Opinion: When to hunt the rare

Last August, gray wolf populations in Idaho were returned to the protection of the Endangered Species Act after a trial hunting season from September 2009 to March 2010 resulted in the killing of 188 wolves. Across the Atlantic, Sweden conducted the first wolf hunt in 45 years, allowing hunters to kill 27 wolves in January 2010 out of a total population of around 200. Landowners perceive wolves as a major threat to livestock and the motivation for these hunts is to control growing wolf populations. Yet, wolf hunting is controversial as many populations are protected under environmental legislation. So when, if ever, is it appropriate to hunt rare species?

Image: Wikimedia commons, Gary Kramer

Humans have been hunting wildlife for millennia. Today, wildlife is hunted for food or other commercial products (e.g. fur or medicine), to limit negative impacts on human livelihoods, or for recreation. But such activities must be closely regulated to avoid putting the hunted species at risk.Indeed, there are many examples where over-hunting has contributed to the decline or extinction of species. These include well-documented cases such as the passenger pigeon in the United States and the Tasmanian tiger in Australia, both hunted to extinction in the early 20th century, and the Arabian oryx, which disappeared from the wild as a result of recreational hunting in the 1970s, but has since recovered owing to reintroductions from captive stock. Despite hunting being a major factor in the decline of many species, evidence exists that tightly regulated recreational hunting (e.g. "big game" hunting for trophies) of non-threatened populations can yield substantial economic benefits for local communities and generate revenue that can be used to improve wildlife management and conservation without threatening species persistence. The hunting of endangered species, however, is a much riskier operation, and there is no evidence to suggest that it can improve their conservation prospects. Regardless of a species' status, populations should never be harvested at a rate that is higher than the rate of population increase. Harvesting at the rate of population increase allows hunting to be conducted each year without affecting the yield of future harvests. However, an appropriate harvest limit must be adjusted downwards to leave a margin of error for factors other than hunting that can cause declines in population size (e.g. fluctuations in resource abundance or climate). When dealing with endangered species, this margin of error must be very high to avoid causing the species to spiral to extinction. Determining how many animals to kill each year should be based on fluctuations in population size and rate of increase, but this requires an annual census of the population -- a costly and time-consuming task. While setting such limits is popular, controlling harvesting effort (e.g. the number of hunters) is another way to manage hunting that can reduce the need for constant population monitoring. It also has the potential to be self-regulating -- that is, fewer animals will be encountered (and killed) when population density is low. However, census data and careful consideration are needed when establishing the most appropriate effort at the onset of a hunting program, especially when population size is small. While wildlife scientists can advise on the likely outcome of any given hunting strategy, the decision whether or not to hunt a particular animal is largely ethical and must consider social, cultural, environmental and economic consequences. Hunting for the purposes of controlling the impacts of species (as is the case with wolf hunting) must have clear objectives directly related to damage mitigation. For example, if the reason for hunting wolves is to reduce livestock losses, then comprehensive scientific evidence must demonstrate a clear link between wolf population size and attacks on livestock, and show that control efforts will reduce these attacks. Hunting any species based on perceived risk is scientifically indefensible, especially if that species is endangered. linkurl:Gary Luck;https://f1000.com/thefaculty/member/5467778464957864 is an associate professor at the Institute for Land, Water and Society at Charles Sturt University in Albury, NSW, Australia, and an F1000 member since 2004.
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