Big Pacific – Voracious Pacific

Watch the third episode of Big Pacific, “Voracious Pacific,” on your local PBS station at 8pm Eastern, Wednesday, July 5th. The companion book is available now from Princeton University Press.

The inhabitants of the Pacific Ocean are united by the need to feed, the constant quest for sustenance. Many of these inhabitants feed on each other—only a handful of the largest and most dangerous are free of the threat of becoming somebody else’s lunch. Any evolutionary adaptation that makes it easier to acquire food confers an advantage in the battle for survival, and the Pacific showcases many remarkable adaptations and specializations.

Double-crested cormorant

A double-crested cormorant dries its wings after a dive.

The double-crested cormorant dives for fish, plummeting out of the air to plunge into shallow coastal waters. The light, hollow bones that make it easy for other birds to soar would make it difficult for the cormorant to remain submerged; instead it has evolved with heavier bones, lower body fat, and feathers that absorb water, allowing it to swim underwater for up to thirty seconds at a time, propelled by its wings and webbed feet. After a dive, the now waterlogged bird will need to dry its feathers before it can fly again, and they can be easily spotted on rocky shores, standing with wings outstretched to dry in the sun. These cormorants are so well adapted to hunting underwater that their young will sometimes take to the water even before learning to fly.

Peppered moray eel

A peppered moray eel slithers across the rocks in search of crabs

If the Pacific is home to birds that hunt underwater, it is only fitting that there should also be fish that hunt on land. Moray eels have long been known as effective predators, possessed of powerful jaws from which few victims escape. Morays typically lurk in crevices or holes in underwater reefs, waiting for an unsuspecting meal to swim by, but the peppered moray takes a more proactive approach. These eels will slither out of the water at low tide, dipping in and out of rock pools to avoid suffocation, searching for crabs. The peppered moray is the only member of the moray family known to leave the water in this way.

Nomura's jellyfish

Nomura’s jellyfish is one of the largest jellyfish, but feeds though hundreds of tiny mouths.

Paradoxically, some of the largest denizens of the ocean feed on the smallest prey. The blue whale is the largest animal on the planet – a full-grown blue whale can reach a hundred feet in length and two hundred tonnes in weight—but it feeds on krill, small crustaceans barely an inch in length, filtering vast draughts of water through baleen plates in its mouth to trap the tiny krill. Manta rays feed on smaller fry still, sweeping up plankton as they glide through the water on wing-like fins that can span 23 feet in width. But perhaps the most extraordinary is the Nomura’s jellyfish. These giant jellyfish start life as a polyp the size of a pinhead with a mouth barely a millimeter wide but in the space of a year they grow to some six feet in diameter and more than 400 pounds in weight. Their mouths do not grow with them; instead the jellyfish develops hundreds of tiny mouths, allowing them to filter an Olympic swimming pool of water for plankton every day. Voracious indeed!

See dazzling footage of these animals and many more in the next episode of Big Pacific.