Are blue whales nocturnal or diurnal?

Blue whales are neither strictly nocturnal nor diurnal. They are crepuscular, which means they are most active during twilight hours - at dawn and dusk.

Here's why:

* Food Availability: Blue whales feed primarily on krill, which are tiny crustaceans. Krill are more concentrated at the surface during twilight hours, making it easier for the whales to feed.

* Temperature Regulation: Blue whales are large animals and can overheat in direct sunlight. They may be more active during cooler twilight hours to help regulate their body temperature.

* Predator Avoidance: While blue whales have few natural predators, they might be more vulnerable to attacks from orcas during daylight hours.

Therefore, while blue whales can be active at any time of day, they tend to be most active at dawn and dusk, making them crepuscular.