Thursday, January 30, 2014

Ligers and zonkeys and eles oh my!


If the Internet has taught us anything, it's that we love strange and adorable animals.  Possibility one of the most reliable sources of such creatures is hybrids: we love discovering new, and sometimes fictional, animal creations.  Although when we hear the term "hybrid," we often picture a car, it is used in biology to refer to an organism that resulted from cross-breeding of (typically) two different species.  Hybrids are quite common in plants, though today we are going to focus on animal hybrids (our apologies to our botany fans).  There are many well-known types of hybrids in the animal kingdom, including the liger (a lion/tiger), mule (a horse/donkey), and zonkey (zebra/donkey).  For most hybrids, the physical appearance and name of the animal depends on the sex of each parent species: the difference between a tiglon and a liger depends on species of the mother and father. For example, a liger is a cross between a male lion and a female tiger, while a tiglon is a cross between a female lion and a male tiger. 

hercules liger
Hercules the liger

Many hybrids occur in nature, especially amongst plants.  Some, however, only occur when two species are artificially housed together in captivity.  Even when housed together, though, some animals simply can't breed to form hybrids (even if they seem closely related).  The resulting fetus may not be carried to term or, even if it is, it may be nonviable.  This means the hybrid itself cannot breed--this is the case with mules.  The only way to get new mules is by crossbreeding horses and donkeys.

Hybrids between two species in captivity are quite often unexpected.  For example, Ippo the zonkey was born this year after his  father (an amorous zebra) jumped the fence into an enclosure holding a female Amiata donkey.  The owners were quite surprised when, a year later, their donkey gave birth to a striped foal!

Ippo the zonkey foal

For such a hybrid to occur between two historically geographically separated species is quite incredible.  In the case of elephants, it was long believed that African and Asian elephants would be unable to produce a hybrid that could be carried to term and born successfully.  Asian and African elephants have been separate species for almost 7 million years; Asian elephants are actually more closely related to the now-extinct wooly mammoth than to African elephants.  Thus, African and Asian elephants have been kept in the same enclosures in some zoos and parks, with little concern for any inter-breeding that may occur.  Even if a male elephant were to mate with a female, it was not believed that any offspring would result.

However, in 1978, keepers at the Chester Zoo in the UK were shocked to discover that Sheba, their female Asian elephant, was pregnant.  The only possible paternal candidate was Jumbolina (also called Bubbles), a male African elephant.  Much to the keepers' amazement, Sheba carried her calf succesfully, and gave birth on November 7, 1978.  He was named Motty, after George Mottershead, the founder of the Chester Zoo who had recently passed away.

Motty with his mother

Motty was undersized and unable to stand soon after his birth, which suggested that he was born prematurely.  However, he appeared to do well after hourly feedings of glucose supplementing his mother's milk.  Amazingly, Motty sported a beautiful mix Asian and African physical features.  He had large ears, shaped like those of a typical African elephant.  His legs were long and slim like an African elephant, and he had a large single dome on his head.  However, he also had two smaller domes behind the large one, like an Asian elephant.  Motty had Asian elephant features in other ways: a single "finger" on the end of his trunk, and the typical five-four front-back foot toe nail pattern. 

Photograph demonstrating the mixed Asian and African elephant traits


Sadly, a week after his birth, Motty developed an umbilical cord infection, and rapidly fell ill.  Two days after starting treatment, Motty passed away from necrotic-enterocolitis and E. coli.  He was exactly two weeks old.

It's unclear why Motty got so sick so quickly--most likely, premature care for elephants at that time was not as effective as it is now.  Perhaps, if Motty had been born in 2014, he would have been successfully treated and survived.  Unfortunately, we will never know if he was viable and able to reproduce himself.

Although a sad story, Motty is a remarkable example of cross-breeding.  Although African and Asian elephants are not only different species, but also belong to different genera, they were able to interbreed.  Such a hybrid may never occur again, and there's no reason for it to, but it is certainly a remarkable example of nature defying our expectations.

References


http://news.bbc.co.uk/2/hi/sci/tech/6913934.stm

http://www.huffingtonpost.com/2013/09/13/hercules-liger-worlds-largest-cat-photos_n_3920158.html

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