KEY POINTS:
Orcas are highly social and long-lived: Females can live up to 80 years and males almost 60. But the pods grow slowly because orcas take at least 15 years to mature, the females have calves only every five years or so, and many of the calves die young.
"It's a culture at risk," Roberto Bubas, a ranger with 15 years of experience observing orcas in Patagonia, said of the hunting method, noting that of the seven, only five are teaching the technique to younger members of the pod.
Mel, the 9m male who caught the baby sea lion on the beach, was shadowed by a smaller apprentice, who shared the spoils of the hunt and followed the big expert up near the sand but did not dare to beach himself.
The orcas, sea lions and penguins attracted 340,000 tourists to the Valdes Peninsula last year, when 36 cruise ships made stops nearby, three times as many as in 2002.
"Tourism is growing and growing. It's massive. What we're trying to do is redistribute the tourists," said Sergio Casin, conservation director for protected areas in the southern Argentine province of Chubut.
The government asks tour companies to spread their groups around the peninsula, where they watch penguins and whales from lookout points on cliffs.
Walking on the beaches is prohibited in most of the peninsula's 400,000ha reserve.
"The problem is trying to control all the people who don't know how to respect the animals on the beach," said Juan Copello, whose family own the land at Playa Punta Norte.
People like Copello, who owned land on the peninsula before it became a reserve, are allowed to remain but must work with the government to protect wildlife.
"In places where people always went down to the beach, the animals have moved on and sought quieter areas," said Copello, who runs a small lodge and also observes whales for Punta Norte Orca Research (www.orca-puntanorte.com/index.html), a group led by New Zealand researcher Ingrid Visser.
Only documentary makers, researchers and some journalists are allowed access to the beach at Playa Punta Norte and they must pay for the privilege. The money goes to the provincial government, which administers the reserve.
Mr Casin, of the provincial government, said: "Taking a lot of people there would make the sea lions stampede, which would damage the [whale's] food and the life of the sea lions themselves."
