A couple weeks ago, I told you guys two dolphins that many thought not to be a member of the Delphinidae family, the Orca, and the Short and Long-Finned Pilot Whale. As usual, I will provide a few facts and a picture about each dolphin.
Here are a few more:
The first is the Melon Headed Whale:
Genus & Species: Peponocephala electra
The melon-headed whale, also known as the electra dolphin, little killer whale, melonhead whale and many-toothed blackfish, is a large dolphin with an elongated body. The head is rounded, with a slight beak detectable in the smaller specimens. The mouth angles upward towards the eyes and the sides of the face are pressed in, giving it a triangular look when seen from the top. They look much like pygmy killer whales, but are distinguished by them from the shape of the head and the longer, pointed flippers. They have many teeth, 20-26 pairs per jaw, unlike other dolphins, which have fewer than 15 pairs per jaw. The dorsal fin is tall (12in , 30 cm) and is pointed at the tip. It is located at the center of the back. The tail flukes are broad.
Melon-headed whales are black or dark grey in colour. A dark dorsal cap extends from the head and widens below the dorsal fin, narrowing again at the flanks. The lips lack pigment and appear to be white, pink or grey. A dark grey anchor shape is located on the underside and extends from the flippers towards the throat. There is a light stripe that extends from the blowhole to the snout tip and a white urogenital patch on the underside. The head has a dark patch shaped almost like a mask that extends from an eye spot to cover most of the head.
Melon-headed whales reach a maximum length of 9 ft and a maximum weight of 595 lbs. The males have slightly longer flippers and dorsal fins, and broader tail flukes, than females. They communicate with clicks and whistles.
Melon-headed whales are found in tropical and subtropical waters that are deep and in the open ocean. They are seen along most of Africa but do not travel farther north than Morocco. There are no reports of any in the Red or Mediterranean Seas. They are found in the eastern Atlantic, Caribbean, central Pacific and Indian Oceans. They have stranded on Australia, Vanuata, Seychelles, Japan, Brazil, and Costa Rica. One specimen has been stranded in Texas. They are common in the Gulf of Mexico but were not known to live there until 1990. They are not thought to migrate.
Melon-headed whales feed on small fish, large squid, and shrimp. They are very aggressive and have been known to attack small dolphins escaping from purse seines.
Little is known about the breeding habits of the melon-headed whale. The males reach sexual maturity at lengths of 99.2 inches and females at 92 inches. The gestation period is thought to be 12 months. One calf is born from August to December in the Southern Hemisphere and April to June around the Phillippines. Calves are 3 ft long at birth.
Melon-headed whales have no problem with over-collection for amusement parks as they are too aggressive to be handled. However, many are killed in purse seines and drift nets each year. They are hunted off the island of St. Vincent and are harpooned off Sri Lanka, Indonesia, and the Phillippines.
Melon-headed whales are found in pods ranging from 100-2000 individuals. They are found in association with Fraser’s dolphins and are thought to be the more dominant of the two. They are also seen with spinner and spotted dolphins. They can swim at high speeds and will often bow- ride ships.
The melon-headed whale is in a genus by itself, although prior to 1960 it was in the Lagenorhynchus genus with the dusky dolphin and the Atlantic white-sided dolphin. It is considered to be an “outcast” member of the blackfish group, a term used to describe other members of the subfamily Globicephalinae. These include the killer, pygmy killer, false killer, short-finned pilot and long-finned pilot whales.
The Second is the False Killer Whale:
False killer whales are large members of the dolphin family. Females reach lengths of 15 feet (4.5 m), while males are almost 20 feet (6 m). In adulthood, false killer whales can weigh approximately 1500 pounds (700 kg).
They have a small conical head without a beak. Their dorsal fin is tall and their flippers (pectoral fins) have a distinctive hump or bulge in the middle of the front edge. False killer whales have dark coloration except for some lighter patches near the throat and middle chest. Their body shape is more slender than other large delphinids.
False killer whales’ breeding season lasts several months. Gestation periods range from 14 to 16 months and lactation occurs for one and a half to two years. False killer whales have low reproduction rates with calving intervals of approximately seven years. Maturity occurs at around 12 years of age and maximum longevity is 63 years.
These whales are gregarious and form strong social bonds. They are usually found in groups of ten to twenty that belong to much larger groups of up to 40 individuals in Hawai’i and 100 individuals elsewhere. They are known to “strand” in large groups as well. False killers are also found with other cetaceans, most notably bottlenose dolphins. To increase success of finding prey, these whales travel in a broad band that can be up to several miles wide.
Food sharing has been documented between individual false killer whales. They feed during the day and at night on fishes and cephalopods, and they are known to attack smaller dolphins that are involved in the tuna purse-seine fishery in the Pacific Ocean.
They prefer tropical to temperate waters that are deeper than 3,300 feet (1000 m).
False killer whales occur in the U.S. in Hawaii, along the entire West Coast, and from the Mid-Atlantic coastal states south. The species can also be found in all tropical and temperate oceans worldwide.
Currently, the Hawaii stock is estimated at 270 whales and the Northern Gulf of Mexico stock at 1040 whales. There are not enough data to estimate population trends for these stocks. See below for links to the most recent stock assessments for the U.S. populations.
False killer whales are taken as bycatch or interact with a number of fisheries, such as the Hawaii Longline fishery and bottomfish fishery off the Northwestern Hawaiian Islands. They are also hunted and killed opportunistically in Indonesia, Japan, and the West Indies.
False killer whales are classified as Lower Risk – Conservation Dependent on the IUCN Redlist . NMFS funds several research studies on life history and stock structure of false killer whales in Hawaii.
In January 2010, NOAA established a new Take Reduction Team to reduce bycatch of Hawaiian false killer whales in longline fisheries.
This species is protected under the Marine Mammal Protection Act of 1972 as amended.
In 2010, NMFS initiated a status review in response to a petition to list the insular population of Hawaiian
The Third is the Tucuxi:
Description & Behavior
The tucuxi (pronounced too-koo-shi), Sotalia fluviatilis (Gervais and Deville, 1853), aka gray dolphin and gray river dolphin, resembles a bottlenose dolphin except that it is slightly smaller in size. There are 2 subspecies of the Tucuxi: 1) Sotalia fluviatilis fluviatilis (Gervais and Deville, 1853) is the freshwater species and, 2) Sotalia fluviatilis guianensis (P.-J. van Bénéden, 1864) is the marine species. The marine tucuxi reaches 2.1-2.2 m in length, and the riverine tucuxi reaches 1.5 m in length. They are light gray to blue-gray in color on the dorsal side, and light gray to pink on the ventral side. The flanks are slightly lighter than the dorsal side between the flippers and dorsal fin. The dorsal fin is triangular and may be slightly hooked at the tip. The tucuxi has a moderately slender and long beak.
The marine and riverine tucuxis have similar social behaviors. Marine tucuxis can be found in groups of up to 30 individuals. They are most commonly found in pairs in the Baia de Guanabara and Cananéia, although group size varies by time of day and activity. Juvenile marine tucuxis are usually observed in small groups of 3 that include the calf and 2 adults or 4 (2 calves and 2 adults). Riverine tucuxis are found in groups of 1-6 in more than half of the observations recorded, and in groups of up to 9 individuals on occasion. The composition of the riverine groups is unknown, however groups consisting of 1 female with 1 male calf, and 1 pregnant female with an 1 juvenile female have been recorded. The average group size in the Upper Amazon River is about 3.9 individuals.
World Range & Habitat
The tucuxi, Sotalia fluviatilis, is found in both fresh and saltwater. The coastal range of S. f. guianensis extends from Florianopolis, Brazil, north into the Caribbean Sea as far as Panama. One individual was reported near Nicaragua, north of the mouth of the Layasiksa River on the west side of Waunta Lagoon (13°40’N). Riverine tucuxis, S. f. fluviatilis are found in waters below an elevation of about 100 m in the Orinoco and Amazon rivers, primarily in estuaries and bays, and in deep river channels or flood-plain lakes. The separation of S. f. fluviatilis into subspecies is supported by data on genetic variation between the marine and riverine Sotalia in Brazilian waters.
Population data for the tucuxi is scarce, however it appears to be relatively abundant throughout its range. The population data available is from small geographic areas such as: the mouth of the Magdalena river in Colombia where an estimated 100-400 dolphins were counted, the Gulf of Cispata near San Antero, Colombia where they were abundant, Suriname where they were common in the mouths of the larger rivers, and in Guyana where they were reported as “frequent” in the lower reaches and mouth of the Essequibo river. They have also been reported as common in the Baia de Guanabara near Rio de Janeiro, Brazil where an estimated population of 418 individuals in about 109 groups was reported, although this conflicts with more recent data that estimates only 69-75 individuals in that region. The tucuxi population near Cananéia Island was estimated at 2,829. Population density estimates in the Amazon drainage area show an average density of approximately 1.1 dolphins per km of river between Manaus and Tefé in the Solimöes river. In the Iquitos area, 62 Sotalia were reported over a 36 hr observation period. Sotalia were frequently encountered in the Samiria river and its tributary the Santa Helena river, and in Colombia in the Loretoyacu river, the Tarapoto river at the El Correo lake system, and in the lower region of the Orinoco river. In another survey conducted in 1993, a population estimate for the tucuxi along 120 km of the Amazon river bordering Colombia, Peru, and Brazil was about 409 tucuxi in the study area. Population density estimates calculated at the number of Sotalia per square mile put the highest number in lakes (8.6), followed by areas along main river banks (2.8), and around islands (2.0).
Sotalia fluviatilisis prefer shallow protected estuarine waters or bays near junctions of rivers and channels. In the Baia de Guanabara ( Rio de Janeiro), they inhabit channels at least 25 m deep and avoid areas with less than 6 m of water. They are not, however, limited by physical factors such as visibility and pH as they are found in all types of water in the Amazon, other than rapids and fast-flowing turbulent water.
Marine Sotalia may travel up to 130 km or more upriver. They are thought to have a specific home range, although the area covered may be large given the distances between the estuaries and protected bays they inhabit. In one study, individual Sotalia (identified by natural marks) remained in the same area for over 1 year, and in another study 2 tagged tucuxi were were found within 5 km of the original tagging site up to 1 year later.
Daily rhythms are apparent in the movement of the tucuxi as well. Studies in the Amazon indicated increased activity between 9-10:00 am following movement into lakes from rivers during the early morning hours before 9:00 am. In another study, Sotalia entered the Bahía de Guanabara between 6-8:00 am and left between 1-6:00 pm, although they rarely left the same day they entered. These movements may be related to preferred resting and feeding areas.
Marine tucuxi, S. f. guianensis, from the southeast Brazil region feed on a diet of fish such as herring, drums, croakers, and cephalopods. In Santa Catarina they are known to feed on anchovies.
In the Amazon region, rivierine tucuxi, S. f. fluviatilis feed on at least 28 species of fish belonging to 11 families including: tetras, drums, croakers, and catfishes.
Riverine tucuxi, S. f. fluviatilis, in Brazil begin calving in October and November during the low water period. Little else is known of the species’ reproduction.
Conservation Status/Additional Comments
Tucuxi, Sotalia fluviatilis, are not hunted commercially. Riverine tucuxi have been protected by the superstitions of fishermen from Colombia to southern Brazil, and in the Amazon. Small numbers of marine tucuxi are caught for shark bait or shrimp traps, and it is thought that a small number may be hunted for sale in the Asian aphrodisiac market for the eyes and genitalia.
Entanglement ( bycatch) in fishing gear threatens both species of Sotalia, particularly gillnets , seine nets, and shrimp and fish traps. In one study, 938 tucuxis were taken in drift nets from the port of Arapiranga during the summer of 1996 followed by another 125 during the winter. These data were collected from fishermen in the port who collected the carcasses.
Fortunately, these dolphins do not compete with humans for the same fish as the diet of tucuxis largely consists of noncommercial species.
Like other river dolphin species, damming of rivers for hydroelectric projects threatens the habitat of the tucuxi. These dams can cut off populations from one another thereby restricting the gene flow and they can also prevent migratory fish species preferred by tucuxi from reaching their reservoirs. Furthermore, dams built on freshwater rivers that empty into the sea may affect primary and secondary productivity in the estuaries and reduce the feeding potential in these areas.
Similarly, pollution from industrial and agricultural activities threatens the tucuxi through habitat destruction and contamination of the food chain. The Baia de Guanabara in Rio de Janiero and Santos in São Paulo are polluted with toxins such as heavy metals. Insecticides made with chemicals banned in other regions (such as the US) are still common in South America.
Recommendations by a International Whaling Commission (IWC) sub-committee in 2000 for the protection of the tucuxi include: 1) research to detect trends in abundance in a range of regions and habitats, 2) research on mortality due to bycatch associated with different fishing methods, and 3) research on the range of the 2 subspecies in areas such as the Orinoco and Amazon estuaries.
National legislation exists to protect the tucuxi in Brazil, Peru, and Colombia. The species is indirectly protected in Ecuador, Venezuela, Guyana, and French Guiana. In the majority of countries within the range, nature reserves may protect the habitat.
I hope you learned a few things. I did putting this together. Thanks