Abstract
Mean calving dates among 7 wild reindeer (Rangifer t. tarandus) herds in southern Norway varied between the 6th and the 27th of May. Ln transformed foetus weights relate linearly to ln age in days. Regression analyzes based upon 225 days pregnancy predicts birth wet weights between 4600 and 7500 g in the different areas and years. At 130 days, foetus weights varied between 547 and 746 g (mean=681, standard deviation s=63) in all areas and years, indicating that foetus growth up to this size is independent of mothers body weight or condition. During the remaining 95 days of pregnancy, very poor body condition, reflected in dressed weights, resulted in slower foetus growth and smaller regression estimated birth weights. The foetus weight variation recorded at similar dates within areas and sampling years indicates a dispersed breeding time mostly within two ovulations. A small sample of foetuses from pregnant yearlings and calves indicate that these cohorts conceive later than 2 yr + females. Assuming similar foetus growth pattern among all female age cohorts within areas, yearlings conceive around 1 week later and calves (in Ottadalen) more than 3 weeks later than 2 + yr olds.
Highlights
Variation in calving time and birth weight may play an important part in the demographic processes
Pregnant female dressed weights differed in the vari¬ ous areas as did the mean calving dates (Table 1)
The newborn weights presented are dry weights as presumably are the weights reported in the literature; i.e. the calves are licked dry by their mothers
Summary
Variation in calving time and birth weight may play an important part in the demographic processes. They relate both to neonatal mortality and to growth later in life (Lenvik & Aune, 1988; Eloranta & Nieminen, 1986). Jacobsen et al (1981), Rognmo et al (1983), Skogland (1984), Eloranta & Nieminen (1986) and Lenvik & Aune (1988) found that calves from undernourished reindeer were born smaller and suffered higher neonatal mortality than those from mothers in prime condition. This paper: (1) compares differences in foetus growth rates in relation to mother carcass weights in 7 wild reindeer areas in southern Norway, (2) assesses the variation of Rangifer, 22 (1), 2002
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