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Prey Selection by the Tropical Snail Thais Melones: A Study of Interindividual Variation
Author(s) -
West Lani
Publication year - 1988
Publication title -
ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.144
H-Index - 294
eISSN - 1939-9170
pISSN - 0012-9658
DOI - 10.2307/1941161
Subject(s) - predation , biology , snail , thais , ecology , foraging , gastropoda , invertebrate , rocky shore , habitat , population , mollusca , zoology , demography , sociology
I studied the feeding behavior of marked individuals of the carnivorous marine snail Thais melones in a rocky shore habitat along the Pacific coast of Panama. These snails consumed a variety of invertebrate species such as bivalves, limpets, and polychaetes. The population of Thais melones was generalized in overall diet, but individuals varied in degree of specialization. Feeding sequences of 282 marked snails were divided into size classes for the 100 snails observed through five or more sequential feeding attacks. These sequences revealed two interesting patterns. First, diets varied from specialized to generalized even among individuals of similar size foraging adjacent to one another in the same habitat. Second, among individuals that exhibited more specialized diets, the prey species of choice was not always the same. Individual diets of snails were monitored twice daily in the field for time periods ≤3.5 mo. Two of five snails that were observed over longer periods showed consistency of prey choice with more specialized diets for 11 and 13 mo until they were lost. Neither of these patterns appeared to result from biased movements of individual snails among different habitat patches since mapped foraging tacks of individual snails intersected and overlapped extensively. Both of these results do, however, reveal that no single "optimal" pattern of prey selection was exhibited by these size—matched, co—occurring snails. In addition, for medium—sized snails (20—30 mm shell length), rates of spiral shell growth measured over the same time period revealed a statistically significant association with diet diversity: individuals with a less diverse (i.e., more specialized) diet tended to grow more rapidly, yet the relationship was not significant for small (<20 mm) or large (>30 mm) snails. These studies indicate that pattern of prey choice (i.e., specialized or generalized) may be as important as the composition of the diet on correlates of fitness. Superiority of a specialized diet (regardless of specific prey identity) could occur through increased efficiency in prey handling.