The gut microbiome of wild American marten in the Upper Peninsula of Michigan

Carnivores are ecologically important and sensitive to habitat loss and anthropogenic disruption. Here we measured trophic level and gut bacterial composition as proxies of carnivore ecological status across the Upper Peninsula, Michigan, for wild American marten (Martes americana; hereafter marten). In contrast to studies that have focused on omnivorous and herbivorous species, we find that marten, like other carnivore species without a cecum, are dominated by Firmicutes (52.35%) and Proteobacteria (45.31%) but lack Bacteroidetes. Additionally, a majority of the 12 major bacterial genera (occurring at ≥1%) are known hydrogen producers, suggesting these taxa may contribute to host energy requirements through fermentative production of acetate. Our study suggests that live trapping and harvest methods yield similar marten gut microbiome data. In addition, preserving undisturbed forest likely impacts marten ecology by measurably increasing marten trophic level and altering the gut microbiome. Our study underscores the utility of the gut microbiome as a tool to monitor the ecological status of wild carnivore populations.

Changes in dental wear and breakage in arctic foxes across space and time: Evidence for anthropogenic food subsidies?

Increased human presence in the Arctic may affect its vulnerable ecosystems. Effects on arctic and red foxes provide notable examples. Both have been documented to take anthropogenic subsidies when available, which can change diet and ranging patterns in complex ways that can either benefit or harm populations, depending on the situation. Understanding this complexity requires new tools to study impacts of increasing human presence on endemic mammals at high latitudes. We propose that dental ecology, specifically tooth wear and breakage, can offer important clues. Based on samples of arctic foxes (Vulpes lagopus Linnaeus, 1758) trapped prior to (n = 78) and following (n = 57) rapidly growing human presence on the Yamal Peninsula, Russia, we found that foxes trapped recently in proximity to human settlement had significantly less tooth wear and breakage. This is likely explained by a dietary shift from consumption of reindeer carcasses (Rangifer tarandus Linnaeus, 1758) including bone to softer human-derived foods, especially when preferred smaller prey (e.g., West Siberian lemmings, Lemmus sibiricus Kerr, 1792 and arctic lemmings, Dicrostonyx torquatus Pallas, 1778) are unavailable. These results suggest that tooth wear can be a useful indicator of the consumption of anthropogenic foods in arctic foxes.

Sugar addicted in the city: impact of urbanisation on food choice and diet composition of the Eurasian red squirrel (Sciurus vulgaris)

Urban wildlife faces a great variety of human-induced habitat alterations, among others changes in resource availability and composition, often resulting in serious declines in biodiversity. Nevertheless, Eurasian red squirrels (Sciurus vulgaris) occur in high densities in urban areas and seem to benefit from supplementary feeding. However, we still lack knowledge about consequences of urbanisation on mammalian foraging behaviour and nutrient intake. Thus, we investigated body mass, food choice and diet composition in squirrels from an urban core area versus a forest population in a cafeteria experiment. Urban individuals were lower in initial body mass and condition, but consumed significantly more g and kJ per day and significantly gained weight over the course of the experiment (around 2 weeks); nevertheless, the difference in body mass and condition persisted. All squirrels preferred hazelnuts, but urban squirrels had a wider dietary range and consumed more non-natural food items. Both groups prioritised fat and there was no difference in protein intake. Urban squirrels though had a significantly higher sugar intake, mainly by eating biscuits. Our results demonstrate clear effects of urbanisation on foraging behaviour and preferences, which has the potential for nutritional mismatch or negative side effects due to consumption of non-natural food items. Our findings show that highly supplemented urban core fragments might not serve as adequate refuge for wildlife.