Lagenorhynchus albirostris, the Whitebeaked Dolphin. GENERAL BIOLOGY SIZE The whitebeaked dolphin is a medium sized, strongly build dolphin. It is approximatly 3m long, male individs are bigger then female. Its weight is approximatly 270 kg, though there are considerable variations in both size and weight.It has a thick beak and a large, strongly curved dorsal fin and a thik tail stock with a keel. COLOURATION The dorsal and lateral surfaces are dark gray to black, and it has a white coloration on the balley, reaching to the middle of the tail stock. It has several white or gray markings along its sides and flanks. A white area extends from above the flipper, along the flanks and over the back behind the dorsal fin. There are gray to white spots on the thorax and along the flanks, which all can be coloured with black spots and streaks. The balley is usually bright gray or white, and this white colouration usually extends to the beak. Hence its name the whitebeaked dolphin. Particulary in the eastern parts of the Atlantic specimens can have a gray or even dark beak, and this individs can easily be confused with their cousin, the whitesided dolphin. There is a gray to black blaze and a dark area at the tip of the lower jaw, which extends back to about a third of the length of the mouth. The blowhole is surrounded by an almost circular, dark gray to black patch. A large gray patch extends from behind the blowhole to the level of the flippers. IDENTIFICATION Most whitebeakes have circular scars from infections and very often they have scars from contact with fishing nets, boats etc.. These markings, together with their distinctive colouration can be used for photo-identification of individs. TEETH The whitebeaked dolphin has between 22 to 26 kone shaped teeth in each jaw. THE LIFE SPAN, BREEDING, ETC.. The life span of the whitebeaked dolphin is generally unknown. so are many other facts about this dolphin. They probably migrate to warmer, calmer waters or better feeding areas in connection with giving birth to their calves.
POPULATION SIZE,HABITAT, HOMERANGE AND MIGRATIONS POPULATION SIZE According to the SCANS transect observation in june 1996, using nine ships and two aircraft for the area, including the Northern Sea, Skagerak, Kattegat, the English Channel and the Celtic Sea, the population of whitebeaked dolphins in this area is estimated at 8.000 individs, 4.000 to 13.000 with a confidence interval of 95%.As our research area, between Skagen Reef and the Norwegian Trench is a part of the area covered by SCANS, we will do what we can to adjust our transect observation in a manner that makes it possible to make comparative studies. HABITAT Whitebeaks are found in cool, sub arctic waters of the North Atlantic, and some populations are observed in the northern Sea, probably follwing the Atlantic Currents. They are believed to be more coastal then their cousins, the more pelagic whitesided dolphins, and they probably favour habitats close to the continental shelves. Our research area between Skagen Reef and the Norwegian Trench, is an area, where the winterstorms press the atlantic watermasses into the north eastern part of the North Sea. Variations in deapth there are between some 50 and 700 meters. MIGRATIONS Surprisingly little is known about the migrations of the whitebeaked dolphin, and for that sake about its homerange too. It probably migrates towards warmer waters in connection with mating and the birth of their calves. The population in our research area is present there from march to november. Later whitebeaks are more frequently observed in the western part of the Northern Sea, north of dogger banks. Anyhow it is not known, if the population in our research area is connected with the whitebeakes observed north of dogger banks during the winter month. ANSWERS HOPEFULLY FOUND SOON. We are confident, that our intensive, two years observation of the whitebeaks in the Orion Belt will contribute with some answers about the whitebeaks migrations and homerange. COMPARATIVE STUDIES OF PHOTO IDs AND SATELLITE TRACKING Satellite tracking of some few individuals should give a reasonable impression of the movements during a season, and comparative studies of Photo-ID's from observations in Island, Rasmussen,98/99 and from the western coast of Scotland, by PGH Evans Sea Watch Foundation might also contribute with some hard needed answers about the whitebeaks migrations and homerange
SOCIAL BEHAVIOR , GROUP DYNAMICS, FEEDING... GROUP SIZE,HUNTING,SEXUAL MATURITY... Whitebeaks are most frequently observed in groups of 2 to 20 animals. Observations of grous containing several hundred to thousand individs are not uncommon. Whitebeaks are known to use fish herding techniques for hunting. Usually a group of whitebeaks herds a school of fish towards other small groups, thus entrapping the school of fish. Such fish herding techniques require a high degree of coordination and coopperative behavior. Individuals are communicating during hunting, utilizing whistles, breaches and various displays of surface behavior. Whitebeakes are frequently observed hunting and feeding in association with other dolphins, such as the whitesided dolphin, rissos dolphin and the bottlenose dolphin. They have also been observed feeding in the same area as fin whales, pilot whale and killer whale. Whitebeakes become sexually mature at an average size of 2,5 / 2,6 meters. Mating, as well as the birth of their calfs is believed to take place during the warmer month of the year, but veary little is known about this too.
SOUNDPRODUCTION AND ECHOLOCATION A LITTLE KNOWN AND MAYBE MISUNDERSTOOD SPECIES.. The whitebeaked dolphin is one of the species that is little understood, and the research about their sound production and eccolocation that has taken place so fare has left more unanswered questions then answers. Their vocalisations are thought to be similar to those of other Lagenorhynchus species, but this does not answer any question as to the specifics, since also other lagenorhynchus species may be quiet misunderstood. SO FARE So fare it is expected that the vocalisations of whitebeaks are best described as this. PULSE repetition rates varying from less than 10 to 170 pulses pr. second. Pulse frequencies reach at least 305 kHz. The max. source level is 180 dB re 1 mPa@ 1m. TONAL whistle frequencies ranging from appr. 6- at least 15 kHz, and are often at about 8 kHz. Max. source level is 180 dB re 1 mPa@1m. NEW RESULTS Rasmussen,Island,98/99. New results by M.Rasmussen, from Island,98/99 seem to indicate, that whitebeaks use pulse frequencies fare above 300 kHz, and that new knowledge should be achieved by utilizing sound recording equipment that can record at higher kHz levels. QUESTIONS TO BE ANSWERED The research by M.Rasmussen, Island,98/99 has left us the following questions, of which we would like to answer some in connection with our research in the Orion Belt. Do whitebeaks produce different signals, depending on background noise and geografical area? Are burst signals used, only in association with agressive behavior? How does the whitebeaks klik interval change during a huntingsequence? Do all individs react equally to signature whistles, using play back technique? How do dolphins distinguish between different whistles? Which parameters are important for the dolphins own classification of whistles? What is the exact source level for whitebeak whistles and over which distances can they be hered? How does the source level of klicks change over greater distances? What is the maximum source level for a whitebeaks click? How does the audiogram of a whitebeak look? How would the audiogram look, if clicks where used instead of pure sounds? Can a whitebeak hear a click, that is played back to it????? This and many other questions are unknown quantities about the whitebeaks sound production and eccolocation. we hope that we can find some answers to them during our two years project in the Orion Belt. CONTACT. For more details about sound production and eccolocation and the exchange of data, please, contact Marianne H. Rasmussen. marianne_ras@hotmail.com
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