Fieldwork Focus: Seeing red

For the first installment of my Fieldwork Focus series, I thought it would be appropriate to profile one of the most common species here in Alabama, the red bat (Lasiurus borealis). Despite being pretty easy to find, these are truly beautiful bats and I never get tired of catching them!

First up, how do you identify a red bat? Well, as the name implies, color is obviously a big giveaway. All red fur is not created equal, however. L. borealis shows marked sexual dimorphism in pelage color. Females tend to be much lighter in color, with white-tipped hairs that give them a frosted appearance. Males can be "frosty" sometimes as well, you do need to check the genitalia to verify the sex, but you can typically use fur color as a pretty good indicator. Here are a couple of shots showing the difference in male and female appearance:


Beyond the red color, there are a couple of other obvious features that can be used to identify L. borealis. One of my favorite things about this species is the "hairy armpits." The wing membrane along their upper arms is furred.


In addition to the "armpits" these are bats are much fuzzier overall than many other species. Their hair is fairly long, and they have a fully furred uropatagium (the membrane connecting their legs and tail) that can be used as a partial wrap to protect their body from chills.


Red bats range in size from 9-15 grams, and the average litter size is 3 pups (usually ranges from 2-5). The pups are weaned shortly after they learn to fly, at about four weeks of age. They are forest bats, living as solitary tree-dwellers as opposed to colonial cave roosters.

On a slightly more subjective note, like all bat species L. borealis has a distinctive personality, at least from my experience. They have tempers to match their fur: they are fiesty, and are like little bulldogs when they get a grip on something with their teeth, it'is really pretty comical (as long as you're wearing gloves, that is!). Standard procedure is to remove them from the mist net and put them in a "bat bag" overnight to process (measure, weigh, examine, etc) in full light the next morning, and reds will chitter and scold you from the bags for quite a while before going into torpor for the night. I think they may be a good example of the Napoleon complex, they are actually very delicate but act much bigger and badder than you'd expect from an animal that fits nicely into the palm of your hand.

We ended up catching about 50 of these bats in the two nights we netted last week! One interesting observation I thought warranted sharing is that the first couple of hours of netting tend to yield almost exclusively males. There are occasional exceptions, but in my experience the females don't tend to start hitting the nets until around 22:00 or so (we usually open the nets around 19:30). I've always thought this difference between the behavior of the sexes is pretty interesting, I need to do some more research to see if it's actually been tested/explained, or if it's just a trend in the areas/seasons I've worked in.

That's all for the reds, you can see more field biology pictures here, but stay tuned to the blog for more species features and fieldwork-related posts in the near future!


Note:
I took all of the photos on this post, (except the ones that I'm in, obviously) feel free to use them if you want to but I would really appreciate a photo credit if you post them anywhere, thanks!