Over 300 species of mammals, birds, reptiles and amphibians are found in the Arboretum. Abundant but often unseen insects, spiders and scorpions are also part of the Arboretum's natural ecosystem. Seeking shelter during the heat of the day, many of the Arboretum's free-roaming inhabitants are not always evident. Snakes, tortoises and toads usually venture forth at dawn or dusk. Lizards, such as the desert spiny lizard may be seen basking in the sun during the day.
Birds are most conspicuous during the early morning hours.
Diligent bird watchers may spot over 200 migratory, wintering and resident avian species. Evidence of night-roaming javelina , deer, coyote, bobcat, raccoons and ringtails can be seen as tracks or droppings. Pack rats abound along with day-time active cliff chipmunks, ground and rock squirrels. Animals are important to the desert plant community. Many desert plants rely on insects, birds, bats, rodents and other animals to pollinate their flowers and to disperse their seeds.