Ecological immunization: in situ training of free-ranging predatory lizards reduces their vulnerability to invasive toxic prey

Abstract

In Australia, large native predators are fatally poisoned when they ingest invasive cane toads (Rhinella marina). As a result, the spread of cane toads has caused catastrophic population declines in these predators. Immediately prior to the arrival of toads at a floodplain in the Kimberley region, we induced conditioned taste aversion in free-ranging varanid lizards (Varanus panoptes), by offering them small cane toads. By the end of the 18-month study, only one of 31 untrained lizards had survived longer than 110 days, compared to more than half (nine of 16) of trained lizards; the maximum known survival of a trained lizard in the presence of toads was 482 days. In situ aversion training (releasing small toads in advance of the main invasion front) offers a logistically simple and feasible way to buffer the impact of invasive toads on apex predators.

The ecological and life history correlates of boldness in free‐ranging lizards

“…Response to novel prey.-Prior to the arrival of invasive cane toads (Rhinella marina) in our study area, we approached lizards and offered them a small toad at the end of a line attached to a fishing rod, as part of a study on conditioned taste aversion (see Ward-Fear et al 2016). We scored the response of each goanna to this novel prey item as follows: 0 = immediately moved away; 1 = investigated the prey item but did not eat it; and 2 = ate the prey item.…”

“…Our study was originally designed to test a novel conservation technique (conditioned taste aversion; see Ward‐Fear et al. ). However, we soon realized that individual goannas possessed unique behavioral profiles, so we compiled behavioral observations for each individual to assess whether:…”

“…In the present paper, we describe the results of a field study in which we recorded behavioral, ecological, and microevolutionary data on free-ranging varanid lizards on a tropical floodplain. Our study was originally designed to test a novel conservation technique (conditioned taste aversion; see Ward-Fear et al 2016). However, we soon realized that individual goannas possessed unique behavioral profiles, so we compiled behavioral observations for each individual to assess whether:…”

No signs of Na+/K+‐ATPase adaptations to an invasive exotic toxic prey in native squamate predators

“…Recently Ward-Fear et al (2016) showed that conditioned taste aversion, using small cane toads, resulted in increased survival of free-ranging yellowspotted goannas suggesting that the trained goannas learned to avoid feeding on large cane toads. The latter result is further supported by study by Jolly et al (2016) that showed when toad-na€ ıve lace monitors where offered euthanised toads from which the parotids glands had been removed (although sufficient amount of toad toxin was still present to elicit illness in the monitors) they subsequently refused to feed on this toxic amphibian.…”

Sharper eyes see shyer lizards: Collaboration with indigenous peoples can alter the outcomes of conservation research

“…We then monitored the survival of CTA-trained versus untrained lizards over the next 18 months and found a major effect of our manipulation. By the end of the study, only 3% of untrained lizards had lived longer than 110 days versus 56% of trained lizards (Ward-Fear, Pearson, Brown, Rangers, & Shine, 2016). The research team included participants from two distinct ethnic backgrounds, which unintentionally produced a case study highlighting social dimensions of conservation research.…”