Forests are usually places of dappled light and muted colours, where the wildlife cleverly camouflages itself. Not so on Christmas Island, a volcanic speck stranded in the Indian Ocean, 1,600 miles north-west of the Western Australia capital, Perth.
Here, the forest floor is stained crimson thanks to its seething carpet of native red crabs, unique to the island. During the breeding season, which starts around the end of November, they stage a mass migration from rainforest to ocean. It's one of the world's great natural spectacles, once drawing awed admiration from Sir David Attenborough, who dubbed the place "the kingdom of the crabs".
Apparently up to 120 million of them may live here, and it seemed so when I visited. The large crabs – the island has 20 native species, including the red variety – seemed to be everywhere: on beaches, roads and in the national park that covers two-thirds of this island.
My guide was Lisa Preston, from Island Explorer Holidays. She drove me through the narrow bush tracks to the island's national park with extreme care. But she was unable to avoid the occasional casualty. Hearing a crunch beneath her tyres, she let out a wail: "I'm a Cancerian and it strips my heart out every time! Sometimes when I close my eyes at night, I see a sea of crabs."
Our destination that morning was The Dales – a dreamy area of wetland, streams and waterfalls. Lisa led the way through an enchanted forest. Vying for attention were arenga palms, strangler figs and elegant Tahitian chestnuts, which have distinctive buttress roots like great struts rising from the forest floor. Hundreds of crabs scurried among rotting leaves, including the coconut crab, the world's largest land invertebrate, which can be the size of a small dog.
The former British territory was first spotted on Christmas Day, 1643, by a British sea captain, William Mynors. Australia has controlled the island since 1957. However, Christmas Island is closer to Java in Indonesia than to Australia.
Ethnic Chinese and Malays, the descendants of indentured mine workers, make up 85 per cent of the population. Buddhist and Taoist temples, scattered around the island, testify to its mixed heritage, as do the noodle shops and the trilingual road signs. On the world stage, though, Christmas Island is known as the site of Australia's main offshore processing centre for asylum-seekers. One camp on Christmas Island can accommodate up to 2,000 people, which is more than the island's permanent population.
This remote spot hit the headlines just over a year ago when a boat carrying Middle Eastern asylum-seekers travelling from Indonesia was shipwrecked, killing up to 50 people. Visitors may well see a Navy patrol vessel planted in the main harbour, Flying Fish Cove, or even the latest group of would-be refugees being ferried ashore.
Christmas Island is undergoing a makeover. Since it was settled in the late 19th century, the mainstay of the economy has been phosphate mining. You can still watch phosphate, which is used to make fertiliser, being loaded on to ships via a striking looking cantilever at Flying Fish Cove. But now that the reserves are dwindling, the islanders need another way to make money. The local tourism authority is promoting the island as a "green" destination, playing on its profusion of endemic species to sell it as "the Galápagos of the Indian Ocean".
The conventional approach to Christmas Island is a four-hour flight from Perth. Travellers who make the journey will discover a place of subtle charms. Party animals will be bored, because the nightlife consists of a few low-key bars and restaurants, most of which shut early. Sunbathers should look elsewhere, too: the few available beaches are small and rugged. But it's the perfect place for twitchers, who flock to Christmas Island from all over the world. Wandering along a coastal path to a place called Margaret Knoll, we saw golden bosuns and endangered frigate birds soaring on the ocean breezes. The terraced cliffs encircling the island are studded with white dots: colonies of nesting red-footed boobies.
The island is a popular destination for venturing beneath the surface, too, as I discovered on a snorkelling trip in deliciously warm water. The venue was West White Beach, a half-hour boat ride from Flying Fish Cove. According to the locals, the visibility averages 100ft; the marine life – which includes green and purple parrot fish and, in season, whale sharks – is extraordinary. We spent almost an hour drifting through a pristine coral garden. "I remember the first time I dived here, I nearly flipped," says Linda Cash, who runs the local tourism association. "It was so clear, I swear I could see Indonesia."
Beyond Christmas Island, at least from the perspective of Perth, lies the archipelago with the curious name of the Cocos (Keeling) Islands. This Australian external territory is the place to go if Christmas Island is too lively – and the two are easily combined on a round-trip.
Consisting of two atolls, one a wildlife sanctuary, the other a necklace of 26 coral cays, Cocos is a tropical haven, albeit a rather eccentric one. Just two of the sunburnt specks of land are inhabited: Home Island is home to 500 or so Cocos Malays whose ancestors worked on the copra plantations; West Island is inhabited by about 130 Europeans. The two, situated on opposite sides of a lagoon, are linked by ferry.
Home Island was settled by the Scottish Clunies-Ross family, which established the plantations and brought over the Cocos Malays. West Island was settled separately after the Second World War, hence the effective segregation. WestIsland has all the tourism infrastructure; the Cocos Village Bungalows are excellent. A dawn "canoe safari", led by a resident Australian couple, Ash and Kyle James, explores several offshore islands, and features an excellent breakfast, complete with champagne, at a time when I'm not usually even awake.
For visitors to this quiet backwater, there is sailing, diving, fishing and beach-combing. Alternatively, you can just curl up in a hammock. West Island has one restaurant, one café and one supermarket. The focus of community life is the one pub, the Cocos Club – a tin-roofed building that doubles as the cyclone shelter and as the pint-sized airport's departure lounge.
Locals include Johnnie Clunies-Ross, a sixth-generation descendant of the original Scottish settlers, who ruled Cocos as a fiefdom for 150 years. Clunies-Ross's father was forced to sell the islands to Australia in 1978; his son – obliged to abandon the family's ancestral mansion, Oceania House – became a clam farmer. Nowadays he lives in a modest bungalow on West Island. If you want to hear his story, Johnnie can be found in the Cocos Club most nights. He appears to harbour no bitterness about his fate. "This isn't the end of my family's story," he told me, "it's just a different chapter, or perhaps a different book. I wouldn't say I would not enjoy being rich. But you can only drink so much beer, and what else is there to spend money on?"
Travel essentials: Christmas and Cocos Islands
* You can fly to Perth on a range of airlines, including Qantas, Emirates, Etihad, Malaysia Airlines and Singapore Airlines. Virgin Australia (0843 104 7777; virginaustralia.com) flies from Perth to Christmas Island twice a week and to Cocos once a week; one-way fares start at A$464 (£309). Flights between Christmas and Cocos start at A$194 (£129) each way.
* The Sunset on Christmas Island (00 618 9164 7500; thesunset.cx). * Cocos Village Bungalows (00 618 9162 7711; cocosvillagebungalows.com). * Cocos Castaway (00 618 9162 6515; cocoscastaway.com).
* Tour operators on Christmas Island include Island Explorer Holidays (00 618 9322 9561; islandexplorer.com.au) and Christmas Island Wet 'n' Dry Adventures (00 618 9164 8028; divingchristmas.com). On Cocos (cocos-tourism.cc), you can borrow a pushbike for free. Ash and Kyle James run dawn canoe safaris (book in situ).