Squirrels are a small mammalian species native to Earth on several continents. Squirrels are herbivorous-eaters having a basic diet of nuts, small plants and some seeds. They also live in trees in order to hide from predators and to raise young. They also have been noted to live on Reach until its destruction by the Covenant.
The young Spartan-IIs survived several days on squirrels during one of their war game sessions with Tango Company, where they had to capture a flag.
Janissary James, musing about food in which milk that came from an unspecified source is used, suggested that the milk could come from squirrels.