An understanding of anthropogenic factors influencing wildlife invasions is crucial to development of comprehensive prevention and management strategies. However, little attention has been paid to the role religious practice plays in biological invasions. The tradition of wildlife release is prevalent in many areas around the world where Asian religions are influential and is hypothesized to promote species invasions, although quantitative evidence is lacking. We used an information-theoretic approach to evaluate the influence of Buddhist wildlife release events on establishment of feral populations of American bullfrogs (Lithobates catesbeianus) in Yunnan province, southwestern China, from 2008 to 2009. We identified frequency of release events and lentic water conditions as factors that promote establishment of bullfrog populations, whereas hunting activity likely helps to prevent establishment. Our study provides the first quantitative evidence that religious release is an important pathway for wildlife invasions and has implications for prevention and management on a global scale.

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Abstract. Globally, ceremonial wildlife release events, originated from the traditions of Buddhism and other Asian religions take place in large numbers every year, and have caused conservation concerns. These releases pose a paradox in that Buddhism is generally considered to have great respect for the environment and a desire to cause no harm to any living being, yet Buddhist wildlife releases have resulted in biological invasions. We explored this paradox by evaluating the release of two highly invasive species (American bullfrogs Lithobates catesbeianus and red-eared slider turtles Trachemys scripta elegans) by 123 Buddhist temples surveyed across four provinces in China and validating survey results with intensive field surveys of release sites. We found that ecological knowledge of invasive species reduced the probability of release; conversely, market availability increased this probability. We suggest that this invasion paradox stems largely from a lack of invasive species knowledge and thus targeted public education about invasive species could be an effective strategy for preventing religious release of invasive species on a global scale.

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We collected Osteopilus septentrionalis from Central Florida for analysis of sexual size dimorphism and compared our data to published information from populations across the native and introduced range of the species. We found significant sexual size dimorphism (females larger), with the degree of dimorphism decreasing with increasing degrees north latitude, a trend largely driven by a pronounced decrease in female mean snout to vent length. Potential explanations for this trend include reduced growth rates, increased time to maturity, and reduced life expectancy, all of which may be tied to climatic variation. A trend of decreasing female mean size toward the northernmost extent of the current introduced range of this species may be indicative of diminished impacts and invasive success. Geographical variation in morphology and its associated implications should be evaluated when considering the potential impacts of invasive species.

Invasive species often exhibit geographical variations in life history traits that may allow them to successfully invade different environments. We investigated geographical variation in body size and sexual size dimorphism (SSD) of invasive bullfrogs in southwestern China, by sampling two breeding populations (descendants of a single source population) inhabiting sites at low (1,412 m, Shiping) and high (2,692 m, Luguhu) altitudes. Both populations exhibited significant SSD, with females larger than males. At high altitude, mean body size of both sexes and the degree of SSD were significantly reduced; the reduction in mean body size with increasing altitude was more pronounced in females, although not significantly so. Female bullfrogs also showed a significant decrease in average age at high altitude that may be a major factor related to this pattern; average age of male bullfrogs did not vary significantly with altitude. Growth rate of both sexes was also lower at high altitude. Our results provide the first evidence that introduced bullfrog's exhibit geographical variation in morphology in invaded areas in response to different environments, likely due to changes in climate. Additional research is required to determine the mechanism of this variation (i.e., physiological or developmental plasticity, mortality rate, selective pressure) and most importantly, to evaluate the potential for variation in the impacts of introduced bullfrogs on native ecosystems in China.

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