Thursday, 29 September 2016

The many faces of extinction

'Toughie', last Rabbs' Fringe-limbed treefrog

Rabbs' Fringe-limbed tree frog

This post is inspired by the incredibly sad news that the last Rabbs' Fringe-limbed tree frog (Ecnomiohyla rabborum) has died and this species has now been declared officially extinct. This species of frog was a forest canopy dweller found in Panama and was only discovered as recently as 2005 and classified as a separate species in 2008.  Sadly, around this time the chytrid fungus was noted in other frog species in the same habitat as the Rabb's Fringe-limbed tree frog which was the primary cause of the drastic decline of this species which resulted in one remaining male frog, 'Toughie', being left in captivity by 2012. This fungus has had devastating impacts on huge numbers of amphibians and scientists suggest that this is the worst disease to have ever impacted a group of vertebrates as it thought that it can infect every species of amphibian and is nearly always fatal.  Although there is a vain hope that there may still be some of this species of tree frog left in the wild, none have been reported in many years, so the strong likelihood is that this species is now gone forever.

Other types of extinction 

Scimitar-horned oryx
Not all cases of extinction are quite this straight forward.  For instance, a species may be relatively common in captivity but extinct in the wild.  An example of such a species is the Scimitar-horned oryx which was one of the most common mammals in Africa but hunted to almost extinction in the 20th century (primarily for its meat) until it was declared extinct in the wild in 1999.  A captive breeding programme is currently being set up for this species and small-scale reintroductions have begun so it is hoped that this status can be reversed.  

One of the remaining three northern white rhinos
Perhaps the most frustrating type of extinction includes species that are functionally extinct.  This describes a situation where the a species is still present but no longer viable to breed and therefore it is just a matter of time before they disappear. Arguably the most famous current example of this is the northern white rhino as this species only has three individuals remaining, one male and two females.  These rhinos are too old to naturally reproduce as these females a highly unlikely to have a successful pregnancy to produce a calf.  The situation is almost beyond hope but a handful of scientists are continuing to pursue new strategies to keep this species going.  One strategy is to remove the reaming eggs from these rhino females and fertilise them with the sperm of this male to create an embryo (IVF) that can then be carried by female southern white rhinos which are a far more numerous subspecies. This task is far from simple however as it is extremely difficult to access these female's eggs and then successfully fertilise them without risking the lives of these old rhinos.  If it is pulled off, it will be a first for rhino's and perhaps give this species, and others in a similar position, a lifeline.  It may be a big 'if' but these beautiful animals deserve all the help we can give them. 

Is extinction really forever?

There is a budding area of science that may change the stories of all these species and that is the theory of 'de-extinction'.  Our understanding and ability to work with genetic material has improved immensely in even the last decade with the possibility of bring wildlife species back from the dead perhaps not such a radical idea.  This is a very controversial concept which will always cause arguments but it will also continue to grow as, after all, the human race is in desperate need of a back up plan if we continue to decimate wildlife at the current rate.

At any rate, conservation should and will focus on trying to prevent other wildlife species becoming any type of extinct as is our duty.  We have failed the Rabbs' Fringe-limbed treefrog. I can only hope that our list of successes slowly starts to increase to make these failures more bearable.  

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