WhatsApp Messenger for iOS has been
updated with the ability to search for animated GIFs right from within WhatsApp.
That is you can now send and receive animated GIFs and also can share short
videos and Live Photos from iPhone 6s and iPhone 7 as animated GIF images. 
WhatsApp Messenger for iOS has been updated with the ability to search for animated GIFs right from within WhatsApp
Just
3D Touch any live photo from Attach — Photo/Video Library and choose
“Select as GIF.” To get started tap on the GIF search button on the
bottom left for the perfect animated GIF right from within WhatsApp and tap
Attach – Photo/Video Library to send.

So go ahead and download the updated WhatsApp
Messenger to get animated Gif feature