Modeling habituation of introduced predators to unrewarding bird odors for conservation of ground‐nesting shorebirds

Abstract

Foraging mammalian predators face a myriad of odors from potential prey. To be efficient, they must focus on rewarding odors while ignoring consistently unrewarding ones. This may be exploited as a nonlethal conservation tool if predators can be deceived into ignoring odors of vulnerable secondary prey. To explore critical design components and assess the potential gains to prey survival of this technique, we created an individual‐based model that simulated the hunting behavior of three introduced mammalian predators on one of their secondary prey (a migratory shorebird) in the South Island of New Zealand. Within this model, we heuristically assessed the outcome of habituating the predators to human‐deployed unrewarding bird odors before the bird's arrival at their breeding grounds, i.e., the predators were “primed.” Using known home range sizes and probabilities of predators interacting with food lures, our model suggests that wide‐ranging predators should encounter a relatively large number of odor points (between 10 and 115) during 27 d of priming when odor is deployed within high‐resolution grids (100–150 m). Using this information, we then modeled the effect of different habituation curves (exponential and sigmoidal) on the probability of predators depredating shorebird nests. Our results show that important gains in nest survival can be achieved regardless of the shape of the habituation curve, but particularly if predators are fast olfactory learners (exponential curve), and even if some level of dishabituation occurs after prey become available. Predictions from our model can inform the amount and pattern in which olfactory stimuli need to be deployed in the field to optimize encounters by predators, and the relative gains that can be expected from reduced predation pressure on secondary prey under different scenarios of predator learning. Habituating predators to odors of threatened secondary prey may have particular efficacy as a conservation tool in areas where lethal predator control is not possible or ethical, or where even low predator densities can be detrimental to prey survival. Our approach is also relevant for determining interaction probabilities for devices other than odor points, such as bait stations and camera traps.

Leveraging Motivations, Personality, and Sensory Cues for Vertebrate Pest Management

“…Olfactory cues that signal danger, such as predator odour [27] or territorial scent marks [28], can reduce the impacts of pests. Though examples are rare, applying odour cues can change pest behaviour, such as camouflaging native prey to reduce the impacts of invasive predators [29,30] (Figure 1A,iii).…”

Olfactory lures in predator control do not increase predation risk to birds in areas of conservation concern

“…Bird odour could be used sparingly as a novel lure to attract snakes to control devices, especially larger BTS shown to be refractory to mouse lure (Yackel Adams et al 2019). Alternatively, managers could deploy bird odour across the landscape to camouflage endangered birds through olfactory swamping or odour priming (Ruxton 2009;Banks 2012, 2017;Latham et al 2019;Norbury et al 2020).…”

“…However, excessive use of an inaccessible mouse lure could lead to predator demotivation for mouse-lure traps (Price and Banks 2012). The extent of effectiveness for lure traps can inform how olfactory stimuli are distributed in time and space (Latham et al 2019). On Guam this could include the deployment of traps, but also the distribution of bird odours (e.g.…”

Outfoxing the fox: Effect of prey odor on fox behavior in a pastoral landscape

“…This finding is important because it provides a complementary approach to fox management beyond the traditional approach of lethal removal of foxes from the landscape. It may also be applied to other olfactory-led predator species, with recent experimental evidence demonstrating the effectiveness of an olfactory pre-exposure to protect shorebird populations from a range of olfactory mammalian predators in New Zealand (Latham et al, 2019;Norbury et al, 2021;Price et al, 2020). By conditioning the fox to ignore the odors of a prey species, this tactic targets the predator behavior at the point of prey detection, before an encounter occurs (Endler, 1991;Price & Banks, 2012).…”