Thread by @FateOfCaribou

Each spring, #caribou migrate from their winter habitat to calving grounds. We analyzed GPS collars from 1000+ caribou and found that herds across the #Arctic are synched up and all depart on this migration around the same time 🤯 1/5

The timing of spring migration departure is related to large-scale, ocean-driven climate indices. In other words, continental-scale patterns in temp and weather trigger caribou to head north at the same time. 2/5

BUT, even if they leave at the same time, not all herds arrive on their calving grounds at the same time. The speed of migration is highly variable, and later departure dates ≠ later arrival. Are some caribou just more punctual than others? 3/5

Turns out that weather conditions from the ✨previous summer✨ determine how fast caribou migrate. Cool summers ➡ fewer biting insects ➡ better body condition ➡ faster migration. 4/5
Pic: caribou trying to avoid insects; Kyle Joly, NPS

For a deep-dive on spring migration synchrony and climate/weather, check out our #OpenSource 2019 paper “Tactical departures and strategic arrivals: Divergent effects of climate and weather on caribou spring migrations” 5/5
esajournals.onlinelibrary.wiley.com/doi/10.1002/ec…