Climate, Plant Phenology and Variation in Age of First Reproduction in a Temperate Herbivore

Abstract

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. British Ecological Society is collaborating with JSTOR to digitize, preserve and extend access to Journal of Animal Ecology. Summary 1. Density-independent weather effects can have important consequences for the demography of terrestrial herbivores because precipitation, temperature and insolation influence plant phenology, forage quality and biomass production, which in turn affects the habitat carrying capacity. Since forage digestibility influences intake and weight gain, life-history traits of young, growing animals are likely to reflect variation in the prevailing weather. 2. This paper specifically investigates spatial and temporal variation in age at maturation in female red deer (Cervus elaphus) in Norway in relation to climate variables known to influence primary production. Our findings are corroborated by analysing differences in age at maturation in 21 cohorts of red deer on the Isle of Rum, Scotland. 3. In Norway the majority of females ovulated as yearlings and calved for the first time as 2-year-olds. The proportion calving for the first time at two years varied from 0 23 to 0 67 between regions and fluctuated from 0 46 to 0 76 between cohorts. On Rum, where age of maturation was delayed at least a year, the proportion calving for the first time as 3-year-olds varied between cohorts from 0 0 to 0 89. 4. In a subset of yearlings culled in Norway at the time of conception, the spatial and temporal differences in ovulation rates were related to the geographical and annual variation in body weight. 5. Both the spatial and temporal variation in the proportion of 2-year-olds calving in Norway, and cohort differences in the proportion calving as 3-year-olds on Rum, were negatively related to variation in May-June degree days 12 months earlier. 6. Although primary production on the preferred herb-rich Agrostis-Festuca grasslands was positively correlated with temperature in May and June on Rum, the proportion of females calving as three years old, was negatively correlated with annual differences in May-June primary production. 7. We argue that retarded phenological development, during periods of cooler weather, enhances diet quality because leaf:stem ratios and digestibility of plant parts decline more slowly. Thus, weight gain during the early summer growth spurt should be rapid during cool May-June weather, increasing the probability of conception in the autumn. 8. Since density-independent variation in food availability also influences fitness components which commonly have a more pronounced influence on population demography, for example offspring survival, we argue that our results highlight the potential importance of variation in weather on herbivore abundance.

Growth and body weight of free-range reindeer in western Alaska

“…Body weight of adult females in Rangifer influences conception rates (Dauphine, 1976;Ropstad et al, 1991;, calving time (Reimers, 1983;Cameron et al, 1993), birth weights (Skogland, 1984), recruitment rate (Skogland, 1986;Post & Klein, 1999), and age at first reproduction (Leader-Williams & Rosser, 1983;Langvatn et al, 1996;. As population densities increase, a decline in growth rate and body weight (Skogland, 1983) will affect maximum sustained yield (Karter & Dieterich, 1989;, and may indicate changes in range quality (Fox, 1999).…”

Dominance, fatness and fitness in female American bison, Bison bison

“…Delayed calving is related to reduced future fertility of the mother (red deer: Clutton-Brock et al 1987;caribou, Rangifer tarandus: Cameron et al 1993). Late-born daughters reproduce later (red deer: Langvatn et al 1996), mature later and have lower fecundity (bison : Green 1987;Green & Rothstein 1993).…”

Morphometric characterization of Mesola red deerCervus elaphus italicus(Mammalia: Cervidae)

“…Young adult (i.e. 2-4 years old) hinds were on average 15 kg lighter than fully mature ones, which may contribute to explain the low birth rate (Mattioli et al 2003;Ferretti & Mattioli 2012), since in hinds ovulation and pregnancy are related to the attainment of threshold body mass Langvatn et al 1996). The retarded body growth is also responsible for the delay in antler development of juvenile stags.…”