Campaigners who believe that dolphins and whales should be granted rights on account of their intelligence are to push for the animals to be protected under international law.

A group of scientists and ethicists argues there is sufficient evidence of the marine mammals' intelligence, self-awareness and complex behaviour to enshrine their rights in legislation.

Under the declaration of rights for cetaceans, a term that includes dolphins, whales and porpoises, the animals would be protected as "non-human persons" and have a legally enforceable right to life.

If incorporated into law, the declaration would bring legal force to bear on whale hunters, and marine parks, aquariums and other entertainment venues would be barred from keeping dolphins, whales or porpoises in captivity.

"We're saying the science has shown that individuality, consciousness and self-awareness are no longer unique human properties. That poses all kinds of challenges," said Tom White, director of the Centre for Ethics and Business at Loyola Marymount University in Los Angeles.

"Dolphins are non-human persons. A person needs to be an individual. And if individuals count, then the deliberate killing of individuals of this sort is ethically the equivalent of deliberately killing a human being. The captivity of beings of this sort, particularly in conditions that would not allow for a decent life, is ethically unacceptable, and commercial whaling is ethically unacceptable," White said.

The group spoke at the annual meeting in Vancouver of the American Association for the Advancement of Science, to raise support for the declaration among scientists and the visiting public. The 10-point declaration sets out a framework to protect cetaceans' "life, liberty and wellbeing", including rights to freedom of movement and residence in their natural environment, and protection against "disruption of their cultures".

"The next step is taking the science and advocating for law in different places, from a regional point of view, from a national point of view, and eventually from a multinational and international view," said Chris Butler-Stroud of the Whale and Dolphin Conservation Society.

Decades of research on cetaceans, and dolphins in particular, has revealed that their brains, while markedly different from humans, are large, complex and capable of sophisticated behaviour. Observations of dolphins have shown that they can recognise themselves, use tools and understand symbols and abstract concepts.

In 2001, Lori Marino of Emory University in Atlanta, who is promoting the declaration, tested whether dolphins recognised themselves by drawing temporary marks on different parts of their bodies and watching them check the mark by swimming up to an immersed mirror. "When we did that with two dolphins they passed with flying colours," she said.

Orcas off Patagonia displayed a seemingly extraordinary act when an aged member of the group suffered jaw damage and could no longer eat properly. The whale's companions kept the animal alive by feeding it. "The animal, we would say, was past its sell-by date, an older creature. They must have conceptualised that if it wasn't fed, something would have happened to it, and they were able to work out what was needed to keep it alive," said Butler-Stroud.

At the Institute for Marine Mammal Studies in Mississippi, a dolphin named Kelly outwitted its human keepers and passed on some of its tricks to its offspring. Dolphins at the centre were rewarded with fish if they collected litter from their tanks and carried it in their mouths to the staff but Kelly found a weakness in the scheme. When people dropped paper into her tank, she hid it under a rock on the bottom. When a keeper next approached, she swam down and tore a small piece off, and returned to the surface to claim her reward. She worked out that a small piece of paper earned the same reward as a big piece, and so maximised her meals.

Then one day, Kelly managed to grab a gull that flew into the tank. When she delivered it to her keepers, she got an especially large fish reward. The next time Kelly was fed she hid the fish at the bottom of the pool, and later brought it to the surface to lure more gulls into the pool. The strategy proved so successful that she taught her offspring, who went on to teach others.

Though much of the declaration is intended to bring pressure on whaling nations and venues that keep cetaceans in captivity, the document has major implications for conservation programmes and environmental assessments that impinge on communities of dolphins, whales and other cetaceans.

As an early step, the special rights for cetaceans are being considered by the UN as part of its convention on migratory species, which aims to protect migrating species over their entire ranges.

Enshrining the rights in law could be some time, though. "If we are lucky it could take 10 years," said White. "We are at the stage of climate scientists 20 years ago. This is the first step."