Sonny S Bleicher

Foragers process information they gain from their surroundings to assess the risk from predators and balance it with the resources in their environment. Measuring these perceived risks from the perspective of the forager can produce a heatmap or their "fear" in the environments, a so-called "landscape of fear" (LOF). In an intercontinental comparison of rodents from the Mojave and Negev Deserts, we set to compare families that are used regularly as examples of convergent evolution, heteromyid and gerbilline respectively. Using a LOF spatial-analysis on data collected from common garden experiments in a semi-natural arena we asked: (1) do all four species understand the risk similarly in the exact same physical environment; (2) does relative relation between species affect the way species draw their LOFs, or does the evolutionary niche of a species have a greater impact on its LOF?; and (3) does predator facilitation between vipers and barn owls cause similar changes to the shape of the measured LOFs. For stronger comparative power we mapped the LOF of the rodents under two levels of risk: low risk (snakes only) and high risk (snakes and barn owls). We found concordance in the way all four species assessed risk in the arena. However, the patterns observed in the LOFs of each rodent family were different, and the way the topographic shape of the LOF changed when owls were introduced varied by species. Specifically, gerbils were more sensitive to owl-related risk than snakes and at the opposite correct for heteromyids. Our findings suggest that the community and environment in which a species evolved has a strong impact on the strategies said animals employ. We also conclude, that given the homogenous landscape we provide in our arena and the non-homogenous patterns of LOF maps, risk assessment can be independent of the physical conditions under which the animals find themselves.

To study how wildlife perceive recreating humans, we studied the habitat selection of a human commensalist, the collared peccary (Pecari tajacu (Linnaeus, 1758)). We measured peccary activity patterns in an area of high human activity (Tumamoc Hill Desert Laboratory in Tucson, Arizona, USA) using a landscape-of-fear analysis. We examined whether the perception of risk from human activity interacted with the chemical (tannin) and mechanical (thorns) antipredator mechanisms of local plant species. The peccaries avoided food stations near a hiking trail. The population foraged less near houses, i.e., moderate human activity, than in the perceived safety of a small wadi. Plant defence treatments impacted the harvesting of food only in the safe zone, suggesting that risk trumps food selectivity. The strong effect of the hiking trail on habitat selection in this disturbance-loving species is an indicator of a much larger impact on sensitive species in conservation areas. Résumé : Pour étudier la perception qu'ont les animaux sauvages d'usagers récréatifs, nous avons étudié la sélection d'habitats d'une espèce vivant en commensalisme avec les humains, le pécari à collier (Pecari tajacu (Linnaeus, 1758)). Nous avons mesuré les habitudes d'activité de pécaris dans une région de forte activité humaine (le laboratoire du désert de Tumamoc Hill à Tucson, en Arizona (États-Unis)) en utilisant une analyse de la topographie-de-la-peur. Nous avons vérifié si la perception du risque associé à l'activité humaine interagit avec les mécanismes anti-prédation tant chimiques (tannin) que mécaniques (épines) d'espèces de plantes locales. Les pécaris évitaient les stations de nourriture près d'un sentier de randonnée pédestre. La population s'approvisionnait moins à côté des maisons, c'est-à-dire près d'une activité humaine modérée, qu'à proximité d'un petit oued, un lieu perçu comme étant plus sûr. Les traitements de défense des plantes n'avaient d'incidence sur la collecte de nourriture que dans la zone sûre, ce qui indiquerait que le risque représente une considération plus importante que la sélectivité des aliments. La découverte principale de cette recherche fut l'impact inattendu du sentier de randonnée sur le comportement de cette espèce qui en principe aime les perturbations. C'est pourquoi leur comportement représente un indicateur de cet impact utilisable sur des espèces plus sensibles à l'activité humaine dans les aires de conservation. [Traduit par la Rédaction]

Sidewinders (Crotalus cerastes) and Saharan horned vipers (Cerastes cerastes) have evolved to hunt desert rodents on different continents in evolutionarily independent communities. These species are remarkably convergent, except that sidewinders possess heat-sensitive pit organs that enable them to "see" in the dark. As a constraint-breaking adaptation, this may give sidewinders an advantage when hunting in the dark. How will introducing a novel predator with a constraint-breaking adaptation affect the local species? We allowed Saharan horned vipers to hunt Allenby's gerbils (Gerbillus andersoni allenbyi) in patches with or without sidewinders at full and new moon. When horned vipers hunted alone, moonlight did not affect their foraging behavior. However, in the presence of sidewinders, horned vipers increased their activity on bright nights, but dramatically decreased it on dark nights. Although gerbils foraged equally when hunted by either snake, the combined effect of the 2 predators synergistically decreased gerbil foraging, especially during full moon when both snakes were most active. Thus, sidewinders facilitated horned vipers in full moon, but interfered on darker nights when possessing pit organs were most advantageous for sidewinders. Gerbils quickly learned and adjusted their behavior to manage risks from the novel predators, but the combined effects of both local and novel predators may prove detrimental in the long run. Comparing convergent species that differ in a constraint-breaking adaptation allows us to study the effectiveness of these key adaptations and their potential roles in biological invasions.

Predator-Prey dynamics, and their trophic impacts, have functioned as a focal point in both community and population biology for five decades. The work-group focusing on these dynamics has however largely changed the focus of their work from trophic effects to the study of non-consumptive effects of predation-the " ecology of fear ". An increasing number of studies chose to spatially chart wildlife populations' risk assessment and of those the majority use optimal patch-use (giving-up densities) as a continuous measure of fear. These charts, " landscapes-of-fear " (LOFs) originated in conservation literature and the reintroduction of wolves to Yellowstone. Today, they are used to study population habitat selection and venture into the evolutionary context with studies examining the mechanisms by which species coexist in the same physical space. This review predicts increase in, and encourages the use of, LOFs: as a conservation tool to assess species land-use; as a bridge between ecology and neurology with stress hormones as indicators fear; and as a tool to compare species' evolutionary dynamics within a community context. PeerJ Preprints | https://doi.org/10.7287/peerj.preprints.2840v1 | CC BY 4.0

Desert rodent assemblages from around the world provide convergent, but independent crucibles for testing theory and deducing general ecological principles. The heteromyid rodents of North America and the gerbils of the Middle East and their predators provide such an example. Both sets of rodents face predation from owls and vipers, but the North American species possess unique traits that may represent macroevolutionary breakthroughs: rattlesnakes have infra-red sensitive sensory pits, and heteromyids have cheek pouches. To test their significance, we brought together two gerbils (Middle East), two heteromyid rodents (a kangaroo rat and a pocket mouse; North America) in a common setting (a vivarium in the Negev Desert), and quantified the “opinions” of the rodents towards the North American sidewinder rattlesnake and the Middle Eastern Saharan horned viper and the foraging behavior of each in the face of these snake predators plus owl predators. Gerbils are fairly evenly matched in their anti-predator abilities, while the heteromyids differ widely, and these seem to match well with and may determine the types of mechanisms of species coexistence that operate in the communities of each continent. Evolutionary history, macroevolutionary traits, and risk management therefore combine to determine the characteristics of the organisms and the organization of their communities.

Ph.D. dissertation involving experiments testing the response of four convergent desert rodents to vipers of both the Mojave and Negev deserts. Bio-assays in form of "interview chamber" experiments showed that all four rodent species were able to identify pit vipers, that can "see" in the dark, as a greater risk than horned vipers. In common garden experiments each of the four rodent species responded using different predator evasion strategies.