Dolphin tours need to ease into the swim

By SIMON COLLINS

New Zealand's lucrative swimming-with-dolphins industry needs to change its practices so as not harm the mammals, says an Auckland University researcher.

Dr Rochelle Constantine estimates that only 450 bottlenose dolphins are left on the North Island's east coast, and that each dolphin now encounters an average of 31 groups of human swimmers a year.

"Often, especially during the holiday months, these dolphins can have extended periods up to a few hours long when there are always boats around them. That is inhibiting their rest."

She says swimmers should slip into the water quietly off to one side of a group of dolphins, rather than jumping into the middle of a pod. Swimming to one side gives dolphins the choice of whether to interact with humans.

Since Dr Constantine started taking photos of the dolphins' dorsal fins in the Bay of Islands eight years ago, she has been out on swim-with-dolphin boats from Doubtless Bay down the Northland coast, around Auckland, Coromandel and Tauranga. The same fins have surfaced everywhere.

"Over the years, almost 100 per cent of the adult bottlenose dolphins I have seen have had markings on their fins, so we have been able to track almost all the adults," she says.

Last week she heard that a group of her aquatic friends turned up for the first time at Onehunga. They must have swum down the west coast and into the Manukau Harbour.

Last week, too, Rochelle Constantine added "Dr" before her name. She outlined the findings from her doctoral research to a meeting in the Bay of Islands on Tuesday.

Although there are more than 120,000 bottlenose dolphins in the world, she says there are just three groups in New Zealand, in the Marlborough Sounds, Fiordland, and a third group which has not been reported south of Tauranga.

"The Bay of Islands is a very important part of this group's home range," she says.

The dolphins eat "constantly" - 10kg of fish a day to feed their average weight of around 300kg. "We have some of the largest bottlenose in the world. Only the west coasts of Scotland and Ireland have larger ones."

They swim in groups averaging 11 adults without calves, or around 20 with calves, and sometimes up to 60.

But they are not family groups. Dr Constantine says they have "a fission and fusion society", with individual dolphins changing groups from day to day or within the same day.

Rearing the calves - and suckling them for three to four years - is entirely a female job. The males do not know which calves they have sired.

"They have a polygamous mating system. Multiple males mate with multiple females," Dr Constantine says.

There is no distinct mating season. It is the "teenage" dolphins, who have been weaned but are not yet sexually mature, who have most fun swimming with humans. Although dolphins live until they are 40 or 50, Dr Constantine found that 76 per cent of the swimmers with humans were aged between four and 10.

"They are like human teenagers, learning the rules of bottlenose dolphin life. They are growing and developing social skills. I think they use the swimmers as part of their play behaviour," she says. "The adult dolphins in general are not so interested. Adult dolphins have other concerns."

However, the adults appear to look on benignly. "I never saw an adult come over or remove a juvenile from a swim situation," Dr Constantine says.

"But remember that juveniles will only contact with the swimmers as long as the group will allow. Often the group will start to move on and the juveniles will join the group. They may get an acoustic signal, or it may be visual."

Over the years, the dolphins have got smarter. Back in 1994-95, 64 per cent of them would interact with swimmers even when the humans slipped into the water right in the middle of a their group. Now that behaviour makes them more likely to scatter.

On the other hand, they are still just as likely as ever to interact with humans if the swimmers enter the water off to one side of the group, giving the dolphins the courtesy of deciding whether to join them.

"The dolphins have, with cumulative experience over the years, made a choice of how best for them to enter the water," Dr Constantine says.

She says the swim-with-dolphin operators have also learnt how the dolphins feel. "They tell people, 'Slip in the water quietly. If you jump in, you'll give them a shock.' They never swim with groups containing calves - it's illegal."

It is also illegal under the Marine Mammals Protection Act 1978 to put swimmers directly in the path of a moving school of dolphins.

In the United States, swimming with dolphins was banned recently after officials consulted Dr Constantine. But she says the ban was necessary partly because the US had not adopted New Zealand-style regulations.

"In New Zealand we are fortunate that we have a small population, and by educating people, and the fact that it is the nature of New Zealanders to spend a lot of time on the water, hopefully people will learn the law and know how to behave," she says.

"We need to start paying more attention to the marine mammal tourism industry. It's a multimillion-dollar industry.

"But as long as we have open relationships between scientists and the companies running these tours - and that is the situation we've had in the Bay of Islands, which has been very much a learning experience for both of us - then we can come up with rules that will improve their practices.

"That's good for business and, most importantly, it's good for the dolphins."

nzherald.co.nz/environment