EPOW - Ecology Picture of the Week

Pacific (Coastal) Giant Salamander (Dicamptodon tenebrosus)
Tryon Creek State Park, Lake Oswego, Oregon

Explanation:  How can this tiny amphibian be a "giant?"  It is an immature Pacific (or Coastal) Giant Salamander that I discovered in a small stream in early winter, close to home in northwestern Oregon, USA.  

Immatures of this size are seldom seen because they can hide so well among the rocks and leaves of a stream bottom.  As they age, they grow more well-developed gills as the stream larval form ("neotenics") ... eventually becoming more terrestrial creatures at their full body size of up to 330 mm (13 inches). Now that's a giant salamander.

But the tiny juveniles are hardly large enough to fit on a coin.  This one had recently hatched from its egg, which is deposited in clusters underneath rocks and logs in streams.  

Juveniles this young and this small appear to be coated with a mucus, even apparently covering the eyes, which may play a role in ensuring that the body does not dry out.  The mucus layer might also play as a defense against predators, and also help avoid the loss of nutrients.  

Being this small means risking being prey to a variety of predators including raccoons, otters, water shrews, garter snakes, fish, and even other, older Pacific Giant Salamanders!  Yes, some are cannibalistic!  

These may be very uncommon photographs.  None of the field guides to amphibians of the region has photos of juvenile Pacific Giant Salamanders this young and this small ... the tiny giant in a winter stream!  

Information:
    Anderson, J.D. 1960. Cannibalism in Dicamptodon ensatus.  Herpetologica 16:260.
    Welsh, H. H., Jr. 2005. Coastal giant salamander Dicamptodon tenebrosus Baird and Girard. Pp. 54-57 in: L. L. C. Jones, W. P. Leonard, and D. H. Olson, eds. Amphibians of the Pacific Northwest. Seattle Audubon Society, Seattle WA. 227 pp.