Local climate determines vulnerability to camouflage mismatch in snowshoe hares

Aim: Phenological mismatches, when life-events become mistimed
with optimal en- vironmental conditions, have become increasingly common
under climate change. Population-level susceptibility to mismatches
depends on how phenology and pheno- typic plasticity vary across a
species’ distributional range. Here, we quantify the envi- ronmental
drivers of colour moult phenology, phenotypic plasticity, and the extent
of phenological mismatch in seasonal camouflage to assess vulnerability to
mismatch in a common North American mammal. Location: North
America. Time period: 2010–2017. Major taxa
studied: Snowshoe hare (Lepus americanus). Methods: We
used > 5,500 by-catch photographs of snowshoe hares from 448 re-
mote camera trap sites at three independent study areas. To quantify moult
phenol- ogy and phenotypic plasticity, we used multinomial logistic
regression models that incorporated geospatial and high-resolution climate
data. We estimated occurrence of camouflage mismatch between hares’ coat
colour and the presence and absence of snow over 7 years of monitoring.
Results: Spatial and temporal variation in moult phenology
depended on local climate conditions more so than on latitude. First,
hares in colder, snowier areas moulted earlier in the fall and later in
the spring. Next, hares exhibited phenotypic plasticity in moult phenology
in response to annual variation in temperature and snow dura- tion,
especially in the spring. Finally, the occurrence of camouflage mismatch
varied in space and time; white hares on dark, snowless background
occurred primarily during low-snow years in regions characterized by
shallow, short-lasting snowpack. Main conclusions: Long-term
climate and annual variation in snow and temperature determine coat colour
moult phenology in snowshoe hares. In most areas, climate change leads to
shorter snow seasons, but the occurrence of camouflage mismatch varies
across the species’ range. Our results underscore the population-specific
sus- ceptibility to climate change-induced stressors and the necessity to
understand this variation to prioritize the populations most vulnerable
under global environmental change.