Phenacomys ungava (Rodentia: Cricetidae)

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Phenacomys ungava (Rodentia: Cricetidae) JANET K. BRAUN, SARA B. GONZALEZ-PEREZ, GARRETT M. STREET, JENNIE M. MOOK,

AND

NICHOLAS J. CZAPLEWSKI

Sam Noble Oklahoma Museum of Natural History, University of Oklahoma, Norman, OK 73072, USA; [email protected] (JKB); [email protected] (NJC) Department of Zoology, University of Oklahoma, Norman, OK 73019, USA; [email protected] (SBG-P); [email protected] (JMM) Department of Botany and Microbiology, University of Oklahoma, Norman, OK 73019, USA; [email protected] (GMS) Abstract: Phenacomys ungava Merriam, 1889, is an arvicoline rodent commonly known as the eastern heather vole. A small vole with a short tail and reddish to yellowish nose and eye rings, it is 1 of 2 currently recognized species in the genus Phenacomys. The species occurs in diverse habitats of the boreal forest ecosystem of Canada from Labrador to southern Yukon and from southern Quebec to southern Alberta, with isolated records from northeastern Minnesota. P. ungava is listed as ‘‘Least Concern’’ by the International Union for Conservation of Nature and Natural Resources. Key words:

Canada, eastern heather vole, heather vole, murid, rodent

Ó 30 May 2013 American Society of Mammalogists Synonymy completed 16 December 2010 DOI: 10.1644/899.1

Phenacomys ungava Merriam, 1889 Eastern Heather Vole Phenacomys celatus Merriam, 1889:33; plate 2, figures 1–3; plate 4, figure 13. Type locality ‘‘Godbout,’’ Canada, Quebec. Phenacomys latimanus Merriam, 1889:34; plate 2, figure 5; plate 4, figure 12. Type locality ‘‘Fort Chimo, Ungava, Hudson Bay,’’ Canada, Quebec. Phenacomys ungava: Merriam, 1889:35; plate 2, figure 4; plate 3, figures 8 and 9. ‘‘Fort Chimo, Ungava, Hudson Bay Territory,’’ Canada, Quebec; first use of current name combination. Phenacomys celatus crassus Bangs, 1900:39. Type locality ‘‘Rigoulette, Hamilton Inlet,’’ Canada, Newfoundland and Labrador. Phenacomys mackenzii Preble, 1902:182. Type locality ‘‘Fort Smith, Slave River (near the Athabasca–Mackenzie boundary line),’’ Canada, Northwest Territories. Phenacomys ungava ungava: Howell, 1926:13, 25. Name combination. Phenacomys ungava crassus: Howell, 1926:13, 27. Name combination. Phenacomys mackenzie Banfield, 1941:121. Incorrect subsequent spelling of Phenacomys mackenzii Preble, 1902. Phenacomys ungava soperi Anderson, 1942:58, figure. Type locality ‘‘near Swanson Creek, in the middle of Section 34, Township 19, Range 17, Riding Mountain National Park, Manitoba; about ten miles east of Park Head-

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quarters at Wasagaming, on Clear Lake, altitude 2016 feet,’’ Canada, Manitoba. Phenacomys ungava mackenzii: Anderson, 1942:58. Name combination. Phenacomys intermedius mackenzii: Crowe, 1943:403. Name combination.

Fig. 1.—An adult male Phenacomys ungava from Fort Chimo, Ungava, Quebec Province, Canada (USNM [United States National Museum of Natural History] 282954). Used with permission of the photographer M. A. Mares.

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Phenacomys intermedius ungava: Crowe, combination. Phenacomys intermedius crassus: Crowe, combination. Phenacomys intermedius soperi: Crowe, combination. Phenacomys intermedius celatus: Hall 1953:395. Name combination.

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1943:404. Name 1943:404. Name 1943:404. Name and Cockrum,

CONTEXT AND CONTENT. Order Rodentia, suborder Myomorpha, family Cricetidae, subfamily Arvicolinae, genus Phenacomys (Musser and Carleton 2005). Although no subspecies were recognized by Musser and Carleton (2005), 4 subspecies were recognized by Hall (1981): P. P. P. P.

u. crassus Bangs, 1900:39. See above. u. mackenzii Preble, 1902:182. See above. u. soperi Anderson, 1942:58. See above. u. ungava Merriam, 1889:35. See above; celatus Merriam and latimanus Merriam are synonyms.

NOMENCLATURAL NOTES. Phenacomys ungava (eastern heather vole) currently is recognized as distinct from P. intermedius (western heather vole—Musser and Carleton 2005). Howell (1926) recognized 3 species (intermedius, mackenzii, and ungava), but Anderson (1942, 1947) later included mackenzii in ungava. These taxa were further combined in intermedius by Crowe (1943) based on suspected intergrades between P. u. mackenzii and P. i. levis in southwestern Alberta, Canada. Since, various authors have recognized 1 species (e.g., Hall and Cockrum 1953; Banfield 1974) or 2 species (e.g., Peterson 1966; Cowan and Guiguet 1978) of Phenacomys. Foster and Peterson (1961:45) suggested that Crowe’s (1943) proposed intergrades may be a result of age variation and ‘‘while a final evaluation of the relationship between Phenacomys ungava and P. intermedius must await a more thorough study, especially of the latter, it seems quite obvious that intergradation between the two forms has not been demonstrated.’’ Cowan and Guiguet (1978:212) also noted that ‘‘in our opinion this matter [conspecificity of P. ungava and P. intermedius proposed by Crowe (1943)] requires more detailed examination before a decision can be reached.’’ Because taxa that now are included in P. ungava previously were considered as subspecies of P. intermedius, only literature data that could be associated clearly with P. ungava were used in this account. Because the ranges of the 2 species have been suggested to be nonoverlapping (Soper 1964; Cowan and Guiguet 1978; Hall 1981), much of the specific information from the literature was evaluated primarily on the known distributions. We have omitted those publications where it was unclear as to the identification of specimens. The species epithet ungava was selected by Miller (1897b:84), the 1st reviser of the genus, in preference to celatus, although the description for ungava appears several

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pages after that of celatus. Bangs (1900) and (Elliot 1901), among others, used celatus based on its page priority. The use of the name ungava was followed by Howell (1926) and subsequent authors until the early 1950s. Hall and Cockrum (1953) recognized P. intermedius celatus and placed ungava and latimanus as synonyms based on the anticipation that page priority would be invoked in the revised International Rules of Zoological Nomenclature (Handley 1954). Because the ‘‘first reviser rule’’ remained in effect (Stoll et al. 1961), ungava is the proper name usage for this taxon. Type specimens for taxa given above are present in the collections at the Canadian Museum of Nature (soperi CMN 17131), Museum of Comparative Zoology (crassus MCZ 3959), and United States National Museum of Natural History (ungava USNM 186488; celatus USNM 186486; latimanus USNM 186487; mackenzii USNM 110625). Some First Nations believe that P. ungava dies after coming into contact with human footprints (Merriam 1889). The Davis Inlet band of Naskapi First Nations identified Phenacomys as an-i-suk-i-sash (Strong 1930). The etymology of genus name is derived from phenax (Greek), meaning cheat or imposter, and mys (Greek), meaning mouse, which refer to the ‘‘circumstances that the external appearance of the animal gives no clue to its real affinities’’ (Merriam 1889:28). The etymology of the specific and subspecific epithets are: crassus (Latin), meaning thick, fat, and stout, a reference to the size being larger than other taxa; mackenzii, a geographic place (Mackenzie); soperi, a proper name (J. Dewey Soper); and ungava, a geographic place (Ungava—Merriam 1889; Bangs 1900; Preble 1902b; Anderson 1942).

DIAGNOSIS Phenacomys ungava is distinguished from the other species in the genus (P. intermedius) by external and cranial characters (Howell 1926; Banfield 1974; George 1999a, 1999b; Reid 2006). The nose and eye rings of P. ungava are yellowish to reddish; in P. intermedius the coloration of the hairs of the nose and face is grayish brown. The tips of the ears of P. ungava are tawny or yellowish and a tuft of stiff orange hairs is present in front of each ear. In contrast, ear tufts are absent in P. intermedius and the ears are lightly lined with yellowish hairs. The dorsal coloration of P. ungava is grizzled dull brown often with a yellowish or tawny wash, particularly on the rump; the dorsal coloration is variable in P. intermedius, ranging from dark brown to gray brown to reddish brown, but lacks the yellowish wash. P. ungava differs from P. intermedius in having a larger cranium, larger auditory bulla, a relatively narrower interorbital region, and well-developed interorbital ridges (Howell 1926; Foster and Peterson 1961). The angle of the

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rostrum is strongly downward in P. ungava and the palate has a well-defined, blunt median process (Howell 1926); in P. intermedius, the rostrum is only slightly angled and the morphology of the palate, although variable, is simpler and the median process is not well defined.

GENERAL CHARACTERS Phenacomys ungava (Fig. 1) is a small to medium vole with a short tail (Merriam 1889; Miller 1896, 1897a, 1897b; Bangs 1900; Preble 1902b, 1908; Hinton 1926; Howell 1926; Anderson 1942; Hall and Cockrum 1953; Harper 1956; Johnson 1973). The length of the tail is , 50% of the length of the head and body or about 25% of the total length. The ears are small, barely visible above the fur, and well haired on the inner surface and outer edge. Five well-developed tubercles are present on the plantar surface of the forefoot and 6 are present on the hind foot. The pelage of P. ungava is thick and soft. The dorsal coloration is brownish with a yellowish wash; blackish tipped hairs give the dorsum a grizzled appearance. Hairs of the dorsum are plumbeous basally. Pelage color and size varies geographically; populations in the east are generally darker colored and larger and those in the west are paler and smaller. The sides are lighter in coloration than the dorsum and the rump and flanks are brighter, a tawny olive or russet. The coloration of the face and snout is yellowish, ochraceous, or cinnamon, contrasting with the rest of the head and dorsum. Compared with adults, the pelage of juveniles is darker (the plumbeous bases more evident), duller (less brownish), and lacks the cinnamon and ochraceous coloration. The general color of the venter is grayish white; hairs are plumbeous basally, giving the area of the throat and belly a darker appearance. The tail generally is bicolored, blackish brown above and grayish white below, but this may be less distinct in juveniles and adults in some localities. The hairs of the inner surface of the ear are tawny ochraceous and a tuft of stiff orange hairs is present in front of each ear; hairs of a small postauricular area are paler than the dorsum. The feet are covered with light-colored hairs ranging from whitish to pale grayish. External measurements (mean and range, mm; body mass, g; sexes combined; n ¼ 49—Smith and Foster 1957) of adult P. u. mackenzii were: total length, 131 (111–152); length of tail, 32 (23–40); length of hind foot, 19 (17–20); body mass, 27.4 (15.5–46.7). External measurements (mm; body mass, g; 2 males and 2 females, respectively—Harper 1956) of subadult P. u. mackenzii were: total length, 118, 129, 117, 121; length of tail, 24, 28, 24, 26.5; length of hind foot, 17.5, 18, 18, 18; length of ear, 12, 12.5, 13, 13.5; body mass, 18.4, 21.7, 16.6, 17.8. Cranial measurements (mean, mm) of P. u. crassus (3 adults—Howell 1926), P. u. mackenzii (3 females—Howell 1926), P. u. soperi (3 females—Anderson 1942), and P. u. ungava (2 adults—

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Howell 1926), respectively, were: condylobasilar length, 24.4, 22.7, 21.3, 23.55; length of nasals, 7.6, 7.4, 6.3, 7.3; interorbital breadth, 3.5, 3.1, 3.0, 3.65; zygomatic breadth, 15.2, 14.0, 13.0, 14.75; lambdoidal width, 11.4, 11.1, 9.2, 11.55; length of incisive foramina, 5.1, 4.5, 4.0, 4.65; length of maxillary toothrow, 5.8, 5.7, 6.0, 5.8; height of skull, 9.3, 9.1, 8.9, 9.1. Variation in external or cranial measurements between sexes and among age groups is insignificant (Foster 1961). The skull (Fig. 2) is subquadrate in shape (Merriam 1889; Miller 1896, 1897a, 1897b; Preble 1902b; Hinton 1926; Howell 1926; Hall and Cockrum 1953; Johnson 1973). Well-developed supraorbital ridges and a deep median longitudinal frontal sulcus generally are present; development, however, increases with age and is more evident in males, and may vary geographically. The postorbital process of the squamosal is prominent and peglike. The interparietal is relatively large, pentagonal in shape, and the posterior border nearly straight. Temporal ridges are well developed and widely separated, especially in adults. The rostrum, when viewed laterally, is depressed or flexed downward. The suture of the premaxilla and maxilla forms a near right angle. Bullae are small to medium in size and globular; internal spongy tissue is absent. The palate is broadly emarginate posteriorly, not transversely continuous or shelf-like, and terminates in a distinct median spinous process. Dental formula is i 1/1, c 0/0, p 0/0, m 3/3, total 16. Dental characters include (Merriam 1889; Miller 1896, 1897b; Preble 1902b; Hinton 1926; Howell 1926; Hall and Cockrum 1953): dentine is brown to black; rooted molars in adults; and molars with 2 roots. In the upper molar teeth, the reentrant angles of the molars are only slightly deeper on the lingual side compared to the labial side; M1 has a broadly rounded anterior triangle and 2 closed triangles on each side; M2 has a rounded anterior triangle, and 1 internal and 2 external triangles, which often are closed; the anterior face of M2 and M3 is concave and the anterior loop is pyriform; M3 has a rounded anterior triangle, 1 internal triangle, 2 external triangles, and a postero-internal loop. In the mandible, the root of the lower incisor extends posteriorly from the lingual to the labial side of the molars, between the bases of the roots of m2 and m3, and terminates at the level of the alveolus of m3; the reentrant angles of the lower molars are proportionally deeper on the lingual side compared to the labial side; m1 with anterior trefoil variable, anterior loop that forms an inward or slightly outward projection, posterior transverse loop, 4 internal triangles, and 3 external triangles; m2 has 2 small external triangles, 2 elongated internal triangles, and a posterior transverse loop; m3 has 3 elongated internal loops and a distinct convex notch opposite the middle lobe on the inner side.

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Alberta, south-central Saskatchewan, southern Manitoba, southern Ontario, and southern Quebec provinces (Fig. 3; Hall 1981; McAllister and Hoffmann 1988; George 1999b; Linzey et al. 2008). In the United States, P. ungava has been documented only in northeastern Minnesota (Handley 1954; Etnier 1989; Jannett and Oehlenschlager 1997). The distributions of the currently recognized subspecies are: P. u. crassus, coastal and inland Labrador; P. u. mackenzii, northeastern British Columbia, Alberta, northern Saskatchewan, northern Manitoba, southern Nunavut, southern Northwest Territory, and southern Yukon; P. u. soperi, eastcentral Alberta, central Saskatchewan, and west-central Manitoba; and P. u. ungava, eastern Manitoba, Ontario, Quebec, parts of Labrador, and northeastern Minnesota (Fig. 3; Peterson 1966; Banfield 1974; Hall 1981). The distributions of P. ungava and P. intermedius in southwestern Alberta have been suggested to be allopatric. Whereas P. intermedius is distributed at higher elevations (Innes and Millar 1982; George 1999a) along the eastern slopes of the Rocky Mountains, P. ungava is found at lower elevations and is associated with the Mackenzie Basin and its tributaries, including those of Great Slave Lake (e.g., Howell 1926; Soper 1964; Innes and Millar 1982; George 1999b).

FOSSIL RECORD

Fig. 2.—Dorsal, ventral, and lateral views of skull and lateral view of mandible of an adult male Phenacomys ungava from Fort Chimo, Ungava, Quebec Province, Canada (USNM [United States National Museum of Natural History] 282954). Greatest length of skull is 24.39 mm. Used with permission of the photographer M. A. Mares.

DISTRIBUTION Phenacomys ungava occurs throughout most of Canada, from Labrador west across southern Nuvavut and Northwest Territories to southern Yukon, and south to southern

The ancestry of the genus Phenacomys is uncertain, but its rooted molars and other dental characters suggest that it differentiated early within the arvicoline radiation, possibly within Beringia during the early Pliocene from an Asian ancestor such as the extinct Mimomys (Repenning et al. 1987; Repenning and Grady 1988). A derivation from Mimomys, however, was not supported by Martin et al. (1986) based on the lack of characters shared with extant arvicolids; they suggest a derivation from an unknown ancestor in northern Asia. The early fossil record for Phenacomys is weak (generally rare prior to the Wisconsin—Martin et al. 1986) but dental characters suggest a separation from Arborimus by the middle Pleistocene (Repenning and Grady 1988). A molecular phylogeographic analysis of sequences of the mitochondrial control region of recent Phenacomy intermedius in the Pacific Northwest estimated a divergence date for Phenacomys and Arborimus of 2.1–2.8 million years ago (Chavez and Kenagy 2010). The earliest fossils in North America assigned to Phenacomys are from Froman Ferry, Idaho, dated by magnetostratigraphy at either 1.5–1.6 million years old (Bell et al. 2004) or 1.9–2.6 million years old (Ruez 2009). Less well known temporally are fossil localities in Alaska, Yukon, and Yakutia (¼ Sakha), Russia, with 2 extinct species, Phenacomys gryci and Phenacomys deeringensis of putative late Pliocene age (Repenning and Grady 1988). Most North American fossils of Phenacomys are from the late Pleistocene, and are widespread in previously

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Fig. 3.—Geographic distribution of Phenacomys ungava. Subspecies are: 1, P. u. crassus; 2, P. u. mackenzii; 3, P. u. soperi; 4, P. u. ungava. Map redrawn from Hall (1981) with modifications.

periglacial areas across the middle temperate latitudes of the United States (between about 488N and 358N latitude), far south of the present range. Late Pleistocene records extend west–east from Nevada to Pennsylvania and north–south from North Dakota to Tennessee and Arkansas (McAllister and Hoffmann 1988; FAUNMAP Working Group 1994). Fossil remains consist primarily of teeth and jaws that seem to lack sufficiently diagnostic gross morphological characters to enable differentiation of P. ungava and P. intermedius. Most of the late Pleistocene occurrences have been identified as P. intermedius following the taxonomy accepted at the time (e.g., FAUNMAP Working Group 1994), but many of them may in fact represent P. ungava as currently recognized (Musser and Carleton 2005:1036). Differentiation of the 2 currently recognized modern species likely occurred during the glacial advances and retreats of the Pleistocene, with the 2 forms having diverged sufficiently to remain distinct in parapatry following at least the last deglaciation.

FORM AND FUNCTION Phenacomys ungava has 8 mammae; 4 are located in the inguinal region (also described as 2 postabdominal and 2 inguinal) and 4 are positioned in the pectoral area (Miller 1897a; Harper 1956, 1961). Posterolateral scent glands, modified hypertrophied sebaceous glands, are present on the flanks of adult males (Howell 1926). Glands of an adult male examined in mid-July measured 28 by 10 mm (Harper 1961). The hairs of the flank gland area may be paler than those of the surrounding area and they may exhibit a different cycle of hair growth as was found for P. intermedius (Quay 1968). Brain lesions containing birefringent (double refraction of light) colloid deposits have been reported in a wild-caught individual from Manitoba (Quay 1969).

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The distinctive yellow nose and face always is present in adults and occasionally in subadults (Foster and Peterson 1961). In juveniles, however, the yellow coloration is absent (Harper 1956; Foster and Peterson 1961). The dorsal pelage coloration of juveniles is darker, brownish olive mixed with blackish hairs, and the coloration on the rump is duller compared with adults (Howell 1926; Harper 1956). The venter of juveniles also is darker than in adults, with the dark gray basal part of the hairs more evident (Harper 1956). Phenacomys ungava may have 1 or 2 annual molts, although the exact number is not known (Howell 1926). Molting has been reported for adults and subadults captured in July, September, and October (Harper 1956, 1961). The pattern of molt varies from melanin deposits on the rump, sides, chest, and posterior venter (subadult in July); midventer (adult in July); shoulder and in small areas (adult in July); to the entire dorsum from the crown to the rump (subadult in September—Harper 1961). Phenacomys ungava exhibits age-related variation in cranial and dental morphology (Foster and Peterson 1961). In juveniles, the crania are weak and rounded and ridges are absent, auditory bullae are relatively small, incisive foramina are short, zygomata are compressed, the interorbital region is relatively wide, and the rostrum is short (Foster and Peterson 1961). Among 9 cranial measurements, the length of the rostrum was found to be the best assessment of age; in captive individuals, the rostrum grows rapidly in length during the first 150 days and maximum length is reached at about 1 year of age (Foster and Peterson 1961). The length of the rostrum in juveniles ranges from 6.0 to 8.2 mm, and in adults from 8.2 to 9.8 mm (Miller 1897b; Foster and Peterson 1961). The molars in young P. ungava are rootless and not completely extended; roots develop as the molars extend, and, when the molars are fully extended and cease growing, the roots are closed completely (Howell 1926; Foster and Peterson 1961). As individuals age, the crowns of the molar teeth are worn so that in the oldest individuals, the crown is nearly worn to the roots (Foster and Peterson 1961). Wild-caught and captive P. ungava differ in their rate of growth (Foster and Peterson 1961). In captivity, the lengthening of the rostrum was more rapid and the growth of the molars slower compared with individuals captured in the wild. The age at which full extension of the molars occurred in P. ungava in captivity was about 1 year of age and was between 8 and 10 months of age for noncaptive animals; the difference in growth may be correlated with diet (Foster and Peterson 1961).

ONTOGENY AND REPRODUCTION Ontogeny.—Phenacomys ungava born in captivity are altricial (pink, hairless, and blind) and have a mean mass of

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2.4 g (range 2.0–2.7 g) and mean crown–rump length of 3.0 cm. Vibrissae are visible by the end of day 1, and by day 3, the pigmentation of the dorsum changes from pink to graypink to blue-black. On day 2, the young can vocalize and the vibrissae are 3 mm in length. On day 6, fine fur has covered the body and the young are able to right themselves. Young are able to crawl by day 8 and the incisors have erupted by day 9. The eyes open on day 14 and young begin to eat green vegetation. Although young are weaned by day 17, some individuals continue to nurse until day 19. Young gain mass at about 0.5 g per day until they are more than half grown, with the mature body mass of 27 g attained at approximately 100 days of age (Foster 1961). Based on cranial and dental morphology (tooth wear), maximum life span is about 4 years (Foster and Peterson 1961). Reproduction.—Male Phenacomys ungava do not become fully sexually mature their 1st summer. In general, testes of juvenile males range from 2 to 4 mm, and those of older individuals measure 6–8 mm (Foster 1961). Testes sizes (mm) between June and October were: 7.5 by 5 (June, adult), 8.0 by 5.5 (July, adult), 3.5 by 2.5 (August, immature), 2.0 by 1.5 and 2.5 by 1.5 (September, subadult), and 2.5 by 2.0 (October, subadult—Harper 1956, 1961). In the Hudson Bay area, males breed through August because males captured after this time had ascending or ascended testes (Edwards 1963). Female P. ungava were reproductively active (vagina open) in late June and mid-July and nonbreeding (vagina closed) in late August and October (Harper 1956). Pregnant female P. ungava are known from June to early September (Saunders 1927; Jackson 1938; Weaver 1940; Banfield 1941; Harper 1956, 1961; Soper 1961b; Edwards 1963; Youngman 1975). Mean gestation time is 21 days (19–24 days—Foster 1961). Litter size ranges from 2 to 8 (Preble 1908; Saunders 1927; Jackson 1938; Weaver 1940; Banfield 1941; Harper 1956, 1961; Smith and Foster 1957; Foster 1961; Soper 1961b; Edwards 1963; Youngman 1975). Mean litter sizes are 4.8 (Foster 1961) and 4.9 (Smith and Foster 1957), but are smaller (3.8) for females less than 1 year old or born at the beginning of the reproductive season compared with litters of females of at least 1 year of age (5.9—Foster 1961). Females become sexually mature before males at Ft. Churchill, Manitoba (Foster 1961). The absence of reproductively active individuals from late August–early September to late October suggests that 1 litter per year is likely born in mid-June or early July (Foster 1961). Juveniles become sexually mature at 4–6 weeks of age and some female young-of-the-year breed by the end of the 1st summer (late July), although the breeding season of juveniles may end several weeks before that of adult P. ungava (Foster 1961). Presence of placental scars in females captured in September in Keewatin, Canada, indicates that a 2nd litter may be born in August (Harper 1956).

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ECOLOGY Population characteristics.—Population characteristics of Phenacomys ungava are not well studied. Sex ratio as determined by capture is biased toward females (1 male : 1.4 females) and independent of capture method (Naylor et al. 1985). Age ratio is biased toward juveniles (1 adult : 1.9 juveniles [Naylor et al. 1985] and 1 adult : 1.4 juveniles [Foster and Peterson 1961]) and the type of trap or trapping method may influence age structure of animals captured (Naylor et al. 1985). In Ontario, more juveniles were sampled in mixed and disturbed forest, suggesting that these forests may serve as dispersal sinks (Naylor et al. 1985). Demography data generally are available only for summer months; the earliest record is that of a young adult found dead in early February (Merriam 1889). Adults are present from May to October, juveniles appear in July and August, and subadults are present from July to October (Miller 1897a; Preble 1902a; Saunders 1926, 1927; Banfield 1941; Harper 1956, 1961; Smith and Foster 1957; Foster 1961; Foster and Peterson 1961; Soper 1961a, 1961b; Jannett and Oehlenschlager 1997). Phenacomys ungava often is noted as being ‘‘rare’’ or ‘‘uncommon’’ (e.g., Merriam 1889; Saunders 1927; Foster 1961; Jannett and Oehlenschlager 1997); however, it frequently is common locally (e.g., Edwards 1963; Naylor et al. 1985). Although regular population fluctuations have not been reported, populations of P. ungava may show dramatic increases. Over a 7-year period (1951–1957) in Manitoba, captures increased from 0 in year 1 to 192 in year 5, and decreased to 1 in year 7 (Smith and Foster 1957; Foster 1961). Large numbers of individuals captured and observed in Quebec and Manitoba in the early 1950s also suggested a population explosion of P. ungava (Peterson 1956). In Ontario, P. ungava was captured only on study plots 2–3 years after black spruce (Picea mariana) were clear-cut and dry, shrubby habitat was present; the number of individuals per hectare ranged from 0.3 to 0.7 (Martell and Radvanyi 1977). P. ungava was captured in mature and regenerating forests of varying age, except the oldest (20- to 25-year-old) regenerating forest, and capture rates were highest in 10- to 15-year-old regenerating forest after clearcutting (live traps ¼ 2.84 animals/2,000 trap nights; pitfall traps ¼ 1.39 animals/2,000 trap nights) and mature forest (live traps ¼ 2.10 animals/2,000 trap nights; pitfall traps ¼ 0.45 animals/2,000 trap nights [Pearce and Vernier 2005]). Phenacomys ungava was more common (based on capture rate of number of individuals per 100 trap nights) in Ontario jack pine (Pinus banksiana) forest monocultures with a relatively continuous understory of ericaceous (requiring acidic soil) shrubs (X¯ ¼ 4.40) and lowest in disturbed forest (X¯ ¼ 0.58) and mixed forest (X¯ ¼ 0.10— Naylor et al. 1985). In the coniferous forest of Ontario, the

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relative abundance of P. ungava is correlated with the amount of cover of sheep laurel (Kalmia angustifolia) and lowbush and Canadian blueberry (Vaccinium angustifolium and V. myrtilloides, respectively—Naylor et al. 1985), suggesting that P. ungava may play an important role in recycling nutrients in jack pine–sheep laurel habitats. In the western part of the distribution (Yukon), the niche breadth for P. ungava was correlated with population density; as the density increased, individuals dispersed into more habitats (Krebs and Wingate 1976). The number of individuals captured per 100 trap nights ranged from 0.05 to 0.37 with the highest numbers in willow (Salix), open spruce (Picea)–willow, shrub birch (Betula)–meadow, and balsam poplar (Populus balsamifera) habitats. Space use.—Phenacomys ungava is found in diverse habitats of the boreal forest ecosystem in the Northern Hemisphere. A common characteristic among the diversity of the habitats is the presence of ground cover (Smith and Foster 1957; Foster 1961; Naylor et al. 1985) and a preference for dry, open seral vegetation (e.g., Edwards 1955; Foster 1961). In the eastern part of its distribution, P. ungava is found in habitat associations with coniferous forests of pines or spruces, or both (Howell 1926; Saunders 1927; Foster 1961; Naylor and Bendell 1983; Naylor et al. 1985). In Labrador, P. ungava is recorded from semitundra, but also conifer–lichen woodland and black spruce muskeg (Weaver 1940; Gabbutt 1961). The habitat of P. ungava in Quebec is comprised of jack pine and black spruce, with white birch (Betula papyrifera) and trembling aspen (Populus tremuloides—MacLeod and Cameron 1961) and blueberry, Labrador tea (Ledum groenlandicum), or sheep laural dominating as ground cover (Foster 1961). Preferred habitat in Ontario is jack pine forest with an understory of ericaceous shrubs (e.g., sheep laurel and blueberry— Naylor et al. 1985; Pearce and Vernier 2005), although individuals also have been captured in dry, shrubby areas in clear-cut forest (Martell and Radvanyi 1977) and spruce– birch forest, sphagnum bogs, and among rocks (Saunders 1927). In the region west of Hudson Bay, P. ungava is known to occur in a variety of habitats, such as scrubby vegetation, specifically willow; open forest (spruce or Labrador tea–larch [Larix]–spruce); dry, rocky areas, such as rocky ridges surrounded by wet tundra; climax tundra; and open peat bogs and muskegs (Preble 1902a; Harper 1956; Smith and Foster 1957; Wrigley 1974). P. ungava in this region is absent or less frequently found in grassy areas or meadows (Preble 1902a; Smith and Foster 1957; Foster 1961) and sandy tundra (Smith and Foster 1957). In the western part of its distribution, P. ungava occupies closed spruce, open spruce, deciduous forest, and shrub habitats (Krebs and Wingate 1976). These habitats include closed spruce–willow, closed spruce–buffaloberry (Shepherdia), closed spruce, open spruce–willow, open spruce–birch, open spruce–buffaloberry, aspen, balsam poplar, willow

45(899)—Phenacomys ungava

shrub habitat, and shrub birch–willow (Preble 1908; Banfield 1941; Douglass and McDonald 1976; Krebs and Wingate 1976). Descriptions of habitat and location of capture also include references to marsh (Preble 1908), as well as brush piles, logs, and willow clumps (Banfield 1941). Phenacomys ungava uses winter and summer nests. Winter nests often are located above ground at the base of a bush, stump, or rock; they are occupied only during the winter because the absence of snow cover provides little protection (Foster 1961). The winter nest is about 15 cm in diameter and is constructed of leaves, twigs, grass, and other vegetation (Foster 1961). Summer nests are located under cardboard, boards, planks, or rocks; in stumps, logs, or the roots of small trees; under mounds left by rotten stumps; and occasionally in peat (Miller 1897a; Smith and Foster 1957; Foster 1961; Edwards 1963). The summer nest is smaller than the winter nests, measuring about 10 cm in diameter (Foster 1961), and is placed 20 to 26 cm below ground (Miller 1897a; Smith and Foster 1957; Foster 1961). Materials used to construct summer nests generally are soft and include grass, moss, leaves, and plant down, although other found materials may be used (e.g., shredded cardboard, shredded paper, and cotton—Smith and Foster 1957; Foster 1961). The burrow system consists of a single nest (Foster 1961; Edwards 1963) located at the end of a simple, short (, 0.9-m) tunnel system (Miller 1897a; Smith and Foster 1957; Foster 1961; Edwards 1963), and a latrine or defecation chamber placed , 30 cm from the nest (Smith and Foster 1957; Foster 1961; Edwards 1963). Fresh feces are greenish (Harper 1956) and have a characteristic aromatic odor (Smith and Foster 1957; Foster 1961). In captivity, P. ungava constructed burrow systems from materials provided; over a 3-week period, individuals in 1 cage moved about 2,100 g of willow twigs into a 30-cm wooden cube with cotton (Foster 1961). P. ungava generally defecated in the corner of cage farthest from the nest, but commonly defecated in water provided for drinking (water bowl or drinking tube); this behavior may be important in disease transmission (Foster 1961). Diet.—Phenacomys ungava is an herbivore. During winter and summer, P. ungava caches food (Foster 1961), placing it in piles at entrances to burrows (Foster 1961; Naylor et al. 1985), under stumps and pieces of metal on the ground (Miller 1897a), and in shallow burrows and under rocks (Edwards 1963). Caches placed in holes or cavities of fresh shoots of willow, buffaloberry, blueberry, or bearberry (Arctostaphylos) often indicate the presence of Phenacomys (Smith and Foster 1957). The plant material cached in summer is primarily soft and brittle, whereas that in winter is generally tough and course (Foster 1961). Fungi also may comprise part of the diet of P. ungava (Harper 1956). In general, the type of food found in caches depends largely on availability. At 1 site, caches (n ¼ 215) were

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MAMMALIAN SPECIES

comprised of willow (68%), blueberry (9%), soapberry (Shepherdia; 9%), dwarf birch (Betula glandulosa; 6%), bearberry (6%), crowberry (Empetrum; 1%), and fireweed (Epilobium; 1%). In contrast, at another site, soapberry comprised 50% of the caches and may be eaten more in autumn than in summer (Foster 1961). The diet varies by season and region, and is dependent on the local availability of plant matter. In Quebec, the diet of P. ungava in early spring was comprised of vascular leaves (70%), bark and stems (12%), and digested material (14%— Coˆt´e et al. 2003). In late summer of the same year, the diet included vascular leaves (79%), seeds (15%), and digested material (5%), but in the following year had shifted to berries (95%), seeds (4%), and vascular leaves (1%). In summer, caches of P. ungava contain berries, leaves, twigs, and succulent parts of blueberry, northern bilberry (Vaccinium uliginosum), lowbush blueberry, common bearberry (Arctostaphylos uva-ursi), red bearberry (A. rubra), alpine bearberry (A. alpina), Canada buffaloberry or soapberry (Shepherdia canadensis), sheep laurel, arctic willow (Salix arctica), northern willow (S. arctophila), grayleaf willow (S. glauca), sageleaf willow (S. candida), dwarf birch, paper birch (B. papyrifera), and three-toothed cinquefoil (Sibbaldiopsis tridentata—Miller 1897a; Foster 1961). Other less common plants found in caches include red crowberry (Empetrum nigrum), fireweed (Epilobium angustifolium), bog-rosemary (Andromeda polifolia var. glaucophylla), net-leaved willow (Salix reticulata), mountain cranberry (Vaccinium vitis-idaea), and bakeapple (Rubus chamaemorus—Foster 1961). The winter diet, based on stomach contents, caches, and plant material found near burrows in spring, is comprised of bark (willow and dwarf birch), seeds, and possibly lichens (Cladonia—Foster 1961). The bark of sheep laurel, blueberry, bilberry, and common bearberry also may be winter foods (Banfield 1974), although sheep laurel generally is thought to be toxic to vertebrates (Naylor et al. 1985). Seeds (a high-energy food item) may be an important component of the diet in winter due to the lack of fresh vegetation during the season (Coˆt´e et al. 2003). Phenacomys ungava has been captured with plant material present in the mouth (Harper 1956, 1961), such as mountain cranberry (Harper 1956). Stomach contents consisted of finely chewed plant material (Edwards 1963). Diseases and parasites.—Ectoparasites (fleas; Siphonaptera) include Megabothris asio, M. groenlandicus, M. quirini, Malaraeus penicilliger athabascae, Peromyscopsylla hamifer hamifer, and Epitedia wenmanni (Foster 1961; Gabbutt 1961; Edwards 1963). The bot fly Cuterebra (Diptera) also occurs on Phenacomys ungava (Foster 1961). Mites (Acarina) include Haemogamasus alaskensis, H. ambulans, Hirstionyssus isabellinus, Laelaps alaskensis, Haemolaelaps glasgowi, and Listrophorus (Harper 1956, 1961). The sucking louse Polyplax abscisa (Anoplura) also

25

infests P. ungava (Harper 1956). P. ungava is a host for the cestodes Paranoplocephala bairdi and P. macrocephala (Cestoda: Anoplocephalidae—Schad 1954; Haukisalmi and Henttonen 2000; Haukisalmi et al. 2005), and the nematode Heligmosomoides polygurus americanus (Nematoda: Heligmosomatidae—Schad 1954; Rausch and Rausch 1973; Behnke et al. 1991), which are the only records of endoparasites for this species. Although the original host of P. bairdi was identified as the Microtus chrotorrhinus (rock vole—Schad 1954), this determination was found to be in error and the host was reidentified as P. ungava (Peterson 1962; Rausch 1976). Listeriosis, an infection caused by bacteria Listeria (Bacilli: Bacillales), was isolated from an individual that died in captivity (Foster 1961). In central Labrador, 60.9% of P. ungava carried the flea M. quirini, but only 8.7% and 4.3% were reported carrying E. wenmanni and M. asio, respectively; the mean number of fleas (M. quirini) per individual was 4.8 with a maximum of 14 (Gabbutt 1961). The sex ratio of M. quirini was biased strongly toward females and may reflect a differential response of female fleas to temperature (Gabbutt 1961). Small areas of tissue on the inside of the skin may be discolored due to the accumulation of blood but are of unknown cause (Harper 1956). P. ungava has been found dead lying in the open or in nests in Manitoba, suggesting that this species may be more vulnerable to cold, disease, or other factors than other arvicoline rodents in the region (Smith and Foster 1957; Foster 1961). Interspecific interactions.—Terrestrial mammals commonly found in association with Phenacomys ungava in northeastern Minnesota include Blarina brevicauda (northern short-tailed shrew), Sorex arcticus (arctic shrew), S. cinereus (cinereus shrew), S. fumeus (smoky shrew), S. hoyi (American pygmy shrew), S. palustris (American water shrew), Condylura cristata (star-nosed mole), Glaucomys sabrinus (northern flying squirrel), Tamias minimus (least chipmunk), T. striatus (eastern chipmunk), Napaeozapus insignis (woodland jumping mouse), Zapus hudsonius (meadow jumping mouse), rock vole, Microtus pennsylvanicus (meadow vole), Myodes gapperi (southern red-backed vole), Synaptomys cooperi (southern bog lemming), and Peromyscus maniculatus (North American deermouse—Jannett and Oehlenschlager 1997). Associations in the Kluane region in Yukon include cinereus shrew, Sorex monticola (dusky shrew), Ochotona princeps (American pika), Lepus americanus (snowshoe hare), northern flying squirrel, Urocitellus parryii (arctic ground squirrel), least chipmunk, meadow jumping mouse, Lemmus trimucronatus (Nearctic brown lemming), Microtus longicaudus (long-tailed vole), M. miurus (singing vole), M. oeconomus (root vole), meadow vole, Myodes rutilus (northern red-backed vole), Synaptomys borealis (northern bog lemming), North American deermouse, and Erethizon

26

MAMMALIAN SPECIES

dorsatum (North American porcupine—Krebs and Wingate 1976). In Churchill, Manitoba, small mammal associations include arctic shrew, cinereus shrew, American pygmy shrew, Lepus arcticus (arctic hare), Canis lupus (wolf), Vulpes vulpes (red fox), Mustela erminea (ermine), Tamiasciurus hudsonius (red squirrel), arctic ground squirrel, meadow jumping mouse, Dicrostonyx richardsoni (Richardson’s collared lemming), meadow vole, southern red-backed vole, northern red-backed vole, Ondatra zibethicus (common muskrat), and northern bog lemming (Smith and Foster 1957; Wrigley 1974). In Labrador, P. ungava was found associated with arctic shrew, cinereus shrew, American water shrew, star-nosed mole, snowshoe hare, red fox, red squirrel, woodland jumping mouse, meadow jumping mouse, Dicrostonyx hudsonius (Ungava collared lemming), meadow vole, northern red-backed vole, southern red-backed vole, and North American deermouse (Jackson 1938; Gabbutt 1961). In Ontario, P. ungava was associated with northern short-tailed shrew, arctic shrew, cinereus shrew, smoky shrew, American pygmy shrew, least chipmunk, rock vole, meadow vole, southern bog lemming, southern red-backed vole, northern red-backed vole, and North American deermouse (Martell and Radvanyi 1977; Pearce and Vernier 2005). Mammals in association with P. ungava in Quebec include northern short-tailed shrew, red squirrel, woodland jumping mouse, southern red-backed vole, and North American deermouse (MacLeod and Cameron 1961). Finally, associations in Northern Territories include meadow vole, Microtus xanthognathus (taiga vole), northern redbacked vole, and northern bog lemming (Douglass and McDonald 1976). Phenacomys ungava is a common prey species for avian predators based on the presence of skull fragments in pellets and direct observation (Smith and Foster 1957; Foster 1961; Edwards 1963; Douglass and McDonald 1976). Common predators include short-eared owls (Asio flammeus), snowy owls (Bubo scandiacus), northern hawk owls (Surnia ulula), and rough-legged hawks (Buteo lagopus—Smith and Foster 1957; Foster 1961; Edwards 1963). Predation by owls and hawks was observed particularly when populations of P. ungava and other arvicoline rodents were high, and some species (e.g., snowy owls) were common winter residents in an area following a summer of high levels of arvicoline populations (Smith and Foster 1957). Avian predators cache carcasses in or near nests (Smith and Foster 1957), and P. ungava comprised 32% of skulls found in owl and hawk pellets (Smith and Foster 1957; Foster 1961). Phenacomys ungava also is prey for several carnivores, including Mustela (weasels—Preble 1902a) and Martes americana (marten); remains of P. ungava were found in 5% of marten scats (Douglass and McDonald 1976).

45(899)—Phenacomys ungava

Although a terrestrial species, the remains of P. ungava have been found in the stomach contents of brook (speckled) trout (Salvelinus fontinalis) in Ontario (Peterson 1956). Miscellaneous.—Phenacomys ungava is captured in live traps (Smith and Foster 1957; Martell and Radvanyi 1977; Pearce and Vernier 2005), snap traps (Martell and Radvanyi 1977; Naylor et al. 1985; Jannett and Oehlenschlager 1997), pitfall traps (Naylor et al. 1985; Pearce and Vernier 2005), and occasionally by hand in their nests (Smith and Foster 1957). Fewer total captures result from the use of pitfall traps (Naylor et al. 1985; Pearce and Vernier 2005), but pitfall traps capture a higher percentage of young individuals (84.4% pitfall traps versus 60.4% snap traps— Naylor et al. 1985). P. ungava has been captured using a variety of baits, including oatmeal and bacon fat (Gabbutt 1961); peanut butter and oatmeal (Naylor et al. 1985); peanut butter, oatmeal, and apple (Jannett and Oehlenschlager 1997); peanut butter, oatmeal, sunflower seeds, and potato (Pearce and Vernier 2005); and ground beef suet, raisins, walnuts, peanut butter, oatmeal, oil of aniseed, and apple (Martell and Radvanyi 1977). Capture success, however, may have a higher correspondence to placement of traps rather than attraction to bait, which was suggested by the orientation of voles caught in snap traps, indicating that animals were crossing traps, rather than trying to get the bait (Naylor et al. 1985). In captivity, P. ungava eats foods native to the area where individuals were captured, including berries, caribou moss (Cladonia), Polygonum vivipare (alpine bistort), Hedysarum mackenzii (sweetvetch), Ledum (Labrador tea–flowers), Cypripedium passerinum (sparrow’s-egg lady’s slipper– seed pods), and infrequently grasses and sedges (Foster 1961). Nonnative foods that are eaten include carrots, apples, turnips, yams, oatmeal, and raisins. Peanut butter, peanuts, and cheese occasionally are eaten, but animal food pellets, lettuce, and cabbage are not consumed. All individuals maintained in captivity developed diarrhea, and the digestive tracts were full of gas. P. ungava in captivity lived a maximum of 784 days (Foster 1961).

BEHAVIOR Phenacomys ungava is terrestrial; captive P. ungava swim, but this type of locomotion generally is avoided (Smith and Foster 1957; Foster 1961). This species is active primarily during twilight or night, or both (Foster 1961). Although activity during the day is reduced in the wild and in captivity, individuals have been observed to be active in daylight (Miller 1897a; Smith and Foster 1957; Foster 1961; Edwards 1963). Foraging activity is highest on rainy, foggy, or windy nights (Foster 1961). Phenacomys ungava is docile when captured and in captivity; individuals are unlikely to bite or attempt to

45(899)—Phenacomys ungava

MAMMALIAN SPECIES

escape, except when females have young (Smith and Foster 1957; Foster 1961). P. ungava becomes accustomed to captivity quickly and is not disturbed by the presence of human observers (Foster 1961). In the laboratory, P. ungava is tolerant of the presence of conspecifics, as well as other species of voles. No species was observed to be dominant, but, in general, P. ungava avoids direct encounters (Foster 1961; Harper 1961). In captivity during winter months, Phenacomys will share nests with as many as 5 individuals (Foster 1961). Aggressive behavior is absent except during the breeding season (Foster 1961). During the breeding season, captive males are aggressive toward other males and will inflict injuries; however, evidence of this behavior has not been documented in wild-caught individuals (Smith and Foster 1957; Foster 1961).

GENETICS The diploid number (2n) of chromosomes in Phenacomys ungava is 56 and the fundamental number (FN) is 58 (Matthey 1957). Autosomal pairs consist of 27 acrocentric and submetacentric chromosomes. The X chromosome is large and submetacentric and the Y chromosome is small and acrocentric. Karyotypes of P. ungava and P. intermedius are similar; the diploid numbers are identical, but the fundamental numbers differ due to 1 pair of autosomal chromosomes that is single-armed in P. ungava and biarmed in P. intermedius (McAllister and Hoffmann 1988; George 1999b; O’Brien et al. 2006).

CONSERVATION Phenacomys ungava is listed as ‘‘Least Concern’’ on the 2008 International Union for Conservation of Nature and Natural Resources Red List of Threatened Species based on its nearly ubiquitous distribution in Canada and stable population structure (Linzey et al. 2008). It occurs in numerous protected areas, and no major threats to this species are known. P. ungava frequently is noted in the literature as being ‘‘rare’’ or ‘‘uncommon’’ (e.g., Merriam 1889; Saunders 1927; Foster 1961; Jannett and Oehlenschlager 1997), and individual populations may thus be highly susceptible to localized habitat destruction and degradation, as well as parasitism and disease (Smith and Foster 1957). Others have suggested that P. ungava may be more common than trapping results indicate (Smith and Foster 1957; Foster 1961; Douglass and McDonald 1976) or that it exhibits periods of cyclic population abundance (Smith and Foster 1957; Foster 1961; Naylor et al. 1985; Jannett and Oehlenschlager 1997). Because of the association of P. ungava with mature forest of high economic value (Pearce and Vernier 2005), this species may be a potential bioindicator for pole jack pine, mature jack pine, and

27

mature lowland conifer boreal forest biomes (McLaren et al. 1998; Pearce and Vernier 2005).

REMARKS Although Phenacomys intermedius and P. ungava both are poorly studied, very little primary literature focusing on P. ungava as a distinct species is available compared to information on P. intermedius. Future research on genetics, morphology, population ecology, and behavior of P. ungava would provide information on this potential bioindicator species. Additional information on natural history of this species such as specific habitat might clarify the importance of the species as a bioindicator of sustainable boreal forest management, given the specific association of the species with mature forest of high economic value (e.g., jack pine forest—Pearce and Vernier 2005). Another potential importance of the species is due to its preference for consuming bark of sheep laurel present in jack pine forests; this shrub is toxic for most vertebrates and it is rarely consumed, thus, P. ungava may play an important role recycling nutrients in this type of forest (Naylor et al. 1985).

LITERATURE CITED ANDERSON, R. M. 1942. Canadian voles of the genus Phenacomys with description of two new Canadian subspecies. Canadian FieldNaturalist 56:56–61. ANDERSON, R. M. 1947. Catalogue of Canadian Recent mammals. National Museum of Canada Bulletin, Biological Series 102:1– 238. BANFIELD, A. W. F. 1941. Notes on Saskatchewan mammals. Canadian Field-Naturalist 55:117–123. BANFIELD, A. W. F. 1974. The mammals of Canada. University of Toronto Press, Toronto, Ontario, Canada. BANGS, O. 1900. Three new rodents from southern Labrador. Proceedings of the New England Zoological Club 2:35–41. BEHNKE, J. M., A. E. KEYMERN, AND J. W. LEWIS. 1991. Heligmosomoides polygurus or Nematospiroides dubius? Parasitology Today 7:177–179. BELL, C. J., ET AL. 2004. The Blancan, Irvingtonian, and Rancholabrean mammal ages. Pp. 232–314 in Late Cretaceous and Cenozoic mammals of North America: biostratigraphy and geochronology (M. O. Woodburne, ed.). Columbia University Press, New York. CHAVEZ, A. S., AND G. J. KENAGY. 2010. Historical biogeography of western heather voles (Phenacomys intermedius) in montane systems of the Pacific Northwest. Journal of Mammalogy 91:874–885. COˆTE´ , M., J. FERRON, AND R. GAGNON. 2003. Impact of seed and seedling predation by small rodents on early regeneration establishment of black spruce. Canadian Journal of Forest Research 33:2362–2371. COWAN, I. MCT., AND C. J. GUIGUET. 1978. The mammals of British Columbia. 7th printing. British Columbia Provincial Museum, Handbook 11:1–414. CROWE, P. E. 1943. Notes on some mammals of the southern Canadian Rocky Mountains. Bulletin of the American Museum of Natural History 80:391–410. DOUGLASS, R. J., AND D. MCDONALD. 1976. A northern record for the heather vole, Phenacomys intermedius, in the Northwest Territories. Canadian Field-Naturalist 90:82–83. EDWARDS, R. L. 1963. Observations on the small mammals of the southeastern shore of Hudson Bay. Canadian Field-Naturalist 77:1–12.

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Associate editor of this account was C. WILLIAM KILPATRICK. Editor was MEREDITH J. HAMILTON.