Predatory Life On The Savanna Is Complicated (Unless You’re A Lion)

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In a simple system, there’s a predator and its prey; the predator roams wherever the prey is found. Add in more predator and prey species, and where the predators live should be decided by what they eat. Real life, though, is not that simple. Just look at this new study published online by Ecology of four predator species in South Africa.

An international group of researchers studied an 85-square-kilometer, fenced-in region of South African savanna — the Karongwe Game Reserve. In this area there are four main predator species: lions, cheetahs, leopards, and wild dogs. These predators hunt 12 different ungulate species, mostly impala, blue wildebeest, waterbuck, Burchell’s zebra, warthog, and giraffe.

To figure out where the predators were going and what they were doing, many of the adults of each of the four species were outfitted with VHF transmitters during the study period of 2001 to 2005. The distributions of the prey species were determined by aerial surveys and sampling in the wet and dry seasons (respectively, November to March and April to October).

All that data was then combined. The patterns and interactions of the various species are complex, but there were definite patterns:

Lions: The big cats (above), as might be expected, are the dominant predators in this environment. That power gives them unrestricted access to pretty much anything they want. They go where the best and most vulnerable prey can be found and where they’ve got the best cover for hunting. They don’t worry about where other predator species are. Even the season doesn’t affect them much.

Leopards: These cats overlap in range with lions — the best prey is found where the lions live — but they avoid the much-bigger cats. They also avoid each other. In this area at least, the biggest killer of leopards is other leopards. And during the dry season, when it’s easier to see through parched vegetation and the risk of detection by other cats is higher, leopards find it safest to move towards the smaller wild dogs.

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Cheetahs: Like leopards, these spotted cats (above) are also smaller than lions, and it would be expected that they would also avoid the big cats. But, like the leopards, their range overlaps with the lions. And in the wet season, these cats tended to actually move towards locations where lions were recently roaming. The researchers theorize that cheetahs may be using other tactics to avoid lions, such as by choosing habitats, like woodlands, that the bigger cats don’t use, or being active when lions aren’t. Staying near the lions, and their high-quality prey, proved beneficial; some cheetahs were able to take down large prey like wildebeest instead of having to stick with smaller meals. But just because the cheetahs were comfortable venturing into lion territory doesn’t mean that they were entirely fearless; these cats generally stayed away from leopards.

Wild dogs: The African wild dogs — the smallest of the predators — tended to avoid all three of the cat species, but they behaved differently depending on the season. In dry times, when they could be more easily seen, the wild dogs stayed away from the other carnivores’ activity centers. In the wet season, though, when there was more cover available, they took a little more risk and only avoided areas where the other species had been recently. Constrained as they were by the movements of the other predators as well as the boundary fence they could not cross, the wild dogs had to settle for prey species they did not prefer.

The researchers’ take-away message from all these interactions is that for subordinate carnivores like the cheetahs, leopards, and wild dogs, competition with other predators can matter more than what they eat. Because if you have to eat an impala instead of a wildebeest, or even wait another day for a hearty meal, being hungry is better than getting mauled to death by another predator.

Images courtesy of flickr user Jean-Louis A

No Easy Solutions For Saving Africa’s Wildlife

elephantA sampling of recent stories from Africa:

Dozens of elephants were slaughtered in Chad in just a week. Then there was a study that estimated 62 percent of central Africa’s pachyderms were killed between 2002 and 2011. And a report that 80 percent of the water buffalo in the Serengeti have been lost to poaching, along with 2,000 elephants and nearly all the rhinos. The United Nations Environment Programme says that 22,218 great apes, more than half chimpanzees, have been killed since 2005.

In a rare spot of good news, six rare white rhinos were secretly transported to Botswana to escape rampant poaching in South Africa. But that’s just a drop in the bucket when two dozen rhinos can be killed in a week.

Thousands and thousands of iconic wildlife are killed each year in Africa, and I can’t help but think that the problem is getting worse.

There are plenty of suggestions for how to stop the tide: Legalize trade in rhino horn. Build fences around lion habitat. Slick ad campaigns and a multi-national anti-poaching force. But what strikes me about all these proposals and plans is that they don’t get to the heart of the problem — greed.

As long as the money to be made through the wildlife trade outweighs the risks and punishments, poaching will continue.

Those caught poaching animals or trafficking in their remains are often let off with little more than a slap on the wrist, usually just a fine. A Chinese ivory smuggler, for example, was fined all of $350 for a haul worth $2,500 before being set free. Punishment in the U.S. for these crimes can be more harsh — a father and son team of rhino horn smugglers faced a fine of up to $1 million in one case last year — but I do wonder how much of that was for tax evasion rather than wildlife trafficking. And though there are a few countries where poaching and smuggling can bring a sentence of jail time, convictions can be rare.

Calls for Google to remove ads for ivory are at least trying to get at the root of the problem. While there is a market for things like ivory and rhino horn and lion parts, there will be people willing to kill elephants and big cats and other amazing creatures.

But how do you fight a rumor that rhino horn will cure cancer? Or that lion bone will increase a man’s sex drive? That God wants to you wear ivory? That a chimp bone will make a child stronger?

Fences may help keep lions or elephants from straying into villages, but it won’t stop a determined man with a gun from trying to make a few thousand dollars. Legalizing trade in animal parts isn’t going to stop demand for them. Slick ad campaigns won’t deter someone who truly believes they’ve found a cure for the disease that’s killing them. And building up an army of anti-poaching forces can’t protect every animal on the continent, especially when there are still legal options (i.e., trophy hunting) for obtaining wildlife.

What we need, around the world, is better laws against the wildlife trade, better enforcement of these laws, and harsher punishments attached to wildlife crimes. And we should promote projects that give local people incentive to protect the wildlife around them, such as through ecotourism.

Because it’s only when we change the equation such that an elephant or a rhino or a lion is worth more alive than dead that the killing will stop.

Image of a poached elephant carcass in Cameroon in 2009, courtesy of flickr user USFWS Headquarters

An Uncertain Future For Vultures

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It can be difficult to feel sorry for a creature that lives by eating the dead. But vultures fill an important ecological niche, and removing them from the landscape can cause a cascade of changes with devastating consequences, as India has learned in recent years.

Vultures started disappearing from India during the 1990s. The cause, scientists later learned, was the painkiller, diclofenac. The drug is used to treat cattle in India (and elsewhere), but it’s toxic to vultures. When cattle die, the vultures eat the carcasses, get sick and also die. Vultures in India are disappearing faster than the dodo.

You might think that without the vultures to eat the carcasses of the dead, the bodies would just decay. But instead they’ve become a food source for rats and, worse, packs of feral dogs. Feral dogs are a growing problem in India, where they have attacked and killed children, and spread rabies and distemper, threatening a host of other species.

Now Africa could be facing the same problem, and hopes that vultures could be saved through the creation of protected areas have been dashed by a study in PLOS One that found that the birds roam farther than anyone suspected.

“We found that young vultures travel much further than we ever imagined to find food, sometimes moving more than 220 kilometers a day. Individuals moved through up to five countries over a period of 200 days, emphasizing the need for conservation collaboration among countries to protect this species,” study co-author Stephen Willis of Durham University in England said in a press release.

The reason vultures fly so far is that there’s just not enough food for them in the protected areas. Vultures prefer to eat animals that have died naturally, rather than compete with lions and other predators for their kills. The best place for a vulture to find a meal, then, is a pasture far from other carnivores. Sadly, though, the vultures don’t know that those pastures can contain some of the most deadly foods. And until people stop treating their cattle with the problem painkiller, the vulture populations will continue to decline.

Image Credit: Dr. Stephen Willis/Durham University