Bolivian river dolphin – Inia boliviensis

Inia boliviensis

The Bolivian river dolphin - Inia boliviensis. Source: http://www.allvoices.com

Unique new species of Amazon river dolphin isolated by raging rapids

Scientists in Bolivia have recently discovered a new species of dolphin, which lives only in the Bolivian Amazon, cut off from other river dolphin populations by a series of 18 impassable rapids between Bolivia and Brazil.  The Bolivian river dolphin – or bufeo as it is better known locally – has evolved in this riverine isolation to develop as a separate species to its better known cousins.  The Bolivian species is lighter grey in colour and has a larger row of teeth than other river dolphins.

As you might expect, the Bolivian government is very proud of this unique new population, and has designated the Bolivian river dolphin as a Natural Heritage species, and prioritised its conservation.  The river dolphins are highly sensitive to pollution, and so provide excellent indicators of the overall health of the river system.

It is amazing to think that in a world where nature often seems to have been entirely explored, described and named, it is still possible for entirely new populations of such large creatures to be discovered.  It certainly makes you wonder what other curious aquatic populations are lurking in our lakes and rivers, (as yet!) undiscovered by science?!

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Baikal seal – Pusa sibirica

Baikal seals basking in the sun (image: Sergey Gabdurakhmanov under Creative Commons http://www.flickr.com/photos/gabdurakhmanov/)

Tiny land-locked, freshwater seal mysteriously exists miles from the sea

The Baikal seal is a true natural marvel.  One of the world’s smallest seals, it’s entire population is land-locked in the freshwater of Russia’s Lake Baikal.  The ongoing mystery as to how the seal became trapped in Lake Baikal continues to puzzle scientists.

Whilst it is estimated that the seals have inhabited Lake Baikal for over 2 million years, the route and timing of their isolation from the sea is a mystery.  One hypothesis says that Baikal seals are descended from ancestors in the Paratethys Sea, which covered south-east Europe until roughly 2-3 million years ago.  An opposing idea is that the Baikal seals are of Arctic ancestry, and migrated south through a formerly connected network of rivers and lakes.

Regardless of its ancestry, the Baikal seal has evolved some amazing adaptations to its land-locked home.  Reaching a maximum size of 1.5m and 80-90kg, the Baikal Seal is one of the world’s smallest seals.  The seal’s eyes are surprisingly large in comparison to the body size – an adaptation to the low light conditions found under the ice.  Again, they are unusually long-lived seals – often living well past 50 years and reproducing into their 40s.

Baikal Seal pup (image: Pacific Environment under Creative Commons, http://www.flickr.com/photos/pacific_environment)

The Baikal seal’s feeding habits are also pretty unusual.  It can stay under water without coming up for air for over 70 minutes – whether to hunt or to avoid danger.  Weirdly, in the early autumn before the winter freeze, the Baikal seal will preferentially feed on fish such as sculpin in shallow lake bays and coves.  Eating this prey means the seal consumes a large amount of grit, which is thought to clean the seal’s innards and remove parasites.

Lake Baikal itself is remarkable.  At 636 km long, almost 80 km wide at its widest point, with an average depth of 700 m and a maximum depth of 1.6 km, it is better termed an inland sea.  Indeed, it is recognised as the world’s oldest (25 million years +), deepest and clearest lake – holding over 20% of global surface freshwater.  Containing over 1,085 species of plants and 1,550 species of animals – many of which are restricted to the lake – Lake Baikal is extremely rich in biodiversity.

If you are lucky enough to visit Lake Baikal during spring or summer, you may see groups of up to 500 seals basking on the surface.

Lake Baikal as seen from space (image: Wikipedia)

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