Eurasian Serotine

Fascinating facts about the Eurasian Serotine

• A bat that hunts at dusk can catch and eat 40% of its body weight in insects before midnight — a Eurasian serotine weighing 8 grams will consume 3 grams of mosquitoes, flies, and midges in a single night. It hunts from 10 to 50 metres above ground, higher than most European bats, scanning the air with echolocation that clicks 10 times per second and adjusts to 200 clicks per second the moment it locks onto prey. This feeding rhythm lets it survive on temperate insects that other bats can't reliably find.
• The Eurasian serotine's ears stay upright even while roosting — a permanent listening post that lets the bat detect predators and competitors without opening its eyes, and without changing body position. Most bats fold their ears when resting; serotines don't. This vigilance costs energy, but buys survival in roost sites shared with owls and domestic cats.
• These bats return to the same roost every autumn, sometimes for over 20 years, picking the same building or tree cavity they used the previous season — a fidelity so strong that individual serotines are recognisable by roosting spot alone. Some populations migrate south for winter; others stay and enter torpor (a metabolic pause) for weeks, surviving on fat reserves. The ones that return migrate just 200 to 300 kilometres, barely a fraction of the distances other European bats travel.
• In mating season, male Eurasian serotines broadcast ultrasonic 'songs' from their roosts — frequency-modulated calls that advertise body size and health to females, like a mammalian peacock call but 40 kilohertz above human hearing. Females approach males with good songs more often, and males with larger body size sing louder. This acoustic marketplace happens every autumn, before females ovulate the following spring.
• The Eurasian serotine is one of Europe's few bat species that reliably coexists with human buildings — it roosts behind shutters, under eaves, and inside church bell towers across cities and farms alike. Unlike bats that vanish when humans clear forests, serotines adapted to human architecture 500 years ago, making them one of the most abundant bats in temperate Europe today and a living proof that some species thrive alongside us if we don't actively poison them.

At a glance

About the Eurasian Serotine

In the twilight hours, the Eurasian Serotine bat takes to the skies, its leathery wings beating with a soft whoosh as it dances through the shadows, a master of the crepuscular realm. With echolocation calls that pierce the fading light, this diminutive creature navigates the intricate landscape of trees and buildings, its agility and cunning allowing it to thrive in a world of human dominance. As it flits and weaves, its dark silhouette is punctuated by fleeting glimpses of chestnut-brown fur, a fleeting reminder of the beauty that lies just beyond the reach of our everyday perception.

Discover more wildlife