KNOWLEDGE BASE

In this article, researchers report on attempts to work out how beaver dams influence ecosystems downstream. They looked at 12 beaver ponds over two years, one very wet and the other very dry. They found a number of impacts but none of them consistent, depending not only on the size of the dam but also the size of the pond and water levels more broadly. The authors note that the knowledge gathered about human-made lakes and ponds is of limited use when trying to understand beaver ponds.

This study explores the evolutionary history of beavers by studying the genes of both living beaver species. The scientists found that beavers are closely related to scaly-tailed squirrels, who may have diverged from other rodents around 54 million years ago (mya). The divergence between North American and Eurasian beavers probably occurred over 7 mya, possibly due to migration from Eurasia to North America. Finally, they find that the last common ancestor of all the Eurasian beaver populations probably lived much earlier than thought, around 210,000 years ago.

The study in the French Ardennes region compared the ecological needs of three aquatic rodents: the invasive coypu and muskrat, and the protected European beaver. Coypus and muskrats were found in various habitats while beavers preferred wider waterways with specific woody plants. The findings suggest potential settlement areas for each species, but more data for beavers is needed for conclusive management decisions.

As part of the 5-year Scottish Beaver Trial, interim monitoring was carried out to understand the impacts of beavers on hydrology, biodiversity, and other factors. This study reported on field observations from 2010 and showed that beavers had had minimal impact on the river habitat. Beavers were mainly active in the lochs and had few impacts on streams. The report notes that future surveys will thus focus on changes in standing water habitats.

Rapid industrialisation in Alberta, Canada, around the turn of the millenium has changed the types of habitat available, leading to an increase in deer populations and the wolf populations that prey on them. This has raised wolf encounters with caribou, which previously were able to stay away from wolves more effectively, contributing to declines in caribou. Beavers also became a more important food source for wolves during this time. This fascinating text describes in detail how industrialisation impacted predator-prey dynamics in this region and set out some implications for caribou conservation.