Surfin’ Safari, 17 August 2010
By Keith L. Bildstein, Ph.D., Sarkis Acopian Director of Conservation Science,
Hawk Mountain Sanctuary, on his recent visit to East Africa
More than a million wildebeests, together with hundreds of thousands of zebras and gazelles, represent a lot of meat on the hoof. Indeed, if you work the numbers–and I have–the edible portions of the wildebeests alone add up to almost a billion MacDonald’s Big Macs.
Not surprisingly ungulate herds of this magnitude attract the attention of lots of scavengers and predators, and I had timed my visit to East Africa earlier this month to coincide with the herd’s passage through the Masai Mara National Reserve of southwestern Kenya. The idea was to arrive at the peak of vulture numbers in the reserve and help Princeton University graduate student Corinne Kendall place Hawk-Mountain-sponsored tracking devices on a number of them to track their movements inside and outside of the Mara and other protected areas in Kenya and Tanzania.
I had readied myself by bringing a new trap to help catch the White-backed, Ruppell’s, and Lappet-faced Vultures we were after, and a pair of sturdy leather gloves to handle them safely. What I was not prepared for was a vulture “Surfin’ Safari” that Corinne took me to almost as soon as I stepped off the plane at the reserve’s airstrip.
But before I talk about the vultures, a bit of ecological geography is in order.
The massive, or as some of my younger friends might say “gi-normous,” migrating herd of ungulates I was searching for traditionally follows a largely circular path that tracks the availability of lush, rainy-season grass across the vast Serengeti ecosystem, the northernmost extension of which is the Masai Mara reserve. The hoofed stock walks an average 10 kilometers (six miles) a day while feeding its way through the reserve, a migratory journey that includes crossing the crocodile-infested Mara River.
You probably have seen photos or videos of “the crossing.” Thousands of fitfully frightened wildebeest, none wanting to be the first to jump into the river, until one of them–pushed by those behind—falls in, and then the mad rush begins, egg-beater-like hooves churning the river’s water into foam as the frightened mass hastens to the other side. Although a few fall victim to the crocs, most of the animals make it, albeit shaken and bruised, to the other side. This year, however, conditions were such that more wildebeests drowned at the crossing than were eaten, and a macabre scene of bloated and soon-to-be bloated carcasses greeted me at the river’s edge when Corinne took me to “the crossing” for a look.
YES this bird's head is under water!
Now back to the “surfin safari.”
The vultures of East Africa are built to scavenge carrion on land. Sometimes they feed alone. Most often, however, they do so in frenzied groups of dozens of individuals, each aggressively vying for a front row position at the feast. Floating carcasses, as well as those wedged among the river’s rocky bottom, present a challenge for vultures, whose swimming abilities are limited.
The first is that most semi-submerged carcasses offer little in the way of points of entry for the birds. The eyes, mouths, and rear ends, the places that vultures normally use as break-in points, are below the waterline and largely out of reach.
Let's go surfin now, everybody's learning how...
The second is that the carcasses are wet and slippery, making it difficult for the vultures to gain purchase while attempting to break through the tough hides that are exposed.
In most cases the exposed parts of the carcasses were only large enough for one or, at best, two vultures to work at a time, with each bird performing a delicate balancing act of trying to avoid falling into the river or being bumped from the carcass by another vulture, while at the same time working feverishly to break through the animal’s hide and get at the food inside. The accompanying photographs tell the story best.
...come on a safari with me
The White-backed and Ruppell’s Vultures feeding in the river looked like novice surfers, unable to hang 5 (or 4 in their case), let alone 10, while trying to get a decent meal. That said, the tantalizing feast was just too good to pass up for
the birds, and on several days Corinne counted well over 100 hungry vultures lining the river’s edge, waiting for their chance at a piece of the action. Although the hundreds of tourists that visited “the crossing” came to see the croc-wildebeest carnage, what many got to see were the antics dozens of resourceful and persistent if largely ill-prepared vultures, trying to go where few avian scavengers had gone before.
Just when I thought I had seen it all, events like this come along and I realize there is still very much to learn.
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