APRIL
Bats
come out of hibernation this month after almost 6 months asleep. The first
really warm days bring them out of torpor. The first things they do is drink and
replenish their food reserve which by now is at a minimum
MAY
During this month male and
female bats go their separate ways. The males go off to roost alone or in small
bachelor roosts. The females go to pre-maternity roosts where their numbers can
be into the hundreds. As soon as the female bats are in back in good condition
they fertilize their single egg. It’s only on a rare occasion that they have
twins.
JUNE
Pregnant
female bats arrive at their maternity roosts where young bats, pups, are born
anytime from the middle of May to the first week of July. Most young are born
during June. Pups are born very large the equivalent of a human mother having a
child the size of a 5 year old.
JULY
Young bats grow really fast
and can fly at 6 weeks. In the weeks leading up the independence the volume of
bat sounds coming from a roost can be quite loud especially when the mums are
about to leave the roost to feed.
AUGUST
This month the female bats
gradually leave the roosts to be followed later by the young. From now until
late autumn bats must put on a lot of body fat which will see them through
hibernation period.
SEPTEMBER
This is the mating period as
males set up breeding harems at this time of year. They ‘sing’ from inside
crevices, tree hollows or under copingstones. The song, to our ears, is like two
coins being hit together. Although bats mate now the egg isn’t fertilized
until the female is out of hibernation. This is called delayed fertilization and
female bats are one of only a few mammals that can store sperm, alive, in their
own bodies.
OCTOBER
TO MARCH
During early October bats prepare for hibernation by finding suitable places like cellars, mines, caves, icehouses. These places are unlikely to vary in temperature during hibernation. The ideal range for a bat is 0 – 5c or F. while a sleep during hibernation a bats body temperature fall to match that of it’s surrounding air. Breathing goes down to a minimum and the heart may only beat 6 times a minute. The bat’s body goes into a state of suspended animation. Bats are the only mammals that can have such a wide range of body temperature that would kill any other. This range is 0c while hibernating up to 40c while in flight. Before bats go into hibernation they must increase their body weight by at least one third.