Daily Times

Swimming with wild dolphins is a regular feature of ‘bucket lists’ – things to do before you die. But “conditioning” dolphins by close human contact may be threatening their survival, a study suggests.

Familiarity with humans is having a host of negative consequences for the intelligent sea creatures. The most serious of which is increasing their chances of getting killed or injured by collisions with boats. When dolphins get used to being fed by people – either directly or indirectly, they lose their fear of people and boats.

Expecting food, they are more likely to swim toward boats which increases the risk of dolphins being hit by the boat or its propellers. It also makes them more likely to become entangled in fishing gear.

Dolphins used to people can also show ‘unnatural’ behaviours such as begging and scavenging and can also become more aggressive, the study said.

As more parts of the world’s coastline become developed, people and dolphins are increasingly sharing the same waters. Scientists in Sarasota Bay, Florida looked at interactions between dolphins and people using a database spanning 45 years.

They said that an increasing number of the long term dolphin community is becoming used increasingly conditioned to human contact. The authors, writing in Royal Society Open Science said, “We found that conditioned animals were more likely to be injured by human interactions when compared with unconditioned animals. This is alarming as conditioning could lead to a decrease in survival, which could have population-level consequences.”

Feeding dolphins is a ‘major concern’ as it ‘encourages unnatural behaviours in wild animals and increases each individual’s risk for injury and death.’

The researchers looked at 32,000 sightings of dolphins involving 1,100 individuals.

Several aggressive incidents involving dolphins have been reported over the years.

Most recently, off the coast of Ireland, a bottlenose dolphin known as Clet dragged a swimmer down into the water – although he fortunately escaped.

Cases of dolphins killing swimmers have also been recorded, as well as dolphins exhibiting aggressive sexual behaviour.

Concerns about feeding dolphins by humans go beyond increasing familiarity.

The US marine conservation authority, NOAA, has reported that people feed dolphins unsuitable food such as hot dogs and chocolate.

Dr Fredrik Christiansen said that swimming with dolphins may not lead to negative results if it does not include feeding the dolphins.

He said, “Conditioning to food provisioning likely occurs because dolphins starts to associate people with food. This is different from swimming with dolphins, where dolphins might become habituated to interactions with humans over time. Sometimes though swim tourism also include feeding animals, which then could become conditioned.”

He said that he did not think it was necessary, however, to feed dolphins to encourage them to swim with people.

He said, “I don’t think dolphins need to be conditioned to allow people to swim with them. Dolphins are very curious by nature and often interact with people because of that. Conditioned dolphins might actually become quite aggressive towards people if you no longer give them food or keep the food away from them.” Meanwhile, separate research has uncovered another threat to wild dolphins: the dolphin variety of measles. A separate study in another Royal Society journal, Biology Letters, studied the unexplained death of 58 bottlenose dolphins.

A study of the dolphin carcases found that measles, known as cetacean morbillivirus, was a major factor in their deaths.