Differences in habitat use between the native Eurasian beaver and the invasive North American beaver in Finland

Abstract

Habitat requirements largely determine the distribution and abundance of a species. An invasive species can therefore threaten the survival of a native species, if the two species are similar in niche use. In Finland, the distribution of the invasive North American beaver (Castor canadensis) is approaching the range of the native Eurasian beaver (Castor fiber) possibly creating a threat for the latter. We compared the habitat use of the native and invasive beaver species in Finland in the main distribution of the species and within a smaller area where the species live in sympatry. We compared the used habitats (volume of birch and other deciduous trees and distance to agricultural and urban areas) at beaver lodges and at random locations in the available riparian habitat with (conditional) logistic regression models. Results indicated that the native beaver lodges were located closer to agriculture than those of the invasive beaver. The volume of birch was also slightly greater near the lodges of the native beaver than those of the invasive beaver. However, habitat use of both of the species seemed quite flexible, because the habitat near lodges did not differ much from the available habitat. We conclude that the probability that the North American beaver will invade the distribution area of the Eurasian beaver in Finland depends, at least partly, on the ability of the former to live in proximity to agricultural areas. However, methods other than those related to managing habitat quality may be the best approach to controlling the invasive species.

Low genetic polymorphism in the re-introduced Eurasian beaver (Castor fiber) population in Finland: implications for conservation

“…Despite the absence of North American beavers, the population of Eurasian beavers grew slowly. This might have been affected by other factors, such as poor habitat quality, as western Finland in primarily nonoptimal agricultural habitat (Alakoski et al 2019).…”

“…Although recent data indicates that in western Finland the Eurasian beaver population has been increasing in size (see also Kauhala and Karvinen 2018), interspecific competition with North American beavers may have limited the eastward dispersal of Eurasian beavers in the country (Alakoski et al 2019). However, evidences also suggest that the expansion of Eurasian beavers in Russian Karelia led to displacement of American beaver (Danilov et al 2011a).…”

“…We cannot, therefore, exclude the possibility that the difference in the competitive ability of Eurasian beavers in the two countries is due to, for example, different environments. Although the habitat requirements of the two species are similar, some differences exist (Alakoski et al 2019;Danilov et al 2011b).…”

“…The present distribution of the Eurasian beaver in Finland covers Satakunta, parts of the provinces of Pirkanmaa, Pohjanmaa, and Etelä-Pohjanmaa, as well as western Lapland and the NE corner of Varsinais-Suomi (Fig. 1), and the population seems to be spreading in western Finland (Kauhala and Karvinen 2018;Alakoski et al 2019). The North American beaver population increased and expanded much more rapidly than that of the native beaver and today occupies most of eastern and central Finland and some areas of northern Finland (Kauhala and Karvinen 2018).…”

Differential Resource Use between Native and Introduced Gray Squirrels

“…Competition between bull trout ( Salvelinus confluentus ) and introduced brook trout ( S. fontinalis ), for example, is concentrated in stream reaches with moderate temperatures that can support both species, whereas the coldest stream reaches are suitable only for bull trout (Rodtka and Volpe 2007). Mapping the spatial distribution of habitat for native and introduced species can provide important insights on habitat amount, distribution, and connectivity that influence interactions and population dynamics of species (Stevenson‐Holt et al 2014, Alakoski et al 2019). Habitat suitability maps also enable identification of areas with species overlap to help managers prioritize treatments to recover native species.…”