KNOWLEDGE BASE

The types of trees beavers use for building lodges on the Loire River, France, are not well understood. Here, scientists studied which trees beavers use and how they cut them. Beavers prefer larger willow branches for the frame of their lodges, even if these trees aren't common in the area. They then use smaller branches from various other nearby trees to cover the lodge. Beavers often cut trees so that they fall into the water and are easier to transport. Please note, this resource is not open-access.

Tool use is rare in rodents and had never been linked to aggressive displays. This article reports on observations of 'stick display behaviour' in Eurasian beavers, where the beavers held a tool (most often a stick) in their mouth and waved it up and down, sometimes splashing the water. The article contains a video of the behaviour in the Electronic Supplementary Material section. This behaviour was mainly seen at territory borders, between rivals, and triggered increased aggression in the other. It likely serves as a territorial display.

This letter presents some of the challenges associated with beaver reintroductions. It highlights concerns with the Scottish reintroduction which included the lack of an exit plan if things go wrong as beavers can't be lethally dealt with. It specifically mentions Baltic countries' experiences, which warn of overpopulation leading to impacts on smallholders through flooding and loss of land.

This study aimed to work out how and why willow populations had changed over the 20th century in Yellowstone National Park, USA. The researchers propose that eliminating the wolf led to elk outcompeting the beavers. As beaver dams were no longer maintained, water levels reduced and rivers begun to dig deeper into the land in a process called incision. These two changes made it more challenging for willow to grow. This change in geology means that, even with wolf populations returning, it may not be easy to restore the previous ecosystem functions without addressing these underlying hydrological shifts.

This text proposes three hypotheses to explain the successful invasion of North American beavers across Tierra del Fuego, Chile. One is that they lack natural enemies, another is that there are available resources, and the third is that they create the conditions they need to survive. This last point is supported by the observation that beaver population density is higher where beavers have modified the habitat more. Please note, this paper is mostly written in Spanish.