Walk the Line

Walk the Line Nerdese

Click to see bolded terms.

It is 5:15. I shove my feet into my rubber boots and then meet the guide at the top of the hill in camp. We double-check everything, wiping the sleep from our eyes. GPS unit? Compass? Lemur book? Pen? I grab water and two power bars. He grabs his kiso (machete). We hike out, going up the hill leading to camera station seven. And up. And up. My glasses fog up. We make it to station seven, blast past. I’m sweating like a stuck pig. We hear birds, we hear the rush of the stream. And up, and up, we go. My legs are burning. I think of how good I’ll look in yoga pants. And then I remember that I hate yoga pants. So I think of cheeseburgers. We get to station ten. It’s 6:00. We’ve hiked 1km already.

We haven’t even started the lemur transect. We just made it to the start.

Few researchers work in northeastern Madagascar. Due to this lack of research, there aren’t many estimates of lemur density in Makira, despite Makira being home to a large number of threatened and rare lemurs. We are interested in lemurs, not only for themselves, but because fossa and the other carnivores likely prey upon them. To estimate lemur density, our team has walked lemur transects at each site, while the camera traps ran, except for Lokaitra.

Lemur transects are line transects where we look for lemurs. In a perfect world, line transects are supposed to follow a straight line. In the world of Makira, line transects follow winding trails, and you had better be thankful that there are actually trails to follow.

Thanks to Zach for this figure.

Thanks to Zach for this figure.

Typically, these transects are 2km in length, with flagging every 25m. Zach Farris originally had three transects at each of his sites; I intend to step up survey effort with four. These transects are walked at the very least five times during the day (5:00-9:00; diurnal) and five times during the night (17:00-20:00; nocturnal). This allows for ten surveys for each transect. With four transects, that makes for a total of a minimum of 40 lemur surveys.

We try for more, because more data is always better than less data (research rule #1). But there are constraints.

  1. A transect can’t be surveyed more than once every day. This means that we can’t run two diurnal surveys on one transect the same day. Why not? Because, for example, if we see white-fronted brown lemurs during one survey and then white-fronted brown lemurs during the second survey, there is a possibility that those observations aren’t independent. This could lead to overestimating white-fronted brown lemur density. However, a diurnal and a nocturnal on the same transect during the same day is okay, because we tend to see different types of species on diurnals than on nocturnals (and with our newly implemented “informal” transects, even observations of the same species can be used).
  2. Do not survey in the rain! This is not just for our comfort (though it is nice to stay dry when it is pouring down), but for the simple fact that it is rather hard to see or hear lemurs when you are literally drowning in rain. This rule, by itself, probably throws away half of our opportunities to run lemur transects. Recall that we are in the armpit of Madagascar and Madagascar doesn’t believe in deodorant.

While we are on the transect, we walk slowly and gaze about us, listening and watching for the lemurs among us. At night, we use headlamps to catch lemur eye-shine. When we see a lemur, we note the following bits of data:

  • Time of observation
  • Species
  • Flag number
  • Number of animals in the group
  • Height (m) or how high the animal is in the canopy
  • Distance (m) or how far the animal is from the transect
  • Compass bearing
  • GPS location (UTM X/Y coordinates)
  • Elevation (m)
  • How we detected the animal (by sight or by sound)
  • Behavior of the animal
  • Habitat type that the observation took place in

And then we move onto the next lemur observation!

What happens when we do not observe lemurs? This happens a lot (too often). A survey without observations is in itself data, especially if compared to former years. If, way back when, there were few surveys without lemur observations, and as the years go by, there are more and more surveys without observations, that could mean, among other things, that lemur density is decreasing at the site.


Zach Farris, in his infinite wisdom, came up with an interesting idea that has led to a publication (now in the works). We have a camera grid filled with…cameras…that record when and where carnivores are on the landscape. We run lemur surveys on fixed transects that go through this grid and record when and where lemurs are on the landscape. Carnivores eat lemurs. What if we…gasp…mesh the two types of data together? A lemur observation within 200m of a camera station can be used as a lemur presence point, to be analyzed along with carnivore presence points. Are lemurs avoiding carnivores on the landscape?

It is ingenious use of data. Now, when we run our “formal” transects day and night, and catch lemur observations that we can’t use for density estimation, we can use them for another analysis. For example, if we glance back and notice a lemur we didn’t see, which is a big no-no in density estimation because you had originally not detected that lemur. Or, when we see white-fronted brown lemurs on a nocturnal when we had already run a diurnal on that transect and had seen white-fronted brown lemurs. Or, when we are just walking through the forests, checking cameras or exploring, and happen upon lemurs. All of these data points can now be used to look at the nature of interactions between lemurs and carnivores.

Yay for thinking outside the box!


We don’t like boxes (or short girls with cameras)!

Getting up early in the morning for Transect C or leaving the leech-less safety of camp to stumble around in the forest in the dark (or, as it is officially known, to run a nocturnal), you’ve walked the line and come out alive. But we’ve only started our dark, dark journey into the bowels of what will be the next two years of my life. You’ve seen how we collect the data; now what in the world are we going to do with it? Check out the next installment, How Many Fossa in Makira?, for the answers.

And if you are one of those people who thinks that your time spent at the breakfast table re-reading the nutrition content on your Cap’n Crunch is a fun time, click here!


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