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OCH BLOG

Bats of Orange County, CA: Part 2

Updated: Mar 18

Welcome back to the 2nd part of our 2-part series on Bats in Orange County. To view the previous article check out OCH’s website. In our last conversation about bats, we introduced how many bat species there are here in Orange County and debunked some of their common myths. Here we will discuss the three most common bats in Orange County which are the Yuma Myotis, Mexican Free-Tailed Bats, and the Big Brown Bats.


Yuma Myotis

top view of Yuma Myotis Bat resting in cave. Notice the light sandy fur and narrow ears. Photo by Dan Neubaum

Yuma Myotis (Myotis yumanensis) bats are small-sized bats (averaging about 24cm in wingspan and are smaller than the palm of your hand) that live for about nine years and are known by their sandy-colored fur and dark ears, nose, and wings. These bats show the popular bat behavior of staying in caves and hanging upside down that everybody thinks of when they look at a bat. Bats hang upside down because their biological characteristics make it necessary for them to sleep in this fashion. A bat actually cannot launch itself into flight from the ground like birds can, so instead they drop down from their sleeping place allowing them to take flight. They can sometimes roost (which means a place where bats settle or congregate for rest or sleep) in caves or mines, but due to human development, their favorite places to live are underneath bridges and buildings. Originally, they roost in hollowed-out trees, but when humans started to develop further, they no longer had hollowed-out trees to nurse/roost in.

Frontal view of Yuma Myotis Bat outside of the cave. Photo by Kirk Navo

Sometimes, bachelor Yuma Myotis bats reside on cliffs, but that is a rarer sight. These bats forage insects found over the water in forested areas where there is an abundant source of water. This is getting harder for them to find, because homes and buildings are being constructed, leaving their homes in ruin. The lack of Riparian habitat is forcing them to move to more densely populated cities for food and ultimately threatens their survival.



Mexican Free-Tailed Bats

Full body view of Mexican Free-tailed bat. This bat ranges in colors of brown and has larger ears than the other two species. Photo by Janet Hurley

Mexican Free-tailed bats (Tadarida brasiliensis) are medium in size (30cm - 35cm in wingspan and about as big as the palm of your hand) and have reddish/darker brown fur and black ears, lips, and wings. A cool thing about these guys is that their tails are actually longer than their tail membranes, which some say contribute to their flight speed (see picture below for reference). These bats roost in caves and abandoned buildings near the water. The water attracts the

Face view of Mexican Free-tailed bat. Notice the longer snout and broader ears.

insects they like to eat and provides a constant source of water as well. These bats can have a colony size of up to 20 million and can eat about 250 tons of moths per night! The younger bats normally sleep on the higher points of the cave because it's warmer, while the adults normally reside on the lower side. They have a lifespan of approximately 18 years, weigh about half an ounce, which is pretty light, and they are one of the fastest flying bat species, going up to 60 miles an hour. Mexican free-tailed bats are not endangered, however, with freshwater sources becoming more scarce, they are starting to find other places to live, like attics of homes.

Reference picture of Mexican Free-Tailed bat. Take a look at the tail. Photo by Sheri Amsel

Big Brown Bats

Frontal view of Big Brown Bat. It is the darkest of the two species. This one lost its roost in the winter (it was saved). Photo by Karl Krueger

Big Brown bats (Eptesicus fuscus) are larger in size (32.5cm to 40cm in wingspan and are about as big as your average phone). They are normally light to dark brown in color and have black ears, mouths, and wings. Their ears are a lot shorter than the other two featured bats, their mouths are broader, and their tails do not have fur. They like to roost in buildings, churches, athletic stadiums, and in the cavities of trees (mainly pine, oak, and beech). They love to eat beetles, however, any flying insect is fair game. These bats can consume their body weight with any and all kinds of beetles. Due to their consumption of these bugs, these bats are considered essential to our environment to help control the insect population and were named one of America’s most beneficial animals (NPS). Big Brown bats can live up to 20 or more years and their colonies normally hold up to 300 individuals. Encroaching human populations are threatening Big Brown bats and forcing them to move out of the forests and heavily wooded areas and into buildings and other man-made structures. This doesn’t hurt the humans, however, it does hurt the bats because humans do perceive them as dangerous and, therefore, remove/relocate or kill them.

Full body view of Big Brown Bat. These guys a larger than the other two species and have no fur on their tails. Photo by Michael Durham

The three common bat species we see in Orange County are harmless. They help control our insect population and normally stay out of our way. However, with human encroachment and habitat modification, these bats are forced to move away from their habitat and end up dying of starvation or getting killed.


There are ways to help the bat colonies thrive. We can start by looking at them as backyard guardians, instead of calling an exterminator. By allowing them to take care of our gardens by eating the insects that threaten our plants, we are feeding the bats and controlling our insect problem at the same time. The best thing we can do is to become educated and share our knowledge with the public about bats, how they are a beneficial part of our ecosystems, and pose no threat to humans. By reading this article you have taken the first step in this process. OC Habitats raises awareness of endangered/threatened species and habitats around Orange County. To learn more on how to get involved please visit https://www.ochabitats.org/getinvolved

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