Big population decline; Several possible causes
SANTA CRUZ, Galapagos Islands, Ecuador — The marine iguana, a coal-black, prehistoric-looking creature found nowhere on earth but the Galapagos Islands, is coping with some difficult times.
Its population has declined by several hundred thousand over the last 15 years, scientists estimate.
“The town was flooded with iguanas when I was growing up,” said Lucas Tario, a 46-year-old baker who grew up in the Galapagos. “Now they’re not as easy to find.”
In 1996, the International Union for Conservation of Nature, with headquarters in Switzerland, listed the marine iguana as vulnerable, one level below endangered. It said the iguanas reproduce slowly and confront many threats.
Jenifer Suarez, a specialist on wildlife surveys at the Charles Darwin Research Center, said a study from 2004 to 2014 at Punta Nunez, about 10 miles east of Puerto Ayora, the main town on the island of Santa Cruz, showed an 18.5 percent decline from 3,200 marine iguanas to 2,609.
As to what is causing the decline, the scientists are stumped.
“We are not really sure,” said Suarez.
Many theories are being bandied about, including changes in the weather, attacks by other animals and the growth of tourism.
The weather phenomenon known as El Nino has always been tough on marina iguanas. El Nino causes warmer-than-usual ocean currents that kill algae, the main food of marine iguanas.
The marine iguana has a one-of-a-kind survival technique. When food is short, it is able to shrink itself by as much as 20 percent by digesting parts of its own bones, scientists say. It is the only animal in the world with that capability. But that’s not enough.
In the last two decades, the frequency of El Nino has doubled and that makes it harder for marine iguanas to recover from each episode.
El Nino is also blamed for negatively affecting the marine iguanas breeding. In the 1982-83 El Nino cycle, as many as 70 percent of some varieties of marine iguanas died, scientists say.
It’s not just the marine iguana whose numbers are down in the Galapagos. Population surveys indicate the blue-footed booby, the Galapagos sea lion and the Galapagos penguins have also been decreasing because of the El Nino phenomenon.
Another explanation for the decline in marine iguanas might be the non-native animals that have been brought to the islands, either intentionally or unintentionally. As far back as the 17th Century, pirates and explorers used the Galapagos as a stop for fresh food and water. The descendants of the animals they had on the ships with them, such as goats, pigs and black rats, roam the islands today. These animals, plus the domesticated dogs and cats that have come along in recent decades, often snatch up the marine iguana eggs and newborns.
Just how much damage the rats and other predatory animals have done is not clear. But the government has killed hundreds of thousands of goats and millions of black rats at a cost of millions of dollars.
But a more recent intruder on the islands is affecting the iguanas: the tourist.
“The most common problem that we have, not only with the marine iguana, but with most animals, are that tourists want to touch them,” said Eduardo Espinoza, an iguana specialist at the Charles Darwin Research Station. The iguana’s stress levels spike when people touch them, Espinoza said.
As recently as the 1960s, only a trickle of back-packers and a few yachtsmen and women were coming to the Galapagos Islands. In 1979, the government says, 12,000 tourists visited the Galapagos. In 2012, immigration officials counted 180,000 tourists. And people who live in the Galapagos say they think well over 200,000 tourists are arriving annually now.
Much of the 51,000 square miles of volcanic islands and ocean in the Galapagos is still pristine. But stretches of Galapagos land that were once occupied only by marine iguanas, giant Galapagos tortoises and other animals have been taken over by restaurants, hotels, souvenir and snack shops, and scuba diving businesses.
People from mainland Ecuador and elsewhere around the world are moving to the archipelago hoping to make money catering to the tourists.
The community of people living the Galapagos has grown from a handful half a century ago to an estimated 35,000, which includes government officials, soldiers, sailors, police and squads of national park guides in khaki shirts and pants. Most of the people live on the islands of Isabela, San Cristobal and Santa Cruz, the main base for many tourists in the Galapagos.
All the commotion, Espinoza said, has been pushing the iguanas away from familiar territory. “If you have a hundred tourists passing and touching the same animal,” he said, “ the animal is going to go away from that place.”
Some conservations worry about the harm to the Galapagos animals from sound and light. Several inter-continental size passenger jetliners roar into the Galapagos every day and a few companies operate shuttle flights around the islands with small twin-engine propeller planes. Most of the boats that take tourists diving and on explorations on land are powered by big outboard motors. Beaches that once were dark after sunset are now often dotted with lights. The iguanas, scientists say, find the lights disorienting.
“They don’t know where the beach is,” Espinoza said, so they cannot swim into the water and find food.
Espinoza has requested extra staff to monitor the iguanas and says that a comprehensive, island-wide population survey is needed.
Espinoza is keeping his eye on the negative trends, but he says he he doesn’t think there is cause to be overly worried. “We do not have enough data to show that it is a major issue,” he said. #