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

Abstract

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 capacity; and iiii) the variable density‐dependent pattern among populations may be due to differential harvest regimes, causing variable post‐peak densities, and thus different levels of resource competition among populations.

Deer, predators, and the emergence of Lyme disease

“…S8; <25% in MN, PA, and WI, and <40% in VA) suggest increases in deer abundance would be represented by increased harvests, because hunters are not saturated with deer. Longitudinal hunter harvest data has been shown to correlate well with trends in deer density and has been used in the literature not only for crude population trends but also for more sophisticated time-series analysis (42)(43)(44)(45).…”

Characteristics of spermatozoa and reproductive organs in relation to age and body weight in Swedish moose (Alces alces)

“…Research on moose reproduction has mostly focused on female characteristics such as age and weight at sexual maturity (Ferguson, 2002;Sand and Cederlund, 1996;Saether and Heim, 1993), fecundity at different ages (Ericsson et al, 2001;Garel et al, 2009;Sand et al, 1996;Solberg et al, 2007;Saether and Haagenrud, 1983), and senescence (Ericsson et al, 2001;Garel et al, 2009), whereas studies on male moose reproductive characteristics are relatively few.…”

Spring-loaded reproduction: effects of body condition and population size on fertility in migratory caribou (Rangifer tarandus)

“…Reproductive performance can be affected by extrinsic factors including density (Albon et al 1983;Sand et al 1996), predation, parasitism (Hughes et al 2009), and weather (Adams and Dale 1998;Post and Stenseth 1999). It may also vary with individual characteristics such as age (Festa-Bianchet 1988;Sand et al 1996;Ropstad 2000), previous reproductive experience, and body condition (Sand et al 1996;Testa and Adams 1998).…”