At the tip of Cape Cod, a sandy spit reaches out into the Atlantic, like an arm, towards a vast underwater plateau where humpbacks gather each summer to feed. This is the US marine sanctuary of Stellwagen Bank, where for the past three weeks I’ve been a guest on the Dolphin Fleet whalewatch boats, working out of Provincetown.

I’ve been coming here for 18 years; it’s where I learned about whales. I’m inordinately fond of these animals and like me, they come back here too.

Every spring, the whales return from their mating grounds in the Caribbean where they’ve spent the winter, fasting: those clear blue waters hold no sustenance for a whale. The grey-green seas of the Cape are filled with food: the cycle of upwelling nutrition feeds phytoplankton, that feed zooplankton, that feed the sand-eels, that feed the whales. They’re unconcerned by the clouds of gulls that follow them, in the same cycle, after the same food – even stealing fish out of the whales’ mouths.

Like other rorqual whales, humpbacks’ throats expand in rubbery pleats reaching down to their navels. Opening their mouths wide, they strain their food using the strips of baleen – made of keratin, the same substance found in human fingernails – that hang from their upper jaws. Humpbacks co-operate in one of the most spectacular sights in the natural world. Blowing precisely calibrated streams of bubbles from their mouths, they swim round in circles, creating curtains of air around their prey. Then they rise, open-mouthed like giant crows. As they do so, they seem to alter the shape of the water itself.

This whale is thwacking its tail up and down in behaviour known as lob-tailing. But only the humpbacks of Stellwagen Bank use another technique, ‘kick-feeding’, to stun their prey. It’s learned, local culture.

This may be the most closely studied population of great whales in the world. The Provincetown Center for Coastal Studies (PCCS) was founded in 1976 to observe and document these animals. At that time, whaling was still widely practised. A veteran captain of the Dolphin Fleet told me that back in the 1960s, one Provincetown diner used to serve humpback steaks.

With the advent of the Dolphin Fleet whalewatch, founded in 1975 by the Avellar family (Portuguese in descent, like many of the fishing community in Provincetown), commerce was allied with science. With naturalists on the boats, PCCS was able to gather an immense database, sustained by tourist dollars. The result is a catalogue of 2,000 individual whales. One of the first to be named, Salt, has had 14 calves, and is now a great-grandmother.

Calves stay with females for their first year, feeding on milk which is 60% fat. One intrepid researcher who sampled it said it tasted like fishy cottage cheese. Females can bear a calf every two to three years, and remain fertile all their lives. They may reach 100 years in age.

Humpbacks have unique black and white patterns on the underside of their flukes, enabling the identification of individual animals. Each receives non-gender-specific names; not because Provincetown is a gender-fluid town – which it certainly is – but because it is difficult to sex a whale.

This whale is an exception. She’s displaying her genital mound, which is usually impossible to see.

Some whales are truly striking. This speckled female has been called Ventisca –Spanish for “snowstorm”. She’s one of the first whales I ever saw, back in 2000. She’s a popular performer, partial to rolling on her back. Humpbacks show no fear of the whalewatch boats. These whales may also be among the most habituated to humans. Sometimes on the boat we joke that we’re providing a ‘human watch’ for whales. As to what they really make of us, we may never know.

Dennis Minsky, veteran naturalist on the Dolphin Fleet, has a wild theory. “Every day I announce a whale’s name over the tannoy system,” he says. “If my dog Dory recognises her name, what’s to say these whales don’t?”

This whale rose perpendicularly through the water to peer at us. It’s called “spy-hopping”; to me it looks like curiosity. Fascinated by whale-human culture, Minksy has compiled a “whalewatch glossary” of terms used by the captains. A breaching whale is a “Hail Mary”. Irritating leisure craft are generically “plastic”. It’s a sort of update on Moby-Dick. With more swear words.

Other interactions on Stellwagen Bank are more dangerous. Some 55% of its humpbacks get entangled in fishing gear or are struck by ships. This whale has had a serious encounter with a propeller, leaving it with a serrated ridge of scars. The North Atlantic right whale, which also shares these waters, suffers seriously from anthropogenic threats. In the past year, 19 right whales have died in this way. With only 450 of the species left, Dr Charles “Stormy” Mayo, one of the founders of PCCS, has started using the E word: “Extinction – possibly by 2050.”

Fin whales – the next biggest animals on Earth after blue whales – also scythe through these waters. Vast and enigmatic, nicknamed the greyhounds of the sea, they can reach 24 knots, as fast as our boat. They have uniquely asymmetrical markings – pale on one side of their bodies, dark on the other. They use the white side to scare fish with a sudden flash – then gulp down their prey. A pair of lunge-feeding fin whales once lurched so close to our prow that our captain, Todd Motta, shouted, “Whoa!”, But far from colliding with us, they seemed to be using our boat as a fish-stop.

On calm days, this ocean becomes hypnotic. Below its silvery surface - which Herman Melville called “the ocean’s skin” - white-sided dolphin surfed into view, leaping and foraging around the whales. They’re beautifully marked, with grey and mustard stripes that seem to streamline their bodies. One came close to the boat, visible through that watery skin like a super-realist art work by Gerhard Richter.

Of all great whales, humpbacks are most prone to breaching. No one knows why. Are they trying to dislodge troublesome parasites or communicating with other whales? Anyone who sees a 15-metre whale launch itself out of the ocean is sure of one thing: it looks like fun. Melville observed of the humpback: “He is the most gamesome and light-hearted of all the whales, making more gay foam and white water generally than any other of them.” As this calf leapt, it looked close to landing on a dolphin. Hanging there in the air, a humpback demonstrates its kinship with us. No whale so well deserves its binomial: Megaptera novaeangliae – “big-winged New Englander”, a barnacled angel.

John Berger wrote of the ‘”narrow abyss of non-comprehension” between ourselves and other animals. That abyss is implicit out here, in the open ocean. Given what we have inflicted on these animals, and given the future threats they face, this protected zone seems like a modern Eden. Surrounded by jumping, feeding humpbacks, circled by minke and fin whales, with white-sided dolphins weaving in between, it seemed to me that merely bearing witness to this wonder was enough. They were in their moment, and so were we.

• With grateful thanks to the Dolphin Fleet, its crew and its naturalists.

Philip Hoare’s RisingTideFallingStar (4th Estate) is published this month in paperback.

