Dolphins

Introduction

Humans have always found dolphins to be enchanting creatures. Ever since the days of the first seafarers, they have been the subject of numerous works of art, literature, and myth. They are among the most intelligent of animals, as some species have brain-to-body mass ratios equal to that of a human being. They are also mammals, having evolved from land-faring creatures tens of millions of years ago. They are known for their extremely gregarious behavior. This report attempts to look at the characteristics, biology, reproductive habits of these amazing creatures. It also attempts to discuss the types of dolphins as well as their intelligence and interaction with humans.

Dolphins: Biological name

All dolphins are toothed whales belonging to the sub-order, odontocetes, of the order cetacea (see section on humpback whales for more information). As a group, dolphins are often referred to as "small" cetaceans, even though some of them are quite large, attaining lengths of over 20 feet. In addition, although the terms dolphins and porpoises are often used interchangeably, they really refer to two different types of animals. (Mukhametov Supin 119-121)

Porpoises belong to the family Phocoenidae. They are generally smaller and more robust species. Most attain about 5-7 feet in length. Porpoises have no distinct beak, or rostrum. Their foreheads slope almost uniformly to the tip of their snout, and their teeth are spade-like in shape. The family Phocoenidae is rather small, and consists of only six members. There are no porpoises found in Hawaiian waters(Goodson Klinowska Kastelein 255-267).

Dolphins belong to the family Delphinidae. Dolphins possess a distinct beak. Their teeth are conical in shape. Most species of dolphins are larger than porpoises, with the males usually being larger than the females. The family Delphinidae is the largest and most diverse family of the cetacean order and includes 26 living species. Several species of dolphins are found in Hawaiian waters.Below is the biological classification for the common dolphin:

Kingdom Anamalia

Phylum Cordata (vertebrates)

Class Mammalia

Order Cetacea

Sub-order Odontoceti

Family Delphinidae

Genus Delphinus

Species delphis

Types of Dolphins

Oceanic Dolphins

Oceanic dolphins comprise some 26 species, including such renowned taxa as the bottlenose dolphin (Tursiops truncatus) and the common dolphin (Delphinus delphis). They are the primary focus of this site, so the information presented here on them is much more detailed. One page is presented for each genus(Mukhametov 227-238).

Small Toothed Whales

The smaller toothed whales include such species as the killer whale (Orcinus Orca), the melon-headed whale (Peponcephala electra), and the pilot whales (Globicephala macrorhynchus and G. melas). Although called "whales", they are taxonomically more closely related to dolphins and are placed in the same family. This page discusses briefly all of the species(Williams 89-101).

River Dolphins

River dolphins are truly perplexing creatures, termed both "some of the most highly evolved cetaceans" and "evolutionary holdovers from millions of years ago." They have both the most highly developed echolocation systems of all cetaceans and such evolutionary vestiges as fingerlike structures on their flippers. Unfortunately, these are also some of the world's most endangered cetaceans, with several species on the verge of ...