Ecological correlates of regional variation in life history of the moose Alces alces: comment - response to B.-E. Saether, Journal of Wildlife Management, vol. 49, p. 977, 1985

Ecology, July, 1998 by Michel Crete

However, Saether et al. (1996) found that winter climate was a limiting factor for their moose populations, as calf mass increased by [congruent]40% during two snow-free winters (a very unusual situation for moose [Bedard et al. 1974]), and larger body size after mild winters resulted in higher fecundity of yearling females. From this observation, they concluded that regulating factors due to competition for forage likely contributed less to variation in recruitment rate than variation due to climate. Saether (1985) had already identified summer climate as a limiting factor for moose in Norway, its influence on somatic growth differing however between the south and the north of the country. Sand et al. (1995) observed that climatic harshness influenced body mass of adult Swedish moose more than density or browse availability, whereas Crete and Courtois (1997) found a relationship between winter and summer climate and calf production in an unproductive boreal range of northeastern Quebec. As Saether et al. (1996) observed in Norway, Sand (1996) also noted that the relationship between body mass and sexual maturity varied with latitude for Swedish moose. Three conclusions can be drawn from the preceding observations: (1) Saether et al. (1996) could not compare the relative importance of climate and competition for forage for moose fecundity because they had no data for populations regulated by food. (2) Climate might play a minor role in moose demography if influencing only somatic growth and sexual maturity; adult fecundity and survival have greater effects on population growth of cervids than sub-adult fecundity (Nelson and Peak 1982, Crete et al. 1996). (3) Climatic factors exert a variable influence on population dynamics throughout the range of moose. In this respect, the idea first proposed by Haldane (1956) could be true for moose - that regulation might be easier to detect in the core of the species range whereas limiting factors might gain in importance at the periphery (Crete and Courtois 1997).

Sinclair (1991) advocated the utilization of control and manipulated animal populations through wildlife management for scientific experimentation. In order to test the existence of density-dependent regulation by competition for forage in Fennoscandian moose and to test the stability of the equilibrium, one should exclude moose from hunting over an area large enough ([approximately]1000 [km.sup.2]) to reduce the importance of emigration (Crete 1989) and should monitor major demographic variables for comparison with contiguous, harvested populations. Doing the study in the core of the range of moose might yield more conclusive results than at the periphery.

Acknowledgments

B. E. McLaren, D. L. Murray, J. D. Wehausen, and an anonymous reviewer helped to improve this note by kindly commenting on a previous draft.

Literature cited

Bedard, J., E. S. Telfer, J. M. Peek, P. C. Lent, M. L. Wolfe, D. W. Simkin, and R. W. Ritcey, editors. 1974. Alces: moose ecology, ecologie de l'orignal. Les Presses de l'universite Laval, Quebec, Quebec, Canada.