Gervais' Beaked Whale

· 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.