In a 2015 documentary on dolphin behavior, a filmmaker claimed that dolphins get high on puffer fish. Puffer fish release a poisonous nerve toxin that can be deadly to humans. In the film footage, the dolphins don't eat the fish. They toss the fish around like a ball, and take turns with it. Afterwards, the dolphins appear to be in a trance-like state. The filmmaker suggests that dolphins use puffer fish to enjoy a natural high, just as other animals enjoy fermented sugarcane, nectar, or berries. Some sceptics say there is no scientific proof that puffer fish give dolphins a natural high. One researcher says that the dolphins would have to eat the puffer fish to feel the effects of the toxins. Another says dolphins may be immune to the toxins, like some sharks. Regardless of whether dolphins are affected by the toxins, they certainly have fun playing with objects, including ball-shaped fish.