Relative Predation Risk Research Articles

A retrospective analysis of sea turtle nest depredation patterns

AbstractNest predation can significantly reduce hatchling recruitment in sea turtle populations. We examined 20 yr of data from Canaveral National Seashore, Florida, which has pristine and altered beaches. We used chi‐squared test to determine if secondary predation events were related to the nests' primary predation events, and proportional hazard regression analysis to determine the relative risk of individual nest predation. To determine if human beach use and nest predation risk were spatially or temporally linked, we ranked human beach use and examined predation frequency across all screened and marked nests. We found that once a nest has experienced predation it has an increased likelihood of experiencing a subsequent predation event when compared to other nests on the beach. Primary and multiple predation events occurred with greater frequency in limited beach use areas and with lowest frequency in moderate use areas. Predation risk decreased by an average of 29.5% from 2000 to 2008, relative to the initial year of study. Nests deposited mid‐season were 9.8% more likely to be predated than early or late season nests. We conclude that where anti‐nest predator management efforts are required but restricted (e.g., by funds, available personnel, or multiple management goals) resources should be concentrated to protect mid‐season nests and those in limited access areas, if enhancing hatchling numbers is a management goal. © 2012 The Wildlife Society.

Juvenile Gobius niger avoids seagrass in the presence and uncertain absence of seagrass-inhabiting predators

We performed a series of laboratory tank experiments designed to identify possible mechanisms for the strict seagrass avoidance of juvenile Gobius niger previously observed in their natural habitat, the Novigrad Sea, northern Adriatic. Overall our results suggest that juvenile G. niger strongly prefers seagrass when predator absence is certain, avoids seagrass in the presence of predators, and chooses habitat based on both predator identity and on the degree of certainty of predator presence or absence. In the presence of predators, juvenile G. niger occupies the same habitat as adult size G. niger but avoids the habitat chosen by Zosterisessor ophiocephalus. Juvenile G. niger is most likely to switch habitat in response to addition or removal of Z. ophiocephalus, the predator with the stronger seagrass preference. A significantly lower likelihood of selecting seagrass was exhibited when predator absence was uncertain than when predator absence was certain. Our results suggest that juvenile G. niger identifies predators by species and responds differentially to perceived risk posed by each predator through differential habitat selection, which also depends on the certainty of predator absence. These results are consistent with the hypothesis that the importance of structured refuge habitats, such as seagrass, is relative: it depends on both the prey's perception of the relative predation risk posed by multiple predators in alternative habitats, and on the prey's specific antipredator response strategies. These responses could explain the avoidance of seagrass by G. niger in the Novigrad Sea.

How avian nest site selection responds to predation risk: testing an ‘adaptive peak hypothesis’

1. Nest predation limits avian fitness, so birds should favour nest sites that minimize predation risk. Nevertheless, preferred nest microhabitat features are often uncorrelated with apparent variation in predation rates. 2. This lack of congruence between theory-based expectation and empirical data may arise when birds already occupy 'adaptive peaks'. If birds nest exclusively in low-predation microhabitats, microhabitat and nest predation may no longer be correlated even though predation ultimately shaped microhabitat selection. 3. This 'adaptive peak hypothesis' was tested for a population of Yellow Warblers (Dendroica petechia) focusing on two nest microhabitat features: concealment and height. Experimental nests measured relative predation risk both within and outside the microhabitat range typically occupied by natural nests to examine whether nest site choices made by birds restricted our ability to detect microhabitat effects on predation. 4. Within the natural range (30-80% concealment, >75 cm height), microhabitat-predation relationships were weak and inconsistent, and similar for experimental and natural nests. Over an extended range, however, experimental predation rates were elevated in exposed sites (<30% concealed), indicating a concealment-related 'adaptive plateau'. 5. Clay egg bite data revealed a concealment effect on avian predators, and the abundance of one avian predator group correlated with nest concealment among years, suggesting these predators may cue birds to modulate nest concealment choices. 6. This study demonstrates how avian responses to predation pressure can obscure the adaptive significance of nest site selection, so predation influences may be more important than apparent from published data.

Milk composition in mares fed a fat and fiber-added concentrate

Livestock guarding dogs (LGDs) are utilized worldwide as a non-lethal strategy to alleviate human-wildlife conflict. However, while studies show their effectiveness, resulting in reductions of livestock loss, there is limited research into the factors that influence individual dog variation. One factor which may be important is the proximity of the dog to the herd it is guarding, as well as subtle aspects of its behavior. This small-scale study investigates individual differences in proximity and behavior and the potential influencing environmental factors. It compares these to the dog's perceived effectiveness, as rated by the herder who regularly works with them. We attached GPS collars to 8 LGDs and a ‘lead’ goat from their respective herd to track proximity during grazing visits to the Namibian bush. For 4 dogs, the data spanned 2 years, so we examined consistency of proximity, both within, and between, years. We also examined associations between temperature, time of day and vegetation density and the LGD's proximity to the herd. In addition, behavioral observations were conducted for 3 of the dogs to compare to the data derived from the collars. Individual dogs varied in their proximity to the herd and showed consistency within (F(7,4180)=36.8, P < 0.001) and between the 2 years (r=0.99. P = 0.012). Proximity was significantly associated with time of day (F(1,4180)=19.3, P < 0.001), but not with daily temperature (F(1,4180) = 0.003, P = 0.96). Dogs tended to be closer to the herd at the start and end of the day. Whilst vegetation density did not have a universal effect (F(2,4180) = 0.99, P = 0.393), some dogs showed distinct patterns of change in proximity with differences in vegetation density (F(14,4180) = 3.60, P < 0.01). This suggests some dogs were modifying their behavior in response to relative predation risk. The herder tended to rate those dogs, which were recorded to be closest, as more effective. Behavioral observations of distance correlated well with the data gathered from GPS collars but, in most cases, the dog was observed to be closer to other herd members than to the collared lead goat. We conclude that measuring dog proximity to the herd is a useful way to monitor behavior, but that monitoring multiple sheep or goats, and also conducting behavioral observations is integral to understanding ways to maximize performance.

Minimizing predation risk in a landscape of multiple predators: effects on the spatial distribution of African ungulates

Studies that focus on single predator-prey interactions can be inadequate for understanding antipredator responses in multi-predator systems. Yet there is still a general lack of information about the strategies of prey to minimize predation risk from multiple predators at the landscape level. Here we examined the distribution of seven African ungulate species in the fenced Karongwe Game Reserve (KGR), South Africa, as a function of predation risk from all large carnivore species (lion, leopard, cheetah, African wild dog, and spotted hyena). Using observed kill data, we generated ungulate-specific predictions of relative predation risk and of riskiness of habitats. To determine how ungulates minimize predation risk at the landscape level, we explicitly tested five hypotheses consisting of strategies that reduce the probability of encountering predators, and the probability of being killed. All ungulate species avoided risky habitats, and most selected safer habitats, thus reducing their probability of being killed. To reduce the probability of encountering predators, most of the smaller prey species (impala, warthog, waterbuck, kudu) avoided the space use of all predators, while the larger species (wildebeest, zebra, giraffe) only avoided areas where lion and leopard space use were high. The strength of avoidance for the space use of predators generally did not correspond to the relative predation threat from those predators. Instead, ungulates used a simpler behavioral rule of avoiding the activity areas of sit-and-pursue predators (lion and leopard), but not those of cursorial predators (cheetah and African wild dog). In general, selection and avoidance of habitats was stronger than avoidance of the predator activity areas. We expect similar decision rules to drive the distribution pattern of ungulates in other African savannas and in other multi-predator systems, especially where predators differ in their hunting modes.

Suitability of Artificial Nests—Response

Faaborg presents a valid concern that artificial nests should not be used to infer real nest success. For our study, we chose artificial nests to provide a controlled measure of relative predation risk across latitudes, not to infer real nest success. In real nests, success is not determined by

Relative predation risk for fishes along a subtropical mangrove–seagrass ecotone

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 401:259-267 (2010) - DOI: https://doi.org/10.3354/meps08449 Relative predation risk for fishes along a subtropical mangrove–seagrass ecotone Neil Hammerschlag1,*, Annie B. Morgan1, Joseph E. Serafy1,2 1Rosenstiel School of Marine and Atmospheric Science, University of Miami, 4600 Rickenbacker Causeway, Miami, Florida 33149, USA 2National Oceanic and Atmospheric Administration, National Marine Fisheries Service, Southeast Fisheries Science Center, 75 Virginia Beach Drive, Miami, Florida 33149, USA *Email: nhammerschlag@rsmas.miami.edu ABSTRACT: Many fishes shelter in mangrove habitats by day and forage mostly in seagrass beds by night. This pattern of diel habitat use has been attributed to a predator avoidance strategy, whereby predation risk is reduced by alternating between the cover afforded by prop-roots during the day and darkness at night. We employed a series of diel tethering experiments in Biscayne Bay (Florida, USA) to empirically examine whether relative predation pressure on fishes is lower at night than during the day and to compare relative predation pressure on fishes at different distances from the mangrove– seagrass ecotone. Pinfish Lagodon rhomboides ranging from 10 to 17 cm in total length were tethered during day and night at 10, 50, and 110 m from the mangrove–seagrass ecotone. Pinfish removal rates at night were twice as high as during the day, which contradicts the idea that darkness provides ‘cover’ during nocturnal foraging in seagrass. Predation losses were highest nearest the mangrove edge and decreased with increasing distance from shore. Our results agree with those of other tethering studies that marine ecotones, or transition zones between refuges and feeding sites, can be areas of high predation pressure for fishes. KEY WORDS: Predators · Edge effects · Proximity gradient · Shark · Snapper · Porgy · Grunt Full text in pdf format PreviousNextCite this article as: Hammerschlag N, Morgan AB, Serafy JE (2010) Relative predation risk for fishes along a subtropical mangrove–seagrass ecotone. Mar Ecol Prog Ser 401:259-267. https://doi.org/10.3354/meps08449Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 401. Online publication date: February 22, 2010 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2010 Inter-Research.

Alpine marmots (Marmota marmota) adjust vigilance behaviour according to environmental characteristics of their surrounding

Predation risk can strongly affect behaviour of preys, and natural selection should have favoured the evolution of behavioural plasticity in the strategies used to avoid predation. The level of predation risk can be affected by environmental characteristics and we expect individuals to adjust vigilance behaviour to the level of risk. In this study we investigate if Alpine marmots (Marmota marmota) living in an area delimited by the forest and with scarce visibility (Closed Site) differ in their vigilance behaviour from marmots inhabiting an open meadow further away from the forest edge and with greater visibility (Open Site). The rate of vigilance and the time spent vigilant in the Closed Site were higher than in the Open Site, while the mean duration of each vigilance bout did not differ between the two sites. Our results suggest that Alpine marmots adjust vigilance behaviour according to the environmental characteristics of their surroundings while there appears to exist an optimal duration of scan bouts which is independent of relative predation risk.

Predator-Specific Mortality of Pronghorn on Yellowstone's Northern Range

Yellowstone National Park supports a small population (<300) of pronghorn (Antilocapra americana). Some individuals migrate during summer to areas characterized by reduced visibility, mixed habitat types, and a diverse predator community. Across areas selected by migratory and nonmigratory pronghorn, we documented cause-specific mortality of adults and fawns and assessed relative risk of predation by various predators. Coyotes (Canis latrans) accounted for 56% of adult predation and up to 79% of fawn predation. Cougars (Puma concolor) and wolves (Canis lupus) accounted for additional predation of adults, while cougars, black bears (Ursus americanus), and Golden Eagles (Aquila chrysaetos) were documented killing fawns on rare occasions. Our results suggest that even when pronghorn are in the presence of multiple predator species, coyote predation on adults and fawns may predominate for populations inhabiting shrubsteppe habitat. However, the risk of predation by sympatric predators, particularly cougars, may be high for female pronghorn selecting mixed cover types during migration or for birthing purposes. While the direct effect of wolves on overall mortality was low, wolves may indirectly influence survival rates of adult females and fawns by altering the behavior and space use of sympatric predators, particularly coyotes.

Does predation risk influence habitat use by northern redbelly dacePhoxinus eosat different spatial scales?

This study investigated the relationship between spatial variations in predation risk and abundance of northern redbelly dace Phoxinus eos at both macroscale (littoral v. pelagic zones) and microscale (structured v. open water habitats in the littoral zone) of Canadian Shield lakes. Minnow traps were placed in both structured and open water habitats in the littoral zone of 13 Canadian Shield lakes, and estimates of the relative predation risk of P. eos in both the pelagic and the littoral zones were obtained from tethering experiments. Results showed that (1) the mean abundance of P. eos in the littoral zone was positively correlated with the relative predation risk in the pelagic zone, (2) P. eos preferentially used structured over open water habitats in the littoral zone and (3) this preference was not related to the relative predation risk in the littoral zone but decreased as the relative predation risk increased in the pelagic zone. At the lake level, these results support the hypothesis that P. eos enter the littoral zone to avoid pelagic piscivores. At the littoral zone level, the results do not necessarily contradict the widely accepted view that P. eos preferentially use structured over open habitats to reduce their predation risk, but suggest that flexibility in antipredator tactics (e.g. shelter use v. shoaling) could explain the spatial distribution of P. eos between structured and open water habitats.

Optimal escape theory predicts escape behaviors beyond flight initiation distance: risk assessment and escape by striped plateau lizards Sceloporus virgatus

Abstract Escape theory predicts that flight initiation distance (FID = distance between predator and prey when escape begins) is longer when risk is greater and shorter when escape is more costly. A few tests suggest that escape theory applies to distance fled. Escape models have not addressed stochastic variables, such as probability of fleeing and of entering refuge, but their economic logic might be applicable. Experiments on several risk factors in the lizard Sceloporus virgatus confirmed all predictions for the above escape variables. FID was greater when approach was faster and more direct, for lizards on ground than on trees, for lizards rarely exposed to humans, for the second of two approaches, and when the predator turned toward lizards rather than away. Lizards fled further during rapid and second consecutive approaches. They were more likely to flee when approached directly, when a predator turned toward them, and during second approaches. They were more likely to enter refuge when approached rapidly. A novel finding is that perch height in trees was unrelated to FID because lizards escaped by moving out of sight, then moving up or down unpredictably. These findings add to a growing body of evidence supporting predictions of escape theory for FID and distance fled. They show that two probabilistic aspects of escape are predictable based on relative predation risk levels. Because individuals differ in boldness, the assessed optimal FID and threshold risks for fleeing and entering refuge are exceeded for an increasing proportion of individuals as risk increases.

Differences in reproductive seasonality of the Central American cichlidCichlasoma urophthalmusfrom three ‘cenotes’ (sinkholes)

Summary A total of 966 cichlids, Cichlasoma urophthalmus, was sampled from three karstic water bodies (cenotes) in the Yucatan Peninsula. Sex ratio was not different from 1. Specimens with ripe eggs were found during the dry and rainy seasons in the inland cenote and during the dry, rainy, and north winds seasons in the two wetland cenotes. With respect to relative fecundity, data show the C. urophthalmus inland population as two- to three-fold greater (53.1 ± 27.7) than the wetland populations (15.7 ± 5.1 and 18.2 ± 3.1). This is attributable to the different breeding strategies of C. urophthalmus populations inhabiting these two types of cenotes. In particular, the ichthyofauna from the two wetlands showed not only higher species richness (17 and 16 species) but also a higher number of potential predators (nine and eight species) as compared to the inland cenote (six species; two potential predators). It is hypothesized that C. urophthalmus adjusts its clutch size and extends its breeding periods as a response to riskier sites as compared to more secure ones; a higher competition for breeding sites and to increased fishing mortality.

The irrelevance of individual discrimination in meerkat alarm calls

Individual discrimination is an important element in the evolution of social behaviour and is particularly important in social living species which show intense intragroup interactions. Numerous previous studies, particularly with nonhuman primates, ground squirrels and marmots, demonstrate the widespread ability of various species to signal and perceive individual identity from vocalizations. The function of individually different alarm calls is thought to assist in the detection of unreliable individuals. This would allow individuals to optimize the benefits of antipredator behaviour by self-assessing the relative predation risk, and responding selectively to reliable callers. In this study we investigated whether meerkats, Suricata suricatta, a social mongoose, discriminated among alarm callers individually, and adjusted their response accordingly. Several parameters of the acoustic structure of meerkat alarm calls were measured and analysed with multivariate statistics. Within groups, the 10-fold cross-validation of a multinomial regression yielded, on average, 90% correct assignment. This strongly suggests that meerkats have individually distinct alarm calls. With a habituation–dishabituation playback experiment, we then tested whether meerkats use this information to discriminate between individual callers. Receivers did not distinguish between different individuals in the playback experiments. In meerkats, unreliable callers appear to be uncommon, and the cost of being predated might exceed the costs of responding to an unreliable caller, thus rendering a reliability-based discrimination mechanism unnecessary. Although meerkat alarm calls contain information on individual identity, this information does not appear to be important to the receivers in this context.

Water depth modifies relative predation risk for a motile fish taxon in Bahamian tidal creeks

We evaluated the influence of water depth on relative predation risk for mojarra (Eucinostomus spp.) in six tidal creeks on Andros Island, Bahamas. Relative predation risk was determined using a tethering protocol combined with underwater visual census. In one experiment, we found that relative predation risk increased predictably with water depth (r2 = 0.83), and survival of tethered mojarra decreased with water depth (r2 = 0.71). We identified three depth zones containing differing levels of predation threat: refugia (0–19 cm), transition (20–69 cm), and predation (> 70 cm). Predation on mojarra rarely occurred within the refugia zone (2% eaten) and always in the predation zone (100% eaten). Additional factors not examined in this study (e.g., mangrove complexity, predator density) likely drive variability of relative predation risk within the transition zone. In a second experiment, we directly examined influence of water depth on relative predation risk at fixed locations from high tide to low tide in a single creek. Mean relative predation risk was significantly higher during higher tides at deeper water depths. Results provide experimental evidence that exploitation of shallow water refugia by motile prey can significantly reduce predation risk. We expect the distribution of motile fishes is at least partially influenced by spatially-dynamic shallow water refugia.

Littoral Fish Community Response to Smallmouth Bass Removal from an Adirondack Lake

AbstractLarge‐scale observational studies in eastern Canada and the northeastern USA have concluded that introduced littoral predators are responsible for reductions in native fish diversity and abundance. To determine whether nonnative predator removal could increase native littoral fish abundance, we removed 47,682 smallmouth bass Micropterus dolomieu from a 271‐ha Adirondack lake during a 6‐year period. Two years after removal began, habitat‐stratified snorkel surveys indicated a greater than 90% reduction in smallmouth bass abundance. The relative abundances of six native littoral species increased (4‐90 times preremoval abundances) within 2 years of smallmouth bass removal. Decreased relative predation risk during the experiment reflected the reduction in littoral predators and identified seasonal differences in nearshore predation risk. The smallmouth bass population was resilient to removal, producing strong year‐classes throughout the experiment. Mechanical removal was successful at decreasing smallmouth bass abundance and increasing native fish abundance, but removal must be conducted on a yearly basis to maintain low smallmouth bass population abundance. Our results provide experimental evidence regarding the need to prevent littoral predator introductions in Adirondack waters and offer support for nonnative control wherever native fish species conservation is a management priority.

Comparative Predation on Naturally Occurring Gypsy Moth (Lepidoptera: Lymantriidae) Pupae and Deployed Freeze-Dried Pupae: Table 1.

Predation is an important factor in the dynamics of gypsy moth (Lymantria dispar L.) populations, yet predation rates can be difficult to estimate accurately in the field. Biased estimates can result from spatial heterogeneity in risk or from artifacts associated with deploying prey. Here we compare predation rates on freeze-dried gypsy moth pupae affixed with beeswax to pieces of burlap with predation rates on naturally occurring live pupae in the same sites. Daily predation rates, primarily by small mammals, were two to eight times greater for freeze-dried deployed pupae than natural pupae, depending on the year. These results indicate apparent predation rates can be substantially biased by artifacts associated with deployed prey, such as human scent, artificial substrates, or freeze drying. Results from studies using similar methods may provide qualitative comparisons of relative predation risk, but their estimates of absolute predation rates should be interpreted with caution, and attempts should be made to quantify and correct for any resulting bias.

A quantitative test of the size efficiency hypothesis by means of a physiologically structured model

According to the size‐efficiency hypothesis (SEH) larger bodied cladocerans are better competitors for food than small bodied species. In environments with fish, however, the higher losses of the large bodied species due to size‐selective predation may shift the balance in favor of the small bodied species. Here we present a theoretical framework for the analysis of the competitive abilities of zooplankton species that takes both competition and predation into account in one coherent analysis. By applying the conceptually well‐understood framework of physiologically structured population models we were able to predict the relative difference in predation rates necessary to cause a shift in dominance of the large‐bodied species (Daphnia pulicaria) to the small‐bodied species (D. galeata). These predictions depend only on seven easily interpretable parameters per species: size at birth, size at maturity and maximum size, age at maturity, maximal clutch size, egg development time and finally the half‐saturation constant for food. The critical equilibrium mortality of D. pulicaria was 0.16 d−1 at food concentrations close to the critical food concentration of D. galeata, i.e. D. pulicaria will win the competition as long as its mortality rate is below 0.16 d−1. At higher food concentrations the differential mortality curve (plotting equilibrium mortalities of both species against each other) approached a linear function with a slope of one and an intercept equal to the difference in maximal population birth rates. The prediction of critical predation rates was independent of the ingestion rate of the cladocerans and the algal carrying capacity and food regeneration rate of the environment although the mechanism works through competition for a shared algal food resource. We interpret these findings in terms of the relative predation risk large and small‐bodied cladocerans will face in various freshwater ecosystems.

Variation in fish density, assemblage composition and relative rates of predation among mangrove, seagrass and coral reef habitats

We tested the hypothesis for several Caribbean reef fish species that there is no difference in nursery function among mangrove, seagrass and shallow reef habitat as measured by: (a) patterns of juvenile and adult density, (b) assemblage composition, and (c) relative predation rates. Results indicated that although some mangrove and seagrass sites showed characteristics of nursery habitats, this pattern was weak. While almost half of our mangrove and seagrass sites appeared to hold higher proportions of juvenile fish (all species pooled) than did reef sites, this pattern was significant in only two cases. In addition, only four of the six most abundant and commercially important species (Haemulon flavolineatum, Haemulon sciurus, Lutjanus apodus, Lutjanus mahogoni, Scarus iserti, and Sparisoma aurofrenatum) showed patterns of higher proportions of juvenile fish in mangrove and/or seagrass habitat(s) relative to coral reefs, and were limited to four of nine sites. Faunal similarity between reef and either mangrove or seagrass habitats was low, suggesting little, if any exchange between them. Finally, although relative risk of predation was lower in mangrove/seagrass than in reef habitats, variance in rates was substantial suggesting that not all mangrove/seagrass habitats function equivalently. Specifically, relative risk varied between morning and afternoon, and between sites of similar habitat, yet varied little, in some cases, between habitats (mangrove/seagrass vs. coral reefs). Consequently, our results caution against generalizations that all mangrove and seagrass habitats have nursery function.

Begging and short-term need in cowbird nestlings: how different are brood parasites?

Because brood parasitic nestlings are usually unrelated to their nestmates and to the provisioning adult, they are free from indirect costs of begging. Consequently, they are predicted to beg more intensely than host nestlings, and some models predict they will beg at an invariantly high level, regardless of short-term need. Previous work has shown intense begging by parasitic cowbirds, but short-term need was not controlled. In this study, we manipulated short-term need and measured begging intensity in two species pairs of host and parasitic nestlings: shiny cowbirds (Molothrus bonariensis) parasitizing larger hosts than themselves (rufous-bellied thrushes, Turdus rufiventris), and brown-headed cowbirds (M. ater) parasitizing smaller hosts than themselves (yellow warblers, Dendroica petechia). All four species increased their begging intensity with short-term need, though the change was much less pronounced between food-deprived and control treatments than between control and hand-feeding treatments. Shiny cowbirds begged more intensely than rufous-bellied thrushes following each treatment. In contrast, brown-headed cowbirds did not beg significantly more intensely than yellow warblers under any of the treatments. Intense begging by both species of parasites was as effective as host begging in stimulating the adults to make provisioning visits, but shiny cowbirds were less successful at acquiring food from adult thrushes. A wide array of factors may underlie the apparent differences in the begging behavior and success of brown-headed and shiny cowbirds, including relative size, experience, and local risk of nest predation. Our experiments clearly demonstrate, however, that these two species of parasitic cowbirds adjust their begging intensity based on short-term need.

Differential Avoidance of Snake Odours by a Lizard: Evidence for Prioritized Avoidance Based on Risk

AbstractMost studies of predator avoidance behaviours have focussed on single‐predator systems, despite the fact that prey often are confronted with predator rich environments. In the presence of more than one predator, prey may have to choose between avoiding one predator over another. How prey cope with exposure to several enemies simultaneously remains largely untested. In this study I set out to investigate if skinks showed preferential avoidance of snake odours based on the relative predation risk posed by different snake species. This relative predation risk was estimated using information on density, diet specificity and foraging habit of each snake species. I tested retreat‐site selection in two‐choice tests, where lizards chose between different combinations of control and snake treated retreat‐sites as well as two retreat‐sites treated with different snake species odours. Lizards preferred control–treated retreat‐sites to those treated with snake odours and showed a differential avoidance response to refuges treated with odours from different snake species. There was strong evidence to suggest that lizards preferentially avoided refuges with the odours of the snake that posed the greatest predation risk, the white‐lipped snake (Drysdalia coronoides). Naïve juvenile lizards were also tested and their response was similar to the adults demonstrating that the behaviour is innate and not the result of higher encounter rates of more common snake odours. To my knowledge this is one of the first studies to demonstrate that prey can prioritize avoidance to a single most dangerous predator in the face of several predators and conflicting avoidance responses.