London, March 18 (IANS) Though humans wouldn't miss a chance to swim with dolphins, the aquatic mammals don't return the sentiment.

British experts have found that dolphins suffer at the hands of tourists eager to dive in alongside them, reports in.com.

A study of the bottlenose species living off the coast of Zanzibar found the animals were experiencing 'incredible' stress from packed pleasure boats.

'The current situation in Zanzibar is unsustainable. The local community is dependent on tourism - and therefore the dolphins - but unless the activity is regulated, the animals will leave,' said lead researcher Per Berggren, from the University of Newcastle.

'Our study found that whenever the tourist boats were present the dolphins were very unsettled and spent less time feeding, socialising or resting. This has a negative impact, not only on individual animals, but on the population as a whole and long term it could be devastating.

'The problem is that any change needs to be tourist-driven. Many visitors will pay drivers extra in tips to steer their boats in close, herding the dolphins so they can dive right in amongst them. Our message is, keep your distance and put the dolphins first,' he explained.

Around 150 bottlenose dolphins live along the south coast of Zanzibar, where dolphin-watching was introduced in 1992.

Tourism replaced traditional hunting practices which were previously endangering the sea mammals.

'Abolishing the hunts was a major breakthrough and dolphin watching offered a humane, sustainable alternative,' said Berggren.

'Unfortunately, without regulation, dolphin tourism brings with it its own challenges,' he added.

The scientists watched the dolphins over a period of 40 days. They found that when tourist boats were present, the amount of their time dolphins spent resting dropped from 38 percent to just 10 percent. The time they devoted to foraging and socialising also halved.

Meanwhile, time spent on swimming activity more than doubled from 33 percent to 77 percent and dominated dolphin behaviour during interactions with tourist boats.

'Overall, the dolphins are using more energy than they are taking in because they aren't resting or feeding as much but are swimming more as they try to avoid the tourist boats,' said Berggren, who is based at Newcastle University's School of Marine Science and Technology.

'Zanzibar is a wonderful place, the dolphins are incredibly interesting and between July and October there are also breeding humpbacks in the area. I would recommend that anyone go there for a holiday and support the local community but act responsibly and ask operators to follow existing guidelines,' he added. The findings are published in the journal Endangered Species Research.