An extensive study of the foraging ecology of beavers (Castor canadensis) in relation to habitat quality

Abstract

The objective of this study was to examine the foraging behaviour of the beaver (Castor canadensis Kuhl, 1820) and to explain its selection of terrestrial woody plant species according to central place foraging theory. Limitations in variety of food items in most studies with regard to size and (or) distance from the central place and information on availability of forage choices give a partial view of the subject. In this study, the theory is tested in a natural environment with high variability in food items with regard to these factors. Foraging choices by beavers were inspected by measuring variables on cut and uncut trees of every species encountered within 1 m of trail systems made by 25 beaver colonies in Kouchibouguac National Park in New Brunswick, Canada, thereby quantifying the availability of the different food items. The effect of habitat quality (food availability) on the foraging behaviour of beavers was also tested. The results of this study suggest that with increasing distance from the pond, beavers in high-quality habitats selected fewer, but larger, trees and are more species selective. This selectivity was diminished in habitats of lower quality. The results of this study are consistent with the predictions of the central foraging theory.Résumé : Le comportement alimentaire du castor (Castor canadensis Kuhl, 1820) et son choix de plantes ligneuses terrestres en fonction de la théorie de la quête alimentaire à partir d'un point central font l'objet de cette étude. Les études précédentes constituent des bilans partiels du sujet, en raison de carences dans la diversité des plantes ligneuses disponibles, quant à la taille et la distance du point central, et (ou) dans l'évaluation de leurs disponibilités respectives. Notre étude teste les prédictions de la théorie dans un environnement naturel qui incorpore une grande variété de plantes ligneuses d'après la taille, la distance à l'étang et la composition spécifique. Nous avons déterminé les choix alimentaires des castors en mesurant les caractéristiques des plantes ligneuses coupées et non coupées présentes jusqu'à une distance de 1 m de part et d'autre des sentiers formés par les castors de 25 colonies dans le parc national Kouchibouguac au Nouveau-Brunswick, Canada afin de déterminer la disponibilité des plantes alimentaires. L'effet de la qualité de l'habitat (disponibilité des plantes alimentaires) sur le comportement alimentaire est également testé. En s'éloignant de l'étang, les castors deviennent plus sélectifs au niveau des espèces choisies et sélectionnent de plus gros arbres, mais en plus petit nombre. Cette sélectivité diminue dans les habitats de moindre qualité. Les résultats obtenus sont en accord avec les prédictions de la théorie de la quête alimentaire à partir d'un point central. Gallant et al. 933

Long-term effects of supplementary feeding of moose on browsing impact at a landscape scale

“…Central-place foraging theory, an application of the wider optimal foraging theory, describes space-use and foraging patterns by animals that frequently return to a focal place such as a den or a nest (Orians and Pearson, 1979). It has also been used as an effective tool to describe radial pattern of habitat use in a wide range of herbivores (Gallant et al, 2004;Bakker et al, 2005;Raffel et al, 2009;Shrader et al, 2012). Central-place foraging theory predicts a decline in space use and an increase in selectivity with increasing distance from the central place (Orians and Pearson, 1979;Rosenberg and McKelvey, 1999).…”

The role of forage availability on diet choice and body condition in American beavers (Castor canadensis)

“…Aquatic and terrestrial forage availability has been used to infer habitat quality, with beaver litter size increasing with overall forage availability (Fryxell, 2001;Baker, 2003;Baker et al, 2005). Further, beavers select certain plant species among many species consumed (e.g., deciduous species over coniferous species; Busher, 1995), and are more selective in high-quality habitat (Gallant et al, 2004), presumably to improve fitness. For example, beavers feeding on quaking aspen (Populus tremuloides), considered a high-quality food, produced more kits than beavers feeding on cottonwoods (P. deltoides), willows (Salix spp.…”

Preliminary investigation of the effects of timber harvesting on the activity status of beaver lodges in central Ontario, Canada

“…Beavers generally forage within 60 m of the water (Johnston and Naiman 1990, Donkor and Fryxell 1999, Martell et al 2006, likely in response to energetic requirements of transporting trees and the risk of predation (Basey and Jenkins 1995, Barnes and Mallik 2001, Gallant et al 2004. Hence, as we observed, forest disturbances in proximity (within 100 m) of the shoreline would have the most influence on the activity status of beaver lodges.…”

“…and willow (Salix spp.) are considered preferred forage species (Johnston and Naiman 1990, Donkor and Fryxell 1999, Barnes and Mallik 2001, Gallant et al 2004. Most beaver impoundments are on small streams resulting in the creation of ponds with associated changes in water flow and nutrient cycling (Naiman et al 1986, Martell et al 2006, and ultimately, changes in vegetation (Parker et al 2007), fish, and wildlife communities.…”