Viewers pointed it out on Twitter.

The return of Planet Earth has been highly praised, as the compelling animal and nature programme continues to entertain us. While we love learning about the animal kingdom and seeing them interact, hunt and live, there is one part of the show that viewers are not happy about. On Sunday night's episode viewers took to Twitter to point out the fact that the sound was coming across as fake. People especially focused on the sounds the could be heard as a jaguar crunched into a caiman’s skull  and the sound of the millipede’s footsteps. https://twitter.com/akkwildlife/status/800591156706873344?ref_src=twsrc%5Etfw https://twitter.com/hughesroland/status/800999390995312640 https://twitter.com/JenRoseBresnick/status/800838837119422468 The BBC bosses have responded to the claims and have admitted to recreating some of the sounds in the studio. They do this to “create a sense of a wild place, as well as emotion and drama” according to the Sun. The producers added that they have a “limited range of microphones” to pick up the sounds while filming.

 “Range and ambient noise ensure quite a lot of wild sounds simply cannot be recorded in the field. “As a result, wildlife film-makers often turn to sound designers to recreate something that sounds like it would in the wild — a soundtrack that is true to nature.” They said.