Tag: Manatee

Manatees and the Dugong

Dogong credit Niklas Findt
Amazon manatee
West african manatee
West Indian Manatee

Dugong and Manatees

The family Sirenia consists of 2 genus, the Dugongidae (only extant species is the Dugong)  and  Trichechidae which contains the 3 Manatee species.

The Dugong is the species in the top left (if you cannot pick it out). The Steller sea cow was a close relation of the Dugong

The big difference, is that unlike Manatees with a paddle shaped tail, where as Dugongs have fluked tails.

As always, as links are made to help with tourism, these will either appear below, or each species will be spun off to have its own page. Ecotourism need not have a big impact on the species and its natural behaviour, however, by giving them financial value to the local population you greatly increase the liklihood of survival as well as increasing the standard of living for local people.

 Should you work in tourism dealing with these species, do get in touch, there is a link at the top of the home page, with a simple form.

Dugong– The only surviving Dugongidae after the stellers sea cow (described in 1741 and hunted to extinction by 1768 for hide meat and fat) was lost.

It is found in the waters of around 37 countries in the Indo-west Pacific. It has recently become functionally extinct in Chinese waters, and may well be lost entirely in the near future. Its thought that while their current range is highly fractured, it is probably still a similar limit to before. These countries between them, give around 140,000km of coastline, and this area maps with where the correct species of sea grasses grow. The worldwide population is thought to have declined 20% in the last 90 years, though this is pretty good compared to many other species.

There are currently thought to be 100,000, with its conservation status being Vulnerable

Amazonian Manatee-Found in parts of the Amazon basin, throughout parts of Brazil, Colombia Peru and Ecuador.

It is the smallest of the surviving Manatees. Weights fall between 7,5kg and 350kg, with a 75cm-225cm length.  Given that it is likely decreasing, it is going to be below this now.

They are exclusively herbivorous, feeding on water lettuce and hyacinth. During a day, they can consume around 8% of their bodyweight. This mostly occurs during the wet season, during the dry season they return to the main river and survive on their fat reserves. They have a prehensile snout (like a less developed trunk) for feeding

They are considered Vulnerable, with the last count giving an upper limit of 10,000, however, this was in 1997. 

West-Indian manatee- So named,  because they were first sighted amongst a group of Islands called the West-Indies in the Caribbean – it is no-where near India (as you can see).  They live in shallow coastal areas. They have a prehensile snout (like a less developed trunk) for feeding. Unlike elephants, they are not limited to 6 sets of teeth, but only having molars (24-36) it is a simpler layout. As their range includes Florida (well known from the Everglades) this species is well known in places. They are hard to count, living in murky water,

Listed as vulnerable, the whole population is not thought to be greater than 10,000. The 2 subspecies are the Florida manatee (around 2500) and the Antillean Manatee which is found off the Atlantic coast of Mexico and central south America (particularly in the waters of greater Antilles) potentially, historically found along the coast of Texas (and as far north as Dennis, Tennessee).

African Manatee- (or West African Manatee) Although found both on the coast and inland, there is no significant genetic difference between these populations. African Manatees can be found in West African regions which include a wide range of countries – requiring cross nation action to save them. Manatees are found in brackish waters to freshwater: in oceans, rivers, lakes, coastal estuaries, reservoirs, lagoons, and bays on the coast.

The areas with the highest manatee populations are Guinea-Bissau, the lagoons of Côte d’Ivoire, the southern portions of the Niger River in Nigeria, the Sanaga River in Cameroon, the coastal lagoons in Gabon, and the lower parts of the Congo River. Alone amongst manatee species, the African manatee is Omnivorous, eating clams and molluscs as well as fish found in nets (can make up 50% of diet). They are more adaptable than other manatees, being able to survive in salt water (though they need access to fresh water to drink).

They are nocturnal, but many countries, a dead manatee is worth a lot to hunters. They are listed on CITES Appendix 1 with a population under 10,000. Cote d’Ivoire has a population of 750-800. Some of the biggest populations still live in Gabon, status is unknown in many areas. There is much tourism potential – worth a lot in Florida.

 

Spinner Dolphin

Spinner dolphin

The spinner dolphin (also known as the long-snouted dolphin (distinguishing it from the Clymene dolphin – which is often called the short snouthed spinner dolphin) is a small dolphin found in off-shore tropical waters around the world. It is famous for its spinning  along its length, as it leaps from the water. It is a member of the family Delphinidae of toothed whales.

The four named subspecies are:

  • Eastern spinner dolphin, found from the tropical eastern Pacific.
  • Central American or Costa Rican spinner dolphin, also found in the tropical eastern Pacific.
  • Gray’s or Hawaiian spinner dolphin, from the central Pacific Ocean around Hawaii but represents a mixture of broadly similar subtypes found worldwide.
  • Dwarf spinner dolphin, first found in the Gulf of Thailand.

The species, though, displays greater variety than these subspecies might indicate. A hybrid form characterized by its white belly inhabits the eastern Pacific. Other less distinct groupings inhabit other oceans.The species name comes from the Latin word for “long-beaked.”

Spinner dolphins are small cetaceans with a slim build. Adults are 129–235 cm long and weigh 23–79 kg. This species has an elongated rostrum and a triangular or subtriangular dorsal fin. Spinner dolphins generally have three colours, one on the dorsal fin, one on the underside and one on the upper-side. Also, a dark band runs from the eye to the flipper, bordered above by a thin, light line. However, the spinner dolphin has more geographic variation in form and coloration than other cetaceans. In the open waters of eastern Pacific, dolphins have relatively small skulls with short rostra. A dwarf form of spinner dolphin occurs around southeast Asia. In these same subspecies, a dark dorsal cape dims their tripartite colour patterns Further offshore, subspecies tend to have a paler and less far-reaching cape.] In certain subspecies, some males may have upright fins that slant forward.[8] Some populations of spinner dolphin found in the eastern Pacific have backwards-facing dorsal fins, and males can have dorsal humps and upturned caudal flukes.

The spinner dolphin lives in nearly all tropical and subtropical waters between 40°N and 40°S. The species primarily inhabits coastal waters, islands, or banks. However, in the eastern tropical Pacific, spinner dolphins live far from shore. Some studies suggest they use different areas at different times of the year.

The spinner dolphin feeds mainly on small mesopelagic fish, squids, and sergestid shrimps, and will dive 200–300 m to feed on them. Spinner dolphins of Hawaii are nocturnal feeders and forage in deep scattering layers, which contain many species. The dwarf spinner dolphin may feed mostly on benthic fish in reefs and shallow water. Off Oahu, Hawaii, spinner dolphins forage at night and cooperatively herd their prey into highly dense patches. They swim around the prey in a circle and a pair may swim through the circle to make a catch. Spinner dolphins are in turn preyed on by sharks. Other possible predators include the killer whale, the false killer whale, the pygmy killer whale and the short-finned pilot whale. They are susceptible to parasites, and are known to exhibit both external ones like barnacles and remoras as well as internal parasites.


Due to the spinner dolphin foraging and feeding at night, in certain regions, such as Hawaii and northern Brazil, dolphins spend the daytime resting in shallow bays near deep water. Spinner dolphins rest as a single unit, moving back and forth slowly in a tight formation but just out of contact with one another. These resting behaviours are observed for about four to five hours daily. During rest periods, spinner dolphins rely on vision rather than echolocation. At dusk, they travel offshore to feed. They travel along the shore during foraging trips, and the individuals that occupy the same bay may change daily. Some individual dolphins do not always go to a bay to rest; however, in Hawaii, dolphins do seem to return to the same site each trip.

Spinner dolphins live in an open and loose social organization. The spinner dolphins of Hawaii live in family groups, but also have associations with others beyond their groups. Mothers and calves form strong social bonds. Spinner dolphins seem to have a promiscuous mating system, with individuals changing partners for up to some weeks. A dozen adult males may gather into coalitions. Vocalizations of spinner dolphins include whistles, which may be used to organize the school, burst-pulse signals, and echolocation clicks. The spinner dolphin has a 10-month gestation period, and mothers nurse their young for one to two years. Females are sexually mature at four to seven years, with three-year calving intervals, while males are sexually mature at seven to 10 years. Spinner dolphins live for about 20-25 years old. Breeding is seasonal, more so in certain regions than others.

Although most spinner dolphins are found in the deeper waters offshore of the islands, the rest of the Hawaiʻi population has a more coastal distribution. During daytime hours, the island-associated stocks of Hawaiian spinner dolphins seek sanctuary in nearshore waters, where they return to certain areas to socialize, rest, and nurture their young.

They get their name for their spinning jumps, a spinner dolphin comes out of the water front first and twists its body as it rises into the air. When it reaches its maximum height, the dolphin descends back into the water, landing on its side. A dolphin can make two to seven spins in one leap; the swimming and rotational speed of the dolphin as it spins underwater affects the number of spins it can do while airborne. These spins may serve several functions. Some of these functions are believed by experts to be acoustic signalling or communication. Another reason is to remove ectoparasites such as remoras. Dolphins may also make nose-outs, tail slaps, flips, head slaps, “salmon leaps”, and side and back slaps.

The protected status of spinner dolphins are CITES Appendix II and Marine Mammal Protection Act (MMPA) protected throughout its range as well as MMPA depleted in its eastern stock. Tens of thousands of spinner dolphins, mostly eastern and white-bellied varieties, were killed in the 30 years after purse seine fishing for tuna began in the 1950s; The process killed probably half of all eastern spinner dolphins. They have also been contaminated by pollutants such as DDT and PCBs. Spinner dolphins, as with other species affected by ETP tuna purse-seine fishing, are managed nationally by the coastal countries and internationally by the IATTC. The IATTC has imposed annual stock mortality limits on each purse seine and promulgated regulations regarding the safe release of dolphins. The eastern tropical Pacific and Southeast Asian populations of the spinner dolphin are listed on Appendix II of the Convention on the Conservation of Migratory Species of Wild Animals (CMS), since they have an unfavourable conservation status or would benefit significantly from international co-operation organized by tailored agreements. In addition, the spinner dolphin is covered by Memorandum of Understanding for the Conservation of Cetaceans and Their Habitats in the Pacific Islands Region (Pacific Cetaceans MoU) and the Memorandum of Understanding Concerning the Conservation of the Manatee and Small Cetaceans of Western Africa and Macaronesia (Western African Aquatic Mammals MoU). Spinner dolphins are susceptible to disease and two of the recorded diseases within them are toxoplasmosis and cetacean morbillivirus. The number of cases reported however is fairly low in the species.

Spinner dolphins in Hawaii receive multiple daily visits to their near-shore resting grounds, with boats taking people out daily to snorkel and interact with the local dolphin population. Such activities are increasingly coming under criticism on the grounds of possible harm to the dolphins, and efforts are being made both to educate the public in order to minimise human impact on the dolphins, and to bring in regulations to govern these activities. In 2023, 33 swimmers were arrested for reportedly harassing dolphins off the coast of the Big Island of Hawaii. The swimmers reportedly broke federal law by swimming within 45 meters (50 yards) of the dolphins. The ban went into effect in 2021 due to dolphins not getting enough rest during the day to forage for food at night. The swimmers were caught by drone footage pursuing the dolphins as they tried to escape.

We are eager to work with people who run boats to see these animals – provided they are run with due care for the animals. Do get in touch, or fill in a form you will find in ‘List your wild place’ at the top of the page (or click here).

aaa Sian ka’an biosphere reserve, Monarch butterfly migration Yucatan Peninsula, Mexico

Sian ka'an biosphere reserve, Yucatan Peninsula, Mexico

 

 

Bottlenose dolphin, Sea green turtle, Caribbean manatee, Central American Tapir, Forest condor or real condor, Jaguar, Howling monkey, Ocelote in Sian Ka’an, Western manatees can all be found in this reserve. 

 

The reserve is made up of tropical forests, mangroves, marshes and a large area of ocean.  The reserve’s name can be translated as gate of heaven. 

 

The reserve covers over 5000 Square km, Part of which is land and the rest is in the coral sea and includes a large area of coral reef.

 

This is an 8 minute video of someone exploring some of this reserve

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The Florida manatees are facing significant threat to the long-term survival

Runoff from farms has caused an algae bloom which has not left space for enough sea grasses – the primary food of the manatee.

a Floridian Manatee

Without food the manatee population is severely endangered and likely to suffer mass starvation. 12 manatees have already died this year due to this poisonous algae.

The united fish and wildlife service changed the conservation status of manatees from endangered to threatened in 2019: this was clearly not a good move.

A considerable number of Floridians are blaming the current administration and Rick Scott who has determinately reduce the budget of of these environmental protections. Without a significant changing governmental behaviour this is unlikely to be reversed anytime soon.

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