The Canadian Field-Naturalist (E-Journal)
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Range expansion of Fisher (Pekania pennanti) in Nova Scotia
Full text linkFisher (Pekania pennanti) is a medium-sized mesocarnivore that typically occupies mature hardwood and softwood forest where its preferred prey is abundant. In Nova Scotia, Fisher populations are reported as restricted to the mainland; they have been absent from Cape Breton Island for the past 50–80 years. A record of a Fisher on Cape Breton Island in February 2002 prompted us to collate and analyze other records of Cape Breton Island sightings of the species from that date to May 2021. Based on reported sightings, we conclude that Fisher has extended its range from mainland Nova Scotia, apparently crossing the Strait of Canso, and that a breeding population now exists on Cape Breton Island and is expanding. We also comment on possible negative interactions between this expanding Fisher population and the provincially Endangered American Marten (Martes americana) population on the island
Salmon Shark (Lamna ditropis) scratching behaviour using floating anthropogenic debris
Full text linkObservations of animal behaviour in the open ocean are relatively rare. However, while conducting surveys in the Northeast Pacific in the summers of 2019 and 2021, we encountered two Salmon Shark (Lamna ditropis) using floating anthropogenic debris to scratch their bodies. We captured the activity with aerial (drone) and underwater cameras. We document and describe this novel behaviour as high energy, high impact, repetitive, fast, and long lasting (e.g., every ~15 s for >20 minutes). We explore these observations in light of traditional ecological knowledge and scientific literature
"Why Sharks Matter: a Deep Dive with the World’s Most Misunderstood Predator" by David Shiffman, 2022 [book review]
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"The Alpha Female Wolf: the Fierce Legacy of Yellowstone’s 06" by Rick McIntyre, 2022 [book review]
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Hiding in plain sight: combining field-naturalist observations and herbarium records to reveal phenological change
Full text linkAs the climate warms, northern ecosystems are experiencing warmer winters and seasonal climatic shifts. Vascular plants are expected to respond to climate change by adjusting flowering or seeding periods. To determine how a native mixed-wood boreal floral assemblage has responded to warming temperatures over the 20th century, we collated historical observations made by field-naturalists as well as voucher data from the Thunder Bay region of Ontario, Canada. Combining these datasets, we performed regression analyses on 11 species of spring-flowering vascular plants to evaluate temporal trends and used spring cumulative growing degree day (sGDD0) to determine the influence of climate on flowering times. Four species showed consistent positive temporal trends (i.e., flowered later with time), while four species (three of which also demonstrated temporal trends) showed negative trends with sGDD0 (i.e., flowered earlier with an increased number of degree days above 0°C). The unexpected observation of later flowering times but predicted observation of earlier blooming with increased sGDD0 indicates that the inclusion of climate metrics may be necessary to determine the response of native vascular plants to the onset of changes in their environment. These observations were not statistically significant when field-naturalist or herbarium voucher data were analyzed separately, possibly due to low statistical power. Combining data from both sources, however, revealed common responses to climate warming among species within an ecoregion
Introduced earthworms (Lumbricidae) in restored and remnant tallgrass prairies of southern Ontario
Full text linkIntroduced earthworms alter the trajectory and composition of plant communities, for example, through their feeding, burrowing behaviour, and interactions with seeds. High densities of several earthworm species may decrease native biodiversity and disrupt restoration efforts in tallgrass prairies. This affects efforts to conserve and restore such habitat, which is of high conservation and restoration priority in eastern North America and typically restored through seeding events. To date, Lumbricus terrestris (Lumbricidae) and other species have remained largely undocumented in tallgrass prairies. We surveyed 22 tallgrass prairie sites in southern Ontario, Canada, to document earthworm density and species. Lumbricus terrestris was found at all sites. The average density was 66 ± 91 (SD) earthworms/m2 across our sampling plots, mostly juveniles (~94%). The number of all earthworms per plot significantly increased with the number of earthworm middens in each plot (χ21 = 4.50, P = 0.034). Prairies with a large number of middens had high earthworm density, but middens alone appear to explain little variation in our data (linear mixed-effects model, marginal R2 = 0.12) meaning there are other biologically important factors that affect their density. However, we found no effects of soil pH, organic matter content, or texture on the number earthworms per plot suggesting that earthworms can invade a range of tallgrass prairie soils with pH values between 5.27 and 7.67
Status and declining trend of Sparrow’s-egg Lady’s-slipper (Cypripedium passerinum) orchids in Pukaskwa National Park, Ontario, Canada
Full text linkPukaskwa National Park hosts part of a disjunct population of the perennial orchid species Sparrow’s-egg Lady’s-slipper (Cypripedium passerinum) on the north shore of Lake Superior, Ontario, Canada. Monitoring of C. passerinum within Pukaskwa National Park occurred between 1979 and 2019. During that period, the total number of stalks and the number of C. passerinum colonies within the park have declined, while the proportion of flowering stalks at colonies has increased. Although the number of stalks at extant colonies is stable, this population may be suffering from lack of recruitment and is at risk of extirpation. We hypothesize that the decline and lack of recruitment are a result of changing habitat conditions due to natural and anthropogenic influence
