Lucky to see a bat? Naomi Klein, among her grave predictions in “This Changes Everything”, worried that climate change might prevent her young son from ever seeing a bat. When writing the book (2013), she observed that 100,000 bats were dying due to record-breaking heat in Queensland, Australia, leaving the bat colony devastated. Four years later, by 2017 – a year that Naomi concluded would be the turning point for taking possible action to control a 2ºC global warming – North America has had millions of bats wiped out due to White Nose Disease.
Fortunately, we are still lucky enough to have a rich and abundant bat biodiversity on Denman. Retaining bat-sighting opportunities for future kids is certainly important. As is retaining bats to eat flying invertebrates that feed on us and our plants, and also maintaining the bats’ place in our complex ecosystem-web. So this year DCA embarked on a project to enhance bat habitat and build community bat awareness.
So what’s it like to grow up as a bat?
FALL
As the bats get ready to leave Denman in the fall, the sexes meet up and conceive the next bat generation. Currently we have at least 9 species of insect-eating bats that are starting to leave their summer haunts for their winter hibernacula. Bat houses empty out, and roofing, shakes and other crevices no longer scratch and squeak with noisy occupants. Small guano piles are all that remain! While mating takes place in the fall, actual fertilization and embryo growth doesn’t occur until the female bats are en route to the summer roost sites in the spring.
WINTER
Bats get to sleep through the winter. Generally bats need protected hibernacula for the winter, with a constant humid environment and temperatures of 0-5ºC. Most bats hibernate off Denman, but a few stay and are seen on mild winter evenings. Why do some stay? We don’t know. Nor do we know if these ones survive, especially if it gets very cold. Where are these off-Denman hibernacula? That’s another unknown!
If folks see bats in the winter, please record the date/time/place of your sighting at email dhbatproject@gmail.com or 335-2151. Also, please let us know of any dead bats found. All observations are important and add to our understanding of Denman’s bat life!
SPRING
Bats return! Mums are pregnant with their developing offspring. The gestation lasts 7 weeks, but can be delayed up to 10, if the temperatures are cool. Bats come back to where they were born, or to new suitable sites in their birth neighbourhood. Once in the bat house, large tree, building or other crevice, babies are born. Baby bats, usually one per mum, are helpless like puppies and are about 25% of the mum’s weight. In bat houses, groups of mums and young huddle together for warmth, chatting and squirming. Females of the two bigger forest bat species may roost in colonies or family groups, in trees, and may have 1 to 4 young.
Maternal bat colonies need lots of heat – such as bat houses with full on sun! On cool days, mums can’t chill their metabolism and go into torpor as male bats do. Nursing babies requires that mums stay warm and thus maternal colonies must be in hot habitats. Each warm evening, mums head out to drink from the nearby pond or other water source and then hunt for insects.
SUMMER
Baby bats grow remarkably fast. In just a few days they can see, their ears are up and their fur grows, often darker, duller and shorter than their mum’s. By 3 to 6 weeks they are adult size, they can fly, echolocate and eat solid food! At this time they are weaned.
Thus, near the end of July, young bats take their first flight. Tumbling from their perch as they test those wings…the only mammals capable of true flight! Their thin winged-arm membranes can carry them, as most bat species weigh only about as much as a loonie or toonie. The young bats practice complex flying exercises and also learn to hunt insects by mastering advanced echolocation techniques in the dark! But there’s always a few timid young that cling to solid supports, crash land or can’t get home as day approaches. Sadly many of these won’t survive. Here on Denman, cats are likely one of our bats biggest predators.
Gradually the young become proficient in flying and hunting insects. As they do, they move out into the forest with the adults. Some bats will try new day roosts near their birth-place. This is the time when the future mum’s may explore and spend a day or two in your new bat house. All the while they are feeding on as many insects as possible to accumulate enough energy to last through the long winter. Young female bats may mate the following fall and, in the spring, head back to maternal colonies. Young males will return to Denman next spring to patrol for insects and spend the summer days hanging out in a variety of crevices or unoccupied bat houses. Our long-lived bats, like the Little Brown bats that may reside on Denman for up to 30 years, keep our forest and meadow ecosystems complex and healthy.
Caution
Always Think Rabies First! – do not handle bats without gloves and care!
Bat Calendar Summary
April-May:
Adults return to Denman. Most females fly to maternal colonies in bat houses or other warm maternal habitats. Males travel around Denman, roosting in a variety of crevice habitats. Large forest bats roost in trees.
May-June:
Female bats hunt insects, birth young and nurse babies in maternal colonies. Males hunt insects.
July:
Young bats take first flight. All bats are hunting insects.
August-September:
Bats, still hunting insects, move out into forests and may check out new day-roost habitats (additional new bat houses).
September:
Bats mate and leave Denman for hibernacula at unknown destinations.
October-April:
Most bats hibernate in cave-type sites with a stable temperature and humidity. Disturbances at hibernacula can lead to exhaustion of the bats’ winter reserves resulting in disease and death of the bat colony. Much work in the USA has been done to protect old mines and caves where bats hibernate. Most hibernacula in BC are unknown.
