135 days and temperature plays a role both in the length of incubation and the sex of the hatchlings.

To see color photos of this animal, go to www.sfzoo.org/wildaboutartandscience

At the Zoo “Cactus”, “Mojave” & “Helga Feinstein” all live at the Koret Animal Resource Center.

Comparison Tortoises and turtles both belong to the same order which evolved over 200 million years ago while dinosaurs walked the earth. Turtles are aquatic or semi-aquatic with streamlined shells and are mostly omnivorous. Tortoises live on land and have domed shells which they can retreat inside and are herbivorous.

Status and Conservation Vulnerable

Threats Habitat destruction and fragmentation, road mortality, and the pet trade. This includes both the collection and release of former pets; many of which had caught a respiratory illness in captivity and passed it on to wild populations.

Bibliography Nature Trail Handbook, Animal Diversity Web

Carapace

Plastron

Scute

Gular shield

Desert Tortoise – Can You Dig It?Meets Kindergarten California Science Content Standards – 2c, 3a and 4e (see Standards Key)California Visual Art Standard 2.6 - Use geometric shapes/forms (circle, triangle, square) in a work of art.Taking It Further - California Visual Art Standard 2.3 - Make a collage with cut or torn papershapes/forms.

Animal to Draw for Art Contest – turtle or tortoise

Writing prompt for the sentence of the back of the student’s drawing – What is your tortoisedoing in your drawing? Why do tortoises have a shell?

Objective – To better understand the different body parts of the desert tortoise

Time - 15 min.

Background – The desert tortoise is California’s state reptile, living in the southeastern portionof the state, in the Mojave Desert. They use their extremely long nails to dig burrows in orderto avoid the heat of the day or to hibernate. When battling over territory, males use their gularshields to try and flip another male over on to its back, which can be fatal. If desert tortoisesfind water, they will drink some, but most of the water they need comes from the plants theyeat.

Vocabulary -Carapace – the part of the shell that covers the tortoise’s backPlastron – the part of the shell that covers the tortoise’s bellyScute (sk-oot) – the outer layer of horny shields that cover the shell, these are made of keratin,the same material found in our fingernails.Gular (goo-lar) shield– the part of the plastron that sticks out under the chin of male deserttortoises

Materials – Images of desert tortoises (included), images of the Mojave Desert, and desert plants(easily found online)

Directions – Discuss with the students the different characteristics of deserts. The typicalresponse may be that deserts are hot, but explain that the temperature changes a lot from theday into the night. Would it be easy to deal with very hot days and very cold night? All desertsare very dry, with less than 10 inches of rain for the whole year. Ask: What types of plantsgrow there? (Cactus, grasses, some flowers after a rain, trees and even some fruit.) What kindsof animals live in the desert? (Rattlesnakes, sidewinder, desert iguana, coyote, tarantula) Usethe included image of a desert tortoise to engage the students in a discussion of the differentbody parts and what they are used for. You could also use images of the Mojave Desert andplants found there to give the students an idea of what the habitat looks like.

Questions for discussion – What do desert tortoises use their claws for? (digging) Where do youthink a desert tortoise goes when the weather is too hot or too cold? (underground) How wouldthe tortoise’s shell help to camouflage it? (it looks like a rock) What does a tortoise use its shellfor? (protection, shelter) Can it ever leave its shell? (No, its spine and ribs are part of the shell)Do you think it is easy for an animal to survive in the desert? (No, extreme temperatures, littlewater, plants are sparse) What plants does a desert tortoise eat? (cactus, grasses)

Website/books/other resources –Owen and Mzee: The True Tale of a Remarkable Friendship by Isabella Hatkoff, Craig Hatkoff,Paula Kahumbu and Peter GresteThe Tortoise and the Hare by Aesophttp://geochange.er.usgs.gov/sw/impacts/biology/tortoise1/http://www.californiaherps.com/turtles/pages/g.agassizii.html

Desert tortoise virtual field trip http://www.tortoise-tracks.org/dtna/tour.htmlDesert tortoise life cycle http://www.tortoise-tracks.org/gopherus/lifecycle.html

Taking it Further – Use classroom chalk to mark the length of a desert tortoise burrow on theplayground or sidewalk, their hibernation burrows reach 30 ft. long!

Conservation Action - Making choices that help our wild places and wild things is important.Saving water is one of those choices. Turn off the water while brushing your teeth, take shortershowers and keep some water in the refrigerator so you don’t need to run the tap to get coldwater.