Pi led an interesting life since childhood. At one point he simultaneously observed three religions (Hinduism, Christianity, and Islam). Unfortunately, he lost both his parents and his brother in a tragic accident at sea. He survived the ordeal and provided different accounts of his situation at sea. One of his accounts seemed factual. However, it was plain and uninteresting. His other account was exciting and presented with attention-grabbing myths. The meerkats and the carnivorous island appear in his exciting version. Thus, the existence of the meerkats can be explained as an aspect of symbolism.
In my opinion, the meerkats represented people, and the island represented the world. During the day, the meerkats fed on fish provided by the island and at night they sought the safety of the tree and avoided the base of the island, which turned toxic. The day symbolized life and the night symbolized death. The meerkats symbolized people/souls trapped between the two cycles. Pi refused to be trapped and decided to leave the island. Thus, the meerkats on the island were an attempt by Pi to express his view of the world and the people in it.