KNOWLEDGE BASE

Two Eurasian beavers introduced to a wooded site in England profoundly changed the local ecosystem structure. By creating 13 dams, water storage increased and peak flow after rainfall decreased by 30%. Water leaving the site had lower suspended sediment, nitrogen, and phosphate levels but higher dissolved organic carbon.

This text describes a computer model which was used to estimate where beavers were likely to build dams across 40,000 km worth of streams in the USA. The model took into account seven different factors and very accurately predicted where beavers actually were! This can help scientists' to convert their understanding of how dams impact river systems from the individual-dam-scale to the landscape scale.

This paper tested the effectiveness of a programme to manage beaver populations in trout streams. By comparing managed streams to unmanaged streams, the paper concluded that the management programme had some impact on beaver populations. In one area, it led to a decrease in beaver population; in another, it led to a faster decrease. Adverse weather conditions affected all beaver populations.

This report assessed the risk of the North American beaver (Castor canadensis) becoming invasive in the European Union. It described the beavers' introduction to Finland in the 1930s as well as its its habitat preferences, ecological impact, and potential threats to public health. The study highlighted concerns about its spread in several EU countries. The report also noted that, given the species adaptability (with a native range from the arctic tundra to Mexico), climate change is unlikely to impact its ability to become invasive.

This study was one of the first to try to understand why mammals change mate, testing a variety of hypotheses. It found that, for beavers in Norway, mate change generally occurred in the seventh year of a partnership. The individual who stays often re-paired with a younger newcomer, but this change didn't improve reproductive success. It seemed that the mate change was forced either by the arrival of the newcomer or the disappearance (or death) of the beaver who left.