Birth rate and offspring survival in a free-ranging wild boar Sus scrofa population

Abstract

We estimated birth rates in wild boar Sus scrofa by counting embryos in the uterus of females killed in individual or drive hunts. Counting corpora lutea in the ovaries gave information on embryo:corpus luteum rate, which can be useful for estimating birth rates in early stages of pregnancy. Birth rates were estimated separately for the different age groups. Age was estimated by means of teeth wear. Survival was estimated by direct observations counting the piglet:female ratio in matrilineal groups. The method is suitable for assessing summer survival only, as 8-9 months after birth, matrilineal groups begin to disintegrate. Average estimated birth rate was 6.7 ± 2.1 (N = 51). We found a positive linear relationship between conception rate and age of female, conception rate and body mass, and conception rate and body length, respectively. In late stages of pregnancy, embryo:corpus luteum rate proved to be 0.83 ± 0.15. Recruitment of piglets to the female population was low; more than half of the piglets had perished by the end of September. The highest mortality rate occurred in the first weeks of the piglets' lives.