| Summary: | Multiple fecundity (i.e., >2 fetuses or calves per female) is a rare and poorly known phenomenon in moose (Alces alces). In this paper I: (1) report the frequency of multiple fecundity of moose in Finland; (2) study the frequencies of multiple fecundity in different years and areas; (3) discuss the viability of litters with different numbers of progeny; and (4) discuss the possible fecundity effects of selective harvest and the evolutionary aspects of multiple fecundity. The embryo numbers of harvested cows were counted during 1980-89 (n = 2,347) and the proportion of single, twin, and triplet calves were determined from the 1986-99 moose observation material recorded in the field by hunters during the hunting season (n = 585,149). The material includes 4 sets of quadruplet calves, 1 set of stillborn sextuplets, and a moose female with 5 sets of triplet calves; a total of 30 calves in 15 years. In Finland, 60.38 % of pregnant moose cows had one, 39.37% two, 0.21% three, and 0.04% four embryos. In the observation material, 61.79% of the cows had one calf, 38.18% twin calves, and 0.03% triplet calves. The proportion of multiple cases decreased from south to north. The viability of single and twin calves was found to be very high, but only 15% of the sets of triplet calves seemed to survive up to the first fall. Calf survival rate was clearly higher in 1980-99 than in 1963-66, possibly depending on the different age structures of the female populations. According to the literature, the frequency of multiple fecundity in moose appears to be lower in North American than European moose populations.
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