title: Group or ungroup - moose behavioural response to recolonization of wolves.
abstract: BACKGROUND
  Predation risk is a primary motivator for prey to congregate in larger groups. A large group can be beneficial to detect predators, share predation risk among individuals and cause confusion for an attacking predator. However, forming large groups also has disadvantages like higher detection and attack rates of predators or interspecific competition. With the current recolonization of wolves (Canis lupus) in Scandinavia, we studied whether moose (Alces alces) respond by changing grouping behaviour as an anti-predatory strategy and that this change should be related to the duration of wolf presence within the local moose population. In particular, as females with calves are most vulnerable to predation risk, they should be more likely to alter behaviour.
  
  
  METHODS
  To study grouping behaviour, we used aerial observations of moose (n= 1335, where each observation included one or several moose) inside and outside wolf territories.
  
  
  RESULTS
  Moose mostly stayed solitary or in small groups (82% of the observations consisted of less than three adult moose), and this behavior was independent of wolf presence. The results did not provide unequivocal support for our main hypothesis of an overall change in grouping behaviour in the moose population in response to wolf presence. Other variables such as moose density, snow depth and adult sex ratio of the group were overall more influential on grouping behaviour. However, the results showed a sex specific difference in social grouping in relation to wolf presence where males tended to form larger groups inside as compared to outside wolf territories. For male moose, population- and environmentally related variables were also important for the pattern of grouping.
  
  
  CONCLUSIONS
  The results did not give support for that wolf recolonization has resulted in an overall change in moose grouping behaviour. If indeed wolf-induced effects do exist, they may be difficult to discern because the effects from moose population and environmental factors may be stronger than any change in anti-predator behaviour. Our results thereby suggest that caution should be taken as to generalize about the effects of returning predators on the grouping behaviour of their prey.
authors.affiliation: Department of Ecology, Grimsö Wildlife Research Station, Swedish University of Agricultural Sciences, SE-730 91 Riddarhyttan, Sweden.
authors.forename: Johan
authors.initials: J
authors.lastname: Månsson
authors.affiliation: Département de Biologie, 1045, av de la Médecine, Université Laval, Québec, G1V 0A6 Canada.
authors.forename: Marie-Caroline
authors.initials: MC
authors.lastname: Prima
authors.affiliation: Department of Ecology, Grimsö Wildlife Research Station, Swedish University of Agricultural Sciences, SE-730 91 Riddarhyttan, Sweden.
authors.forename: Kerry L
authors.initials: KL
authors.lastname: Nicholson
authors.affiliation: Department of Ecology, Grimsö Wildlife Research Station, Swedish University of Agricultural Sciences, SE-730 91 Riddarhyttan, Sweden.
authors.forename: Camilla
authors.initials: C
authors.lastname: Wikenros
authors.affiliation: Department of Ecology, Grimsö Wildlife Research Station, Swedish University of Agricultural Sciences, SE-730 91 Riddarhyttan, Sweden.
authors.forename: Håkan
authors.initials: H
authors.lastname: Sand
keywords: Alces alces; Behaviour; Canis lupus; Group size; Predator; Prey; Ungulate; anti-predator