1. March of the red crabs, Christmas Island
Where else can you come face-to-face with millions of crabs scuttling through scrub, over rocks, across roads, down cliffs and finally to the ocean? For most of the year, these dinner-plate-sized crustaceans – which adapted to living on land – forage among the rainforest undergrowth, picking up leaves, fruits, carrion and just about anything they can get their claws on. Reflecting their marine heritage though, the red crabs need to return to the sea to reproduce. The arrival of the monsoon dampens the environment, making it easier for the crabs to undertake the trek. Along the way, they face hazards like potential dehydration, ant attacks and being crunched by cars, though residents and park authorities try their best to keep the crabs safe. Once spawning ends, the crabs, in a reverse migration, head back to the forest.
Where: Christmas Island is an Australian territory in the Indian Ocean. It is home to 2,000 human residents and an estimated 120 million red crabs.
When: Late October through January
2. Leatherback turtle voyage, Pacific Ocean
If slow and steady wins the race, then the award must surely go to the leatherback turtle, which has been known to traverse the Pacific Ocean in a span of around 647 days – based on research gleaned from tagging. Believed to be guided only by the earth’s geomagnetic fields and oceanic gyres, the large creature can migrate more than 10,000km from its breeding grounds in Papua, Indonesia to feeding areas in Oregon on the Pacific Northwest Coast of the USA. Unlike other marine turtles, leatherback turtles can regulate their body temperature, enabling them to make the transition from tropical to sub-arctic waters, where they feed on their preferred diet of soft-bodied organisms such as jellyfish and other invertebrates.
Where: During nesting season, head down to the Caribbean coast of Costa Rica, where visitors can join local researchers at a remote station and help search for leatherback turtles as well as move the eggs to safe hatching sites.
When: October to March
3. Monarch butterfly marathon, North America
They are about 10cm in wingspan, weighing less than a gram each. Yet every autumn, the monarchs of North America flutter a few thousand kilometres, from as far north as Canada into the central highlands of Mexico, to avoid the harsh cold. They spend the winter clumped together on the branches and trunks of oyamel fir trees till spring, when they stir from semi-slumber and head back to summer feeding areas up north. How do such delicate insects accomplish this astounding feat? The females lay eggs along the way, so each round trip involves several generations of butterflies. This leads to the quandary of how the winged creatures find the same trees and follow the same routes every year, given that return visitors would be the great-great-great-offspring (or thereabouts) of previous visiting monarchs.
Where: See them huddled on fir trees in towering panoramas of orange and black at Mexico’s UNESCO World Heritage-listed Monarch Butterfly Biosphere Reserve. Popular areas include El Rosario, Sierra Chincua, Cerro Pellon and Piedra Herrada.
When: November through March
4. Passage of humpback whales, Hawaii
Imagine a 40-tonne whale launching itself clear of the ocean, then crashing back with a thunderclap, throwing up walls of whitewater. Or perhaps a robust male humpback belting out a whale song with a melody that reverberates through the hull of the boat. The humpback whales of Hawaii are an inspiring story of redemption. Thanks to global protection and establishment of the Hawaiian Islands Humpback Whale National Marine Sanctuary in 1992, there are over 20,000 humpbacks visiting the region – up from fewer than 1,500 after commercial whaling officially ended in 1986. Each year, the whales swim thousands of kilometres from places like Alaska to the warm waters of Hawaii, where they give birth, nurse their young and compete for mates. During this migration and extended stay in the tropics, the whales fast for roughly half the year. As summer approaches, the humpbacks head back north for concentrated feeding, in order to build up the energy to head back to Hawaii again the following winter.
Where: Though humpbacks live around the world, Hawaii is one of the most reliable humpback-watching destinations.
When: During winter and spring with peak encounters in February and March.
5. Northern elephant seal journey, South America
With food on their minds, the northern elephant seal undertakes two migratory journeys annually, travelling as far as 21,000km. Most of these journeys are spent underwater, and remarkably, each year, the mammals follow the same migratory course, arriving at the same place at the same time with clockwork precision. Every February and March, they leave their rookery beaches along the Mexican and Southern Californian coasts for frigid waters to feast on krill and squid. Their ultimate destination is the offshore foraging grounds in the North Pacific and the Gulf of Alaska. After feeding and storing layers of fat, they prepare for the return journey to their breeding grounds to moult and breed.
Where: California’s Ano Nuevo State Park, located between two major marine conservation areas, boasts one of the largest mainland breeding colonies for the northern elephant seals, where visitors can go on a naturalist-led tour and watch the cacophonous animals in action.
When: Late April and early May