The Nature Writers of Texas

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Sunday, March 09, 2003


Naturally Texas
Studying Spotted Skunks Requires Technology and Money
Terry Maxwell, March 9, 2003, San Angelo Standard Times, © 2003

I want to visit with you today about the smallest species of skunk in our region, but I might end up with too little space to tell you anything. The problem is that I am drawn to introduce you to the modern world of wildlife research.

Finding out what we need to know about spotted skunks involves the use of battery-powered radio transmitter collars, a yagi directional antenna and radio receiver, GPS, GIS, UTMs, CALHOME, and LOCATE, among other sundry electronic doodad. And all that costs money before you ever fill up the tank and head to the field in your skunk clothes.

Two things we don't know about spotted skunks - among many things that we want to know - involve habitat use. How big are their territories and where do they den? The only way to get a definitive handle on that sort of understanding is to follow individuals - not an easy thing to do, but nonetheless we're going to do it. So, let's get started with your training.

We're going to catch skunks using two methods: live trapping with Tomahawk traps and hand-catching using the skunk corps. The Tomahawk traps are simple, humane cages with a trap door sprung by the skunk entering for a tasty morsel.

I described hand-catching for you a couple of weeks ago. Briefly again, you gather the students who live for this sort of thing - the skunk corps - and head to the brushland in a pickup truck at night. When a skunk is spot-lighted, it's a mad dash out of the truck and off into the night - you can join the chase if you want to as long as you've had your rabies shots. The object is to catch the animal, preferably without bodily injury to yourself or the skunk.

Upon capture, the skunk is returned to the truck and anesthetized with an injection of a carefully determined cocktail of sedatives. Someone in authority has the permit to possess these chemicals for wildlife research.

Once our spotted skunk is sufficiently groggy to handle, all participants gather around and contribute to the data collections: external parasites are combed from its fur; its general body condition is recorded; measurements - total length, and length of tail, ear, and hind foot - are taken; sex and reproductive condition are recorded - a female might be lactating, indicating young in a den; an ear tag with a unique identifying number is attached and so on.

Most critically, a collar with a battery-powered radio transmitter is carefully fitted to the skunk. For the western spotted skunk, we'll use a collar weighting 24 grams. That gives a functional battery life of two years.Uh-oh, someone points out that our skunk is waking, and I notice you backing up a little. C'mon now - a little courage. Well, our work is done on this little fellow, se we stand back while he comes out of his stupor. When released, we want him alert and able to take care of himself.

Before we leave the scene, we need to see if his radio is working. The radio receiver with its yagi directional antenna is fired up. Our graduate student in charge of the project - it's his graduate thesis research - slowly rotates the antennna until the signal is received. It works.

On future nights, we're going to pinpoint the locations of this skunk with our antenna and a GPS unit. A handheld global positioning system (GPS) device uses satellites to pinpoint the location. The skunk corps drives to established points of known location and uses the antenna to locate the direction of the skunk from the point. After repeating the procedure from at least one other fixed point, the data is fed into the computer program LOCATE. This program calculates the triangulation of directions and fixes the skunk's location.

You might be discouraged - I was - to find that the skunk locations are recorded in UTMs - universal transverse mercator units - not in latitude and longitude. It's a system of mapping developed by the U.S. Army in 1951. I could get really involved here in describing how it works, but suffice it to say that it uses a decimal grid system rather than one of degrees, minutes, and seconds. It's supposed to be more efficient - yeah.

Back in the lab at school, we're going to plot all the individually known skunk locations using a GIS - geographic information system - and then using the computer program CALHOME, determine home range size for each western spotted skunk we
caught.

Did you get all that? Well, guess what? I don't have any space left to talk about what we've learned about the animal. But I think we needed to go through this training exercise for you to develop a little savvy about the modern world of wildlife research. I'm sure you'll have to hear most of it again before you're comfortable with it, but for now let's just get our skunk clothes and running shoes. There's night work - still the best part - to be done.

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