During a recent Africa Geographic safari in Botswana, we came across a sounder of warthogs led by a rather determined and, clearly randy, hog.
As we stopped and tuned into the surrounding soundscape, we all noticed a sound that can be best described as the rhythmical workings of a two-stroke engine. It became evident that the sound was stronger when the hog faced us, and softer when it faced away, thus we realised the sound was being produced by the hog itself.
Through our binoculars we noticed that the warthog’s face was darkened by an oily secretion and its lower jaw was motioning up and down constantly. Also noticeable was a build-up of saliva frothing out of his mouth, which he often smeared against a stump, or the unfortunate backside of one of the females he courted.
At the time we didn’t really have a clue what we were looking at – it looked like some sort of mating display. After showing the tape to several field rangers, biologists and well-travelled bush-fundies it became evident that this behaviour has been seldom witnessed, and so I took it upon myself to find out more.
In short, the behaviour was indeed nothing else but textbook warthog courting behaviour. The darkened area you can see in the video is caused by glandular secretions from the pre-orbital gland – much like the secretions on the side of an elephant’s head when in musth. The ‘two-stroke’ guttural sound we were hearing is better known as champing and it is apparently produced by repeatedly gnashing and chattering the molars and tusks.
But in looking deeper into the nature of this gnashing sound, I came across a a rather sinister twist to this tale. As it turns out, most pigs have a gland on the inside of their upper lip – in warthogs it is behind the bulge of skin that surrounds the tusks and it is known as the lip gland. You may have seen it in action when you last saw a warthog rubbing the sides of its nose against a rock or tree stump, the purpose of this behaviour is to mark their territory with their scent.
It is currently believed that the rhythmic act of champing, combined with tusk-gnashing expresses a fatty secretion from the glands, which helps with the formation of the foamy saliva that we noticed. This saliva acts as a carrier to a pheromone produced by the boar’s sub-maxillary glands, which are loaded with androgen steroids. This is so much the case that when picked up by the females (especially if they are smeared with it), it induces females in oestrous to assume lordosis, or ‘assume the position’.
As the saying goes, ‘all is fair in love and war’ – hence I am not surprised that anything born with a warthog face would resort to such trickery to spread the love.