Author: Jennifer Carpenter

Seals can identify a single star in the night sky and navigate by it, scientists have discovered.

Navigating in the open ocean is essential for seals to move between foraging grounds that may be hundreds of kilometres apart.

This is the first evidence that marine mammals, like humans, use stars to navigate in open water, say scientists.

The European team has published details of its work in the journal Animal Cognition.

The researchers, headed by Dr Guido Dehnhardt of University of Rostock in Germany, simulated a night sky above two captive male seals and monitored the movements of the animals through six hidden infrared cameras.

“Initially, the seals were guided to one of the brighter stars by a laser pointer, and encouraged to swim towards it,” said Bjorn Mauck of the University of Southern Denmark and one of the team-members.

Wild Seals

Once the seals got the hang of navigating by the one star, the night sky above them was swivelled around and the seals were watched to see if they could still orientate themselves.

“With a little practice the seals swam in the right direction 100% of the time,” said Dr Mauck.

In the wild, seals’ foraging trips can take several days and so they often find themselves in open water with no visible landmarks for nights on end. How these wild seals learn the relationship between a star and their feeding ground is still unknown.

Hard work for captive seals used to study animal navigation

“Seals might learn the position of the stars relative to foraging grounds during dawn and dusk when they can see both the stars and landmarks at the coast,” suggests Dr Mauck.

The researchers think that marine mammals might use star paths, or “kaveingas” as Polynesian seafarers call them.

These people navigate by heading towards a star on the horizon until it moves too high to see, and then swap over to follow another star, and so on, guiding their way until dawn.

Seals, sealions and whales are often seen elevating themselves out of the water as they swim in open ocean. This act of coming out of the water vertically and staying above the surface momentarily, in the same way a human treads water, could allow marine mammals to set their course, the researchers speculate.

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Yawning is known to be contagious in humans but now scientists have shown that pet dogs can catch a yawn, too.

The copying activity suggests that canines are capable of empathising with people, say the researchers who recorded dogs’ behaviour in lab tests.

Until now, only humans and their close primate relatives were thought to find yawning contagious.

The team – from Birkbeck College, University of London – reports its findings in Biology Letters.

Yawning, although sometimes a response to extreme stress, is more often a sign of tiredness; but the reason for why yawning is catching is not fully understood.

Human cues

There is evidence that autistic individuals are less inclined to yawn into response to another human yawning, suggesting that contagious yawning betrays an ability to empathise, explained Birbeck’s Dr Atsushi Senju.

Dr Senju and his team wondered whether dogs – that are very skilled at reading human social cues – could read the human yawn signal, and set out to test the yawning capabilities of 29 canines.

The team created two conditions, each five minutes long, in which a person – who was a stranger to the dog – was sat in front of the animal and asked to call its name. Under the first condition, the stranger yawned once the dogs had made eye contact with them.

“We gave dogs everything: visual and auditory stimulus to induce them to yawn,” Dr Senju, told BBC News.

Under the second condition, the same procedure was followed, but this time the stranger opened and closed their mouth but did not yawn.

This was a precaution to ensure that dogs were not responding to an open mouth, explained Dr Senju.

Yawning yet?

The team found that 21 out of 29 dogs yawned when the stranger in front of them yawned – on average, dogs yawned 1.9 times. By contrast, no dogs yawned during the non-yawning condition.

The researchers believe that these results are the first evidence that dogs have the capacity to empathise with humans; although the team could not rule out stress-induced yawning – they hope to in future studies.

“Dogs have a very special capacity to read human communication. They respond when we point and when we signal,” Dr Senju told BBC News.

The researchers explained that along with floppy ears and big soppy-eyes, humans have selected dogs to be obedient and docile. The results from this study suggest the capacity for empathy towards humans is another trait selected in dogs during domestication.

Dr Senju thinks that these traits would have been useful to humans when they began to live side-by-side with canines approximately 15,000 years ago.

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