Saving Stripes

Category: News | Date: Jul 20 2009 | By: savingstripes

Last month, between the 12^th and 18^th, we successfully collared 11 zebras. Five were Grevy’s and six were plains zebras. Last time we collared zebras, almost exactly two years ago, we had a hard time catching plains zebras, but this time, strangely, they were quite easy to capture. Maybe this was because the vet was able to shoot the tranquilizer dart from further away, or maybe we were just luckier this time.

In any case, the whole round of collaring went very smoothly. We didn’t even have to go very far, because there were plenty of zebras on the Mpala property. By now, though, many of those zebras have dispersed to neighboring properties – which is good, because it will tell us where they’ve gone and how far and wide an animal travels looking for food and water.

Typically, the collaring process goes like this: Once we’ve found a group of zebras, we pick the one we want to collar (any female, for Grevy’s zebras, since we’re more interested in their movements). Then the vet aims and shoots a tranquilizer dart (see the pink fluff on its end as it moves through the air).

 With a little luck, the dart hits the zebra, preferably in the rump or shoulder.

After 4-6 minutes, the zebra goes down. We immediately go to it and ensure that it’s gone down in a good position (flat on its side, and not in any thorn bushes). Then we start monitoring it – its body temperature, blood oxygen concentration, breathing and heart rate.

 If the zebra is getting hot, we pour some water on her so that she can cool down (the sedatives can interfere with her body’s natural temperature regulation).

As we are monitoring her, we are also doing all the other tasks: putting the collar on, taking a blood sample, taking a tissue sample, examining her teeth, and collecting some ticks from her (more on this later). By examining the teeth, we can learn approximately how old she is.

Once we have finished all of these tasks, the vet gives her a reverser drug. Within a minute or two, she gets up, takes a few wobbly steps, and runs off.

One interesting thing I noticed during the collaring is that plains zebras always seem to bray when they wake up from the tranquilizer. “Whoop-whoop, whoop-whoop,” they shout to their companions. This lets them find their harem quickly and rejoin the group.

Once, when a female woke up and brayed, the stallion came running over to retrieve her; it seemed like he was just as relieved as she was! See here how he comes to get her and herds her back to the rest of the harem.

The Grevy’s, in contrast, don’t seem to be so anxious about rejoining their group. It’s interesting because it’s exactly what you would expect, given that plains zebras have such a tight social structure while Grevy’s don’t.

The collars will store the GPS location of each zebra every hour, so that we can track where they zebra has gone and how much time it has spent in different areas. We also set the collars to collect more fine-grain data (GPS coordinates every 15 minutes) for three days of each month. Why did we do this? The fine-grain data will allow us to ask more subtle questions, like how much time do zebras appear to spend grazing (in one area) and when do they walk quickly to cover a lot of distance in a short time. For example, it might be that zebras move quickly through inhabited areas during the day to avoid people and cattle, but they might graze in those same areas during the night.

Some more technical specs: of the eleven collars we put out on zebras, ten were made by a Swedish company, while one was made locally (assembled from various parts made in Europe). We are testing the locally-made collar on one zebra and several lions (including the one I helped Alayne collar in March). If these collars work well, we’ll put out a bunch more on lions in this area. This will let us see how zebras move to avoid being eaten by lions, or what kind of habitat brings zebras and lions close together.

-Siva

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