Mystery Mammals of the Night
Bats of Metchosin
June 17, 2007
Like many kids, I grew up with a fascination with all aspects of the outdoors. I happily spent summer days looking for snakes, salamanders, baby rabbits, raccoons, birds, you name it. One of the most interesting animals to me has always been those mysterious night flying creatures, that seem half bird, half mouse, sort of a modern day Pterodactyl.
About thirty people crowded the municipal chambers in June to hear the last Talk and Walk for this season. Dave Nagorsen, former curator of small mammals at the Royal BC Museum, co-author of Bats of British Columbia, local resident and a great neighbour, found time to debunk bat myths and inform us of their characteristics and benefits.
Bats are NOT flying mice! They are a family of mammals that have the distinction of being the only mammals capable of sustained flight; their wings are skin stretched across their hands. There are 1116 species of bats worldwide, making them the second largest group of mammals, outside of rodents. Most bat species are found in the tropics, where they often perform such critical duties as pollination and seed dispersal in tropical forests.
British Columbia has sixteen species of these flying wonders, the most of any province. Vancouver Island is home to ten species of bats, all of which can probably be found in Metchosin. Unfortunately bats have not been well studied here. In the 1960’s, Dave Kerridge did a survey on bats in the old, long gone Weir’s Farm barn and in the 1990’s some studies were undertaken at the DND property at Rocky Point. When he has time, Dave is also doing some research in Metchosin.
Although some bats can appear large-with their wings outstretched and flying about, they are quite small. Most weigh less than ten grams, although our largest bat, the hoary bat, can reach thirty grams (just over an ounce). All Canadian bats are insect eaters and most capture and eat their food “on the wing”. A couple of species are known as gleaners, meaning they can capture prey on branches or on the ground.
Most bat species have only one young per year while a few species can have twins. This means it can take a long time to build up bat populations if something disruptive happens to them. Some bats have been recorded as living up to thirty years, to put that in perspective, a shrew of approximately the same weight has an expected lifespan of eighteen months. Part of this longevity might be due to the bats ability to put themselves in torpor, a short-term (daily) inactive state wherein their metabolism slows down and they can conserve energy.
Roosting sites are critical to bat survival. These are natural or manufactured spaces that bats use for a variety of purposes. Depending on species and availability, roosts can be found in abandoned woodpecker nests, under the loose bark of old trees, in burnt out hollows of trees, in rock crevices, in caves, mines and tunnels, in attics or under shingles. They will also use human made bat boxes. There are three types of roosts: summer day roosts are used by maternity colonies and are generally quite hot, to protect and nourish the naked newborns. Males are solitary and find single, less exacting roosts to occupy during the day. Night roosts are used sporadically throughout the night, between feeding periods. In the winter, bats find suitable accommodations where they can hibernate unmolested (called hibernacula), at a stable temperature-usually just above freezing. A few species of our bats are thought to migrate and there is evidence that a few others might become active during warmer winter periods.
Bats use echolocation to navigate through forests and to find their prey. These 20-60 kHz ultrasonic calls are generally out of our range of hearing and they detect prey at a close range of one to five metres.
During the “walk” portion of the evening, Dave brought some bat detectors to the pond at the Metchosin Golf and Country Club Golf, where we were able to hear the calls of the silver-haired bats that were foraging over the pond.
There are no skunks on Vancouver Island but we were “skunked” that evening in our attempts to capture some bats for first hand viewing. Dave set up a very fine mesh mist net by the water in the anticipation that some low flying Myotis species might become ensnared. We were treated to some fine aerial acrobatics by the silver-haired bats and many of us were delighted to see a nighthawk flying low over the water, competing for the same insects. Their hair trigger turns and split second evasive actions were amazing to watch. The eerie cry of a solitary heron and more familiar calls of a killdeer rounded off our wildlife interactions for the evening.
Bat Species in Metchosin
Little brown bat: common across the province, maternity colonies of hundreds to thousands of females and young
Yuma myotis: most common bat on the coast
Long-legged myotis: less commonly found
California myotis: our smallest bat, quite common, can be active in winter
Keen’s myotis: red-listed, a record from Tideview Rd in East Sooke (killed by cat) where it was probably residing in a hollow maple tree
Big brown bat: studied in the Weir barn, uses trees, rock crevices, attics, may be active in winter
Townsend’s big-eared bat: blue-listed, uses old DND facilities at Mary Hill as a summer maternity colony roost and for winter hibernation, sensitive to disturbance
Hoary bat: our largest bat (to 30 grams), a tree bat that roosts under leaves on trees, migrates long distances to California, might be using the Rocky Point migration route.
Silver-haired bat: a tree bat that uses woodpecker cavities as a nursery, migratory but some might over-winter, can be active in winter
Bats are in decline worldwide from loss of trees, reduction in food sources, pesticides and disease. Eight species in BC are either blue or red-listed and one species in the Okanogan is recognized in the federal species at risk endangered listing.
If you have some wildlife trees on your property; those dead, damaged and dying older trees, consider leaving some to provide habitat for bats. Of particular importance are larger diameter, taller trees with loose bark and/or hollows. Studies have shown that bats use a series of night roosts throughout the summer, changing roost trees every few days. The reason for this is not known, but it shows how important it is to resist the urge to cut down wildlife trees. Maybe you have some that were damaged in last winter’s storms, and haven’t got around to cutting them down yet. Save yourself some effort and leave them for the bats and birds that use them as shelter.
It is illegal to kill a bat but at one time exterminators would be called into people’s homes that had bats within and they would kill all the bats. This practice no longer happens. Most local exterminators will not handle bat issues but in the US, safely removing living bats from buildings is a thriving industry. If you have a bat problem, wait until the fall, when maternity colonies are disbanding before sealing off the holes and cracks that have allowed the bats into your home. Put up approved bat houses nearby (site them south facing and paint black), so the bats will have some habitat when they return.
Bats are a main predator of flying insects and they have been found to be extremely beneficial in controlling some agricultural pests, especially on potatoes. The organic farm industry in some parts of California are erecting many bat houses, to attract bats as a tool to combat insect infestations. They are also major predators on forest pests and can eat many mosquitoes a night, helping reduce the threat of West Nile disease.
Guano, or bat poop, has been discovered to play an important role in keeping our forests healthy, by spreading nitrogen. As the bats fly back to their roosts after feeding, they deposit their guano in a manner that has them labeled as “nitrogen pepper shakers”, a suggestive image!
When people have concerns about bats, high on the list is the chance of rabies. Dave estimates that only about 1% of bat populations might carry rabies but that you should be vigilant and never handle bats, particularly bats that are acting strange or seem unafraid of you. People that study and work with bats are vaccinated to protect themselves against the chance of rabies. Vaccinate your cats if they roam outdoors, in case they prey on bats. Other concerns that have been voiced are worries about Hantavirus (bats don’t carry Hantavirus), Histoplasmosis (again, not a bat disease) and West Nile, (bats protect against West Nile by eating mosquitoes).
To help bat populations, maintain riparian habitat-which as well as protecting water quality-keeps the insect populations healthy and provides food for bats. Avoid using pesticides which are a cause for your own health concerns and which kill many insects that are bat food; erect bat houses; exclude bats from your attics in fall; and control your cats, who, although irresistibly great pets, are major predators on bats, birds and small mammals in general.
We hope you have enjoyed our Talk and Walk series, check the Muse later this summer for more information on upcoming Talk and Walks in this fall.
A special thanks to Grant West for allowing us to use his facilities at the Metchosin Golf and Country Club Golf Course and to our mayor and council for their continued support.