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NUMBER 109 FEBRUARY 25, 1922

OCCASIONAL PAPERS OF THE MUSEUM OF ZOOLOGY

UNIVERSITY OF MICHIGAN

ANN ARBOR, MICHIGAN PUBLISHED BY THE UNIVERSITY

NOTES ON THE MAMMALS OF GOGEBIC AND ONTONAGON COUNTIES, MICHIGAN, 1920

BY L. R. DICE AND H. B. SHERMAN

The authors of this paper spent the summer of 1920 in western Michigan studying the mammals of the region for the Michigan Geological and Biological Survey. From June 25 to August 4 was spent in the Cisco Lake Region with headquarters on Lindsley Lake; August 6 to August 20 a camp was maintained in the woods four miles southeast of Little Girl's Point; and from August 20 to September 6 was spent working from a camp on the western shore of Lake Gogebic, about three miles south of Lake Gogebic Station. The first two camps were in Gogebic County, the third in Ontonagon County.

The field work was performed jointly by the two authors, under the direction of the senior author, who is responsible for the identification of the species, the descriptions of the general areas and of the habitats, and is jointly concerned in writing the annotated list.

In addition to our own records, we have secured many valuable notes on the distribution of the larger species from J. E. Fischer, of Merriweather, Ontonagon County, a trapper of many years' experience; and from Benjamin J. Twombley, of Bent's Resort, Wisconsin, who has made many observations on the mammals of the Cisco Lake Region. We have also added a number of records from J. E. Marshall, who trapped for many years, beginning 1884, in Ontonagon and Gogebic counties, and from Ole Petersen, at one time a trapper at Gogebic Lake.

The habitats in which records of occurrence have been obtained for the region under consideration are listed under each species; and the number of individuals taken, or seen and positively identified, in each habitat are given. From the figures a rough estimate of the relative abundance of the various species in the different habitats can be obtained, but the various habitats were not trapped or studied equally intensively, and for the larger and the rarer forms the numbers give little dependable data on relative abundance.

DESCRIPTIONS OF THE REGIONS STUDIED

_Cisco Lake Region._ In the Cisco Lake Region there are many lakes, mostly small, but several of a length of one to three miles. The water-level in the Cisco Lake chain has been raised six or ten feet by a dam across the outlet, and this change in water-level has killed the trees along the lake borders, so that the lakes are fringed by a narrow line of dead trees. The habitats of emerging vegetation and of aquatic vegetation have been much altered by the change in water-level, and these habitats cannot be well studied in these lakes. However, the neighboring lakes in which the water-level has not been changed show that the forests of the region originally came down to the water's edge, and that there was little normal development of marsh or swamp.

The ridges between the lakes rise in general to heights of twenty-five feet or more, though bluffs are not formed. These ridges are mostly covered by mixed hardwood forest in which the hard maple, yellow birch, hemlock, and linden are the dominant trees. There are numerous small wet depressions, some of them containing small black spruce bogs, while others include a few arbor-vitae mixed with linden and other typical trees of the wet hardwood forest. Small areas of nearly pure hemlock occur on some slopes near the lake shores. A few large tamarack bogs are present.

Though the pines formerly occurring have been taken out, the region otherwise is in nearly its native condition. A few former clearings along the lake shores have grown up to brush or to white birch saplings or small trees.

_Little Girl's Point Region._ Much of the region in the near vicinity of Little Girl's Point has been cleared or burned, but a few miles to the east and southeast there are still considerable areas of native forest. The high ridge running through the region bears a splendid forest of maple, yellow birch, and linden, with little if any hemlock. However, on the steeper lower slopes hemlock occurs in nearly a pure stand. At one place was found a nice grove of large white pines, mixed, on the lower edge of the slope, with a few hemlocks. Black spruce-tamarack bogs are extensive and arbor-vitae swamps occur commonly. The extensive burned areas south of the point have grown up to a thicket of aspen, birch, and various shrubs and saplings. A few small areas are under cultivation.

_Region at the north end of Gogebic Lake._ Most of the region about the north end of Gogebic Lake is low and wet. A number of small black ash swamps occur near the lake, and further back there are extensive black spruce bogs. The main forest is of a much mixed wet hardwood type, sugar maple, linden, yellow birch, elm, and hemlock, being the dominant species. The forest in most places reaches the edge of the lake, though a few sandy beaches occur. However, the level of the water in the lake has been raised a few feet by a dam across the outlet, and beaches were probably more abundant before this occurred. The lake is so large, about 13 miles long by 1 to 2 miles broad, that wave action is quite pronounced.

One beaver meadow was studied, this meadow including areas of grasses and of sedges, traversed by ditches, small mud-flats covered with low rushes, and alder thickets.

Just north of Lake Gogebic Station there are some high hills having bluffs on the southern exposures. These hills were visited, but they had been extensively logged and burned over and no attempt was made to trap for mammals on them.

Some large burned areas have grown up to sapling forests of aspens. Near the towns of Lake Gogebic and Merriweather nearly all the forests have been cleared away, but farther south on the sides of the lake the woods are still in their natural condition.

HABITATS

The habitats studied in Gogebic and Ontonagon counties may be listed as follows:

Exposed shores: Open-water Beach Dirt-bluff Forest--shore

Protected shores: Water lily Pondweed Rush Submerged-sedge Cat-tail Willow-thicket Mud-flat

Meadow: Ditch-border Tall-sedge Grassy-meadow Alder-thicket

Swamps: Black ash swamp Arbor-vitae swamp

Bogs: Leather leaf bog Sphagnum bog Black spruce--tamarack bog

Forests: Hemlock forest White pine forest Wet hardwood forest Dry hardwood forest

Mountains: Rock-bluff Mountain-heath

Air: Aerial

Burns and clearings: Herbaceous stage Shrub stage Paper birch--aspen stage Young hardwood forest stage

Artificial conditions: Overflow swamp Cultivated-field Edificarian

This list of habitats is admittedly not complete for the regions visited, but is intended to include those which we studied. We had no opportunity of studying either the shores of a large river or jack pine ridges, both of which situations will undoubtedly have habitats not here recognized.

The habitats studied in Gogebic and Ontonagon counties but every habitat has been listed which seems to form a distinct type of mammal environment. We are firmly convinced that it is better to describe a great number of habitats rather than to lump different kinds of environments together. It is infinitely easier for a later worker to combine several habitats, which have been split too finely, than it is to separate the component habitats which may have been lumped together under one name.

No attempt is made to give complete lists of the plants found in each habitat, but only the more conspicuous plants or those of special importance to the mammals are mentioned. The plant names used are mostly taken from Darlington's list of Gogebic County plants.[1]

_Exposed Shores_

_Open-water habitat:_ This habitat includes the areas of open water with no rooted vegetation in the deeper parts of the lakes and rivers. On Lake Superior at Little Girl's Point this habitat comes directly to the beach, for the wave action on this exposed point is sufficient to prevent the growth of plants along the shore. In Gogebic Lake and in the smaller lakes of the Cisco Lake Region there are also many parts where there is no rooted vegetation along shore. This habitat, therefore, covers by far the larger part of the aquatic conditions of northwestern Michigan. We secured no records of mammals for this habitat, and, though some aquatic species must occasionally occur in the open water along lake shores, they are rare there, and are practically absent from the areas of open water farther out in the lakes.

_Beach habitat:_ The shore of Lake Superior at Little Girl's Point is subjected to heavy pounding by the lake waves, leading to the formation of a well-developed beach. To the east of the point the beach for some distance is five to ten yards wide, mostly of small gravel, with sand on the upper part; it ends abruptly against a steep dirt bluff. On the beach no vegetation grows and only a few scattered drift logs occur. To the west of Little Girl's Point undetached masses of solid rock are more prominent, though small patches of gravel occur in partially protected places. The beach here in general is narrow and rises steeply, so that the different beach zones, lower, middle, and upper, are not well marked. On the shores of Lake Gogebic are a few small sand beaches; but around this lake, as well as around the smaller lakes of the region, the forest comes, in general, directly to the edge of the water. There was no opportunity to trap for mammals on a beach, and no records for the habitat were obtained.

_Dirt-bluff habitat:_ To the east of Little Girl's Point the beach of Lake Superior runs along the base of a dirt bluff about 35 feet high. The storm waves of winter evidently wash against this bluff, eroding it away and destroying the forest, which is of the hemlock type, growing on the level above. The bluff is quite steep, and along with small exposures of bare clay bears a number of scattered herbs and a few shrubs and small trees, such as alder, willow, arbor-vitae, yellow birch, paper birch, and red maple. No collecting was done in this habitat and no records of mammals were obtained from it.

_Forest--shore habitat:_ Along all the lakes of the region, except Lake Superior, the forests in general come down to the water's edge. The marginal forests are frequently dominated by hemlock, though often a wet hardwood forest occurs along the shores, and in a number of places along Gogebic Lake black ash swamps border the water. Red maple (_Acer rubrum_) and mountain ash (_Sorbus americana_) frequently occur along the exposed shores of Gogebic Lake. Frequently young forests of paper birch or quaking aspen have replaced the original forests in the clearings and burned areas along the lake borders. The shore beside a forest commonly rises abruptly a few inches to a foot or more in a firm bank, and in most cases the trees overhang the water to some extent. These shores are the favorite promenade of the porcupine; and the mink, muskrat, and otter are typical of the habitat.

_Protected Shores_

_Water lily habitat:_ In shallow, protected parts of the lakes and channels of the Cisco Lake chain there are extensive growths of white and yellow water lilies (_Castalia tuberosa_ and _Nymphaea advena_). Water lilies also occur in many places as a narrow border at the edge of deep water. Muskrats were the only mammals noted in this habitat, but mink and otter probably occur also.

_Pondweed habitat:_ A thick growth of pondweeds (Potamogeton spp.) occurs in protected places along the shores in many parts of the lakes of the Cisco Lake chain. Muskrats were noted in this habitat. In Gogebic Lake the exposure to wave action is in most places too great for a good development of pondweeds, though in the northern end of the lake there are a number of widely scattered plants of this type, but not forming a very well marked habitat.

_Rush habitat:_ On somewhat protected shoals, both in the lakes of the Cisco Lake Region and in Gogebic Lake, there is sometimes a growth of rushes (Juncus sp.). Along the lower course of the Merriweather River, just before it enters Gogebic Lake, rushes thickly cover numerous small areas. The plants in both cases grow partly submerged in the water. No records for mammals were obtained from this type of habitat, though doubtless some of the amphibious forms frequently occur here.

_Submerged-sedge habitat:_ Sedges in general do not occur as a definite belt about the margins of the lakes in the region studied. The only place where any considerable growth of sedges was noted at the edge of the water was along the lower course of Merriweather River, just before it enters Gogebic Lake. Here there are considerable areas of sedges partially submerged by the water. No records of mammals were obtained from this habitat.

_Cat-tail habitat:_ Under native conditions cat-tails (_Typha latifolia_) apparently do not often form extensive habitats in the region. Along the marshy borders of the lower Merriweather River at Gogebic Lake a few small patches were seen. Small patches were seen in other places along railroad tracks where embankments had produced small areas of marshy ground.

In the Cisco Lake Region a few of the areas of timber killed by the raising of the water-level have grown up to cat-tail swamps. In these swamps there are many standing dead trees and fallen logs as well as some areas of open water. The cat-tails seem to occur mostly in those swamps having only a small connection with the main body of the lake. In these places the cat-tail is dominant, though numerous sedges occur, and there is some sphagnum growing on the fallen logs and along the shore. A few small black spruces are starting. Along the edge of such a swamp a few deer-mice were taken, but these were evidently stragglers from the adjacent forest.

_Willow-thicket habitat:_ Willows do not occur commonly along the water margins of the lakes of the region. The only place, except in clearings, where willows were noted as a definite growth is along the lower course of the Merriweather River at Gogebic Lake. Along this part of the river there are extensive growths of shrubby willows, growing (in early September) in a foot or more of water. The indications were that earlier in the summer the water about these plants must have been at least a foot higher. Signs of muskrat were noted at the edge of these willows.

_Mud-flat habitat:_ Around the margin of a pond formed by an old deserted beaver dam near Gogebic Lake, two miles southwest of Merriweather, is a narrow strip of mud, very wet and sparsely covered with a growth of low rushes. The strip of muddy ground varies from about 1 to 4 meters in width and extends a short distance up along the edge of the small ditch draining into the pond. At the upper border of the strip of muddy shore is a thick growth of sedges, meeting the muddy shore at a fairly sharp line.

In this habitat meadow mice are common and four jumping mice (_Zapus hudsonius_) were taken.

_Meadows_

_Ditch-border habitat:_ A number of small ditches run through an old beaver meadow of considerable size near Gogebic Lake, about two miles southwest of Merriweather. The borders of the ditches are muddy and the banks are from 6 to 18 inches high; in places the ditch borders are closely encroached upon by the tall sedges of the adjacent meadow. A small amount of water was present (in early September) in most of the ditches. In mouse traps set at the edges of these ditches, partly in the water, star-nosed moles and navigator shrews were taken. In a larger trap a skunk was taken.

_Tall-sedge habitat:_ In the beaver meadow studied near Gogebic Lake, an area about 200 meters by 100 meters or more is occupied by a heavy growth of high, coarse sedges, reaching a height of about .75 to 1.00 meter. A few grasses and some low herbs occur sparingly among the sedges. The habitat had not been burned over and the ground is covered with a thick mat of the decaying leaves and stems of the sedges and grasses. In most places the ground is quite wet, sometimes soggy to walk upon, and in a few places low hummocks are numerous. A similar habitat was found in rather a narrow strip at the edge of Mud Lake, one-fourth mile southwest of Thousand Island Lake, Gogebic County. Here a small area of meadow occurs along the inlet of a tiny stream. This area apparently had been artificially cleared of its forest, but the level of the lake had not been raised.

The habitat differs from the submerged-sedge habitat of protected lake shores in being higher above the water and in not being covered with water from July to September; probably water does not stand to any depth on it at any time. The Richardson shrew is apparently a characteristic mammal of this habitat, though other shrews and mice were taken here also.

_Grassy-meadow habitat:_ Part of the beaver meadow studied near Gogebic Lake is covered by a thick growth of grasses and sedges of a number of species. The ground of the habitat was rather dry and had been burned over the previous year. Grasses are also dominant over a few small areas near Mud Lake in Gogebic County. On a small area of the clearing near this lake a thick stand of bluegrass (Poa) is almost the only plant present. This occurs on an area of fairly moist mud. On the drier slope near the forest Poa also is abundant, forming the dominant species over a strip about 5 to 10 meters wide. Jumping mice are common in this habitat.

_Alder-thicket habitat:_ On very wet ground just below an old beaver dam near Gogebic Lake there is a heavy growth of alder (_Alnus incana_) about 20 feet high. No other shrubs were noted in the thicket. The ground under the alders is mostly bare, there being only a few ferns, grasses, and other herbs. On the ground are many dead sticks fallen from the alders. This situation contained few mammals, only one Blarina being taken in four days' trapping with 25 traps. At the south end of the beaver meadow willows and alders are invading the sedges in very wet ground. No trapping was done in this situation.

_Swamps_

_Black ash swamp habitat:_ A number of black ash swamps occur along the shores of Gogebic Lake, being apparently partially flooded during periods of heavy rains and during stages of high water. In a swamp of this type near the north end of Gogebic Lake on the west side, black ash (_Fraxinus nigra_) is the dominant tree, the trunks reaching diameters up to 2 feet. Elms (_Ulmus americana_) sometimes reaching a trunk diameter of 3 feet are common, and yellow birches and hard maples are common also. Black maples are rare, and lindens are few. The trees are high and the forest crown nearly closed. Underbrush is common in the more open places, this being mostly mountain maple (_Acer spicatum_) with a few young firs, young arbor-vitae, and Virginia creepers (_Parthenocissus quinquefolia_). There are numerous ferns, and herbs are abundant. Under the more closed parts of the forest canopy the ground is mostly bare, underbrush and herbs being scanty. Smaller black ash swamps occur in the Cisco Lake Region, and in the vicinity of Little Girl's Point a number of small black ashes were noted in a swamp of mixed arbor-vitae and black spruce.

_Arbor-vitae swamp habitat:_ In the Cisco Lake Region arbor-vitae (_Thuja occidentalis_) occurs commonly near the edges of the lakes and in the wet depressions in the forest. Near Gogebic Lake also the arbor-vitae grows commonly near the shores of the lake and in wet places in the woods, especially at the edges of swamps. But the trees in both these areas, so far as seen, were small, and the arbor-vitae did not form a dominant species, but occurred in a small percentage mixed with the other types of forest. However, in part of the region near Gogebic Lake extensive arbor-vitae swamps are reported to occur. In the vicinity of Little Girl's Point arbor-vitae swamps are common, occupying the wet lower northern slopes of the high ridge.

In a swamp of this type three miles southeast of the point arbor-vitae is the dominant tree, reaching trunk diameters of two feet and more. Under the dense shade of the high forest crown there are many young trees of the same species, and the forest has evidently reached a temporary climax. Of other trees, a few small yellow birch, a few young firs and hemlocks, and one fallen white spruce (_Picea canadensis_) were noted. The ground is very wet and there are numerous tiny streams, which frequently disappear under the ground. Fallen trees and decaying logs on the ground make a thick tangle, very difficult to penetrate. The underbrush is scanty; mountain maple is rather common, and there are a few young black ashes. Much moss grows on the ground and on the decaying logs.

In a depression two miles south of Little Girl's Point is a mixed growth of arbor-vitae, black spruce, with a few black ashes. The trees are mostly small, none of them exceeding about eight inches in trunk diameter. In August the ground was very wet, there being standing water in some places, and the ground was heavily covered with sphagnum. This situation may be considered transitional between the black spruce bog and the arbor-vitae swamp. No traps for mammals were set in this situation.

_Bogs_

_Leather leaf bog habitat:_ In the northwestern corner of Fish-hawk Lake and at several places along the channel connecting Lindsley and Cisco lakes a heavy growth of leather leaf (_Chamaedaphne calyculata_) adjoins and overhangs the water, a considerable portion of the growth actually floating on the water. With the leather leaf is associated much sweet gale (_Myrica gale_) and alders, and these plants form almost the entire mat in some of the wetter areas. At other places sphagnum becomes abundant and the conditions approach those of a sphagnum bog. Other plants commonly found in the leather leaf bog in the Cisco Lake Region are the Labrador tea (_Ledum groenlandicum_), swamp laurel (_Kalmia potifolia_), wild rosemary (_Andromeda glaucophylla_), small cranberry (_Oxycoccus oxycoccus_), pitcher-plant (_Sarracenia purpurea_), and small trees of black spruce and tamarack. In a typical leather leaf bog on the Ontonagon River near the outlet from Thousand Island Lake a large beaver house is located.

_Sphagnum bog habitat:_ In a restricted sense the name is here applied to the part of a bog which is free from trees. It differs from the leather leaf bog in having a greater amount of sphagnum, for while the leather leaf bog when first developed over the water has little or no sphagnum, the sphagnum bog, as here considered, is almost entirely covered by sphagnum. The shrubs found in the two situations are apparently identical, except that the leather leaf is less abundant. A small bog of this type borders the edge of Mud Lake in the Cisco Lake Region, and small parts of many bogs are free from trees. So far as was determined, the mammal fauna is the same as that for the black spruce--tamarack bog, from which the only difference is the absence of trees.