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Body size and reproductive parameters in the wild boar Sus scrofaPedro FERNÁNDEZ-LLARIO and Patricio MATEOS-QUESADA Fernández-Llario P. and Mateos-Quesada P. 1998. Body size and reproductive para meters in the wild boar Sus scrofa. Acta Theriologica 43: 439-444.Parameters involved in the reproductive performance of wild boar Sus scrofa Linnaeus, 1758, such as fertility rates and litter size, show considerable intrapopulational variability. In this work we analyze a total of 198 females, culled by hunting in the Villuercas region (Cáceres, Spain), in an area with food suplementary throughout the year. The 31% of the total number of females examined, and the 47% of the female above 44 kg body weight, were in breeding condition (either gestating or lactating). There were no differences among four central months throughout the breeding period in the proportion of breeding females. Mean litter size was positively influenced by physical features of the female such as body size and weight. The month of the year (within the central breeding period) did not affect litter size. These findings indicate that reproductive decisions of females, ie whether or not to start gestation and the number of offspring in the litter, are mainly determined by their physical features.

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We examined the reproductive phenology of wild boar populations in four regions of the western Iberian Peninsula during the 1999/2000 hunting season (OctoberFebruary). To estimate conception dates and birth distribution frequencies, we used foetal weights. Regions differed significantly, and we detected a relationship between region and birth distribution frequencies. Throughout the year, food availability had a major influence on the distribution of farrowing. Although a short period of high food availability leads to highly synchronous births, even in relatively harsh environmental conditions, adult females that exploit low-quality food items appear to be able to give birth at any time of the year.

Competition to access the front teats in the domestic pig is strong during the first days of life, despite the fact that the number of piglets is fewer than the number of teats. Preference has been explained in terms of greater milk production (although it might also be the consequence rather than the cause), or reduced risk of crushing when the female lies down to begin a suckling session. Here, with the aim of determining whether one cause might be the body and reproductive modifications caused by artificial breeding, we analysed teat preferences of wild boar piglets in the wild. Fifty-one hunted females in lactation in the Western Iberian Peninsula were analysed. In contrast to domestic pigs, wild boar piglets showed a clear preference for rear udders. This preference was consistent for females of different ages and body characteristics, as well as for females hunted in different seasons. We suggest that the choice of rear udders in the wild boar may be related to the advantages of suckling at places offering higher protection from low temperatures and from predators, in contrast to domestic pigs, for which crushing is the main cause of mortality.