By NORA BODRIAN
Why are some animals nocturnal? It is an evolutionary phenomenon where prey animals come out at night when their predators might not find them. Consequently, the predators have adapted hunting skills, and some might have enhanced their sight, speed, or senses of heat and smell. As bats produce sounds to locate prey through echolocation, tarantulas have specialized hairs with sensory receptors to “see” in the dark.
Animals that are primarily out at night at Mission Trails Regional Park include bats, owls, woodrats, mice, skunks, opossums, raccoons, and grey foxes, as well as scorpions and tarantulas. Some animals are crepuscular, active at dawn and dusk; these animals include bobcats, coyotes, mountain lions, and cottontail rabbits.
According to author, regional bat expert, and MTRP Trail Guide Don Endicott, there are 10 species of bats at Mission Trails Regional Park, and 22 species in San Diego County. The most common ones residing in the park are Canyon bats, Yuma myotis, Big brown bats, Mexican free-tailed bats, and Pocketed free-tailed bats. Living in diverse habitats throughout most of the world, bats are impressive mammals that can be nectar eaters (nectavores), fruit eaters (fructivores), or insect eaters. Nectavorous bats are responsible for pollinating many types of plants and “fruit bats” disperse seeds, greatly assisting reforestation in tropical regions. However, most of the over 1,300 species of bats, and all 10 species present in MTRP are insectivores. During their nightly forays, they consume moths, gnats, mosquitos, and other flying insects as well as those on the ground including grasshoppers, centipedes, and scorpions. One species that lives just north of San Diego County, the little brown bat, has been documented eating 1,000 mosquitos in a single hour — that’s a lot of mosquitos!
Mexican free-tailed bats are generalists who typically feed on moths, consuming hundreds of tons of invasive and crop-damaging species throughout the Southwestern U.S.
Bats are not blind but they primarily use echolocation to navigate and hunt during the night by emitting a call that echoes back to inform them where they are and the location and size of prey.
Our bats in Mission Trails will not fly into your hair, nor drink your blood. Like other wild animals, though, bats can contract rabies. Although the incidence of rabies in our local bats is extremely low, for your safety it is important to not handle any injured or sick bat you might encounter on the ground. Please contact one of Mission Trails’ rangers if you discover one.
At night, one might catch a glimpse of such silent flying predators as barn owls or great-horned owls. Owls can take down large raptors as well as small rodents, frogs, and lizards. They can swallow small prey whole, then spit up pellets of undigested feathers, skin, and bones. By dissecting pellets, one can see what kinds of animals live in an area.
The owl’s razor-sharp talons are for piercing and cutting; they would not sit on your shoulder like Harry Potter’s “Hedwig.” Owls’ large eyes don’t move in their sockets, but the whole head can swivel 180 degrees. It is very difficult to see an owl as they sit very still and their feathers are patterned like tree bark and leaves. One might see them flying over Mission Trails’ grasslands.
Tarantulas are the largest of all spiders, with distinctive hairy legs and bodies. The hair, or setae, is their primary sensory organ to smell and hear. The urticating hairs on the abdomen are defense mechanisms, which they flick out at attackers. Tarantulas do not spin webs, but live in burrows or under rocks, which they line with their spun silk. Tarantulas primarily eat insects, and their predators include mammals, birds, reptiles, and the infamous tarantula hawk wasp.
Bats, owls, and spiders make important environmental contributions beyond our imaginations. After the MTRP Visitor Center reopens, make sure to go out onto the terrace to see the interpretive panel about bats at MTRP, and the bat boxes installed on the Visitors Center’s roof.
— Nora Bodrian is a trail guide at Mission Trails Regional Parkk.