The desert tortoise is an endangered species in California, so you are not supposed to take them as pets, but if they wonder onto your property or dig under the fence to find shade and food, or make a home burrowing under the yard, you aren 't allowed to move them, unless you call in a special wildlife biologist to assist. It's quite a tricky endeavor. However, sometimes you can make them feel more at home and they make nice pets. Still, you might not wish to get too attached, eventually they decide to leave, and often don't return for a while, sometimes never.
There is quite a bit of difference between the males and females, and you can easily tell the difference. Males have an indentation underneath to which matches the shape of the shell of the females for mating, since the male mounts the female in this process. That's the easiest way to tell. If you see a desert tortoise, you might see a small sensor epoxied to the shell, don't worry it's a wildlife tracking device to help biologists learn more and protect the species habitat.
Wildlife field biologists remind us to always check under our car tires and cars if we are in their domain because they often seek shelter from the hot summer sun in the shade underneath. If you see a desert tortoise do not pick it up and move very slowly as not to upset it. If you do scare it or pick it up it might discharge its bladder where it stores water, this is very bad. If that happens it might be better of you lay it in some water to let it soak back into its system. And if you pick one up because it is on the road way, always put it back down facing the same direction, otherwise it becomes disoriented as to its direction of travel.
How would you like to learn more about having a tortoise as a pet? If so, let me recommend a very good book for you, it is available in digital or paper versions, the name of the book is:
"Sulcata and Leopard Tortoises – Complete Herp Care," by EJ Pirog, TFH Publishing, Neptune City, NJ, 2008, 128 pages, (Digital eBook Version) ASIN: B005KKODD4, ISBN: 978-0-7238-2898-2.
In this work you can learn about many of the African Tortoise species and the size of the egg laying "clutches" and how many eggs they lay along with their habit needs, mating season, incubation time for the eggs, and what type of predators try to get those eggs. Knowing what they eat is very important too. Most arid region tortoises are similar in nature, and be sure not to call them turtles, they are different you see. Please consider all this and think on it