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Walk beside a stream or pond at sunset on a warm evening in the far West and you may see something dart low over the water — too quick and too erratic for a bird. It is likely a Yuma myotis (Myotis yumanensis), a small bat that lives by water more closely than almost any other.
An adult female Yuma myotis near Chiloquin, Oregon. Alice Chung-MacCoubrey
At a glance
| Family | Vespertilionidae, the vesper bats — small dark eyes, simple noses, temperate North America |
| Name | Myotis means "mouse-eared"; Yuma for Fort Yuma, Arizona, where Western scientists first described it |
| Weight | 4–6 g — about a nickel |
| Length | 65–89 mm (2.5–3.5 in), nose to tail tip — about a credit card |
| Wingspan | 238–240 mm (9.3–9.4 in), a membrane stretched across long fingers |
| Colour | golden brown |
| Lifespan | 5–8 years — far longer than a mouse |
| Range | the western United States |
Telling it apart
In the hand, it is very hard to tell from the little brown myotis (Myotis lucifugus), which lives in the same part of southern Oregon and northern California. The reliable way is by ear — with a bat detector: their echolocation calls differ. The little brown bat also ranges across North America; the Yuma myotis stays in the West.
Water, bridges and bark
- Feeds on the insects of streams, rivers and ponds — more tied to water than most bats, especially in the desert.
- Roosts, in the warm months, under bridges and in abandoned buildings, as well as in caves, hollow trees and under loose bark.
- Moves house: switching roosts during the summer is common.
- Its main stressor is disturbance at those roosts.
Hunting at dusk
Bats are not blind; most see perfectly well. What they add is echolocation — a high-pitched call from the mouth or nose, and an ear for the echo that tells them what is around them. The Yuma myotis uses both, sight and sound, to catch flies, midges, froghoppers, moths and beetles at dusk. Bats in general save U.S. farming more than $3.7 billion a year in pest control.
They are social. In spring, females gather in maternity roosts. Where and how they spend the winter is still largely unknown.
Raising a pup
| When | |
|---|---|
| Autumn | mating |
| Spring to late summer (varies by region) | one pup is born |
| First 4–6 weeks | the pup nurses, grows and learns to fly |
| After it can fly | it keeps learning from its mother and other bats where and how to forage |
Researchers near Chiloquin examine an adult Yuma myotis and note damage to its wing. Emily Heller
The threat
Since 2006, white-nose syndrome — caused by a non-native fungus, Pseudogymnoascus destructans — has devastated hibernating bats across North America and kills many species. Scientists are still working out what it means for the Yuma myotis. Meanwhile, the best protection is to keep maternity roosts and winter hibernation sites undisturbed.
Where to see one
Yuma myotis live in every park of the Klamath Network:
- Crater Lake National Park
- Lava Beds National Monument
- Lassen Volcanic National Park
- Oregon Caves National Monument & Preserve
- Redwood National and State Parks
- Whiskeytown National Recreation Area
For more, Bat Conservation International's Bats 101 covers bats in general, and the Cornell Wildlife Health Lab explains white-nose syndrome in depth.
Sources
Written from "Yuma Myotis," the Featured Creature for July 2024 by the National Park Service's Klamath Inventory and Monitoring Network; a work of the United States government in the public domain.
En estas coleccionesCrater Lake National ParkLassen Volcanic National ParkRedwood National and State ParksLava Beds National MonumentWhiskeytown National Recreation AreaOregon Caves National Monument & Preserve
Licencia: CC0 1.0 (dominio público) · Adaptado de www.nps.gov
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