Do animals know their time is running out?
As the Arctic ice rapidly melts owing to climate change, two seemingly dissimilar apex predators are being forced to adapt their diets and behaviours faster than these cold-climate mammals can cope.
Polar bears and narwhals are using up to four times as much energy to survive because of major ice loss in the Arctic, find scientists. Even though the Arctic was once the perfect habitat, the shrinking and unique adaptations are becoming less suitable to them.
But these iconic polar species now face an uncertain future as global warming causes catastrophic sea ice loss, driving polar bears onto land and narwhals to swim for their lives to avoid the killer whales that now have access to previously ice-locked stretches of ocean, finds the study published in the Journal of Experimental Biology.
Both species have been forced to alter their behaviours in fundamental ways that increase the amount of energy they burn by as much as 400% — a rate few species could sustain. The mammals are physiologically designed to use as little energy as possible. Polar bears are primarily “sit and wait” hunters, adapted to catching seals by breathing holes, and narwhals have evolved to dive very deep for prey without making fast movements, reports The Guardian.
“The Arctic world is so much more unpredictable for these animals now,” said Dr Terrie Williams, a co-author of the report from the department of ecology and evolutionary biology at the University of California, Santa Cruz told The Guardian. “With a finite amount of oxygen in their muscles and blood, we find that the narwhals budget their speed, depth, and duration of dives to match the capacity of their internal scuba tanks. One miscalculation could result in drowning.”
“Polar bears on land without access to marine mammal prey are at an increased risk of starvation,” the study authors wrote.
“The high costs of diving for narwhals, coupled with the loss of reliable breathing holes upon which they depend, due to unpredictable sea ice shifts, have led to the mammals becoming trapped beneath the ice,” the study authors wrote.
The loss of sea ice also disrupts the timing of narwhal migration, exposing their young to increased predation from killer whales.
The scientists also warn that the decline of both apex predators will “lead to rapid changes in the Arctic marine ecosystem.”