Grey Long-Eared Bat (Plecotus austriacus)

The Grey Long‑Eared Bat (Plecotus austriacus) belongs to the order Chiroptera and the family Vespertilionidae. It is a small, insect‑eating bat distributed across much of temperate Europe, extending into western parts of Asia such as the Caucasus and northern Iran. Preferred habitats include mixed deciduous‑coniferous forests, hedgerows, and riparian woodlands, but the species also roosts in human structures, attics, and abandoned mines. Its most distinctive feature is the exceptionally long, funnel‑shaped ears that can be half the length of its head, aiding in passive acoustic detection of prey. The fur is a muted grey‑brown on the dorsal side with a paler ventral surface, providing camouflage among bark and leaf litter. Although currently listed as Least Concern by the IUCN, populations are thought to be declining due to habitat loss, pesticide use, and disturbance of roost sites. Conservation actions focus on protecting roosting habitats, maintaining forest connectivity, and monitoring population trends across its range.

Grey Long‑Eared Bats are nocturnal and emerge at dusk to forage, often flying low over water surfaces and forest edges where insects are abundant. They are solitary roosters but may form small maternity colonies of up to 30 females during the breeding season. Home ranges are relatively small, typically 2‑5 km², and individuals show strong fidelity to known roosts. Communication relies heavily on low‑frequency echolocation calls (20‑30 kHz) that are less detectable by many insects, complemented by social calls used in mother‑pup interactions. During the day, they hang inverted in narrow crevices, tree cavities, or roof spaces, selecting sites that offer stable microclimates and protection from predators. Territorial aggression is limited; overlapping foraging areas are common, and individuals may share feeding sites when prey is plentiful.

The Grey Long‑Eared Bat is a strict insectivore, feeding primarily on moths (Lepidoptera), beetles (Coleoptera), and flies (Diptera). Studies of guano analysis across its range show that moths constitute up to 60% of its diet, especially noctuid and geometrid species that are active near forest edges. Beetles, particularly ground beetles (Carabidae), make up 20‑30%, while the remaining portion includes dipterans and occasional spiders captured incidentally. Foraging is conducted using a combination of passive listening—detecting the wing beats of moths—and low‑frequency echolocation that penetrates cluttered vegetation. Individuals can consume up to 0.5 grams of insects per night, equivalent to roughly 10% of their body weight, and may make several foraging bouts per evening depending on prey availability and temperature.

Females reach sexual maturity at 10‑12 months, while males mature slightly earlier. Mating occurs in late summer (August‑September), after which females store sperm until ovulation in spring. Gestation lasts about 50‑60 days, culminating in the birth of a single pup in May or early June. Newborns weigh roughly 1.5 grams and are altricial, relying entirely on maternal milk for the first three weeks. The mother visits the roost daily to nurse the pup, which grows rapidly, reaching a weight of 5‑6 grams by the end of the nursing period. Weaning occurs at 4‑5 weeks, after which the juvenile begins to forage independently but may remain near the natal roost for several months. Sexual maturity is typically reached the following year, allowing for an annual reproductive cycle.

The IUCN classifies Plecotus austriacus as Least Concern, yet regional assessments indicate declining trends in parts of its range. Primary threats include loss of roosting sites due to building renovations, demolition of old structures, and forest management practices that remove dead trees and snags. Pesticide application in agricultural landscapes reduces prey abundance and can cause direct toxicity; studies have detected neonicotinoid residues in bat guano at concentrations up to 15 µg/kg. Climate change may shift insect phenology, leading to mismatches between bat emergence and peak prey availability. Population estimates suggest there are roughly 1‑2 million mature individuals across Europe, but numbers are fragmented, with isolated subpopulations in the Balkans and the Iberian Peninsula showing signs of local extirpation. Conservation measures focus on preserving roosting habitats, installing bat boxes, and promoting pesticide‑free farming zones.

• The ears of P. austriacus can be up to 30 mm long, nearly half the length of its head.
• It uses passive acoustic detection more than echolocation, allowing it to locate silent moths.
• Females can store sperm for several months before fertilizing eggs in spring.
• Grey Long‑Eared Bats often roost in roof spaces of historic buildings, making them important bio‑indicators of heritage site health.
• Despite its small size, it can travel up to 30 km during seasonal migrations in northern Europe.