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Fauna Series No. 7







Study Area

Isle Royale Mammal History

Methods and Extent of Present Research


Wolf-Moose Coaction




Fauna of the National Parks — No. 7
The Wolves of Isle Royale
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SINCE the study area is isolated, relatively few mammalian species are present. Furthermore, when a species disappears, it may not return for decades, if at all. Thus, significant shifts in species composition have been noted since Adams (1909) published the first list of mammals for Isle Royale. Man's role in these events is not fully known. However, he probably is responsible for exterminating the lynx and marten. The caribou and coyote apparently disappeared for other reasons. No attempt was made during the present study to complete a mammal survey, but incidental observations of mammals were made, and long-time summer residents of the island were interviewed regarding the past status of various species. (One cooperator first camped on Isle Royale in 1902!) Table 3 summarizes the information on shifts in the Isle Royale mammal community.


[X=present; O=not observed]

SpeciesPresent in 1905 InterimPresent status

Woodland caribou
Rangifer caribou
XTo about 1925.O
Canada lynx
Lynx canadensis
XTo early 1930's.O
Martes americana
Canis latrans
Caster canadensis
Alces alces
Red fox
Vulpes fulva
OFrom about 1925.X
Timber wolf
Canis lupus
OFrom about 1948.X
Snowshoe hare
Lepus americanus
Red squirrel
Tamiasciurus hudsonicus
Mustela vison
Long-tailed weasel
Mustela frenata
X?X (Mustela sp.)
Short-tailed weasel
Mustela erminea
X?X (Mustela sp.)
Ondatra zibethica
Deer mouse
Peromyscus manicutatus
Red-backed vole
Clethrionomys gapperi
Little brown bat
Myotis lucifugus
Keen's myotis
Myotis keenii
Big brown bat
Eptesicus fuscus
Silver-haired bat
Lasionycteris noctivagans
Hoary bat
Lasiurus cinereus
White-tailed deer
Odocoileus virginianus
(12 introduced in 1906 eventually disappeared; Cole, 1956.)
Lutra canadensis

a A fragment of skull believed to be from Clethrionomys was found in a fox scat.

b Listed by Burt (1957) for Isle Royale.

c Reported by Johnsson and Shelton (1960).

d See page 20.

The lynx must have been plentiful on Isle Royale, for Adams (1909:413) reported: "Victor Anderson and son, John, secured 48 skins during the winter of 1903 and 1904. Most of these were from about three miles southeast [sic] of the head of Rock Harbor, in the vicinity of Lake Richie." Tracks or specimens were reported from most sections of the island.

Milford Johnson of Amygdaloid Island relates that lynx were being trapped by Bill Lively of the Michigan Conservation Department about 1925. Glen Merritt (Tobin Harbor) believes the species was present until about 1930, and Zerbey (1960:4) wrote that "In the early 1930's the Michigan Conservation Office trapped over 25 lynx." This is the last record of the species on Isle Royale.

Martens undoubtedly were common on the island at one time; Adams (1909:414) wrote: "During the past season [1905] Chas. Preulx took eleven Martens along the Desor trail . . ." Apparently, soon after this, the valuable and easily trapped furbearer disappeared. None of the interviewed early residents remembered the animal, and no other reports or mentions of it were found.

Adams also recorded that residents observed 2 woodland caribou near Blake's Point in the winter of 1904, and 9 on the ice near the Rock Harbor lighthouse in 1905; an ice fisherman about 5 miles out from Pigeon Point, Minn., spied 11 caribou on the ice toward Isle Royale. Julian G. Cross, whose father lived for many years at Silver Islet (near the tip of Sibley Peninsula, Ontario), wrote (personal correspondence, 1961) concerning the movement of caribou: "Previous to 1900, when caribou were abundant, they were often observed on the ice outside of Silver Islet singly, or in small herds. . . . These animals often could be observed traveling back and forth, apparently to Isle Royale, or following the shoreline in both directions."

red squirrel
Figure 14—Red squirrel.

Pete and Laura Edisen observed a band of 14 to 16 on the ice near the Daisy Farm in 1922. Pete also noticed a single animal a few summers later in Conglomerate Bay. Milford and Myrtle Johnson saw caribou as late as 1925. This appears to be the last definite observation of the species on Isle Royale. Cole (1956:53), without giving details, reported that "small numbers of caribou or single animals were seen in 1904, 1915, 1920, 1921, and 1926." It is not known whether the caribou population was resident on Isle Royale or whether small bands merely migrated there from the mainland in winter.

The reason for the caribou's disappearance has not been ascertained. However, the history of the species on Isle Royale correlates well with that on the mainland. Before 1900 the caribou was common in northeastern Minnesota (Swanson et al., 1945) and in Ontario (de Vos and Peterson, 1951; Peterson, 1955), but it began to decline in numbers about the turn of the century (Hickie, n.d.). At present, it is rare along the north shore of Lake Superior. Perhaps the forest fires and invasion by man which occurred in the early 1900's altered the environment too drastically. If the Isle Royale herd was migratory, it also might have succumbed to these factors.

The most abundant mammal on Isle Royale in 1905 (possibly except for the deer mouse) was the snowshoe hare, according to Adams (1909). Commercial fisherman Sam Rude reported that hares were also plentiful in 1911 and 1922, but that since he settled in the southwest section of the island in 1927 he has seen none. Pete Edisen at the northeast end stated that in 1916, when he arrived, hares were abundant and remained so until the 1930's, but since 1936 he has seen very few. Murie (1934) reported hares very scarce in 1930. According to residents of Mott Island, the hare population there was high about 1950, but it decreased markedly by 1955. Cole (1956:53) observed that "the population level in the winter of 1955—56 was considerably below that of the winter of 1952—53."

The earliest record of the red fox on Isle Royale was furnished by Pete Edisen. He remembers seeing wild foxes outside the cages of black foxes raised by Bill Lively about 1925. Murie (1934), working in 1929 and 1930, also observed foxes. Later reports indicate that the population, although persisting, never was high.

Although Adams failed to mention the coyote, Glen Merritt of Tobin Harbor recalls that in 1902 "brush wolves" were plentiful. Mrs. William Lichte, also of Tobin Harbor, heard her grandfather, C. F. W. Dassler, speak of "wolves" on Isle Royale in the early 1900's, but her father, J. C. Dassler, informed her that these were coyotes. Pete Edisen said coyotes were present in 1916 when he arrived; Sam Rude remembers them in 1922; and Milford Johnson reported that they were common in 1925. Zerbey (1960) noted that coyotes were persecuted by residents from 1915 to 1935.

Murie (1934) found coyotes present in 1930, and Hickie (n.d.) stated that about 50 were taken in 1934—35. The occurrence of the species in 1945 was recorded by Aldous (1945), in 1946 by Gensch (1946b), and in 1949 by Krefting (1949b). Cole (1956:53) summarized more information:

Brush wolves trapped in the 1920's are believed to have been coyotes. A number were trapped in the winter of 1928—29 and from fifty to one hundred more the winter of 1934—35. During six months on Isle Royale, two observers saw 18 coyotes in the winter of 1941—42. They were reported plentiful in 1944 and scarce in 1945.

Cole, a National Park Service biologist, did much field work on Isle Royale from 1952 to 1957. During 3 weeks in the park in February 1957, he (1957:37) saw no coyotes and only one track, and concluded: "Apparently the Isle Royale coyote population has declined substantially the last five years." This is also the opinion of most island residents.

Beavers inhabited Isle Royale in the 1800's but apparently disappeared and then reappeared since. According to Adams (1909), the William Ives survey in 1848 indicated the presence of old beaver sign, and island residents in 1878 saw beaver dams and cuttings. Glen Merritt asserts that beavers were present in 1902. However, Adams obtained no recent evidence in 1905 and believed that trappers had exterminated the species. Pete Edisen saw no beavers from 1916 until the early 1920's, when they again were evident. In the southwest section of Isle Royale, Sam Rude noticed them first in 1927. Aerial photos taken in 1930 showed evidence of a small population (Gilbert, 1946).

According to Gilbert, beavers were trapped before the island became a National Park in 1940, and not until 1943 was an increase in the population noticed. "At that time the gradual spread of colonization could be easily discerned. Outlets to inland lakes began to show signs of beaver damming, a few isolated swamps showed beaver work, and dams began to appear in series along the streams." By 1945, beavers had colonized almost every stream, lake, swamp, and bay. Several worked-out colonies were found, and aspen had been depleted severely along many waterways; white birch was being resorted to.

Gensch (1946a) studied 57 beaver colonies and their food supplies in 1946, and Krefting (1963) studied 28 colonies in 1948. Many had been abandoned, and new ones had been established in almost every available location. The latter authors concluded that the food reserve in the center section and especially the southwest section was low; the northeast section had the best reserve. In 1951, Krefting again reported a dwindling aspen supply. Pete Edisen (Rock Harbor) and Sam Rude (Siskiwit Bay) noticed a decline in beaver numbers about 1950, and Cole (1954) found a significant decrease in the population in the Siskiwit Bay region from 1952 to 1954. All island residents interviewed agreed that the beaver population decreased sharply in the 1950's.

Although there is no definite record of the presence of otters on Isle Royale, it seems odd that such an aquatic mammal would not have found its way to the island. Indeed, certain circumstantial evidence was obtained during the present study indicating that otters are present. Milford Johnson reported that in the autumn of 1959 he found several 3- to-4-pound whitefish bitten into while in nets in the mouth of McCargo Cove and around Round Island. This damage sounded like something for which only an otter could be responsible. On August 23, 1960, I found mustelid-like tracks 2 inches long by 2-3/8 inches wide along the outlet of Hatchet Lake, and suspected they were otter tracks. Again, on June 14, 1961, I noted similar tracks on the beach at the head of Conglomerate Bay. These, too, looked like otter tracks I have seen on the mainland. A final piece of evidence came from Lt. Comdr. C. G. Porter, skipper of the U.S. Coast Guard's Woodrush, who observed what he believed to be an otter in Washington Harbor on June 17, 1960, for 10 minutes at a distance of 75 feet. Porter is familiar with both beavers and mink and was certain the animal was neither of these. Nevertheless, it remains for future studies to gather in disputable evidence.

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