Lives of Salt Spring Bats
Bats are active during the night, when they hunt insects on the wing, and bats may also be observed flying at dawn and at dusk. During the day they rest upside down in snags, live trees, tree cavities, under loose bark, in rock crevices, caves, or in attics, roofs, sheds, barns, and out-buildings. Some bat species congregate in groups and others are solitary.
Bats navigate in darkness using the echoes of their high-pitched calls (“echolocation”) that bounce off objects in the environment, like a radar system. Each Salt Spring species can be identified by the pitch, duration, and shape of its call.
In winter most bats likely hibernate locally although some migrate south. Some Salt Spring bats are active year-round but hole up and become torpid during poor weather. Torpor and hibernation allow the body temperature to drop, eliminating the need to feed in poor weather in order to heat the body.
Bat reproductive rates are low, unlike other small mammals such as mice, so population recovery from environmental impacts is problematic. Bats typically mate in the late summer or fall, and the female bat stores sperm until after hibernation. Young are born in June and July. Most Salt Spring bats have but a single pup and nurse the young for several weeks.
Bat Habitat Requirements and Environmental Threats
Bats require an abundant food supply — a nursing female may consume her body weight in food in a single evening – and bats require habitats that are productive of insects. Patches of native trees, shrubs, and herbs, natural meadows, and wetlands provide a reliable food source for bats. Wetlands are especially valuable – lakes, streams, ponds, marshes, swamps, bogs, and fens – and are focal points for bat feeding. These scarce but vital highly productive habitats are threatened by land development for housing, industry, and agriculture, which can alter hydrology, pollute waterways, and decimate wetlands.
Another risk of the insectivorous diet is exposure to insecticides. The enormous throughput of insects combined with the long lifespan of a bat (which can be decades) can result in unhealthy accumulation of insecticides in the bat’s body.
Bats require a variety of roosting sites — for resting during the day, for resting while on feeding expeditions at night (to digest and avoid predators), and for winter hibernation. Roosting bats are sensitive to temperature and humidity. Bats have a large surface area in relation to their volume, and are at great risk of body heat depletion when weather is poor, and thus require large volumes of food to compensate for heat loss when active. Reproductive female bats may seek sunny warm roosts in summer and huddle together, which helps raise temperature as needed for care of young. Non-reproductive females and males often seek cooler summer day roosts to conserve energy. If a bat colony is disturbed in poor weather, the arousal of bats from torpor may result in mass starvation.
Other threats to bats include forest clearing, domestic cats, wind turbines, and cave exploration. Nutrient pollution of ponds and lakes may result in toxin-producing algae harmful to bats. A fungal infection, white nose syndrome, has caused massive bat die-offs in eastern North America, and has been detected nearby. White nose syndrome causes respiratory acidosis, altered energy metabolism, and starvation. Human entry into caves may facilitate spread of the disease. A decontamination protocol for spelunkers can be found here: