These baby rhinoceroses live at Care for Wild Africa Rhino Sanctuary in South Africa. Redditor Nkandla works there. He says they are fed milk every three hours, and make these noises when their milk is gone.
The sad part is that the little rhinos are in the sanctuary due to poachers killing their mothers.
They should never have needed to come to us in the first place. They are the victims of poaching, even if they're still alive. We do everything we can to give them as normal a life as possible and the bigger they get, the less dependant on us they will become. Our bigger rhinos, which were once in the same position, are already grazing in the big open fields, without any form of human interaction.
We really do hope to have them back out in the wild one day!