Bats spend most of the winter hibernating, a state of inactivity characterised by lower body temperature, slower breathing, and lower metabolic rate.

Bats are still hibernating. They have little fat left to live off of now. They may leave the roost on warmer nights to find food and a drink of water.

Bats may begin to emerge and signs of limited activity can be seen. There are small numbers feeding as it gets warmer. In bad weather, they may become torpid.

Bats have mainly come out of hibernation and are hungry and active, feeding on most nights. They may move between several roost sites and can become torpid (cool and inactive) again when cold.

Bats are fully active and feeding. Females start forming maternity colonies and looking for suitable nursery sites, such as buildings or trees. Males roost on their own or in small groups.

Female bats usually give birth to a single pup, which they feed on their milk. Young bats are very small (less than an inch) with thin, slightly grey fur. Adult bats will catch thousands of insects each in a night.

Mothers continue to suckle babies. Some bats grow fast and are almost full-size; others are still very small. At around three weeks, young bats are sometimes found on the ground as they learn to fly.

At six weeks old, the young bats begin to catch insects for themselves and no longer need their mothers’ milk. The summer maternity colonies begin to disperse and bats may move to mating roosts.

Mating season begins. Males of most species use special calls to attract females, which can include purrs, clicks, and buzzing. Bats also concentrate on building up fat stores for the coming months.

More mating is taking place, and building up fat reserves is becoming crucial to survive the winter season. Bats are seeking suitable hibernation sites, and beginning periods of torpor.

Periods of torpor are lasting longer. Some begin hibernation, to save energy over the colder months, when insects are harder to find. They are using stored fat as fuel.