MARINE MAMMALS IN THE CENTRAL MEDITERRANEAN

Dolphins are very often mistaken for sharks and many large fish sightings around the Maltese Islands refer to the presence of dolphins. A shark may be distinguished by the presence of a vertical tail fin and 5-7 gill slits containing gills like those of an ordinary fish. Their mode of swimming is also different, and while a dolphin when sighted is "rolling" in the process of breathing, the shark's progress is steadier. A number of large sharks belonging to several species have been captured or sighted from around Maltese shores.

Cetaceans are broadly divided into two groups: the toothed (suborder odontoceti) and the whalebone or toothless whales (suborder mysticeti). The former include the smaller creatures such as dolphins and porpoises whose diet is carnivorous. The teeth in these may be well evident or alternatively may be concealed below the gum. The toothless whales feed on small organisms filtered from the sea by their great mouth-fringes or whalebone (baleen). Whalebone consists of rows of triangular hairy plates arranged transversely with their free ends hanging down into the mouth cavity. The inner edge of each plate is frayed out into a hair-like fringe, which all together form two sieve-like surfaces. As the whale glides through the sea, it takes in gulps of water which it squeezes out through this sieve. Small organisms are trapped in the bristles and are licked off and swallowed. These large whales can consume as much as 1.5 tons of food each day by this means. Six species of whalebone whales have been reported to occasionally enter the Mediterranean, including the 30.5 meters long Blue Whale. There is however no definite record of any specimens being taken or sighted in Maltese waters, and all cetacean species recorded belong to the suborder odontoceti. The Toothed cetaceans are represented in Maltese waters by eight species. A key to their identification is given below. There are in addition six other species recorded from the Mediterranean. Only accurate documentation of specimens encountered by sea-farers can hope to establish the correct list.

2a. - Tip of lower jaw well behind the foremost limit of the massive head. Back fin present, made up of gradually decreasing humps continuous to tail. Large size to about 18.5 meters length ....................................Sperm Whale
2b. - Tip of lower jaw to about the same level as tip of snout. Back fin present ................................3

3a. - Angle between forehead and snout definitely marked......................................4
3b. - Angle between forehead and snout forms no distinct angle............................7

4a. - Bulging forehead above a very short inconspicuous beak. Black colour throughout except for white area just behind chin. Back fin long, low and recurved near middle of back. Flippers slender and long, about one-fifth of the body length. Large size generally about 7 meters long ............................ Pilot Whale
4b. - Profile of head passing gradually into that of beak...........................................5

5a. - Size large, up to 7 meters. Beak short and not distinct. Dorsal fin behing middle of body. Anterior part of body coloured cream-white, distinct from the dark skin ........................ Cuvier's Whale
5b. - Size smaller not exceeding 5 meters. Beak long and distinct..........................6

6a. - Length up to 3.5 meters. Beak about 7.5 cm long in middle line. Recurved dorsal fin at middle of back. Colour black or dark brown with white throat and belly ...................................... Bottle-nosed Dolphin
6b. - Length up to 2 meters. Beak narrow and long, as much as 15 cm in middle line. Dorsal fin recurved and in mid-body position. Colour of back dark with two elongate lens-shaped arrangement of yellowish, white and dark bands on the body sides.......................Common Dolphin

7a. - Large size in the region of 4-6 meters in adult ..........................................8
7b. - Small size in the region of 1.5-2.0 meters. No narrow beak, with an evenly rounded snout. Triangular fin at middle of back. Back black, belly white ............................. Common Porpoise

8a. - Size large reaching 6 meters in adults. Head evenly rounded, forehead not prominent. Dorsal fin mid-way in body length, recurved, moderate size. Colour black all over. Flippers narrow and pointed ................................. False Killer Whale
8b. - Length up to 4 meters. No distinct beak and a slightly bulging forehead. Dorsal fin high, in mid-body length, recurved. Body colour dark grey, darkening to black on fins and tail. Ventral surface lighter grey ........................... Risso's Dolphin

The identification of cetaceans is however not as clear and distinct as is suggested by the identification key. Very often sightings consist of nothing more than a brief glimpse of the dolphin's back during a normal breathing "roll", unless the sighting occurs at quite close quarters or unless the dolphin jumps clear. The key above would serve to identify stranded or captured dolphins, though a brief sighting can also be useful. Once sighted from a vessel, there are several things that one can do to attract dolphins and encourage them to maintain contact, enabling one to obtain a better view for identification purposes. Try and maintain a steady course at 5-10 knots and avoid making loud or sudden noises that might frighten the animal. Do not hesitate to reduce speed and circle round them but avoid sudden changes of speed or direction. Never run at them. It is thought that they are attracted to high-pitched repetitive sounds and might well be attracted to music. Dolphins have gained a reputation for coming to the aid of drowning men, but it may be better not to put this to the test!

Another sea-mammal which inhabits the mediterranean is the Monk Seal. This mammal is not a cetacean but belongs to the order Carnivora, and is thus related to dogs, cats and weasel. Unlike the cetaceans, this sea-mammal comes onto the land to rest and to give birth to its young. The world population of the Monk Seal are threatened with extinction, and while fairly small stable populations are found in some regions of the Mediterranean, estimates of the total population only number 500 individuals.

Family: ZIPHIIDAE Gray, 1865
Genus: ZIPHIUS Cuvier, 1823
Ziphius cavirostris Cuvier, 1823
Cuvier's Whale
maltese:Balena ta' Kuvjer
Geographical range: This species is the most widely distributed of the beaked whales, with a worldwide range in all tropical and temperate seas. They appear to prefer warm and deep waters. They also occur in the Mediterranean Sea being relatively frequent in the waters of Corsica. First recorded in Maltese waters by LANFRANCO (1969) but a cetacean sighted by MEDLYCOTT (1870) may have belonged to this species (SAVONA-VENTURA,1979a\b). LANFRANCO (1969) notes that according to maltese fishermen this species is not infrequent in our seas, being indistinctly referred to as "denfil", but DEPT. OF ENVIORNMENT (1992) records the species as being noted only once. The MARINE LIFE CARE GROUP (MALTA) recorded a stranded specimen at Qawra in December 1995.
Biological characteristics: Colour of the head, lower jaw and part of the body may be cream white separated from the dark skin of the rest of the animal by an oblique line passing from the anterior end of the dorsal fin to the posterior end of the lower jaw. Back often scarred by long linear streaks. Head profile passes gradually into the beak. General form rather stout. Back fin behind body middle with concave posterior edge. Length: up to 8 meters.

Genus: MESOPLODON Gervais, 1850
Mesoplodon bidens Sowerby, 1804
Sowerby's Whale
Geographical range: Cosmopolitan. Relatively common in Northern waters and possibly occurs in the Mediterranean. Never recorded in Maltese waters.
Biological characteristics: Colour mostly black, often with irregular white blotches or steaks, sometimes white on belly. No definite beak, passing gradually into the receding "forehead". Back fin behind the body middle with slightly concave hinder edge. Length: up to 4.5 meters.

Genus: HYPEROODON Lacepede, 1804
Hyperoodon ampullatus Forster, 1770
Bottle-nosed Whale
Geographical range: Fairly common species in the Northern Atlantic. Occurs occasionally in the Mediterranean, never reported from Maltese waters.
Biological characteristics: colour dark grey to black above, some grey or white on the undersurface. Flippers and flukes dark on both surfaces. Prominent bulging forehead above a well-defined robust beak. Small dorsal fin well behind middle of back, flippers are also small. Teeth may be concealed below gums so that the mouth appears entirely toothless. Length: adult specimens have been known to reach a maximum length of about 9.5 meters.

Superfamily: DELPHINOIDEA Flower, 1864
Family: DELPHINIDAE Gray, 1821
Genus: DELPHINUS Linnaeus, 1758
Delphinus delfis Linnaeus, 1758
Common Dolphin
maltese: Denfil komuni
Geographical range: This dolphin is a pelagic species which inhabits both costal and offshore waters of the tropical, subtropical, and warmer temperate seas of the world including the Mediterranean Sea. Reportedly very common in Maltese waters (TALLACK,1861; GULIA,1890; GULIA,1913; LANFRANCO,1969; SAVONA VENTURA, 1979a\b, DEPT. OF ENVIORNMENT,1992). GULIA (1890) list as very rare a species Delphinus feres (Dum.) but no other reference to this name is available.
Biological characteristics: dark colour of back does not extend far down on sides. White belly, but salient features of the sides are two elongate lens-shaped light areas giving a figure-of-eight appearance distinguishable at a distance. General form slender and graceful. Snout long, narrow and well defined. Back fin in mid-body with backwardly directed tip. Length: up to 2.5 meters, generally about 2 meters.

Genus: PRODELPHINUS van Beneden & Gervais, 1877
Prodelphinus euphrosyne Gray, 1846
Euphrosyne Dolphin
maltese: Stenella
Geographical range: Typical North Atlantic and Pacific species. Recorded from the Mediterranean by a few captures. Its superficial similarity to the Common Dolphin makes for confusion between the two. Recorded by the MARINE LIFE CARE GROUP (MALTA) as a dead specimen at Marsaxlokk in January 1996. Listed as protected by DEPT. OF ENVIORNMENT (1992) as Striped Dolphin, Stenella coeruleoalbus.
Biological characteristics: Darkly pigmented on the back, white on the belly. Narrow dark band extending from eye along side to vent with a branch given off above base of flipper. Darkly pigmented flippers inserted on the light part of the body. General form slender similar to the Common Dolphin. Beak sharply defined from "forehead". Back fin in midbody length projecting backwards with a concave hinder edge. Length: up to 2 meters.

Prodelphinus frontalis Cuvier, 1829
Spotted Dolphin
Geographical range: Typically found in the Atlantic, Indian and North Pacific Oceans. It is possible that this species, occasionally found in the Mediterranean and may enter Maltese waters though it has never been recorded.
Biological characteristics: Dorsal parts including the fin marked with whitish or light grey spots. The inferior parts are lighter but with darker spots. Similar in form to the other dolphins and Prodelphinus euphrosyme. Length: 1.8-2.0 meters

Genus: TURSIOPS Gervais, 1855
Tursiops truncatus Montagu, 1821
Bottle-nosed Dolphin maltese: Denfil geddumu qasir
Geographical range: Largely distributed in warm and temperate waters. Various subspecies are described, but the Mediterranean form appears to belong to the subspecies truncatus. The subspecies ponticus Bobrinskii, 1944 is found in the Black Sea and the species Tursiops aduncus Ehrenberg, 1883 in the Red Sea. The Bottle-nosed Dolphin does not appear to be as common as the Common Dolphin, but this may be due to mistaken identifications. Recorded from Maltese waters (GODWIN,1880; LANFRANCO,1969; SAVONA-VENTURA,1979a/b, DEPT. OF ENVIORNMENT,1992, MARINE LIFE CARE GROUP (MALTA), stranded at Marsaxlokk in January 1996).
Biological characteristics: Colour of the back and sides black or dark brown. Throat and belly white but black towards the tail. General form robust with a short well-defined snout. Dorsal fin in mid-body with tip directed backwards and hinder edge concave. Length: up to 3.5 meters.

Genus: STENO Gray, 1846
Steno bredanensis Lesson, 1828
Rough-toothed Dolphin
maltese: Denfil tat-tikki
Geographical range: The distribution of this species is world wide in tropical and warmer temperate seas. It occurs in the Atlantic, Pacific and Indian Oceans, and in the Caribbean Sea, the Mediterranean Sea, the Red Sea, the Bay of Bengal and the Hawaiian Islands. Never recorded from Maltese waters, but listed as protected by the DEPT. OF ENVIORNMENT (1992).
Biological characteristics: Colour of the dorsal parts of the body and the fin purple black; flanks sprinkled with rather large stellate spots. Snout and inferior parts of the body white or reddish white with purple spots. Body relatively slender similar to the Common Dolphin. Snout long, compressed laterally and not well defined from the forehead. Length: up to 2.6 meters.

Genus: LAGENORHYNCHUS Gray, 1866
Lagenorhynchus acutus Gray, 1828
White-sided Dolphin
Geographical range: Atlantic but especially in Northern waters. Observed and photographed on the Dalmatian coast of the Adriatic. Never recorded from Maltese waters.
Biological characteristics: Darkly pigmented on back, tail and flippers. Each flank conspicuously marked by elongated streak of lighter colour extending from below the dorsal fin on to the tail stock. General form rather robust with short distinct beak. Dorsal fin in midbody length, large rounded backwardly projecting tip, hinder margin concave. Length: 2.7 to 3 meters.

Genus: GRAMPUS Gray, 1828
Grampus griseus Cuvier, 1812
Risso's Dolphin
maltese: Denfil ta' Risso
Geographical range: Risso's Dolphin is distributed throughout the seas of the world, preferring waters deeper than 100 fathoms. Reportedly rare in the Mediterranean (DEPT. OF ENVIORNMENT,1992), but LANFRANCO (1969) comments that it is often taken from around Maltese shores. Various records of this Dolphin's occurrence in Maltese waters are found in local newspapers (ANON.,1962; ANON.,1963), but on reviewing these records these appear to be non-specific and on one occasion referred to the Bottle-nosed Dolphin (SAVONA VENTURA,1979a/b). THE MARINE LIFE CARE GROPU (MALTA) recorded a specimen found stranded at Fomm ir-Rih in April 1996. Another specimen was reported at Marsaxlokk in March 1997 (ANON., 1997)
Biological characteristics: General body colour grey darkening to black on fins and tail. Lighter grey or even white on ventral surface. General body form rather robust. No distinct beak. Slightly bulging forehead. Back fin high in mid-body, rather acutely pointed backwards. Length: up to 4 meters.

Genus: ORCINUS Fitzinger, 1860
Orcinus orca Linnaeus, 1758
Killer Whale or Grampus
maltese: Orka
Geographical range: The Killer Whale is worldwide in its distribution, but is more frequent in cold seas. Relatively scare in the Mediterranean but may have been more frequent in the past. Recorded only once from Maltese waters (ANON.,1914), but this specimen appears to have been a specimen of the False Killer Whale (SAVONA-VENTURA,a/b). Listed as protected by DEPT. OF ENVIORNMENT (1992).
Biological characteristics: The black back is distinctly defined from the white of the belly. Various white patches on the back and sides. General form robust. Beak absent. Back fin high situated in mid-body length, acutely pointed and triangular. Very massive teeth. Length: males up to 9 meters, females about 4.5 meters.

Genus: PSEUDORCA Reinhardt, 1862
Pseudorca crassidens Owen, 1846
False Killer Whale
maltese: pseudorca Geographical range: The species is a warm water cetacean widely distributed in the world seas. Occasionally enters the Mediterranean. Definitely recorded from Maltese waters by LANFRANCO (1969), but a stranded cetacean in 1914 (ANON.,1914) may have belonged to this species (SAVONA-VENTURA,1979a/b). Listed as rare in Maltese waters (DEPT. OF ENVIORNMENT, 1992)
Biological characteristics: Entirely black except for white scar marks. Head evenly rounded without a beak. Back fin midway of moderate size and the tip pointing backwards. Length: males up to 5.5 meters; females up to 4.8 meters.

Genus: GLOBICEPHALA Lesson, 1828
Globicephala melaena Traille, 1809
Pilot Whale
maltese: Balena sewda
Geographical range: Vast distribution with sporadic occurrence in the Mediterranean. Recorded once in Maltese waters (ANON.,1973; SAVONA-VENTURA, 1979a/b). Listed as rare in Maltese waters by DEPT. OF ENVIORNMENT (1992).
Biological characteristics: Black over most of the body. White area just behind chin which may extend as a white streak on belly. General form long and slender. Bulging forehead above a very short beak. Long low back fin projecting backwards in midbody length. Length: generally about 6 meters.

Family: PHOCAENIDAE Bravard, 1885
Genus: PHOCAENA Cuvier, 1817
Phocaena phocaena Linnaeus, 1758
Common porpoise
maltese: denfil bla geddum
Geographical range: It occurs generally in the costal waters of countries bordering the North Atlantic, in the North Sea, Baltic, White Sea, and Greenland Sea. Apparently of accidental occurrence in the Mediterranean, but may be confused with the Common Dolphin. Reported from Maltese waters (GULIA,1890; LANFRANCO,1969; SAVONA-VENTURA,1979a/b; DEPT. OF ENVIORNMENT, 1992).
Biological characteristics: Back black, belly white or cream with the sides grayish. Snout evenly rounded with no beak. Back fin in body middle triangular. Length: up to 1.8 meters.

Suborder: MYSTICETI Flower, 1864
Family: BALAENOPTERIDAE Gray, 1864
Genus: BALAENOPTERA Lacepede, 1804
Balaenoptera physalus Linnaeus, 1758
Common Rorqual, Fin Whale
maltese: Balena Kbira
Geographical range: This species has a worldwide distribution and it undertakes extensive migrations between high and low latitudes. It is the most frequent of the Whalebone Whales in the Mediterranean Sea. It has been recorded from the Adriatic Sea. Never recorded from Maltese waters. Listed as protected by DEPT. OF ENVIORNMENT (1992).
Biological characteristics: grey above, white below. Head asymmetrically pigmented. General form long and slender. Snout broad and low. Back fin in hinder third of the body. Length: usually about 20 meters.

Balaenoptera acutorostrata Lacepede, 1780
Lesser Rorqual , Minke Whale
maltese: Balena zghira
Geographical range: More or less cosmopolitan. It is less frequent than Balaenoptera physalus in the Mediterranean. Never reported in Maltese waters. Listed as protected by DEPT. OF ENVIORNMENT (1992).
Biological characteristics: General colour black above, white below from chin to tail flukes. General form resembles Balaenoptera physalus, but is rather stouter. Snout from above appears triangular. Back fin prominent in hinder third of the body. Length: up to 9 meters.

Balaenoptera musculus Linnaeus, 1758
Blue Whale
Geographical range: Distribution is worldwide with extensive migration correlated with feeding and breeding habits. Generally absent from the Mediterranean, but rare records have occurred. Never recorded from Maltese waters.
Biological characteristics: Dark bluish grey on the back and belly, the belly speckled with white spots and pale mottling. Snout broad, low and flattened. Back fin small and triangular in hinder third of body. Length: up to 30.5 meters.

Balaenoptera borealis Lesson, 1828
Sei Whale
Geographical range: Worldwide in distribution, seemingly preferring warmer seas. Occasionally recorded in the Mediterranean, but never in Maltese waters.
Biological characteristics: Colour on the back bluish grey, somewhat lighter on the undersurface. A white area confined to grooving on the that and chest excluding the chin. Similar in form to the Fin Whale being less slender. Snout low and acutely pointed with the edge viewed from the side slightly arched. Back fin in hinder third of the body with the apex projecting backwards over concave hinder edge. Length: up to 18 meters.

Family: BALAENIDAE Gray, 1825
Genus: EUBALAENA Gray, 1864
Eubalaena glacialis Borowski, 1781
Biscayan Right Whale
Geographical range: Occurs especially in the northern Atlantic and adjacent seas. Rare in the Mediterranean and never recorded from Maltese waters.
Biological characteristics: General colour completely black all over with an occasional irregular white patch on belly. Large head, the upper jaw arched and narrow. The top of the head commonly with a rough horn projection. Mouth region frequently barnacle infested. Back fin absent. Length: up to 18 meters.

Genus: MEGAPTERA Gray, 1846
Megaptera novaeangliae Borowski, 1781
Humpback Whale
Geographical range: The humpbacked whale inhabits nearly all of the temperate and tropical seas of the world. In the northern hemisphere, this whale is distributed from the equator to about 70o N.L. Only occasionally recorded in the Mediterranean, never from Maltese waters.
Biological characteristics: Great variation in coloration, but generally black above, white below. Flippers and flukes usually white underneath. Robust general form. Snout short, broad with many tubercles on the surface. Similar tubercles are found on the chin and on the sides of the lower jaws. Rather small backfin in hinder third of the body with the posterior border only shallowly concave. Length: up to about 15 meters.

Order: CARNIVORA
Suborder: PINNIPEDIA Storr, 1780
Family: PHOCIDAE Gray, 1825
Genus: MONACHUS Fleming, 1822
Monachus monachus Hermann, 1779
Mediterranean Monk Seal
maltese: Monka, Bumerin
Geographical range: The Monk seal is a Mediterranean species, and outside this region is found in small groups on the Canary Islands and on the shores of Madeira. The species was first definately recorded from the Maltese Islands by a sighting in 1856 at Rinella, Malta (GULIA,1858-59), though a record of a half-man half-fish animal washed ashore in 1642 at l-Ahrax (Malta) may have referred to this species (ABELA,1647). GULIA (1890) reports another sighting at Munxiar near Marsascala, Malta in 1887. Recent sightings date to 1974 in the region of Ricasoli, Malta (ANON,1974; SAVONA-VENTURA,1984; DEPT. OF ENVIORNMENT, 1992).
Biological characteristics: Back dark grey or chestnut. Prominent white mark of variable size on underparts. Heavy body on land. Hindlimbs turned backwards. Dense fur. Claws on fore and hind feet (flippers). Length: 2.3-3.8 meters.

References