North Amer­ica

From the north­ern tun­dra to the south­ern swamps, wildlife here has to cope with in­tense sea­sonal change and ex­treme weather events.

BBC Wildlife Magazine - - SEVEN WORLDS | ONE PALNET -

The third largest con­ti­nent is North Amer­ica. It oc­cu­pies about 16.5 per cent of the world’s land­mass and, like Asia, it ex­tends from the Arc­tic to the trop­ics. The big dif­fer­ence is its es­pe­cially ex­treme weather, which is all down to its ge­og­ra­phy.

In Asia, the ma­jor moun­tain chains run in an east–west di­rec­tion, but in North Amer­ica, the Rock­ies and Ap­palachi­ans are aligned north–south. In be­tween are the vast grass­lands of the Great Plains and a com­plex of very dif­fer­ent wildlife habi­tats, from steppe in the north and hot deserts in the south­west to swamps and bay­ous in the south and south­east. It means that, with noth­ing to im­pede it, cold po­lar air can bar­rel down to­wards the Gulf of Mex­ico, where it meets warm air from the trop­ics.

The re­sult is tor­na­does.

The USA ex­pe­ri­ences up to 1,717 ma­jor tor­na­does a year: more than any­where else in the world. And, if that’s not enough, the south­ern and south­east­ern parts of North Amer­ica, in­clud­ing the Caribbean, are reg­u­larly slammed by par­tic­u­larly pow­er­ful hur­ri­canes that swing in from the trop­i­cal At­lantic.

The reg­u­lar oc­cur­rence of these ex­treme weather sys­tems makes the con­ti­nent unique.

Rain­for­est bears

On the coast to the west of the Rock­ies, the Pa­cific Ocean en­sures that the cli­mate is mild and damp, both sum­mer and win­ter. There are no ex­tremes here. As a re­sult, it sup­ports the largest tracts of tem­per­ate rain­for­est in the world. They stretch from south­ern Alaska to north­ern Cal­i­for­nia, where they are home to the Amer­i­can black bear and, on Canada’s Van­cou­ver Is­land,

a sub­species that is slightly larger and darker than its main­land rel­a­tives. The Seven Worlds North Amer­ica film­ing team vis­ited the is­land in search of a mother and her cubs, and dis­cov­ered that the fam­ily reg­u­larly went beach­comb­ing. Wildlife cam­era­man and drone op­er­a­tor Ber­tie Gregory was with the team.

“One of the best parts of film­ing on these big land­mark se­ries is the amount of time you get to spend with the an­i­mals, es­pe­cially if you get to fol­low known in­di­vid­u­als. I had man­aged to find a fe­male bear with two small cubs, so we spent about four weeks fol­low­ing their daily rou­tine,” re­calls Ber­tie.

“We filmed them mainly at low tide each day, when they came out of the for­est and be­gan to for­age on the beach. At low wa­ter, the sea re­treats from the many in­lets along the coast, re­veal­ing vast boul­der fields.

Un­der the rocks is a ver­i­ta­ble smor­gas­bord ready to sat­isfy a hun­gry bear. The mother would sniff amongst the boul­ders un­til she smelled a crab, then she’d flip over the rock and grab the food be­fore it nipped her nose. The amaz­ing thing was that the boul­ders were very heavy, yet she turned them over with just the deft move­ment of her paw. The cubs, which were su­per cute, learned from their mother, and while we were there we saw how they pro­gressed from flip­ping over peb­bles to tack­ling quite large stones. With all that weightlift­ing from an early age, it’s no won­der that adult bears are so strong!”

Stream­ing with life

Mov­ing rocks about came to be a bit of a theme in the North Amer­ica episode, with di­rec­tor Sarah Whal­ley head­ing for the rivers of the South­ern Ap­palachi­ans to find a fish – the river chub – that

builds huge mounds of peb­bles in or­der to impress fe­males.

“The first time I donned a wet­suit and snorkel and put my head un­der, I was blown away. The colour­ful life in front of me was as strik­ing as that on a co­ral reef. It’s such a vi­brant, but lit­tle-known world. Peo­ple would stop and ask us what we were film­ing (well we did look odd float­ing face down in the river!) and, when we showed them, they couldn’t be­lieve what was in their own back­yard. This area is a hotspot for aquatic life. There are more species of fresh­wa­ter fish, cray­fish and sala­man­ders in these wa­ters than any­where else in the tem­per­ate parts of the world.

“The river chub is ac­tu­ally quite a com­mon fish in North Amer­ica, but the lengths to which he goes to build his mound is ex­tra­or­di­nary.

Once a male got go­ing, there was no stop­ping him. He’d col­lect and place one peb­ble after an­other, all the while watch­ing for fe­males, un­til he had a pyra­mid-shaped mound about a me­tre across. There were times when he would place a stone and it would roll off, but he im­me­di­ately put it back in its right­ful place.

Fussy ar­chi­tects

One day, we watched as a male built a nest, then de­con­structed it, and re­built it a half-a-me­tre away – they re­ally can be quite par­tic­u­lar.

“Un­for­tu­nately, the chub’s del­i­cate ecosys­tem is un­der threat from hu­man en­croach­ment. It was brought home to us every day. Our cam­era­men would lift their heads out of the wa­ter and hear gun shots from the nearby shoot­ing range.”

“The first time I put my head un­der, I was blown away. The colour­ful life in front of me was as strik­ing as that on a co­ral reef.”

A fe­male po­lar bear leads her two cubs through a patch of colour­ful fire­weed. Dur­ing sum­mer, with no sea-ice to hunt on, po­lar bears in this area are re­stricted to the shores of Hud­son Bay, Canada.

A beach­comb­ing black bear teaches her cub to leave no stone un­turned. In South Dakota a fe­male prairie dog watches over her pups. A road­run­ner perches on a stump to get a bet­ter view of his ter­ri­tory in the Sonora desert.

To­tal land area: 24.71 mil­lion km² Hu­man pop­u­la­tion: 427 mil­lion Pop­u­la­tion den­sity: 24 per km² Num­ber of coun­tries: 23 (+ 9 de­pen­den­cies) Coun­try with the most threat­ened species: United States, 1,818* Con­ser­va­tion threats: habi­tat de­struc­tion, degra­da­tion and frag­men­ta­tion, in­va­sive alien species, dis­eases, over-hunt­ing, pol­lu­tion and cli­mate change Every au­tumn the wa­ters off the coast of Florida turn dark with the mi­gra­tion of mil­lions of grey mul­let. They hug the shal­lows for safety. 5 The male river chubb cre­ates a nest out of rocks. Smaller fish such as bright orange ‘shin­ers’ crowd in to lay their eggs in his im­pres­sive stone pile. THE STATS *In­cludes IUCN Red List cat­e­gories: Crit­i­cally En­dan­gered, En­dan­gered and Vul­ner­a­ble.

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