Predators and Prey
Another point along the Rock Harbor Trail at Isle Royale National Park. Isle Royale is a large, remote, isolated island near the northern shore of Lake Superior that should probably be part of Ontario instead of Michigan, but nobody remembered it was there when people were drawing up the maps they used to write the treaties. People--both Native and Euro American--have lived here on occasion, but since it was turned into a national park in 1940, the only people living here even part-time have been a few park rangers and a small number of scientific folks studying the predator-prey relationship between the island's moose and wolf populations.
It's that study that prompted me to go through all my Isle Royale pictures recently. Isle Royale's isolation made it possible to study the predator-prey relationship in a box, so scientists started watching in 1959. Scientists believe moose and wolves have coexisted on Isle Royale a number of times since the island emerged from the ice 11,000 years ago. One or the other population would cross onto the island from Ontario in the winter over ice and stay a while, then either die off or leave. Neither species was on the island when Euro-Americans showed up, though there was a population of caribou that has since gone extinct.
The forebears of the current moose population showed up around 1900, and they spent several decades eating the island bare. A few moose aren't going to have much impact on Isle Royale's vegetation, but the island's big enough to support a couple of thousand. By the middle of the 20th century, the island's fir forests had been decimated. And then the wolves showed up. The first wolves--likely just a single female and two males--crossed over around 1940, and for the next several decades they and their descendants enjoyed what must have seemed an endless feast of moose. There were about 20 wolves on the island when the study began in 1959. At their peak in 1980, there were fifty wolves, and the moose population was in sharp decline. There was some fear among the scientists that the wolves would eat the moose to extinction.
That's when wolf disaster hit, as canine panovirus (accidentally introduced by humans, of course) spread through the population. The wolves--all descended from that single female and two males--proved especially vulnerable to the virus, and by 1982 their number had dropped to 14. The disease passed, but the population never recovered. Inbreeding had weakened the population, and a long period of warm winters without significant ice kept new wolves from coming to the island. The last thirty years of island wolf history has been a long and painful decline.
For a while, things went the other way for the moose, whose numbers exploded to 2,500 by 1996. But then a combination of a lack of vegetation and an explosion in the population of a particular moose tick caused moose numbers to collapse to about 500 in the winter of 1996-1997. This collapse proved another set-back for the wolves, whose population was still fighting to recover from the virus. They suddenly had far fewer moose to eat, which was a second punch in the genetics.
By the time I took this picture in 2011, there were fewer than 10 wolves left on the island. It had become apparent that the wolves weren't going to recover on their own, and the National Park Service had started a vicious debate with itself over what, if anything to do about it.
More to come ...
Predators and Prey
Another point along the Rock Harbor Trail at Isle Royale National Park. Isle Royale is a large, remote, isolated island near the northern shore of Lake Superior that should probably be part of Ontario instead of Michigan, but nobody remembered it was there when people were drawing up the maps they used to write the treaties. People--both Native and Euro American--have lived here on occasion, but since it was turned into a national park in 1940, the only people living here even part-time have been a few park rangers and a small number of scientific folks studying the predator-prey relationship between the island's moose and wolf populations.
It's that study that prompted me to go through all my Isle Royale pictures recently. Isle Royale's isolation made it possible to study the predator-prey relationship in a box, so scientists started watching in 1959. Scientists believe moose and wolves have coexisted on Isle Royale a number of times since the island emerged from the ice 11,000 years ago. One or the other population would cross onto the island from Ontario in the winter over ice and stay a while, then either die off or leave. Neither species was on the island when Euro-Americans showed up, though there was a population of caribou that has since gone extinct.
The forebears of the current moose population showed up around 1900, and they spent several decades eating the island bare. A few moose aren't going to have much impact on Isle Royale's vegetation, but the island's big enough to support a couple of thousand. By the middle of the 20th century, the island's fir forests had been decimated. And then the wolves showed up. The first wolves--likely just a single female and two males--crossed over around 1940, and for the next several decades they and their descendants enjoyed what must have seemed an endless feast of moose. There were about 20 wolves on the island when the study began in 1959. At their peak in 1980, there were fifty wolves, and the moose population was in sharp decline. There was some fear among the scientists that the wolves would eat the moose to extinction.
That's when wolf disaster hit, as canine panovirus (accidentally introduced by humans, of course) spread through the population. The wolves--all descended from that single female and two males--proved especially vulnerable to the virus, and by 1982 their number had dropped to 14. The disease passed, but the population never recovered. Inbreeding had weakened the population, and a long period of warm winters without significant ice kept new wolves from coming to the island. The last thirty years of island wolf history has been a long and painful decline.
For a while, things went the other way for the moose, whose numbers exploded to 2,500 by 1996. But then a combination of a lack of vegetation and an explosion in the population of a particular moose tick caused moose numbers to collapse to about 500 in the winter of 1996-1997. This collapse proved another set-back for the wolves, whose population was still fighting to recover from the virus. They suddenly had far fewer moose to eat, which was a second punch in the genetics.
By the time I took this picture in 2011, there were fewer than 10 wolves left on the island. It had become apparent that the wolves weren't going to recover on their own, and the National Park Service had started a vicious debate with itself over what, if anything to do about it.
More to come ...