Several dolphin species occur in Florida costal waters. The most common of these is the bottle-nosed dolphin (Tursiops truncatus), mistakenly called porpoises. Bottlenose dolphins have robust, powerful bodies that are blue-gray on top with lighter sides and bellies. As adults they are typically 6 to 12 feet long and can eat more than 20 pounds of mullet, sheepshead, pinfish, flounder and marine invertebrates each day. Bottlenose dolphins show a high degree of intelligence, have a wide range of vocalizations, and may cooperate in fishing or taking care of injured conspecifics.
Dolphins have been known to live into their 50s, and reach weights of up to 140-650kg.
Dolphins live both inshore and offshore along temperate and tropical coasts worldwide.
Inshore dolphins live in small social groups of approximately 10 individuals; while offshore dolphins form larger groups of 10-100 individuals. Dolphins travel about their home ranges (the geographical area that defines their home) in groups of 4-7 in shallower waters and more than 20 dolphins in deeper areas. The dolphins interact and re-form groups at will, somewhat like a kaleidoscope.
Dolphins are often heard clicking. Contrary to popular thought, clicking is likely not communication, but rather the sonar system dolphins use for navigation, food-finding and avoidance of predators. Clicks are one of three classes of sounds dolphins produce, in addition to squawks (whose purpose is unknown, although these sounds are made while dolphins are socializing), and pure tones, one of which is known as that dolphin's "signature whistle."
Dolphins cooperate in many ways, some species more than others. As a group they may guard against predation by sharks or support a sick or injured community member in the water by keeping it afloat. A few dolphins sometimes use the lengths of their bodies to encircle and pen a school of fish in shallow water, like horses rounding up yearlings, in order to feed. In addition, bottlenose dolphins often take turns feeding according to age, size, and health. Often two males of the same age form a lifelong pair bond and spend the majority of their time together, helping each other find suitable food and mates.
It is against federal law to feed or harass wild dolphins. Swimming with or feeding dolphins can be dangerous for both human and dolphin and should not be attempted. The NOAA Fisheries Service warns that disruption of normal behavior and activities can ultimately harm these mammals. Human/dolphin swim with and feeding interactions increases their risk of injury from boats, increases the incidents of entanglement in fishing gear to the point of being a nuisance to anglers, decreases their willingness to forage for food and may cause habituated behaviors to be passed on to calves and other dolphins. Inappropriate non-food items, contaminated food and food meant for human consumption can jeopardize the health of this species. Dolphin are also known to become aggressive to humans when seeking food or defending their territories in areas where feeding or swimming practices occur.
Image Credit: Amanda Nalley