Association Between Habitat Characteristics, Human Activities, and Anuran Species in a Wetland Agricultural Landscape
I conducted anuran vocalization surveys in cranberry bogs, drainage ditches, and reservoirs of three active and three abandoned cranberry farms in the New Jersey Pinelands to examine the distribution of four anuran species in three consecutive years. I then applied a multinomial model to quantify their calling intensity and assess the influence of cranberry cultivation activities on each anuran species. I discovered that four species naturally inhabiting the Pinelands exhibited varied responses to cranberry cultivation. The responses ranged from positive to negative depending on the life history characteristics, disturbance tolerance, and especially the breeding season of the species in question. Green frogs (Lithobates (=Rana) clamitans) showed a high abundance in the bog habitats of active farms, where they exhibited prolonged courtship calls in late summer. Fowler's Toads (Anaxyrus (=Bufo) fowleri) exhibited high abundance in the ditches of active farms and the reservoirs of abandoned farms. On the other hand, Southern Leopard Frogs (Lithobates sphenocephalus) and Carpenter Frogs (Lithobates virgatipes) showed a reduced occurrence and calling intensity in active farms, probably because of the intensive water management that coincides with their breeding or wintering season, respectively. My findings indicate that wetlands in agricultural settings with diverse habitats can potentially be used as breeding habitats by anurans, but only if agricultural activities do not interfere with the anuran's breeding and wintering patterns.Abstract
Study locations within the Pinelands of New Jersey, USA. Aerial photo showing location of the six study sites (A) and survey locations within abandoned farm ABD1 (B) and active farm ACT3 (C). Letters in (B) and (C) indicate the actual survey sites of the three different habitat types: B = bog; D = ditch; R = reservoir.
Breeding phenology of the four anuran species during three breeding seasons (2006–2008). Data from the 3 yr were pooled. Each peak represents the mean calling intensity of the species over all surveyed locations, at the specified date, regardless of the farms, survey locations, habitat types, and farm types.
Model results showing each species calling intensity and the percentage of survey locations where each species was present. Letters A, B, C, and D indicate the mean calling intensity of Green Frogs (GF), Fowler's Toads (FT), Carpenter Frogs (CF), and Southern Leopard Frogs (SL) in bogs, ditches, and reservoirs within active and abandoned farms, calculated by the top submodel of each species (the mean calling intensity for each habitat is calculated as N̄ = 0*ψ0 + 1*ψ1 + 2*ψ2 + 3*ψ3). Letters E, F, G, and H indicate the percentage of surveyed locations where each species was present (i.e., probability of N≠0, calculated as 1 − ψ0). Error bars indicate the standard error (±SE).
Calling intensity of Green Frogs in bog habitats from May 2006 to August 2008. Calling index is calculated as the mathematical mean of the calling intensity of all surveyed bogs of each farm type (active vs. abandoned) at each specified date.
Contributor Notes
Present address: Department of Biology, University of Northern Iowa, 144 McCollum Science Hall, Cedar Falls, Iowa 50614-0421, USA; E-mail: ai.wen@uni.edu
