How would you feel to be an elk in wolf country?
Would you feel alert, jumpy, constantly on edge?
Or would you revel in the extensive vegetarian menu, oblivious to the constant threat of chase and death?
Predators can be inconvenient. We humans love to farm animals and harvest wildlife, often to the detriment of an area's ecology. We perceive as competition any animal that shares our view of animals as dinner and entertainment wrapped up in one. So we shoot predators, trap them, poison them, run them down with dogs, so that we can keep their quarry to ourselves.
Would you feel alert, jumpy, constantly on edge?
Or would you revel in the extensive vegetarian menu, oblivious to the constant threat of chase and death?
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Does this elk look nervous? (image: http://pixnio.com)
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| This one does. |
Predators can be inconvenient. We humans love to farm animals and harvest wildlife, often to the detriment of an area's ecology. We perceive as competition any animal that shares our view of animals as dinner and entertainment wrapped up in one. So we shoot predators, trap them, poison them, run them down with dogs, so that we can keep their quarry to ourselves.
But do wild, native predators really influence prey populations that much?
The classic example of a predator-prey relationship is the rise and fall of the snowshoe hare and Canadian lynx. Lynx populations grow fat and healthy on a bloodbath of hare. Hare grow scarce and become hard to find, so lynx die off or leave the area in search of more cute stuff to kill. With the populations of their tyrannical oppressors diminished, the hare populations grow again and the fluffy little guys rejoice - until the lynx catch on, return, and begin the purge again.
The pattern shown by the hare and lynx populations is wonderful. Hare reproduction is hugely affected by stress, but ultimately, directly and indirectly, it is predation that affects their populations. This is such a neat, orderly relationship of boom and bust in population size, but sadly such a beautiful pattern is rarely seen in natural systems. Most wild animal populations fluctuate depending on the seasons, food, predators, the weather, and of course human influences.
Predators are important parts of ecosystems, but they are not always massively influential on prey populations. Humans tend to think of a predator as in charge of its domain, lording it over the other animals by casting a shadow of fear over them. But ecosystems are far more complicated than that.
Another lovely story about predator-prey relationships takes place in Yellowstone National Park, where wolves were eradicated by humans by the mid-1900s, and reintroduced in 1995. As the wolves began preying on elk, the elk became nervous or dead and withdrew from browsing on trees in exposed areas, including willow trees, that they had previously been devastating. The willows grew thick and lush, tempting beavers to come and eat them and use them to build complicated feats of engineering on the rivers. The flow of the rivers slowed, the rivers widened, and more habitat was created for creatures that love slow, wide rivers.
This story was so popular that it was shared all over the web, and even made it into mainstream science media and lectures at my university. Unfortunately, subsequent research has poured vinegar on the pancakes of narrativity, and found that the real situation is much more complicated than that. In fact, new research at the University of Stirling found little evidence that wolf presence affects elk behaviour at all. Some elk changed where they browsed at different times of the day if wolves were plentiful in the area, but less than 10% of the elk studied modified their usual behaviour even once due to the presence of wolves.
This is great for the elk - more power to them! They should not let fear control their lives. But it's not so good for those of us who like nice, clear, logical examples of ecological interactions. Ecology is a pain, because it's often so fluffy, random and vague that it's hard to pin down the effects that species have on each other. This also means that the principles applied to one ecosystem may not necessarily be applied in any other ecosystem.
Predator-prey relationships are not always straightforward, and in real life, prey has more to worry about than predation. That's why conserving ecosystems as a whole is really important - we still don't understand all the interactions that go on between the components of the ecosystem, even in well-studied areas such as Yellowstone National Park.
Another lovely story about predator-prey relationships takes place in Yellowstone National Park, where wolves were eradicated by humans by the mid-1900s, and reintroduced in 1995. As the wolves began preying on elk, the elk became nervous or dead and withdrew from browsing on trees in exposed areas, including willow trees, that they had previously been devastating. The willows grew thick and lush, tempting beavers to come and eat them and use them to build complicated feats of engineering on the rivers. The flow of the rivers slowed, the rivers widened, and more habitat was created for creatures that love slow, wide rivers.
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| An example of a wolf. |
This story was so popular that it was shared all over the web, and even made it into mainstream science media and lectures at my university. Unfortunately, subsequent research has poured vinegar on the pancakes of narrativity, and found that the real situation is much more complicated than that. In fact, new research at the University of Stirling found little evidence that wolf presence affects elk behaviour at all. Some elk changed where they browsed at different times of the day if wolves were plentiful in the area, but less than 10% of the elk studied modified their usual behaviour even once due to the presence of wolves.
This is great for the elk - more power to them! They should not let fear control their lives. But it's not so good for those of us who like nice, clear, logical examples of ecological interactions. Ecology is a pain, because it's often so fluffy, random and vague that it's hard to pin down the effects that species have on each other. This also means that the principles applied to one ecosystem may not necessarily be applied in any other ecosystem.
Predator-prey relationships are not always straightforward, and in real life, prey has more to worry about than predation. That's why conserving ecosystems as a whole is really important - we still don't understand all the interactions that go on between the components of the ecosystem, even in well-studied areas such as Yellowstone National Park.
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