Environmental variables associated with mosquito breeding habitats at two zoological parks in South Carolina, US

From March 2008 to January 2009 mosquito larvae were sampled at two zoological parks (i.e. zoos) in South Carolina. The objectives of the study were to determine the mosquito species breeding on zoo grounds, and the environmental variables useful as predictors of species presence in the zoos. There were 27 (zoo 1) and 31 (zoo 2) sites initially identified and then sampled up to seven times over the study period. Habitats were classified as either natural or man-made pools, or natural or man-made containers. Site variables measured were canopy cover and height, conductivity, dissolved oxygen, pH, and water depth and surface area. Additionally, the average high and low temperatures, and precipitation from the week preceding collections were recorded. In total, sixteen species and 1,630 larvae were collected and identified during the study period. The most abundant species, comprising 91.7% of all larvae collected, were Aedes albopictus (46%), Culex pipiens complex (9.7%), Culex restuans (12.4%), and Ochlerotatus triseriatus (23.6%). Multiple logistic regression (species presence/absence) and ANOVA (species abundance) on site variables were performed for each of these four species. In both zoos Ae. albopictus was best predicted by surface area, depth, and canopy cover, and significantly associated with man-made containers in one zoo. Cx. pipiens complex was significantly associated with man-made pools in one zoo. Cx. restuans was significantly associated with both pool types in one zoo, and natural pools in the other. Oc. triseriatus was best predicted by dissolved oxygen and shade height. Respectively, 71.9% (zoo 1) and 54.6% (zoo 2) of these larvae were found in man-made habitats.