Wolves and Moose on Isle Royale

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The vast wilderness of Isle Royale, and the surrounding islands that constitute the national park harbors a relationship between wolves and moose that is unlike any other in any area in the world. Because Isle Royale is an isolated island, the two species are able to be studied with virtually no factor of human interaction, as the island is protected by its national park status, and also, know factor of wildlife immigrating to, or emigrating from the island. The unique single predator-single prey relationship, where wolves are the only predator of moose, and moose are almost exclusively the only prey for wolves, lends unparalleled research to the study of predator-prey relationships, and the causation of the fluctuation of the two populations. Because this research is so valuable to the understanding of the interaction of predator-prey relationships, it should be recognized and valued as such. If anything should cease the existence of one or both of the two species on the island, they should be reintroduced without hesitation in order to further advance the research of the interaction between the two species.

Isle Royale is a national park that is made up of several islands (about 200), and is in the northwest portion of Lake Superior. It is about fifty miles from Michigan’s shore, and twenty-two miles from the Canadian shore. The main island is forty-five miles long, and nine miles wide approximately (at the widest point), with an area of 205 square miles. Isle Royale is twenty-two miles off the Canadian shore, and fifty off Michigan’s shore. There are no roads, and no motorized vehicles are allowed on the island. Because there are no roads, nor any residential area, ninety-nine percent of the land on the island is wilderness. The remoteness of Isle Royale leads to it having fewer visitors in one year than Yellowstone National Park has in just one day.^[1]

The relationship between wolves and moose on Isle Royale has been studied and researched for an unprecedented amount of time, which provides a rich background of research that aids in the better understanding of the two species and their interaction. The continuing 47-year study is the longest study of either wolves or moose ever.^[2] Because of Isle Royale being an isolated island, neither wolves nor moose were there initially. Moose swam across Lake Superior from Minnesota in the early 1900s.^[3] For nearly fifty years the moose thrived, having no predator to stump their population growth. Until in 1949 when a pair of wolves wandered across an ice bridge made to the island during a harsh winter from Ontario.^[4] But because only one pair of wolves migrated to the island, inbreeding has posed problems to the species existence. As Rolf Peterson, a professor at Michigan Technological University and the lead researcher of the unique relationship between the two species on the island says, "Moose were isolated here 100 years ago. Most of the genes are still here, but they have enough population (to compensate). There are so few wolves that they have lost genetic variability. The scientific dogma suggests that they are not going to make it."^[5] In fact, all of the wolves DNA on Isle Royale can be traced back to one ancestor.^[4] The lack of genetic variability leads to inbreeding, and inbreeding in turn leads to mutations and fitness problems. Wolves with mutations often receive ridicule from other members in the pack, and are violently harassed, and sometimes killed because of their differences.^[5]

The populations of wolves and moose on Isle Royale fluctuate between each year. Though when initially studied, many researchers believed the two species would eventually reach an equilibrium (which is believed to be about twenty-five wolves, and 1,500 moose), they haven't, and probably never will.^[6] The highest number of moose on Isle Royale since being researched with the interactions of wolves was 2,442 in 1995. The highest number of wolves ever recorded on the island was fifty in 1980. The most dramatic decrease in the wolf population occurred when the canine parvovirus was spread to the wolves on the island, when a visitor brought its dog over (breaking the rules of the national park) in 1980 or 1981, causing a crash in the population from '80 to '82.^[4] The population fell from fifty in 1980, to a very low fourteen in 1982. The population of the two species as of 2005 was 540 moose, which is an all time low, and thirty wolves, which is considered pretty high.

The density of the two species is very much dependent on the density of proper forage (the vegetation that animals feed on). Because a moose's diet is 59% balsam fir, any change in its density affects the density of moose.^[7] The consistent presence of moose on Isle Royale since 1900 has led to a dramatic decline in understory growth of balsam fir. As of 2002, understory growth of balsam fir was at five percent, which is down forty-one percent from numbers in the 19th century, when it was recorded at forty-six percent.^[5] The reliance of moose on balsam fir has led to a much higher concentration of the species on the east side of the island, where the plant is more plentiful.^[8] Unfortunately, birch and aspen trees, which are much healthier for moose used to grow plentifully on the island, but have now mainly been replaced by the less nutritious balsam fir. Because balsam fir does not fulfill the amount of moisture moose need in their diet, they have recently been spotted eating snow, which is a very rare occurrence.^[6] They have also been sighted eating lichens, which is another very strange occurrence, by Rolf Peterson, who says that eating lichens is similar to eating dust.^[6] When the moose population is very high, then the density of balsam fir crashes, which leads to a crash in the moose population. This leads to the continuing "see-sawing" of the moose population on the island. Crashes in balsam fir growth lead to malnutrition, which is one of the most common killers, both directly and indirectly of moose. When there are too many moose for the amount of balsam fir, then many moose, especially young moose become plagued with malnutrition, which leads to arthritis. Moose commonly die either directly from malnutrition, or, because they become emaciated, and slowed down by arthritis, they are picked out by wolf packs as easy prey, and are killed. The most common causer of malnutrition in moose is when calves are born during a winter with deep enough snow that browsing for proper forage is very difficult.^[7] The moose population should be able to rebound soon, because there aren't as many moose as their have been in the past, which will allow for the balsam fir to grow back.

Wolves use their intelligence to pick out easy moose prey, which they can outrun, and bring down. They do not go after healthy moose, unless they are completely desperate; a healthy moose in its prime years is very tough for any wolf pack to bring down. Also, moose in their prime years commonly can simply outrun wolves in a hunt. As Rolf Peterson puts it, "moose can trot through two feet of snow at twenty miles per hour. That's faster than the world champion cross-country skiers. Wolves cannot keep up if the snow is soft."^[3] Even if wolves can catch up to a moose, they cannot always bring it down; researchers have found many bruises and scars on wolves that have not been successful when trying to kill healthy moose.^[5] Wolves pick out young moose calves, old moose, or moose plagued with disease or injury in order to increase their chances in successfully killing one. The typical moose that a wolf kills is about 12 years old, and suffers from arthritis, osteoporosis, or periodontal disease, and in some cases all of them.^[9] Though moose are often infected by various diseases, approximately eighty to ninety percent of moose deaths on Isle Royale are a direct result of wolves killing them.^[10] Rolf Peterson believes that the wolf population is in trouble in the future, because in his words, "wolves feast mostly on calves and elderly moose, both of which are in short supply." Because moose make up ninety percent of an Isle Royale wolf’s diet (the other ten percent being snowshoe hare and beaver), finding a young, old or sickly moose is imperative for survival.^[2] The average amount of moose a wolf kills a month is between .44 and 1.69.^[11]

Nearly the entire wolf population (with the exception of a few loners and separate pairs) on Isle Royale is separated into three packs; the East pack, the middle pack, and the Chippewa Harbor pack.^[12] Wolf packs on the island have historically been separated into three or four packs, with each pack usually having anywhere from three to eight members, two to three of those being pups. The amount of wolves in a pack is primarily determined by the amount of snow that falls in a given winter. Packs are comprised of about four to five wolves in less snowy winters, to about twelve during very snowy winters. This can be explained by the fact that pups stay with their packs during heavily snowy winters, instead of leaving the pack like they would normally do during less snowy winters to find a mate. If a pack dissolves (from many of the pack members dying), it takes less than a year to form a new one. One pack will dissolve about once every three years.^[11] Wolf packs are designed to increase wolves’ chances in killing and feeding on moose; because a moose is nearly impossible for one wolf to bring down by itself (unless on the verge of death already), a pack of wolves is virtually the only way for wolves to efficiently kill a moose. Once a moose is brought down and killed, wolves have to compete with scavenging ravens. Because ravens are tenacious scavengers that can easily dodge the strike of a wolf, and are unbothered by them, packs are used by wolves in order to increase the amount of meat they get from a moose. Ravens can eat and store up to two pounds in a few days, which is very minuscule compared to the storage capacity of wolves, which is up to eighteen pounds in just a few hours.^[11] An Isle Royale wolf pack usually kills one moose for anywhere from four to ten days during the winter.^[11] In order to increase the amount of moose they can kill, wolf packs on the island have been known to fight in attempt to further their territorial reign. Recently, the East pack killed Chippewa Harbor pack's alpha male, as witnessed by John Vucetich, a professor at Michigan Technological University, and one of the lead researchers on the island, who believes that the Chippewa Harbor pack is now in grave danger of dying off without their leader.^[12]

Other animal species have an affect, though rather small, on the relationship between wolves and moose on Isle Royale. Before wolves hunted them to extinction, researchers believe that coyotes, which would serve as a good alternate food source for wolves, used to inhabit the island. Beavers and snowshoe hares also have an affect on both populations, because beavers and snowshoe hares are the only two animals that wolves prey on excluding moose, constituting ten percent of an Isle Royale wolf's diet.^[2] Unfortunately, the beaver population has sharply declined since the arrival of wolves, but they still are present, and though they are not a prime food source for typical wolves, they are the second to moose as the most consumed animal by the wolves on the island.^[13] Beavers benefit both species, because they create aquatic macrophytes, which are very nutritional plants for moose, because they are a key source of sodium, and they serve as easy prey for wolves. Unfortunately for the moose, beavers themselves also consume the macrophytes they create.^[7] Though wolves are thought to contribute to the decline in beaver, researchers believe that the decline of aspen, the primary food source of beavers, which used to be plentiful, could have led to their decrease. Beavers have been exposed to predation by having to travel long distances to find only parts of the island where aspen remains. Snowshoe hares, the third most consumed animal by wolves on Isle Royale constitute a very small portion of the wolves’ diet, because snowshoe hares are so difficult to catch. Researchers have found that wolves do not show much interest in preying on hares, and only feed on them incidentally.^[13] Snowshoe hares have a negative affect on moose as they eat some of the same vegetation that moose eat, which only contributes to the decline in appropriate forage for moose.^[7] Red foxes are yet another animal that inhabits Isle Royale; they mainly feed on snowshoe hares and occasionally scavenge on moose, or any other meat a wolf leaves behind. Wolves do not commonly kill foxes, though wolves have been observed killing foxes when they attempt to feed on an animal carcass.^[13] A healthy population of each of these animals on Isle Royale will help preserve both wolves and moose, and the unique relationship they have with each other.

Climate affects the balance between the unique single predator, single prey relationship between wolves and moose on Isle Royale more than any other variable. Since El Nino hit in 1998, the climate has warmed up, which has significantly affected the moose population on Isle Royale, and across North America.^[14] The warmer climate in recent years has produced more ticks, which feast on the flesh, and bight off the hair of moose, which makes them more susceptible to anemia (a lower than normal amount of red blood cells), and hypothermia for moose.^[14] A moose can have tens of thousands of ticks feeding on its blood at one time. Each of those ticks can suck up to one cubic centimeter of blood. The biting ticks cause a lot of discomfort for the moose, so they try to get the ticks off of their bodies by biting off of their hair, and rubbing up against trees. This preoccupies moose, and keeps them from browsing for food, which can lead to problems with malnutrition, making the moose weaker, and easier for wolves to bring down. Ticks bight out hair, and suck out the blood of moose; hair and blood loss emaciate moose, which makes them more vulnerable prey for wolves.^[15] Ticks have been a major problem for moose on Isle Royale since the climate has recently warmed up. Ticks are more prominent in years where spring arrives earlier than usual, because if when they fall on the ground when their isn't snow, then they can reproduce, otherwise, they die out.^[16] Then, if the summer is hot, ticks are able to reproduce at a higher rate. Hot summers also lead to moose resting in the shade, or in the water to keep cool, making them easier prey for wolves. Also, hot summers lead to tougher foraging for moose which makes them less prepared and more vulnerable to the winter. Not only has the recent warming of Isle Royale hurt the moose, but completely opposite problems harm them also. Harsh winters pose significant problems to moose, and the unique relationship they have with wolves on Isle Royale, because moose have problems finding food when there is too much snow on the ground.^[9] The less snow there is, the more freely moose can move around the island. When there is a significant amount of snow, moose stay in conifer swamps, making them easier prey for wolves, because they are more stagnant.^[12] Deep or heavy snow decreases the speed and agility of moose that is necessary to evade wolf attacks. Calves born during a winter with particularly deep snow are more vulnerable to being weaker prey for wolves later on in their lives because of foraging problems that surface when the snow is deep.^[7] The keen survival instincts of moose have been clearly evident from the studying of their actions on Isle Royale. Cow moose (female moose) have been spotted on nearby smaller islands, around the main island of Isle Royale, because they swim across to give birth. This allows for them to give birth and raise their young without the threat of wolves preying on their young when they are vulnerable. Once the calves are physically mature, they are able to swim back, and are then able to better protect themselves from wolves, as they are then in their prime years.^[5] This practice should help the moose population rebound in the future.

The future of the unique single predator, single prey relationship between wolves and moose on Isle Royale is in jeopardy due to aforementioned problems. Most of these problems are climatic, resulting either harsh winters or warm summers, resulting from the problem of global warming. This problem is threatening the lives of many species around the globe, and specifically those on Isle Royale. Because the moose population is at an all time low since being studied, scientists expect that the wolf population will decline due to the lack of prey, which will lead to a rebound in the moose population).^[6] The normal ratio of moose to wolves is forty or fifty to one, whereas in 2005 it was fifteen to one. This imbalance should allow the moose population to increase.^[3] Also, because of the low moose population, forage is given the opportunity to grow back, which will help the moose population to rebound.^[16] Though global warming has been and most likely will keep the moose population from returning to the booming populations in the two thousands that it used to have, the wolf population is in greater danger. As aforementioned, the lack of genetic diversity in wolves, and the decline of the moose population could lead to serious problems in the future. Rolf Peterson believes that the wolf population has a strong chance of dying out in the future. If this should happen, he feels that they should be reintroduced, in order to further study predation, as it is a natural process.^[7] The isolated wilderness of Isle Royale provides an opportunity unlike any other to study predator-prey relationships in their purest form; the unique single predator-single prey relationship between wolves and moose on the island is found nowhere else in the world. This research is invaluable to the understanding the natural process of predation, and the interactions of predator-prey relationships. Natural and unnatural factors are presently, and could in the future threaten the existence of one or both of the two species. If either or both of the species become extinct on the island, they should be reintroduced to restore the natural interaction between both of them. The benefits of preserving the unique relationship between wolves and moose on Isle Royale heavily outweigh the cost, and time needed to maintain what is the only study of a single predator-single prey relationship in the world.

Contents 1 See also 2 External links 3 Notes 4 References

[edit] See also

• Predator
• Prey

[edit] External links

• The Wolves and Moose of Isle Royale

[edit] Notes

1. ^ Holliday, Michael E., and Grant H. Fenner. "Isle Royale National Park." Paddling.Net. 31 Aug. 2001. 18 May 2006
2. ^ ^{a b c} "Overview of the Ecology and Research of Wolves and Moose on Isle Royale." The Wolves and Moose of Isle Royale. 16 Apr. 2006 [1]
3. ^ ^{a b c} Flesher, John. "Biologist Never Tires of Watching Wolves, Moose on Isle Royale." StarTribune 23 Mar. 2006. 9 Apr. 2006
4. ^ ^{a b c} Line, Les. "In Long-Running Wolf-Moose Drama, Wolves Recover From Disaster." The New York Times 19 Mar. 1996. 3 Apr. 2006 [2]
5. ^ ^{a b c d e} Weier, Anita. "Isle is Perfect Laboratory for Moose and Wolves - Their Interactions Studied Since 1958. (Saturday Extra)" The Capital Times (Madison, WI) (May 31, 2003): 1B.
6. ^ ^{a b c d} Myers, John. "Isle Royale's Moose Numbers Continue Crash." Duluth News Tribune 10 Mar. 2006. 2 Apr. 2006
7. ^ ^{a b c d e f} McLaren, B.E., and R.O. Peterson. "Wolves, moose, and tree rings on Isle Royale. (Isle Royale National Park, Michigan)." Science 266.n5190 (Dec 2, 1994): 1555(4).
8. ^ Wilmers, CC, ES Post, RO Peterson, & JA Vucetich. 2006. Disease mediated switch from top-down to bottom-up control exacerbates climatic effects on moose population dynamics. Ecology Letters 9: 383-389.
9. ^ ^{a b} "Isle Royale is a study in moose and wolves." Akron Beacon Journal (Akron, OH) (Dec 29, 2005): NA.
10. ^ Peterson, R.O., R.E. Page, and K.M. Dodge. "Wolves, moose, and the allometry of population cycles." Science 224 (June 22, 1984): 1350(3).
11. ^ ^{a b c d} Vucetich, JA & RO Peterson. 2004. Long-term population and predation dynamics of wolves on Isle Royale. Pages 281-292 in Biology and Conservation of Wild Canids, edited by D. Macdonald & C. Sillero-Zubiri, Oxford University Press.
12. ^ ^{a b c} "Moose population decline leaves Isle Royale wolves scrapping for food." The America's Intelligence Wire (March 11, 2006): NA.
13. ^ ^{a b c} "Species of Lesser Significance." ParkNet. 4 July 2002. National Park Service. 18 May 2006
14. ^ ^{a b} "Predators and prey affected by warming.(Ecology)(decline in numbers of North American moose, increase in number of wolves)(Brief Article)." USA Today (Magazine) 133.2711 (August 2004): 7(1).
15. ^ Goodrich, Marcia. "Isle Royale Wolf-Moose Study Report." Michigan Tech News/Media. 4 Mar. 2004. Michigan Technological University. 3 Apr. 2006
16. ^ ^{a b} Roach, John. "Wolves, Ticks, Send Michigan Moose Numbers Plummeting." National Geographic 6 June 2005. 5 Apr. 2006

[edit] References

• "Food Fight: Wolves Pack Up to Out-Eat Ravens." Ascribe Higher Education News Service (August 19, 2004): NA.