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Cattle, wildlife: No real conflict?
Posted 22 September 2011
Animal wars
In Africa, elephants trample farms. Some traditional herders are prohibited from grazing their herds on land
occupied by tourist-magnets like lions, leopards, giraffes and gazelles.
ENLARGE
Photo courtesy Rob Pringle.
Wildlife and domestic livestock, like these zebras and
cattle near Kenya’s Maasai Mara Reserve, cohabit
rangeland ecosystems throughout many parts of Africa.
And buffalo, zebras and antelopes eat grass that could
feed cattle.
In the East African savannas, the interactions between
wildlife and the people whose livelihood depends on cows
and goats, are complicated, critical and contentious.
Grazing is about the only way to make a living in this hot,
dry land, but livestock and many wild herbivores eat
similar vegetation.
And so the competition is obvious: How can a cow eat forage that a zebra ate first?
The question answers itself, and so nobody studied the issue.
Not so obvious after all
But in other realms, ecologists have found that organisms that seem to compete may actually aid each other.
“We are just beginning to understand that the relationship between species is highly contextual,” says
Truman Young, a professor of plant sciences at the University of California at Davis, “and this interaction
includes competition and facilitation. Once, people thought if two species were similar, they always
competed, but years ago, it became clear that facilitation exists in certain situations.”
Young is senior author of new study showing that in Kenya’s highland savannas, competition is partly offset
by facilitation; although during the dry season wildlife steal food from the mouths of cattle, so to speak, the
situation is reversed during the wet season.
When the rains come, wild ungulates (mammals with hooves), particularly zebras, seem to benefit cattle by
eating fibrous, woody grasses and revealing the more delectable, higher-protein grasses beneath.
This gives cattle access to forage with more protein, and their wet-season weight gains nearly
counterbalance the dry-season losses inflicted by wildlife.
ENLARGE
Photo courtesy Ryan Lee Sensenig.
During the rainy season, cattle and zebra shared a lush pasture that sprouted after burning.
Well done
The study was performed during 2007 and 2008, on nine fenced plots, or “exclosures,” each 4 hectares in
size. The researchers placed four young, unbred females of an African breed called Boran on each plot for
16-week periods, and measured their eating habits and weight gain in three conditions:
Cattle only
Cattle plus medium-sized herbivores (at least 20 kilograms, including zebras, gazelles, elands and
African buffalo)
Cattle plus all herbivores, including the jumbo-sized elephants and giraffes
First author Wilfred Odadi, a postdoctoral researcher at Princeton University and the African
Wildlife Foundation, wrote us to explain that facilitation nearly equaled competition. “Wildlife-driven
depression of cattle weight gain in the dry season is 35 to 40 percent. In the wet season, cattle put
on weight faster by about the same percentage when they forage with wildlife.” The real-world
situation, he added, would “depend on the lengths and frequencies of dry and wet seasons.”
This was the first experimental evidence that wildlife and livestock are engaged in facilitation and
competition, Young says. “There is a basic-science excitement here. With this large-vertebrate system, we
have shown that you can actually sometimes have competition and sometimes facilitation.”
It’s possible that the 15-year history of experiments on the site has changed the vegetation enough to
weaken the results. But the continuous grazing of cattle kept the site’s vegetation similar to the surrounding
savanna, Young says. “If we had excluded all large herbivores, the rangeland would become very different,
and our inferences would be skewed. But because cattle are the dominant herbivores … the plots were not
that different. My belief is if we had started the exclosures last year, we would have gotten the same result.”
ENLARGE
In Eastern Serengeti, Tanzania, a Maasai herdsman tends his goats with a Thompson’s gazelle in the
background. Maasai herders were hired to tend cattle in the Odadi experiment.
What are the practical implications?
Killing wildlife, except for rogue animals, is illegal in Kenya, but it still happens, Odadi told us. “Because in
Kenya wildlife belongs to the state, and not to the land owner, some livestock keepers still show a negative
attitude towards wildlife because of perceived ‘detrimental’ effects on livestock including competition,
livestock depredation and disease transmission. Some people react by fencing off their properties to keep
wildlife away. There are also situations where water sources are fenced off by pastoralists to make them
inaccessible to wildlife. In extreme cases, wild animals are actually killed, albeit illegally.”
ENLARGE
The Why Files
Africa’s seasonally dry, grassland savannas
cover a large portion of the continent.
And so in a region with unreliable rainfall and few
resources, it’s good news for advocates of
biodiversity conservation that the competition
between domestic and wild ungulates, at least on
savannas, may be more apparent than real.
Good news for conservation
Indeed, large mammal ecologist Johan du Toit of
Utah State University, wrote in Science that the
new information should eventually “provide
managers with opportunities to capitalize on
facilitative interactions, intervene against
competitive ones, and enhance animal production
overall.”
Rangeland managers often mix native and nonnative plants, du Toit added. And after “bold
experimentation and a break from orthodoxy,” a
similar approach with animals could boost
production while conserving biodiversity.
Odadi says better knowledge of cattle-wildlife interactions could support short-term changes, such as
slaughtering or marketing livestock “at the end of the wet season, when they have recovered from
competition in the preceding dry season, and also to minimize competitive effects (by reducing densities) in
the next dry season.”
Conservationists in East Africa and elsewhere are seeking “to manage land for ecosystem biodiversity and
short-term extractive value,” says Young, “but it’s pretty hard to find good examples, other than assertions
about the profitability of ecotourism. We were able to show that wildlife and cattle have a complex interaction;
that wildlife is not uniformly bad for cattle, and that allows us to be a little more lenient toward wildlife.”
– David J. Tenenbaum
Terry Devitt, editor; S.V. Medaris, designer/illustrator; David J.
Tenenbaum, feature writer; Amy Toburen, content development
executive; Jenny Seifert, project assistant
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Tags: Africa, biodiversity, cattle, ecological research, Kenya, Truman Young, wildlife conservation, Wilfred
Odadi