"Rhinoceros are fierce"
Translation:Vifaru ni wakali
Because it's an animate noun (people and animals). These tend to follow M/Wa rules, although N/N animate nouns tend to keep their pluralisation agreements to help differentiate singular from plural (dada yangu, dada zangu, compared to the animate Ki/Vi rhino. kifaru wangu, vifaru wangu). They still follow M/Wa rules for adjectives (dada mkali, dada wakali).