Big and brilliant: complex whale behavior tied to brain size


FILE PHOTO: The fluke of a sperm whale sticks out of the sea as it dives among other resting whales off the coast of Mirissa, in southern Sri Lanka on March 29, 2013. REUTERS/David Loh
FILE
PHOTO: The fluke of a sperm whale sticks out of the sea as it
dives among other resting whales off the coast of
Mirissa

Thomson
Reuters


By Will Dunham

WASHINGTON (Reuters) – Cetaceans — whales and dolphins — are
among the brainiest of beings. In terms of sheer brain size, the
sperm whale is tops on Earth, with a brain six times larger than
that of a person.

And now, scientists have identified key differences among
cetaceans linked to brain size. A study of 90 cetacean species
published on Monday found that those with larger brains exhibit
greater complexity in social structures and behaviors, with
species like the killer whale and sperm whale leading the way.

“Dolphin and whale societies are at least as complex as what we
have observed in primates,” said evolutionary biologist Susanne
Shultz of the University of Manchester in Britain.

“They are extremely playful, they learn from each other,have
complex communication. One problem for understanding justhow
smart they are is how difficult it is to observe them and to
understand their marine world. Therefore, we have only a glimpse
of what they are capable of.”The researchers created a
comprehensive database of brain size, social structures and
cultural behaviors across cetacean species. The group of species
with the largest brain size relative to body size was the large
whale-like dolphins such as the killer whale, the similar-looking
false killer whale and the pilot whale, Shultz said.

“Killer whales have cultural food preferences, have matriarchs
that lead and teach other group members, and cooperatively hunt,”
Shultz said.

In terms of intra-species food preferences, certain killerwhale
populations, also known as orcas, prefer salmon whereas others
prefer seals or other whales or sharks depending on their group’s
culture.Other big-brained cetaceans also demonstrate
sophisticated behaviors.

Mother sperm whales organize babysitting duties using other
members of their pod to protect their young while they hunt for
food down deep. The distinctive vocalizations sperm whales use to
communicate sometimes differ depending upon where they live, much
like regional dialects in human language.

Bottlenose dolphins use sea sponges as tools to protect their
beaks while foraging for food, and live in structured
communities.

Some of the largest cetaceans — filter-feeding baleen whales
like the blue whale, fin whale and humpback whale that eat tiny
crustaceans called krill rather than fish or squid — were on the
low end of relative brain size. They live fairly solitary lives,
coming together only for breeding seasons and near rich food
sources.

The research was published in the journal Nature Ecology &
Evolution.

(Reporting by Will Dunham; Editing by Sandra Maler)

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