In terms of production values and excitement this one goes right up there with such giants as "Speed of Life" and "In cold Blood". You'd think that the topic is too broad and well-known to really hold your interest. After all, we've all seen the insects, birds, reptiles, and mammals go through the motions: they are born, they bumble around, they gain skill and confidence, they mate... Repeat.
Maybe it's how well it's scored. The music is so great that this is basically Fantasia with animals.
Maybe it's the species selected. A Mongolian jerboa, for example, is extremely adorable not only in its huge-eared, fairy-tale looks, but also in its twitchy, terrified behavior. A young mantid's environment is an alien world, with horrific-looking predators. A tiny gosling starts its life with a 400-feet vertical plunge along evil-looking, jagged cliffs.
There are even a couple of jump scares.
Overall, very impressive. 9/10.