Fish and aquatic news » Manatee http://www.aquaticcommunity.com/news The latest news from below the surface Wed, 23 Oct 2013 11:30:17 +0000 en-US hourly 1 http://wordpress.org/?v=3.6.1 The mystery of why Amazonian manatees migrate http://www.aquaticcommunity.com/news/lib/492 http://www.aquaticcommunity.com/news/lib/492#comments Fri, 01 Jan 2010 15:55:50 +0000 William http://www.aquaticcommunity.com/news/?p=492 A few years back scientists became aware that Amazonian manatees (Trichechus inunguis) migrate from shallow to deep water each year, starting in October or November when the dry season makes the water level decrease in their favoured habitat. A team of Brazilian and British researchers now claim have found out why these mesmerizing creatures undertake a perilous journey to get to a habitat that doesn’t have much to offer food wise.

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manatee The mystery of why Amazonian manatees migrate A few years back scientists became aware that Amazonian manatees (Trichechus inunguis) migrate from shallow to deep water each year, starting in October or November when the dry season makes the water level decrease in their favoured habitat. A team of Brazilian and British researchers now claim have found out why these mesmerizing creatures undertake a perilous journey to get to a habitat that doesn’t have much to offer food wise.

By studying manatees living in the Mamiraua and Amana Sustainable Development Reserves in north-western Brazil, the team found out that if the manatees wouldn’t move, the animals would be become stranded in the shallow water and exposed to predators such as caimans and jaguars.

Amazonian manatees migrate to a habitat that doesn’t offer easy living conditions in order to flee from a habitat that becomes inhospitable,” says team-member Dr Eduardo Moraes Arraut from the National Institute for Space Research in Sao Paulo, Brazil.

A dangerous voyage
In order to reach deeper waters, the manatees must pass through narrow bottlenecks in the landscape where they easily fall prey to predators – including humans. Hunting manatee is illegal in Brazil but the local people have a long tradition of eating the meat.

Once the manatees reach their destination, it isn’t much of a relief either. Due to a lack of aquatic plants in their new home, they are forced to go without food for several months.

When you have two options that are not good, you choose the one that is less bad,” Dr Arraut explains, adding that the harshness of the low-water conditions surprised him.

Modern technology and ancient knowledge
In order to learn more about the elusive manatees, the international research team asked local inhabitants about the movements of the manatees, and placed modern radio tracking devices on 10 individual manatees. What they found was that the Amazon landscape forces the manatees to migrate through a type of narrow lakes known as rias, a type of submerged river valleys.

Dr Arraut now wishes to track manatees in other parts of the Amazon to find out if they are facing similar obstacles as the populations in Mamiraua and Amana.

The findings have been published in the Journal of Zoology.

http://www.zsl.org/info/publications/

A gentle giant
The Amazon manatee is one of the smallest species of manatee but can nevertheless reach a length of 9.2 ft (2.8 m) and weight 800-1200 lbs (360-540 kg). It is only found in the Amazon River basin, in the countries Brazil, Peru, Colombia, Guyana and Ecuador.

During the high-water season (mid-May to late June), the Amazon manatees live in quiet lakes (so called varzeas) that form within river flood plains in the Amazon. In this hospitable environment, they feast on aquatic plants and typically consume 8% of their weight in greens each day. For a manatee weighing 800 lbs, that means 64 lbs – almost 30 kg!

Picture is depicting a manatee in Florida (not an Amazonian Manatee)

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Record number of manatees sighted in Florida http://www.aquaticcommunity.com/news/lib/198 http://www.aquaticcommunity.com/news/lib/198#comments Mon, 02 Feb 2009 00:40:30 +0000 William http://www.aquaticcommunity.com/news/?p=198 The yearly manatee count revealed a record number of manatees this year. The survey counted 3807 manatees which is about 500 more than the previous record from 2001........

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The yearly manatee count revealed a record number of manatees this year. The survey counted 3807 manatees which is about 500 more than the previous record from 2001.

manatees Record number of manatees sighted in Florida
Manatee with calf

Experts do however say that it is too early to cheer and that one shouldn’t read too much into this as this year offered ideal conditions for spotting manatees. Cold temperatures made the manatees gather in warm clear waters around nuclear power plants and natural springs making them easy to spot. The previous record year 2001 – when about 1000 more manatees were counted than the year before and the year after – also offered similar conditions. It is important to remember that the count doesn’t reflect the actual number of manatees but rather a minimum number of manatees as not all of them can be found and counted.

Wildlife managers and manatee advocates do however call the number encouraging and say that it might indicate that the manatee population is slowly recovering as the number is higher then the numbers the previous record year. They say that the count supports population models suggesting manatees are increasing in Northwest Florida, along the Atlantic Coast and on the upper St. Johns River. Pat Rose, executive director of the “Save The Manatee Club” does however add that the numbers in Southwest Florida and the Everglades, home to about 40 percent of all manatees in Florida, are believed to be in continuing decline. Data on this region is however much more scare as it is hard to keep track on the animals in the dark waters found in this area.

Considering that scientists earlier estimated the manatee population in all of Florida to be below 1500 animals it can only be concluded that the conservation process have been a success and with 3807 animals it seems clear that the situation is much better than it once were, even if there still is much work to do to protect these gentle giants.

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Dwarf Manatee – World’s cutest creature found in the Amazon? http://www.aquaticcommunity.com/news/lib/77 http://www.aquaticcommunity.com/news/lib/77#comments Fri, 22 Aug 2008 22:45:40 +0000 William http://www.aquaticcommunity.com/news/?p=77 This might not be news for some of you, but for those of you that has missed it: a new species of manatee might have been encountered by Dr Marc van Roosmalen in the Brazilian Amazon! Not only is this believed to be an entirely new species of manatee; it is also the smallest living member of the order Sirenia, […]

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This might not be news for some of you, but for those of you that has missed it: a new species of manatee might have been encountered by Dr Marc van Roosmalen in the Brazilian Amazon! Not only is this believed to be an entirely new species of manatee; it is also the smallest living member of the order Sirenia, measuring no more than 130 cm as an adult.

Trichechus pygmeus Dwarf Manatee   Worlds cutest creature found in the Amazon?
All Picture by: Marc van Roosmalen

In September 2002, wildlife-researcher Dr Marc van Roosmalen collected a complete skull from a recently killed specimen, but it would take an additional two years before he could finally photograph, film and examine a live specimen in its natural environment. As per usual when a new mammal is “discovered”, the species is only new to the scientific community, not to the locals of the area, and the skull of the specimen collected by van Roosmalen came from a manatee that had been killed and eaten by the locals.

Van Roosmalen has proposed that the so called Dwarf manatee should be considered a separate species of manatee and has given it the name Trichechus bernhardi, but others have suggested that this peculiarly small manatee is actually an immature Amazonian manatee (Trichechus inunguis). Both animals are very closely related and mitochondrial DNA (mtDNA) comparisons have failed to reveal any difference between the two.

According to van Roosmalen’s scientific description of the dwarf manatee, it lives in one of the tributaries of Rio Aripuanã where it inhabits shallow, fast running water. This distinguishes it from the Amazonian manatee which is known to prefer deep and slow moving waters and is found throughout a much larger part of South America. There is also a difference in diet; both animals feed on aquatic plants but on different species. In addition to this, there is a significant disparity in both proportions and colour. The dwarf manatee weighs about 60 kg as an adult and has a dark, almost black, body adorned with a white patch on the abdomen. The Amazonian manatee is much larger than the Dwarf manatee and can weigh over 500 kg. This difference has been used by both sides; those who believe that it is a separate species and those who believe it to be an immature Amazonian manatee.

dwarf manatee Dwarf Manatee   Worlds cutest creature found in the Amazon?

Regardless of whether this is truly is new species or merely an immature version of the Amazonian manatee, I certainly agree with Christopher Collinson’s comments on the Tetrapod Zoology blog: “On a side note, why the heck are those dwarf manatees so friggen adorable? They have way more cutesy factor than any one animal should be allowed to posess, its at least like a million times more than regular old plain Jane manatees.”

dwarf manatee swimming Dwarf Manatee   Worlds cutest creature found in the Amazon?

First dwarf manatee Dwarf Manatee   Worlds cutest creature found in the Amazon?
Picture courtesy of: Marc van Roosmalen

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