Investigating the dispersal routes used by an invasive amphibian, Lithobates catesbeianus, in human-dominated landscapes

Abstract

Clarifying how species move across and utilize human-modified landscapes is key to the conservation of declining populations, as well as to the management and control of invasive species. The North American bullfrog (Lithobates catesbeianus) is a globally distributed invasive amphibian that has been implicated in the decline of native amphibians across its invasive range and may also act as a transport vector for a number of deadly amphibian pathogens. Identifying the landscape-level features that facilitate or hinder this species as it moves across an ever-changing landscape is necessary to inform control efforts and limit this species’ impact on already declining amphibian populations. We conducted surveys of 243 wetlands across the Colorado Front Range and used an information-theoretic approach to evaluate the contribution of wetland-specific characteristics and landscape-level factors in determining the detection of bullfrog populations and breeding bullfrog populations. Specifically, our goal was to determine whether features related to overland dispersal or to the connectivity of wetlands were better predictors of bullfrog occurrence. Our results indicated that landscape-level factors that may either hinder or facilitate overland movement, such as topographic complexity and the density of wetlands, were the best predictors of bullfrog occurrence at the scale of our analysis, rather than characteristics relating to the connectivity of wetlands to lotic waterway systems. We suggest that when considering the control or eradication of this species, efforts should be directed at reducing hydroperiod of wetlands and should target regions with a high density of wetlands and/or low topographic relief.