It's a dog-eat-croc world: Dingo predation on the nests of freshwater crocodiles in tropical Australia

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Journal Article
Ecological Research, 2011, 26 (5), pp. 957 - 967
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Predation on eggs is an important source of mortality for many long-lived organisms, but causes of egg mortality from specific predators remain poorly known in most cases. Understanding the identity of predators, and the rates and determinants of their effects on a cohort of recruits, can provide a valuable background for attempts to exploit, control or conserve populations. We used remotely triggered cameras to study predation on the nests of freshwater crocodiles (Crocodylus johnstoni) inhabiting Lake Argyle, in tropical Australia. We also supplemented our work on natural crocodile nests with artificial nests. Overall, 80 of 111 natural nests were opened by predators, and predation occurred throughout the study period (7 weeks). Unlike in other parts of the species' range, most nest-robbers were dingoes (Canis lupus dingo, responsible for 98% of all predator visits in the northern sites, and 54% in the Ord River site), with minimal additional predation by reptiles and birds. Contrary to expectation, rates of nest predation were not influenced by spatial clumping of nests: the probability of predation per nest did not change with total numbers of nests laid in an area, and artificially aggregated versus dispersed nests experienced similar levels of predation. Nest vulnerability was linked to abiotic features including slope of surrounding banks, compactness of nesting substrate, and distance from the nearest forest. Abundant aquatic food resources support a large crocodile population, but a lack of suitable nest-sites forces the crocodiles to concentrate nesting in small areas readily accessible to wide-ranging nest predators. Collectively, our results suggest that distinctive attributes of the lakeside landscape alter predator guilds and fashion unique predator-prey interactions. © 2011 The Ecological Society of Japan.
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