Canines have a secret language based on their gaze, study claims
In humans, a flash of anger or moment of mischief can be conveyed with a simple look.
But we aren’t the only creatures to use our gaze to send covert messages – wolves and dogs can also communicate using their eyes alone.
A recent study in Japan found that eye shape, iris colour and facial markings in canines are part of an intricate eye-based communication system that humans can't yet comprehend.
Sayoko Ueda of the Tokyo Institute of Technology and Kyoto University led the study, which compared characteristics of the face and eyes among 25 different types of canines.
He found that the species with the most striking eyes tended to live and hunt in groups, where eye-based communication was necessary to bring down large prey.
Those with camouflaged eyes were more likely to live alone or in pairs, where communication with other members of their species may not be needed in the same way.
Professor Ueda’s team organised the species into three groups. Group A - which included the grey wolf, coyote, and golden jackal - had irises lighter than their pupils, and faces with markings that made their eyes easy to locate.
Group B contained the manned wolf, the dingo and the kit fox. These species only had facial markings that indicate the position of the eyes and the pupils aren’t visible. They also tend towards the single life, or bonded pairs.
Bush dogs, tanukis, and African wild dogs were in Group C. These canids had no markings around the eye to highlight the feature from the rest of the face. They tend to live in social packs, but usually hunt alone.
Scientists watched some the species interact in zoos and found that those with eyes that were easier to see were more likely to be social.
All three species gazed at each other about the same number of times, but the wolves held their gaze significantly longer than the foxes or bush dogs.
Previous studies suggested lighter iris colours are an adaptation to sunlight, similar to variations in human skin colour.
To test this theory, the Japanese team compared the eye colours of three wolf subspecies originating from Arctic, temperate, and subtropical regions.
But iris colour did not vary much between the group, suggesting that it may have developed to improve communication rather than to adapt to their environment.
Gaze communication may be an important tool for other canids, including domestic dogs, the researchers claim.
Earlier studies have shown that domestic dogs are more likely to make direct eye contact with humans than wolves raised in the same setting, suggesting they are more in tune with humans.
‘This could mean that after thousands of years of cohabitation, dogs see us in socially useful ways that wolves never will,’ according to a report in the PlosOne blog.