Lucy Cooke on duelling cows competing for a prime bull
Late afternoon on the grassy plains of the Serengeti. As the orange sun slinks towards the horizon, two topi (Damaliscus lunatus jimela) are duking it out in the long shadow of an acacia tree. It’s rutting season and this pair of mid-sized antelopes – think souped-up goats on stilts – have joined hundreds of other topi to spar for sex. The horny pair face off, charge and drop to their front knees as they lock their lyrate antlers, heads wedged against the ground in a vicious stalemate. After a few tense seconds, the more dominant topi makes the
most of a slight size advantage and shoves the other backwards along the ground. With the ignominy of a sumo wrestler expelled from the ring, the loser scuttles back into the herd shaking its head, leaving the victor free to claim the prize: sex with the prime bull. You read that right – bull. For these armed and aggressive rivals aren’t males fighting over cows, they’re females duelling over the top topi’s sperm.
After the short rains in February, female topis travel in large groups to cruise for mates at a lek – essentially a topi singles’ bar. Up to a hundred males gather in one area and mark out small adjoining territories for themselves using their dung, a surprisingly versatile material that creates a signature scent boundary between rivals.
Breeding season is intense as the females all come into oestrus for just one day of the year. This short fertility window leads to a 24-hour frenzy of sexual activity as each female mates with four to twelve males.
As the females shop for sex, rejected males are not above resorting to underhand tactics to win their attention.
If a female leaves his territory unmated, a scorned male will often sound an alarm call, a loud snort that signals a hyena or lion is nearby. This fake news alert encourages the exiting female to linger longer in the pretender’s territory for safety. With limited time to spare, she often winds up being mounted by the fraudster while she waits. It’s been calculated that topi only succeed in mating by bogus snorting on 10 per cent of occasions.
While some bulls must lie to get laid, others are fighting off females and knackered from the exertion. The top bulls command terrain at the centre of the lek and it’s these studs that have females battling over their finite seminal reserves. Some pushy cows even go so far as to charge top studs in the act of mounting other females.
This brazen tactic doesn’t always pay off, however. Disrupted males will often counterattack belligerent females and rebuff their advances with added aggression, especially if they’ve mated with them already.
This scenario of choosy males and competitive females is a reversal of the traditional sex roles predicted by Charles Darwin in his theory of sexual selection. But it may prove to be far more widespread now that we have
our eyes open to it.