In Autumn, male red deer make their voices heard across moorland as they size each other up during the annual rut.

I tramp through the heather and hunker down on a slab of grit stone. Looking down from the edge, my eyes begin to focus, one by one, on tines emerging from the horizon. One. Two. Another. Another.

To the left is a mature male, noticeably larger than the others in my line of sight. He plays his role well, guarding his harem at the cost of all else. He's too focused to sleep and pumped too full of testosterone to eat. Over the course of the season, he'll lose 20% of his body weight - enough to make any man roar.

It's the roaring that makes the annual deer rut so impressive and with wild moorland as a backdrop, my imagination jumps straight to scenes from prehistory, when giant armadillos and the pleasingly named 'Smilodon' (Saber-toothed Tiger) roamed the earth around 5 million years ago in the Pliocene era. Amongst these iconic creatures was Cervus, the genus of deer from which Britain's modern deer (Cervus elaphus) developed. I can imagine the great beasts crossing these wild expanses, bellowing at each other just as they do now.

The chirpy trill of a pipit brings me back to the scene and I remember that my daydream is all wrong. This moorland is man-made.

It's not long before the roaring takes over again. If I close my eyes, the guttural 'bolving' is so distinct from anything else that I can pinpoint the location of yet another stag, lurking on the periphery and out of my sight. It's a clue that deer did not evolve to thrive on moorland. The proof is in the roar.

A red deer's roar is created much in the same way as the voice of a human - air is pushed over the larynx, the larynx retracts and sound is enabled. Studies have suggested that deer with greater stamina are better able to cope with the tiring activity of roaring and are probably more attractive to females looking for the best father for her offspring. For these stags, their well-trained larynx, just like that of a classically trained singer, will retract even further, creating a deeper, louder and more resonant sound. Singers call this 'singing with an open throat', but for the deer, this is prowess.

In deer, the larynx retracts much deeper into the throat than in humans, creating a low frequency sound that travels further across a territory. It's a quality found in woodland mammals rather than those inhabiting open spaces and yet deer, the UK's largest mammal, are found predominantly on open moorland.

Why?

What many people forget is that moorland has developed because of people and greatly, because of deer. As human populations increased, woodlands were cleared. Land was managed for agriculture, for grouse shooting and of course, for venison. The process shaped vast expanses of land into semi-natural, but incredibly beautiful tracts, to which the deer have been gradually confined.

The stag on my left is certainly claiming ownership of his hinds, roaring with barely more than a few minutes’ rest. Several males, young or past their prime, lurk opportunistically on the fringe of his harem. He watches them keenly, but they dare not provoke him.

With a high percentage of injuries sustained through fighting, it's likely that roaring is more about intimidation than provocation, enabling rival stags to size each other up and assess the risk: win and secure females; lose and risk injury, or worse, allow those opportunistic males to have their way with the harem.

It's a primal behaviour and it's compelling.

I watch the antlers of a rival male approach the mighty stag, his harem safely where he has parked them. As he bellows out across the heather, I find myself awed, not only by this majestic beast, but by its remarkable ability to adapt.

Deer survived the ice age, they survived mass hunting and they survived the clearance of their natural habitat. Now, not only do they survive, but they thrive on the poor nutrition of the open moors and do so, so successfully that their populations usually need to be controlled to conserve the delicate landscape.

The sun is lowering, the air is cooler and my gloves are on. Despite the roaring, the rival stag has weighed-up his opponent and deemed the risk worth the reward. He lowers his head and prepares for battle. It's time for my camera to make an appearance – wildlife photographers are suckers for a performance!

 

To read more:

Clutton-Brock, T. H., and S. D. Albon. "The Roaring of Red Deer and the Evolution of Honest Advertisement." Behaviour 69.3/4 (1979): 145-70. Web.

Fitch, W. Tecumseh, and David Reby. "The Descended Larynx Is Not Uniquely Human."Proceedings: Biological Sciences 268.1477 (2001): 1669-675. Web.

Clutton-Brock, T. H., and S. D. Albon. "Red Deer: Behaviour and Ecology of Two Sexes." University of Chicago Press (1982)