This research from Bristol University tells us that dolphins who work as a team recognise those individuals who are likely to help others when needed and those that won’t or don’t. To those that don’t help they do not reciprocate help. It is said that they might hold a grudge against them and won’t help them when they need help in the future. It seems like sophisticated behaviour very similar to the behaviour of people which does not surprise me because dolphins are intelligent and they work in groups and in coordination with each other.
If you click on the link above the photograph you can read more on this if you wish.