This article was published in Scientific American’s former blog network and reflects the views of the author, not necessarily those of Scientific American
After a few days spent settling in at the field station—getting oriented with the vehicle (read: learning to drive manual shift on the opposite side of the vehicle from what I’m used to, in a Land Rover on bouncy bush roads), gathering some supplies from town, and doing overall game planning, I finally made it out into the field yesterday.
I headed up to the northern part of Mpala with my field assistant, Simon (whose knowledge of this ecosystem is just astounding), to scout out places to set up my mesopredator trapping grid. We drove almost the entire length of the Mpala Research Conservancy (MRC), and it was wonderful to be out and about in the field at last.
When Simon and I finally got to my first sampling site (a 25 kilometer drive takes close to an hour on these roads), we headed out on foot to determine the best way to orient and structure the grid. A key component of trapping mammals is to make sure that trapping stations are close enough to one other to keep animals from slipping between them without noticing any bait, but not so close that you limit yourself to the home range of just one or a few individuals, and to keep the traps a standard distance from on another—they are most often arranged in rectangular grids. The rules can change depending upon the social structure of the target species and the questions you seek to answer with the data, of course, but those are the general guidelines for the type of abundance/diversity sampling that I’m doing.
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Simon and I decided to set up a grid starting along a nearby luga—the local term for a small stream channel that often only actually has water during the wet season and to extend outwards across the savanna from that. In case you are wondering what the terrain here looks like, here is a shot of the incipient trapping grid (with Simon telling me about the luga just off in the distance).
Unfortunately, our luga exploration was truncated when Simon noticed a large bull elephant (Loxodonta africana) lurking a few hundred meters away. Although many people think of carnivores as the main killers on the savannah, elephants and buffalo are actually the ones that people out here tend to be the most concerned about. Lone bulls are often thought to be especially dangerous.
Elephants (presumably both the African and Asian species) actually kill upwards of 500 people each year, and the Cape buffalo (Syncerus caffer) is commonly said to kill more hunters than any other species in Africa. Both elephants and buffalo are enormous, travel in large groups, are unbelievably quiet as they move through the bush, and have the unfortunate pairing of short tempers and sharp weapons on their skulls.
The rule around here is that if an elephant is occupying a spot at a given time, the elephant gets to keep that spot until he/she decides they’re ready to move on. So Simon and I hiked east, away from the elephant but not in a direction that would let it easily get between us and our vehicle. We kept scouting the farther portion of our planned grid, and spotted an Eastern Chanting Goshawk (Melierax poliopterus) on our way.
What makes a good trapping site for a mesopredator, anyway? As you can see in the picture, the acacia woodlands found in this area consist mostly of acacias or other small trees dispersed across relatively sparse ground, with bunches of vegetation crowded around the base. Those bunches of vegetation are ideal mesopredator trapping spots, because a trap can be wedged into the grasses to resemble a burrow.
This also keeps the animal from stealing bait out of the back of the trap and generally makes it feel less exposed as it enters the doorway. The vegetation provides essential shade from the sun—we don’t want any crispy mongoose on our hands. I will also be wrapping the traps in shade paper before setting them, but the vegetation itself does the best job of keeping things as cool as possible. (Just a note, the traps are opened in the evening and checked first thing in the morning, so no animals are ever left inside a trap in during heat of the day).
The site we scouted yesterday is to the far north of the MRC, meaning that the site gets relatively little rainfall (< 400 mm/year). This will be one of my “dry” treatment grids. East Africa will likely experiencemore frequent and intense droughts as global climate change progresses. Thus, the dry sampling areas in my study may be representative of what the environment will be like in the more southern—and historically wetter—portions of Laikipia in the near future.
Another hugely rewarding part of this week was that I finally laid eyes on one of my study animals! This afternoon I spotted two dwarf mongoose (Helogale parvula) in the grass not far from the station. These small herpestids are extremely wary critters, and they rarely stick around long once they detect that they’re being observed. Dwarf mongoose have a social structure that is actually very similar to that of the ever-popular meerkats (Suricata suricatta), and they also have a neat vigilance mutualism with hornbills.
The hornbills hang around while mongoose are foraging and eat some of the insects that the little mammals grub up, and in “exchange” they emit alarm calls when they see predators, warning other hornbills and mongoose alike that danger is near. I’m interested to see whether hornbill sightings are a good indicator of finding dwarf mongoose at a given locality in this ecosystem.
I will report back once we start getting the traps set—fingers crossed for lots of mesopredators in the traps and no elephants stepping on them!
Images: copyright by author.
Previously in this series: