Hidden Heroes

Human visitors are not allowed on the refuge between dusk and dawn, but the refuge is still alive with activity during the dark hours. Rarely seen and difficult to study, bats are little-known and very misunderstood. But each night during summer, there are more bats on the refuge than most people realize.

During the day, bats roost away from human eyes in small rock crevices , caves, abandoned mines, under loose tree bark, in tree foliage, in barns and attics, or even in bat boxes designed to attract them. At night, they emerge from their roosts to hunt for insects. Graceful and acrobatic, they use echo-location and their large, sensitive ears to locate and capture prey

With enormous appetites, they consume up to 1/2 their body weight in insects nightly. When winter's cold weather arrives, insect activity decreases greatly, so bats must adapt. Most hibernate for the winter, living off stored body fat. However, two of the species found on McKay Creek NWR migrate south, all the way to the Gulf Coast or Mexico!

There are 47 species of bats in the United States. Seven species have been documented on McKay Creek NWR. Let's meet 2 of them on the following pages:

Silver-haired Bats

The silver-haired bat is a medium-sized bat, weighing about 1/3 of an ounce (10 grams). Silver-haired bats inhabit conifer forests or riparian areas with trees. During the day, they roost in live trees or in large snags. Females with young roost in groups of 5 to 25, mostly in tree cavities. Males and females without young usually roost alone. Although some individual silver-haired bats may hibernate locally in winter, most migrate south. During migration, silver-haired bats are one of the species most commonly killed in wind-power generators.

Fun Facts:

  • Silver-haired bats mate in the fall.
  • Sperm is stored in the female’s body until spring.
  • Pregnancy lasts 50 to 60 days.
  • Two, sometimes only one pup, is born.
  • The young are nursed for about 36 days.
  • Pups can fly by three weeks of age.

Little Brown Bat

The little brown myotis (also called little brown bat) is one of the most common and widespread bats in the United States. This bat weighs about 1/4 of an ounce (8 grams). They use a wide variety of habitats, from conifer and hardwood forests, to forest edges, sites with cliffs, and urban structures. In rangelands, they prefer being near water. During the day, little brown bats roost in a wide variety of sites—buildings, rock crevices, caves, tree cavities, under tree bark. Females with young roost in groups of 10 to more than 1,000. Males and non-reproductive females roost alone or in small groups. Emerging aquatic insects are major prey of little brown bats, so they often forage over water. However, they forage in upland areas, as well.

Although they hibernate during winter, little brown bats may fly up to 500 miles between their summer and winter homes. Winter hibernacula are poorly known in the west, but include caves, abandoned mines and lava tubes. In the east, little brown bats concentrate at large hibernacula which can contain thousands of bats. However, the few hibernacula found in the Pacific Northwest have contained small groups of bats.

Little brown bats are highly susceptible to White-nose Syndrome, and in New England, over 90% of the little brown bats in many hibernacula have died from the disease.

Fun Facts:

  • Little brown bats mate in the fall.
  • Sperm is stored in the female's body until spring.
  • Females are pregnant for 50 to 60 days.
  • One pup is usually born; twins are rare.
  • Young can fly after three weeks.
  • Females may return to the same nursery roost year after year.
  • Most females do not breed until their second year.

Facts About Bats

Over 1,100 species exist world-wide

About 1/5 of the world's mammals are bats

Only mammal capable of powered flight

Bats live 15 to 20 years

Bats actually have good eyesight

The winter home of bats is a "hibernaculum"

Bat babies are called "pups"

Most species have only 1 pup/year

A group of female bats with young is a "nursery colony"