Whales and Dolphins

Please remember not to swim with wild whales or dolphins in the Cayman Islands. Observing a wild whale or dolphin is a rare privilege in the Cayman Islands, however, wild animals – especially lone dolphins – can be unpredictable and dangerous when approached by swimmers. Therefore, DoE is warning members of the public not to enter the water with wild whales or dolphins, for the protection of both the animals and people.

Natural History

Most cetaceans lead a K-selective life history strategy, represented by long life expectancy, reaching sexual maturity late and reproducing few offspring with lengthy gaps between breeding years. All cetaceans give birth to only one calf; this is related to energetic limitations of reproducing in marine environments. The amount of nutrient needed for the calf from the mother and the amount of available nutrients available to the mother dictate low fecundity. Physiological adaptations to living in marine environments have led to cetaceans evolving compact streamlined bodies; therefore there is no room within the mother for more than one calf. Calves need to be large and fully formed to have the best chance for survival. Cetaceans nurse their offspring with a high fat content milk and calves are dependent on their mothers for about a year. Cetaceans are highly intelligent and social, with strong bonds between family members reinforced by constant interactions. Behaviour and hunting techniques are passed on through generations from adults to juveniles. There are some general differences between Mysticeti and Odontoceti life histories.

Mysticeti are all large bodied with long life expectancies; the longest lived mammal is thought to be the bowhead whale, where the oldest one recorded was at least 211 years old. Mysticeti make long migrations from cooler productive waters in which they feed, to warmer tropical or subtropical water where they calf and breed; the only exceptions being Bryde’s, bowhead, and the Indian Ocean Population X of humpback whales. Mysticeti engulf large quantities of water, containing high concentrations of plankton, small fish or crustaceans, in their mouths. Their expanding buccal cavity allows them to engulf huge quantities of water; they then close their mouths and expel the water through the baleen, trapping their prey which is then swallowed. The water and food within are filtered through racks of baleen, which are bristly plates of keratin that fray. Foraging behaviour differs between species, some species populations feed cooperatively, more notably this is associated with humpback whales which employ techniques such a bubble netting or the use of loud feeding calls to corral prey.

Odontoceti have more varied life history strategies than Mysticeti. Their body size and life expectancy ranges from less than 25 years for the small (<6.23ft/1.9m) harbour porpoise to over 70 years for the large (<60ft/18.3m) sperm whale. Their use of habitat is diverse and primarily species dependent, ranging from shallow coastal and deep pelagic water to estuarine and fresh water systems. The foraging behaviour varies with habitat. For example sperm whales and beaked whales use echolocation to hunt at extreme depths (often up to or over 6000ft/1.8km)as there is no light in these deep waters. Similarly river dolphins use echolocation to forage in often murky water, although agility and fast movements are imperative to capture their prey in these environments, which is a stark contrast to the slower sluggish movements of deep divers. There are also well documented cases of co-operative foraging within Odontoceti species, notable examples include pods of bottlenose dolphins and killer whales hunting.

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