These are dangerous places to be at the bottom of the food chain.
Unable to run, Nothronychus relies on brute strength.
Tyrannosaurs are predators that will eat anything,
even one of their own, whether they've killed it or not.
And a discovery found in Montana of a number of meat-eating dinosaurs...
appeared to show that being such an unfussy eater
could have dramatic consequences.
It seems scavenging can hold hidden dangers.
This tyrannosaur wasn't killed by Nothronychus.
There's a more deadly killer at work here.
All the predator's bones were found alongside
the edge of an ancient stagnant lake.
And all of them died at the same time.
Similar mass killings have been found today among birds.
And the killer, a fast-acting, naturally-occurring, deadly disease,
botulism.
Botulism is caused by bacteria that can thrive in rotting carcasses.
We think that the dinosaurs, too, might have been victims
of this lethal and invisible killer.
Once a carcass is poisoned, it is quickly passed on to any animal that eats it...
with lethal results.
But plant-eaters, like Nothronychus, are usually safe from such deadly killers.
By completely changing its diet,
Nothronychus shows the extraordinary adaptability
of the group known as the theropod dinosaurs.