The reindeer did not know they were running out of island
A small herd became 6,000 animals and then almost disappeared. The uncomfortable part is not what happened to them. It is how easy the collapse is to understand from outside the system — and how much harder our own system is to see from within.
In 1944, 29 reindeer were brought to St. Matthew Island in the Bering Sea.They were intended as an emergency food source for a wartime Coast Guard station. The humans eventually left. The reindeer stayed.There were no significant predators. There was a large island covered in food. For the reindeer, things must have looked exceptionally good.Then this happened.
Twenty-nine animals became roughly six thousand.
Three years later, there were forty-two.Before explaining why, I think the graph is worth looking at on its own.From inside that curve, 1963 probably did not feel like collapse. It looked like success.There were more reindeer than ever before.More births. More movement. More animals occupying more of the island. If a reindeer could have measured the health of its society by population growth, it would have been looking at an all-time high.The catastrophe was already inside the success.
What happened
The herd had expanded into an environment with unusually abundant lichen and effectively no predators. But lichen is a slow-growing resource, especially in the Arctic. As the herd expanded, grazing pressure increased and the winter food base was heavily depleted.Then the winter of 1963–64 was exceptionally severe.The crash was not simply one bad winter, and it was not simply one greedy reindeer eating too much lichen. It was the interaction between a population, a slowly regenerating resource, a system with almost no balancing pressure, and an external shock arriving after resilience had already been reduced.The U.S. Geological Survey describes the herd reaching about 6,000 animals at its peak, after the original 29 were introduced in 1944. Later research on island reindeer populations points to depleted winter lichen combined with harsh climatic conditions as the mechanism behind crashes like St. Matthew.
Reindeer on St. Matthew IslandApproximate population counts from introduction to collapse
