TY - JOUR
T1 - Sex-ratio variation in Soay sheep
AU - Lindström, Jan
AU - Coulson, Tim
AU - Kruuk, Loeske
AU - Forchhammer, Mads C.
AU - Coltman, Dave W.
AU - Clutton-Brock, Tim
PY - 2002/12/1
Y1 - 2002/12/1
N2 - We studied the effects of ecological variables on the birth sex ratio of Soay sheep (Ovis aries) lambs on the island of Hirta, in the St Kilda archipelago, Scotland. Both individual- and population-level models were constructed. In the individual-based model, only population size was significantly associated with the sex of a lamb, with the probability of giving birth to a male lamb being positively associated with population size. However, this model explained a very small proportion of the variance in birth sex ratio. A multiple regression analysis of the annual population birth sex ratio also showed a slight increase in the proportion of males born in years following high autumn population density, but this result was not statistically significant. Population growth rate, Julian birthday, litter size, mother's age and weight, and the weather conditions during the gestation and neonatal period did not explain significant variation in the birth sex ratio.
AB - We studied the effects of ecological variables on the birth sex ratio of Soay sheep (Ovis aries) lambs on the island of Hirta, in the St Kilda archipelago, Scotland. Both individual- and population-level models were constructed. In the individual-based model, only population size was significantly associated with the sex of a lamb, with the probability of giving birth to a male lamb being positively associated with population size. However, this model explained a very small proportion of the variance in birth sex ratio. A multiple regression analysis of the annual population birth sex ratio also showed a slight increase in the proportion of males born in years following high autumn population density, but this result was not statistically significant. Population growth rate, Julian birthday, litter size, mother's age and weight, and the weather conditions during the gestation and neonatal period did not explain significant variation in the birth sex ratio.
KW - Maternal effects
KW - Ovis aries
KW - Sexual size dimorphism
KW - St Kilda
KW - Trivers-Willard hypothesis
UR - http://www.scopus.com/inward/record.url?scp=0037672724&partnerID=8YFLogxK
U2 - 10.1007/s00265-002-0545-4
DO - 10.1007/s00265-002-0545-4
M3 - Article
SN - 0340-5443
VL - 53
SP - 25
EP - 30
JO - Behavioral Ecology and Sociobiology
JF - Behavioral Ecology and Sociobiology
IS - 1
ER -