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Bats through the seasons – Summer

With summer here and the days at their longest, right now Devon’s greater horseshoe bats are at their busiest. The hedges are thick with leaves, the wildflowers are in bloom and the warm air full of insects, making it the perfect time for female horseshoes to rear their young.

A female greater horseshoe bat with her pup
A female greater horseshoe bat with her pup

The reproductive cycle of the greater horseshoe bat is fascinating. Female bats visit the males’ roosts and mate in the autumn. They don’t ovulate until the following spring, however, and gestation takes around eighty days. In June and July, the pregnant females gather together in warm, quiet barns and churches to undertake the miraculous task of giving birth while suspended upside down.

New-born greater horseshoe bas are about the size of a bumblebee, and from the moment of birth are able to cling to their mother’s fur with their claws. Despite the misleading saying “as blind as a bat”, greater horseshoe bat pups open their eyes after about a week and can navigate their way around the crowded maternity roost while their mother is out foraging.

Mothers tend to forage near their roosts, generally staying within a 5km radius, but will travel further if insect prey is scarce. Their diet changes slightly in time with the seasons: in one study, greater horseshoes were shown to eat more craneflies, dor beetles and cockchafers in April and May, more moths in the summer months and more dung beetles in autumn.

Greater horseshoe bats have two main methods of catching their prey. The first, known as ‘aerial hawking’, involves flying low over the ground along woodland edges and hedgerows, catching insects on the move. The second method, ‘flycatching’, is much more energy-efficient and is unique among British bats. Using the branch of a hedgerow tree as a perch, the bats dart out to intercept passing prey and take it back to the perch to eat. One thing conservationists surveying for greater horseshoes look for is the piles of chewed up beetles and moths on the ground beneath a tree, a good clue that a greater horseshoe bat has been using it as a foraging perch.

After eight weeks of devoted care by its mother, a greater horseshoe bat pup is weaned and ready to leave the roost to begin foraging on its own. It will have just a couple of months to fatten up before hibernation. Although it won’t be ready to mate for a while (3 years on average), if it is a female, she may well return to the roost where she was born in several summers’ time.

Have a look at our live cam footage of a greater horseshoe maternity roost in South Devon to see how this year’s generation are getting on.

For a closer look at the life cycle of the greater horseshoe bat, see this beautiful French documentary.

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