Arctic ungulates are experiencing the most rapid climate warming on Earth. While
concerns have been raised that more frequent icing events may cause die-offs, and
earlier springs may generate a trophic mismatch in phenology, the effects of warming
autumns have been largely neglected. We used 25 years of individual-based data from
a growing population of wild Svalbard reindeer, to test how warmer autumns enhance
population growth. Delayed plant senescence had no effect, but a six-week delay in
snow-onset (the observed data range) was estimated to increase late winter body
mass by 10%. Because average late winter body mass explains 90% of the variation
in population growth rates, such a delay in winter-onset would enable a population
growth of r = 0.20, sufficient to counteract all but the most extreme icing events. This
study provides novel mechanistic insights into the consequences of climate change
for Arctic herbivores, highlighting the positive impact of warming autumns on population
viability, offsetting the impacts of harsher winters. Thus, the future for Arctic
herbivores facing climate change may be brighter than the prevailing view.
body mass, climate change, fitness, GPS, movement ecology, plant phenology, Rangifer, snow,
space use, ungulates
