A Pacific Pocket Mouse at the San Diego Zoo Safari Park enjoyed a late-night snack in the zoo's off-exhibit breeding facilities. The mouse is part of the first-ever breeding program of the critically endangered species. The program has yielded five litters of pups since June. Pacific Pocket Mice are nocturnal animals. True to the name, these mice are pocket sized—they weigh less than 9 grams. Aside from the occasional lettuce, they eat seeds and have been known to eat insects. Interestingly, these rodents don't drink water. Instead, they are hydrated from the vegetation they eat. The breeding program is managed by the San Diego Zoo Institute for Conservation Research in cooperation with the U.S. Fish and Wildlife services. Scientists are working to increase the overall population and to maintain genetic diversity within the native-Californian species.