Bats! (or the nightlife of lower Geology Tour)

On the evening of May 7, we were sidetracked from our night climbing session for a little while by a group of bats (see Rob’s previous post “roadside geology tour revisited”) that was quite actively flying all around us. Their activity seemed to be focused in an area approximately 100 feet to the north of where we were climbing, so we wandered over and sure enough found the bats’ roost in an overhanging flake on a large boulder. Captivated as they whirled around our heads (we could even hear the whoosh of their wings moving through the air), Rob took photos while I recorded their echolocation calls on my bat detector. His images and my analysis of their calls from my detector confirmed that the bats we were seeing were Mexican free-tailed bats (Tadarida brasiliensis)!

Rob was able to get some rad images (despite the challenge of shooting fast-flying objects in the dark)! By the way, the best way to view all of these images is to click on them so that you can see them in full size and detail (note: the following 3 images have been cropped about 30%):

A close-up of a bat in flight approaching the roost boulder


You should never pick up or handle a bat (or any wild animal for that matter). This is for your safety and the bat’s safety. I work with bats (for almost 6 years) and have specific training, rabies inoculations, etc. If you come across a bat that might be sick or injured, please use gloves or some cloth to gently scoop it up and put it into some kind of container that will be secure but also allow it to breathe. You can then email the blog address at the right, or call any bat specialist/rehabilatator (info at the end of this post).

A bat and its shadow cast against the roost boulder

An even closer shot!

In this last shot, if you look closely you’ll see the “free tail” extending past the tail membrane (hence this species is grouped as one of the “free-tailed” bats). The anatomy of the wings is also clearly visible. A bat’s wings are its hands, with the humerus, forearm, and then the fingers spread out through the wing membrane… this arrangement gives them a lot of dexterity (though at the cost of speed) in flight; all the better to catch those pesky bugs for dinner! The little claws poking up at the top of each wing are its thumbs.

Investigating the roost flake... yes there are bats in there!

Below are snapshots of some of the bats’ echolocation calls from that evening represented in sonograms (graphed as frequency in kilohertz over time). This was done using some nifty bat acoustic analysis software I use for my bat work called Sonobat.

Part of a call sequence from a Mexican free-tailed bat

This sequence has two bats: the first call is from a myotis bat (probably California myotis), and the latter calls are from a Mexican free-tail

On the afternoon of May 18 we were cleaning some loose flakes from a sweet-looking overhanging crimp line (see Rob’s previous post “that seam, a bat, and more climbing”) when Rob suddenly said something about seeing a bat. At first I thought he had simply seen one fly away, but then I realized he was crouched over some debris from a flake that had hit the ground. Turns out that was where he was seeing the bat: on the ground amidst that debris. We were (or at least I know I was) mildly horrified that we might have just killed a bat, and I gently scooped the bat up to get a better look.

I carefully took a closer look at him and determined first that he was an adult male (if you’re wondering how I know, as some often do, it is quite obvious in bats to tell the boys from the girls) western pipistrelle (Parastrellus hesperus), aka canyon bat. These little guys (and girls) are the smallest bats in North America. Anyway, he wasn’t moving but I knew that could also be because he had been in torpor (similar to hibernation) since it was the middle of the day… as well as stunned by the physical impact of his little home suddenly shattering to pieces around him. I examined him closely and didn’t see any obvious physical trauma, but I was worried about internal injuries. While Rob ran back to the van to get another lens, the little bat and I hung out in the little alcove and I tried to gauge his condition. By the time Rob returned, which he did fairly quickly (no small feat since we were at the top of the formation), the bat had gotten alert and even a bit feisty!

The little male pipistrelle... just after being removed from the debris

Another view of the little guy (you can really get a sense of his diminutive size next to my fingers)

Examining the wings for signs of injury

A closer look at the delicate fingers and wing membrane

Doing much better and raring to go!

This experience definitely yielded for us a valuable lesson, and we recommend that if you are cleaning a problem or route out in Joshua Tree (really, anywhere with exfoliating flakes), please take a moment and use a headlamp or flashlight to look behind any flakes that you are considering removing before pulling them off.

Bats can use crevices as small as 1/2 inch, so what seems like a small crevice behind a small flake is not necessarily too small for a bat! This bat was roosting behind a flake that measured approximately 3 or 4 by 5 inches, and was less than an inch reliefed from the face of the boulder. In the image below, you can see the crevice that we returned him to once he seemed to be doing well.

The pip after I returned him to a crevice behind another flake on the same boulder

He didn’t stay behind this flake long, though… he ended up flying off a short time later (I think he’d had enough harassment for the day). But we were reassured by the fact that he was flying well. I think he’s going to be fine! 🙂

One last shot of our little friend...

If you find a sick or injured bat, please use gloves or a cloth (never bare hands) to pick it up and put it into a secure yet breathable container lined with cloth then call a bat specialist/rehabilitator. You can use the following link to find one in your area:

~ by jillc on 2010/06/01.

One Response to “Bats! (or the nightlife of lower Geology Tour)”

  1. Wow great photos of the bats!! So lucky Jill was there to rescue the bat too!

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