Cambridge University Press. Calf birthweight may influence milk production, and therefore gender could have a role via this mechanism since bull calves have larger birthweights. In his discussion of lion same-sex relations, Bagemihl is making use of published work by: Studies have estimated 8— In contrast, Graesboll et al[ 11 ] found birth of 2 consecutive bull calves had the greatest positive impact on milk yield. Janet Mann, Georgetown University professor of biology and psychology, argues that the strong personal behavior among male dolphin calves is about bond formation and benefits the species in an evolutionary context.
In agreement with the present study, three previous studies have shown favourable yields when a heifer calf is born to a primiparous dam,[ 6 — 8 ] whilst three studies have shown dams calving bulls at the start of second lactation have higher yields.
The authors have declared that no competing interests exist. For that to happen, the genes that make some males homosexual would have to have another, useful effect in other sheep. The Journal of Experimental Biology. Retrieved October 20,
Livestock Production Science.