The Noctule Bat (Nyctalus noctula)

The Noctule bat is the largest species of bat in the UK. They’re usually the first to appear in the evenings, often leaving their roosts before the sun sets.

What Does the Noctule Bat Look Like?

The Noctule bat is the UK’s largest bat. Still, it only measures 3.8cm – 4.7cm from head to tail and weighs 18g – 40g. Its wingspan ranges from 32cm – 40cm.

Noctules have plush, chocolate brown fur which can change to reddish-brown as winter approaches. Their face and wings are quite dark.

Where Do Noctule Bats Live?

Noctule bats are widespread across much of England, Wales and southwest Scotland. There a none in Ireland.

They’re tree dwellers and live in holes caused by rot or old woodpecker holes. You’ll also find them in bat boxes. They don’t often roost in buildings and if they do, it’s for a short time.

Trees and woodland are important feeding habitats. In urban areas, you might also see them around street lamps feeding on the insects that are attracted to the light.

What Do Noctules Eat?

Moths, chafer beetles, dung beetles, mayflies, and flying ants are all staples of the Noctule bats diet.

Hunting starts earlier than other bats, often before sunset. They fly above the treetops making repeated, steep dives to catch their prey which they eat mid-flight. They sometimes take food from the floor.

How Do They Breed?

Noctules mate in late summer.

Single males establish mating roosts, usually in the hole of a tree. They defend their roosts from other sexually mature males for several weeks.

Males attract female mating partners in two ways;

1. They emit a shrill mating call, either from the entrance of their roosts or while in flight, and
2. Produce a strong odur during flight

A male Noctule usually attracts 4 or 5 females (sometimes up to 20!) who stay with him for 1-2 days.

In early spring, usually April, Noctule bats form mixed-sexed maternity colonies. Usually in trees, buildings or bat boxes. Females give birth in late June into early July, usually to a single pup but twins have been recorded.

Maternity colonies often change their roosts with mothers carrying their young from one location to the next.

Mothers leave their young in creches when they go off to feed. Pups feed on their mother’s milk for 3-4 weeks. At 6 weeks old they’re fully weaned and able to forage and hunt for themselves.

Female Noctules are sexually mature by their first autumn but most don’t mate until their second year. Males become sexually active by the end of their first year.

When and Where to They Hibernate?

Noctule bats hibernate in trees, rock fissures and sometimes buildings over the winter months. Usually between November and April. On mainland Europe, hibernation colonies can be as large as 1,000 bats. In the UK, they’re much smaller.

That said, Noctules have been recorded feeding over the winter when conditions are right.

By the time May arrives, they’re fully active again.

What Does Their Echolocation Sound Like?

A bat detector can pick up their echolocation calls between 20kHz – 45kHz. Some adults and most children can hear their calls.

Threats to the Noctule Bat

Populations of Noctule bats have declined a lot in the last few decades. This is due to;

• Intensive agriculture – the heavy use of pesticides in farming has caused a drastic decline in the number of insects bats feed on.
• Loss of habits – the demand for housing and development has resulted in the loss of mature trees used for nesting and hibernation.

As a result, the Noctule bat is a priority species in the UK’s Biodiversity Action Plan. It’s also protected in the UK under the Wildlife and Countryside Act 1981.

When and Where to See Noctule Bats

Noctules bats are most active between April and September.

You’ll have the best chance of seeing them in wooded areas just before dark. They fly high above the canopy so keep looking towards the sky. You might see them diving as they hunt for their prey.