Species Spotlight: Little Brown Bat
Updated: Oct 11
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 little brown bat (scientific name: Myotis lucifugus).
Little brown bats (also commonly called little brown myotis) are light brown in color, typically four or five centimetres long and weigh about as much as a Canadian loonie (4-11 grams). They look similar to the northern long-eared bat, however little brown bats have a rounded, fleshy projection that covers the entrance to the ear.
Range and Ecology
Little brown bats have the most widespread distribution across Canada, compared to the other seven Canadian species. They can be found in every province and territory besides Nunavut. In Ontario, little brown bats are widespread and can be found as far north as Moose Factory and Favourable Lake.
In terms of roosting, little brown bats are the species most likely to roost in human structures, such as houses and garages. In the summer months, they can be found roosting in tree cavities, bridges, attics, abandoned buildings and barns. In the fall, little brown bats can migrate as far as 1,000 km from their summer roosts to their winter hibernation roosts, where they select humid caves or abandoned mines with above-freezing temperatures to spend the winter months.
Little brown bats feed on a variety of small, flying insects. They commonly feed on insects associated with waterbodies (have an aquatic larval stage), including mosquitoes, midges, and mayflies as well as moths and beetles.
This species is currently classified as 'Endangered' according to the IUCN Red List, with decreasing long-term population trends. 50% of the little brown bat's global range is in Canada, and here (as well as elsewhere) white-nose syndrome is the main threat for this species. White-nose syndrome, is caused by a fungus that infects the exposed skin of the muzzle and wings of hibernating bats. Overall, this results in bats waking up more frequently during hibernation, therefore using more energy which often leads to death. Little brown bats are particularly susceptible to this disease due to their small size and low energy reserves.
White-nose syndrome has caused huge declines of little brown bats across Ontario and other parts of their range since 2010. However, some recent scientific evidence suggests that genetic variation within individual bats can help them survive and overcome white-nose syndrome infections.
Throughout our 2020 summer surveys, little brown bats were regularly recorded at one of our riverine survey sites, making up 10% of the total number of recordings for 2020.
Spectrograms from little brown bats typically range between 100-60 kHz, leading a sweep that ends around 40 kHz. Myotis bat calls are very similar, however little brown bat calls tend to have a distinctive change in slope angle and may have a downward sweeping tail or smear at the end of the call. This species can also produce different types of call depending on their habitat.
To listen to the little brown bat call snippet above, download the MP4 file below.
To explore more little brown bat spectrograms, check out the iNaturalist Bat Spectrogram project.