The Canadian Field-Naturalist (E-Journal)
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Diet of St. Lawrence Estuary Beluga (Delphinapterus leucas) in a changing ecosystem
Get PDFEcosystems and community structure fluctuate over time as a result of natural and anthropogenic factors that may affect prey availability and population dynamics. Most of what we know about St. Lawrence Estuary (SLE) Beluga (Delphinapterus leucas) diet comes from stomach contents collected 80 years ago mainly from a hunting site that Beluga no longer use. How reflective these data are of Beluga diet at other sites and at the current time is unknown. In the context of the recent population decline, general information of prey species alone may help identify useful conservation actions for potentially important prey or habitats. Here, we examined the diet of SLE Beluga using digestive tracts collected from carcasses recovered over the past 30 years, in the context of historical diet data and recent changes in the St. Lawrence ecosystem. We showed they have a varied diet composed of fish and invertebrates generally <30 cm in length, and that adult males and females differ in their summer diet in a way that is consistent with the sex segregation observed in this population. Our results also indicate that polychaete worms, squid, and cod are still among the most prevalent prey, and that species such as redfish (Sebastes spp.) might be important prey items. This study shows that Beluga diet has changed since the 1930s, and that prey from digestive tracts identified to species are valuable for making comparisons to the past, and for improving applications of molecular analyses, such as stable isotopes and fatty acids
"Birds of Saskatchewan" by Alan R. Smith, C. Stuart Houston, and J. Frank Roy, 2019. [book review]
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"The Voices of Marine Mammals: William E. Schevill and William A. Watkins: Pioneers in Bioacoustics" edited by Christina Connett Brophy, 2019. [book review]
Get PDFSharp-tailed Grouse (Tympanuchus phasianellus) population dynamics and restoration of fire-dependent northern mixed-grass prairie
Get PDFCase studies of Sharp-tailed Grouse (Tympanuchus phasianellus) population dynamics before and during re-introduction of fire to northern mixed-grass prairies that lacked fire for multiple decades are unavailable. At a 108-km2 northern mixed-grass prairie refuge in North Dakota, fire was suppressed from the early 1900s through late 1970s. Nine management units (total area 16.8 km2, 15.7% of the refuge) received initial prescribed fire treatments during 1979–1984. The mean annual density of male Sharp-tailed Grouse attending leks on these units during 1981–1985 (9.0 males/km2) was twice that on the same units during 1961–1965 (4.2 males/km2), amid the fire exclusion era; nonoverlap of 90% CIs encompassing the means suggested a significant treatment effect. However, densities of males on units managed without prescribed fire during 1961–1965 and 1981–1985 did not change between the two periods. By 1987, fire had been re–introduced to >50% of the refuge overall. Mean annual abundance (i.e., total numbers) of lekking males on the entire refuge did not differ between 1961–1965 and 1981–1985 but was significantly greater during 1989–1993 than during 1961–1965 and 1981–1985. Changes in density and abundance of lekking males coincided with fire-induced reductions in woody cover and increases in herbaceous cover. Our study illustrates the marked capacity of Sharp-tailed Grouse to respond to reductions of tree and shrub cover resulting from prescribed fire in northern mixed-grass prairie and the species’ attraction to habitat disturbance in general
Sixty years of White-tailed Deer (Odocoileus virginianus) yarding in a Gray Wolf (Canis lupus)–deer system
Get PDFThis article synthesizes information from over a six-decade period of studies of White-tailed Deer (Odocoileus virginianus) use of a winter yard and subject to Gray Wolf (Canis lupus) predation in northeastern Minnesota. It also adds spring migration data from 35 adult female deer and fawns studied there during 1998, 1999, 2001, 2014, and 2017. Twenty-nine of these deer migrated in spring a mean distance of 29 km (SE = 4), a maximum distance of 78 km, and at a mean bearing of 83° (SE = 12; range 21–348). These findings are similar to those from 49 deer (both sexes) from the same yard studied during 1974–1984, that migrated a mean distance of 25 km (SE = 1.8) and a mean bearing of 77° ± 4 SE. Between the two periods, the wolf population fluctuated considerably, the winter range of deer in the area where these deer spent summer greatly diminished, and both derechos and fires disturbed the habitat. This study attests to the selective advantage of the migratory tradition of deer in this yard
High reliance on a diet of Moose (Alces americanus) by Eastern Coyotes (Canis latrans var.) in Cape Breton Highlands National Park, Nova Scotia, Canada
Get PDFEastern Coyote (Canis latrans var.) scats were collected along transects in Cape Breton Highlands National Park, Nova Scotia, Canada, from May 2012 to August 2013 to determine diet. Based on 294 scats, Moose (Alces americanus) remains made up the highest percentage by volume in scats during fall, winter, and spring. During the summer, Moose remains were found in over 30% of scats (18% by volume), although fruit and berries were more commonly found. No other study has documented such high annual use of Moose. As there was no evidence that the consumed Moose were killed by Coyotes, presumably Coyotes scavenged Moose that had died of natural causes
Interactions between Elk (Cervus canadensis) and invasive Feral Swine (Sus scrofa) on the Canadian Prairies
Get PDFElk (Cervus canadensis), a native species on the Canadian Prairies, makes extensive use of agro-ecosystems. Feral Swine (Sus scrofa) is a highly invasive species introduced to western Canada in the late 1980s; it is now endemic and rapidly expanding its range across the Canadian Prairies. Here we consider a series of 14 trail camera photos obtained near St. Breiux, Saskatchewan on 18 November 2018. Taken at night over 67 minutes, they document close, non-aggressive encounters between Elk and Feral Swine. We believe that these are the first documented observations of close (<5 m) interactions between free-ranging Elk and Feral Swine in North America that include no indications of fear response or displacement of one species by the other. These types of indirect interactions among species have important implications in terms of potential risk of disease transmission and interpreting potential ecological impacts of invasive Feral Swine on native large mammals
Do turtle warning signs reduce roadkill?
Get PDFRoadkill is a serious threat for many species of freshwater turtles. One of the most common road mitigation tools is wildlife warning signs to alert drivers. These warning signs have commonly been used for large mammals, although there is little evidence that they are effective in reducing roadkill. We tested the effectiveness of turtle warning signs at four known roadkill hotspots along a provincial highway in eastern Ontario and compared the results with four control sites on a nearby major road in a before-after-control-impact (BACI) study. We found 30 dead turtles in the four hotspots in 2017 before the signs were installed and 27 in 2018 after the signs were installed. The number of turtles killed on the road after the signs were installed did not change significantly (χ21 = 1.1, P > 0.2). Although turtle warning signs may alert some drivers, they should not be considered a replacement for more effective road mitigation tools, such as wildlife fencing and crossing structures
Axanthism in Green Frogs (Lithobates clamitans) and an American Bullfrog (Lithobates catesbeianus) in Maine
Get PDFWe document eight cases of axanthism in Green Frogs (Lithobates clamitans) and one case in an American Bullfrog (Lithobates catesbeianus) in Maine. Although this mutation has been previously reported for both species, this is the first confirmed documentation of “blue” L. clamitans and L. catesbeianus from Maine