Alderney is home to 13 recorded bat species (out of 18 found in the UK). Common Pipistrelle stands out as the most common on Alderney. It is also the only species of bat that was recorded on every island surveyed in the Bat Bailiwick Survey 2021-2024 across Guernsey, Alderney, Herm, Sark, Brecqhou, Burhou, Crevichon, Jethou and Lihou.

Despite the idiom ‘blind as a bat’, bats can see well at night although they rely more on their ears and echolocation to avoid crashing into things and to find their prey. Bats emit high-pitched sounds that bounce off objects and return as echoes, helping them understand their surroundings, locate prey, and even gauge its speed.

Normal hearing range of humans is between 20 Hz to 20,000 Hz (20 kHz). For most people, the highest-pitched sounds they can perceive fall within the range of 15 kHz to 17 kHz. Bats echolocate at frequencies higher than the frequencies that most people can hear so their calls are beyond our hearing. To detect bats, we use bat detectors to turn the high-pitched sounds of bats into the sounds that we humans can hear.

A Common Pipistrelle has a wingspan of about 200mm-234mm. The bat is very small and lightweight, as heavy as a 20p piece (around 4-5 grams).

To distinguish a bat in flight, you need to use as many clues as possible, such as size, flight pattern, habitat, and emergence time after dusk. 

• Common Pipistrelle’s emergence time after sunset: 20-30 min and occasionally before sunset.
• Flight pattern: Fast, erratic flight at head height often along habitat edges.
• Colour: Medium to dark brown. Face and around the eyes usually dark.
• Common Pipistrelles fly between 2 m and 10 m
• Peak frequency range: 46.5 kHz (41.7 – 51.8)

Hear the sound of Common Pipistrelle via bat detectors here.

Bats hunt at night, searching for food in woodlands, meadows, gardens, and wetlands. Like all bats in the UK, Common Pipistrelle feeds on insects including flies, lacewings, midges, mosquitoes, and moths. Each night, a Common Pipistrelle can eat up to 3,000 insects. Common Pipistrelles chase flying insects and eat them on the wing, also known as aerial hawking. This technique is different from gleaning which involves picking up prey from the vegetation.

Common Pipistrelles roost in nooks and crannies in houses, barns and sheds. They also live in the outside parts of houses, in roof spaces or in cavity walls, in trees and caves.

The best place to see bats is near water at dusk such as at Longis Pond or around white streetlights (such as those on Longis Road), hedges, trees and gardens and the edge of Alderney Community Woodland.

The Alderney Wildlife Trust run Bat and Hedgehog walk between April and October, please visit the Wildlife Information Centre on Victoria Street for more information.

Bat’s life cycle

Bats wake up from hibernation around mid-March. Summer brings the breeding season, when females form maternity colonies and give birth to a single pup. Bat pups rely solely on mothers’ milk for the first 3-4 weeks. After four weeks, young bats can fly and at 6 weeks, they can forage independently. 

As temperatures drop in mid-October, bats return to hibernation sites to conserve energy through winter. All of Alderney’s bats hibernate, though not all species of bats do.

Problems that bats face:

Bats are under pressure from the loss of roosting sites, declining insect populations, habitat loss (fewer meadows, green spaces and trees) and disturbance and declining habitats.

How you can help bats

• Leave bat roosts undisturbed. Bats are very vulnerable to disturbance when trying to survive the winter or rear their pups in the summer. Having to move roosts wastes energy and can mean they abandon attempts at breeding or even fail to survive the winter.
• Keep your cats indoors from about half an hour before sunset to an hour after sunset, as bats tend to be most active during this time. Alternatively, you can attach a small bell to your cat’s collar if they go outside often.
• Garden in a nature-friendly way to attract insects which are a good food source for bats. Having a variety of pollinator friendly plants, maintaining trees and deadwood, and just leaving bits of your garden overgrown and untidy are great ways to support insect populations and so support bats.

More information:

1. What to do when you find a bat on the ground?
2. If you find bats roost under your roof, please feel free to reach out to us. We’re very happy to support you to reduce disturbance to the bats or connect with bat specialists for help.
3. Only three bat species feed on blood and they all live in South America so no vampire bats on Alderney!