Category: riverine mammal

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How do animals like beavers and otters stay clean underwater (and benefit their environment at the same time)

A British beaver living out its life on the the river Otter in Devon

Anyone who has removed a branch or similar from a pond, will remember the incredible quantity of weed that will have wrapped around it. Any surface which lies underwater, tends to accumulate variety of things which makes it “grimy”. From dirt to algae and even bacteria, the process is called fouling.

However, animals like otters and beavers do not have to spend large amounts of time removing these substances from their fur – Why? This ability comes in part from the fur itself, where each hair can bend and flex as the animal moves, and a recent study showed that this ability to move allows the accumulation of dirt to be less than half of that when the hair is held steady at both ends (or for instance in hair that does not sway). This is a big issue in places such as boat, and people are working on ways to stop this.

It is fascinating the way that so many human processes take their inspiration from the natural world.

Beaver dams create barriers which allow all these bad substances to be removed. Dams block large quantities of soil, manure, slurry and fertilisers from rivers and streams, The stationary water allows substances like fertilizers and other chemical substances to sink to the bottom and be removed from the river ecosystem. Both the European beaver and the American beaver have the same impact on their water environment. While otters do not have the same dam making ability, they do have cleaning impacts on their environments as well.

It is well known, that while otters and beavers are often not the first species to return after a river is polluted, they can accelerate the process.

Aragualan River Dolphin

Araguaian river dolphin by Rio Cicica

Araguaian river dolphin

The Araguaian river dolphin or Araguaian boto  is a South American river dolphin population native to the Araguaia–Tocantins basin of Brazil.

The recognition of I. araguaiaensis as a distinct species is still debated. It was originally distinguished from the Amazon river dolphin in January 2014. On the basis of nuclear microsatellite and mitochondrial DNA data as well as differences in skull morphology (it generally has a wider skull). It also differs from the Amazon and Bolivian river dolphins in the number of teeth per hemimandible (24–28 versus 25–29 and 31–35, respectively).

River dolphins have a complex set of acoustic calls that help shed light on their personalities, behaviours and interaction with other river dolphins. In a study by Gabriel Melo-Santos et. Al they analysed frequency contours of 727 signals They found that these signals had a critical similarity value of 96% and frequency contours were categorized into 237 sound-types. Interestingly the most notable and frequent sounds were emitted when calves were present shedding light on a close and complex mother child relationship. The findings show that the acoustic sounds of river dolphins are incredibly complex and are similar to those of by social delphinids, such as orcas and pilot whales.

The total population of the species is estimated to be of the order of 600 to 1500 individuals, and genetic diversity is limited.[4] The ecology of its habitat has been adversely affected by agricultural, ranching and industrial activities, as well as by the use of dams for hydroelectric power. The inhabited section of the Araguaia River probably extends over about 1500 km out of a total length of 2110 km. The Tocantins River habitat is fragmented by six hydroelectric dams, so the population there is at particular risk.[4] The authors of the discovery paper regard its probable eventual IUCN status to be Vulnerable or worse.

The largest number of individuals of the new species is likely to occur in and around Cantão State Park, which contains most of the lakes in the Araguaia basin. However, commercial fishermen around the park have been killing them because they sometimes steal fish from nets. Shooting is common, but around protected areas like Cantão, where the sound of a gun might attract park rangers, some fishermen have taken to putting out poisoned bait for dolphins. The southernmost population of the species is a small group of isolated individuals in the Tocantins river above the Serra da Mesa dam.

Below you will find a list of any articles which mention this species specifically, below that is a video of this species in the wild. Below this, we will list any tourism opportunities (if any that we connect with).

Bolivian river Dolphin

Bolivian river dolphin by Ramon and Suzanne Vargas

Bolivian river-dolphin

Bolivian river dolphins were discovered by the Western world in 1832 by Alcide d’Orbigny. Initially considered a subspecies of the Amazon river dolphin, differences in body structure and the isolation of the Bolivian river dolphin meant it was reclassified as its own species in 2012. In a study conducted in 2015, it was also noted that any gene flow between I. geoffrensis (downstream) and I. boliviensis (upstream) would be a one way path flowing from upstream to downstream due to the Teotônio waterfall between them.

Even with gene flow, these populations would also remain morphologically different from each other due to the differences in the environment in which they live. Differences in seasonal water depth and speed would result in morphologically different species. However, for now, these populations are considered subspecies of the same species.

Research is hard to do, as the number of the species is low.

They are listed as endangered. Other threats include several dams, and while there are ways for river wildlife to navigate this, it requires moving through fast water, which this dolphin species does not do.

It is classified as endangered, though estimates of the current population size are hard to find.

Below is a video of this species, and below that is a list of any time it is mentioned on this site. Under this, we hope to add links that will allow you to see them in the wild.

Baji or Chinese river dolphin

Baija or Chinese river dolphin - Extinct

Almost definitely extinct, this species of river dolphin lived in the Yangtze and was also known as the white dolphin among other names.

The last confirmed sighting was now more than 20 years ago, and given the incredibly polluted state of their river home it is unlikely that any did survive. There may well be much debate in the future, as to whether similar river dolphins from elsewhere could replace them. What is clear is that this is irrelevant for a significant length of time, as it is likely to be many decades before the river is capable of supporting significant populations of fish, never-mind a river dolphin.

Below is a rare clip of it from before extinction, and below is any times that it is mentioned on this site. Given that it is extinct, its mentioning may not be helpful for seeing it, but may well be of interest. Below this video, is an automated list of any articles from this site which mentions this species. Unfortunately, as the species is extinct means that the local population cannot benefit from ecotourism, but there are many other species that still cling on in China. All wildlife has the capacity to bring in money for those who live nearby. Help us make this happen

Amazon River Dolphin

Amazon river dolphin by Oceancetaceen sometimes known as the Orinoco

Amazon Dolphin

The Amazon river dolphin, (other names include boto, bufeo or pink river dolphin), is a species of toothed whale endemic to South America and is classified in the family Iniidae. Three subspecies are currently recognized: Amazon river dolphin,, Bolivian river dolphin and the Orinoco river dolphin while position of Araguaian river dolphin  within the clade is still unclear The three subspecies are each found in a separate river basin (in order) the Amazon basin, the upper Madeira River in Bolivia, and the Orinoco basin.

The Amazon river dolphin is the largest species of river dolphin, with adult males reaching 185 kilograms (408 lb) in weight, and 2.5 metres (8.2 ft) in length. Adults acquire a pink colour, more prominent in males, giving it its nickname “pink river dolphin”. Sexual dimorphism is very evident, with males measuring 16% longer and weighing 55% more than females.

Like other toothed whales, they have a melon, an organ that is used for bio sonar. The dorsal fin, although short in height, is regarded as long, and the pectoral fins are also large. The fin size, unfused vertebrae, and its relative size allow for improved manoeuvrability when navigating flooded forests and capturing prey.

They have one of the widest ranging diets among toothed whales, and feed on up to 53 different species of fish, such as croakers, catfish, tetras and piranhas. They also consume other animals such as river turtles, aquatic frogs, and freshwater crabs. However, this is not particularly surprising, as there are so many forms of life in the Amazon rainforest, and plenty is likely to occasionally find themselves in the river.

In 2018, this species was classed as endangered, by the IUCN with a declining population. Threats include incidental catch in fishing lines, direct hunting for use as fish bait or predator control, damming, and pollution; as with many species, habitat loss and continued human development is becoming a greater threat.

While it is the only species of river dolphin kept in captivity, almost exclusively in Venezuela and Europe, it is difficult to train and often die very young, when kept in captivity..

Life expectancy of the Amazon river dolphin in the wild is unknown, but in captivity, the longevity of healthy individuals has been recorded at between 10 and 30 years. However, a 1986 study of the average longevity of this species in captivity in the United States is only 33 months. An individual named Baby at the  Duisburg Zoo, Germany, lived at least 46 years, spending 45 years, 9 months at the zoo.

Below you will find any news articles on Amazon dolphin (though articles with both words also get sucked in). Also  we will add any information on where you can go to see these in the wild, beneath both of these.

Common Hippopotamus

Common Hippopotamus

Hippopotamus are a fascinating animal. Large, highly aggressive, and spending most of their days in water. For many people, their memory of a Hippopotamus on safari (or in a zoo) is a pond with a grey bump in the middle. But there is far more to a hippopotamus than meets the eyes. Duromg the night, Hippo leave the safety of the water and go into the bush to graze.

They are incredibly dangerous, and there is a far higher risk for people wandering in the bush to be killed by hippo than anything else. In the past, they were one of the few species that still lived in significant numbers outside reserves. Unfortunately, as the human population of Africa has grown, the majority of these free roaming Hippo have been killed – for an African living on a tiny income, a hippo is a huge pile of meat, which can be sold, and some of its teeth are made of ivory.

A rough estimate suggests that the meat is worth around 8000. When you add in the Ivory teeth, it is possible for a Hippo carcass to be worth a years average salary (and that is the mean salary). 85% of Africans survive on $5.50 per day, which works out at almost exactly $2000 – so for 85% of Africans, a hippo carcass is worth 4 years of salary – assuming that you do not make much money from the ivory, and it would not be surprising if this added significantly.

When you look at these numbers, it is not surprising that people poach Hippos -and it makes it very hard to work out how to save them.

Of course, Hippo can be worth far more in tourism dollars over their lifespan.

Common hippopotamus are possible to see in all the Savannahs that we have listed so far. Visit wild places to see the total list.

Below is links to some of the biggest (though as I say, hippo can often be seen in small reserves and in places outside reserves as well. All our savannah wild places have sizable populations of common hippopotamus.

Limpopo transfrontier
Okavango delta (part of KAZA transfrontier park)
Serengeti from above

Pygmy Hippopotamus

Dwarf Hippopotamus

The dwarf hippopotamus was a little known species until more recently. However, the pygmy Hippopotamus is far more endangered, with an estimated population of just 2000-2500, compared to 115,000-130,000 common Hippopotamus remaining in the wild.

Now, of course, this comparison is foolish. While the current common hippopotamus is pretty much exclusively restricted to reserves, this is still a large area.

The vast majority – in both numbers and percentage – of the world’s remaining pygmy hippos are found in Liberia, although smaller populations still survive across the border in Côte d’Ivoire, Guinea and Sierra Leone. Furthermore, being a rainforest species, as the rainforest is cut down the animal looses its home (those which have not already been poached.

It is in the same genus as the common hippo, and they are clearly each others closest relation. I hope eventually to be able to list places for you to see this secretive animal, and give people a reason to protect it – if you work with an area like this, please do click on our link “list your wild place” we are eager to help people find you.

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