Saving large carnivores, but losing the apex predator?

A top predator that must constantly look over its shoulder for fear of human hunters, may not be a top predator any more.

Humans have probably been hunting big, scary predators for as long as we have been human, and for the obvious reasons: They are big. They are scary. And they are competition. The fear goes deep in our culture— the Big Bad Wolf was appearing in folk tales in the early middle ages. When I spent a little time on foot in lion habitat a few years ago, the fear felt even more deeply rooted, down somewhere in my gut. Hunting helps restore our precious illusion of control.

Even today, and even among people who may privately loathe the practice, trophy hunting of top predators can seem like a useful tool. The theory is that trophy fees—$10,000 for a lion, say—help pay to protect habitat and keep out poachers. These fees can also provide economic benefits to local communities. In theory, that increases tolerance among people who still live with large, dangerous animals outside their garden gates. Hunting some species may thus serve as the means to increase their numbers— killing predators in order to save them.

But a new study in the journal Biological Conservation asks whether what’s actually happening is the opposite: These methods may be saving large carnivores numerically, but altering their role as apex predators. A top predator that must constantly “look over its shoulder” for fear of human hunters, Andrés Ordiz and his co-authors suggest, may not be a top predator any more. And the effects of that subtle shift can reverberate through entire ecosystems.

As hunters tend to know too well, even white-tailed deer or Canada geese know what to do and where to avoid when hunting season starts. It’s the same for predators, according to the new study: Brown bears tend to shift their daily foraging and resting routines when human hunters arrive. So do lions. Wolves may actually relocate their breeding sites.

These animals’ natural ecological function as predators is to instill “the landscape of fear” in their prey. But they become victims of that landscape instead, spending more time and energy being vigilant, and less out hunting. That means they may not be as effective at controlling numbers of prey species like moose or elk, according to Ordiz and his co-authors. And that can lead in turn to overgrazing and a cascade of other effects on the habitat.

Over the long-term, persistent hunting may also make the predators themselves less big and bad. The long history of hunting and persecution in Europe may be one reason, the study suggests, that European brown bears are not nearly as fierce as grizzlies in North America, though they are the same species, Ursus arctos. “Long-term, human-caused selection may explain the reduced aggression of brown bears towards people, their nocturnal behavior, and their higher investment in reproduction,” the authors write.

When I reached him by phone at the Norwegian University of Life Sciences, Ordiz said that hunters’ preference for large male trophies can have dramatic and destructive social effects, too. When a big brown bear is shot, for instance, infanticide increases over the next two years as other males move in to court the female.

The same thing happens with lions, Craig Packer of the University of Minnesota’s Lion Research Center told me several years ago, when I interviewed him about his research in Tanzania. A young male may take the place of a hunting victim long enough to begin a new litter, said Packer, who is not connected to the study. That new father then needs to stick around to protect those cubs for another two years. But a lot of younger males lack the moxie to hold off challengers. Social upheaval often ensues, with one male after another fathering cubs, but faltering as their protector, and none of the litters ever reaching maturity.

The new paper does not advocate a hunting ban. Controlled, licensed hunting of predators may still be a better alternative than leaving a habitat open to poachers, said Ordiz. (He also noted that his two co-authors have at times been hunters, though of prey species, not predators.) Instead, the paper urges conservationists to start thinking beyond mere predator numbers, to larger ecological effects.

The authors also make recommendations for managing large predators more thoughtfully. Among them: Establish core areas or large-carnivore reserves where predators can be predators, without fear of hunting. In places where hunting is allowed, limit it by space and season to minimize the ecological effects. And end or limit trophy hunting based on traits like the lion’s mane or the Kodiak bear’s size.

These traits—status symbols, social dominance, size, and a little raw ferocity—are the very things that enable these animals to function as big, scary predators in the first place.

Source: http://www.takepart.com/article/2013/10/25/surprising-reason-hunting-wolves-and-bears-can-damage-habitats

Dibujo

Reference: Ordiz, A., Bischof, R. & Swenson,J.  Saving large carnivores, but losing the apex predator? Biological Conservation 168 (2013) 128–133

Some general management recommendations arise from our current understanding of large carnivore ecology. We recognize that it will often be difficult to implement them and that they must be adjusted for species-specific and regional contexts. Nevertheless, we include these recommendations to highlight aspects of large carnivore management that managers should consider.

1. Given the role of large carnivores in ecosystem functioning, establish core areas or large-carnivore reserves within large landscapes where human hunting is excluded.

2. Human hunting of ungulates can help control them numerically, especially in areas lacking natural predators, but hunting does not replace the indirect effects of natural predation (see above). In places where large carnivore hunting is deemed necessary, limit hunting in space and time to allow natural interactions and their ecological impacts, at least in large protected, less human-dominated areas.

3. Prevent or limit trophy hunting of large carnivores when based on traits that are linked with their performance as apex predators (such as physical size, age or dominance).

4. Set higher thresholds and use greater selectivity when targeting ‘‘problem’’ animals. Targeting animals of certain sex and age limits may be feasible for some large felids with conspicuous physical characteristics (e.g. Whitman et al., 2004, see Section 5), but field determination of sex or age for wolves or bears during hunting situations is usually unrealistic. When possible, limited removal of young (subprime) or transient animals would be better than removal of prime, dominant resident individuals, which often have disproportional ecological effects.

5. Show considerable care when targeting individuals in breeding packs. Alternatively, avoid interfering with the social structure of group-living carnivores by targeting solitary individuals rather than members of a group (see Brainerd et al., 2008).

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