Climate Trivia: Size and Temperature

Shifts in temperature related to climate change cause species to shift their favored territories, the seasonal timing of their activities and physiological traits including body size. As a given location becomes warmer, a population of warm-blooded animals such as mammals become:

a)    bigger over successive generations.
b)    smaller over successive generations.

The correct answer is b. Bergmann’s rule states that closely related populations of warm-blooded animals (birds and mammals) have members with larger body sizes in cooler climates and smaller body sizes in warmer climates. This difference arises largely from the ability of smaller animals to dissipate heat more quickly and possibly from climatic differences in food availability. Excavations of an ancient tropical environment now located beneath present day Wyoming show that during a period of rapid warming ? the Paleocene-Eocene Thermal Maximum around 56 million years ago ? an early species of horse became on average 30 percent smaller over the course of about 130,000 years. This shrinking occurred as the average global temperature warmed by as much as 16 degrees Fahrenheit.

Seasons: Winter, Spring, Summer, Fall

Source: Secord, R et al. “Evolution of the Earliest Horses Driven by Climate Change in the Paleocene-Eocene Thermal Maximum.” Science 335 (2012): 959-962.

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