Bringing Back the Wolverine

The Swedish government changed tactics at the end of the 20th century, giving incentives to farmers when there were successful wolverine reproductions in their area

The Swedish government changed tactics at the end of the 20th century, giving incentives to farmers when there were successful wolverine reproductions in their area (Image Credit: Vojtěch Zavadil, CC BY-SA 3.0)

Paying for an Endangered Predator Leads to Population Recovery (2015) Persson et al., Conservation Letters, https://doi.org/10.1111/conl.12171

The Crux

Humans have a long history of driving dangerous predators out of their backyard. Wolves and wolverines have been driven out of different parts of Europe at different points in history at the behest of farmers looking to protect their livelihood, and the Tasmanian Tiger was driven to extinction for the same reason. But with the realisation that these predators bring enormous ecosystem benefits, governments have been searching for ways to bring about co-existence between predators and locals.

This study looks at a scheme introduced by a Swedish government in 1996, where reindeer herders had previously been compensated for any wolverine related losses. The new scheme introduced compensation for successful wolverine reproductions in the area. Persson et al. decided to have a look at how it fared.

How it Works

The data used documented wolverine populations between 1996 and 2011 in an area in Northern Sweden close to the Norwegian border, where reindeer is the wolverine’s main prey, and illegal hunting their biggest danger. The data examines both the rates of reproduction and illegal killing before and after the introduction of the new scheme in 1996. Importantly, there was also a distinction made between male and female wolverine populations, in order to measure whether the population was worse affected by illegal hunting of the females than the males.

Did You Know: Trophic Cascades

Having top-level predators in an ecosystem can have a stabilising effect on the rest of the ecosystem. It ensures that herbivore populations are kept at regular levels, which in turn can influence vegetation, and then the biodiversity of all manner of species which call this vegetation home. The practice of a fluctuation in populations at one end of the food chain rippling through the rest of the food chain is known as a trophic cascade. A rise in wolverine populations would be a good example of a top-down trophic cascade, whereas a sudden increase in algae numbers in a lake would start a bottom-up cascade.

What They Found Out

The results on illegal hunting in Sweden conflicted with data from other surveys on wolverine, as it suggested that males were around twice as likely to be killed as females. Yet reports from North America and Norway showed no significant difference between males and females, a discrepancy we’ll touch on later. The number of registered reproductions doubled after the introduction of the new scheme, and five years after the scheme was implemented the population growth rate increased. This is especially impressive considering the proximity of the Norwegian border means that some members of the population are killed in Norway.

Whilst there are conservation measures in Sweden, the wolverine is actively hunted just across the border, in Norway

Whilst there are conservation measures in Sweden, the wolverine is actively hunted just across the border, in Norway (Image Credit: NTNU Faculty of Natural Sciences, CC BY-SA 4.0)

Problems?

That discrepancy between other studies is the big one, really. Wolverine population growth rates are very sensitive to increased killings of females, so if this study is incorrect, and the chance of illegal killing of males and females is the same, then the population growth rate may not be positive since 1996. However the statistical analysis was as conclusive as you can get for such a study, so instead of questioning these results, I think a more optimistic approach would be a study comparing the difference in risk of mortality from hunting in areas where hunting is illegal and legal.

So What?

This is a fantastic sign for conservation of the wolverine. The implications are obvious – if you give farmers a tangible incentive to care about the local population, growth rates rise. However I can’t pretend this is a universal solution. Wolverines are a special case, as they’re by large a solitary predator. The reintroduction of wolves pose different problems, as their predatory behaviour can sometimes see them pick off entire herds.

However there are also positives to this situation. In this area, we have a carnivore whose diet is almost entirely livestock. There are many parts of the world where wolverines and other predators do not depend solely on one source of food, and programs like this may be even more effective in those regions. And the core message remains, that if you bring farmers and other affected citizens into the fold and make the benefits of conservation more direct, conservation always faces less resistance.

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