Forecasting Europe’s (Very Specific) Rodent Problem
The potential current distribution of the coypu (Myocastor coypus) in Europe and climate change induced shifts in the near future (2020) Schertler et al., NeoBiota, https://doi.org/10.3897/neobiota.58.33118
For all my talk on not immediately demonising alien species, there are a plethora of annoying little critters who the label ‘invasive’ was made for. This is the case with the Coypu, an annoying beaver-like rodent initially from South America who has since spread through other parts of the world, including large swathes of Europe.
The Coypu is a textbook invader – it reproduces quickly, and though individuals don’t stray far from rivers, as a species they are capable of expanding their range very quickly. They destabilise riverbanks through their burrowing, which can lead to severe ecological and economical damage.
They are, however, quite sensitive to temperature, and as such it’s important to know what the effects of climate change will have on their distribution. Today’s authors set out to come up with a habitat suitability map for the Coypu in light of the rise in temperature we’re expecting in the coming decades.
What They Did
The team aggregated records of European coypu presence from a wide range of scientific studies and observations, including the use of a bunch of GBIF data. They created five categories of presence to measure by, ranging from one presence recorded at one point in time to well-established populations that had been in an area for multiple generations.
To create a habitat suitability model though, you also need to know where a species isn’t. There are ways to get around this when using presence-only data, usually involving generating absences randomly. In this study’s case, the best results were given when these ‘absences’ were randomly generated throughout the entire extent of the study area. The occurrence data was then compared to a range of environmental variables, including several different temperature variables, local land cover, and local human activity.
Did You Know: Door Knockers
While the Coypu is well established in many European countries, there are a few in the north that it’s now starting to venture into. In these countries, the Coypu is part of a group known as ‘door-knocker’ species, which are threatening to enter a country as an invasive but (for the moment) are being kept at bay. Doorknockers can often be a source of tension between countries, as one country’s attitude to management of a particular invader may be particularly lax, resulting in easier access for the invader to bordering countries.
What They Found
46% of all presences throughout Europe showed signs of early establishment, and 10% of these showed evidence of long-term persistence of the Coypu. There were long-term occurrences in Italy, France, the Czech Republic, Germany and the Netherlands.
Temperature variables were the most influential, with habitat suitability increasing as temperature increased. As such, the predicted suitable habitat for the coypu expanded further north under climate change scenarios. Despite this, the predicted area of suitable habitat stayed the same, with conditions in southern Europe growing too warm for the Coypu.
One of the variables used here is nearby human activity, which brings to light a constant concern with this sort of data – that high presences near human settlements are often just a consequence of humans being more likely to observe a species there. Here, the authors tried to get around that by adjusting for spatial bias seen in all non-marine, non-flying small to mid-sized European mammals, figuring that the same recording biases would apply to the coypu. It’s not perfect, but it’s an interesting solution to a persistent problem (see our recent look at observation bias here).
The fact that the Coypu’s suitable habitat area might not grow doesn’t mean climate change won’t have a significant impact on European freshwater ecosystems. As the coypu dies out in its southern European habitats, those ecosystems might (BIG might) go back to their previous state, but the effects in northern Europe, where many freshwater ecosystems are already species-poor, may be severe.
The good news is that Coypu eradication is a possibility – the UK actually had a flourishing Coypu population, which was wiped out in the 80s. So a risk map like this could be a fantastic tool for concerned managers.
Sam Perrin is a freshwater ecologist currently completing his PhD at the Norwegian University of Science and Technology and dealing with his own rodent problem in the form of a guinea pig who thinks pooping on a laptop is acceptable behaviour. You can read more about Sam’s research on his Ecology for the Masses profile here, and follow him on Twitter @samperrinNTNU.