They also eat other small animals like:
* Copepods: Another type of small crustacean.
* Small fish: Like sardines and anchovies.
* Squid: Especially in deeper waters.
Blue whales are filter feeders, meaning they strain food out of the water. They do this by opening their massive mouths and swallowing large quantities of water. Their baleen plates, which are made of keratin (the same material as human hair and nails), act like giant sieves, trapping the krill and other small prey while allowing the water to pass back out.