Myotis septentrionalis (Northern Long-Eared Bat)

The Northern Long‑Eared Bat (Myotis septentrionalis) is a small insectivorous mammal in the order Chiroptera and family Vespertilionidae. It occupies a broad swath of eastern North America, ranging from Newfoundland and Labrador through the northeastern United States, down the Appalachian Mountains into the mid‑Atlantic states, and extending westward into the Great Lakes region and parts of the Midwest. The species prefers mature deciduous and mixed forests where it roosts in tree cavities, under loose bark, or in abandoned structures such as mines, caves, and attics. Summer maternity colonies can number from a few dozen to several hundred females, while winter hibernacula are typically small groups in cool, humid caves or mines. Distinguishing features include ears that are longer than the head, a soft reddish‑brown dorsal pelage that fades to a paler ventral side, and a wingspan of roughly 22–25 cm. Its echolocation calls are high‑frequency, narrow‑band pulses centered near 45 kHz, optimized for detecting moths and other insects near foliage. Although the International Union for Conservation of Nature (IUCN) currently classifies M. septentrionalis as Least Concern, the bat has suffered population declines of 30–40 % in several U.S. states since the spread of white‑nose syndrome in 2006, leading to regional conservation efforts that include protecting hibernacula, installing artificial roost boxes, and monitoring colonies.

Myotis septentrionalis is primarily nocturnal, emerging at dusk to forage in forest edges and over water. Individuals travel within a home range of 0.5–2 km², often returning to the same roosting sites nightly. During the summer, females form maternity colonies that are highly cohesive; males are more solitary and may form small bachelor groups. The bats use a combination of high‑frequency echolocation calls (≈45 kHz) for navigation and prey detection, and lower‑frequency social calls to maintain colony cohesion and coordinate movements. Roost fidelity is strong, with females returning to the same tree cavity or artificial box for successive breeding seasons. Territorial aggression is limited; instead, individuals tolerate close proximity within the colony, relying on acoustic cues to avoid collisions. Foraging strategies include gleaning insects from foliage and brief aerial hawks, allowing the species to exploit a diverse insect community. Seasonal migrations are short‑range, with bats moving to deeper, colder hibernacula in winter and returning to summer roosts in spring.

Myotis septentrionalis is an insectivorous specialist that captures a wide array of nocturnal arthropods. Stomach‑content analyses and DNA metabarcoding studies show that its diet is dominated by Lepidoptera (especially moths), Coleoptera (beetles), Diptera (flies and mosquitoes), and Trichoptera (caddisflies), with occasional consumption of Hymenoptera (wasps) and Arachnida. On a typical night, an adult consumes approximately 0.5–1 g of insects, equivalent to 10–20 % of its body weight. The bat employs both aerial hawking—brief, high‑speed flights to intercept flying insects—and gleaning, where it plucks prey from leaves and bark using passive listening. Its high‑frequency echolocation calls are tuned to detect the fluttering wings of moths, while the elongated ears enhance passive acoustic detection of stationary prey. Seasonal shifts in prey availability lead to increased consumption of beetles in late summer and a higher proportion of flies during humid spring evenings.

Myotis septentrionalis reaches sexual maturity at about one year of age. Breeding occurs in the autumn, but fertilization is delayed until after hibernation, a strategy known as delayed fertilization. Females store sperm through the winter and ovulate in early spring, resulting in a gestation period of roughly 50–60 days. Typically, a single pup is born, though twins occur in up to 10 % of litters. Births take place in warm, protected maternity roosts where the mother nurses the pup exclusively for 4–6 weeks. Neonates weigh about 1 g at birth, representing roughly 15 % of the mother’s body mass, and grow rapidly, reaching volant status by three weeks. The mother continues to provision the juvenile with insects until weaning at about six weeks, after which the young disperse to establish their own foraging territories. Seasonal timing ensures that juveniles are ready to accumulate fat reserves before the onset of the next hibernation period.

The IUCN lists the Northern Long‑Eared Bat as Least Concern, yet regional assessments indicate steep declines of 30–50 % in many parts of its range. The principal threat is white‑nose syndrome, caused by the fungus Pseudogymnoascus destructans, which has killed an estimated 5–7 million individuals of Myotis spp. across North America since 2006. Additional pressures include loss of roosting habitat due to forest fragmentation, removal of dead trees, and renovation of historic buildings that house colonies. Wind‑energy turbines pose a collision risk, especially during migration and foraging over open landscapes. Climate change may alter insect phenology, affecting food availability during critical breeding periods. Conservation actions focus on protecting hibernacula by restricting human access, installing bat boxes to replace lost natural roosts, and monitoring populations through acoustic surveys. State and provincial agencies have listed the species as Threatened or of Special Concern in several jurisdictions, prompting recovery plans that emphasize habitat preservation and disease management.

• One of the few North American bats with ears longer than its head
• Uses both echolocation and passive listening to locate prey
• Can enter torpor at temperatures as low as 2 °C during winter
• Females practice delayed fertilization, storing sperm over winter
• Populations have declined by up to 40 % in some states due to white‑nose syndrome