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Benjamin Larue

Université de Sherbrooke
Spring molt in bighorn sheep: what are the drivers and is there individual plasticity?

Benjamin Larue, Fanie Pelletier and Marco Festa-Bianchet

Fur facilitates thermoregulation and offers protection against harsh climatic condition in mammals. Because it is a non-living keratinous structure, damaged fur can only be replaced through shedding or molt. This process of hair loss and subsequent hair growth can be energetically costly. This is particularly true for spring molt in temperate climates because it occurs after a period of high energetic demand and low resources. Here, we first described the progression of individual spring molt in bighorn sheep using generalized linear mixed models. Random slopes in these models have made it possible to assess individual plasticity and create molt reaction norms based on environmental and life-history gradients. This is particularly interesting because adaptive phenotypic plasticity could mitigate the potential mismatch between molt and environmental conditions caused by global change. Then, we evaluated extrinsic (e.g. environment and density) and intrinsic (e.g. body condition and life-history) factors that potentially drive spring molt in bighorn sheep using path analyses. Path analyses were used to identify of factors that don’t, indirectly or directly affect molt. These analyses allowed the representation of a single molt causal network which included the strength of the effects between the different factors.