Man’s best friend in the animal kingdom probably doesn’t trust humans unconditionally and it develops a trust deficit, as it ages as well as on the basis on its immediate past experience.

Studying as many as 200-odd stray dogs, a team of evolutionary biologists at the Indian Institute of Science Education and Research (IISER) at Kolkata has found an interesting pattern on what makes or breaks their trust in humans.

Almost 80 per cent of dogs in India are stray dogs and stray dog menace is reported from almost all urban settlements in the country. Significantly, humans are responsible for 63 per cent dog mortality, studies have shown.

While pups, that are still suckling, follow human cues even if they didn’t get any reward, juveniles were reluctant and adult dogs reserved their response based on whether they received any reward on the previous occasion. The idea was to understand how the animals fashion their socio-cognitive behaviour as they age and how their experience, positive or negative, influence it,” said Anindita Bhadra at IISER’s Behaviour and Ecology Lab, who led the study which appeared in the journal PLoS One on Monday.

The study is probably one of the first to explore the relationship between free-ranging dogs and humans in urban and semi-urban settlements.

For the study, the IISER researchers used puppies, juvenile and adult stray dogs. The animals were made to follow the human hand cue to bowls where either a piece of chicken is kept or not.

“We found puppies follow the hand cues most of the times even if there is no chicken piece. The juvenile and adult dogs, on the other hand, did not follow the pointing gesture, chose the bowls randomly,” Bhadra said. When they repeated the trials, the juveniles remained indifferent, but the adults began to follow the human cues provided they were rewarded with a chicken piece on the previous occasion.

The fact that the inexperienced pups follow pointing unconditionally indicates that dogs have an inherent tendency to relate to humans, said Bhadra. However, in the juvenile state, when they begin to forage, they also experience interactions, which can be both positive and negative. These experiences probably make them wary of humans, leading to reduction in trust, she said.

As dogs become adults, there is a remarkable difference in their decision making. “It is as if they develop skills to differentiate between reliable and unreliable humans,” said Debottam Bhattacharjee, a PhD student who works under Bhadra and the first author of the study.

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