Variation in the fecundity of roe deer in Britain: Effects of age and body weight

Abstract

This paper investigates variation in female fecundity in relation to effects of age and body weight within and between 15 populations of roe deer Capreolus capreolus (Linnaeus, 1758) in Britain. Analyses were based on carcass material and fecundity was assessed from the presence/absence and number of fertilised ovulations (corpora lutea) and implanted foetuses. A significant proportion (> 10%) of does ovulated in their first year in some populations, but such precocious reproductive activity rarely resulted in successful implantation of a foetus. Generally, the majority of yearling does (in their second year) conceived successfully, but average potential litter size was lower than among older animals. There was no consistent age- related variation in fecundity among does older than 2 years. Differences in fecundity between age and body weight classes suggest weight thresholds may exist for the onset of puberty and for successful conception as an adult. Fecundity of adults and yearlings was highly variable between populations and in some populations was considerably lower than previously reported for this species. Although differences between populations were correlated with differences in body weight, this relationship was insufficient to explain the wide variation in fecundity across Britain, suggesting fecundity body weight thresholds will be defined independently in separate populations.