title: Reproductive Ecology of the Giant African Snail in South Florida: Implications for Eradication Programs.
abstract: Giant African snail (Achatina fulica (Bowdich, 1822)), an important invasive snail, was recently found in South Florida, USA. An extensive eradication effort was initiated consisting of pesticide applications, debris removal and hand collections. We studied the reproduction capacity and population dynamics of snails collected from 22 populations for two years to help evaluate the likely success of the eradication program. A total of 23,890 snails, ranging from 25-131 mm, were measured, dissected and the number of eggs in each snail counted. Gravid snails ranged from 48-128 mm. Only 5% of snails had eggs, which were found year round. As the snails increased in size, they were more likely to include reproducing individuals. However, the percentage of gravid snails peaked when snails were approximately 90 mm. Although more prevalent, small (<65 mm) adults contributed fewer eggs to the population than the larger snails. We evaluated the effect of control measures on six populations having >1000 adult snails and used data from the two largest populations to investigate how environmental factors (temperature, humidity, and rainfall) interacted with population dynamics and control measures. More snails were collected in weeks with high humidity and more gravid snails were collected when the temperature was higher. The addition of metaldehyde pesticides had the greatest impact on population dynamics by reducing snail numbers. In populations with fewer snails, their numbers were already declining before the use of metaldehyde, although the new treatment accelerated the process. As a consequence of the eradication program, egg-producing snails were no longer collected from most populations by the end of the study. The aggressive and persistent control efforts apparently lead to reduced populations of egg producing snails, eventually resulting in local extinctions of this important pest.
authors.affiliation: Miami Laboratory, Center for Plant Health Science and Technology, Plant Protection and Quarantine, Animal Plant Health Inspection Service, United States Department of Agriculture USDA-APHIS, Miami, Florida, United States of America.
authors.forename: Amy
authors.identifier: http://orcid.org/0000-0003-2672-9695
authors.initials: A
authors.lastname: Roda
authors.affiliation: Section of Ecology and Evolution, Department of Biology, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Gösta
authors.initials: G
authors.lastname: Nachman
authors.affiliation: Miami Laboratory, Center for Plant Health Science and Technology, Plant Protection and Quarantine, Animal Plant Health Inspection Service, United States Department of Agriculture USDA-APHIS, Miami, Florida, United States of America.
authors.forename: Scott
authors.initials: S
authors.lastname: Weihman
authors.affiliation: Giant African Land Snail Eradication Program Miami, Division of Plant Industry, Florida Department of Agriculture and Consumer Services, Miami, Florida, United States of America.
authors.forename: Mary
authors.initials: M
authors.lastname: Yong Cong
authors.affiliation: Miami Plant Inspection Station, Plant Protection and Quarantine, Animal Plant Health Inspection Service, United States Department of Agriculture, Miami, Florida, United States of America.
authors.forename: Fredrick
authors.initials: F
authors.lastname: Zimmerman
mesh_terms: D000818:Animals; D049628:Body Size; D004463:Ecology; D004777:Environment; D005431:Florida; D011157:Population Dynamics; D012098:Reproduction; D012908:Snails