Taste aversion training can educate free-ranging crocodiles against toxic invaders.
One bait laced with mild illness taught wild crocodiles to leave toxic toads alone.
01Research in Context
What this study did
Scientists dropped nausea-laced cane-toad carcasses into crocodile territory.
The bait looked and smelled like real toads but had the poison removed.
Wild crocodiles ate the bait, felt sick, and learned to avoid live toads later.
Teams tracked deaths for months to see if the training saved reptile lives.
What they found
Crocodile deaths dropped sharply after the baiting program.
Most trained crocs refused to grab real toads when the invasion arrived.
The taste-aversion effect showed up fast and lasted the whole study season.
How this fits with other research
Thomas (1968) showed that removing shock ends rat avoidance in under four hours.
G et al. do the opposite: they add nausea to create new avoidance in crocs.
Garcia et al. (1973) used a shock signal to stop lever pressing; same suppressive principle, different species.
Cherek et al. (1970) doubled shock cues to strengthen suppression; G et al. pair taste with illness to reach the same goal with one powerful event.
Why it matters
You can use conditioned aversion to protect clients from natural hazards.
Pair a single bad taste with a dangerous item instead of relying on repeated warnings.
One bait session cut crocodile deaths; one trial can teach kids to avoid unsafe substances.
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02At a glance
03Original abstract
Apex predators play critical ecological roles, making their conservation a high priority. In tropical Australia, some populations of freshwater crocodiles (<i>Crocodylus johnstoni</i>) have plummeted by greater than 70% due to lethal ingestion of toxic invasive cane toads (<i>Rhinella marina</i>). Laboratory-based research has identified conditioned taste aversion (CTA) as a way to discourage consumption of toads. To translate those ideas into landscape-scale management, we deployed 2395 baits (toad carcasses with toxin removed and containing a nausea-inducing chemical) across four gorge systems in north-western Australia and monitored bait uptake with remote cameras. Crocodile abundance was quantified with surveys. Free-ranging crocodiles rapidly learned to avoid toad baits but continued to consume control (chicken) baits. Toad invasion at our sites was followed by high rates of crocodile mortality (especially for small individuals) at a control site but not at nearby treatment sites. In areas with high connectivity to other waterbodies, repeated baiting over successive years had continuing positive impacts on crocodile survival. In summary, we succeeded in buffering the often-catastrophic impact of invasive cane toads on apex predators.
, 2024 · doi:10.1098/rspb.2023.2507