Extensive dinosaur faunas inhabited Arctic regions well beyond the polar circle. We know that northern regions were warmer during the Mesozoic than they are now, and clearly they were warm enough for dinosaurs

Question

But Arctic winters would have had long periods of dim light (twilight) in the Mesozoic, as they do now. How might dinosaurs have responded to the seasonal changes in day length in the Arctic?

Answer 1

Two issues must be considered: being able to see in dim light and finding food during a period of many weeks when primary production by plants was low.
• Some of the Arctic dinosaurs had large eyes—Troodon, a theropod, is frequently cited as an example. All else being equal, large eyes should enhance vision at low light intensities.
• Trackways suggest that dinosaurs migrated. During most of the Jurassic and throughout the Middle Cretaceous, dinosaurs in western North America (the best-known assemblage) would have been able to move in a north-south direction along the shore of the inland sea that extended across the middle of the continent.
The flip side of low primary production in the Arctic during the dark winters is extraordinarily high primary production during the summers when the days are long. The abundance of food that was available in the Arctic during the summers may have rendered long migrations cost-effective in terms of the annual energy budgets of dinosaurs.
Sources
Buffetaut, E. 2004 . Polar dinosaurs and the question of dinosaur extinction: A brief review. Palaeogeography, Palaeoclimatology, Palaeoecology 214:225-231
Fanti, F., and T. Miyashita. 2009 . A high latitude vertebrate fossil assemblage from the Late Cretaceous of west-central Alberta, Canada: Evidence for dinosaur nesting and vertebrate latitudinal gradient. Palaeogeography, Palaeoclimatology, Palaeoecology 275:37-53