Shifts in the foraging tactics of crocodiles following invasion by toxic prey

Aiyer, Abhilasha; Shine, Richard; Somaweera, Ruchira; Bell, Tina L.; Ward‐Fear, Georgia

doi:10.1038/s41598-021-03629-6

Cited by 5 publications

(1 citation statement)

References 35 publications

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“…In yet another fascinating project taking place in Western Australia, scientists are working to teach lizards, crocodiles, and other species not to eat the highly toxic cane toads that are moving into their habitat. Through a program of 'conditioned taste aversion', in which predators are exposed to small toads or cane toad sausages that make them very ill but do not kill them, they learn to steer clear of these animals (Ward-Fear et al 2020;Aiyer et al 2022).…”

Section: Introductionmentioning

confidence: 99%

Worlds of Meaning at the Edge of Extinction: Conservation Behaviour and the Environmental Humanities

van Dooren

2023

Humanities

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We are living in the midst of a period of mass extinction. All around us, diverse species of animals and plants are disappearing, often largely unnoticed. However, this is also a period in which, on a daily basis, new and fascinating insights into animal life are emerging as we come to appreciate more about their remarkable perceptual, cognitive, social, and emotional lives. This article explores this strange juxtaposition of loss and knowledge-making and the many challenges and possibilities that it gives rise to. It focuses on the emerging field of Conservation Behaviour in which researchers are seeking to modify or manipulate animal behaviours to achieve conservation outcomes: for example, teaching lizards not to eat toxic prey, or birds to utilise a safer migratory route. The article seeks to bring this approach to conservation into dialogue with work in environmental humanities, including the emerging paradigm of conservation humanities. The article outlines an interdisciplinary environmental humanities approach to conservation behaviour, grounded in work in multispecies studies and philosophical ethology. It then explores four broad thematic areas—agency, identity, ethics, and loss—in which the dialogue between these two fields might prove to be particularly, and mutually, enriching.

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Section: Introductionmentioning

confidence: 99%

Worlds of Meaning at the Edge of Extinction: Conservation Behaviour and the Environmental Humanities

van Dooren

2023

Humanities

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Imperfect adaptation by freshwater crocodiles to the invasion of a toxic prey species

Letnic,

Dempster,

Jessop

et al. 2024

Biol Invasions

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Novel interactions between invaders and native species that have evolved in their absence may impose strong selective pressures that drive species to extinction or prompt rapid co-evolution and learning. Here, we report on the effects that invasive cane toads, a toxic prey species, have had on freshwater crocodile populations in 7 waterholes of the Victoria River, Australia, before and up to 14 years after toads invaded. We recorded observations of crocodiles attacking toads, dissected dead crocodiles to determine if they had eaten toads and indexed the abundances of cane toads, live crocodiles and dead crocodiles. Following toad-invasion we observed crocodiles attacking cane toads. Dead crocodiles were only observed following the invasion of toads and 62% of the 71 dead crocodiles we dissected had toads in their stomachs. Counts of dead crocodiles showed a humped relationship with time since toad invasion and declined markedly after 3 years post-toad invasion. Live crocodile abundance declined sharply following toad-invasion, but this decline attenuated approximately 4 years post-invasion. The pulse of crocodile mortality and attenuation of the rate of crocodile population decline suggests that crocodiles have evolved or learned to enable co-existence with toads. However, crocodile populations have shown no sign of recovery in the 8–14 years post toad invasion. Our findings highlight that adaptation by native species to the presence of invaders may be imperfect and thus may not necessarily entail numerical recovery of populations to pre-invasion levels, but instead downward shifts to new equilibria due to ongoing interactions with invaders.

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Acute impacts of invasive toads on the population demography of a native predator in tropical Australia

Ward-Fear,

Brown,

Shine

2024

Biol Invasions

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If an animal’s size, age and/or sex influence its vulnerability to an invasive species, the arrival of such an invader can cause rapid changes in the population demography of an affected species. We studied free-ranging varanid lizards (Yellow-spotted monitors, Varanus panoptes) at a site in tropical Australia during the influx of fatally toxic cane toads, Rhinella marina. Mortality was inferred from shifts in population structure, as well as the survival rates (time to death) of 107 radio-tracked lizards. Of 57 deaths whose cause was unambiguous, 32 were due to fatal poisoning by ingesting a cane toad; the other 25 lizards were consumed by pythons. Size and age structure shifted between years, such that the population post-invasion was dominated by smaller, younger lizards, and by females rather than males. Radiotelemetric monitoring confirmed that survival rates were reduced more in males than in females in the post-toad year, with males most at risk late in the dry-season, when food was scarce and females were nesting rather than foraging. Pythons disproportionately consumed larger female lizards during the nesting season. Toad-induced poisoning of adult male varanids (which are larger and bolder than females) likely produced a population that was more resilient to toad impact, but less easily surveyed by conventional techniques.

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Shifts in the foraging tactics of crocodiles following invasion by toxic prey

Cited by 5 publications

References 35 publications

Worlds of Meaning at the Edge of Extinction: Conservation Behaviour and the Environmental Humanities

Worlds of Meaning at the Edge of Extinction: Conservation Behaviour and the Environmental Humanities

Imperfect adaptation by freshwater crocodiles to the invasion of a toxic prey species

Acute impacts of invasive toads on the population demography of a native predator in tropical Australia

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