What drives Yellowstone’s massive elk migrations?

Source: Science Daily

Yellowstone’s migratory elk rely primarily on environmental cues, including a retreating snowline and the greening grasses of spring, to decide when to make the treks between their winter ranges and summer ranges, researchers show. Their study combined GPS tracking data from more than 400 animals in nine major Yellowstone elk populations with satellite imagery to create a comprehensive model of what drives these animals to move.

https://www.sciencedaily.com/releases/2019/06/190614141246.htm