Aquatic habitat use in a semi-aquatic mammal: the Eurasian beaver

Abstract

Background Semi-aquatic mammals exploit resources both on land and in water and may require both to meet their habitat requirements including food- and building resources, refuges, and for social interactions with conspecifics. Within this, the specific availability of both terrestrial and aquatic resources is expected to impact individual fitness. Beavers are highly dependent on water for movement and protection from predators. They are central place foragers and mostly forage on woody vegetation near water although aquatic vegetation may also be an important food resource. However, little is known about their use of aquatic habitats. We aimed to address this knowledge gap by dead-reckoning fine-scale movement tracks and classifying fine-scale diving events, which we then related to the spatial distribution of aquatic vegetation and habitat components within the territory. Results Overall, there was a statistically clear decrease in probability that diving would occur at dawn and with increasing distance from territory borders. In addition, the distance from the lodge at which animals dived decreased through the night and during the spring/early summer. There was strong selection for diving habitats located closer to the riverbank, with stronger selection for these areas being observed in individuals with larger home ranges. We saw a higher selection for diving above clay sediment, and within 150 m from the lodge, presumably because mud and clay sediment tended to be located closer to the lodge than sand and rock sediment. Furthermore, we found a clear selection for diving in the presence of quillwort (Isoetes spp.), shoreweed (Littorella uniflora), and stonewort (Nitella spp.). Selection for these focal species was stronger among subordinate individuals. Individuals with lower body condition dived closer to the beaver lodge, and dives located further from the lodge were associated with high densities of aquatic vegetation. Conclusion We provide new knowledge on the aquatic habitat use in a semi-aquatic mammal and show how energetic constraints may shape how beavers spatially use the aquatic environment, whereby short and shallow dives appear most beneficial. We show how aquatic habitats may have great importance for both foraging, building materials and safety, and discuss to how they may affect the fitness of individuals.

Dead-reckoning elucidates fine-scale habitat use by European badgers Meles meles

“…Nevertheless, to whether the positional data were derived from GPS or GPS-enabled dead-reckoned data, labelled "GPS" and "DR", respectively current application of this technique to determine movement paths of free-ranging terrestrial species is surprisingly limited ( [7,9,39] cf. semiaquatic beavers [40]).…”

Hazel dormouse in managed woodland select for young, dense, and species-rich tree stands

“…The habitat quality of habitat patches has been shown to positively affect the survival and density of Italian hazel dormouse populations (Mortelliti et al ., 2014), highlighting the importance of preserving areas with high habitat quality in the larger patch system, and support dispersal to these by improving connectivity of habitat patches through for example plantation of hedgerows (Dietz et al ., 2018; Dondina et al ., 2018). We also observed a higher selection strength for dense vegetation among larger individuals which implies the energetic constraints shaping their habitat selection (Gallagher et al ., 2017; Mortensen et al ., 2021). Smaller individuals may be more willing to expose themselves to risks and potential predators in order to increase their energy intake for reproduction, growth, and prepare for hibernation (Juškaitis et al ., 2013; Pretzlaff et al ., 2014).…”

“…In addition, we examined the context dependent selection in individual-specific models weighed by the inverse-variance of the coefficient estimates by fitting the RSF with no random effect to each individual (Gillies et al ., 2006; Muff et al ., 2020). This enabled us to investigate how ecological variations between individuals (sex, body size), season (time of the year), and home range compositions (home range size, mean vegetation density, mean tree canopy cover, mean height of highest tree, mean circumference of thickest tree, and mean SSAS) may affect the found resource selection functions (Mysterud and Ims, 1998; Gillies et al ., 2006; McLoughlin et al ., 2010; Ariano-Sánchez et al ., 2020; Mortensen et al ., 2021).…”

The vomeronasal system in semiaquatic beavers

“…Beavers ( Castor spp. ; family Castoridae) are myomorph rodents that have become ecological specialists in semiaquatic environments (Mortensen et al, 2021) and they have uniquely adapted to aquatic life. For example, they have webbed hind feet, a flat tail that functions as a rudder in the water, and combing claws responsible for maintaining nonwettable fur (Bailey, 1923; Müller‐Schwarze & Sun, 2003).…”