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Research article2023Peer reviewedOpen access

Increased summer temperature is associated with reduced calf mass of a circumpolar large mammal through direct thermoregulatory and indirect, food quality, pathways

Holmes, Sheila M.; Dressel, Sabrina; Morel, Julien; Spitzer, Robert; Ball, John P.; Ericsson, Goran; Singh, Navinder J.; Widemo, Fredrik; Cromsigt, Joris P. G. M.; Danell, Kjell


Climate change represents a growing ecological challenge. The (sub) arctic and boreal regions of the world experience the most rapid warming, presenting an excellent model system for studying how climate change afects mammals. Moose (Alces alces) are a particularly relevant model species with their circumpolar range. Population declines across the southern edge of this range are linked to rising temperatures. Using a long-term dataset (1988–1997, 2017–2019), we examine the relative strength of direct (thermoregulatory costs) and indirect (food quality) pathways linking temperature, precipitation, and the quality of two important food items (birch and freweed) to variation in moose calf mass in northern Sweden. The direct efects of temperature consistently showed stronger relationships to moose calf mass than did the indirect efects. The proportion of growing season days where the temperature exceeded a 20 °C threshold showed stronger direct negative relationships to moose calf mass than did mean temperature values. Finally, while annual forb (freweed) quality was more strongly infuenced by temperature and precipitation than were perennial (birch) leaves, this did not translate into a stronger relationship to moose calf weight. The only indirect path with supporting evidence suggested that mean growing season temperatures were positively associated with neutral detergent fber, which was, in turn, negatively associated with calf mass. While indirect impacts of climate change deserve further investigation, it is important to recognize the large direct impacts of temperature on cold-adapted species.


Alces alces; Climate change impacts on mammals; Direct effects; Indirect effects; Sweden

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