Currently there are 6 stocks of walrus recognised in Canada (2 of which are shared with Greenland), 3 in Greenland (2 of which are shared with Canada), and 2 in the eastern North Atlantic. The location of the 9 recognised stocks can be seen on the maps below.
Historically, walrus occupied Canadian waters on the east coast from Nova Scotia to perhaps 85°N and from the boundary with Greenland to roughly 100°W, but their range now is smaller and their distribution more discontinuous. The Canadian Department of Fisheries and Oceans (DFO) and the North Atlantic Marine Mammal Commission (NAMMCO) currently recognize two “genetic populations” and seven walrus stocks in Canada: the High Arctic population which includes the Baffin Bay (BB), West Jones Sound (WJS), and Penny Strait-Lancaster Sound (PS-LS) stocks, and the central Arctic population which includes the north and central Foxe Basin (N-FB, C-FB) and Hudson Bay-Davis Strait (HB-DS) stocks (see map) (DFO 2013, Stewart et al. 2013c, NAMMCO 2013, Shafer et al. 2013, Stewart 2008). The relationship between these stocks and the seventh stock, the South & East Hudson Bay (S&E-HB) stock is not clear at the present time (DFO 2013).
The high Arctic stocks are differentiated from each other in a number of ways. The Baffin Bay stock can be separated from West Greenland walruses through genetics. The West Jones Sound (WJS) stock, is differentiated from the Baffin Bay by seasonal distribution and tag movements, and the Penny Strait-Lancaster Sound (PS-LS) stock, is separated from West Jones Sound by distribution and tag movements and from Baffin Bay by limited lead isotope data (Stewart 2008).
The two stocks in Foxe Basin are distinguished from each other and from HB-DS on the basis of lead isotope and trace element profiles (Outridge and Stewart 1999, Outridge et al. 2003). Local Inuit also distinguish between two types of walrus in Foxe Basin on the basis of size, colour and distribution (DFO 2002). However, there is a lack of genetic differentiation between Foxe Basin and HB-DS stocks. There may be some male-mediated genetic exchange between FB and the HB-DS and SE-HB Bay stocks, which could indicate a single interbreeding population (Shafer et al. 2013).
In the summer, walruses from each of these stocks are found along the coasts in the area they are named for. In the winter, their distribution is more limited. Wintering areas for the high Arctic stocks are in the Cardigan Strait–Fram Sound area at the west end of Jones Sound, around Dundas Island, the floe edges of Jones and Lancaster sounds, and in the North Water polynya between approximately 69° and 77° N on the Greenland coast (Stewart 2008).
Further south, walrus from the HB-DS stock winter in Cumberland Sound and other areas around south Baffin Island (Stewart et al. 2013b), while some south Baffin walrus winter off west Greenland (Dietz et al. 2013). Walrus in Foxe Basin generally winter at the floe edge around Rowley Island (Stewart 2008).
As in Canada, walruses were previously much more abundant in Greenland than they are today, and were part of one large population (Witting and Born 2005). Currently, three stocks of Atlantic walrus occur in Greenland: the northwest or Baffin Bay stock, the West Greenland-Southeast Baffin Island “component” of the Hudson Bay-Davis Strait stock, and the East Greenland stock. (Wiig et al. 2014). The three stocks have been differentiated on the basis of genetics, distribution and migration patterns (Witting and Born 2013). Two of these stocks, the northwest/Baffin Bay and the West Greenland, are shared with Canada.
The northwest/Baffin Bay stock are found in the coastal waters of Northwest Greenland and the northern reaches of the Canadian Arctic Archipelago. This stock is a subunit of the former North Water population (Andersen et al. 2013).
These walruses, however, are absent from coastal areas of NW Greenland during the open water season in August- September, as they spend the summer along the eastern and southern coast of Ellesmere Island (Canada) and in the Canadian High Arctic archipelago (Stewart et al. 2013a). It is not known whether these walruses travel into Jones or Lancaster Sounds. Sometime in the fall they reappear in the Qaanaaq area of Greenland.
A survey in the North Water in May of 2009 and 2010 found most of the walruses distributed roughly in a belt from Greenland across to Ellesmere Island in the southern part of the North Water at a latitude of about 76° 30’N over both shallow and deep (>500m) water. Only three sightings were made north of 77° N (Heide-Jorgensen et al. 2012).
The West Greenland stock of walrus occurs off the central coast of West Greenland at the edge of the Baffin Bay pack ice from about 66° N to 70° N from fall to spring (Witting and Born 2005). Based on satellite tracking data, it is now clear that walruses in West Greenland are part of the larger Hudson Bay – Davis Strait population that summers primarily around Baffin Island (Dietz et al. 2013).
Along the eastern coast of Greenland, walruses occur year-round, and are mainly distributed inside the National Park of North and Northeast Greenland, north of the entrance to Scoresby Sound (about 71° N) (Witting and Born 2013). There is very limited exchange between the East Greenland walruses and neighbouring populations, such as the West Greenland, North Water, and the Svalbard-Franz Land populations (Witting and Born 2005).
Information on distribution and studies of movement and genetics have shown that there is a common stock of Atlantic walruses found in the Svalbard and the Franz Josef Land archipelagos in which most of the males summer in Svalbard and most females and calves remain in north-eastern parts of Svalbard and the Franz Josef Land area (Wiig et al. 2014, Lydersen and Kovacs 2013, Freitas et al. 2009).
While there has been a single documented exchange of walrus from East Greenland to Svalbard (Born and Gjertz 1993), this is likely rare. Walruses from East Greenland and Svalbard-Franz Josef Land differ genetically and are distinct stocks (Wiig et al. 2014).
The relation between the Svalbard-Franz Josef Land stock and walruses found further east around Novaya Zemlya, and in the Laptev, south-eastern Barents, Pechora and White Seas is uncertain.
As mentioned above, Atlantic walruses in Franz Josef Land (Russia) and Svalbard (Norway) belong to a single population (Freitas et al. 2009). Walruses are also found south and east of Franz Josef Land, around Novaya Semlya and into the southern Barents, Pechora and Kara Seas (Wiig et al. 2014, Glazov et al. 2013). In a recent survey of the Pechora Sea, male walruses were found hauled out at three sites: one on Vaygach Island and two sites on Matveyev Island (Lydersen et al. 2012). Since no females or calves were seen during the survey, the population must be using a larger area than that surveyed.
Walruses found further east in the Laptev Sea are more closely related to the Pacific walrus than the Atlantic (Lindqvist et al. 2008).