Home-Loving Bats

Bats need no home during the lush summer nights when the air is full of edible insects. By day they hang in convenient roosts--trees, chimneys or barns. But when the chill months come and insects disappear, torpor comes over them and with it a longing for their own cave, the same spot where they have spent previous winters. Bats sometimes fly 100 miles to find their old cave and sleep in it until spring.

Charles E. Mohr of Philadelphia's Academy of Natural Sciences reported in Frontiers last week on his ten-year study of the homing urge of the common (Little Brown) bat. Most bats can be caught only in caves when hibernating. No one has yet devised a bat trap for catching them on the wing. But in winter they can easily be picked from their underground perches and fitted with light aluminum bands for identification. Mohr has been banding bats for years.

Last winter a group of Cornell students joined Mohr in a thorough exploration of the bat caves in Center and Mifflin Counties, Pennsylvania. The limestone ridges there are honeycombed with small caves, but Aitken's Cave, near Milroy, is the most accessible. All banded bats were found in the same cave as in previous years. Even bats that had been carried off and released far away were back again. Only once did Mohr find an intruder: this stray bat's own cave had been sealed by a rockfall during the summer.

Charles Mohr is not the only bat-bander. Don Griffin of Harvard has banded thousands of bats in New England, had also noted the homing urge. Bats from a cave near the coast were released 15 miles at sea. Two days later they were back in their own cave.

Curiously, the caves are not used for accouchements. In early summer female bats congregate in hollow trees, barns or vacant houses. (Male bats are excluded.) Here each gives birth to her live young, only one per year, with occasional twins! The baby clings to its mother as long as it is suckling, but the mother leaves it hanging from the roof or wall while she goes on brief foraging expeditions.

Millions of bats of all kinds, chiefly Free-tailed or Guano Bats from Mexico, make their winter home in Carlsbad Cavern and neighboring caves in New Mexico.

There are a few varieties of bat which do not hibernate, including the Red Bat, the Hoary, and the Silver-haired. Some live in the forests of Washington or Canada, eating insects during the summer, but when winter comes they migrate southward.

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