The Dusky dolphin according to MammalMAP
Dusky dolphins were first described by John Edward Gray in 1828 from stuffed skin and a single skull shipped from the Cape of Good Hope. This spry cetacean is a medium sized dolphin measuring between 1.8 – 2 meters. Identification of dusky dolphins is relatively easy as its head is evenly sloped and it lacks a beak at the end of its snout. There is virtually no sexual dimorphism in dusky dolphins; although males tend to have more curved dorsal fins with broader bases.
Dusky dolphins rarely weigh more than 100 kgs. They have 24 – 36 pairs of small pointed teeth in each jaw. Usually the upper jaw has two less teeth than its lower half. Nonetheless, they are skilled herders when it comes to feeding time. They generally feed on large schools of fish by herding the fish together. This cooperative strategy can involve up to 300 dolphins working together to feed. Dusky dolphins will often leap before or after feeding. It has been hypothesised that this behaviour is an effort to recruit other dolphins to assist in the feeding activity.Common prey items of a dusky dolphins menu include a variety of different fish, anchovy, squid and shrimp. They are opportunistic feeders – they will feed at the surface or the bottom of the water. Dusky dolphins are highly social. They are known to approach ships so that they can bow ride as well as leap in the air in an acrobatic display. Playing and leaping in the air are critical activities for socialisation. Dusky dolphins also use squeals, squeaks, clicks and whistles to communicate. These calls are quite loud and can be heard up 3 km if the dolphin is out of the water. Even in the water, the sound can travel up to a kilometre. The IUCN classifies dusky dolphins as a data deficient species. An assessment of the global population of dusky dolphins is not possible with the current estimates of abundance and removals. Direct catches and bycatches of dusky dolphins have been large and continue in some regions. For more information on MammalMAP, visit the MammalMAP virtual museum or blog.
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