Dolphins
Dolphins are aquatic mammals that are members of the scientific families Platanistidae (river dwellers) and Delphinidae (ocean dwellers). Where some authorities list dolphins as close relatives to whales, most authorities cite that dolphins are actually a type of toothed whale. To mediate the opposing points of view, some experts refer to dolphins according their suborder name, Odontoceti/Odontocete. The name "dolphin" is also used to describe an unrelated species of fish. A common dolphin grows to approximately 8 feet in length and 165 lbs. This fish-like mammal generally has a black to dark blue upper body, a white underside and a dorsal fin that has the appearance of a sickle. Its average life span is 50 years. One of the most widely known species of dolphins is the bottlenose dolphin (Tursiops truncates).
Natural Enemies
Dolphins only have two natural predators, killer whales and sharks. Killer whale attacks are somewhat rare; bull sharks, tiger sharks and white sharks lead the way in attacking dolphins. Some experts believe that shark attacks on dolphins are the consequence of sharks and dolphins sharing many food sources. Generally, humans are not dolphin predators because dolphins are not a major food source in most societies and cultures. However, humans have inadvertently become dolphin adversaries by frequently and unintentionally catching them in commercial fishing nets.
Individual Strategies
Dolphins use specific strategies to defend themselves against predators. Their first course of action is to try to outswim their attacker. If this is unsuccessful, they use an evasive technique that includes battering the underbelly of a predator with their snout.
Pods
Battering is also used when dolphins mobilize as defensive units called pods, attacking predators as a group. A protocol of pod strategy consists of a large adult male serving as a scout, roaming the dolphin group's periphery, watching out for predators and investigating unfamiliar regions. The scout reports back to the dolphin group to relay gathered information. Dolphins are known for their highly developed language that includes specialized vocalizations of clicks, pops, squeaks, grunts and whistles. Dolphins commonly swim in groups of two to 15 dolphins.