Annual variation in maternal age and calving date generate cohort effects in moose (<Emphasis Type="Italic">Alces alces</Emphasis>) body mass |
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Authors: | Erling J Solberg Morten Heim Vidar Grøtan Bernt-Erik Sæther Mathieu Garel |
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Institution: | (1) Norwegian Institute for Nature Research, Tungasletta 2, 7485 Trondheim, Norway;(2) Center for Conservation Biology, Department of Biology, Norwegian University of Science and Technology, 7491 Trondheim, Norway;(3) Laboratoire de Biométrie et Biologie Evolutive, CNRS, UMR 5558, Université de Lyon, Université Lyon 1, 43 boulevard du 11 novembre 1918, 69622 Villeurbanne, France |
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Abstract: | A general feature of the demography of large ungulates is that many demographic traits are dependent on female body mass at
early ages. Thus, identifying the factors affecting body mass variation can give important mechanistic understanding of demographic
processes. Here we relate individual variation in autumn and winter body mass of moose calves living at low density on an
island in northern Norway to characteristics of their mother, and examine how these relationships are affected by annual variation
in population density and climate. Body mass increased with increasing age of their mother, was lower for calves born late
in the spring, decreased with litter size and was larger for males than for female calves. No residual effects of variation
in density and climate were present after controlling for annual variation in mother age and calving date. The annual variation
in adult female age structure and calving date explained a large part (71–75%) of the temporal variation in calf body mass.
These results support the hypotheses that (a) body mass of moose calves are affected by qualities associated with mother age
(e.g. body condition, calving date); and (b) populations living at low densities are partly buffered against temporal fluctuations
in the environment. |
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Keywords: | Calf sex Density Climate Maternal effects Mixed effect models Cohort effects |
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