Richard Collins: Why stags indulge in their own fake news and spin

A Red stag believed to be the largest ever seen in Killarney National Park. Photo: Peter O'Toole

A ‘Royal’ stag has 12 antler ‘points’.An ‘Imperial’ one has 16. Killarney’s ‘ Grand Master,’ with 21, is almost certainly Ireland’s largest deer(Irish Examiner, October 15).

Huge amounts of food are required to develop such spectacular adornments and a new pair must be grown each year. But the effort pays off; large antlers intimidate rival males during the autumn rut. They also suggest that the owner’s sperm count is equally impressive, encouraging hinds to join his ‘harem’ of concubines.

But antlers are not the only string to a stag’s bow; rutting males indulge also in exhaustive ’singing’ competitions. At the height of the mating season, a stag may roar throughout the day. The pitch of his utterances is crucial. The lower it is, the farther the sound travels but, more importantly, pitch advertises the caller’s size; the bigger the stag, the lower its calls will be. Nor are such vocal communications confined to deer. Wolves, for example, gauge the size of a rival pack by listening to the chorus of howls its members produce.

But another factor is at play in vocalisation; mimicry. ‘Fake news’ and ‘spin’, whether human or animal, deceive and manipulate the hearer. ‘Dishonest’ signals are widespread in the animal kingdom. Mute swan cygnets, for example, continue to produce the high-pitched squeaks of their babyhood even when almost fully grown. As a new breeding season approaches, their father wants them out of his territory, to ensure that sufficient food will be available for his pen to form eggs and raise the coming season’s brood. Feeding extra mouths from the previous year is not on; if the youngsters remained, he would have to secure a much larger territory. The lingering cygnets don’t want to depart into the big bad world, so they issue baby-talk calls to stimulate his fatherly instincts. These help reduce his aggression and delay the eviction. Nor is such dishonest signalling confined to swans. Songbirds arriving in a new area may pass themselves off as locals by picking up the regional dialect. The low-pitched calls of a stag depend on body size, making them difficult to fake, but even they might not be entirely authentic.

Vocalisation and mimicry are closely connected; both depend on aural learning ability. So are they just two sides of the same coin?

Scientists at the Max Planck Institute have compared vocalisation to body size in a range of mammal species. Their results confirm that species which are particularly skilled at picking up sounds tend also to be good mimics. Deer, they found, can produce lower-pitched calls than their body size would seem to dictate. Nor does pitch of vocalisation necessarily correlate with a caller’s bulk. Whales and dolphins, for example, are able to transmit a wide range of sounds. Yet they routinely produce much higher-pitched sounds than their huge frames might suggest. Proclaiming size, it seems, is not the sole evolutionary driver of pitch, nor was the evolution of mimicry just a bi-product of vocalisation.

Attempts to solve a mystery sometimes deepen it. Research on this topic may be such a case.

• Andrea Ravignani & Maxime Garcia. A Cross-species Framework to Identify Vocal Learning Abilities in Mammals. Philosophical Transactions of the Royal Society B. 2021.