Culling animals who “do not belong” may be a great misstep for conservationists

A comprehensive analysis published by scientists suggests that large herbivores should not be culled based on their place of origin. Animal traits appear to have an impact on ecosystems, but this does not relate to whether they are native.

Fallow Deer are not native to Scotland like Red and Roe deer are.
Fallow Deer are not native to Scotland like Red and Roe deer are.

Large herbivores have been introduced by humans to many regions of the world Conservation policies have sought to eliminate introduced herbivores and certain other non-native species, to these regions, even though many of these wild animals are considered threatened in their own home territories.

Herbivores known to have been culled include various species of deer, elk, bison, antelope and caribou. Large herbivores were previously thought to damage fragile plants and habitats, cutting down plant diversity, but these assumptions were based on research that did not have a proper comparison to native megafauna (as a study control).

This is why scientists from University of Oxford, Aarhus University and the Environmental Change Institute (ECI) did a broad analysis (meta-analysis study) of the impacts of large mammals in 221 studies across 6 continents of the world. They found that large herbivores' impacts on ecosystems did not relate to whether they were native or foreign in origin.

As a result of the meta-analysis, there is no evidence found to suggest that large herbivores who are native have different impacts on ecosystems than those that are not native.

Co-author of the study Dr Jeppe Kristensen (at the ECI) told Environmental Change Institute: “We do not find evidence to support the claim that native large herbivores have different impacts on ecosystems, specifically plant communities in this case, than their non-native counterparts. Therefore, we should study the ecological roles these animals - native or not - play in ecosystems rather than judge them based on their belonging."

What are contributing factors?

The recently published study by Kristensen and the co-authors in the Science journal concludes that culling animals just because they are not native to protect plant species can be flawed in practice. This kills millions of healthy wild animals, economically costing millions of dollars.

In fact, their analysis suggests that the animal's size and diet are more likely to be contributing factors to impacts on plant diversity in the ecosystem rather than whether the large herbivores are native or not.

Traits like those with selective diets show a stronger effect on vegetation state, such as grass feeders. This research indicates there should be more focus on animal traits, rather than their place of origin, which is often irrelevant. This could be vital information for conservation policy makers when making decisions that impact the species and ecologies of the world. It may come at a good time while criticism grows in the UK over government plans to expand the badger cull.

What else could be done?

Aside from improving policies, other strategies can be used to look after animal species and ecosystems in the world. The Guardian posted that there are humane alternatives to killing wild animals like wild boar, deer and grey squirrels. Researchers have said that contraceptives for animals can keep populations down humanely. This could look like a form of a vaccine int he form of an oral contraceptive. For a grey squirrel, for instance, it can be mixed with hazelnut spread and fed to the grey squirrels for controlling UK populations and benefiting red squirrels.

Even if eradication methods improve, we need more ecological studies to really understand whether the species assumed to be bad for the environment really are, looking holistically at multiple factors, just as Kristensen and his colleagues had done in their newly published meta-analysis.