Such close encounters are a common hazard, according to Ramiro, our naturalist guide, although the birds have excellent eyesight, and nobody actually gets hit. Anne is now shadowing a ray, a very big ray, no harm done. Just a couple of minutes later we watch a marine iguana swimming in the sea alongside us, gnawing algae off the black basalt.

When we land on Espanola that morning, a sea lion that had given birth moments before is moving her still-blind pup away from the jetty's footpath, lifting the mewling ball of fur gently in her mouth. That same night after dinner, while the ship swings at anchor, we watch flying fish exploding from the sea and thudding against the side of our vessel, attracted by the lights, while sea lions hover just a couple of metres away, waiting to scoop up the stunned fish.

A journey to the Galapagos Islands is a voyage to another planet. Even for the well-travelled adventurer, the astonishing animal, plant and bird life of these remote volcanic islands rekindles all the excitement of the first-time traveller. It's nature as you've never seen her before, birth, death and everything in between, flaunting her wildest notions with species that seem to come from science fiction. The marine iguana for starters, is a creature that looks like a leftover from the age of the dinosaurs. Then there's the Galapagos tortoise, which can weigh up to 300 kilos, happily munching the fruit of the poison apple, which will blister your skin if so much as a drop should fall on you, and can live – well nobody quite knows for sure, but 150 years is well within reach.

What's more, it all happens right before your nose. Apart from the lumbering giant tortoises, the islands' wildlife has never been hunted. There are no large predators here, and the birds and animals are practically fearless. At the waterfront on San Cristobal, shortly after our flight to the island, fat sea lions are sprawled across the steps of the jetty where we wait to board the Zodiac waiting to take us to our ship. V-tailed frigate birds, also known as pirate birds for their habit of robbing other birds of their catch, drift across the sky. As you march around the islands' paths, pairs of Nazca boobies will continue their squabbling domestic arguments, albatross will barely pause from their mating dance and a blue-footed booby lands just a couple of metres away as I stand on a clifftop. At the Tortoise Reserve on San Cristobal, giant tortoises will munch their way through vegetation, unconcerned by the telephoto lenses focused on them. Go out for a snorkel and sea lions perform aquabatics in front of your nose, while their pups will nuzzle against your laces if they find your footwear sufficiently attractive – and neon blue seems to be their fashion favourite.

It's these animals that rule the roost. While sea lions and land iguanas might sprawl casually across the pathways, and even give birth on them, it's you who must tread carefully, walk around and get out of the way when they march towards the sea – a zoo in reverse, and a photographers' paradise.

The Galapagos also occupy an exalted place in the annals of science. Frequently described as mother nature's test tube, these islands once changed the way humanity thinks about its origins. Scattered across the Pacific almost 1000 kilometres off the coast of South America, the Galapagos Archipelago consists of 18 main islands and more than 100 islets. Although they might be close, they're all different. The islands sit above one of the planet's most active volcanic hotspots, where the earth's crust is melting, creating undersea volcanoes that rise to the surface to form the islands. As tectonic plates shift, the islands move away from the hotspot, allowing new islands to be created, and this accounts for the vast differences in age, terrain and vegetation among the islands. While Espanola is probably four million years old, Isabela and Fernandina are still being formed. Isabela's active volcanoes rise to 1700 metres, while plantations of coffee, sugarcane, bananas and citrus divide the lush highlands of Santa Cruz.

It is also the differences between the islands that has created the differences in the species that inhabit them. Espanola's marine iguanas are the only members of the species that change colour during breeding season. The land iguanas that inhabit the slopes of Wolf Volcano on Isabela Island are pink, unlike any others. The mockingbirds on Espanola are carnivorous, distinguishing them from those on the other islands. The giant tortoises that live on islands with more abundant vegetation have a rounded, domed carapace,  and then there are the finches, the beaks of each subspecies adapted to a slightly different purpose, depending on the island where they are found. It is almost as if in the Galapagos, nature is underlining the principle of natural selection, highlighting it in red with bold capitals, waiting for a curious mind to come along and draw the obvious conclusion. When the naturalist Charles Darwin arrived in 1835, it was the Galapagos that provided the spark for what would become Darwin's theory of natural selection, the basis for our understanding of evolution.

There are two ways to experience this animal wonderland, either aboard one of the many vessels that offer cruises around the islands or from a base on dry land. Land has lots of appeal, and it's less expensive, but also limiting. The main tourism base is Puerto Ayora on Santa Cruz, site of the Galapagos' main airport, and home to most of its accommodation. Most of the other islands are national parks, with only day visitors and no accommodation. Those who choose to stay in a resort or guesthouse around Puerto Ayora face long boat trips out to the national park islands to see the wildlife. This involves a two-hour trip each way, even to the closest islands.

For anyone who wants to experience the best that the Galapagos has to offer, a cruise is the way to go. It is only by visiting several islands that you will ever get to experience the abundance that nature has installed here. There are many vessels that offer trips around the islands, from deluxe vessels such as the Pinta, with floor-to-ceiling windows in every cabin, air conditioning, fine food and expert naturalists on board, to more basic operations at a pared-down price. Itineraries start at around three nights, but more time is necessary if you want to visit more than just a couple of the islands. Dedicated wildlife watchers and photographers will often spend 10 nights on board, which is enough time to explore the eastern as well as the western isles.

A vessel also gives you more opportunity to explore below the waves, and this is every bit as impressive as what lies above. As it sweeps along the west coast of South America and brushes past the Galapagos, the Humboldt Current brings with it a rich feast of micro-organisms, fostering an explosion of marine life. It is for this reason that the Galapagos is so rich in sea birds and sea lions, and so lavishly endowed with underwater life. Strap on a face mask and snorkel and there's every chance you'll swim with rays, barracuda, turtles, reef sharks and tropical fish. The Galapagos are one of the best places to dive with hammerhead sharks, part of the so-called hammerhead triangle of the Pacific.

A typical day on board will involve a couple of shore excursions in the company of a naturalist, with meals in between, and quite likely time for snorkelling or diving. Naturalists will often give a lecture at some stage during the day, offering insights and background on the islands' history, geology and biology. During the night the vessel will usually pull its anchor and motor off to another location. Every morning you wake to a fresh vision of island and sea waiting to be explored, and fresh revelations. For once in my life I begin every morning feeling like David Attenborough, and every bit as wide-eyed and breathless.

Other places to experience amazing animal life

Madagascar

Another living laboratory where nature has experimented, isolated from the rest of the world for over 60 million years, Madagascar's forests are home to a vast array of endemic animals. The pin-ups of Malagasy wildlife are the furry, round-eyed lemurs, now confined to just a few places and threatened by human encroachment.

Indonesia

Off the coast of Indonesia's West Papua Province, the waters of the Bird's Head Seascape sit at the absolute pinnacle of underwater biodiversity. Unknown to marine biologists until the 1990s, it has blown all previous counts of marine life out of the water. The best base for exploring this pristine underwater wilderness is Misool Eco Resort, which sits on a scimitar of sand a three-hour boat ride from Sorong, in West Papua.

Belize

It might be small, but this slip of a nation tucked into the base of Mexico's Yucatan Peninsula is luxuriantly endowed with tropical forests, mountains, rivers and the biggest reef system in the western hemisphere. Since its human population has remained relatively small, its wildlife flourishes. Situated in the shadows of the Maya Mountains in southern Belize, the Cockscomb Basin Wildlife Sanctuary and Jaguar Preserve is 400 square kilometres of tropical rainforest and the world's only jaguar preserve.

Australia

For the migratory bird species that range as far north as Siberia and south to New Zealand, Lord Howe Island is a biological life raft. Boobies, petrels, terns and ternlets are just some of the species that make this a twitchers' paradise. This is the only place where providence petrels breed and a large concentration of the red-tailed tropic bird can be found along the island's northern cliffs.

Botswana

The delta of the Okavango River is one of Africa's wildlife treasures, a vast freshwater wetland that is flushed by an annual inundation from the Angolan highlands, creating a complete eco-system, from insects to tiny reed frogs, hippos, elephants, leopards and lions. The human population is small, and the delta's wildlife thrives practically unmolested.

TRIP NOTES

MORE INFORMATION

southamericatourism.com

GETTING THERE

LAN Airlines flies daily from Sydney to Santiago, Chile, with onward flights to Quito or Guayaquil, from where there are flights to the Galapagos. Australian passport holders do not require a visa but all visitors pay a  $130 national park fee when they arrive on the Galapagos.

TOURING THERE

Metropolitan Touring, Ecuador's longest-running tour operator, has various packages in the Galapagos, both land and sea based, that can be booked through the South America Tourism Office, southamericatourism.com

The writer was a guest of  LAN Airlines and the South America Tourism Office