JACKSON, Wyo. — It’s Bat Week, and Yellowstone National Park is getting into the Halloween spirit sharing information about the bats in the Greater Yellowstone Ecosystem.
Bat Week is an annual celebration aimed at raising awareness about the need for bat conservation. This year, Bat Week is Oct. 24-31.
In Yellowstone, there are 13 species of bats that are all insectivores (insect-eaters). Bats are the only mammals capable of sustained, flapping flight, which has given rise to a great diversity of species throughout the world.
To support the energy demands for flight, insectivorous bats must eat a large number of insects. Nursing females may consume their own body weight in food each night during the summer. Bats develop and reproduce slowly. Most give birth to one pup a year, although four species in the greater Yellowstone area have two or more pups at a time. These species typically begin flying in 2–6 weeks, are weaned around 5–10 weeks, and become mature in 1-2 years.
In temperate environments, bats mate in late summer or autumn, just before entering into hibernation for the winter. In bats that hibernate, fertilization is delayed until the female emerges from hibernation. For most Greater Yellowstone bats, hibernation ends around mid-April and the females give birth in mid-June.
During spring and summer, bats tend to be highly localized near sources of food, water, and roosting structures. They roost in natural habitats, including thermally heated caves, as well as in bridges, buildings, and other human structures, which can lead to conflicts with human use and historical preservation plans.
Bats use an echolocation system to navigate and find food in the dark. Many species produce pulses of high-frequency ultrasonic sound and listen for the returning echoes. The echoes provide bats with a sonic picture of the environment which includes the movement of prey. High-frequency calls are less likely to alert predators and are effective for locating prey, although some moths have developed organs on their abdomens capable of detecting such calls. Most bats also use lower frequency calls to communicate with each other. Contrary to the expression “blind as a bat,” bats typically have excellent vision used for hunting.
Bats predators are generally opportunistic and include owls, falcons, hawks, snakes, and raccoons. Of bats that survive their first year, 40–80% survive 7–8 years; many bats live 10–30 years.
At rest, bats roost head down, which makes them less vulnerable to predators and facilitates flight. A bat can remain upside down for months because of cavities in its cranium that pool blood and other fluids away from the brain and an arrangement of ligaments and leg muscles that enable them to hang passively from its perch while sleeping.
The fungal pathogen Pseudogymnoascus destructans, which causes white-nose syndrome (WNS), has been responsible for declines as high as 99% in wintering bat populations, leading to regional extinctions of several species in northeastern North America. In 2016, two bats were confirmed to be infected in Washington State. Bats cannot recover quickly (if at all) from these substantial population declines because most species that are vulnerable to WNS rear only a single pup per female each year.
Female bats captured with mist-nets and fitted with radio transmitters have helped to identify buildings that serve as maternity roosts (where females raise young) for little brown bats. Research suggests that access to building attics within Yellowstone National Park is critical for their reproductive success and long-term conservation.
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