Wildlife TV

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How do Nyala Mate?

on July 23, 2013

Very often in nature, the best male specimens are selected by the females so that the most suitable genes are passed onto the next generation and sometimes males will compete against each other for mating rights with females. We tend to assume that competition between male animals involves violence and that it is the strongest that prevails, but this is not necessarily the case, and as always, nature is full of surprises.

Nyala

We saw in the previous post how male blue wildebeest (Connochaetes taurinus) go to great lengths to demonstrate their physical prowess over each other, but this next antelope has a very different strategy when it comes to mating; the Nyala (Tragelaphus angasii) lives a very different lifestyle and has some very different behaviours. Whereas wildebeest are grazers that live in open grass plains, nyala are browsers that live in more densely vegetated areas. One of the most significant differences between the two antelope species’ mating techniques is that nyala are not territorial and females do not select males based on the territory they control, also, nyala bulls very often avoid physical confrontation when asserting dominance so it’s not necessarily the strongest specimen that is selected by the females.

Nyala are an interesting antelope noted for their very striking sexual dimorphism; females are small, hornless and rusty brown in colour whereas males are large with long horns and long fur that’s slate grey in colour. The size differences between the sexes is so distinct that males are named using the large antelope categories, bulls (as opposed to cows) and females are used using the small antelope categories, ewes (as opposed to rams). Nyala bulls are a lot more dramatic in appearance and this has some degree of relation to their mating strategy.

A nyala bull and ewe stand next to each other demonstrating sexual diamorphism.

The sexual dimorphism between male and female Nyala (Tragelaphus angasii) is very striking.

Nyala bulls are mostly solitary or sometimes live in bachelor groups, whereas the females form herds with the youngsters, however, nyala live in small numbers because of their densely vegetated habitats. Solitary bulls will roam their home range feeding and avoiding predators, and generally just living their lives until they encounter females at which point, their priorities turn to reproduction. Upon meeting a ewe, a bull will inspect her to see if she is in oestrus (ready for mating) by sniffing around her tail area and if she is receptive, he will have to win her favour by displaying; he does this by raising the fur along his back, called his dorsal crest, and lowering his horns to avoid aggressive signalling. A male may stay with a female, or small group of females for a day or two before moving along.

Generally, male nyala co-exist quite peacefully and do not engage each other if they meet, however, they are still competitive if they encounter each other in the presence of females. If one male is courting with a female, or group of females, and another male approaches, they must compete for the mating rights; sometimes this is achieving by sparing where they will clash their horns and attempt to demonstrate their physical strength and push away their rival. However, nyala are quite capable of deciding their disputes without resorting to violence, and will very often use their peaceful methods to decide which of them is dominant. When two males meet, they will approach each other slowly and move alongside one another, raising their dorsal crests and stretching out their bodies to make themselves as large as possible, performing a lateral/broadside display. The smaller individual will usually acknowledge their defeat and move away, leaving the receptive ewes for the winner, but if not, it is then that they will resort to a physical confrontation.

A nyala bull (Tragelaphus angasii) with a raised dorsal crest.

This nyala bull (Tragelaphus angasii) clearly shows its white dorsal crest of fur along the ridge of its back.
Photo Credits.

The nyala’s strategy may seem wimpy by comparison to the fearsome battles of other species, but I like to think of it as gentlemanly. Their generally peaceful interactions have a significant advantage over physical confrontation in that the bulls do not have to risk any injury or even the potential of death; even if a male animal is very confident and even if it wins a fight, it might end up with an injury that is detrimental to its health over time. By performing surrogated battles as they do, they can see who is the strongest/fittest and accept it without risk, but even when nyala do resort to fighting, they are usually very brief and not very fierce.

I hope you enjoyed learning about nyala and their mating techniques. For other animals check the series page.

In the next post we will look at some of the ways spiders reproduce.

Much love,

-Nick

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