Spleen size variations and reproduction in a Mediterranean population of wild boar (Sus scrofa)

We analysed spleen size variations of free-ranging wild boars from the west-central Iberian Peninsula during the hunting season (autumn and winter) in relation to the rut, the gestation effort and the attainment of sexual maturity by males and females. Females had larger spleens than males once they reached their sexual maturity. Individuals shot in winter had larger spleens than those shot in autumn, the start of the rutting period. In contrast to other reports, we found no influence of the reproductive status of adult females on their spleen sizes. Our findings may point to an influence of sex hormones, and possibly also stress hormones, and environmental factors on spleen development, mainly in adult and subadult males.