Indigo, N. L. | bioRxiv Science

bioRxiv2018

Bangers and cash: Baiting efficiency in a heterogeneous population.

O_LIContext: The uptake of baits is a key variable in management actions aimed at the vaccination, training, or control of many vertebrate species. Increasingly, however, it is appreciated that individuals of the target species vary in their likelihood of taking baits. To optimise a baiting program, then, we require knowledge, not only on the rate of bait uptake, and how this changes with bait availability, but also knowledge on the proportion of the target population that will take a bait.\nC_LIO_LIThe invasive cane toad (Rhinella marina) is a major threat to northern quolls (Dasyurus hallucatus), which are poisoned when they attack this novel toxic prey item. Conditioned taste aversion baits (cane toad sausages) can be delivered in the field to train individual northern quolls to avoid toads.\nC_LIO_LIMethods: Here we report on a large-scale field trial across eleven sites across one large property in Western Australia. Camera trapping and statistical modelling was used to estimate the proportion of baitable animals in the population, and the proportion of these that were baited at varying bait availabilities.\nC_LIO_LIResults: Population estimates varied at each site from 3.5 ({+/-}0.76 SD) to 18 ({+/-} 1.58 SD) individual quolls per site, resulting in a range across sites of 0.6-4 baits available per individual. Bait uptake increased with increasing bait availability.\nC_LIO_LIWe also estimate that only 62% of individual quolls are baitable, and that a baiting rate of 3 baits per individual (rather than per area) will result in almost all of these baitable individuals being treated.\nC_LIO_LIWe compared our statistical method with prior data informing the probability of being baitable; and with probability of being baitable set to 1; this resulted in largely differing estimates in relation to an appropriate baiting rate.\nC_LIO_LISynthesis and applications: Data and models such as ours provide wildlife managers with information critical to informed decision making and are fundamental to estimate the cost-efficiency of any baiting campaign.\nC_LI

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bioRxiv2017

Not such silly sausages: Northern quolls exhibit aversion to toads after training with toad sausages.

The invasion of toxic cane toads (Rhinella marina) is a major threat to northern quolls (Dasyurus hallucatus) which are poisoned when they attack this novel prey item. Quolls are now endangered as a consequence of the toad invasion. Conditioned taste aversion can be used to train individual quolls to avoid toads, but we currently lack a training technique that can be used at a landscape scale to buffer entire populations from toad impact. Broad scale deployment requires a bait that can be used for training, but there is no guarantee that such a bait will ultimately elicit aversion to toads. Here we test a manufactured bait--a toad sausage--for its ability to elicit aversion to toads in northern quolls. To do this, we exposed one group of quolls to a toad sausage and another to a control sausage and compared the quolls predatory responses when presented with a dead adult toad. Captive quolls that consumed a single toad sausage showed substantially reduced interest in cane toads, interacting with them for less than half the time of their untrained counterparts and showing substantially reduced attack behaviour. We also quantified bait uptake in the field, by both quolls and non-target species. These field trials showed that wild quolls were the most frequent species attracted to the baits, and that approximately 61% of quolls consumed toad-aversion baits when first encountered. Between 40-68% of these animals developed aversion to further bait consumption. Our results suggest that toad-aversion sausages can be used to train wild quolls to avoid cane toads. This opens the possibility for broad-scale quoll training with toad aversion sausages: a technique that may allow wildlife managers to prevent quoll extinctions at a landscape scale.

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