By Barbara Julian
If you walk above the Dallas Road cliffs on a summer night, you might notice small flitting shadows darting close and seeming more corporeal than any shadow has a right to be. These, you realize, are bats, and for some their presence is a good reason never again to walk the Dallas Road cliffs at night.
Figures in a centuries-long literary tradition of evil, bats are few people’s favourite wildlife species. Yet from a biological point of view they’re fascinating, and perform some welcomed services. Their fast and sure-winged movements are guided largely by sounds which they send out and continuously receive back as echoes from objects around them, including objects as tiny as the insects they eat. They use vision as well, contrary to the popular idea that bats are blind. The mammal brain evolved out of the optic nerve, but bat brains evolved also to receive information from waves of sound.
Even if we appreciate their brains, however, we cannot shake the idea that bats might entangle themselves in our hair, and that their faces, claws and brittle wings are beyond ugly. The thought of thousands of them squashed upside-down in dank dark caves is the stuff of nightmares, sustaining a long tradition of vampire lore. The vampire was a corpse who left the grave at night and sucked blood from cattle or persons innocently asleep in their beds. The corpse was typically that of a heretic, and its emergence signified the stirrings of evil. The cave-grave symbolism, plus its evil-looking demeanor, gave the role of vampire to the innocent bat. There are species that do consume blood but they exist in Central and South America; the 16 species found in B.C. are insect-eaters.
Bats copulate in fall before hibernating for winter. The females delay ovulation and store sperm until fertilization takes place in spring. Males and females live separately, but some species engage in interesting unexplained extra-evolutionary sexual behaviours not describable in a community newspaper. They give birth to one infant at a time, perhaps three over a spring and summer. Babies are large at birth and cling to their mothers for a month or more, during which time she must eat prodigiously to maintain her own and her offspring’s weight. That is why a bat can eat 2,000 to 6,000 insects per night and up to 600 mosquitoes per hour.
Where, though, do bats roost during the day and for winter hibernation? The cave lifestyle of non-local bats is intriguing. Among some species a class of baby-sitting females mind the infants (as in whale and wolf societies) when mothers go out hunting at night. How does a mother bat know, when she returns at dawn with food, which of the thousands of baby bats massing in a cave is her own? Some chemical, hormonal, molecular knowledge is at work which science hasn’t explained, some universal attachment of mother to offspring.
Local bats though usually nest not in caves but in hollow trees, attics and abandoned buildings (contributing to the
“Halloween bat” imagery). No one wants them in attics, and urban forest is disappearing, so as for all species habitat loss is a major threat. Two other threats, wind turbines and the fungal disease called white nose syndrome, haven’t yet reached Victoria.
Mythology and our built-in squeamishness about ugly, black night creatures has made bats, along with rats and snakes, one of the unloved wildlife species, yet their usefulness in snapping up mosquitoes has encouraged some to put bat houses in their yards.
If you’re one of those, the website of the Habitat Acquisition Trust has a page on how to build a bat house at hat.bc.ca.