ISLE ROYALE - Population counts are the foundation of the Isle Royale Wolf/Moose Study.
Even by themselves, the numbers speak volumes about the ecosystem on the island. On Isle Royale, the wolf is the only large predator and the moose is its only prey. Despite this seemingly simple relationship, scientists working on the project have noted great variability over 50 years of the study so far.
"This place is extremely dynamic," study co-director Rolf Peterson said. "Every five years is different from every other five years and the last 25 years were distinctly different from the first 25 years."
The first count, in 1959, tallied 20 wolves and 563 moose on Isle Royale.
At last count, in January, there were 23 wolves and 650 moose on the island. Peterson and co-director John Vucetich said it is impossible to make reliable predictions about the future of the wolf/moose population.
"The science of ecology is starting to look more like history, looking back at the ecosystem we can tell how it got where it is, but we can't tell where it will go because of rare, unanticipated events," Peterson said.
One such event occurred in the early 1980s when an outbreak of canine parvovirus decimated the wolf population on the island.
Wolf numbers dropped from an all-time high of 50 in 1980 to 14 by 1982.
The onset of the disease is attributed to an infected dog that was brought to the island illegally on July 4, 1981.
The peak wolf populations since the parvovirus outbreak were in 2005 and 2006. Researchers counted 30 wolves both years.
"Moose have gone through two big increases and two big decreases," Peterson said.
After gradually climbing from 563 in 1959 to 1,493 in 1972, moose numbers dropped during the rest of the 1970s through several successive severe winters.
In 1981, the population hit 863.
During the years of low wolf population, the moose population rebounded, spiking to an all-time high of 2,422 in 1995.
The pressure this population size put on available food sources, a severe winter, and a growing problem with winter tick infestations, caused the population to plummet to 500 by 1997.
"Moose are low and kind of sputtering along right now and we're not sure which way they're going to go, actually," Peterson said.
Dan Schneider can be reached at dschneider@mininggazette.com