546 



FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



hydraphone a school of traveling porpoises sounds 

 something like a pack of hounds yelping with 

 their mouths closed. The bottle-nose dolphin 

 whistles under water with simultaneous release of 

 air. The noise-making of cetaceans is peculiar 

 in that they have no larynx or voice box, and the 

 sounds emanate from controlled movements of 

 gas within the various air passages. Sinclair 

 (1950) has recently shown that the auditory area 

 of the brain of the bottlenose dolphin is exception- 

 ally well-developed and that the olfactory nerve 

 is minute. Toothed whales probably cannot 

 smell. In contrast, the olfactory lobe of baleen 

 whales is rather well-developed. The eyes are 

 relatively small, and power of vision is weak in 

 most species. 



All cetaceans are covered with a layer of fatty 

 areolar tissue, known as blubber, which lies just 

 under the skin. Whale oil cooked out from this 

 material was the primary objective of the whaler. 

 In addition to being a great store of energy and 

 an insulation wall, the blubber possibly serves as 

 a reservoir for storage of o.xygen during deep dives. 

 This layer varies in thickness from an inch in 

 smaller porpoises to 18 inches in large whales. 



Young cetaceans are almost half the length of 

 the mother when born although only one-tenth 

 or less of her weight. They grow rapidly and 

 are nursed for more than a year. The writer 

 once measured a female bottlenose dolphin 

 8 feet 4 inches long, and her nursing calf 5 feet 

 7 inches long. Breasts are present on each side 

 of the vaginal openings, extending forward, and 

 can be seen as swellings of the abdominal outline. 

 The nipples are retracted in two slits. The milk 

 collects in large sinuses and is actively expelled 

 at the time of nursing which takes only a few 

 seconds. Whales mature at the age of 3 to 4 

 years. The age attained is unknown. 



The toothed whales pursue individual prey and 

 are known to live largely on fishes, squid, and 

 cuttlefish. Some dolphins also eat shrimp, and 

 certain fresh-water species possibly utilize some 

 plant material. The killer whale varies the fish 

 diet by attacking any other mammal found 

 swimming in the water. The baleen whales feed 

 by cruismg with their large mouths agape, taking in 

 planktonic crustacca, especially the euphausiids 

 and copepods, and the pteropods. Occasionally, 

 schools of small fishes are also engulfed. One 



baleen whale was found to have 2 tons of plankton 

 in its stomach. 



Some whales undertake long seasonal migrations 

 extending over vast stretches of the oceans. They 

 nevertheless may be rather sharply aggregated in 

 definite localities at the different seasons, probably 

 because of availability of food more than any 

 other factor. These areas were called "grounds" 

 by the old-time whalers and were given 

 individual names. 



Whales are comparatively intelligent animals. 

 The brain is large, and the cerebral hemispheres 

 are extensively convoluted. Studies of the play 

 behavior and other activities of the bottlenose 

 dolphin by McBride and his associates at the 

 Marineland Aquarium in Florida have led them 

 to rank the intelligence of this cetacean as lying 

 somewhere between that of the dog and the 

 chimpanzee (McBride and Kritzler 1951). 



CETACEANS OF THE GULF OF MEXICO 



The cetaceans of the Gulf of Mexico are not at 

 all well-known, as far as actual records go, and 

 it is only in recent years that some of the common 

 porpoises and dolphins have been recorded. It 

 may be assumed that practically all species known 

 to the western subtropical Atlantic are found in 

 Gulf waters. 



Most actual records are known from infrequent 

 strandings which have largely gone unnoted in the 

 literature. The whalers of a century ago combed 

 the seas of thev world rather thoroughly, but they 

 found no reason to sail often into the Gulf of 

 Mexico or the Caribbean Sea. The closest 

 whaling ground of any consequence was the 

 "Charleston Ground" off the South Atlantic 

 coast of the United States (Townsend 1935). 

 This fact and the relative infrequency of strand- 

 ings indicate that the cetacean population of the 

 Gulf of Mexico, especiallj' of larger species, is 

 small in numbers. 



In the following account only those species 

 known from actual records are treated individually. 

 Other species likely to be present are listed 

 together. 



Suborder Odontoceti. Toothed Whales 

 Family PHYSETERIDAE. Sperm Whales 

 Physeter catodon Linnaeus. Sperm Whale 



This is the largest of the toothed whales and the 

 largest predatory animal that ever lived on 



