While enjoying a late evening walk along the edge of a pond in Ireland, you stop to watch several small brown bats zip to and fro over the water. One of the bats veers off course, flying rapidly towards you and snatches a moth that looks nearly as big as the bat’s head right in front of your nose. As your marveling at the bats speed and agility, it disappears into the nearby tree line, the moth clutched between its tiny jaws.
You’ve just been lucky enough to see a whiskered bat (Myotis mystacinus) in action.
What is a Whiskered Bat?
The whiskered bat has the distinction of being the smallest of Europe’s native myotis bat species. The long brown fur that covers their back and shoulders gives them a shaggy appearance. Their underbelly is covered in somewhat shorter hair that’s greyish-white. Their wings, face, and triangular ears are darker than their fur and show a bit a pink. While they hibernate, the adults drop to about 4-5 grams which blooms to 8 grams after they wake and have fed for a few weeks.
The average wing span for the whiskered bats is about 25cm. The wings are shaped in such a way to allow the whiskered bat to fly quite quickly in long straight lines, but also to use a rapid fluttering motion when they’re maneuvering through trees or chasing a wily gnat. Whiskered bats are often observed gliding for long distances at a time.
Their Living Arrangements
Like most European bats, the whiskered bat is active in the summer and goes dormant during the winter months. In the summer time, they seek out small crevices in trees and behind cladding that they use as a roost. Females form maternity colonies that range from 20-60 bats, though in some special cases maternity colonies that approach a hundred bats have been found. No one is sure exactly why the bats occasionally form such large colonies, though it’s food supply and space are considered to be factors. Little is known about the roosting habits of the males, other than they’re more solitary and likely roost by themselves.
Whiskered bats have been observed sharing a roost with other species, including:
- Natterer’s bats
- Various Pipistrelles
- Brown long-eared bats
Because whiskered bats are a bit hardier than other species and do a better job withstanding cooler periods, they tend to gather near the front of both roosting sites and hibernaculums. They also emerge from the hibernaculums a few weeks earlier than the others.
It’s not uncommon for whiskered bats to set up a roost in older abandoned buildings, and if they can find a building that’s near the ideal hunting ground, the species will move in, happily settling into crevices, under eaves, or moving into the attics.
Unlike other types of bats that stay loyal to a single roost site, the whiskered bat likes to move around. As a rule, they change their location every fortnight or so. There are two suspected reasons for the location change. One, the bats may be following a food supply. Two, it’s possible that the species moves in an attempt to avoid predators that might use large piles of guano to help locate the roost and destroy a colony. In the case of large colonies, chiropterologists have noticed that while the colony itself might stay in one place, it’s not unusual for different mothers to abandon one maternity colony and start roosting with another colony. Again, no one is sure why this happens.
When winter approaches, whiskered bats seek out caves and old mine shafts with a winter internal temp of between 2 – 8 degrees Celsius.
Caring for Whiskered Bat Pups
Female whiskered bats reach sexual maturity at about fifteen months old. The mating season takes place in the autumn, just before the bats enter the winter hibernaculum. The sperm is stored within the female while she hibernates and used to fertilize her egg when she wakes up the following spring. The females generally give birth sometime during June or July indicating that the gestation period is two or three months. Although twins occasionally happen, as a rule, the mother only births a single pup, which is weaned at about six weeks of age, the point that it’s able to both fly and forage on its own.
Whiskered Bat Spotting
The single best way to spot a colony of whiskered bats, is by locating a nice spot that’s damp, such as a shallow pond, and close to a wooded area. The combination of the trees and the water not only provides the perfect breeding ground for the soft bodied insects that make up the whiskered bat’s diet, including moths, mayflies, and gnats. Find a nice spot to sit and settle in. If there’s a nearby colony of whiskered bats, they’ll start to appear as the sunsets and stay active for about the next thirty minutes as they eat their fill of available insects. When the whiskered bat first emerges, their flight pattern keeps them low to the ground, where they fly exhibit a nice level style of flying. Later in the night, they’ll take to the tree canopy to hunt.
While Whiskered bats capture most of their prey in mid-flight, if they spot a spider or moth sitting on a leaf or branch, the bat will swoop over and snatch the bug right of the plant.
Whiskered bats don’t like traveling long distances so they seek out roosts that are right on top of their hunting grounds.
A recent study suggested that Derwent Valley is favored by whiskered bats.
Remember, if you’re going out bat watching, you must sit quietly and do nothing to disturb the bats. Human disruption can have a devastating impact on the colony and even the overall bat population.
Final Bits of Interesting Information
The life span of the whiskered bat is considerably shorter than that of the Brandt’s bat, which they’re commonly mistaken for. While Brandt’s bats (which are frequently mistaken for whiskered bats and vice versa) can reach their forty-first birthday, making them the oldest living mammal, ounce-per-ounce, in the world, whiskered bats only live until their mid-twenties. That being said, the average life span of the whiskered bat is about four years.
The biggest threats the whiskered bat population faces is roost destruction, via dismantlement, renovation, or the use of chemical repellants. Pesticides used for agriculture is another problem. At this point, getting a fix on this bat which has a range that extends across most of Europe isn’t easy, but it’s believed that they’re status is vulnerable. As such, International and European legislation is in place to help provide the whiskered bats with some protection.
Wiffen, Tina. “Whiskered Bat.” Natural History Society of Northumbria. Web. Accessed 1 November 2017. http://www.nhsn.ncl.ac.uk/interests/mammals/mammals-north-east/whiskered-bat/
“Whiskered Bat.” Conserve Ireland. Web. Accessed 1 November 2017. http://conserveireland.com/mammals/whiskered_bat.php
“Whiskered Bat: Pictures and Facts.” The Website of Everything. Web. Accessed 1 November 2017. http://thewebsiteofeverything.com/animals/mammals/Chiroptera/Vespertilionidae/Myotis/Myotis-mystacinus.html