Little Brown Myotis - Consumer of Moths and “Mozzies”
These small insectivorous bats belong to the genus Myotis or “mouse-eared bats” they belong to the family Vespertilionidae (vesper bats, also known as evening or common bats). Of Canada’s nineteen bat species, the Little Brown Bat is the one most likely to be seen in urban areas. A member of the only group of mammals to have achieved true flight, they are incredibly adept at using our human or ‘built’ environment for parts of their life. (image credit Pamela Zevit)
They may still be considered the most common and widespread of Canada's bats, but the threat of extinction from the spread of White-nose syndrome or WNS (Pseudogymnoascus destructans), a deadly fungal pathogen introduced from Europe and discovered in eastern North America in 2007, led to this species being emergency listed under SARA in 2014.
A small bat, they weigh between seven to fourteen grams and have a wingspan of 22-27 centimetres. Females tend to be slightly larger than males and compared to some of the other small mammals at risk found on the South Coast, have long lifespans, with some individuals having been assessed at being over 30 years old! Compare that to a species like the Pacific Water Shrew which typically lives less than 2 years.
Females produce only one young annually and yearling survival is low (0.23 to 0.46). Pups nurse from a nipple located under the arm on each side of the mothers chest , similar to the image to the left of a female Pipistrelle Bat with her pup (image credit East Yorkshire Bat Group).
Fur colour can be variable, ranging from pale tan to reddish or dark brown with a slightly paler belly. Ears, wings and muzzle are dark brown to black.
While bats have gotten a bad rap over time due to superstition and misinformation (and yes they can carry diseases like rabies), the Little Brown Myotis and other insectivorous bats are finally getting the street cred they deserve. Lactating females can consume the equivalent of their weight in insects each night, though typically the rate is about 1000 insects per night, or half of their body weight. Their preferred diet of moths, beetles, mosquitoes (“mozzies”), midges, flies and a host of other winged insects, many of which are pests in urban and agricultural landscapes, brought to light their incredible superpowers as pest control agents! As with many other bats, they forage shortly after dusk and may also do another round before dawn. Foraging takes place in open fields, riparian areas and open bodies of water, they even forage over parking lots and roads, if there is vegetation nearby supplying insect prey. Prey is caught and eaten on the wing using their unique echolocation abilities.
Along with a lengthy age span, the Little Brown is our most widely distributed bat species, ranging from Mexico to the tree-line in northern Canada and Alaska (and possibly farther north).
As noted Little Browns use artificial structures and will readily take to bat boxes, bridges, attics (like the image to the left, credit US NPS) and barns to roost (particularly for maternity roosting), but they will also use cavities of canopy trees, foliage, tree bark, crevices on cliffs, and other non-anthropogenic structures. Some of the most notable Little Brown roost sites on the South Coast are maternity colonies at Colony Farm and Deas Island Regional Parks, both of which utilize built structures. While females often have communal maternity roosts, males tend to live the bachelor life, roosting individually or in small groups. As with other species of bats in Canada, the Little Brown hibernates during the winter, seeking out hibernacula (a place to hibernate, often in caves or crevices, though human structures may also be used). Hibernation is an evolutionary strategy which allows insectivorous bats to reside year-round in regions where temperatures drop for prolonged periods and insect prey become unavailable. Hibernating bats minimize use of fat reserves by decreasing metabolic rate and body temperature to within a few degrees of the ambient temperature in the hibernaculum (entering a state of suspended animation called “torpor”). Where Little Brown Bats go to hibernate in winter in Western Canada is a bit of a mystery, though they may use human structures, but to date there is little known about this stage of their life-history for populations in places like BC.
White-nose syndrome is an insidious disease which has wiped out vast populations of Little Browns as well as a number of other communally hibernating bat species across eastern and mind-western North America. The fungus grows in the same microclimate conditions that occur within the hibernacula where these species of bats overwinter. The fungus colonizes the bat’s skin, causes lesions, and damages sweat glands, oil-producing glands, muscles, connective tissue, blood vessels, and hair follicles. The diseases’ name is derived from the white-grey blotches that develop on the surface of the wings and ears and the muzzle often turns fuzzy white (see image, credit Marvin Moriarity USFWS). Infected bats are aroused from hibernation as the fungus spreads across and within their body. Individuals may become so agitated that they start flying within the hibernacula or leave it. During a time of the year when fat reserves must be conserved, such raised metabolic activity depletes the bats of energy and water, often leading to mass mortality. Bats that survive the infection may have damaged wing membranes and reduced reproductive success. It was only a matter of time before WNS made its way to the Pacific Northwest, and sadly the first confirmed infected bat (a Little Brown) was detected in 2016 outside of Seattle, and then another bat, a Silver-haired Bat (a species known to be a carrier of WNS), was identified, also in Washington State. While other bat populations in Washington State have since tested positive, they do not seem to be exhibiting the damaging effects of the infection. To date WNS has not been detected in BC populations.
However the potential for WNS impacts is only one facet of issues facing our South Coast bats. Habitat loss, whether due to the direct removal of roost sites (natural or anthropogenic), loss of mature forests in urban environments (especially through redevelopment) wetland loss, combined with this species’ limited reproductive rate and first-year low survival rate only serves to heighten the risk of local extirpations and potential extinction of this and other affected bat species across North America.
Like all of the species at risk conservation stories the SCCP and other conservation partners are involved with, ensuring a secure future for the Little Brown Myotis seems daunting. While it is uncertain whether or rather, how WNS will affect our coastal BC Little Brown populations, one ray of hope is that other heavily affected populations are showing some signs of resistance and recovery. As well bat conservationists are working at breakneck speed to find treatments that may help susceptible bat species or infected populations to recovery, either through treating the roost sites or through some form of direct treatment of individual bats.
As well the diligent and dedicate work of organizations like the BC Community Bat Program and our local partners the South Coast Bat Conservation Society are taking the plight and conservation of BC’s bat species mainstream. Whether it's bat tagging, at local regional parks, ongoing monitoring for WNS, public engagement, best practices guidelines and bat box workshops, these are just some of the efforts underway that are making a difference for these incredible flying mammals and insect control superheroes!
Bat Week is only one month away! (Oct 24-31, 2018)
And check out BC’s newest best management practices for bats
Little Brown Bats roosting inside a bat box (image credit eartheasy).