Species Spotlight: Hoary Bat
To celebrate the run up to Halloween, we want to shine the moonlight on each of the eight bat species of Ontario. In this series of blog posts, we will be highlighting the key info for each species and will provide some exclusive recordings we have collected this year in our Batacea Guelph Bat Watch project.
In this post, we will be spotlighting the largest bat in Canada - the hoary bat (scientific name: Lasiurus cinereus).
Hoary bats are one of the most striking bats in Canada, with a mix of yellow-toffee, grey, brown and white fur. Despite them being Canada's largest bat (up to 15 cm in length), they weigh less than a chipmunk. Their tail membranes are furred and they have distinctive short ears with a well-defined black line bordering them.
Range & Ecology
Hoary bats are the most widespread bat species in the Americas, their range stretching from south-eastern Canada to Hawaii. This species is also migratory, meaning individual bats fly south to warmer habitats to spend their winters. During migration, they can fly as high as 8,000 feet and travel as fast as 13 miles per hour.
In the summer months in Canada, hoary bats are commonly found in coniferous or deciduous forests along edge habitats. They roost solo, hanging among foliage and use their furry tail membrane to cwtch themselves up in their own personal bat cocoon. Unlike the big brown bat, hoary bats are not often found in urban locations. During the winter months, hoary bats roost on trees, between rocks, in old woodpecker holes and even old squirrel nests.
Moths are the most common prey item eaten by hoary bats, but they also commonly consume beetles, flies, crickets, stink bugs, and burrower bugs. With long, narrow wings, hoary bats usually rely on speed as opposed to agility, hunting relatively large insects in open areas. Hoary bats are incredibly territorial of their feeding grounds when food is scarce, and they are known to show aggression towards other bat species, including the silver-haired bat and tricolored bat.
One of the mysteries surrounding hoary bats is how and when they mate. It is suspected that they mate on the wing either before, during or after the southern migration, with sperm being stored until the female ovulates in the spring. Female hoary bats often give birth to two pups (but sometimes up to four) between mid-May and late June.
Hoary bats are currently classified as 'Least Concern' according to the IUCN Red List, however little is known regarding long-term population trends.
Despite their conservation status, hoary bats are threatened by habitat loss and overuse of insecticides. It is thought that migration mortality rates are high, due to the increase in high-rise towers and other obstacles and thunderstorms. There is also increasing evidence to suggest that hoary bats feed around wind turbines, with an estimated 152,000 hoary bats being killed each year due to wind turbine collisions.
Throughout our 2020 summer surveys, hoary bats were regularly recorded across all four of our survey sites, making up 10% of the total number of recordings for 2020.
Spectrograms from hoary bats form a long, low and flat line, often at < 30 kHz. Sometimes they can form slightly upturned frequency sweeps, but mostly calls are flat.
To listen to the hoary bat call snippet above, download the MP4 file below.
To explore more hoary bat spectrograms, check out the iNaturalist Bat Spectrogram project.
Read our big brown bat species spotlight on the Batacea blog page and keep an eye out for our next species spotlight on the 28th September.