How do you compare the adrenalin rush of a face-to-face underwater encounter with a great white shark with a fleeting glimpse of a critically endangered Sumatran rhino? Or how can you compare sitting quietly next to a bright red flower, mesmerised by fast-living hummingbirds in their iridescent suits, with the spectacle of millions of monarch butterflies at their winter roost?
This is the great pleasure of wildlife watching: every encounter is different. But it made picking the best of the best – my personal selection of the hotspots that have made the greatest impact on me over 30 years of travelling the world in search of wildlife – particularly difficult. Here is a selection.
Rubbing shoulders with mountain gorillas, Uganda
It's only a one-hour encounter – and there is an awful lot of travelling and trekking to be done beforehand. But rubbing shoulders with wild mountain gorillas is likely to be one of the most emotional, humbling and exhilarating 60 minutes of your life.
There are currently about 800 mountain gorillas left in Africa: 480 in the Virunga volcanoes, which straddle Uganda, Rwanda and the Democratic Republic of Congo (DRC), and some 310-340 in Bwindi Impenetrable Forest, Uganda.
In Bwindi, an island of 128 square miles of equatorial rainforest, surrounded by plantations, the Uganda Wildlife Authority has habituated seven gorilla families to receive human visitors. These consist of as few as seven animals to as many as 36, led by a mature male or "silverback" along with his harem of several females, various immature "blackback" males, and youngsters.
The trek in can take anything from less than an hour, if you're lucky, to as long as 11 hours, if you're not. It all depends on where your allotted gorilla family happens to be at the time.
Within minutes of entering the forest you are sweating and panting, crawling and clambering your way along slippery paths and precipitous mountain tracks. But the moment you come face-to-face with your first gorilla, the mud, the sweat and the tears are a distant memory. Standing in the heart of a seemingly limitless jungle, with a family of the largest primates in the world, is one of life's greatest pleasures.
How to do it
Gorilla treks operate year-round. Fly to Entebbe, then drive to Bwindi. There are several lodges, tented camps, community rooms and campgrounds in Buhoma, near the park headquarters. Gorilla-watching permits for each trek needs to be booked in advance.
Leaping with lemurs, Madagascar
When it decided to slip away from the ancient mega-continent of Gondwana some 160 million years ago, Madagascar unwittingly made a good tactical move. The new island, roughly the size of France, travelled a couple of hundred miles east before settling off the coast of southern Africa. There, while the rest of the world grappled with the emergence of Homo sapiens, it was able to develop completely unscathed.
Visiting this chip off the old Gondwana block is rather like landing on another planet. The plants and animals are vaguely familiar — they resemble monkeys, hedgehogs and civets, for example — yet they are actually lemurs, tenrecs and jabadys. What's happened is that in Madagascar, evolution has come up with different solutions to the same problems as elsewhere in the world. More than 80 per cent of the wildlife inhabiting the 1,000-mile-long island — including every single native terrestrial mammal — is unique to Madagascar.
The undisputed stars are lemurs. No fewer than 100 different species are currently recognised. They are found nowhere else, apart from small populations of introduced mongoose and black lemurs in the nearby Comoros Islands. They range in size from diminutive mouse lemurs (the smallest primates in the world) to indris (the size of large monkeys).
There are two species on the top of everyone's wish-list: ring-tailed lemurs and aye-ayes. With their black-and-white coats, soft-toy cuddliness and air of swaggering arrogance, ring-tailed lemurs are great fun to watch. Whereas aye-ayes are just plain weird – undoubtedly among the strangest, most enigmatic and most endearing animals on the planet. But whether it is lemurs you are after, or any of the other unique mammals, from fosas to tenrecs, or the myriad endemic birds, amphibians, reptiles and insects, Madagascar never disappoints.
How to do it
The best months to visit are generally April to early November. Fly to Antananarivo, then explore on a naturalist-led organised tour, or independently using the famous taxi-brousses (mini-buses or converted vans).
Cruising with polar bears, Svalbard
It is possible to see polar bears in many parts of the Arctic and sub-Arctic, but apart from tourist-crazy Churchill, in northern Canada, the Norwegian archipelago of Svalbard is one of the easiest — and wildest — places for a close encounter. There are believed to be 3,000 bears in the islands and surrounding frozen seas; if you join an expedition cruise in July, you would be very unlucky not to see quite a few of them.
Svalbard is a dramatic and awe-inspiring wilderness of huge blue and white glaciers, snow-covered mountains, and steep-sided fjords. It consists of three main islands — the biggest and better-known Spitsbergen, Nordaustlandet and Edgeoya — as well as many smaller ones.
The archipelago is one of the most northerly landmasses in the world — separated from the North Pole by a few hundred miles of frozen ocean. It is imprisoned by ice for eight months of the year and is gripped by perpetual darkness for four.
But, during the brief Arctic summer, it undergoes an extraordinary transformation. This forbidding place turns into a land of 24-hour daylight, with flower-filled tundra, towering sea cliffs crowded with millions of seabirds, and a crazy-paving of ice that provides a home for polar bears, walruses, and ringed and bearded seals.
Polar bears can be seen almost anywhere, but since they favour areas with plenty of ice, they are less often seen in the west of Spitsbergen.
How to do it
Expedition cruises (typically lasting 7-14 days) operate mainly from early June to August. Discover the World (discover-the-world.co.uk) offers an "Around Spitsbergen" trip.
Bumbling around Borneo
The island of Borneo is divided between three different countries: Indonesia (which owns Kalimantan), Brunei (one of the world's smaller countries, but incredibly rich on oil money) and Malaysia (which owns Sarawak and Sabah).
I particularly like Sabah, because it includes many of the most accessible wildlife-rich regions of the island. With some 10,000 species of flowering plants, 900 species of butterfly, 520 species of bird and nearly 200 species of mammal — it's hard to know where to begin with this land of milk and honey.
There are many splendid wildlife places to visit, but one of my favourites is the Danum Valley Conservation Area. It is a good place to see wild orangutans (there are believed to be about 500 of the apes in the conservation area) and is home to nine other primate species. Night walks and drives offer the chance to see two — the western tarsier and slow loris — as well as flying squirrels and even leopard cats.
Other mammals you might see include Bornean pygmy elephants, Bornean red muntjac and mouse deer. And Danum Valley is home to such mouth-watering rarities as Sumatran rhinos, Malaysian sun bears, clouded leopards and flat-headed cats. While you may well find signs of their presence, don't expect to see them unless you are incredibly lucky.
There are some lovely trails through the forest and a 1,000ft-long, 90ft-high canopy walkway. Early morning is best for seeing some of the more elusive mammals, while nocturnal walks, drives and boat safaris can be productive.
How to do it
The dry season is from May to October, although it is not always dry. Fly via Kuala Lumpur or Singapore to Kota Kinabalu, then hire a car or use river boats to reach more remote areas.
Following Darwin's footsteps, Galápagos Islands
The place that provided the inspiration for Charles Darwin's earth-shattering theory of natural selection, the Galápagos Islands need little introduction. A land of stark lava formations, cactus forests, lush green highlands, turquoise bays and quintessential tropical beaches, this extraordinary archipelago flaunts wildlife at every turn.
There are 13 islands larger than four square miles, plus six smaller islands and over 100 islets. Every island has its own unique atmosphere, distinctive landscape and inimitable wildlife – so the more islands you visit, the more variety you are going to see.
Most visitors have a top-10 wish-list: Galápagos penguin, flightless cormorant, blue-footed booby, waved albatross, magnificent frigate bird, Darwin's finch (any one of 13 species), Galápagos giant tortoise, marine iguana, Galápagos sea lion and Galápagos fur seal. Everything else is a bonus.
It's not just a question of where you go — but when. Wildlife activities vary greatly from month to month. There is always something going on.
How to do it
Fly from Quito or Guayaquil on the Ecuadorian mainland, to Baltra or San Cristóbal. The only practical way to explore the Galápagos is by live-aboard boat. A two-week trip will allow you to explore most key visitor sites.