The Pallid Bat (Antrozous pallidus)
by Margaret Gaspari
Many people have heard about the bat that eats scorpions. But the whole story about this creature is even more fascinating than that! The Pallid Bat is one of our most distinctive Washington bats. Large (about 4"), pale cream and white, and sporting huge ears that are wide as well as long, this is an easy bat to identify, even on the wing at night.
The Pallid Bat has a unique hunting strategy. Flying in a slow, dipping flight only three or four feet off the ground, it locates its prey by listening for sounds the prey is making. It eats large insects and invertebrates such as crickets, grasshoppers, mantids, cicadas, centipedes, June bugs, ground beetles, and the legendary scorpion, apparently unharmed by the stings. This incredible hunter has even been reported taking small lizards, and once, a Desert Pocket Mouse! Does this mean that Pallids have lost their ability to echolocate and hunt on the wing? Not at all. Occasionally they will do aerial hunting, complete with a feeding buzz. But they are well adapted to hunting terrestrial prey. They are capable of hovering flight. They are agile on the ground, and their broad wings easily get them airborne again. Their large ears help pick up the sounds of scuffling food items. And there is certainly no hunting competition from other species of bats. Of course, this niche is not without its risks. This is the one bat that is sometimes caught in mousetraps!
Although colonies are small by some standards (12 to 100 individuals), they are close knit and may include males. Babies, born in late June to early July, are slow (by bat standards) to mature. Their eyes and ears don't open until they are 8 to 10 days old, and they don't fly well until they are six weeks old. While most of the females are out foraging, some adults stay with the infants in a sort of baby-sitting behavior.
Pallids are very social bats. Experiments have shown that they learn new tasks most quickly by observing a conspecific performing the behavior. These bats also use a number of vocalizations in social communication. One bell-like "directive" call is used to coordinate the movements of the colony members and orient them on the chosen roost. An infant variation of this call allows the mother to identify and locate her baby, or babies (this species usually has twins). Since these calls can be heard by humans, they have been useful in locating Pallid roosts.
Pallid Bats are found in arid, low elevation, rocky habitats and they have both physical and behavioral adaptations to desert living. They are able to concentrate their urine to conserve water. Thus they are able to go long periods without drinking, getting necessary moisture from their food. Because they cannot tolerate temperatures over 100-104 F, they will search out day roosts in deep rock crevices where they can regulate their temperature by crawling deeper into the rock where it is cooler. They emerge to hunt late in the evening when the temperatures drop a bit.
Pallids are one of the most common and easily observed bats in their preferred habitat. On your next trip to eastern Washington, keep an eye out for them.