Taste aversion training can educate free-ranging crocodiles against toxic invaders

Apex predators play critical ecological roles, making their conservation a high priority. In tropical Australia, some populations of freshwater crocodiles (Crocodylus johnstoni) have plummeted by >70% due to lethal ingestion of toxic invasive cane toads (Rhinella marina). 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 2,395 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 con..., This data was recorded during baiting trials run in the wild to test the effectiveness of taste aversion training with freshwater crocodiles. The data has had minimal processing but was collected and analysed as below.
Eliciting taste aversion
Baiting trials were conducted all sites in September and October of 2021. We ran a repeat baiting at Bandiln͟gan sites 1 and 2 in September 2022 (but not other sites), to explore the longevity of our intervention in a large population experiencing toads for the first time. We also wanted to clarify population dynamics between years at dry-season waterbodies in this important gorge ecosystem, which would allow us to design future conservation protocols. Trials were timed to coincide with late dry-season peak overlap between crocodiles and toads, when pools were relatively isolated. Based on our spotlight counts just prior to trials, we calculated the number of bait stations required in each area to keep the ratio of crocodiles to bait stations belo..., , # Freshwater Crocodile CTA trial Data

[https://doi.org/10.5061/dryad.qjq2bvqq5](https://doi.org/10.5061/dryad.qjq2bvqq5)

For the most part, this is a dataset of bait offtake records by freshwater crocodiles over a five day trial period. Baits were replenished each day and we checked offtake each morning. We offered a choice of chicken or cane toad baits on day 1 and 5, otherwise only toad baits offered at each station every day. This enabled us to test whether crocodiles were eating less cane toad baits over time and also whether this was an active avoidance of cane toad baits (versus control chicken baits). Trials were run in multiple, independent gorge systems. Crocodiles did show avoidance of cane toad baits by the end of the trials, however the strength of this was associated with how 'open' the environment was and the density of crocodiles within it. We also monitored death rates pre- and post- baiting. Within this dataset are the records of crocodile mortality which showed that ...

顶级捕食者在生态系统中发挥着至关重要的调控作用，因此对其开展保护工作被列为优先级极高的任务。在澳大利亚热带区域，部分淡水鳄（约翰斯顿鳄，Crocodylus johnstoni）种群数量骤降超70%，诱因是其误食了具有毒性的入侵性海蟾蜍（Rhinella marina）。已有实验室研究证实，条件性味觉厌恶（conditioned taste aversion, CTA）可有效抑制鳄类捕食蟾蜍。为将该研究成果转化为景观尺度的管理方案，我们在澳大利亚西北部的四个峡谷系统中投放了2395份诱饵（已去除毒素且添加致恶心化学物质的蟾蜍尸体），并通过远程相机监测诱饵被取食情况。同时通过调查量化鳄类种群丰度。自由活动的野生淡水鳄迅速学会了规避蟾蜍诱饵，但仍会取食对照诱饵（鸡肉诱饵）。在我们的研究样地中，海蟾蜍入侵后，对照样地的淡水鳄死亡率显著升高（尤以小型个体为甚），而邻近的处理样地未出现该情况。在高[内容未完成]区域，本数据集记录了野外诱饵投放试验中的相关数据，旨在检验针对淡水鳄的条件性味觉厌恶训练方案的有效性。该数据集仅经过极少处理，其采集与分析流程如下。

诱导味觉厌恶：
诱饵投放试验于2021年9月至10月在所有样地开展。我们于2022年9月对Bandiln͟gan的1号和2号样地重复开展了诱饵投放试验（其余样地未重复），以探究该干预措施在首次遭遇蟾蜍的大种群中的持续效果。同时，我们希望明确该重要峡谷生态系统中旱季水体的年际种群动态，以此为未来的保护规程设计提供依据。试验时间选定在旱季末期鳄类与蟾蜍的活动峰值重叠期，此时各水塘相对隔离。根据试验前的聚光灯计数结果，我们计算了各区域所需的诱饵站数量，以将鳄类与诱饵站的比例控制在[内容未完成]。

# 淡水鳄条件性味觉厌恶试验数据集
https://doi.org/10.5061/dryad.qjq2bvqq5

总体而言，本数据集涵盖了为期5天的诱饵取食试验中淡水鳄的取食记录。每日均会补充诱饵，并于每日清晨检查取食情况。试验第1天和第5天提供鸡肉诱饵与蟾蜍诱饵供其选择，其余日期仅投放蟾蜍诱饵。该设计可用于检验鳄类随时间推移是否减少了蟾蜍诱饵的取食，以及这种取食行为变化是否属于主动规避蟾蜍诱饵（相较于对照鸡肉诱饵）。试验在多个独立的峡谷系统中开展。结果显示，试验结束时鳄类确实表现出对蟾蜍诱饵的规避行为，但其规避强度与环境的“开放程度”及区域内鳄类种群密度相关。我们同时监测了诱饵投放前后的死亡率。本数据集包含鳄类死亡记录，结果显示[内容未完成]。