Category Archives: Science

Bats with red spots

During a 2008 trip to La Selva Biological Station in Costa Rica, I took a terrible photograph of some lesser sac-winged bats (Saccopteryx leptura) roosting on the underside of a tree.

Roosting bats covered with red dots

I kept the photograph because the bats seemed to sporting some strange red dots that were the color of giant red velvet or trombidium mites, and I was curious. But I looked online (for years) and for the life of me couldn’t find any reports of something that large on a bat in Costa Rica. All I succeeded in discovering was that quite a few smaller mites seem to be found on bats (Banks 1915; Klimpel and Mehlhorn 2013), with new species found all the time.

One person suggested that they might be chigger mites (Trombiculidae). Each spot, perhaps, would be composed of hundreds of mites feeding together. Chiggers feeding in a group isn’t rare, apparently. If you search for “trombiculidae aggregation” you’ll get lots of images of seething groups (e.g.) on all variety of animals. But it begs two questions. Why does each bat have only one clump, and of the same size.

UPDATE: After posting and sharing on Twitter, Sean McCann sent me a message asking whether my dots might be marking bands. He also sent a photograph (a good one) in which the locations of the bands exactly matched where my dots are in my photograph. So I contacted Dr Carlos de la Rosa, the Director at La Selva Biological Station, to see if anyone was banding bats at the time, and he responded that it was likely … and is checking to see exactly who. I’ll post an update if I hear back. 

UPDATE II: Dr de la Rosa spoke with Dr Martina Nagy, who claimed those bats as part of her research (as well as corrected my species identification; they are not rhinoceros bats). She even recognized the tree (“SOR 170 Sendero Oriental”). These individuals (two males, one female) had been banded by Dr Barbara Caspers. The tree eventually fell and then the bats disbanded to someplace else. 

It took me almost 10 years, but I’m glad I finally know what was going on. That photograph had really been bugging me. Thanks, everyone!

Shaving your legs to deter ticks

People shave their legs for a variety of reasons: to look younger, to look less like men, to show off tattoos, to show off muscle definition, to improve athletic performance (less drag, plus fools brain into thinking you’re going fast), to facilitate post-accident wound cleaning (cyclists), and because shaved legs induces a pleasurable sensory overload when wearing clothing. But can shaving also protect you from ticks?

Girl with shaven legs

I became curious this week after watching a tick crawl up my leg. This tick, in fact:

Male American dog tick (Dermacentor variabilis) crawling on human leg.

No experiments on this topic have been done, but I found three relevant snippets on the internet:

“One thing that helps is shaving your legs. Not a foolproof way but I would say it reduces them critters by 80%, maybe more. I noticed that when my wife and I were out and she had none, I had around 14 that day.” source

“As an experiment I shaved my legs before riding point to point at lbl with KRS and a few others. It was tick season. After 40+ miles of riding I had 1 tick on my sock. Along the way KRS pulled OVER 15 ticks. We rode the same route at the same pace. I’ve kept the hair off ever since.”  source

“I’d say its mostly impractical. Although, I know many trail runners (including myself sometimes in the summer) do it to prevent ticks from attaching.” source

It makes sense that shaving would deter ticks. The first is obvious: ticks can grip hair, so if you are hairless (and are wearing shorts, skirt, or kilt), they can’t climb as fast. The second is that you if you have hairless legs you can most likely better feel them crawling up your leg. I.e., all eight of their legs are touching your skin’s sensory array. The third is that when you remove all your leg hair you are removing a lot of sensory distractions caused by wind (experiment on swimmers) and thus you can zero in on things crawling on you. Indeed, all of these mechanisms might touch on why we evolved to be relatively hairless in the first place.

One experiment that needs to be done is to count the numbers of ticks on a group of people out for a walk, some of whom shave. But at least in the United States, that would break down to men versus women, and males smell worse than women and thus might attract more ticks, regardless of hirsuteness. And men are usually larger, so there’s the surface area thing that goes against us, too. So it would be far better to recruit a group of hairy-legged people and ask them to shave just one leg, then march around a field known to have ticks. An ideal group for this experiment might be a men’s swim team right before the season begins. I.e., they all have hairy legs but will likely shave them for the season … so they won’t care. Would be crazy photogenic and a great way to strengthen bonds between campus coaches and faculty. Plus great team-building exercise. Would get the college on the evening news I’m sure.

A simpler design might be to just have a motivated group of people (perhaps students in a field ecology course?) conduct tick races on shaved, unshaved legs. You just need to start them on the ankles and have participants hold still while the ticks make their ascents. That would be equally photogenic and fun, I think.

If somebody does go ahead and conducts this experiment — and if the effect is huge (my guess) — the next step would be to alert the folks at the CDC so they could add a shaving recommendation to their tick page. The reaction to that would be entertaining.

Conference poster full of tips for creating conference posters

In case you need a quick guide to making a conference poster, here’s a poster of poster tips. Just view click to enlarge, or display with a room projector and invite students to come up and read together. It’s also available as a PDF if you want to print an actual poster of it — which I highly recommend if you are assigning a poster project for your class. My full tips (and free templates) are at “Designing conference posters“.

Advice on designing scientific posters

This poster is a descendant of a document I created circa 1997 for my evolution students at Swarthmore College.