Density‐dependent variation in reproduction and body mass in female moose Alces alces

• Published in: Wildlife Biology
• Main Authors: Sand, Håkan, Bergström, Roger, Cederlund, Göran, Östergren, Marina, Stålfelt, Finn
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 1996
• Subjects: Alces alces
• Online Access: http://dx.doi.org/10.2981/wlb.1996.026; https://onlinelibrary.wiley.com/doi/full-xml/10.2981/wlb.1996.026; https://onlinelibrary.wiley.com/doi/pdf/10.2981/wlb.1996.026

Female body mass and reproduction from harvested moose Alces alces were compared in four populations of moose at different stages (densities) of population development, i.e. pre‐peak, peak and post‐peak, in Sweden during 1961–1991. In two (1 and 2) of the four populations, age‐related body mass and reproduction was significantly lower in the post‐peak (intermediate density) stage than in the pre‐peak stage; whereas for the other two populations (3 and 4), no differences, or higher growth and reproduction at post‐peak density, were found. In one population (2) data from all three stages (densities) of population development were available. Age‐specific mean body mass was 12.8% lower, and fecundity 46.0% lower (average among age classes), during the peak density stage, than during the pre‐peak stage, but did not differ significantly between the peak and post‐peak stages, except for fecundity in 1.5‐year‐old females. In the two populations showing a negative density‐dependent response (1 and 2), fecundity decreased more from pre‐peak to post‐peak density than could be predicted from the reduction in body mass. This suggested a lower reproductive investment per unit body mass at high and intermediate densities, compared to the low density stage. Similar to age‐related body growth and fecundity, the proportion of lactating and/or calf‐rearing females was significantly lower at post‐peak population density in populations 1 and 2 compared to pre‐peak densities, but only in the youngest reproducing age class (2.5 years). It is concluded that: i) the large increase in population density has resulted in density‐dependent resource limitation, which is expressed as lowered body growth and reproduction in two of the four populations studied; ii) the lower reproductive investment per unit body mass at higher densities may constitute an adaptive strategy to maximise juvenile survival as conditions deteriorate; iii) density‐dependent effects in moose may occur at densities which are lower than close to the ecological carrying ...