Conditioned food aversion mediated by odour cue and microencapsulated levamisole to avoid predation by canids

Abstract

Worldwide, predators and humans are in conflict for resources such as game species or livestock, especially in the case of medium-large wild canids. One non-lethal method to reduce predation is conditioned food aversion (CFA), in which animals learn to avoid a food due to the illness after its ingestion, caused by the addition of an undetected chemical compound. Food aversion can be enhanced by adding an artificial odour cue, in a process known as taste-potentiated odour aversion (TPOA). We carried out an experiment on penned dogs with three experimental groups to test CFA and TPOA. We offered the food mixed with a combination of microencapsulated levamisole + vanilla odour (ODO), microencapsulated levamisole (LEV), and plain food as a control. The aims were: a) to test whether dogs are able to detect the microencapsulated levamisole; b) to analyse the strength and extinction of CFA induced by microencapsulated levamisole; c) to analyse the strength and extinction of TPOA. Two-choice tests were carried out during 11 months in the post-conditioning phase, and two reinforcements with microencapsulated levamisole were done during the first month. In the first post-conditioning test, ODO and LEV groups ate significantly less untreated food than control group. After the reinforcement, suddenly the dogs in LEV group started to eat the food. Three of four dogs in ODO group showed longlasting CFA until the 11 th month. These results show that TPOA could be used to induce odour aversion on canids and that the odour cue overshadows the slight bitter taste of microencapsulated levamisole.These results open new possibilities to develop TPOA as tool to reduce predation by wild canids.

Conditioned food aversion in domestic dogs induced by thiram

“…Contrary to studies with other aversive substances reporting that an odor cue can enhance the food rejection, here with thiram the TH group showed stronger aversion than the THO group. Recently, we showed an enhanced aversion in penned dogs using levamisole plus an odor cue, increasing the strength and time to extinction in a taste‐potentiated odor aversion procedure. It has been suggested that the strong flavor of levamisole acted as a strong cue enhancing the aversion to the weaker cue, the vanilla odor .…”

“…Recently, we showed an enhanced aversion in penned dogs using levamisole plus an odor cue, increasing the strength and time to extinction in a taste‐potentiated odor aversion procedure. It has been suggested that the strong flavor of levamisole acted as a strong cue enhancing the aversion to the weaker cue, the vanilla odor . Differences to the results of the present study could be explained because thiram was apparently not detected by dogs, acting both the food taste and odor as weak cues of the conditioning process.…”

“…Second, combination with ion‐exchange resins has been used to mask the bitter taste of levamisole, but the results in the field are not conclusive yet . Microencapsulation has been also suggested to mask the flavor of the chemical compounds, but the few attempts so far made have not achieved good results . Nevertheless, new formulations of microencapsulation are being developed and promise to offer better characteristics to mask strong flavors …”

“…Another possibility suggested to protect livestock from wild canid predation is taste‐potentiated odor aversion . In this case the aversion is created to an artificial odor cue rather than to the food taste .…”

Conditioned odor aversion as a tool for reducing post‐release predation during animal translocations

“…CFA can be induced deliberately by adding a chemical substance to the food or prey desired to be protected from predation in order to produce rejection by the predator (Gustavson et al ., 1974; Cowan et al ., 2000; O’Donnell, Webb & Shine, 2010). Recent studies carried out with captive dogs Canis familiaris and Iberian wolves Canis lupus signatus have shown the possibility of creating aversion by adding an artificial odor cue during conditioning (Tobajas et al ., 2019 a ; Tobajas et al ., unpublished data), thus, creating an enhanced aversion to that odor rather than to the food itself (Tobajas et al ., 2019 b ). This enables the predator to detect that a prey is noxious at a distance (Rusiniak et al ., 1979), and makes it possible to employ this disruptive effect caused by the odor aversion to stop predation during predatory behavior (Tobajas et al ., 2019 b ; Tobajas et al ., unpublished data).…”