Traveling 125 miles under your own power might take a human a week a more to complete. For an endangered Ruppell’s vulture with an epic wingspan of roughly 8 feet, it’s a mere day trip.
Long Way to Go for a Meal
Carcasses are the major source of food for large vultures. Across Africa, the distribution and availability of carcasses changes from week to week and from year to year. For a vulture, where you dined yesterday is unlikely to be where you’ll dine next week.
Cattle, antelopes, and other large mammals that make up the bulk of vultures’ diet die or are killed in unpredictable places and at less than predictable times. Often small protected areas with few predators and prey cannot provide the food needed to sustain a 15-pound bird. Therefore, to survive only by feeding on carrion, as most species of vultures do, you need to be an aerial nomad, able to traverse large areas on a near daily basis to find food.
So vultures are constantly on the move.
Keeping Up With the Ruppell’s
We recently tracked three Ruppell’s vultures in northern Kenya. Their daily and seasonal movements would make even the most extreme fitness fanatics look like couch potatoes.
Using solar tracking devices attached via harness to the vulture’s back, we discovered that one young bird ranged 67,000 square miles over ten months. That’s roughly the size of the state of Oklahoma or the country of Cambodia—an area that is nearly 300 times larger than the home range of some elephants.
It was not unusual for this bird to be in central Kenya one day and then along the Ethiopian border a day or two later, nearly 375 miles away.
Map of Kenya showing movements of three Rüppell’s Vultures. Each color represents a different individual. In this map of Kenya showing movements of three Ruppell’s vultures, each color represents a different individual.
Riding atop thermals of rising hot air, vultures expend little energy in travelling over vast areas. Unfortunately, such efficient modes of travel are not available to those humans foolish enough to try and study them, and keeping tabs on the birds is a constant chore.
Traveling around northern Kenya is not for those easily intimidated—horrible roads and insecurity are constant companions. Conducting fieldwork under the security of a G3 rifle may seem a bit extreme until you realize that well-armed cattle rustlers and drunken strongmen lurk throughout the arid landscape.
The Pay Off
Our work has opened up a window into the lives of the fascinating Ruppell’s vultures.
We now know how far they are traveling, where they are foraging, and where they raise their families. We have also learned just how difficult it is to conserve vultures due to the vast areas and international boundaries that they cross.
Our journey to study and protect these birds undoubtedly still has many more twists and turns, but even as the landscape continues to become more fraught with dangers, we will remain a voice for nature’s most magnificent aerial nomads.