Gervais' Beaked Whale

Maximum longevity: 48 years (wild) Observations: One specimen may have been over 48 years old (Ronald Nowak 2003).

The coloration of Mesoplodon europaeus is black or dark grey on the back fading to a lighter gray on the sides and belly. For a cetacean, the head is small with respect to total body size. The tails of ziphiids (beaked whales) are unusual among cetaceans in having no notch in the center of the fluke. Some stranded specimens, particularly adult males, have many scars on their bodies, presumably from sharks and fighting between males.

Nearly all ziphiids have a greatly reduced number of teeth, and Mesoplodon europaeus has only two in the lower jaw. These two teeth are are visible outside the mouth as small “tusks” near the front of the rostrum. Conchoderma, stalked barnacles, often attach themselves to these teeth. Tusk shape varies between species and it has been proposed that these difference evolved in order to aid the animals in differentiating their own species, as Mesoplodon species are otherwise very similar in appearance. It is extremely difficult to distinguish the similar-looking species of this genus by sightings, and sometimes even when using the diagnostic characters of the skull.

(Lynn and Ross, 1992; Martin et al, 1990; McLeod, 2000b; Robineau and Vely, 1993; Vaughn et al, 2000; Pitman, 2001)

Range mass: 1200 + (high) kg.

Range length: 4 to 5.2 m.

Other Physical Features: endothermic ; bilateral symmetry

Gervais' beaked whale is known to live to at least 27 years old in the wild.

(Pitman, 2001)

Range lifespan
Status: wild: 27 (high) years.

Average lifespan
Status: captivity: 48 years.

Mesoplodon europaeus lives in warm to tropical pelagic waters.

(Cetacea, 2001; Debrot and Barros, 1992)

Aquatic Biomes: pelagic

Mesoplodon europaeus is known only from strandings, so the known distribution may be affected by ocean currents and efforts in North America to retrieve stranded animals. Recorded from as far north as New York and as far south as Trinidad, Mesoplodon europaeus is probably the most abundant member of its genus in the Gulf of Mexico. Records from the eastern side of the Atlantic are more spotty, ranging from Ireland to Guinea Bissau in Africa. A relationship has been suggested between water temperature and prey species distribution, thus affecting the distribution of different Mesoplodon species.

(McLeod, 2000a; Robineau and Vely, 1993)

Biogeographic Regions: atlantic ocean (Native )

From stomach contents of stranded M. europaeus it is known that they eat primarily squid (Octopoteuthis spp., Mastigoteuthis spp. and Taonius spp.), deep sea shrimp(Neognathophausia ingens) and mesopelagic viper fish (Chauliodus sloani and Nesiarchus nasutus). The stomach is divided into multiple chambers. The purpose of this is undetermined, as squid and fish are easily digested, as opposed to the tough material eaten by most animals with such stomach morphology.

(Vaughn et al, 2000; Debrot and Barros, 1992; Martin et al, 1990)

Animal Foods: fish; mollusks; aquatic crustaceans

Primary Diet: carnivore (Piscivore , Eats non-insect arthropods, Molluscivore )

IUCN Red List of Threatened Species: data deficient

Perception Channels: tactile ; chemical

From distinctive scars on some stranded beaked whale specimens it is known that cookie-cutter sharks do attack M. europaeus. The whale probably uses its tusks to protect itself from this and other predators, as well as for interspecific fighting.

(Pitman, 2001)

Known Predators:

• killer whales (Orcinus orca)
• cookie-cutter sharks (Isistius)

Very little information is available, but females are thought to be sexually mature by the time they reach 4.5 m size.

(Martin et al, 1990; Poss, 1998; Pitman, 2001)

Key Reproductive Features: gonochoric/gonochoristic/dioecious (sexes separate); sexual ; viviparous

As with all cetaceans, the young are necessarily precocial at birth and Mesoplodon europaeus are about 2.1 m long at birth.

Parental Investment: precocial ; pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Female); pre-weaning/fledging (Provisioning: Female, Protecting: Female)

This species is assumed to be a deep diver (6) that only comes close to the shore to give birth, as many strandings are females with their newborn calves, and sightings of this whale are extremely rare (5). Gervais' beaked whale is nearly impossible to distinguish from other beaked whales when sighted at sea (2). Females are thought to be larger than males, becoming sexually mature at 4.5 m and giving birth to highly dependent young of just 2.1 m. The species is known to live to at least 27 years in the wild (2). They are thought to live in couples or small groups, and fighting between males is assumed to occur as stranded males are highly scarred. However, the distinctive tooth marks of the cookie-cutter shark and the orca have been seen on individuals as well. The stomach, which has unexplained multiple chambers, has been found to contain mainly squid, in addition to deep sea shrimp and viper fish (2).

There are no special conservation plans for this species, although trade in this species is limited by CITES around the world and prohibited in Europe.

Gervais' beaked whale has a prominent, slender beak with only two teeth which, whilst obvious in males, are not visible in females (5). These whales are dark grey to black on the back, fading to light grey or white on the underside. The head is relatively small with a slightly bulging forehead and the dorsal fin is situated towards the tail end of the back (2) (5).

Inhabits warm to tropical pelagic waters (2).

Although the first specimen of this species was found in the English Channel, it has only been found in the Atlantic Ocean since. The range has been deduced from stranding sites, and is possibly inaccurate, but is thought to stretch from New York to Trinidad on the western side of the Atlantic and from Ireland to Guinea Bissau on the eastern side (2).

Gervais' beaked whale is classified as Data Deficient (DD) on the IUCN Red List 2004 (1), and is listed on Appendix II of CITES (4). All cetaceans (whales and dolphins) are listed on Annex A of EU Council Regulation 338/97; they are therefore treated by the EU as if they are included in CITES Appendix I, so that commercial trade is prohibited.

The main threats to Gervais' beaked whale are accidental entanglement in gillnets and acoustic trauma following military noise pollution underwater (1). In the mid to late 1980s, several mass strandings were thought to be associated with naval activities around the Canary Islands. Later, between 1992 and 1998, 28 Gervais' beaked whales were stranded along the US coast between Florida and Massachusetts, followed by more mass strandings in September 2002 after NATO tested low frequency sonar (7).

· Gervais' beaked whales may be the most commonly sighted species of Mesoplodont off the U.S. Atlantic coast and the Gulf of Mexico. · Gervais' beaked whales are the most common species of the genus Mesoplodon to strand on the U.S. southeastern Atlantic coast.

· Gervais' beaked whales may be the most commonly sighted species of Mesoplodont off the U.S. Atlantic coast and the Gulf of Mexico. · Gervais' beaked whales are the most common species of the genus Mesoplodon to strand on the U.S. southeastern Atlantic coast.

Gervais' beaked whales are distributed throughout deep, warm waters of the central and north Atlantic Ocean. This species is thought to occur mostly north of the equator. Their range includes the English Channel, Europe, Canaries Islands, Western Africa, Brazil, Caribbean Sea, Gulf of Mexico, and the eastern north Atlantic (Jefferson et al. 2008). There are no known seasonal movements or migrations for this species.

Head Shape The small forehead is defined posteriorly by the indentation at blowhole. The melon merges seamlessly to the narrow, moderate length rostrum. The mouthline is relatively straight. Coloration Adult males are dark gray dorsally and medium gray ventrally with pectoral fins uniformly dark gray above and below. Scarring is often readily visible and appears to be more prevalent in adult males and can occur in round, oval or linear patterns. Oval scars may result from cookie cutter sharks and linear lines from conspecifics given the placement of mandibular teeth. Female pigmentation is similar to adult males, some adult females display a patch of white about 15 cm in diameter that extends from just anterior to the genital slit to a point just posterior to the anus. This patch has not been observed in males. Juveniles have a white belly. Size Adult body length ranges between 4.5 to 4.9 m. Recorded maximum body length for adult males and females is 4.8 m and 4.9, respectively. Length at birth is approximately 2.1 m. Most Likely Confused With: Mesoplodon bidens Mesoplodon mirus Ziphius cavirostris

Map representing approximate range of species.

Gervais' beaked whales prefer deep tropical, subtropical, and warm temperate waters of the Atlantic Ocean, but are occasionally found in colder temperate seas.

For management purposes, Gervais' beaked whales inhabiting U.S. waters have been divided into the Western North Atlantic stock and the Northern Gulf of Mexico stock. The estimated population for Mesoplodon spp. (Blainville's and Gervais' beaked whales) in the Northern Gulf of Mexico is 75-100 animals. This stock is considered "strategic" due to the uncertainty surrounding its status. No current population estimates are available for the Western North Atlantic stock of this species of beaked whale, but based on the number of strandings, they may be fairly common along the U.S. Atlantic coast. There are insufficient data to determine the population trends for this species.

Diagnostic features of the skull and mandible On the vertex of the dorsal skull the premaxillary bone extends forward of the nasal and frontal bones. Separates from Berardius and Ziphius. A sulcus (groove) running along the middle of the combined surfaces of the nasal bones so depresses their combined middle that it is the lateral portion of each nasal bone that reaches farthest forward on the vertex. Separates from Tasmacetus and Indopacetus. When the skull is upright and the long axis of the anterior half of the beak is horizontal, a horizontal plane transecting the summit of either maxillary prominence transects the mesethmoid bone. Separates from Hyperoodon. Tooth alveoli of mandible overlap the mandibular symphysis. Separates from Berardius, Ziphius, Tasmacetus, Indopacetus, Hyperoodon, M. bowdoini, M. carlhubbsi, M. densirostris, M. ginkgodens, M. hectori, M. layardi, M. mirus, M. perrini, M. peruvianus, M. stejnegeri, and M. traversi. Basirostral groove absent or present as a shallow groove that does not extend past the prominental notch. Separates from M. grayi. Jugal bone curves around anterior of maxillary. Separates from M. bidens.

Gervais' beaked whales, sometimes called the "Antillean" or "Gulf Stream beaked whale," are little known members of the beaked whale family (Ziphiidae) (Reeves et al. 2002). As adults, Gervais' beaked whales can reach estimated lengths of about 15-17 ft (4.6-5.2 m) and weigh at least 2,640 lbs (1200 kg). Females may be slightly larger than males. Males can be distinguished from females and juveniles by a pair of visible teeth that erupt from the front portion of the bottom jaw. Females and juveniles have teeth as well, but they remain hidden beneath the gum tissue of the mouth. The jawline is typically straight or slightly curved. Gervais' beaked whales have a relatively small to medium size body with a moderately long beak and an indistinct sloping "melon". They have a small, triangular, wide-based, slightly "falcate", "dorsal" fin located far down (about two-thirds) the animal's back. The coloration of the body is dark gray or bluish to black with a paler ventral side. Animals tend to become darker as they age. Mature males may also have linear scars from battles over females. This species of beaked whale is difficult to observe and identify at sea due to a low profile at the surface and a small, inconspicuous blow. Many species of beaked whales (especially those in the genus Mesoplodon) are very difficult to distinguish from one another (even when dead). At sea, they are challenging to observe and identify to the species level due to their cryptic, skittish behavior, a low profile, and a small, inconspicuous blow at the waters surface; therefore, much of the available characterization for beaked whales is to genus level only. Uncertainty regarding species identification of beaked whales often exists because of a lack of easily discernable or distinct physical characteristics. Gervais' beaked whales are usually found individually or in small closely associated social groups. While diving, they use suction to feed mainly on cephalopods (e.g., squid), mysid shrimp, and small fish in deep water. Females may become sexually mature at 15 ft (4.5 m). A sexually mature female will give birth to a single newborn calf that is about 7 ft (1.6-2.2 m) long and weighs about 176 lbs (80 kg). The estimated lifespan of this species is at least 27 years, but may be up to 48 years (Reeves et al. 2002).

The majority of stranding records for this species occur in the western North Atlantic along the eastern seaboard of the United States. Strandings have occurred to a lesser extent in the Caribbean and Gulf of Mexico. Despite its name, only a few specimens have stranded in European waters. Other eastern Atlantic stranding locations include the Canary Islands and Guinea-Bissau. South Atlantic Ocean records are reported from Namibia, Brazil and Ascension Island. It appears to prefer the deeper waters of the tropical and warm temperate Atlantic.

Gervais' beaked whales have been incidentally taken as bycatch in fishing gear, such as pound nets off the U.S. Atlantic coast and potentially in driftnets and gillnets. This species may be captured in the Caribbean Sea for food. This species of beaked whale may be sensitive to underwater sounds and anthropogenic noise. Anthropogenic noise levels in the world's oceans are an increasing habitat concern, particularly for deep-diving cetaceans like Gervais' beaked whales that use sound to feed, communicate, and navigate in the ocean.

Tooth position A single pair of teeth are positioned back from the apex of lower jaw about 1/3 the total length of the mouthline. The root base is square and not inclined in the jaw. Tooth exposure Erupted teeth in adult males are covered by gum tissue, with only the tip of tooth exposed. Teeth of females and juveniles do not erupt. Tooth shape In lateral profile, the anterior margin is relatively straight for a majority of its length and concave distally; the posterior tooth margin is weakly convex.

Gervais' beaked whales are dark grey above and lighter grey below. In young animals, the belly is white. The teeth of adult males are found one-third of the distance from the snout tip to the gape. They are visible outside the closed mouth. The mouthline is relatively straight. Can be confused with: Gervais' beaked whales are nearly impossible to distinguish at sea from other species of Mesoplodon.

Males attain lengths of at least 4.5 m, and adult females reach at least 5.2 m. Weights of at least 1 200 kg are attained. Newborns are about 2.1 m in length.

The favoured habitat of Gervais' beaked whales appears to be warm temperate and tropical waters. Like other members of the genus, they are known to feed on squid.

There is a record of 1 being taken in a net off New Jersey, and others may have been taken in Caribbean small cetacean fisheries. IUCN: Insufficiently known.

Gervais's beaked whale (Mesoplodon europaeus), sometimes known as the Antillean beaked whale, Gulf Stream beaked whale, or European beaked whale (from which its scientific name is derived) is the most frequently stranding type of mesoplodont whale off the coast of North America. It has also stranded off South America and Africa.

Warm-temperate to tropical waters of Atlantic.

oceanic

Data Deficient (DD)