Non-native populations and global invasion potential of the Indian bullfrog Hoplobatrachus tigerinus: a synthesis for risk-analysis

Abstract

Invasive amphibians have considerable ecological and socio-economic impact. However, strong taxonomic biases in the existing literature necessitate synthesizing knowledge on emerging invaders. The Indian bullfrog, Hoplobatrachus tigerinus, a large dicroglossid frog (snout to vent length: up to 160 mm), is native to the Indian sub-continent. Despite the high likelihood of invasion success for H. tigerinus, based on the species' natural history traits and human use, the status of its non-native populations and global invasion potential has not yet been assessed. In this paper, we provide a profile of H.tigerinus as an invasive species to aid in risk analyses and management of existing populations. We review the available knowledge on non-native populations of H. tigerinus and model its potential distribution in the non-native range and globally; finally, we evaluate its ecological and socio-economic impact using standard impact classification schemes. We confirm successful invasions on the Andaman archipelago and Madagascar. The ensemble species distribution model, with 'good' predictive ability and transferability, predicts tropical regions of the world to be climatically suitable for the species. Considering potential for propagule pressure, we predict the climatically suitable Mascarene Islands, Malaysia and Indonesia, and East Africa to likely be recipients of bridgehead invasions. We assign the species two impact scores: both socio-economic and environmental scores were 'moderate' with 'medium' confidence levels in our assessment. Finally, this synthesis outlines the invasion process of the genus Hoplobatrachus, which is an emerging group of amphibian invaders.Keywords Amphibian Á Madagascar Á Andaman Nicobar Á Island invasive Á Risk-assessment Á Impact scoring Á Environmental impact classification for Alien Taxa Á Socio-economic impact classification of Alien Taxa Á Pet trade Electronic supplementary material The online version of this article (

Using public surveys to rapidly profile biological invasions in hard‐to‐monitor areas

“…None of the competing models included different or significant predictors. The reported impacts on ecosystems included “competition with Indian bullfrog ( Hoplobatrachus tigerinus )” (which is non‐native and invasive in Madagascar but commonly consumed by local communities; Mohanty et al ., 2021) and general concern for environmental degradation, often related to the “decline of snakes”, which was sometimes considered as the only positive effect ( n = 14). The best model – with no competing models – indicated that the perception of invasive toads as an ecosystem threat was reported more frequently by men ( B = 0.79; SE = 0.37; P = 0.032) and less frequently in urban communities ( B = −1.53; SE = 0.62; P = 0.014) (Fig.…”

Using the 2020 global pandemic as a springboard to highlight the need for amphibian conservation in eastern Asia

“…Similar issues have been expressed about the possibilities of other species becoming invasive. For instance, in the Philippines and in the Malaysian states of Sabah and Sarawak in Borneo, H. rugulosus is a non-native species commercially farmed for the food trade as well as for fishing bait and aquaculture feed ( Das, 2011 ; Das et al, 2014 ; Sy, 2014 ), despite the climate of the area being adequate for invasions by the species ( Mohanty et al, 2020 ). Additionally, Chinese giant salamanders that were released in Japan after being farmed for food, now hybridise with the native Japanese giant salamanders ( Andrias japonicus ) and threaten their genetic integrity ( Fukumoto et al, 2015 ; Wang, 2015 ).…”

Attempted predation of an Andaman Bronzeback (Dendrelaphis andamanensis) by an Indian Bullfrog (Hoplobatrachus tigerinus) on Havelock Island, Andaman and Nicobar Islands, India

“…The Indian Bullfrog (Hoplobatrachus tigerinus) is widely distributed in southern Asia, occurring in Nepal, Bhutan, and Myanmar through Bangladesh and India to Pakistan and Afghanistan (Frost 2021). Hoplobatrachus tigerinus has characteristics that make it a likely candidate for invasion success (Mohanty et al 2021), and introduced populations occur in Madagascar (Glaw and Vences 2007) and possibly in the Maldives (Dutta 1997) and Laccadive Islands (Gardiner 1906). The species also was introduced recently to the Andaman and Nicobar Islands by some farmers from West Bengal, who released them into rice fields in Mayabunder, Middle Andamans, from which they rapidly spread, mediated largely by humans (Harikrishnan and Vasudevan 2013;Rangaswamy et al 2014;Mohanty and Measey 2019b).…”