As costs rise and constraints tighten, they become less selective in the manner predicted by an optimal stopping model (
). The analysis also recognizes that objectives (recreation, provision of meat, or deer population reduction) differ among hunters, and that such differences affect the hunters’ selections of deer prey. These findings should generalize qualitatively to hunters from other nations and of other game.
Hunters and Predators: Fundamental Differences
The article spurs the reader to ponder similarities and differences between hunters (hereafter, humans) and predators (hereafter, nonhumans). This commentary focuses on some significant differences between hunters and predators, and between their effects on their prey populations.
Diekert et al. (
1) observe that large carnivores, which are the natural predators in many wildlife populations, are now well below equilibrium levels in many industrial countries, and that hunters provide the predominant preying control on wildlife populations. They observe, as well, that hunters, by their selectivity and ability to kill at far above natural rates, produce far different effects on prey species than would their natural predators.
However, there is a counterbalance to hunters’ outsized killing capability. Humans can impose regulations on themselves (e.g., catch limits, prohibitions on taking animals of a certain size or gender, hunting seasons) and can establish and adhere to social norms. The response to such limitations is the focus of Diekert et al. (
1).
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Most carnivores hunt to survive; they adjust their behaviors depending on their needs and on the availability of prey. Predatory animals have highly variable behaviors both within and among species. Lions appear lazy; they mostly sleep and rest because they can afford to do so. Snakes can be much more infrequent hunters; some eat only every 6 mo.
Shrews are near-constant hunters; a few hours without eating can be fatal. Humans are in the tiny minority of species that often hunt recreationally, although our domesticated pets, dogs and particularly cats, also often kill their prey with little need for consumption.
Hunters have powers not available to predators, as mentioned; they can constrain their hunting behaviors through regulations and social norms (
3). The behavior of predators, by contrast, is regulated by natural forces. Where humans are not significant participants, coevolved predator–prey populations produce equilibria.
The equilibria may wander, and some populations move in cycles (
4). In boreal forests, the lynx–snowshoe hare cycle, with some other predators participating, lasts roughly a decade and is an extreme example, with populations exploding and collapsing (
5).
Not surprisingly, lynx, just like Norwegian deer hunters, move on to less favored targets when faced with the constraint of a collapse in the hare population.
Lynx, however, cannot long sustain themselves on secondary prey, and their population subsequently collapses, with emigration and losses to reproductive capability contributing.
Humans and Species Extinctions
No endangered species regulation constrains predators. However, there is virtually no known case where native predators have driven a prey species to extinction in a setting where humans played little or no role. Humans, by contrast, despite their regulatory tools, have contributed to innumerable extinctions. Humans can disrupt equilibrium patterns through their often outsized hunting capabilities, their habitat destruction, and their introductions of invasive species.
The lamented extinction of the once-multitudinous passenger pigeons is one example. Human activity greatly reduced their breeding grounds. However, the decisive exterminating factor was that those pigeons traveled in vast flocks, making them easy for humans to hunt even when their numbers dwindled (
6). Alas, the human fervor for passenger pigeons did not give the pigeons time to evolve safer travel procedures.