Now he travels the world for National Geographic, spending more than 200 days on the road to make programs to stream on Disney+.
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His latest is called "Animals Up Close" and it's called that for a reason.
"We go and find individual animals or individual animal families and follow them," Gregory said. "I think when you follow an animal like that you suddenly get insight into just how complicated and challenging their lives are."
That's one theme, which runs throughout the new episodes on Disney+.
But there's an even bigger message.
"The key to our, future on earth is protecting our last, wild places, but also really focusing on co-existence so that people can live alongside each other," Gregory said.
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He has the passion of a true believer born of a lifetime spent tracking the world's animals, but he also has the skill of a born storyteller who uses the newest tools.
"Technology has evolved so much certainly in the last four to five years with things like drones, thermal imaging cameras that allow us to see into the darkness for the first time, re-breathers that allow us to stay under the water longer than ever before," Gregory said.
Gregory travels the globe so you get to meet some of the world's most exotic and exciting creatures without ever leaving your home.
"For this show, we need to have incredible, animal behavior," he said. "It has to have a fun adventure to try and find that animal, and it has to have a bigger environmental story to it."
"Animals Up Close with Bertie Gregory" is from NatGeo and shown on Disney+, both owned by the same parent company as this station.