Dolphins are highly intelligent mammals. Their closeness to humans may be caused by the following reasons.
1. Strong sociability: Dolphins are very social animals. They live in large groups and interact and communicate with other members. This sociability makes dolphins show a friendly attitude towards humans.
2. High intelligence: Dolphins are very intelligent animals, and their IQ can even be comparable to that of human beings. This high IQ enables dolphins to recognize humans and show a friendly attitude towards humans.
3. Curiosity: Dolphins are very interested in the surrounding environment and things. They like to explore new things and interact with humans. This curiosity makes dolphins show a friendly attitude towards humans.
4. Human interaction: In the interaction between humans and dolphins, humans usually give dolphins food or other rewards, which will make dolphins feel valued and concerned, thus showing a friendly attitude towards humans.
In a word, dolphins' closeness to humans may be caused by their strong sociability, intelligence, curiosity and human interaction.