[insects chirping] [thrilling music] [dinosaur bellowing] -[Narrator] 71 million years ago, in what would become modern day Alberta.

[birds chirping] Thousands of Edmontosaurus ruled over this lush landscape [Edmontosaurus bellows] of vast plains and meandering rivers.

[Albertosaurus grumbles] With deadly Albertosaurus stalking their every move.

-[Henry Sharpe] If you’re looking for a good meal, they were just giant walking piles of muscle, the McDonalds of the Cretaceous.

-[Narrator] Edmontosaurus were one of the most dominant plant eaters on the continent.

-[Henry] If you think of wildebeests in Africa right now that’s Edmontosaurus because they are everywhere here.

-[Narrator] Palaeontologist Henry Sharpe thinks they had a surprising survival tactic.

A vital key to their success.

[tapping with hammer] Did Edmontosaurus abandon their defenseless young?

-[Henry] Basically the animal, it was sitting on it’s belly, right, and then the different parts kind of fell to one side.

-[Narrator] The team has discovered the final resting place of a youngster they’ve nicknamed Gary.

-Gary is a juvenile Edmontosaurus, he would have been about four meters long and what we found mostly is the body, parts of the skull and the tail.

[tapping with hammer] -[Narrator] Gary’s bones are seemingly alone.

A long way from any adult Edmontosaurus.

And for Henry that poses a mystery.

Experts believe Edmontosaurus grouped together in herds.

Allowing them to close ranks and protect each other from marauding predators.

[Edmontosaurus bellows] -[Henry] And so living in groups means that you could have one or two animals kind of looking out while the rest feed.

It’s like a meerkat strategy.

-[Narrator] But despite being social animals, the team hasn’t found adults and youngsters buried together.

[crunching] -[Henry] It’s just adult Edmontosaurus in one spot and baby Edmontosaurus in another spot.

[birds and insects chirping] -[Narrator] Edmontosaurus young were about the size of a small dog and almost defenseless.

[Edmontosaurus young whimpers] -[Henry] Juveniles are just kind of running around beneath your feet, they’re hard to take of if you’re the size of two elephants.

[Edmontosaurus bellows] -[Narrator] And that’s not all, Henry thinks young Edmontosaurus hadn’t yet developed a defense feature found in adults.

-[Henry] The juveniles, the eye sockets face very much to the side erm, but in adults this bone right behind the eye actually inflates, there’s a big sinus in it and that pushes the eye sockets to rotate to face forward a little bit more.

-[Narrator] Adult Edmontosaurus eyes pointed forwards.

This means they could spot an approaching Albertosaurus pack, [suspenseful music] track its approach and act fast.

[snort] -[Henry] If you want to avoid a fast predator like Albertosaurus, maybe what you need to do is spot it from a long way away coz then you can get a head start, you need to get your herd together and move out.

[Albertosaurus snarls] -[Narrator] But with eyes on the sides of their heads, younger Edmontosaurus wouldn’t spot danger quickly.

[nasal huffing] Small, defenseless and unlikely to spot predators, this doesn’t seem like a recipe for success.

But Henry thinks Edmontosaurus had a clever solution to ensure the next generation survived.

Whilst the very youngest may have stayed with the herd, at a certain age the juveniles go it alone.

-[Henry] Yeah, Edmontosaurus are growing up kind of alone and probably sticking to the forests and away from the big open river plains where the Albertosaurus are waiting to, to eat them.

[panic nasal call] -[Narrator] Henry thinks this strange finding could be the secret to the species success.

-[Henry] For some reason, them abandoning their young is the way to go, it’s the one that’s helping most Edmontosaurus reach maturity.

It’s a weird strategy but it’s what they did and it’s what has worked.

-[Narrator] If Henry’s right, this strategy helped Edmontosaurus become one of the most abundant dinosaurs in North America.

In just a few years, juveniles like Gary will be the size of an elephant and armed with life-saving binocular vision.

Finally ready to rejoin the herd.

[music fades]