The sighting was rare: Risso’s dolphins typically travel in groups of only 10 to 30 animals, according to the National Oceanic and Atmospheric Administration.

[…]

The large mix of adult and juvenile dolphins was likely the result of several pods coming together and swimming south, she said.

Although this is not the first time they have seen this large of a group, it is not a common occurrence, Talty said.

For those curious about why such a large group.