Effects of temperature on climbing behavior ofLittorina irrorata: On avoiding a hot foot

Abstract

Intertidal salt marsh inhabitants, such as the snail, Littorina irrorata, often exhibit vertical migration between the mud substratum and stems of Spartina altemiflora in synchrony with the tidal cycle. However, this behavior, which has been characterized as a predator avoidance mechanism, also occurs at low tide when aquatic predators are absent. Previous studies may have underestimated the contribution of physical factors in selecting for a behavior which reduces mortality in such a population. A positive relationship between substratum temperature and climbing behavior was demonstrated in the laboratory as well as in the marsh habitat. Temperatures exceeding 35°C in the laboratory resulted in either climbing or inactivity. At a substratum temperature of 40°C, snails exhibited a preference for climbing stems of lower temperatures (e.g., stems of ≤25°C exhibited an 0.80 probability of eliciting climbing behavior). In the marsh, a positive relationship between substratum temperatures ≥29°C and snail climbing height was observed. Thus, Spartina provides a refuge from high substratum temperatures, and climbing by Littorina represents a form of behavioral thermoregulation, as well as a means of avoiding predation.