Natasha Preston October 10, 2013 With so many heavyweights, picking five is a Herculean task, but we’re confident we’ve managed to unlock the faunal treasure chest to reveal the biggest and best wildlife encounters on Earth… Whether to sight a belligerent herd of Cape buffalo chasing down a male lion, sit beside a flora-feeding Mountain gorilla or witness a ravenous Grizzly bear gorging on salmon in British Columbia, the rewards are as huge as the animals. 1 - Blue Whale The monolith of the animal kingdom, the Blue whale is the largest creature to have ever lived. Up to 30 metres long, this ocean liner can consume an elephant’s weight in krill every day, take in 50 tons of water with each gulp, and blow spray up to nine metres high. A migratory species, the Blue whale frequents oceans the world over, feeding in high latitude polar waters during the summer months before returning to the tropics to breed in the winter. Baby Blue whales weigh a whopping three tons at birth and, feeding on 50 gallons of milk, pile on around 90kg a day. Nothing can prepare you for the moment one of these majestic mammals flaunts it eight-metre fluke next to your boat – it is a marine thrill without parallel.Weight: up to 170 tonsWhere: Sri Lanka and the Azores, Portugal 2 - American Bison North America’s heaviest land animal, these Ice Age descendants are formidable foes when forced head-to-head in battle. However, outside of the mating season bison are generally gentle grazers and as such, this once iconic symbol of the Great Plains was almost driven to extinction by 19th century settlers. Don’t be fooled by its lethargic posture and lumbering gait, a bison can reach speeds up to 40mph and is armoured with some pretty handy headgear! For the best chance of sighting these herbivore heavyweights head out into the geyser-studded plains of Yellowstone.Weight: up to 1,000kgWhere: Yellowstone National Park, USA 3 - Polar Bear A gleaming ivory coat contrasting against deep sapphire blue waters, a cub scavenging on the blubber-specked skeleton, or a pair of coal-like eyes peeking over a snowy ledge; whatever situation your first glimpse of a polar bear comes in, you can be sure it will be unforgettable. For anyone braving the Arctic chill, a sighting of this formidable ice predator is the top prize. The largest land carnivore in the world, the great white hunter has an extraordinarily powerful sense of smell, and seals denning within a kilometre of a hungry Polar bear should not rest on their flippers!Weight: up to 700kgWhere: Spitsbergen (Svalbard), Norway 4 - Mountain Gorilla Up in the jungle-clad hillsides of the mist-cloaked Virunga Mountains, lives the real king of the jungle. Across this volcanic range around a dozen Mountain gorilla troops are closely watched, their movements and social interactions all carefully monitored. A silverback weighs twice that of an average human male and has ten times the strength, but despite the intimidating chest-beating demeanour, they are really gentle leaf-munching giants. An hour alongside these intelligent jungle-dwelling primates will be the most emotionally intense, awe-inspiring sixty minutes of your life.Weight: up to 220kgWhere: Rwanda and Uganda 5 - Leopard The leopard may seem lightweight in comparison to the other big hitters on the bill, but once you see one of these dappled predators haul its lunch up a tree, there’s no denying this big cat really punches above its weight. Whether prowling the Mara plains, raising cubs in Kruger or sidling up to a watering hole over the granite of Yala National Park, the leopard is the prettiest predator to lay paws on the planet.Weight: up to 80kgWhere: Sub-Saharan Africa, Sri Lanka, Nepal and India.