Many of these animals are almost die out.
1.die out :
disappear completely 灭绝
EX. Dinosaurs have died out long before.
die away:
(光、声音)慢慢消失,(风)停下来
He hid behind the door until the footsteps had died away.
The wind died away, and the leaves became silent.
很多这些动物都几乎要灭绝了.