Territoriality and time budgets in beavers during sequential settlement

Abstract

OLET. B.A. • and ROSELL, F. 1994. Tenitoriality and time budgets in beavers during sequentiat settlement. Can. J. Zool. 72: 1227-1237. Beavers (Castor fiber) were sequentialJy released into a previously unoccupied area. The settlement of the animals approximated an ideal despotic distribution: they successively settled in rich habitat and then in poor habiiat, and then became tloaters. This panem is regarded as evidence that territorial behavior limited density. The early arnvals showed aseasonal differenee in territory size (small in winter, large in late spring and summer). which was expe.. cte'd ·from optimal lerritory size theory but which was not found in later arrivals. In the first 2 years, the beavers were swimming very large distances (up to 20.0 km per night), and were apparently undergoing a long-tenn decline in body condition. Body temperature decreased during sw'inuning, especially in winter (daily amplitude 2.04OC). Each year. winter lerritories were about the size (7.9 :t 0.9 (SE) km, including 3.0 ± 0.4 km of wooded banks) that beavers could patrol daily without losing body condition. 1be number of letritories established at any one time during the 5 years of study was only halfthe canying capacity calculated on the basis of the cunent length of wooded banks within territories, in accordance with the p~~tion for sequential settlement in~inear habitats. However, extensive no-man 's-Iand was not present between territories, b~~early anivals claimed larger territories than later ones. Social and thennoregulatory factors seem to play an important role in detennining the costs of temtory defense. and hence tenitory size. Overexploitation of the beaver 1 s main food source, witlow <Sa/ix 'spp.).. seems unlikely in this productive habilat. Des Castors europeere; (Castor fiber) ont ete relåches progressivement dans une aire prealablement inoccupee. Le type de colonisation utilise se rapprochait d'une repartition despotique ideate : les castors ont d'abord envahi les habitats riches. puis les babitats pauvres et fioalement les' demiers arrivants etaient des vagabonds. Ce type de colonisation indique que 'le componement territorial des castors en limite la densite. Chez les premiers arrivants. la taille des tenltoires etait fonction de la saison (petits territoires en hiver, grands tenltoires au printemps et en ete). ce qui correspond bien ala th&>rie de la taille optimale des tenitoUes" mais ce pattem ne s'est pas repete chez les colonisateurs plos tardifs. Au cours des 2 premieres ann6es, les castors paroouraient de tres grandes distances (jusqu'a 20,0 km par nuit) et semblaient prets asubir une deterioration along tenne de leur condition physique. La temperature du corps baissait au cours de la nage, surtout en hiver (amplitude quotidienne de 2,04°C). Chaque annee, les territoires d'hiver avaient a peu pres les dimensions (7.9 ± 0,9 (erreur standard) km, dont 3,0 :t 0,4 km de berges boisees) que les castors pouvaient patfouiIler chaque jour sans subir de deterioration de leur condition physique. Le nomb...

Territory and group sizes in Eurasian beavers (Castor fiber): echoes of settlement and reproduction?

“…Binoculars were used when needed. Given the range of behaviours displayed by the beavers in both study sites (see Nolet and Rosell 1994;Sharpe and Rosell 2003;Herr and Rosell 2004) it would appear that with due care, the effect of the spotlight, noise and the presence of the motorboat appeared to be minimal and we suggest that such disturbance is unlikely to have had an effect on the 8 beavers' behaviour. Indeed, on several occasions, animals approached the observers to within a distance of two metres and generally ignored the observers whilst doing so.…”

“…A 30 MHz-radio-transmitter with a life span of 1-2 years, depending on the size of the transmitter (52-92 g), was implanted intraperitoneally in 31 beavers in 1988-1991(Nolet and Rosell 1994. Of these 22 survived their first year after release (which was by far the most critical; Nolet & Baveco 1996).…”

“…All group members also appear to participate in the provisioning of young before and just after their emergence from the natal den at c. two months of age (Wilsson 1971;Patenaude 1983;Müller-Schwarze and Sun 2003). Beaver populations vary markedly in both group size (Bradt 1938;Wilsson 1971;Rosell and Parker 1995) and territory size (Collins 1976;Heidecke 1986;Nolet and Rosell 1994;Herr and Rosell 2004), and are therefore an ideal species on which to examine the economics of defensibility within group territorial systems. Based on the rational outlined above, we might expect beavers to be maintaining some minimum economically defendable area that decreases in size with increasing habitat quality.…”

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“…However low water temperatures make prolonged swimming a very costly activity (e.g. Nolet and Rosell, 1994).…”

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“…The anal gland papillae, however, must be rubbed on the substratum in order to deposit the exudates (Wilsson, 1971;Svendsen, 1978). All age classes (except kits younger than 5 months) and both sexes defend their territories by scent marking (Wilsson, 1971;Svendsen, 1980;Welsh and Müller-Schwarze, 1989;Nolet and Rosell, 1994;Buech, 1995). Scent is usually secreted by the Eurasian beaver onto small piles of mud and debris scraped together and placed close to the water's edge and at the borders of the territory throughout the entire year (Rosell and Nolet, 1997;.…”