DOI: 10.5061/dryad.pc866t1qm
title: Toxin cues affect cannibalism responses of cane toad tadpoles

description: In many species cannibalism is uncommon and involves non-selective
 consumption of conspecifics as well as heterospecifics. However, within
 their invasive Australian range cane toad larvae (Rhinella marina)
 specifically target and voraciously consume the eggs and hatchlings of
 conspecifics, often extirpating entire clutches. In contrast, toad larvae
 rarely consume the eggs and hatchlings of native frogs. Here, we use
 laboratory studies to demonstrate that this selective consumption is
 triggered by species-specific chemical cues: maternally-invested
 bufadienolide toxins that otherwise defend cane toad eggs and hatchlings
 against predators. We find that these cues stimulate feeding behaviors in
 toad tadpoles, such that the addition of bufadienolide toxins to the water
 column increases predation on eggs, not only of conspecifics, but also of
 native anuran species that are otherwise usually ignored. In contrast, we
 find that cannibalism rates on conspecific hatchlings are high and
 unaffected by the addition of bufadienolide cues. The maternally-invested
 toxins present in conspecific eggs may therefore be more easily detected
 post-hatching, at which point tadpole feeding behaviors are induced
 whether or not additional toxin cues are present. As bufadienolide cues
 have previously been found to attract toad tadpoles to vulnerable
 hatchlings, our present findings demonstrate that the same toxin cues that
 attract cannibalistic tadpoles also induce them to feed, thereby
 facilitating cannibalism through multiple behavioral effects. Because
 native fauna do not produce bufadienolide toxins, the species-specificity
 of these chemical cues in the Australian landscape may have facilitated
 the evolution of targeted (species-specific) cannibalism in invasive cane
 toad populations. Thus, producing bufadienalide toxins confers a cost
 (increased vulnerability to cannibalism in early life-stages) as well as a
 benefit (reduced vulnerability to predation by other taxa).
description: The data are from a series of laboratory experiments conducted in
 Australia, where eggs/hatchlings of invasive cane toads
 (<em>Rhinella marina</em>) and a native frog
 (<em>Litoria tornieri</em>) were exposed to a predatory cane
 toad tadpole in the absence versus presence of toxin (bufadienolide) cues.
 The response variable was the number of eggs/hatchlings consumed. Data
 were analysed as a binomial response to treatment.
description: The data provided are the raw data as collected during the
 experiments. When we analysed the data, there were several instances where
 the models failed to reach convergence due to 100% survival in the Control
 treament. To account for this and obtain a conservative estimate of
 effect, we allocated one tadpole to have died in the Control treatment.
 Specifically, we did this for: Experiment 1 C.
 albogutata (TadPresent versus TadAbsent), P. ornatum (TadPresent versus
 TadAbsent), R.marina (TadPresent versus TadAbsent)
 Experiment 2 Egg stage 14 analysis (toxin absent versus
 present). Details of these adjustments are given in our
 manuscript and in the attached README file. To follow our analyses in
 these specific instances, others need to make these adjustments.
 Also, note that the data sheet "Expt 2 Toad Egg-Hatchling
 Data" has data for both number of eggs eaten/not eaten and number of
 hatchlings eaten/not eaten. Thus, while eggs were developing and not yet
 hatched in this data set, the columns for TotalNSurvivingAtHatching,
 HatchlingsEaten and HatchlingsNotEaten are not relevant because eggs have
 yet to reach the hatchling stage (i.e., there are no hatchling data). In
 these instances, the cells for TotalNSurvivingAtHatching, HatchlingsEaten
 and HatchlingsNotEaten are filled with "n/a" (not
 applicable).