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Invisible Armies of the Night

John M. Regan

Ask yourself this – how many times have you actually seen a bat?  Most people would have to answer not many.  There’s an obvious reason for this, of course.  Bats are relatively small, dark colored, and tend to nighttime activities.  Small wonder we miss them so easily.  Behind this obscurity, however, lurks a surprising fact:  there are more bats on earth than any other species of mammal except one.  Nearly one thousand different species of them share this world with us.  Only rodents boast of greater numbers.

Bats belong to the order called Chiroptera, a derivative of the Greek term “hand wing.”  A very apropos name for these astonishing creatures whose most obvious physiological feature is its hand wing.  Thanks to this unique appendage bats are the only mammals capable of flying due to their own muscle power.  Other mammals like flying squirrels and some lemurs can glide but only bats actually flap their wings and create long distance flight - and bats are the only mammal to have ever developed the ability.  To date no fossil evidence has been found that indicates mammalian flight has ever existed before the appearance of bats. Bats also lay claim to having the smallest member of the mammal family – the recently discovered Kitti’s Hog Nosed bat of Thailand.  Sometimes called the Bumble Bee bat this little fellow was first described in 1974.  It is a little more than one inch long and weighs in at less than an ounce.  There are moths bigger than that!  This as opposed to the almost six foot wing span of the Flying Fox family of bats.

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Bats other distinctive talent is echolocation.  Well, of course, everyone knows that.  True.  But did you know that was not discovered until sometime in the 1930s and not really understood until the 1970s?  Although not uncommon in the wild world, echolocation is one of those things that seems very straightforward at first.  The animal emits a sound.  That sound bounces off an object and returns to the ear of the emitter.  From that the animal is able to determine the size and location of objects around it.  Yes, that is the principle of the thing.  But when several factors are considered the subject gets a bit more complicated.  The frequency of a sound that echo locates insects, for example, has to be far more precise than that required to determine the boundaries of a cave.  And how are shape and size deduced from sound alone?  A bat hunting insects must be able to produce a high frequency sound, and detect the resulting echo, from amidst the hundreds or even thousands of its companions.  Now that takes a special talent.

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As previously noted the echo locating abilities of bats are directly related to its preference for food.  Although nearly all species of bats have echolocation ability (there is one genus, Rousetta, in which it is lacking (Kunz and Pierson, 1994)) it is most critical for those species that hunt on the wing.  Walkers’ Mammals of the World, 6th Edition lists several basic types of bats:

·         Insectivorous  – the majority of species, they obtain insects for food while in flight

·         Fruit Eating  – these are the largest species, the “flying foxes”

·         Flower Eating  – as the name implies these bats eat pollen and nectar, and as such are tremendous pollinators

·         True Vampire  – despite their notoriety just three species of vampire bats exist

·         Carnivorous  – prey on other small mammals, frogs, etc.

·         Fish Eating  – as the name implies these bats catch and eat fish

A bat that must snag a moth out of mid-air while in flight is obviously much more dependent on echolocation than a fruit eating bat.  And here is where frequency comes into play.  High energy, high frequency sound is key to pinpointing an animal as small as an insect.  Lower sound waves suffice quite nicely for fruit or flowers. 

Bats produce these sounds through their mouth or nose.  The returning echo is, of course, received in their ears, sometimes aided by a special organ inside the ear called a tragus.    And this is what has given rise to the variety and downright bizarre appearance of many Chiropterans.  A fruit eating bat such as the large flying fox, has a dog like face that actually qualifies as endearing.  Compare this to the incredibly strange features of the leaf eared or fish eating bats.  No other mammal on earth can lay claim to that degree of weirdness. 

Bats are not blind, by the way.  Most have eyesight every bit as good as other mammals.  The myth of blindness is understandable, however, considering the Chiropteran affinity for nocturnal activities and dark places.   And they are not all black or brown, either.  There are actually a couple of species of white bats, some are even tri-colored or white spotted.  Despite a body size comparable to small rodents bats have a relatively long life, up to 30 years, with reports of 40 years.  But where rodents make up for their shorter life span by having numerous young, bats generally raise just one “pup” per year.  Twins are occasionally born. 

Bats have a world wide range, but do not live in altitudes above tree growth according to Walker.  Cold climates in general are well inhabited by them as are just about all tropical regions.  Some hibernate throughout winter or become torpid in colder weather, greatly reducing their heart rates.  But abundant water does not seem to be a determining factor.  The author of this article has personally seen hundreds of bats flying around some of the driest parts of southern Afghanistan.  Attracted by the moths and insects that hover around spotlights it is possible that these animals have travelled some distance, too, since there was no visible hiding places within sight. 

The United States is home to about 45 species.  Many range into Canada and as far north as Alaska.  According to the Peterson’s Guide (see references below) about five species of leaf nosed bats have a range that extends from tropical regions into southern Texas.  These chiropterans feed on fruit, flower nectar – and yes – blood.  But don’t expect to see vampire bats if you visit the Rio Gran.  The vast majority of our species are insect eaters beneficial to farmers and by extension all of us who depend on farm products. 

And about this business about bats and rabies.  Yes bats do occasionally carry rabies.  But you are much more likely to be bitten by some other rabid animal that a bat.  All mammals are capable of carrying the rabies virus.  (In fact, only mammals carry it.)  Raccoons are the most common carriers of the disease, but any animal acting strangely should be avoided.

Bats are utterly incredible animals.  Prove it to yourself.  Do some research in your local library or on the internet and see if you can find any other species of warm blooded creature that matches the order Chiroptera in variety, behavior, or appearance.  Bet you can’t.

Bats of the Northwest (Peterson’s Field Guide):

·         California Myotis             Myotis californicus

·         Western Small Footed Myotis   Myotis Ciliolabrum

·         Yuma Myotis                   Myotis yumanensis

·         Little Brown Myotis        Myotis lucifugus (throughout US and Canada into Alaska)

·         Long-Legged Myotis      Mytois volans

·         Long-Eared Myotis         Myotis evotis

·         Keen’s Myotis                 Myotis keeni

·         Fringed Myotis                Miotis thysanodes

·         Western Pipistrelle        Pipistrellus hesperus (throughout US and Canada into Alaska)

·         Silver-Haired Bat            Lasionycteris noctivgans

·         Big Brown Bat                Eptesicus fuscus (throughout North America)

·         Hoary Bat                        Laisurus cinereus (throughout North America)

·         Spotted Bat                     Euderma maculatum

·         Townsends Big Eared Bat             Corynorhinus townsendi

·         Pallid Bat                         Antrozous pallidus

NOTE:  This word “Myotis” that pops up so often in relation to bats is, according to the online Oxford Dictionaries, a modern Latin term derived from the Greed word mus, mus-mouse.  Apparently the intent of the word is to convey a description of “mouse like.” 


Walker’s Mammals of the World, volume 1, 6th Edition, 1999

Peterson’s Field Guide – Mammals of North America, 2006 Edition

Online References:

Bat Conservation International:


Bat Facts:






Bat Rescue:




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