National Geographic - USA (2021-12)

not one we’d recognize, without

the wildebeest.”

A

AS I DROVE across the

plains, even when I

saw no wildebeests,

I often spotted their

remains—clusters

of bleached ribs, disarticulated

vertebrae, and stark alabaster leg

bones—each identifiable by a

nearby skull adorned with the tell-

tale horns.

I’d heard that one of Sinclair’s

protégés, Grant Hopcraft, an ecol-

ogist at the University of Glasgow,

was studying wildebeest remains—

sort of a CSI: Serengeti. So I called

him up.

I’d assumed most of these were

kills, but Hopcraft discounted that

notion. “People think of wilde-

beests dying from lions, hyenas,

or crocodiles, things like that,” he

said. “But predators account for

only about 25 to 30 percent of the

deaths among adults.” The number

one cause of death? Starvation.

Hopcraft and his team study

wilde beest bones, especially

femurs, the large bones in the upper

hind legs. “One of the things we do

is look at the bone marrow content,”

he said, explaining that even after

death it still holds the animal’s last

reserve of fat.

If the fat content in the marrow

is depleted, it tells him that the ani-

mal had metabolized all the energy

stored in the layers of fat under its

skin and around its organs, even some of its muscle tissue,

and had finally dipped into the emergency reserves in its

bones. At that point, he said, “these animals are what we call

a carcass with a pulse.” A predator may have delivered the

death blow, but only because the animal already was weak-

ened by starvation.

Hopcraft’s team is also studying the hairs from a wildebeest’s

tail. The hairs, roughly a foot long, tell the story of the past year

and a half of the animal’s life. Scientists slice them into tiny

segments representing about two weeks’ growth each, then

analyze them for isotopes and hormones that reveal a wealth

of data about the individual. “Imagine the animal is writing

a diary every day,” Hopcraft said. “ ‘I’m pregnant. I’m hungry.

I’m stressed. This is where I’ve been eating. This is what I’ve

been eating.’ It’s telling you that information.”

And what do these wildebeest diaries reveal? The animals

are always desperately hungry, especially the females. “A

female wildebeest is on the edge of starvation almost its

entire life,” Hopcraft said. “And that’s because they never

stop reproducing.”

He explained that the females are either pregnant or nurs-

ing a calf year-round, and for four months, from June to Sep-

tember, they’re doing both, all while migrating, which puts

huge energy demands on their bodies. “That makes them

completely focused on consuming as much as possible of the

most nutritious grasses until they’re gone,” he said. Then they

have to immediately figure out where the rain is falling, hurry

three or four miles to the next available grazing, and start

eating, competing with the million other wildebeests doing

the exact same thing. “This is the engine of the migration.”

I was reminded of the wildebeest that Charlie had seen run

the Mara River gantlet twice in one day and asked Hopcraft

if hunger would prompt an animal to ignore such obvious

threats. “It could,” he said. “Avoiding predators shapes some

of their behaviors, but starvation is the dominant force.”

M

MANY YEARS AGO, I booked a budget safari out

of Nairobi, and in less than an hour we found

ourselves amid a herd of wildebeests, framed

against the city’s skyline. The air smelled of

DATE

DEC. 20 21

NATIONAL GEOGRAPHIC

WELCOME TO EARTH

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NO. 6 8

STORY

THE UNLIKELY KING