Northern Myotis

Fascinating facts about the Northern Myotis

• A northern myotis weighs less than a penny yet hunts in near-total darkness by emitting ultrasonic calls 20 times per second and listening for the echoes that bounce off a mosquito's wing. Their brain devotes 30% of its cortex to processing these returning sound waves — a ratio that would be like a human dedicating half their frontal lobe to hearing alone. This biological sonar is so precise they can distinguish a single insect from background clutter and intercept it mid-flight.
• Northern myotis females are architectural engineers: they drive males away from nursery colonies and build maternity roosts inside dead trees where they give birth to pups weighing only 1 gram — about the mass of a grain of rice. A single mother can produce enough milk to rear a pup to adult size in just 21 days, then return immediately to hunting. This compressed breeding timeline happens in a window of only 4–5 months before hibernation.
• In 2006, a disease called white-nose syndrome appeared in New York caves and spread westward like a plague, killing 90% of hibernating myotis in affected regions. The culprit: a fungus that grows on their muzzle during winter torpor and wakes them repeatedly, forcing them to burn through fat reserves they need to survive months without food. Since then, northern myotis populations have collapsed by 80% across eastern North America, making them one of the fastest-declining mammals on the continent.
• A northern myotis captures and eats insects 80% smaller than itself — the equivalent of a human hunting and swallowing grains of rice without stopping. It can snag prey from water surfaces while flying, pluck spiders from webs mid-air, and filter-feed mosquitoes in loose swarms, consuming half its body weight in insects each night during peak season. Over a single summer, one bat can remove thousands of forest insects from the air.
• Male northern myotis perform an 8-month hibernation that pushes their body to the edge: core temperature drops from 37°C to just 4°C, heart rate slows from 200 beats per minute to 10, and they breathe only once every 2 hours. Yet some males don't fully hibernate — they enter brief torpor states to mate with females during winter, burning precious energy at the worst possible time. This breeding behaviour during starvation explains why males have higher winter mortality than females.

At a glance

About the Northern Myotis

In the twilight skies of North America, the Northern Myotis bat dances on the whispers of the wind, its delicate wings beating at a hypnotic pace as it pursues the faint echoes of unsuspecting insects. With each agile swoop, this nocturnal hunter weaves an intricate tapestry of sound and motion, its high-frequency calls piercing the darkness like a thousand tiny lanterns. As it flits and darts through the shadows, the Northern Myotis embodies the very essence of mystery and adaptability, a true marvel of evolution.

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