CINCINNATI, Ohio (WDTN) — Adorable hippo siblings Fiona and Fritz are continuing to bond – with the supervision of Bibi of course.

Video posted on Twitter by the Cincinnati Zoo shows baby Fritz and big sister Fiona playfully fighting on Friday, Feb. 17.

Fritz stands close to Bibi, and opens his mouth wide at Fiona as she returns the gesture.

The post’s accompanying caption reads, “Fritz acting all big and brave once his mom is behind him.”

According to a representative of the zoo, hippos use their mouths to play, show affection, give warnings and explore their world. The zoo’s website said hippos can open their mouths about three times wider than humans can!

For more information about the zoo and the hippo family, click here.