Dugongs and Manatees: The Mythical Mermaids?

Mermaids. The mythical creature with great seductive powers. The femme fatale, with the head and upper body of a female human and the tail of a fish.

As long as there have been seafarers, it seems, there have been mermaids to mess the minds of these intimacy deprived sailors.  

The male equivalent of the mermaid is the merman. The male and the female collectively are sometimes referred to as merfolk or merpeople.

Do these seductive creatures really exist?  Maybe in form of Dugongs and Manatees which have breasts and suckle their young ones above water, in human fashion. 

When dugongs surface to breathe, they sometimes “stand” on their tail with their head above water. With poor lighting, imaginations and of course dry spell, to the sailor this looked like the head of a beautiful seductive lady..

Dugong also known as sea cow, is known as Nguva in Swahili. It has a simple scientific name: Dugong dudong. They are found tropical waters from East Africa to Vanuatu, about 26 degrees both north and south of equator. They are only found in the salty waters of the oceans. They are the only exclusively marine mammals that are herbivorous. In Kenya Dugongs have been sighted in Kiunga Marine Park. 

          In serach of the dugongs in India Ocean

On the other hand, Manatees are found in shallow, slow moving rivers, estuaries, saltwater bays, canals and oceans. They live in both freshwaters and saltwaters of the Caribbean Sea, Gulf of Mexico, Amazon basin and West Africa. 

Even though the dugongs and manatees are marine mammals, they are more closely related to elephants than dolphins or whales. 

The key difference between the dugongs and manatees are: 

Tail shape

Dugong tails have flukes made up of two separate lobes joined together in the middle and look similar to whale or dolphin tales. 

Manatees have a horizontal paddle-shaped tail with only one lobe to move up and down when the animal swims.

Mouth shape

Dugongs have a longer, broad, short trunk-like snout and agile upper lip used to munch on seagrass. It faces downward with a slit for a mouth, useful for feeding off the ocean floor. 

Manatees have a divided upper lip and a shorter snout.  They are able to both gather food and feed on plants growing at or near the surface of the water. 

Body size

Manatees are larger and can grow up to 4 metres (13 feet) long.

Dugongs are smaller and rarely get larger than 3 metres (10 feet) long.

Habitat 

Dugongs never leave saltwater. They spend their entire life in shallow, sheltered coastal areas such as bays and mangrove swamps.

Manatees, on the other hand, can be found both in fresh and saltwater. West Indian and West African reside primarily in salt water but migrate to warmer freshwater areas in the winter. The Amazonian manatee lives only in fresh water.

Teeth

Dugongs have overgrown incisors set at the front of the mouth that resemble small tusks. They are well developed and only visible in adult males and old female dugongs.

Manatees do not have the ‘tusks’. They have the marching molars (hind molar progression). Manatees constantly grow molars in the back corners of their mouth. As the front teeth grind down and eventually fall out, the molars fully emerge, pushing new teeth forward

Reproduction

Dugongs have a very long reproductive cycle. Female dugongs start conceiving at the age of  10 years. They only give birth every three to seven years. 

Female manatees typically have their first baby at age three and have more babies every two to three years.

Manatees are devout polygamists. A male manatee can have several female partners.

Dugongs, on the other hand, have different sexual lifestyles depending on the locality. In some areas, they are monogamous with only one mate, and they live as a couple for life. In other areas they are polygamist and polyandrous. They even display a mating behavior similar to lekking -  a lek is a traditional area where male dugongs gather during mating season to participate in competitive activities and displays to attract females.  

Once they success in attracting the female, they proceed through three phases.  In the following phase, a group of males follow a single female attempting to mate with her. This prompts the fighting phase whereby the males fight to determine who will mount the female. The winner enters the mounting phase where he mounts the female from underneath as the losers continue to fight for mating rights. The male is thus mounted several times by the competing males. This almost guarantees conception.

Humpback Whales Migration

It is that favourite season for the whale watchers again. The Humpback whales back at the Kenyan Coast to mate and give birth.

 

The humpback whale gets its common name from the distinctive hump on its back.  Its long pectoral fins inspired its scientific name, Megaptera novaeangliae. Megaptera, means “big-winged” and novaeangliae, which means ‘New England’ in reference to the location where European whalers first encountered them.

The humpback whales have one of the longest migrations of any on the planet. They swim over 5,000 kilometers annually from colder polar feeding waters (high latitude grounds) to the warmer mating and calving waters (low latitude grounds).

Humpbacks are massive. They range from 12 to 16 meters (39 to 52 feet) in length and weigh approximately 40 tonnes. They are mainly black or grey with white undersides to their flukes, flippers and bellies. 

Despite their massive size, the humpback whales feed on krill (small shrimp-like crustaceans), plankton, and small fish. They catch them by straining huge volumes of ocean water through their baleen plates, which act like a sieve.

They use a unique method of feeding called bubblenetting. They dive deep then swim up in a spiral pattern, while releasing a steady stream of bubbles from their blow holes. As the bubbles rise they form a "net" that surrounds the whales' prey. The whales swim up through the centre of the bubble net and feed on the prey trapped inside.

The humpbacks are one of the most acrobatic cetaceans. They frequently breach by leaping belly-up completely clear of the water, then arching backward and returning to the surface with a loud slapping sound. When beginning a deep dive, they hunch their back and rolls steeply forward, bringing its tail out of the water and perpendicular to the ocean surface.

Humpbacks are famous for their "songs." Male humpbacks produce a long series of calls that are normally heard during the winter breeding season. The whales may repeat the same song for several hours.  The songs appear to be shared by all singing members in the same area of the ocean: as the song changes, all members sing the new song. The same song is sung in spite of the great distance between groups in the population (up to 5000 km). This sharing of songs may occur when groups intermingle during migration or in shared summer feeding grounds.

The humpbacks have complicated courtship behaviours. Often, many males will surround a single female hitting each other in a competition to get close to her. Females become pregnant about every two to four years, and are pregnant with each calf for about 11 to 12 months. The calves can grow 0.5 metres every month while nursing on their mother’s rich milk. Females nurse their newborn calves in warm, shallow water. 

After spending two months breeding and nursing their calves, the whales will then make their journey back to Antarctica around September.