Among the foliage of eastern North American forests hangs one of the continent's most colourful bats, the Eastern Red Bat, wrapped like a dry leaf. Its reddish-orange fur and its habit of roosting directly among leaves, rather than in caves or buildings, make it almost invisible to a casual observer. Each autumn it undertakes a southward migration, often in groups, to escape the harsher winters of its breeding range. Its cold tolerance and its ability to enter torpor allow it to survive even on the coldest autumn nights.
It measures 95-115 mm in total length, with a forearm 35-45 mm long. The fur is bright orange-red in males and somewhat duller, with greyish tones, in females; both sexes show white patches on the shoulders and at the base of the ears. The ears are short and rounded, and the uropatagium is densely covered in fur on the dorsal surface, a typical adaptation for bats that roost in foliage. The Eastern Red Bat is distinguished from Lasiurus frantzii, its recently separated western relative, mainly by genetic and geographical distribution criteria. They are practically indistinguishable in the field where their ranges do not overlap.
Sonograms and echolocation: The Eastern Red Bat emits FM-QCF pulses. These have a variable characteristic frequency, generally 40-50 kHz, and a short pulse duration, 5-8 milliseconds long. This is typical of species that hunt in relatively open spaces above the canopy or near light sources. It can be confused with other similarly sized Lasiurus species, particularly in areas of contact with L. frantzii, where reliable acoustic separation is not always possible.
It leaves no detectable fixed roost, as it perches loosely among foliage. The most reliable physical indication of its presence is the occasional finding of an individual hanging among leaves, partially wrapped in its own patagium.
It inhabits deciduous and mixed forests of eastern North America, from southern Canada to Mexico, roosting among the foliage of medium to high canopy trees. It migrates seasonally southwards within its range or to Central America during winter.
It feeds on a wide variety of nocturnal flying insects, including moths, beetles and mosquitoes, caught in flight above the forest canopy or near artificial lights.
It is solitary for most of the year, perching individually among foliage, though it may migrate in loose groups. Females give birth to litters unusually large for a bat, of up to four young, which they carry with them during the first few days of life. It enters torpor during cold nights, allowing it to survive low autumn temperatures.
Eastern Red Bat is one of the most common and widely distributed bat species in eastern North America, although doubts persist about recent population trends.
Collisions with wind turbines during autumn migration represent a significant source of documented mortality. The loss of mature forests and the use of insecticides also affect its availability of prey and refuge.
See all species accounts for bats · Full species index
Mammaling is a free app for logging the mammals you find. You record a sighting in a moment — even if it's just a track — your life list grows, and the record becomes available to scientific and conservation projects.
It runs on your phone with nothing to install. If you like, it adds to your home screen like any other app.
Open Mammaling