A Test of Interspecific Effects of Introduced Eastern Grey Squirrels, Sciurus carolinensis, on Douglas's Squirrels, Tamiasciurus douglasii, in Vancouver, British Columbia

We compared the effects of absence and presence introduced Eastern Grey Squirrels (Sciurus carolinensis) on the demography of native Douglas’s Squirrels (Tamiasciurus douglasii) in two urban parks in Vancouver, British Columbia: Ecological Reserve #74 in Pacific Spirit Regional Park (Douglas’s Squirrel only) and Stanley Park (Douglas’s and Eastern Grey squirrels). Based on the exploitative competition hypothesis, we predicted that in the presence of introduced Eastern Grey squirrels, Douglas’s Squirrels would occur at lower densities, have larger home ranges, lower body mass, and poorer reproduction. Using mark-recapture methods, we found no differences in density, home range, or body mass of Douglas’s Squirrel between parks. However, the proportion of breeding Douglas’s Squirrels was higher in Ecological Reserve #74 in the absence of Eastern Grey Squirrel, than in Stanley Park. We found no evidence that Eastern Grey Squirrels are displacing Douglas’s Squirrels in Stanley Park, but less conspicuous negative effects such as reduced breeding propensity may still reflect the competitive interactions of the two squirrel species

Differential Footload of Male and Female Fisher, Martes pennanti, in Quebec

We examined the mass, foot area and foot load (mass/surface area) of Fishers (Carnivora: Mustelidae: Martes pennanti) captured during the 2006-2007 commercial fur season in southern Quebec, Canada. Body mass of males (mean = 4.7 kg ± 0.5, n = 37) was significantly larger than that of females (mean = 2.4 kg ± 0.2, n = 40). Similarly, the size of male feet (mean area = 130.5 cm2 ± 10.9, n = 37) was significantly larger than that of females (mean = 95.2 cm2 ± 7.6 SE, n = 40). The resulting footload of males (36.2 g/cm2 ± 6.1, n = 37) was 43% larger than that of females (25.3 g/cm2 ± 2.3, n = 40). These results may help explain the differential behaviour and niche partitioning in this mustelid carnivore

Sex Ratio, Body Mass, and Harvest Rates for Five Sympatric Mammalian Carnivores in the Canadian Prairies

We assessed sex ratio, body mass, and harvest rates for 5 species of carnivores (Mammalia: Carnivora) collected in southern Saskatchewan, Canada during spring and summer 1999-2001. Overall, 647 adult carnivores were collected; captures consisted mostly of Striped Skunk (Mephitis mephitis, 50.7% of captures, 2.6±0.6 kg), Raccoon (Procyon lotor; 28.3%, 6.5±1.3 kg), American Badger (Taxidea taxus, 8.2%, 7.7±1.5 kg), Red Fox (Vulpes vulpes, 7.7%, 4.6±0.6 kg), and Coyote (Canis latrans, 5.1%, 11.0±1.5 kg). Sex ratio (M:F) of captures was male-biased for Raccoon (2.5:1), Striped Skunk (1.7:1), but did not differ from 1:1 for American Badger (2.3:1), Coyote (1.7:1), or Red Fox (2.2:1). For both Striped Skunk and Raccoon, the temporal variation in sex ratio of captures suggests that males were more vulnerable to capture early in the spring than females. Harvest rates were highest for Striped Skunks (range 0.8-2.2 animals/km2) followed by Raccoons (0.4-1.3 animals/km2), American Badgers (0.2-0.5 animal/km2), Red Foxes (0.2-0.4 animal/km2), and Coyotes (0.1-0.4 animals/km2)

Influence of Gender and Den Type on Home Range Shape for Striped Skunks, Mephitis mephitis, in Saskatchewan

We investigated gender differences in shape of home ranges for Striped Skunks, Mephitis mephitis, in southcentral Saskatchewan, Canada, during 1993-1994. Data collected on free-ranging Striped Skunks indicated that shape of female home ranges was unaffected by den type (building versus burrow) and was similar to shape of male home ranges. Moreover, type of maternity den did not influence the position of the den within the home range (inside or outside of core area). We conclude that the distribution of Striped Skunks in summer, and the distribution of their foraging activity, are not affected by the availability of anthropogenic den structures

Does Removal of Duck Nest Predators Affect the Temporal Patterns of Predation for Simulated Nests of Grassland Songbirds?

We tested whether the temporal patterns of songbird nest predation changed following removal of predators of duck nests in North Dakota, USA, 1995-1996. Overall, 2286 simulated nests were deployed of which 951 were equipped with depredation timing devices that recorded the time of day of nest destruction. Predators destroyed 242 timer nests, and 155 depredation events were recorded. Temporal distribution of predation events was uniform over a 24-h period. However, predator groups, identified by using marks left on modeling clay eggs, depredated nests at different times. Mean times of depredation were 07h41, 12h57, 17h50, and 22h47 for small mammals, ground squirrels, birds, and medium-sized mammals, respectively. Daily depredation events occurred earlier on removal versus non-removal sites. However, within each predator group, there was no difference in depredation times between removal and non-removal sites. We suggest that the difference in time of depredation is caused by the differential importance of each predator group on removal versus removal sites, and thus conclude that removing duck nest predators does not affect temporal foraging patterns of smaller predators

Summer Movements and Impact of Individual Striped Skunks, Mephitis mephitis, on Duck Nests in Saskatchewan

Striped Skunks (Mephitis mephitis) are important predators of duck eggs in the Canadian prairies. We estimated the impact of individual Striped Skunks on duck nests by intensive observations of foraging movements and depredation of duck nests in southern Saskatchewan, 1993-1994. Nightly, skunk movements were variable (range 0-20 km per night), and did not differ among seasons for females, or between males and females during the parturition/rearing season. Overall, nightly movement of Striped Skunks averaged 7.4 km for females (SD = 5.9 km, n = 20 females) and 6.7 km for males (SD = 3.2 km, n = 5 males). During 1,873 h of radio-tracking, we observed depredation of 10 duck nests by 8 skunks (7 F, 1 M). Using our observed estimate of one depredation for every 187 h, and averaged nightly activity of 8-10 h per night, we estimated that individual skunks find one duck nest every 19-23 nights. Thus, during the 60-day nesting season for ducks (mid-May to mid-July), individual skunks probably find 2-3 duck nests. These observations reinforce the growing evidence that, at normal duck nest densities (<2.5 nests/ha), depredation of eggs by Striped Skunks is opportunistic, and the impact of Striped Skunks on duck nests is a direct function of Striped Skunk abundance

Do Repugnant Scents Increase Survival of Ground Nests? A Test with Artificial and Natural Duck Nests

Ground-nesting birds typically experience high predation rates on their nests, often by mammalian predators. As such, researchers and wildlife managers have employed numerous techniques to mitigate nest predation. We investigated the use of scents as repellents to deter predators from both artificial and natural ground nests. Survival rates of artificial nests did not differ among six groups of substances (Wald ?2 df = 5 = 4.53, P < 0.48); however the chronology of predation among groups differed. A commercial Coyote urine based deterrent (DEER-D-TERTM), human hair, and Worcestershire sauce were depredated faster than the control (F4,5 = 40.3, P < 0.001). Nest survival of natural nests differed among those groups tested (Wald ?2 df = 2 = 11.8, P < 0.005); the eight mothball treatment decreased survival (Wald ?2 df = 1 = 11.5, P < 0.005), which indicated that novel smells may attract predators or result in duck nest abandonment when coupled with natural duck scent. Chronologies of predation events among treatment groups were not different for natural nests (F2,3 = 1.9, P = 0.22). These findings indicate an interaction between novel scents and predator olfactory cues

Simultaneous Den Use by Arctic Foxes and Wolves at a Den Site in Nunavut, Canada

Arctic foxes (Alopex lagopus) and wolves (Canis lupus) often use similar den sites. Interspecific interactions and competition for den sites are therefore possible among these species. At the Kangowan River in Nunavut, Canada, we observed arctic foxes and wolves simultaneously using a den site for pup-rearing during a two-day period in the summer of 2000. We also found evidence that both species had used the den site in May that year. Interspecific interactions in summer included avoidance, tolerance, and aggression. Foxes and wolves used separate entrances and did not appear to share a common space. Our observations of arctic foxes and wolves occupying a den site concurrently suggest that avoidance and interspecific tolerance may have facilitated coexistence at this den site.Les renards arctiques (Alopex lagopus) et les loups (Canis lupus) s’installent souvent dans des tanières du même genre. Par conséquent, il est possible que chez ces espèces, il y ait des interactions inter-espèces et une certaine concurrence pour l’obtention des tanières. À la rivière Kangowan, dans le Nunavut, au Canada, on a observé des renards arctiques et des loups qui se servaient simultanément d’une tanière pour élever leurs petits pendant une période de deux jours à l’été 2000. On a également trouvé des preuves que ces deux espèces s’étaient servies de la tanière au mois de mai de cette même année. L’été, les interactions inter-espèces prenaient la forme de l’évitement, de la tolérance et de l’agression. Les renards et les loups empruntaient des entrées différentes et ne donnaient pas l’impression de partager des lieux communs. Par ailleurs, nos observations des renards arctiques et des loups qui occupent une même tanière en même temps laissent croire que l’évitement et la tolérance inter-espèces pourraient avoir joué un rôle dans la coexistence à cette tanière

Foraging Behaviours of Wolverines at a Large Arctic Goose Colony

At the large Ross's goose and lesser snow goose colony at Karrak Lake, Nunavut, Canada, we saw wolverines kill two geese, take 13 eggs from 12 goose nests, and take three goose carcasses from two fox dens. Wolverines also made unsuccessful attempts to capture geese and frequently ignored eggs from nests where geese had fled the approaching wolverine. Most foods (all geese killed by wolverines and 80% of the eggs) were cached for later use, whereas few foods were eaten immediately (20% of the eggs and part of a goose taken from a fox den, which was later lost) or lost (all geese taken from fox dens). Wolverines spent little time caching foods (e.g., some foods were never covered), which suggests that recovery of these foods was not crucial to wolverines. When taking foods from fox dens, wolverines were mobbed by foxes; as a result, only one wolverine managed to consume part of a goose carcass taken from a fox den. These observations illustrate the opportunistic nature of wolverines and suggest that their scavenging success may be influenced by how well foods are defended.À l'importante colonie d'oies de Ross et de petites oies des neiges située à Karrak Lake au Nunavut (Canada), on a vu des carcajous tuer deux oies, prendre 13 oeufs dans 12 nids d'oies, et prendre trois carcasses d'oies dans deux terriers de renards. Les carcajous ont aussi essayé, sans succès, de capturer des oies et ils ignoraient souvent les oeufs des nids que les oies avaient fuis à leur approche. La plupart des aliments (toutes les oies tuées par les carcajous et 80 p. cent des oeufs) étaient dissimulés pour utilisation ultérieure, tandis que peu d'aliments étaient consommés tout de suite (20 p. cent des oeufs et une partie d'une oie prélevée dans un terrier de renard, qui a été perdue par la suite) ou perdus (toutes les oies prises dans les terriers de renards). Les carcajous passaient peu de temps à dissimuler les aliments (p. ex., certains n'étaient jamais recouverts), ce qui suggère qu'il n'est pas crucial pour eux de les retrouver. Quand les carcajous prenaient des aliments dans les terriers de renards, ils étaient assaillis par les occupants; en conséquence, un seul carcajou est parvenu à consommer une partie d'une carcasse d'oie prise dans un terrier de renard. Ces observations illustrent la nature opportuniste des carcajous et suggèrent que leur succès de récupération pourrait être influencé par la façon dont les aliments sont défendus