Before they were officially broadcast, sequences from Planet Earth II (Sundays, BBC One), the BBC's ravishing new documentary on the natural world, found their way into a relatively new and volatile ecosystem. A crowded biosphere where creatures hunt and scavenge for anything easily digestible, in the gaps between fighting viciously with rivals or parading to attract a mate, this is life as we know it on social media. The BBC have been entirely canny about it.

“Hey ladies,” yelped a post from BBC Earth, beside a clip composed for maximum cute virality: “This lovesick sloth will cross oceans to find a mate.”

From the evidence of the first programme in the series, themed around life on the world’s islands, this was not true. We first found the three-toed pygmy sloth, unique to Panama’s Escudo Island, hanging from sun-dappled tree branches with the practiced tranquillity of a stoner during reading week. True, he could muster enough hustle at the sound of a mating call to swim, but only across modest stretches of water.

There was something more revealing in his story, though: chiefly, that he had been given one. Filmed in spectacular close-up, accompanied by sprightly orchestral music and egged on by the anxious hush of David Attenborough’s voice over (“He does his best to put on a turn of speed…”), the sloth finally arrives at his destination only to discover – with a typically excellent “reveal” shot – that his would-be mate is already taken.

A couple of minutes later, while stalking the amorous advances of a fearsome komodo dragon, Attenborough huskily approves: "She's receptive. So far, so good." But, again, expectations are upended, this time with violent komodo combat. What chances do these species have, with the David Attenborough as their wingman?

Nature series, on the other hand, breed almost without interruption.

Planet Earth II comes 10 years after Planet Earth, a staggering undertaking for the BBC in 2006, the first such documentary in high definition, which itself followed The Blue Planet. "We can now show life on our planet in entirely new ways," begins Attenborough today, floating high above ice peaks in a blue hot air balloon. Indeed, the filming and editing is extraordinary, with lenses that can gaze deep into the eyes of tiny birds, or float above unreachable landscapes in liquid-smooth slow motion. This, he promises, will reveal "new wildlife dramas for the very first time". Why, then, does it seem so strangely familiar?

The answer may be that the BBC finds itself, almost unconsciously, in competition with Pixar. The revelatory intimacy of Attenborough's pioneering nature shows gave new access to the secret life of animals, and every discovery of struggle, courtship or nurture reminded us, helplessly, of our own. The anthropomorphic wonders of Madagascar, Happy Feet and Zootopia sprung up in the wake of such discoveries, animating human predicaments through cutesy creatures. The result is that we now watch life on our planet in entirely new ways too, apparently with the expectation of individuated and special stories: a uniquely "lonely" albatross, waiting for his long-distance lover; penguins undertaking "formidable commutes"; or indeed "lovesick"ocean-crossing sloths. New details in filming apparently demand new details in narrative: "wildlife drama" as Attenborough describes it, is a rapidly evolving genre.

You marvel at its construction as much as its visceral effect. How did they even get those shots of fiendishly camouflaged insects or leaping lemurs, which pass by in restless flickers of editing? In the first episode’s most breath-taking drama, who anticipated where the heads of freshly hatched marine iguanas would pierce through volcanic island sand, launching immediately into a panicked scramble away from darting snakes?

Absorbing as this is, Planet Earth II chases viewers as assiduously and expertly as it chases the fauna, rewarding you with sharable stories rather than lingering lessons. How about that baby marine iguana who wrestles out of a serpent's stranglehold ("A near miraculous escape!"), or that father penguin, guided by the pounding percussion of heroic music, searching for his starving chicks among 1.5 million ("Quite heart-breaking")? Where education once led such expeditions, emotion now becomes the main guide.

As with the first series, the documentarians turn their cameras briefly on themselves, and their efforts are laudable. But a more complicated relationship between nature and its observers is alluded to in the march of the red crabs, on Christmas Island, a phenomenon that brought them “world wide fame” and, as a consequence, an influx of yellow crazy ants that now threaten their existence. The programme is spectacular and benevolent and hugely entertaining, but there’s a sobering consequence behind transforming the natural world into compulsive memes or trailing along pests on journeys of discovery.

Even the way we watch the world can change it forever.