Not tonight, deer – the male antelope that refuses sex
Saturday 5 January 2008
A scientist from the ZSL investigating sex secrets of the topi antelope has found that some males are so aggressively pursued by the females to mate that they refuse the advances of previous partners in order to conserve their sperm.
The ZSL research, published in the journal Current Biology, reveals the complicated reproductive behaviour of the African topi. Dr Jakob Bro-Jorgensen found that the topi is a promiscuous species and, as a result, particularly popular males are choosing not to mate with females that they have mated with previously, if they have the opportunity to mate with new females.
Dr Bro-Jorgensen commented, “I was interested to see that in cases where the male antelope was free to choose between females, he deliberately went for the most novel mate, rather than the most high-ranking. However, some pushy females were so aggressive in their pursuit of the male that he actually had physically to attack them to rebuff their advances.”
The research was undertaken in the Masai Mara area of Kenya, in the traditional breeding or “lekking” grounds of the topi. The antelope come together at one particular time of the year and in one particular place for just over a month to mate, with individual females coming into oestrus (being fertile) for one day only.
“The pressure on the both the male and the female topi is just extraordinary,” added Dr Bro-Jorgensen. “The females have just a single day to ensure that they become pregnant, and preferably with a hotshot male, so they must focus all of their energies into ensuring that males mate with them in that time. The males, however, must focus on maximising the potential of their sperm to ensure they impregnate as many females as possible. It was not uncommon to see males collapsing with exhaustion as the demands of the females got too much for them.”
It is hypothesised that this behaviour allows the male to maximise their chances of fatherhood, as the more times he mates, the more reduced his sperm supply becomes, so it is logical for him to conserve it for the widest array of mates possible. On the other hand, females may also be interested in mating with several partners to ensure fertilisation in case their first choice happens to have reduced sperm supply or be genetically incompatible with them. However, it also appears that some unpopular males harass females to mate against their will.