Meeting Abstract

P1.58  Monday, Jan. 4  Juvenile Density and Birth Rate in the Endangered Hawaiian Tree Snails Achatinella lila and A. fuscobasis PASCUA, M. T.*; HOLLAND, B. S.; University of Hawaii mapascua@hawaii.edu

Two species of the federally listed endangered tree-snail genus, Achatinella, occur in the Ko’olau mountain range of O’ahu and face threat of extinction due to factors including loss of habitat due to deforestation and, most urgently, alien predators. In an effort to preserve and restore the Hawaiian tree snails, a captive propagation program at the University of Hawaii has successfully yielded high numbers of A. lila and A. fuscobasis. These two species have shown highest fecundity of the 15 species in the program: a lab population of A. lila, started with 7 individuals in 1997, has increased to approximately 640 individuals; and a population of A. fuscobasis, started with 11 snails in 1991, has grown to about 350 individuals. This study aims to determine whether density of juveniles is associated with higher birth-rates. Results of the study will have direct relevance to captive-propagation management procedures, specifically whether to separate snails by size-class. We applied three treatments consisting of: (1) no juveniles present;( 2) low-density of juveniles; and (3) high-density of juveniles. Results suggest that birth rates are similar among the first and third treatments, with reduced birth-rates in the second treatment. While analyses of past records reveal some level of birth-rate decline after cage-splitting, they do not provide strong evidence that juvenile presence/density correlates with higher birth-rate, because birth-rate data are inconsistent among the cages and adults may become senescent.