Best time to see: May to end Sep
Key facts
The smallest European bat, typically weighing 6 or 7g, and also the most widespread in Essex
Often roost and nest in the roofspace of houses and have declined because of toxic timber treatments and better sealing
Ultrasonic bat detectors have revealed two closely related species, one calling at 45kHz and one (soprano) at 55kHz
Recognition
Brown or reddish brown fur with small triangular ears
Usually fly at or just above head height, zigzagging from side to side in search of prey
Feed on small flying insects like midges, using echolocation to locate and home in on their prey
Lifecycle
Roost in the roofspace of houses and in holes in old trees and can often be seen leaving at dusk to hunt for food
Females have one litter a year in summer, joining nursery colonies of up to 1,000
Hibernate from autumn to spring, hanging in clusters sometimes numbering 1000s of individuals
- Main photo
Photo © Geoff Pyman