KNOWLEDGE BASE

Evidence suggests that beavers were once native to California’s coast, including San Francisco Bay. This article reported on the analysis of a late 19th-century piece of rock art (petroglyph) which referred to a beaver lodge. The authors suggested that this may be the last record of beavers before their local extinction.

In this report, sightings of Eurasian beavers in Tuscany, Italy, were confirmed by the use of camera traps and genetic analysis of beaver hairs from the area. The researchers suggested that the beavers were likely released locally - and unofficially - given that a surviving natural population was very unlikely and the nearest zoo with beavers is over 100 km away. The text also included an account of the history of Eurasian beavers in Italy, ranging from Roman literature to modern legislation!

Both species of beaver create dams that alter water storage, sediment transport, and the chemistry of water courses. Their activities increase biodiversity, change aquatic and terrestrial ecosystems, and modify nutrient cycling. The extent of these complex effects depends on landscape context and the duration of beaver activity, amongst other factors. This text summarised the evidence around beavers' overall impacts on hydrology, biogeochemistry, and ecosystems - an ambitious endeavour, given the complexity involved! The text includes a variety of graphs, photos, and diagrams to help explain beavers' impacts.

Much of the research exploring Eurasian beavers' impacts on fish had focussed on beavers located in forested areas. However, in Russia, many beavers live in steppe (grassland) environments. Some had theorised that beavers' effects on fish in these areas may be less than in forests since beaver population density was lower, but this paper gathered real data to test that theory. The results showed that beaver-modified habitats in this environment supported lower fish diversity and biomass compared to beaver-free areas. However, the researchers suggested that long-term beaver population stability might have a more positive impact.

Following the revival of Sweden's beaver population over the course of the last 100 years or so, this study sought to survey the parasites hosted by beavers across the country. Scientists only found five types of parasites after testing 30 beavers from around the country, reflecting the low levels of infection found in the original Norwegian population. Higher levels of infection were found in beavers from southern Sweden where temperatures are warmer.