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How you can help look after bats

Where do they go in winter?

Tiny bat held in hands while feeding on a small larva
A soprano pipistrelle eating a mealworm larva. This shows just how small this bat species is.
Kristin Marie Skaar Communications adviser
Presented by: Presented by: University of Agder
Published

When zoologist Roar Solheim opened the first of several bat boxes at Campus Kristiansand at the end of September, he saw six small soprano pipistrelles huddled close together under the roof.

There they hung, resting, as they do during the day, presumably after a night of hunting. A single bat can catch several thousand insects in one night.

“I was really pleased to see that they’d found the spot and started using it,” says Solheim.

On behalf of the University of Agder, he has been monitoring the 15 bat boxes on the university campuses in Kristiansand and Grimstad since they were installed in 2024.

It soon became apparent that several of the boxes had new occupants since he last checked.

Six brown soprano pipistrelles clustered beneath the rough roof of a bat box.
Six soprano pipistrelles resting beneath the roof of one of the bat boxes in Kristiansand, September 2026.

A threatened species

Norway is home to 11 different bat species. Several of these are vulnerable, and bats are protected under Norwegian law.

As in other parts of Europe, insect numbers are also declining here in Norway. This makes it harder for bats to find food.

"Bats also need safe places to rest during the day and good places to hibernate. In the wild, hollow trees may provide this. Such trees are becoming increasingly rare," explains Solheim.

Bats are the only mammals in the world that can fly actively using their own wings. They prefer to avoid flying during the day, as this is when they are most vulnerable to birds of prey and owls.

In 2024, Solheim helped install bat boxes in the woodland areas on both campuses, as part of the university’s efforts to increase biodiversity.

Hands in a red sleeve hold a weathered grey rectangular object outdoors.
The boxes are the same height as ordinary bird boxes. However, they are hollow and usually have a narrow opening at the front through which bats can easily slip in – an opening that is too small for birds to enter. The design is intended to provide them with safe places to roost and breed.

"We have a good chance of doing something for mammals such as bats and hedgehogs around our campus area. We know they’re struggling. With bat boxes, flower meadows, natural vegetation and, in the long term, more small ponds, we can ensure that the bats have good opportunities to hunt for food and find safe hiding places," says Solheim.

Bats in Norway

  • Norway is home to 11 bat species. All are protected, and several are vulnerable.

  • Bats are the only mammals capable of active flight.

  • They use echolocation – emitting high-frequency sounds and listening for the echoes – to find their way and catch insects in the dark.

  • With the aid of small electronic devices, known as bat detectors, it is possible to hear the bats’ sonar calls.

  • All Norwegian bats hibernate in winter and can survive for long periods without food.

  • Bats need safe daytime roosts and hibernation sites. The decline in insect populations, including in Norway, reduces the food availability for bats.

(Source: Store Norske Leksikon, zoologist Roar Solheim)

From 1 to 14 soprano pipistrelles

The boxes that have been chosen work well as roosting places for small bat species. Soprano pipistrelles have previously been observed around the university grounds, and it is this species that has now moved into the boxes on both campuses.

Last year, Solheim found 1 bat in the boxes. This autumn, he found 14.

"This may be because I checked earlier this year than last year. But I also found more signs of bat activity in the boxes this time," he says.

Solheim is nevertheless surprised that the majority of the boxes have not been visited by bats, particularly in Grimstad.

"It’s not easy to understand why. It’s one of the many mysteries surrounding the lives of bats," he says.

Close-up of a hand holding a small brown bat beside a weathered black box.
Common pipistrelle found in one of the boxes at Campus Grimstad.

Where do they go in late autumn?

Soprano pipistrelles use the boxes throughout the summer months, and most frequently in late summer. By then, the females have finished breeding and the young bats are flying independently.

"Soprano pipistrelles have one offspring per year, and they are born in June and July. After three to four weeks, they are able to fly. When autumn arrives, the females are ready to mate again," says Solheim.

The soprano pipistrelles then engage in a sort of courtship ritual. In one box, there may be one male and several females. In another, there might be a solitary male or a group consisting only of females.

As the nights grow colder, the bats look for places to hibernate. From late October and early November, the boxes will be empty. They then fly to places where the temperature remains stable and above freezing.

"We know very little about exactly where the soprano pipistrelles hibernate. That's one of the reasons why this species is somewhat mysterious. Other species tend to hibernate in caves or disused mines. In the Modum mines near Blaafarveverket, for example, nearly 160 bats have been found. But no soprano pipistrelles," says Solheim.

Exactly when the bats disappear depends on the temperature. But the chance of spotting bats outdoors at dusk around Halloween is probably slim.

"It’s likely that many have already found their hibernation sites. If the weather remains mild, some may still be active well into November," he says.

Vulnerable to vandalism

It is only when the temperature rises in late spring that the bats emerge from hibernation and become active again.

Solheim therefore waits until late autumn to make any adjustments to the boxes, when he knows they have left.

"Three of the boxes in Kristiansand have been damaged or have gone missing this year. One of the boxes is missing parts, whilst two others have disappeared completely – probably removed by people. It’s a real shame. The solution is to hang the boxes higher up in the trees, out of reach," says Solheim.

You can do this yourself

It’s not just professionals who can help address the housing shortage for bats.

If you have a garden or your own woodland with tall trees, you can hang up bat boxes yourself.

"The important thing is to hang them facing west and without anything blocking the sun, so that the boxes warm up in the evening. Bats seem to like this," says Solheim.

The zoologist has himself hung up his own bat boxes in Denmark.

Earlier this year, he found around 30 pipistrelles huddled together in one of the boxes when he went to have a look.

The Norwegian Society for the Conservation of Nature has some useful tips on how to make your own boxes.

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Read the Norwegian version of this article on forskning.no

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