Struggling with a bunny noise- anyone got any good ideas?

The Grandson turned 2 last week and rather than add to half of Toys R Us to toss aside and play with the packaging we decided to take him out somewhere special for his birthday. Being a real animal lover we decided on a children’s zoo. The sun was shining and the bag was packed with satsumas and nappies ( don’t need much else for him), sensible shoes on and off we went . At the entrance we bought our bag of feed for the goats and started our way round. His like of horses quickly escalated into an obsession when he saw the shetland ponies. With much clapping and clip clopping of our mouths we managed to move on. The goats gratefully ate our offerings, and the pigs snuffled some off us too. Highlight of the day though had to be feeding the lambs. The Grandson held a lamb and gave the bottle ( after we repeatedly told him it wasn’t ‘boo’ for naptime) to the greedy guzzling ball of fluff. The bunnies were let loose into the pen and amongst much screaming from the other children the Grandson stood there, bunny in each arm- not even flinching. So we have now added 2 more animals to our favourite list- along with sounds of course- although we are struggling with a bunny noise- anyone got any good ideas?