The lit­tle brown bat

Ontario Gardener Magazine - - CONTENTS - By Ta­nia Mof­fat

Bats take cen­tre stage ev­ery fall as All Hal­low’s Eve ap­proaches. Per­haps part of the rea­son for this is that many species such as the lit­tle brown bat gather in swarms from late Au­gust to Oc­to­ber to mate prior to set­tling in for a nice long win­ter’s nap.

If that is mak­ing you won­der how long the lit­tle brown bat’s ges­ta­tion pe­riod is, you will be sur­prised to find out that it is ac­tu­ally just 50 to 60 days. Fe­males, who will mate with more than one male, store sperm in their bod­ies through the win­ter de­lay­ing fer­til­iza­tion un­til they ovu­late in the spring. Usu­ally only one pup is born in late June or July. The young bat pup is weak and vul­ner­a­ble at birth, cling­ing to its mom’s mid­sec­tion but it will ma­ture quickly. By three weeks of age it is able to fly and is fully weaned at 26 days. Lit­tle brown bats have a strong at­tach­ment to their ma­ter­nity site and of­ten re­turn year af­ter year to the same lo­ca­tion. They have a rel­a­tively long life­span, liv­ing to ap­prox­i­mately 10 years of age in the wild. How­ever, one was logged as reach­ing an age of 34.

Of the 19 bat species found in Canada, the lit­tle brown bat has the largest dis­tri­bu­tion through­out the coun­try. They can be found in ev­ery prov­ince and ter­ri­tory but Nu­navut. They are also the species most of­ten sighted by hu­mans as they can be found re­sid­ing in build­ings, bat boxes and trees.

This species re­ally is lit­tle

The lit­tle brown bat is, well, brown and lit­tle. Their fur is a glossy brown that ranges from pale tan to a red­dish or dark brown with a lighter coloured belly. Ears and wings are tinted dark brown or black. Th­ese bats grow to reach only 7 to 14 grams and have a wing­span of 22 to 27 cen­time­tres. Other char­ac­ter­is­tics in­clude small ears and large back feet.

Bats are the only mam­mal ca­pa­ble of true flight and th­ese lit­tle guys can reach a top speed of 20 to 35 km/h. Many peo­ple be­lieve all bats are blind, but lit­tle brown bats have ex­cel­lent vi­sion which they use to lo­cate roosts and their win­ter hi­ber­nac­ula. Echolo­ca­tion is, how­ever, the main method used for hunt­ing. They emit high fre­quency calls and clicks that bounce off of ob­jects. This echo is then pro­cessed by the bat and is so finely tuned that they can avoid ob­sta­cles as fine as a hu­man hair. Op­por­tunis­tic feed­ers, they prey on small fly­ing in­sects – flies, mos­qui­tos, mayflies, bee­tles – and are su­perb hun­ters catch­ing an av­er­age of 1,000 in­sects per hour. Lit­tle brown bats eat in flight and will consume half of their body weight per night. Since they pre­fer in­sects with an aquatic lar­val state, yep that means mos­qui­toes; they pre­fer to roost near bod­ies of wa­ter. Now you may un­der- stand why many peo­ple are putting up bat houses!

Lit­tle brown bats sleep and groom them­selves dur­ing the day, emerg­ing at dusk. Keep­ing longer hours than some of the hearti­est of partiers, they are gone from sun­set to dawn, re­turn­ing home at 4 or 5 a.m.

A long win­ter’s nap

Bats leave their sum­mer roosts to mate and hi­ber­nate with fel­low mem­bers of their win­ter roost or hi­ber­nac­u­lum. Hi­ber­nac­ula can be lo­cated as far away as 1,000 km from their sum­mer homes and con­sists of caves or aban­doned mines which main­tain a high level of hu­mid­ity and sta­ble tem­per­a­ture that will re­main above freez­ing dur­ing the win­ter months. Hi­ber­na­tion is an ex­tremely im­por­tant time for them, and it is vi­tal that they are not dis­turbed dur­ing this process. The bat is able to slow its heart rate from 200 beats per minute to 20, along with its me­tab­o­lism and breath­ing. As most an­i­mals that hi­ber­nate, bats will

in­crease their weight by 30 per cent be­fore en­ter­ing a hi­ber­na­tion pe­riod that will last un­til mid-April for fe­males and midMay for males. Any dis­tur­bance dur­ing this pe­riod will cause them to waste their fat re­serves, leav­ing them with in­suf­fi­cient en­ergy to sur­vive win­ter and es­sen­tially starve to death.


Sadly the in­tro­duc­tion of a fun­gus called Geomyces de­struc­tans, in­tro­duced to North Amer­ica in 2006 has had grave ef­fects on the lit­tle brown bat. The fun­gus, likely brought to North Amer­ica ac­ci­dently from some­one ex­plor­ing Euro­pean caves where bat pop­u­la­tions are im­mune to it, has led to a dras­tic re­duc­tion in lit­tle brown bat pop­u­la­tions.

White nose syn­drome, or WNS, seems to af­fect the lit­tle brown bat the most. Dur­ing hi­ber­na­tion the fun­gus grows on the bat’s nose, wings and non-furred skin caus­ing them to wake dur­ing hi­ber­na­tion to groom, de­plet­ing their fat stores and lead­ing to star­va­tion. Most bats suc­cumb to the in­fec­tion af­ter two years.

Un­for­tu­nately, hi­ber­nac­ula con­tain ideal en­vi­ron­ments for the fun­gus and it flour­ishes. The dis­ease is quickly spread as bats gather for their fall mat­ing rit­ual and car­ried to new hi­ber­nac­ula. To date, eastern Canada has been the most heav­ily af­fected but bi­ol­o­gists es­ti­mate that most of Canada will be in­fected within 22 years. Since 2006 5.7 to 6.7 mil­lion lit­tle brown bats have died and they will likely be­come ex­tir­pated or ex­tinct in some ar­eas of Canada.

While there is no cure, a small per­cent­age of bats are sur­viv­ing and will hope­fully trans­fer their im­mu­nity to their young. How­ever, with only one pup per fam­ily per year born, nat­u­ral species re­cov­ery will be in­cred­i­bly slow, if even pos­si­ble. While sci­en­tists try to find a cure, the lit­tle brown bat is also ham­pered by habi­tat and hi­ber­nac­ula de­struc­tion. The Com­mit­tee on the Sta­tus of En­dan­gered Wildlife in Canada have as­sessed it as en­dan­gered – in an emer­gency des­ig­na­tion.

The lit­tle brown bat is en­dan­gered, in an emer­gency des­ig­na­tion.

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