Why are whale sharks not whales?

Despite having the word "whale" in their name, whale sharks are not whales but the largest known living fish species. They are members of the class Chondrichthyes, which encompasses cartilaginous fish, and are more closely related to sharks and rays than to whales.

Whales are mammals and share several distinct characteristics with other mammals, including having lungs for breathing, giving birth to live young, producing milk to nurse their offspring, and being warm-blooded. In contrast, whale sharks are cold-blooded animals that breathe through gills, lay eggs, and do not produce milk.

Here are some key differences between whale sharks and whales:

1. Body Structure: Whales have a streamlined body with a dorsal fin, whereas whale sharks have a broad and flat body with two dorsal fins.

2. Breathing: Whales surface to breathe air through blowholes, while whale sharks breathe through gills located on the sides of their heads.

3. Reproduction: Whales give birth to live young and produce milk to feed them. Whale sharks reproduce by laying eggs, with females producing large numbers of small eggs.

4. Body Temperature: Whales are warm-blooded animals, meaning they can maintain a constant body temperature regardless of the surrounding environment. Whale sharks are cold-blooded, influenced by the temperature of the water they inhabit.

5. Diet: Whales are largely carnivores, feeding on prey such as krill, fish, squid, and even other marine mammals. Whale sharks are filter-feeders and primarily feed on plankton and small fish.

6. Migration: Many whale species undertake extensive migrations, moving between feeding and breeding grounds. Whale sharks also exhibit migratory patterns, but they tend to be less well-defined compared to those of whales.

Overall, while whale sharks may be similar in size to some whales, they belong to a different group of animals and exhibit unique characteristics that distinguish them from true whales.