Bats are in the Order Chiroptera,
which literally means "hand-wing" in latin. This name makes sense
because a bat's wings stretch over the forearm and fingers, and attach down at
the ankle bones.
Bats are mammals, which means that
they have fur, are warm-blooded, and lactate for their young like all mammals
do. Bats are the only true flying mammals (other species such as the flying
squirrels actually glide instead of fly).
There are approximately 1000
species of bats in the world, and bats live on every continent except
Antarctica. There are two subgroups of bats, the Microchiroptera, and the
Megachiroptera (also called fruit bats or flying foxes). There are
approximately 825 species of Microchiptera worldwide, and about 175 species of
Megachiroptera. The Megachiroptera are a group of large bats (primarily fruit
or nectar-feeding) found in subtropical and tropical areas of Africa, India,
Southeast Asia, Australia, and many Pacific islands. Microchiropterans are
smaller insect-eating bats found almost everywhere in the world. All of the
bats in Canada are Microchiropterans.
Did you know? That the brains of
flying foxes share a common brain structure with primates and flying lemurs?
It's possible that flying foxes evolved separately from primates, and the
smaller bats evolved from shrew-like ancestors. This topic is generating much debate
and research within the bat world.
Life History of Bats in BC
There are 16 species of bats in BC,
8 of which are considered Vulnerable or Threatened. BC has the most diverse bat
community of any province in Canada -- there are only 19 bat species known in
all of Canada!
the summer most of our female bats in BC form maternity colonies. In general,
most species roost by themselves, but sometimes we find mixed colonies of 2 or
3 species. The size of a colony is highly variable can can range from 15 bats
up to many hundreds of bats. Males tend to roost by themselves in the summer,
and use torpor (letting their body temperature drop to close to ambient during
the day) to conserve energy. Maternity colonies are usually in protected, warm
areas such as the hollow of a dead tree, underneath bark of a tree, cracks or
crevices in rocks that get lots of sun exposure, hanging off branches in the
tree canopy (hoary bat), or buildings. The exact types of roost selected varies
among the different species. Bats can have quite long lifespans (the longest
known lifespan of a Little Brown Bat in the wild is 34 years!).
tend to have one pup per year. Exactly when the pup is born can be quite
variable. The average length of gestation is 50-60 days, but can be longer;
when the spring temperature is cool, females will use torpor to lower their
body temperature and slow down gestation until the weather improves and their
food source (insects) are likely to be more abundant. In BC most pups are born
late June or July, but occasionally we capture females in August that are still
the pup is born it can weigh up to 1/4-1/3 of the body weight of the female
(that's like a human female having a 30-40 lb. baby!). The pup is fed entirely
through lactation for about the first six weeks of life (the baby is almost
adult-sized by four weeks). As you can imagine, feeding her pup entirely
through lactation represents a huge metabolic stress on the female! In order to
keep her metabolism high to produce milk for the baby and keep the pup warm,
females often seem to choose very warm roosts.
pup is weaned at approximately six weeks of age, after which it is responsible
for catching its own prey. All of our bats in BC (and Canada) eat only insects.
The size of insect they eat, and their method of hunting varies among species.
For example, our most common bats, the Little Brown Bat (Myotis lucifugus)
and Yuma Myotis (Myotis yumanensis) hunt in the air (hawking) and eat
small flying insects such as mosquitoes and flies. A Little Brown Bat can catch
up to 600 mosquitoes in an hour! Another method of hunting is gleaning (eating
insects off vegetation, tree trucks, buildings, or the ground. This can be
accomplished by hovering over the vegetation, or by crawling along the ground).
Bats must add on an additional 40% to their body weight in stored fat reserves
to make it through the winter.
in late August, maternity roosts begin to break up, and bats begin 'swarming' around
their hibernation site. One of our bats, the Hoary bat (Lasiurus cinereus)
might migrate all the way down to Mexico to over-winter, but the rest of the
species likely hibernate in BC. Bats in BC seem to hibernate almost exclusively
in caves, but we know very little about BC hibernation sites in general. Caves
that are chosen appear to have very stable low temperatures, and high humidity
which prevents bats from becoming dehydrated while hibernating.
bats are swarming and getting ready to hibernate, mating takes place. Females
store the sperm over the winter and do not ovulate or fertilize the egg until
the following spring. This is known as delayed fertilization, and bats are the
only mammals that employ this strategy.
hibernate the entire winter in BC (typically November until March), only emerging in the spring when their
insect prey emerges as well. This means that bats hibernate for at least 5
months! During this period, bats live entirely on their energy reserves. Their
body temperature drops to about ambient temperature, and their breathing and
heart rate becomes very slow. All of the hibernation sites known in BC are in mines or caves.
are exceptionally vulnerable to disturbance while they are hibernating.
disturbed they use a large amount of their stored energy reserves to
and might be left with too little energy to survive the winter. If you
come across a hibernating bat, please leave the area immediately! and
report your sighting to Ministry of Environment biologists Laura Friis or Trudy Chatwin.