mammals of lake iroquois age

Canadian Journal of Zoology Issued by THE NATIONAL RESEARCH COUNCIL OF CANADA

VOLUME 41 MARCH 1963 NUMBER 2

MAMMALS OF LAKE IROQUOIS AGE

C. S. CHURCHER Department of Zoology, University of Toronto, Toronto, Ontario

AND

P . F . KARROW Ontario Department of Mines, Toronto, Ontario

Received August 4 , 1962

Abstract Remains of single individuals of a juvenile gray fox ( Urocyon cinereoargenteus),

an eastern chipmunk (Tamias striatus), and a meadow vole (Microtus pennsylvanicus) have been recovered from a buried soil horizon a t Scarborough Bluffs. Toronto, Ontario. These have been dated on associated charcoal fragments a t 5550 + 70 CIA years ago. The charcoal has been identified as being derived from white pine (Pinus strobus), hard maple (either Acer saccharurn or A. nigrum), and probably beech (Fagus grandifolia). This faunal evidence is considered approximately contemporaneous with a fauna from Hamilton Bay containing the pine vole (Pitymys pinetorum) and the presence of the pine vole and gray fox is adduced as support for a climatic optimum some 5000 years ago. Remains of the muskrat (Ondatra zibethicus) have also been recovered from the Hamilton Bay faunal site, adding another mammal to this faunal list.

A number of fragments of bone and some teeth have been recovered from the sands and silts composing Scarborough Bluffs, Toronto, Ontario. The fragments lay within a dark band of fine soil containing organic remains. Brief reference to this fossil soil has been made by Terasmae (9). The band is exposed for some hundreds of feet along a section of Scarborough Bluffs lying to the east of the Dutch Church Section, and lies some 4 ft beneath the present- day turf covering an outwash fan overlying the wave-cut bench attributed to Lake Iroquois times. No signs of disturbance of the sands, silts, and fine gravels of the fan overlying the deposit were observed and the possibility of the remains being of an intrusive origin can be discarded. The one of us who dis- covered the bone fragments (Karrow) believes that leaching had occurred in two layers, one to a depth of some 22 in. beneath the present soil level and the other to some 14 in. beneath the first. The soils seem to be alluvial in origin, the fragments of bone and charcoal associated with them being scattered through- out the layer. Additional pieces of wood charcoal lie within the sandy layers above the fossil soil to a height of some 6 in., but are more scarce. Such a distribution of the bone and charcoal could be brought about by water-borne deposition from the small stream which deposited the fan while draining across the exposed and vegetated bench.

Canadian Journal of Zoology. Volume 41 (1963)

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154 CANADIAN JOURNAL OF ZOOLOGY. VOL. 41. 1963

Samples of the wood charcoal have been dated (6) on the radiocarbon con- tent. The age of the sample (radiocarbon sample S-115A) has been determined as 5550 f 70 C1( years, or approximately 3550 B.C. A second sample (S-115B) is dated a t 5240 + 100 Cl4 years. The wood charcoal has been identified from sections by Dr. R. W. Kennedy (personal communication) of the School of Forestry of the University of Toronto as "1. White pine, Pinus strobus L. 2. Hard maple (either Acer saccharum Marsh. or Acer nigrum Michx.f.). One other hardwood, probably beech, Fagus grandifolia Ehrh."

The skeletal remains are all mammalian and represent a sciurid rodent, a microtine rodent, and a small canid carnivore. These specimens have been catalogued in the collections of the Royal Ontario Museum.

The only sciurid specimen that is identifiable is a left lower incisor (111) (ROM 2742), which agrees in size, cross section, and curvature with, and shows the same pattern on the occlusal wear-surface as, a 111 of the living eastern chipmunk, Tamias striatus.

The microtine remains comprise both upper incisors (I1's), both first lower molars (Ml's), the left second molar (1M2), and some associated cranial and mandibular fragments (collectively catalogued ROM 2741). The incisors match those of the living meadow vole, Microtus pennsylvanicus, in curvatures, cross sections, and occlusal wear surfaces, while the molars are of the same size and exhibit the triangular occlusal patterns typical of the genus. The specimens are assigned to the species M. pennsy1van.i~~~ as this species is present in southern Ontario today, because it is the most widely distributed species of the genus, and because Ml 's characteristically exhibit five closed triangles (3).

The bone fragments of the small canid carnivore represent some of the major elements of the skeleton (collectively catalogued ROM 2740). Elements identified were the left condylar region of the mandible, portions of the parietals and frontals, left humerus, ribs, scapulae, and fragments of long-bones and phalanges. Dental specimens identified were right first and second upper +

incisors (rI1 and r12), right lower canine (rC1), right second lower premolar (rPz), right fourth lower premolar (rP4) with part of the mandible supporting it , right lower milk canine (rcl), and left and right upper milk canines (lcl and rcl), either whole or fragmentary. Many of these elements showed signs of fire-blackening and calcination. No duplication of the elements was observed, suggesting that all the canid material was derived from a single individual. Criteria for assessing the age of a red fox are discussed by Churcher ( I ) , the presence of free epiphyses and poor ossification of the ends of the long-bones, t he open and large pulp cavities in the permanent teeth, the smooth outer surface of the temporal area on the recovered parietal fragments, and the presence of both milk and permanent teeth in the sample suggest an age determination for the specimen of less than 9 months.

The identification of the Scarborough Bluffs canid has been based on com- parative measurements of Pz's and P4's from gray fox (Urocyon cinereoargenteus), Arctic fox (Alopex lagopus), and red fox ( Vulpes vulpes) specimens in the Royal Ontario Museum, Toronto. Measurements of the maximum length and maximum width of the crown and the height of the crown measured between the roots were taken on both teeth, while the maximum depth and

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1.54

1.60 - 1.50

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width of the mandible measured on the plane between the roots were taken on the fragment of ramus associated with the P4 specimen. The measurements of the maximum width of the mandible proved to be inconclusive. Table I gives the means and maxima and minima for the seven dimensions for the three com- pared species and the measurements for the recovered specimens. These figures show, both by inspection and when plotted, that the dimensions of the recovered fragments do not fall within the size range of the red fox measurements for any dimension, but that they fall twice within the size range of the Arctic fox (i.e. maximum length of the crown of P4 and maximum depth of the mandible between the roots of P4) and of the gray fox four times (maximum width and maximum height of the crown of P4, maximum length of the crown of Pt, and maximum depth of the mandible between the roots of P4). In two of the other dimensions (maximum length of the crown of P4 and maximum width of the crown of P2) the measurements for the Scarborough Bluffs canid are close to those for both the gray and Arctic foxes. We have concluded therefore that the remains of the Scarborough Bluffs canid represents a juvenile specimen of the gray fox (Urocyon cinereoargenteus).

Discussion Wetmore (13) reported the discovery of a fossil fauna from the Lake

Iroquois beach lying within the area of Hamilton Bay. Among the remains reported are included both the eastern chipmunk (Tamias striatus) and the red fox (Vulpes vulpes) but neither the gray fox (Urocyon cinereoargenteus) nor the meadow vole (Microtus pennsylvanicus). This report represents the only other fauna of possibly equivalent age from the shoreline of Lake Iroquois, but as no radiocarbon date is available for this fauna, strict comparison is impossible. The date suggested by Wetmore for this fauna is "late Pleistocene (late Lake Iroquois)" . . . "during its period of shrinkage" (13). This date was founded upon ilconsiderable discussion" by Dr. Wetmore and others (personal communication). Such a determination could be interpreted to indicate an age of approximately 10,000 to 12,000 years ago on the present state of our knowledge (4).

The rest of the Hamilton Bay fauna reported by Wetmore includes the wood duck (Aix sponsa) , barred owl (Strix varia) , common grackle (Quisculus quiscula), short-tailed shrew (Blarina brevicauda), gray squirrel (Sciurus carolinensis), flying squirrel (Glaucomys sabrinus), and pine vole (Pitymys pinetorum) as well as the eastern chipmunk and red fox mentioned previously. All these forms are found a t present in southern Ontario but few extend across the Great Lakes - Hudsons Bay divide, although the common grackle, the short-tailed shrew, and the flying squirrel are found down the Moose River as far as Moosonee. The Hamilton Bay fauna is therefore not Arctic in facies, and the presence of the pine vole introduces a definite Carolinian element to emphasize its southern affinities, the northern limits of distribution of the pine vole today being in the neighborhood of Hamilton, Ontario.

The region southwest of the retreating ice-sheets involving the Great Lakes area has been considered to have had a climate comparable to that of James Bay or southern Hudsons Bay a t the present time, which is sub-Arctic in character. Therefore it is probable that the fauna from Hamilton Bay cannot C

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CHURCHER AND KARROW: FOSSIL MAMMALS 157

date from the period irrrmediatefy after the ice-sheets left thc area, approximately 12,000 years ago, but must date considerabf y later, passibIy from the ~ l ima-~ ic optimum placed approximately 5000 years ago, or nearer the present time. Such a supposition would agree with the reported date of 11,500 + 240 Cia years ago (4,8) for pieces of wood found at an elevation of 320 It during the excavation for a new City Hall in Iht-tilton, while t h e Hamilton Bay fauna would be later and a t a lower level, i.e. some 275 ft above sea level. This would date the wood from the Lake Iroquois heach soon after the ice-sheets had left the area, and the Hamilton Bay fauna would have existed after the reduction of Lake Iroquois to almost the outlines of Lake Ontario.

An examination of the Hamilton Bay faunal site, which Iies on the south- eastern bank of a seasonal tributary ravine draining into Coote's Paradise (the western section of I-Tarnilton Bay) and near McMaster University, reveals a series of crassF>edded finc and medium gravels and sands. Hardpan

, formation occurs at approximately t 2 f t below the present land surface, indura- tion being caused mainly hy calcium carbonate and iron saIts. The degree of consolidation varies markedly, hard lenses of a conglomeritic nature only a few inches or parts of an inch thick alternating with less consolidated or free layers. Beneath the hardpan layer unconsolidated cross-bedded sands are seen. The whole deposit has the formation attributable to the recent consolidation of a soft deposit. I t is possible tha t the material comprising the deposit may be derived as erosional debris from Hamilton Mountain (part of the Niagara Escarpment) during the refilling; of Hamilton Ray after the retreat of the ice.

Further bones wcre obtained from this site, being identified by Mr. Shelly Logier of the Royal Ontario Museum as vertebrae from a colubrid snake and one snake rib (collectively c a t a l o ~ d ROM 27501, and by one of us (Churcher) as a partial radius and a fragmental right frontal of a juvenile fox (collectively catalogued ROM 2749) and a radius 05 a muskrat (Ondatra zibelltkcus) (ROM 2743). This additional materia1 agrees with the fauna reported by !Tretmore and adds the muskrat to it.

Because of the presence of the pine vole in the Hamilton Bay fauna, and of the other non-Arctic faunal elements, the lower altitude of the site and the unconsolidated nature of the deposits, it is reasonable to suggest a more recent date for the fauna than that suggested by Wetmore. The southern facies of the fauna points towards the climatic optimum, and tentatively a date of some 5000 years ago may be postulated.

The presence of gray foxes in southern Ontario is reported from a number of Indian Middens (7,10,11,12) and from the Site of Ste. Marie 1 (5) , catabIished by the French Jesuits at the southeast end of Georgian Ray near Midland, Ontario, and they seem to have disappeared from this area by 1649 A.D. (2,7). The presence of the gray fox in the Scarborough Bluffs faunal deposit, with a C14 date attributabte to i t of 5550 zk T O years ago, together with the presence of the pine vole in the Hamilton Bay fauna, which may be considered roughly contemporaneous with the Scarborough Bluffs date, points to a warmer a d more Carolinian iacies to the fauna and climate and supports the general acceptance of a climatic amelioration some 5000 years ago greater than that presently obtaining in the area.

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References 1. CHURCHER. C. S. 1960. Cranial variation in the North American red fox. T. Mamm. 41(3). . ..

349-360. 2. DOWNING, S. C. 1946. The history of the gray fox in Ontario. Canadian Field-Nat. 60(2),

4.546. 3. HALLTE. R and KELSON, IC lL 1959. The mammals of North America. Vol. II. The Ron-

ald Press Co., New York. pp. 273-274. 4. KARROW. P, F., CLARK, J. R.. and ~'ERASMAB, J. 1961. The age of take Irquois and Lake

Ontario. J. Geol. bY6), 65-67. 5. KDD. IC E. 1949. The excavation of Ste. Marie I. Universitv of Toronto Press. Toronto. 6. MCC~LLCW, K. J. and ~ V I ~ N B E R G , J. 1962. L'niversity d Saskatchewan radiocarbon

dates 111. Scarhnrough RIoffs, Ontario-S-115. Radiocarbon, 4, 74. 7. PETERSOP, R. L., STANDFIELD, R. O., h l c E w ~ , E. Ii . , and BROOKS, A. C. 1953. F d y

records of the red and gray foxes in Ontario. J. Manirn. 34(1), 126-127. 8. STLZVEK, M., DFXVEY, E.S., and GWINSKI, L. J. 1960. Ya!e naturalmdiocarbon measure-

ments V; Hamilton City HaII-Y-691. Am. J. Sci. Radiwarbon Suppl. 2, 50. 9. TRRASYM, J. 1960. Contributions to Canadian palynolmgy No. 2. Geol. Surv. Can. Bull.

No. 56. p. 30. 10, ' C ~ T E ~ E R G , N-. 1. 1921. Archaeological evidence concerning the presence of the gray

fox ( L ~ ~ n c ~ y u n sp.) in Ontario. Canadian Field-Xat 35(1), 19-20. 11. WINTEYEERG, W. J. 1928. Uren prehisicrric village site, Oxford County, Ontario. Nat. Mus.

Can. BuU. No. 51. Anthrop. Scr. No. 10. 12. WINTEMDERG, W. J. 1939. Lawson prehistoric village siie, Middlesex County, Ontario.

Nat. Mus. Can. null. No. P4. Anthrop. Ser. No. 25. 13. Z V E ~ O R P , , A. 1958. Miscellaneous notes on fossil birds. Set. V. Pleistocene bird records

from Ontario. Smithsnnian Misc. Collections, 135(8), 9-10.

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mammals of lake iroquois age

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