Manetee marine mammal

Manetee marine mammal

Introduction
In waters near our shores, strange and melodic sounds can be heard during certain times of the year. It is the singing of whales that visit the island. Some of them are born here and return when they are about to give birth.

Marine mammals are not well known in Puerto Rico because they only appear occasionally and they can rarely be seen. The best known marine mammals in Puerto Rico are manatees, because they live closer to the coast and they visit river mouths. Other marine mammals in the Caribbean are whales, dolphins, and sea lions. It is feared that sea lions may have become extinct.

Unlike fish, mammals are characterized by being: warm-blooded, they breathe through lungs, have skin covered with hair, internal fertilization and development of offspring, mammary glands, and a relatively-developed brain. Marine mammals hold their breath for long periods of time by plugging their ears while they are submerged. Some of these characteristics have been modified to adapt to aquatic life. For example, their limbs have been developed for swimming and whales have little or no hair when they reach adulthood.

Many of these species are endangered. Therefore, their conservation is essential and generates greater interest in our aquatic natural resources.

The Department of Natural Resources (DNR), Caribbean Stranding Network, “Sea Grant” Program, and the Marine Sciences Department of the University of Puerto Rico, as well as other foreign organizations through a specialized staff, have focused their efforts toward research for better understanding these organisms.

Whales, dolphins, sea lions, and manatees are an integral part of our natural heritage. Therefore, they must be studied and fully protected.

Sirenians
The West Indian manatee, Trichechus manatus, is found from southeastern United States to the northwestern coast of Brazil. Two subspecies are identified: Florida manatees (Trichechus manatus latirostris), found in the southeast of the United States, and West Indian manatee (Trichechus manatus manatus), found in the rest of the Caribbean, including Puerto Rico.

The adult manatee can reach a length of 4.3 meters and can weigh more than 1,600 kg. Females tend to be longer and heavier than males. The color of adults ranges from gray to brown; offspring are dark-colored at birth, and their color lightens after the first month.

Manatees are primarily herbivores. They feed on a variety of submerged, floating, and emerging aquatic plants. In Puerto Rico, manatees feed mostly on marine herbs such as are thalassia and syringodium. Adults consume approximately between 8 and 11 percent of their body weight per day. Their peculiarity of being the only herbivore marine mammal gives them a major ecological niche. Manatees serve as biological agents for the control of aquatic vegetation and can influence other levels of aquatic ecosystems such as distribution, production of the plants they consume, and encouraging nutrient cycling.

Freshwater, estuarine, and marine ecosystems may serve as habitat for the West Indian manatee, which may move freely between areas of extreme changes in salinity. Manatees have no specific mating season; therefore, offspring may be born throughout the year. They have a low reproductive rate: their gestation period is about 13 months and have a single offspring every 3 to 5 years. These reproductive characteristics make this species highly vulnerable. Offspring depend on their mothers for a minimum of two years, but remain together until they are four years old, not just for food but to learn migration routes and feeding sites.

In Puerto Rico, manatees are found around the entire island, except in the islands of Desecheo and Mona. They are mostly seen from the town of Dorado to the town of Mayagüez, but especially in the area of Fajardo, Ceiba, Jobos Bay in Guayama and at the mouth of the Rio Guanajibo in Mayagüez. The manatee is considered the most endangered marine mammal in the entire area of the northeastern Caribbean. Studies conducted at the end of the 1970s and in 1984 suggest that only between 63 and 200 manatees remain in Puerto Rico. Its endangered status is directly related to human contact, as evidenced by excessive hunting of the species and deaths due to accidents with fast boats.

 

Humpback whale seen off the coast of Rincón

Humpback whale seen off the coast of Rincón

The group of Mysticeti cetaceans includes large whales. These vary in size from 4.5 to 33.5 meters. Mysticeti are characterized by having a few hundred keratin plates instead of teeth. These are used to filter their food, which consists mostly of small fish and invertebrates such as krill and copepods. Mysticeti whales are also characterized by having two blowholes. There are 11 species of mysticeti cetaceans in the world, of which 5 species are found in Puerto Rico:

Fin Whale (Balaenoptera physalus) – Fin whales are characterized by asymmetrical coloration: they are dark on the right side of their throat and part of their chest; they are white on the left side. This species reaches 27 meters; the female is larger than the male. Its body is thin, its belly is white, and its back is usually dark. Dorsal fins measure 60 cm tall. They are found in oceans worldwide. They feed on pelagic crustaceans, codfish, and other fish. Their gestation period is 11 to 12 months. During the spring and summer, these whales remain in warm waters, while in autumn and winter they migrate to tropical waters to mate and give birth to their offspring. Usually, they travel in groups of 6 to 7 whales. They have sometimes been seen alone and in pairs. In Puerto Rico, they have been seen south of Ponce.

Sei Whale (Balaenoptera boreal) – This species exhibits considerable variations in coloring. Their backs vary from dark gray to black with bluish areas that spread to the sides. Their chest is lighter with pink tones. They measure between 14 and 18 meters; females are larger than males. Their body is elongated with a prominent dorsal fin that measures up to 60 cm tall. The head has a single ridge on top, and a gray right lower lip is characteristic of this species. It inhabits all seas especially in temperate areas, migrating to cooler areas during the summer to feed. They are usually found in groups of 2 to 5 individuals. It is possibly the fastest of the great whales, reaching speeds of approximately 30 miles per hour. Their food consists of small fish and crustaceans.

Bryde’s Whale (Balaenoptera edeni) – This is one of the few mysticeti species that do not migrate to the poles in the summer. They mainly live in tropical and subtropical areas. Its head is elongated and has three ridges on top. The three ridges are positioned as follow: one in the center that reaches the blowhole and one on each side. They measure between 12 and 14 meters, and in general, females are larger than the males. Their body is elongated and thin, their back is dark-colored and their chest is lighter. They live in all tropical oceans including the Caribbean. Their food consists of sardines and anchovies. The gestation period is relatively longer than in other whales, almost a year.

Minke Whale (Balaenoptera acutorostrata) – This whale is one of the smallest in size among the mysticeti. The average size is 6 to 9 meters long. They are characterized by a diagonal stripe or a white spot on the pectoral fins. Their backs are black and their chests are white. Most live in temperate waters, specifically in the southern hemisphere or to the north of Antarctica. However, they have been sighted in the Caribbean and Puerto Rico, specifically in the Mona Passage and east of the Virgin Islands. They travel in groups of 2 to 3 whales and sometimes solitary animals have been seen. They feed on codfish, krill, and fish. Their gestation period is 10 to 11 months.

Humpback Whale (Megaptera novaeangliae) – The nodules on the head, long pectoral fins along with the patterns of white and black on the chest area are characteristic of the species. They vary in size from 12 to 16 meters; females are larger than males. They can reach a weight of 40 tons as adults. The body is robust and black; it becomes narrow past the hump and dorsal fin. Pectoral fins are a third of the total length of the body and are mostly white.

Humpback Whales migrate to our shores in late November and stay until the end of April in one of four sandbars in the area north of the Caribbean Sea. Two of these sandbars are located north of the Dominican Republic, one north of the Virgin Islands and the other one is close to the Borinquen sandbar between Aguadilla and Isabela. Many times, whales are seen traveling from one sandbar to another. These cetaceans have adjusted their migratory habits to take advantage of two completely different habitats and use them for different purposes: feeding and reproducing. The warm waters of New England and Canada serve these whales as feeding sites during the summer. They feed on small fish such as herring and eel. On the other hand, the tropical waters of the Caribbean serve the humpback as habitat during the winter (November to April) for mating and giving birth to their young.

Humpback Whales have acquired a high degree of brain development and this is seen in their social behavior. To communicate, humpbacks jump, splash their tail fin and pectoral fins and make a very complex sounds called songs. Males have the ability to produce these sounds in patterns, which are repeated over and over. That is why they are called songs, like bird songs. Unlike birds, humpback melodies are extremely long (6 to 30 minutes) and change from season to season. In the Borinquen sandbar, songs that were heard in the 1980s are different from those heard today. Also, songs heard in Puerto Rico are different from those by the same species in Hawaii. It is believed that the variety of songs in the same population helps females choose a male to mate with.

Dolphin on Jobos coast

Dolphin on Jobos coast

The group of Odontocete Cetaceans generally includes smaller whales, with the exception of the sperm whale —which reaches 18 meters in length— dolphins, and porpoises. Normally, these whales, also known as toothed cetaceans, range in size from 1.2 to 13 meters. Odontocetes are characterized by having from 2 to 260 teeth. They are only used to grab their food, which consists mostly of small fish and shellfish such as squid and octopus. Odontocete whales, contrary to mysticeti, only have one blowhole. There are 67 species of odontocete cetaceans in the world of which the following 17 are found in Puerto Rico:

Bottlenose Dolphin (Tursiops truncatus) – Star of the film and television series “Flipper”, the bottlenose dolphin is the best known cetacean. Its relatively short snout, with a noticeable connection between the forehead (known as “melon”) and the snout and its tall dorsal fin, curved and wide at the base, distinguish this species. Its body is robust, grey on the back and lighter in the underside. Two dark lines go from the eyes to the face. It can measure up to 3.9 meters in length but the average length is 2.4 meters. They are found in all tropical and temperate waters in the world, some near the coast, while others inhabit offshore. They have group structures divided by age and sex. Groups vary on the number of individuals depending on the time of day; there are small groups in the morning and increase in number in the evening. Sometimes the group size increases as water becomes deeper. They feed mainly on fish, squid, and crustaceans. They are is commonly seen in Puerto Rican waters; they are frequently sighted from boats and from the coast throughout the year.

Atlantic Spotted Dolphin (Stenella frontalis) – These dolphins live in tropical waters of the Atlantic Ocean. They are characterized by a few spots or stains on their robust bodies. Their snout is delimited by an abrupt connection with the melon. In addition, they have a curved dorsal fin. Their food consists mainly of fish and squid. In Puerto Rico and the Caribbean this species is very common; it is seen all over Puerto Rico.

Spinner Dolphin (Stenella longirostris) – It is characterized by its high acrobatic jumps. It differs from other dolphins because it is smaller in size, has a long snout, and males have a triangular dorsal fin. It measures between 1.5 and 2.1 meters and males are usually larger than females. Its body is robust and it has a very long snout. Its back is dark, its sides are grayish, and its belly is white. Its pectoral fins are dark and have a colored line that connects them with a dark patch in the eye. They travel in large groups in pelagic waters (ocean waters). In Puerto Rico they have been seen all around the island, especially in areas near the shore.

Striped Dolphin (stenella coeruleoalba) – The color of this dolphin species is very peculiar. It has a pale stripe that goes from its side to the base of the dorsal fin; a black spot around the eye from where a black line extends toward the pectoral fins, and from the eye extending on its side reaching the lower part of the caudal fin. Its back and pectoral fins are bluish gray; its belly is white. It can grow up to 2.6 meters in length. It travels in large groups that can have hundreds of individuals. It feeds on fish, shrimp, and squid. It has never been seen in Puerto Rico, but it is common in the Caribbean. There is a stranding report in the neighboring island of St. Croix.

Common Dolphin (Delphinus delphis) – The common dolphin inhabits tropical waters in all oceans of the world. It measures about 2.4 meters long. It has a very distinctive color pattern in the shape of an “8” on its side, its front is dark yellow or brown, and its back is gray. Its back forms a black layer. This dolphin has a well-defined and long snout. These dolphins swim in large schools of 40 or more individuals. They feed on fish, squid, and anchovies. The gestation period is between 10 and 11 months. In Puerto Rico, they have been sighted in pelagic waters, in the Mona Passage, and the south coast.

Rissos Dolphin (Grampus griseus) – This species measures about 3 to 4 meters long. It is white or silver gray except the dorsal fin which is dark, and it has a stain around the eye. Its body is scratched; adult animals have more scars. These are caused by teeth of other dolphins during games or fights for dominance. Its body is robust. It has no snout and its head is round in the shape of a cauldron. It travels in groups of 12 or less. It is common in tropical waters, but because it is pelagic, there are few sightings. In Puerto Rico it has been reported on rare occasions, the last time was on the island of Vieques.

Short-finned Pilot Whales (Globicephala macrorhynchus) – This mammal is also called a pilot whale. Its body is robust, and its bulbous head is in the shape of a cauldron. It is black except for one white patch in the shape of an anchor in the belly. The dorsal fin is short and wide at the base. Pectoral fins are narrow. Females reach 4 meters in length; males can reach the 5.5 meters. They live in all temperate and tropical waters of the world, coastal and offshore. In Puerto Rico and the Caribbean they are very common; they have been seen in our waters near the shore. There are reports of these dolphins near the islands of Mona and Vieques, San Juan, and Arecibo, among others. They feed on fish and squid.

Orca (Orcinus orca) – The orca, or killer whale, is easily recognized for its black color and tall dorsal fin which in males may reach up to 1.8 meters. Patches located above and behind the eye, the flank and belly are white which clearly stand out on the shiny black body. Males can reach 9.7 meters in length and females reach 8.5 meters. They can weigh 7,200 kg. They are found in all oceans, both in coastal and pelagic waters. In Puerto Rico they have been sighted in the Mona Passage, near the island of Culebra, and in the passage between St. Thomas and St. Croix. They travel in groups of 5 to 20 individuals. Each group is very close and has its own dialect sound. They feed on fish and other marine mammals such as seals, whales, and dolphins, in addition to feeding on squid, penguins, seabirds, and sea turtles. They are well known for adapting easily to captivity and being the stars of marine shows at aquariums.

False Killer Whale (Pseudorca crassidens) – The False Killer Whale is completely black except for one white spot in the shape of an anchor on its chest. The pectoral fins are folded and the dorsal fin is relatively tall. Males grow up to 5.4 meters in length; females could reach up to 4.8 meters. The species could weigh up to 2,300 kg. Its body is thin and long. It inhabits all temperate and tropical waters, including the Caribbean and Puerto Rico. In Puerto Rico, it has been reported of the island of Culebra. The species is highly gregarious, traveling in groups of up to 50 individuals. At times they have been seen traveling with bottlenose dolphins. Their diet consists primarily of squid, pelagic fish, and occasionally, dolphins.

Pygmy Killer Whale (Feresa attenuata) – This dolphin measures about 2.3 meters. It is black except for the mouth and its belly is white. Its body is thin, its head is round, and it has no snout. They live in tropical and subtropical waters. They travel in groups of 5 to 10 individuals. The knowledge we have about their food is very limited. This species has not been seen in Puerto Rico so far, but given its presence in the Caribbean it should be found in our waters.

Melon-headed Whale (Peponocephala electra) – These dolphins are very similar to the pygmy killer whale. They measure between 1.8 and 2.4 meters. They have numerous small teeth. These mammals live in tropical and subtropical waters in all oceans. They are black -except for the genitals, anal area, and mouth which are white. Their food consists of fish. Like the Pygmy Killer Whale, they are found in the Caribbean, but so far they have not been sighted in Puerto Rican waters.

Antillian or Gervais` Beaked Whale (Mesoplodon europaeus) – Like all beaked whales, it only has two teeth in the lower jaw, but these teeth can only be seen in males. These can measure 5 meters long. It is dark gray on the back and light gray in the abdomen. Its body is robust with a small fin in the last third of the body length. They have a slight melon on the head, which holds the snout. They feed on squid and probably on deep-water shrimp. They are very common in the Caribbean and one recently beached in St. Croix in the Virgin Islands. There are no reports of them having been seen in Puerto Rico but they are most likely present in our waters.

Dense-beaked Whale (Mesoplodon densirostris) – Also known as Blainville’s beaked whale, it measures about 4.5 meters long. It is characterized by having two teeth that measure approximately 15 cm long and are located in the center of the lower jaw. The snout is distinctive for this species: it is curved. Its jaw bone is very heavy and this species has one of the densest bones of any animal that has ever existed. Its body is robust and has a small dorsal fin in the last third of the body length. It is dark gray with light areas along the belly. These whales are found in all oceans of the world, specifically in waters ranging from tropical to temperate. They feed on squid. The reports of this kind are rare in the Caribbean and one of only two reports of this kind in the Caribbean was in Puerto Rico.

Cuvier`s Beaked Whale (Ziphius cavirostris) – also known as baby face whale or goose-beaked whale. The male has a white head and two small teeth in the lower jaw that are visible even if its mouth is closed. The head forms a slight slope with its small snout. Adult females measure 5.7 to 6.9 meters and adult males 5.4 to 6.6 meters. Its body is robust and light gray. The head and snout are small compared to other species of beaked whales. It feeds on deep-water fish and crabs. It lives in tropical waters, especially in pelagic areas. In Puerto Rico and the Caribbean, beaked whales are commonly beached in the island of Vieques, La Parguera, Patillas, Salinas, Fajardo, and Caja de Muertos.

Pygmy Sperm Whale (Kogia breviceps) – Pygmy sperm whales measure from 2.7 to 3.3 meters long and are dark gray; others are bluish gray on the back and light gray on the belly. The shape of the jaw gives it the appearance of a shark. They have a light coloration behind the eye that looks like a shark’s gill. They feed mostly on deep-water fish and crabs. They are pelagic, traveling in groups of 1 to 7 individuals. They are found in tropical waters around the world. There is a group of pygmy sperm whales that sleeps with heads towards the surface and tails in the water. The few reports of this kind in Puerto Rico are all of whales that have become beached.

Dwarf Sperm whale (Kogia simus) – The Dwarf sperm whale is very similar to the pygmy sperm whale. The difference is that it is a bit smaller (2.1 to 2.7 meters) and the dorsal fin is tall, located at the midpoint of the back, similar to that of a dolphin. Like all sperm whales, its head is asymmetrical. These are pelagic whales and feed on deep sea crustaceans. Although found in the Caribbean, they have not been reported in Puerto Rican waters. However, their presence would be expected.

Sperm Whale (Physeter catodon) – Became famous in the story of Moby Dick. Its head is elongated and square and measures one third of its total size. Its dorsal fin is small and forms a triangular ridge. Its skin is wrinkled. Males of this species measure up to 18 meters; females barely reach 11 meters. It has 25 teeth on each side of its lower jaw, which is thin and long. They are brown or dark gray and are lighter on the forehead. They feed on octopus, giant squid, and different species of fish. Females of this species travel in groups called harems, while young ones travel in groups called “bachelor schools”. Adult males are solitary. The gestation period for females is 15 months. This species inhabits all the seas of the world, including the Caribbean. Sperm whales approach our waters during the winter months when harems meet solitary males. In Puerto Rico they have been sighted around all over the island, especially near the shores.

Oil`s spill from the Morris SJ Bergman

Oil`s spill from the Morris SJ Bergman

Beaching occurs when marine mammals, living or dead, are found stranded or sick on the shore. There are two kinds of beaching: solitary and in herds. Hundreds of beachings and deaths have been reported in the Caribbean in recent years. However, many other deaths have gone unnoticed. The exact causes of beaching of marine mammals are unknown. Although there are some explanations that seek to clarify this phenomenon, they are incomplete. Some of the theories that have been proposed include: diseases, parasitic infections, confusion due to depth configuration in some beaches and malfunctioning echolocation (sound) system of dolphins. The strong social ties that exist between these animals cause other dolphins or whales that are in perfect health to accompany them to the beach or answer the call for help from another animal that is sick or disoriented.

Beaching also occurs because of human intervention: impact with boats, tangling, ingesting trash from the water such as balloons or plastic bags, or illegal hunting. There are still some Caribbean countries that make illegal use of marine mammal products such as: meat, fat, bones, or oils. This directly affects the survival of these species, many of which are endangered. There are alternative or synthetic products that can be used to substitute products from whales, dolphins, or manatees, used traditionally or commercially. Scientific research and the immediate attention to beaching cases are vital for protecting and conserving these species.

Each beaching is unique, and action to be taken depends on the circumstances in which it occurs. If you were to find a marine mammal stranded on the shore, follow these steps and write down the following information:
1-See if the animal is alive or dead,
2-Describe the animal briefly, if possible, identify the species. Report where the beaching occurred, the number of stranded animals, and what happened.
3-Notify the beaching to the Caribbean Stranding Network (899-2048) and provide your name and phone number. The Network will say what first aid action is needed and will activate the work team and notify relevant government agencies.
4-You can also notify the beaching to the Cuerpo de Vigilantes of the Department of Natural Resources, Tel: 725-1202/1723-5137 / 721-5720.

Protection of marine mammals

In most Caribbean nations it is illegal to hunt marine mammals or use products derived from them. In the United States and its territories, for example, the Marine Mammal Protection Act of 1972 and the Endangered Species Act of 1973 strictly prohibit hunting, unauthorized use and intervention with whales, dolphins, manatees, dead or alive. In Puerto Rico, all marine mammals are protected under the Fisheries Act of 1938, the Wildlife Act of 1976 and the Reglamento para Regir el Manejo de las Especies Vulnerables o en Peligro de Extinción (Regulations for Handling Vulnerable and Endangered Species) of the Department of Natural Resources of 1985.
You can help preserve this resource, heritage of Puerto Rico, noting the following guidelines:
1-If you drive a boat: when you see serials indicating the presence of marine mammals, slow down to a minimum so that you do not make waves.
2-If diving, look at the mammals but do not touch them. Take
photographs if you wish but do not deliberately approach the animal.
3-If fishing, do not discard entangled fish threads in the water. Marine mammals often get injured by floating hooks and nylon threads.
4-If you are going to the beach, do not discard plastic waste in the sand, including bags, balloons, or plastic six-pack rings on soda cans. Dolphins have died from ingesting these plastics.
5-If you have friends who enjoy water sports, talk to them about these harmless creatures. They would not attack even if their lives depended on it.

Thanks
We extend our sincerest thanks to biology students Darien Lopez Ocasio, Dianne Martinez, and Damaris De Jesus; and biologist Fernando Gonzalez for collecting some of the data on the species mentioned here.

Author: Grupo Editorial EPRL
Published: August 27, 2014.

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