SOUND PRODUCTION IN THE SMALL-MOUTHED SALAMANDER (AMBYSTOMA TEXANUM)

Abstract

Auditory signals are commonly used by vertebrates to communicate with one another. While not all vertebrates communicate in this way, vocal communication is an essential part of defense, courtship, and social cohesion in several taxa. Among the amphibians, frogs are well known for their vocalizations, some of which are used by males to attract females at breeding pools. The other extant amphibians (salamanders and caecilians) are generally regarded as mute. Despite this widespread assumption, there are numerous anecdotal reports of both aquatic and terrestrial salamanders that vocalize. Very few studies have attempted to put these sounds into any sort of behavioral context, despite the potential utility (e.g., mate attraction) such sounds may have. While salamanders are extremely limited in their ability to detect sounds transmitted through air, they are able to detect water-borne sounds. I placed Smallmouth Salamanders (Ambystoma texanum) into 19L plastic tanks containing aged tap water, and used hydrophones in an attempt to document underwater sound production in this species. Each tank contained one of the following combinations of salamanders: Isolate male, Isolate female, Male/Female pair, and Female/Female pair. I investigated a possible social context for the production of sounds by comparing the number of sounds produced in each tank. Although sound production was rare, it was recorded at least once in 86% of tanks. No social grouping tested promoted sound production significantly differently from any other, but verifying that sound production occurs in this species at all is an important step in studying the behavior of Small-mouthed Salamanders and non-anuran amphibians.