MARINE MAMMAL SCIENCE, 10(l): 105-l 10 (January 1994) 0 1994 by the Society for Marine Mammalogy

SUBSPECIFIC STATUS OF THE FRESHWATER HARBOR SEAL (PHOCA VITULiNA MELLOnAE):

A RE-ASSESSMENT

Five subspecies of harbor seal, Phoca vitulina, have been described on the basis of geographical distribution: P. v. vitulina and P. v. concolor, the eastern and western Atlantic Ocean populations, respectively; P. v, richardsi and P. v. stejnegeri, the eastern and western Pacific Ocean populations, respectively; and P. v. mellonae, a freshwater population from the area of Lacs des Loups Marins (Seal Lakes), approximately I60 km east of Hudson Bay, on the Ungava peninsula of northern Quebec, Canada (Fig. 1) (Bigg 1981). While there are many references to harbor seals occurring in freshwater worldwide (Beck et al. 1970, Paulbitski 1974, Roffe and Mate 1984, Williamson 1988>, with the possible exception of Lake Iliamna, Alaska (Everitt and Braham 1980), Lacs des Loups Marins contains the only known population that is resident year- round.

P. v. mellonae is listed by the International Union for the Conservation of Nature and Natural Resources as being “insufficiently known,” meaning that it is suspected but not definitely known to be endangered, vulnerable, or rare due to a lack of reliable information (Reijnders et al. 1993). Tenuous estimates of population size range from 120 to 600 animals (Reijnders et al. 1993). Because Canada possesses no specific marine mammal or endangered species legislation, the population currently has minimal legal protection.

Regardless, the validity of the subspecific status of P. v. mellonae remains contentious (Honacki et al. 1982, King 1983, Reeves et al. 1992). Anectodal references to the unique appearance and behavior of these seals date back to 1818 (Atkinson 1963). The subspecies was described primarily on the basis of

106 MARINE MAMMAL SCIENCE, VOL. 10, NO. I, 1994

KIVLliKb ----‘, NASTAPOCA

LACS DES v-&x ‘ nr mc MARINS

----- \ - AFFECTED

AREA

0 20 40 60 80 IOOKM

Figure 1. The proposed Grande Baleine hydroelectric project in northern Quebec, Canada. Available evidence indicates that seals are present in the upper portion of the Riviere Nastapoca, Lacs des Loups Marins, the upper portion of the Petite Riviere de la Baleine, Grande Riviere de la Baleine, and La Grande Riviere (Rougerie 1990).

an unusually dark pelage and an enlarged coronoid process on the mandible (Doutt 1942), and on the presumption that the population had been isolated for approximately 5,000 years, trapped by the Ungava peninsula’s isostatic rebound since the last ice age, Some authors disagree with this view, however, arguing that the supposed morphological anomalies of P. 21. mellonae are merely artifacts of a small sample size, and that the seals are likely able to travel freely between salt and freshwater (Mansfield 1967, Smith and Horonowitsch 1987). Resolving this question is now of pressing concern, since the proposed Grande Baleine (James Bay II) hydroelectric project may threaten the continued survival of the seals resident in the Lacs des Loups Marins area (Rougerie 1990).

Our craniometric analysis and synthesis of available information supports the morphological and behavioral distinctiveness of P. v. mellonae.

The five currently available crania of P. ZJ,. mellonae were compared with those of 61 P. v. vitulina, 60 P. v. concolor, 45 P. v. richardsi, 41 P. v. stejnegeri, 42 spotted seals (P. largha), and 49 ringed seals (P. hispida). Four of the P. v. mellonae crania were recently collected from 2 juvenile females, 1 adult male, and 1 adult of unknown sex (specimen numbers PV/LLM/89/1, PV/LLM/ 89/2, PV/LLM/90/ 1, and PV/LLM/90/2, respectively) which are in the possession of the Canadian Department of Fisheries and Oceans; the fifth cranium examined was the holotype of the subspecies (Doutt 1942), an adult male in the Carnegie Museum, Pittsburgh, PA (specimen number CM/l 52 15). Due to the fragmentary nature of some specimens, only 25 of the 29 measurements

NOTES 107

described by an existing experimental protocol (Burns et dl. 1984) were taken on each skull. The palatal length, width of the nasals at the maxillo-frontal suture, least width at the pterygoids, and the distance from the posterior end of the vomerine septum to the medial edge of the palate were not measured. Four non-metric skull characteristics (Burns et dl. 1984) also were noted: the degree of extension of the premaxillaries toward the nasals, the medial length of the nasal bones in contact with the frontals relative to their overall length, the shape of the posterior margin of the jugals, and the angle of the premolar teeth in relation to the line of the jaw. Measurements were Iogre-transformed and the data analyzed using the Statistical Package for the Social Sciences (SPSS- X). The complete data set is available from the authors upon request.

A MANOVA on the sexed specimens indicated that there was no interaction between taxonomic group and sex (Wilk’s A = 0.53, P = 0.31); thus, data from male, female, and unsexed specimens were pooled in subsequent analyses. The effects of individual size differences were minimized using the “C-score” method (Howells 1986), which involved calculating the difference between the Z-score of a single measurement for a given individual, and the mean Z-score of that individual for all the measurements used in the analysis. The data were then submitted to a discriminant analysis (Zar 1984). Mahalanobis D* were computed between the seven groups of seals. The F-statistics calculated from these distance measures indicated that all group means were significantly different from one another (P < 0.0001). A posteriori classifications, based on the discriminant scores, were 83% for P. v. mellonae as compared to 98% for P. hispida, 87% for P. v. concolor, and 78% for P. v. richardsi (Table 1). The results suggest that the Lacs des Loups Marins seal is at least as distinct from P. u. concolor, the Canadian Arctic’s saltwater harbor seal, as is P. v. richardsi, from which P. v. concolor is geographically isolated.

ANOVAs of the individual C-scored character measurements of the P. v. mellonae and P. v. concolor crania indicated that the length of the coronoid process was not significantly different (P = 0.098), contradicting one of the criteria upon which the subspecies was originally described (Doutt 1942). P. v. mellonae was found, however, to have a significantly smaller interorbital width (P = 0.023), a longer distance between the end of the snout and the anterior edge of the nasals (P = 0.005), and upper premolars set parallel, rather than obliquely, to the angle of the jaw (P = 0.018).

Other evidence suggests that P. v. mellonae may also be behaviorally unique. From his conversations with the indigenous peoples of northern Quebec, Doutt (1942) reported that the mean pupping date of the population occurred in early May. This date has also been corroborated by more recent work (Archiotec Inc. 1990). The female P. v. mellonae specimen collected by Doutt (1942) on March 22, 1938 was carrying a 60-cm fetus. By applying this information to a prenatal growth curve that was formulated for the P. v. concolor population from Sable Island, Nova Scotia (which included a linear increase in length of 3.6 mm per day, and a mean length at birth of between 76 and 85 cm), the mean birth date for P. u. mellonae can be estimated as being between 6 and 3 1 May (Boulva and McLaren 1979). Using a prenatal growth rate of 4.4 mm per day and a

108 MARINE MAMMAL SCIENCE, VOL. 10, NO. 1, 1994

Table 1. A posteriori classifications based on discriminant scores for five P. vitulina subspecies, P. largha, and P. hispida.

Group

5% Correctly

PVC PVM PVR PVS Pvv PL PH classified

concolor (PVC)

mellonae @‘VW

richardsi o?vR)

stejnegeri (PW

vitulina w-9

largha NJ

hispida (PW

% Correctly classified

52 2 4 1 1 87

5 100

1 35 8 1 78

1 1 4 32 1 2 78

5 56 92

3 1 38 91

49 100

88 83 80 78 92 91 98

mean length at birth of 81.6 cm, such as were observed in P. v. richardsi in British Columbia (Bigg 1969), the estimated mean birth date of P. v. mellonae is 10 May. Both of these estimates for the mean birth date of P. v. mellonae are substantially earlier than for other harbor seal populations at a similar latitude (for example, June 10 in northern Labrador, June 27 at Schleswig/Holstein, Germany, and June 29 at Port Moller, AK) (Temte et al. 1991). If Temte et al. (199 1) and Temte (1991) were correct in their belief that birth timing in harbor seals has a heritable component and may, therefore, function to create reproductive barriers between adjacent populations, our calculations would fur- ther suggest that P. v. mellonae may be reproductively isolated from P. v. concolor.

Hydro-Quebec, the provincial hydroelectric utility, would like to begin con- struction on the Grande Baleine project as soon as possible. It is estimated that four proposed reservoirs will flood over 310,000 hectares of land, substantially altering the hydrology of the region (Rougerie 1990). The project continues to undergo intense scrutiny both in Canada (environmental assessment hearings are underway) and abroad (e.g., Rosenthal and Beyea 1989), with concerns being expressed over its impacts on native peoples and the environment. Because P. v. mellonae may rely on strong currents to create ice-free areas and under-ice shoreline shelters in winter (Smith and Horonowitsch 1987), altered water flow could result in habitat changes and increased mortality of seals. Seasonal alter- ations of discharge rates brought about by the project could also affect the distribution and abundance of the seals’ prey, and contaminate the lake with methyl mercury produced by the flooded, decomposing vegetation (Reijnders et al. 1993).

NOTES 109

We are unable to reject the hypothesis that P. v. mellonae is a unique subspecies (O’Brien and Mayr 1991, Geist 1992). Our results, together with evidence that the range of this seal is larger than previously thought, extending well into the Grande Baleine project area (Rougerie 1990), make further assessment of the project’s potential impact on P. v. mellonae a priority. Investigations using molecular techniques are currently being pursued to determine the extent to which the morphological and behavioral uniqueness of P. v. mellonae is reflected genetically.

ACKNOWLEDGMENTS

Special thanks go to the staff at the following institutions: Arctic Biological Station, Ste. Anne-de-Bellevue, Quebec; Carnegie Museum, Pittsburgh, PA; National Museum of Natural History, Washington, DC; Canadian Museum of Nature, Ottawa, Ontario; University of Alaska Museum, Fairbanks, AK; American Museum of Natural History, New York, NY; Naturhistoriska Riksmuseet, Stockholm, Sweden; Zoologisk Museum, Copenhagen, Denmark; and the University of Amsterdam Museum, Amsterdam, The Netherlands. This research was funded by the International Marine Mammal Association Inc., Guelph, Ontario.

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RICHARD J. SMITH AND DAVID M. LAVIGNE, Department of Zoology, University of Guelph, Guelph, Ontario, Canada N 1G 2 W 1; WILLIAM R. LEONARD, School of Human Biology, University of Guelph, Guelph, Ontario, Canada NlG 2Wl. Received 5 April 1993. Accepted 9 August 1993.