The king penguin colony on Ile aux Cochons — a Manhattan-sized island between Madagascar and Antarctica which was believed to be the biggest, untouched penguin colony in the world — has lost 88 percent of its total penguin population in just thirty-five years, according to a new study published in Antarctic Science. An estimated half million pairs of breeding penguins has depleted to just sixty thousand.

The study named the 1997 El Nino event, a reversal of the largest current in the Pacific Ocean that’s naturally-caused but worsened by ocean warming due to human-caused climate change, as the likely leading cause. Ile de la Possession, an island just a couple dozen miles from Ile aux Cochons, experienced a devastating penguin population collapse in 1997 after El Nino ocean temperature changes moved the hunting zone for the penguins further from the island, leaving them unable to gather enough food for their population.

A study published earlier this year found that rising ocean temperatures are shifting breeding grounds on a consistent basis, not just in decadal El Nino events, and severely testing the ability of king penguins to survive. “The cause of the massive decline of the colony remains a mystery, and needs to be resolved,” the study published today reads. “Although the decline started at least 20 years ago, it appears to be ongoing, and the causes of the decline may still be active.”

The island is so remote that all we have to go by is satellite data, which is an incredibly useful tool but can’t tell the whole story. A combination of other factors could have also played into the collapse, such as disease or invasive species like feral cats and house mice could be out-competing penguins for food and attacking chicks. Climate change likely helps invasive species like these thrive. Parasites and ticks that also thrive with climate change could have spread among the penguins. Some of the penguins may have even relocated, as the study notes that a few dozen penguins were found on a previously uninhabited island.

Even if there isn’t a definitive answer, we know that climate change is playing a role in making it more difficult for organisms in the most remote corners of the world to survive — including isolated penguins that will likely never see or meet a human face-to-face.