two color phases of the western terrestrial garter snake ("thamnophis elegans"), one with a red background the other with a green background, are present on brooks island. they're believed to prey on the northern alligator lizard ("elgaria coerulea") which lives around the island's ponds, as well as tree frogs and the ponds' population of introduced mosquitofish ("gambusia affinis"). on one occasion a western pond turtle ("actinemys marmorata") was recorded.