BODY-MASS VARIATION IN SEMIDOMESTICATED REINDEER

The between-years and within-year variation in mass of semidomesticate d reindeer calves and females was studied in four herds in Finnish Lap land. Mass data covered 11-23 years. In two of the herds the intensity of supplemental feeding in mid and late winter increased throughout t he sampling period, whilst in two other herds the amount of food avail able per capita fell drastically as a result of increased density (abo ut 1-4 individuals/km(2)). Calf mass increased in both supplementally fed herds and female mass in one of them. In herds on natural ranges f emale mass was density dependent. Both calf mass (three herds) and fem ale mass (one herd) correlated negatively with the number of warm days in midsummer, most Likely because of severe insect harassment. The su m of snow depth during the two or three preceding winters influenced b ody mass inversely in one herd and positively in another herd, where s now depth probably increased the availability of arboreal lichens. The detrimental effect of warm midsummers disappeared with intensificatio n of supplemental feeding and the resultant improvement of female cond ition in winter. Within-year coefficients of variation (CV) correlated negatively with mean mass for calves in all four herds and for female s in one herd. For calves (two herds) and for females (one herd) CV co rrelated positively with the number of warm days in midsummer. We sugg est that late-born calves, and females who lost body reserves in winte r, were most sensitive to insect harassment.