As the seas warm, marine mammals may struggle to survive the heat or become malnourished because their prey has left for more hospitable waters; both situations can leave the mammals with weakened immune systems.
A growing number of studies show that warming temperatures are increasing mortality. Researchers warn that heat stress could become a major factor in future extinctions.
Warm, wet weather triggered the unprecedented die-off of imperiled saiga antelope, scientists say. And climate change may make such conditions even more likely.