Why are gray wolves smaller near the southern end of their range?

Gray wolves are smaller near the southern end of their range due to an evolutionary principle known as Bergmann’s rule.

This biological principle states that within a wide-ranging species of warm-blooded animals, individuals in colder regions tend to be larger and bulkier than those in warmer regions. This size variation serves as an adaptive mechanism: larger bodies have a smaller surface-area-to-weight ratio, which helps conserve body heat in cold climates. Conversely, wolves in warmer southern regions, such as the Middle East, Arabia, and India, are smaller, as their physiology is better suited to radiate heat in those environments.1234