Answer:
Bottlenose dolphins are probably the species of dolphins more researched, and most of this investigation is oriented to measure and assess their intelligence.
Bottlenose dolphins are intelligent problem solvers, and they can solve simple tasks and perform successfully in intelligence tests. These dolphins are smart enough to use tools to get things done easier, like using sponges to avoid injuries.
The advanced communication capabilities of dolphins also denote their superior intelligence in the animal world.
Read more about Dolphin Intelligence