EPOW - Ecology Picture of the Week

Each week a different image of our fascinating environment is featured, along with a brief explanation written by a professional ecologist.

9-15 June 2003

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A Tale of Two Echidnas


Short-beaked Echidna (Tachyglossus aculeatus)

Credit & Copyright: Dr. Bruce G. Marcot

Explanation:   Only  three species of mammals on Earth lay eggs -- the Duck-billed Platypus and two species of echidna.  Shown above are two photos of the Short--beaked Echidna of Australia (the much larger and threatened Long-beaked Echidna resides only in New Guinea).  But can these two photos really be the same species?

Yes.  The left photo was taken in New South Wales of southeast Australia, and the right photo in Tasmania (the island state of Australia to the south).  Echidnas everywhere are covered in sharp spines, derived from modified hair (keratin), that molt annually and serve as predator defenses.  However, echidnas in Tasmania are also covered in dense long fur and have shorter spines.  This is clearly an adaptation to the colder climate there ... and perhaps the shorter spines are a physiological tradeoff of having dense fur, or perhaps there was less evolutionary need for such Draconian predator defense on isolated Tasmania.  Some authors consider the Tasmanian form to be a separate subspecies, in fact.  

Monotremes date back to the Cretaceous Period of 100 million years ago in Australia.  

Next week's picture:  Skin Patterns

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