23 January 2006

A ruthless predator

This is a juvenile eastern red-backed salamander (Plethodon cinereus). There are 2 color morphs (phases) of this species: red-backed and lead-backed. The pictured specimen was obviously the latter morph.

Unlike many other salamander species that have aquatic larvae, the eastern red-backed salamander spends all of its life cycle on land even though it does not have lungs and obtains its oxygen thru its skin. Because they need to keep their skins wet at all times, these salamanders live in damp places in forests, for example under logs, rocks and in wet leaf litter. I found this individual under a small log on top of rotting leaves. Such places are also the preferred habitats of most land snail species of eastern forests. Not surprisingly, salamanders and land snails are usually found together and snails are among the favorite preys of salamanders1, 2.

In one laboratory study2, adult P. cinereus were kept for 3 months in containers (microcosms) with leaf litter containing various macroinvertebrates, including snails and slugs. At the end of the study, salamanders significantly reduced the density of macroinvertebrates in their containers (see figure below from the cited paper). The authors2 noted that "The six taxa absent from litter bags in salamander microcosms, but present in controls, were all macroinvertebrates: slugs, snails, centipedes, ants, adult beetles, and zoraptera." Salamanders may be small and cute, but they are also very efficient predators.

1. Craig A. Harper & David C. Guynn Jr. 1999. Factors affecting salamander density and distribution within four forest types in the Southern Appalachian Mountains. Forest Ecology and Management 114:245-252.
2. B. Michael Walton & Sonya Steckler. 2005. Contrasting effects of salamanders on forest-floor macro- and mesofauna in laboratory microcosms. Pedobiologia 49:51-60.


Duane said...

He sure doesn't look like a ruthless little guy. But, as they say, looks can be deceiving.

Alun said...

Have you considered sending this to Cute Overload? They're have photos of all sorts of animals.

Tree Hugger Daddy said...

I found a couple salamanders earlier this year. I don't suppose you happen to know if the one at the bottom of this post is a northern or southern two-lined? I wasn't sure...
salamanders link

I think it may have been a Northern, but Northern's aren't supposed to be this far South.