KNOWLEDGE BASE

This text described how and why grassland bird populations in North America have declined, citing habitat loss and changes in ecological processes. Beavers, along with grazers like bison and prairie dogs, helped maintain open grasslands prior, but have suffered due to over-hunting. Understanding these natural processes was said to be crucial for informing bird conservation efforts, whether on natural habitats or on working lands like farms.

This paper compared skulls of 2 ancient beavers with those of modern beavers in Poland. It found that ancient beavers had notably larger skulls than modern beavers of the same age. This is precisely set out by measuring different parts of the skull, including a part called the sagittal crest. Tables 3 and 4 set out these results in comparison to modern beavers.

Castoreum extract is a natural substance derived from beaver scent glands. This article assembles the research on its toxicity as a food additive. Based on the limited current data, consuming castoreum extract at current levels is deemed safe. Its long-term use throughout history without reported adverse effects supports this conclusion. It is regarded as safe by regulatory bodies. Overall, using castoreum extract at current levels poses no safety concerns. Please note, this resource is not open-access.

Between 2002 and 2004, feces from 62 beavers in the USA were tested for certain parasite species using microscopy and genetic analysis. The study showed that 6.4% of the beavers, all young ones, had these parasites.

The return of beavers to a National Park in the USA has led to an 89% increase in wetland habitats between 1944 and 1997. Beavers had converted forested areas to open water and wetlands, benefiting pond-breeding amphibians by providing more breeding sites. Beavers initially favoured larger, lower sites, but later on, beaver sites were smaller and higher up the river. Many were abandoned, creating a diverse habitat mosaic. Please note, this resource is not open-access.