Measuring The Crippling Effects Of Hunting

Recreational hunting is widely used as a tool to “manage” wildlife populations. The social acceptance of this practice, however, depends in part on it being performed sustainably and adhering to some basic ethical principles. To ensure that hunting does not threaten the conservation status of populations and that the negative consequences such as crippling are limited, the effects of hunting must be continuously monitored.

This article suggests a new approach to the measurement of hunting’s negative effects on wildlife – “the crippling ratio” – and presents a case study of how crippling rate and ratio have changed in the Svalbard-breeding Pink-footed Geese population between 1992-2016. In fact, many waterbird populations are managed by means of recreational hunting, while the actual effect of hunting on these populations is subject to ongoing debate.

Specifically, the crippling of waterbirds due to hunting with shotguns has long been a focal point. Crippling is not only ethically problematic, but may also affect population dynamics due to mortality after suffering the injury. The three main reasons for crippling of waterbirds are that hunters: 1) shoot them at ranges too long to be accurate, 2) use suboptimal shotgun ammunition and shotguns, and 3) lack experience in shooting overflying waterbirds.

The Pink-footed Geese migrate from Norway to Denmark, The Netherlands and Belgium. And while they are protected in the Netherlands and Belgium, they are hunted in Denmark and Norway. To regulate the population size, adaptive management has been introduced as a part of the International Species Management Plan. The working group responsible decided that to secure societal accept of recreational hunting as a management tool, crippling of geese should be reduced.

To meet the objective, Denmark and Norway have organized campaigns as well as monitoring of crippling. To evaluate crippling rates among waterfowl species, individuals are usually caught either alive or dead (killed by something else than shotgun shooting) and x-rayed to identify shotgun pellets. The crippling rate is then measured as the percent of birds x-rayed with embedded pellets. But, due to this methods’ sensitivity to the proportion of the population being shot, this method is not useful for evaluating hunters’ ability to reduce crippling.

Therefore, the authors suggest a different method: to assess hunter performance while also considering changes in the hunting pressure of the population and in population size: crippling ratio = (crippling rate / “harvest” rate). Crippling rate is defined as “the proportion of birds with embedded shotgun pellets” divided by the total number of birds x-rayed. Harvest rate is defined as “the proportion of the population being shot” divided by the population size prior to hunting.

The authors distinguished between juvenile and adult birds, which is a useful method of assessing the cumulative effect of crippling versus annual fluctuations. However, while this method of monitoring crippling may be more appropriate than previous approaches, there are limitations. Specifically, there will always be some individuals who were wounded, but died shortly thereafter. They, of course, add to the total negative impact even if they can’t be accounted for.

The authors found that the crippling ratio of the Pink-footed geese have declined over the last 25 years, despite an increased number of individual geese killed. Moreover, levels of crippling before and after Denmark’s first awareness campaigns in 1997 indicate a positive effect of these efforts. The authors of this article therefore argue for the use of “crippling ratio” as an approach to evaluate shooting courses, awareness campaigns, and other initiatives to reduce wounding animals.

In other words, they suggest using the crippling ratio approach as a guiding instrument for policymaking on recreational hunting as a wildlife management tool. And lastly, this method allows for a direct assessment of at least some of hunting’s negative effects of wild animals. While many animal advocates oppose hunting altogether, such tools can be helpful to reduce suffering for some victims of hunting.