TY - JOUR
T1 - Hatchling Australian freshwater crocodiles rapidly learn to avoid toxic invasive cane toads
AU - Somaweera, Ruchira
AU - Webb, Jonathan K.
AU - Brown, Gregory P.
AU - Shine, Richard P.
PY - 2011/5/30
Y1 - 2011/5/30
N2 - Predicting the ecological impacts of invasive species on native fauna is a formidable challenge for conservation biologists. One way to deal with that challenge is to stage encounters between the invader and native species in the laboratory, to illuminate likely outcomes of encounters in the wild. The invasion of the highly toxic cane toad Rhinella marina across tropical Australia threatens many frog-eating predators, including freshwater crocodiles (Crocodylus johnstoni). To predict the impact of cane toads on crocodiles, we need to know whether crocodiles will attack cane toads, and whether predators that survive the toads' poisons will learn to avoid toads. We quantified these traits under laboratory conditions in hatchling freshwater crocodiles from Lake Argyle in Western Australia. All toad-naïve hatchling crocodiles attacked toads during their first encounter, and none showed signs of overt illness after consuming toads. However, crocodiles rapidly learnt to avoid toads as prey, and only four out of the 10 crocodiles attacked toads during subsequent encounters. Compared to control (toadnaïve) conspecifics, toad-smart crocodiles inflicted fewer bites on toads, held toads in their mouths for shorter time periods, and were more likely to reject toads as prey. In the field, toads were consumed more rarely than native frogs. Our results show that hatchling freshwater crocodiles can rapidly learn to avoid cane toads as prey. Hence, even if toads cause mortality of larger crocodiles (as happens in some areas), populations may recover via hatchling recruitment.
AB - Predicting the ecological impacts of invasive species on native fauna is a formidable challenge for conservation biologists. One way to deal with that challenge is to stage encounters between the invader and native species in the laboratory, to illuminate likely outcomes of encounters in the wild. The invasion of the highly toxic cane toad Rhinella marina across tropical Australia threatens many frog-eating predators, including freshwater crocodiles (Crocodylus johnstoni). To predict the impact of cane toads on crocodiles, we need to know whether crocodiles will attack cane toads, and whether predators that survive the toads' poisons will learn to avoid toads. We quantified these traits under laboratory conditions in hatchling freshwater crocodiles from Lake Argyle in Western Australia. All toad-naïve hatchling crocodiles attacked toads during their first encounter, and none showed signs of overt illness after consuming toads. However, crocodiles rapidly learnt to avoid toads as prey, and only four out of the 10 crocodiles attacked toads during subsequent encounters. Compared to control (toadnaïve) conspecifics, toad-smart crocodiles inflicted fewer bites on toads, held toads in their mouths for shorter time periods, and were more likely to reject toads as prey. In the field, toads were consumed more rarely than native frogs. Our results show that hatchling freshwater crocodiles can rapidly learn to avoid cane toads as prey. Hence, even if toads cause mortality of larger crocodiles (as happens in some areas), populations may recover via hatchling recruitment.
KW - aversion learning
KW - Bufo marinus
KW - Bufonidae
KW - invasive
KW - predator-prey
UR - http://www.scopus.com/inward/record.url?scp=79957492751&partnerID=8YFLogxK
U2 - 10.1163/000579511X565763
DO - 10.1163/000579511X565763
M3 - Article
AN - SCOPUS:79957492751
SN - 0005-7959
VL - 148
SP - 501
EP - 517
JO - Behaviour
JF - Behaviour
IS - 4
ER -