A Dynamic Delta
Although the Mackenzie Delta begins officially just past the confluence of the Mackenzie River and the Arctic Red River, at Point Separation, it is not a static waterway. About 210 kilometres in length, with an average width of 62 kilometres in width and an area of 13,500 square kilometres, Canada's largest delta (the 12th largest in the world) continually changes shape within the boundaries of the Richardson Mountains to the west and the Caribou Hills to the east.

Formed by the slow, ongoing deposition of sediment from the Mackenzie, Peel and Rat Rivers into what was once a large bay, the Mackenzie Delta consists of three main channels leading to the Beaufort Sea, interspersed with islands, tidal flas, ponds and at least 25,000 shallow lakes. The size and distribution of the Deltas' lakes are constantly changing, as river sediments are deposited, main river channels penetrate their banks, and shoreline permafrost begins to melt. Lake formation is also influenced by flooding of the Mackenzie River, precipitation levels, and evaporation, particularly in areas of higher elevation.

Mackenzie Micro-Climate: Although the Mackenzie Delta flows through the taiga, the transitional zone between the boreal forest to the south, and into the treeless tundra of the far north, the relative warmth of the Mackenzie River water carries a ribbon of forest and shrub vegetation far beyond the treeline of surrounding colder territory. Similarly, the vast stretches of permanently frozen earth ("permafrost"), up to 100 metres thick, which stretch across the northern latitudes, do not extend beneath the Delta's main channels and lakes.

Muskrat Mecca
For a ubiquitous North American rodent that can survive in a drainage ditch, an urban swamp, or just about any place where water and food are available year round, the countless lakes, slow-moving channels, and willow banks of the Mackenzie Delta offer the ultimate in hospitable muskrat habitat. Amidst the patchwork of land masses and shallow waters that make up the Delta, a thriving muskrat population supports one of the richest fur harvests in Canada.

Musky Mouse: Valued for its thick, lustrous brown coat, the Delta muskrat weighs about 1 kilogram and is about half a metre long, tail included. Its name is derived from the musky-smelling substance that it produces to mark its breeding territory. Contrary to common belief, the muskrat isn't really a rat, and is not closely related to the beaver (with which it occasionally shares a lodge). It is actually a giant field mouse that has adapted to life in the water.

A supremely versatile mammal, the muskrat possesses several characteristics that have contributed to its success as a species:

• It has a long, slender, vertically-flattened tail that acts as a rudder as it swims, and is covered with scales for protection.

• Its nimble, hand-like front feet are useful for digging burrows and holding food. The long toes of its back feet have fringes of specialized hairs that create a paddle-like effect for efficient movement in the water.

• Its thick, waterproof fur provides both insulation and buoyancy.

• It can chew underwater, with mouth and nasal passages closed, by using chisel-like front teeth that protrude ahead of its cheeks.

• It can remain submerged for up to 15 minutes by slowing its heart rate and relaxing its muscles.

• It can build a lodge from riverbank vegetation, or burrow into a river bank if housing materials are not available. It can also subsist carnivorously on frogs, fish and crustaceans if suitable vegetation is in short supply.

• If climate conditions are favourable, it can produce a number of litters in quick succession. Blind, hairless, helpless newborn "kits" mature to complete independence within 6 weeks.

Survival Shelters: By using an ingenious series of surface structures, known as "push-ups," muskrats can survive the frigid waters and thick ice of the Mackenzie Delta's winter waterways. When the first thin ice of autumn begins to form over lakes and channels, the muskrat systematically chews a chain of plunge holes, about 10 metres apart along a straight line which can extend up to 90 metres from its main lodge. Over each hole, it builds a dome of plant material and mud, just big enough for one animal. Beneath the ice, the muskrat paddles from push-up to push-up, digging up roots and underground stems and carrying them to the surface to dine in the comfort of a snow-covered, insulated dome.

Fair Game: Prolific as they may be, muskrats seldom live beyond 2 years of age. On land, they are heavily preyed upon by foxes, wolves, lynx, martens and, bears. In water, mink are a particular threat, pursuing their muskrat prey into lodges, burrow systems and plunge holes. "Ratting" for furs and meat has long been part of the traditional lifestyle of northern First Nations, and muskrat trapping on the Mackenzie Delta has been a feature of the Delta economy since the 19th century.

More Mackenzie Delta Mammals
High above the normal treeline, narrow ribbons of spruce and tamarack continue to rim the larger channels of the Mackenzie Delta, tapering through ponds and lakes to a low-growing cover of cotton-grass sedges and dwarf willows. Within these Arctic and sub-Artic oases of food and shelter, at least 54 species of mammals thrive. They include:

• Black Bears and Grizzly Bears- Black bears are abundant in the Mackenzie Valley and Delta. The outer islands of the northern Mackenzie Delta - Kendall, Richard, Pelly - support a significant population of barren-ground grizzly bears.

• Moose and Caribou - Both species of the deer family are prevalent throughout the Delta. The moose prefer the willow-covered banks of ponds and channels, while vast herds of caribou summer on the barren tundra and winter in the forested transitional zone.

• Red Fox and Arctic Fox - While the red fox, with its distinctive white-tipped tail, favours habitat south of the Arctic tundra, its range extends north to the land of the white Arctic fox. The more diminutive Arctic fox feeds primarily on lemmings, but also trails polar bears in search of fresh seal leftovers. Red foxes dine on the Delta's abundant supply of muskrats and rabbits and occasionally, on Arctic foxes

• Snowshoe Hare - Following the forest north along the Mackenzie, the adaptive boreal rabbit makes good use of its long, four-toed feet and its ability to change its fur colour from the grey-brown of summer to the pure white of winter.

• Arctic Wolf - A sub-species of the gray wolf, the roaming Arctic wolf uses its keen sense of sight, smell and hearing to prey on lemmings, hares musk-oxen and caribou.

• Musk-Ox -Along the Arctic coast, shaggy, prehistoric-looking musk-oxen forage for grasses, willow leaves and Arctic flowers. Weighing up to 350 kilograms, the long-haired wooly oxen with their downward-curving horns excrete musky-smelling urine.

• Beluga Whale - Each spring, a distinct Mackenzie Delta stock of beluga whales leaves its wintering grounds in the Bering Sea to moult in the estuarine waterways of the Delta. After rubbing themselves on the muddy bottom, they allow the warm freshwater currents to rinse away old layers of thick skin.

Pingo Pinnacles
Thrusting high above the flat, treeless plain of the Arctic tundra, cone-shaped ice hills known as "pingos" appear in sharp contrast to the monotony of the far northern landscape. Volcano-like in appearance, but with a core that is frozen rather than molten, pingos are a consequence of underlying permafrost. About 1500 icy boils rise from the Mackenzie Delta, representing the largest concentration of pingos in the world.

The formation of a pingo begins when standing water in a low-lying area gradually expands into a lake:
• The lake water, which cannot permeate the permafrost, spills out over its banks and gradually drains dry.
• Permafrost closes in on the dried lake bed, freezing the sediments in the centre.
• An isolated frozen mound begins to form, gradually rising up above the tundra.
• A fissure opens at the summit of the frozen mound, exposing the ice core and allowing part of it to melt.
• A new lake forms high up in the crater of the icy hill.

Open and Closed: In far northern zones, where the permafrost never melts, "closed-system" pingos form without the addition of water from an outside source. Further south, where partial seasonal melting of the permafrost layer occurs, hydrostatic pressure contributes underground water to "open-system" pingos, often found at the base of south-facing slopes.

Summer Glory: Wildflowers of the Tundra

Like a brightly coloured blanket tossed suddenly over the drabness of the treeless tundra, a thick mat of brilliant, low-growing wildflowers blooms in the 24-hour daylight of the Western Arctic's brief summer. An estimated 100 species of northern wildflowers illuminate the land, including:
• Purple crocuses
• Red and purple lousewort
• Blue Arctic lupins
• Red, yellow and purple sweet peas
• Blue monk's hood
• White, pink and purple Indian paintbrush
• Yellow cinquefoil

Practical Plants: Labrador tea for calming the nerves, saxifrage for soothing upset stomachs, fireweed shoots for a vitamin-rich salad - even the northern Mackenzie Delta's "barren" tundra has produced plants with critical food and medicinal value. Humans and animals alike have feasted on crowberries, blueberries, cranberries, bearberries and lichens. Arctic heather, with its high resin content, has been an important source of fuel, and silky-plumed Arctic cotton heads were once combined with dried moss to make wicks for traditional seal-oil lamps.

Swans of the North
From a distance, it may be difficult to tell a tundra swan from its look-alike trumpeter cousin. Both are completely white, and of a similar graceful form. But at closer range, the tundra species can be identified by its somewhat smaller size (about 7 kilograms, compared to an average of 11 for the trumpeter), the presence of a bright yellow spot at the base of its black bill, and a call which is higher and more melodious than the deep, brassy voice of the trumpeter.

Firm Foothold: Tundra swans of the northern Mackenzie Delta region are part of a distinct "western" North American population of almost 90,000 birds. Further east along the Arctic coast, in the areas of Baffin Island and northwestern Quebec, the "eastern" population has been estimated at about 103,000 swans. Their combined numbers vastly outnumber the less populous trumpeters by about 12 to 1.

Tundras breed, at 4 or 5 years of age, in late May or early June, as soon as the snow has melted from the tundra. Nesting conditions must be favourable; if it is an unusually cold or snowy spring, no eggs will be laid. Swan pairs (male "cobs" and female "pens") mate for life, building nest mounds of grasses and sedges about 2 metres across, and .5 metres high, on points or islands in sheltered, marshy areas. Elevated above water level, the nests keep the eggs from being submerged, and provide a lookout point to guard against predators.

Fast Flyers: Young tundra "cygnets" develop the ability to fly about 3 weeks faster than trumpeter swans, allowing the species to breed in more northern latitudes. Even so, mortality of the downy juveniles is high, due to cold and starvation. As small lakes and ponds start to freeze as early as September, surviving young swans must be fully feathered and ready to migrate to larger, ice-free lakes. As the flocks hop-scotch their way south, fleeing the ever-encroaching ice, many more young birds freeze to death en route. The challenge of the tundra swan's long migration route - as far south as central California - contrasts with the protective isolation of the bird's far northern breeding grounds.