KNOWLEDGE BASE

For this paper, researchers developed a computer model which assessed habitat connectivity in Italy and Iberia (Spain and Portugal). It found that the habitat around the places where beavers were currently found was well-connected, and that only a few man-made dams were likely going to impede their expansion. Therefore, the authors concluded that the beavers’ expansion was likely to continue, with this paper predicting in which directions it may do so.

In this article, the first case of naturally-occurring Borna disease (BD) in a free-ranging Eurasian beaver was reported. The infected beaver showed symptoms of weight loss, depression, and weakness. The beaver was euthanised humanely, and the text also reported on details of the post-mortem analysis, including the characterisation of the virus. Please note, this resource is not open-access.

This report assessed the risk of beaver translocations in England triggering different types of diseases and infectious hazards. The authors stated that the disease risk analysis should be repeated regularly as the available data on free-living beavers grows. This version of the exercise identified 96 hazards, including 28 which hadn't been evaluated before. These are hazards to the beavers themselves and neighbouring mammals such as humans. The report also set out measures which should be followed to manage these disease risks.

Toxoplasma gondii is a parasite which can cause a disease called toxoplasmosis in humans and for which rodents can be intermediate hosts. For public health reasons, therefore, it is worth knowing how much beavers are exposed to it. In Switzerland, scientists found that almost 50% of Eurasian beavers had antibodies to T. gondii, with heavier and more urban beavers more likely to have antibodies. This high number meant that beavers are exposed to, and can act as a host for, this parasite.

This thesis described the first ever investigation of how Eurasian beavers' dams affect brown trout in a British context. Results showed that, in this area of Scotland, a beaver-modified stream supported larger trout with more diverse ages compared to a control stream without beavers. Beaver dams did not hinder fish passage when there was lots of water but may cause delays in times of low flow. The study also highlighted how beaver dams can change the distribution of predators - in this case, the heron.