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Debate: Hunting ‘common’ species won’t mitigate epidemics

Badgers are hunted down as ‘harmful’ species. Pixabay, CC BY-SA

The ongoing catastrophes of climate change, biodiversity loss and the coronavirus pandemic show that politicians are resistant to objective information, especially when economic growth is at stake.

As the Covid-19 pandemic continues to unfold in many countries and our relations to animals are being debated more than ever, the practice of hunting is part of the heated debate.

According to a 2018 poll in France, 84% of those interviewed stated that they disapproved of hunting, even as authorities and nonprofit organisations often face strong pressure from hunters’ lobbies. Such organisations may benefit from local politics, and the claim by hunters that that culling “common” game species can help maintain ecological balance, prevent damage the environment and even reduce the spread of diseases.

Invisible “common” species

Species often described as “common” include weasels, martens, polecats, foxes, rook ravens, black crows, magpies, jays and starlings, all of which were previously termed as harmful. While the term has changed, the consequences remain.

In fact, most people have never or only rarely seen such “common” species, especially mammals that avoid humans or are nocturnal. One notable example is the badger, which can be hunted in ways that strongly diverge from any idealised vision of what “hunting” looks like.

Fox in Chartreuse mountains of France. Brucyn/Wikimedia, CC BY-SA

In terms of natural balances, the numbers of specimens in a given population of any species fluctuates. Simply said, if there are enough food and water resources and habitat to live in, the population thrives. When these resources dwindle, the population size decreases. There are other factors as well, including predator-prey interactions, local climate, human-wildlife interactions, and pathogens.

The role of epidemics in regulating populations

In the case of pathogens, they can influence the population size of any species – that is why we humans fear them as well. Host-pathogen interactions are highly complex, but generally the spread of a pathogen depends on how infectious it is, the size of the population and the interactions between individuals.

This has been recently shown for an amphibian pathogen, Batrachochytrium salamandrivorans. Its transmission is dependent on the number of contacts between individuals, which is closely related to the density of a population. Generally, the higher the number of specimens, and the more reduced the living space of that population, the more likely it will be that the pathogen will spread.

Salamanders are susceptible to catch an amphibian pathogen, Batrachochytrium salamandrivorans. Pixabay, CC BY

If an infectious disease spreads rapidly, the most susceptible individuals will get infected, and this too varies depending on the nature of the pathogen itself – it may most affect younger, weaker or older individuals, whichever is the most susceptible. In an epidemic, individuals in a good condition can also become infected, but depending on their immune system and the disease itself, they may recover or die.

In short, infectious diseases can control the population size of common and not so common species. If culling keeps population size at low levels, however, an epidemic may not occur and therefore will not reduce the number of individuals.

Is culling really beneficial?

While the reduction in the populations of common species may be perceived as beneficial, it can in fact lead to a higher diversity of pathogens in a population – unlike pathogens, hunters do not target for weak individuals, but sometimes those that are most fit and in good health. In this way, hunting common species may actually increase disease risks for humans rather than decrease them.

A 2016 study conducted in the United Kingdom looked at the impact of culling wild badgers (Meles meles), which can serve as a host for the pathogen that causes cattle tuberculosis (Mycobacterium bovis).

Bovine tuberculosis explained.

The study confirmed that while large-scale badger culling reduced the incidence of confirmed cattle TB cases, its benefits were undermined by induced changes in badger behaviour. These changes in turn increased transmission among badgers and from badgers to cattle. The reason culling pushes badgers out of the culled areas, as well as expanding badger ranging in and around the areas where culls occurred. Thus, due to changes in badger behaviour in response to culling, such actions actually resulted in the opposite effect of what was desired.

Also missing in the debate precise information about the damages caused by badgers and other common species. In a 2018 text, the French Environmental Code states that many such species are “likely to cause damage”, but provides no further information. What we do know is that common species can play an important role in an ecosystem. This can include wild boars turning soil to find worms, fox catching mice, martens eating the eggs of other species, or all animals simply leaving behind faeces to nourish the soil.

Each species has its role to play in nature and due to the myriad interactions between species, humans still have significant difficulty in understanding the roles that animals play in their environment, even the most common ones.

Risks to animals and hunters

Female starling: this bird is often confused with any other ‘black bird’. Hedera.Baltica/Flickr, CC BY-NC-ND

Laws are not particular strict regarding who is allowed to take an animal’s life and the choices that they make, intended or otherwise. Risks to non-harmful species can easily occur – it’s easy to confuse any black bird for a blackbird.

Hunters themselves can also be at risk. With the Covid-19 pandemic and Ebola epidemic, we better understand how hunting animals can result in the shift of deadly pathogens to humans. While common European species harbour no such diseases, rabbits and foxes can be infected with rabies, which can affect humans.

What can we do?

In Luxembourg, hunting, trapping and killing foxes has been entirely stopped without any negative effect reported so far on the human or the wildlife populations. The same is true in the Swiss canton of Geneva. Measures other than culling have been used to mitigate damages caused by wild animals, including such as electric fences against wild boars or equipment that emits warning signals at the approach of deer. These examples show that approaches other than culling are possible.

Created in 2007 to help accelerate and share scientific knowledge on key societal issues, the AXA Research Fund has been supporting nearly 650 projects around the world conducted by researchers from 55 countries. To learn more, visit the site of the Axa Research Fund or follow on Twitter @AXAResearchFund

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