(gentle music)
(grandiose music)
- [Narrator] Spinner dolphins.
In the Pacific off the coast of Costa Rica
in Central America, they're starting to gather
in great numbers.
Spinners live in pods, groups of individuals
linked by complex social relationships.
(dolphins squeaking)
The dolphins constantly touch and talk with one another
using a language of clicks and whistles.
(dolphins squeaking)
They're shadowed by yellowfin tuna.
The tuna rely on the dolphins to find food.
Everyone is searching for the same prey.
Lanternfish, the most numerous fish on the planet.
(grandiose orchestral music)
No longer than your finger, lanternfish spend
most of their time hiding in the deep.
So despite their astounding abundance,
we don't fish for them.
They are one of the few fish that still thrives.
As they close in on their prey, the dolphin pod
gets bigger and bigger.
(grandiose orchestral music)
This pod could be 10,000 strong.
(grandiose orchestral music)
For every one at the surface, 20 swim below.
(grandiose orchestral music)
Using echolocation, a type of sonar,
the dolphins detect lanternfish in the depths
and drive them to the surface.
(dolphins squeaking)
They patrol the underside of the show
to stop their prey escaping back to the deep.
(dolphins squeaking) (gentle orchestral music)
Once the dolphins have had their fill,
there's still plenty more for other predators.
Because we don't fish for them,
lanternfish and their predators thrive.
(grandiose music)
(dolphins squeaking)