Eastern Pipistrelle

Fascinating facts about the Eastern Pipistrelle

• Weighing just 4.6-7.9 g (0.16-0.28 oz), the tricolored bat is the tiniest bat in the eastern and midwestern United States, with a forearm length of 31.4-34.1 mm (1.24-1.34 in) and a wingspan of only 21-26 cm (8.3-10.2 in). yet the animal can live nearly fifteen years in the wild, showing how a minuscule body can achieve a surprisingly long lifespan in a harsh, seasonal world.
• Mating happens in the fall, but females keep the sperm frozen in their uterus through winter, only ovulating in spring. After a 44-day gestation, twins are born in June or July, together weighing up to 58 % of the mother's post-birth mass. The newborns are hairless and blind, yet they start flapping by three weeks and are hunting insects on their own by four weeks, illustrating a rapid life-history strategy that lets them survive short northern summers.
• In Nova Scotia, researchers found nearly one hundred tricolored bat roosts, all inside the beard lichen Usnea trichodea, the first known case of a bat using lichen as a home. Scientists think the bat may be exploiting the lichen's usnic acid, which repels insects and bacteria, because no external parasites have ever been recorded on these individuals. If true, the bat is turning a chemical-rich plant into a natural anti-parasite shield.
• Once among the most common eastern bats, the tricolored bat's numbers collapsed after white-nose syndrome arrived in 2006, with mortality exceeding 70 % in many states. The disease kills by forcing bats to wake from torpor and burn their limited fat stores. Even as populations dwindle, the species still accounts for 16 human rabies deaths from 1958-2000-46 % of all US indigenous bat-related rabies fatalities, highlighting its public-health relevance despite its rarity.
• Since the 1980s the tricolored bat has pushed its frontier westward, now reaching Colorado, New Mexico, South Dakota and Wyoming, and even colonising the Great Lakes Basin.

At a glance

About the Eastern Pipistrelle

As dusk descends, the Eastern Pipistrelle takes to the evening skies, its delicate, almost translucent wings beating at a hypnotic pace as it pursues the swarms of insects that dance in the fading light. With an agility that belies its tiny size, this diminutive bat darts and weaves through the trees, its high-pitched calls echoing through the forest like a chorus of whispered secrets. In this fleeting, crepuscular world, the Eastern Pipistrelle reigns supreme, a master of the margins, where day and night entwine.

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