Free-living gerbils with higher testosterone take fewer risks.

Among the physiological differences between the sexes are circulating androgen levels. Testosterone (T) is an androgen that has been linked to aggression and risk-taking in male vertebrates, so that males with higher T are generally more aggressive and take more risks. In females, T is not often measured, and its relationship with behaviour has been less studied.

Social behaviour and foraging success of little egrets (Egretta garzetta).

Intraspecific interactions among predators can change the game between a predator and its prey. Individuals of different size or sex can differ in their responses to conspecific competitors. We studied intraspecific interactions among pairs of little egrets (Egretta garzetta) while foraging on responsive prey (comet goldfish, Carassius auratus).

The Enemy Within: How Does a Bacterium Inhibit the Foraging Aptitude and Risk Management Behavior of Allenby's Gerbils?

AbstractMicrobes inhabiting multicellular organisms have complex, often subtle effects on their hosts. are commonly infected with -like bacteria, which may cause mild nutrient (choline, arginine) deficiencies. However, are there more serious ecological consequences of infection, such as effects on foraging aptitudes and risk management? We tested two alternatives: the nutrient compensation hypothesis (does nutrient deficiency induce infected gerbils to make up for the shortfall by foraging more and taking greater risks?) and (2) the lethargy hypothesis (do sick gerbils forage less, and are they compromised in their ability to detect predators or risky microhabitats?).

The context dependence of non-consumptive predator effects.

Non-consumptive predator effects (NCEs) are now widely recognised for their capacity to shape ecosystem structure and function. Yet, forecasting the propagation of these predator-induced trait changes through particular communities remains a challenge. Accordingly, focusing on plasticity in prey anti-predator behaviours, we conceptualise the multi-stage process by which predators trigger direct and indirect NCEs, review and distil potential drivers of contingencies into three key categories (properties of the prey, predator and setting), and then provide a general framework for predicting both the nature and strength of direct NCEs.

Cancer Community Ecology.

Here we advocate as a valuable focus of study in . We hypothesize that the heterogeneity and characteristics of cancer cells within tumors should vary systematically in space and time and that cancer cells form local ecological communities within tumors. These communities possess limited numbers of species determined by local conditions, with each species in a community possessing predictable traits that enable them to cope with their particular environment and coexist with each other.

Ninja owl; Gerbils over-anticipate an unexpected flying predator.

Foragers make decisions based on cues, information collected from their environment, processed into strategic behaviours. This information, processed in multiple regions of the brain, ultimately result in the production of stress hormones and visible changes in behaviour of animals - both reflexively to avoid depredation and strategically to avoid an encounter with the predator. In a common-garden experiment we tested how imperfect information from visual cues of a predator impacts foraging and apprehension of a desert rodent, the Egyptian gerbil (Gerbillus pyramidum).

Intercontinental test of constraint-breaking adaptations: Testing behavioural plasticity in the face of a predator with novel hunting strategies.

Constraint-breaking adaptations are evolutionary tools that provide a mechanism for incumbent-replacement between species filling similar ecological roles. In common-garden experiments, we exposed populations of two desert rodents to two different viper species, testing their ability to adjust to novel predators that use different hunting strategies. We aimed to understand whether both predators and prey with constraint-breaking adaptations actually manifest comparative advantage over their counterparts.

Ecology of Leishmaniasis in an urbanized landscape: Relationship of sand fly densities, and Leishmania tropica infection rates with reservoir host colonies.

Urbanization may influence the transmission of leishmaniasis, which is as a serious public health issue in Palestine. Semi urban environments can provide suitable habitats for the reservoir host species and the vector sand flies to create favorable condition for disease transmission. This study was aimed to evaluating the effect of distance from hyrax (reservoir host) colonies on sand fly (vector) abundance and its relationship to Leishmania infection within a semi urban landscape.

The spatial and temporal distribution, species composition, and host preference of phlebotomine sand flies in the Bethlehem District of Palestine.

In the Palestinian West Bank, leishmaniasis is emerging as a serious public health issue with incidence increasing over time, especially in the western and the northern parts. This study was aimed to evaluating the effect of altitude on sand fly density, temporal and spatial distribution, species composition, and host preference within and between three villages in the Bethlehem District. The three villages occur along an elevation cline, ranging from the disease-free area of Kisan (KIS; 732-782 m ASL), down to the endemic areas of Arab Ar-Rashaiyda (AAR; 522-568 m ASL), and Al'Azazma (AZA; 473-510 m ASL) in the Bethlehem District (southeastern West Bank).

Does intraspecific competition among Allenby's gerbils lead to an Ideal Free Distribution across foraging patches?

Employing the Ideal Free Distribution (IFD) principle as a tool, we investigated how Allenby's gerbils (Gerbillus andersoni allenbyi) utilized food patches within and moved between connected quadrants (i.e., 'habitats') in a large outdoor semi-natural enclosure.

Individual willingness to leave a safe refuge and the trade-off between food and safety: a test with social fish.

Refuges offer prey animals protection from predation, but increased time spent hiding can reduce foraging opportunities. Within social groups, individuals vary in their refuge use and willingness to forage in the presence of a predator. Here, we examine the relative foraging benefits and mortality costs associated with individual refuge use and foraging behaviour within groups of goldfish (Carassius auratus) under predation risk from an avian predator (little egret-Egretta garzetta).

Time to revisit? A predator's previous successes and failures in prey capture determine its return time to patches.

In a heterogeneous environment containing multiple patches that may deplete and renew, a forager should be able to detect the quality of food resources within and among patches and choose to exploit them to best maximize returns. From the predator's perspective, the behavioral responses of the prey in a patch will be perceived as depletion when they retreat to refuge and renewal when they reemerge. A predator encountering responsive prey should manage predation risk, and thus behavioral resource depression, by optimally timing its return time to the patch based on prey behavior.

Comparing Plasticity of Response to Perceived Risk in the Textbook Example of Convergent Evolution of Desert Rodents and Their Predators; a Manipulative Study Employing the Landscape of Fear.

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.

State-dependent foraging among social fish in a risky environment.

In the presence of a predator, foraging is a dangerous task. Social individuals can respond to risk by forming groups, benefiting from enhanced collective anti-predator behavior but suffering from increased conspicuousness to predators. Within groups, individuals exhibit variable foraging behavior.

Defense by exploitation in Negev gerbils.

In this study, we addressed how frequently a non-traplining animal should visit food patches. More specifically, we investigate if non-traplining animals engage in a behavior called "defense by exploitation", which is characterized by an increase in visitation rates with increased intra-specific competition. We ran four tests with two gerbil species in the Negev Desert.

Divergent behavior amid convergent evolution: A case of four desert rodents learning to respond to known and novel vipers.

Desert communities world-wide are used as natural laboratories for the study of convergent evolution, yet inferences drawn from such studies are necessarily indirect. Here, we brought desert organisms together (rodents and vipers) from two deserts (Mojave and Negev). Both predators and prey in the Mojave have adaptations that give them competitive advantage compared to their middle-eastern counterparts.

Binary patch assessment by goldfish under safe and dangerous conditions.

Food resources can occur heterogeneously in space or time and differ in their abundances. A forager should be able to determine the value of a patch and choose optimally how to exploit it. However, patch choice and exploitation may be influenced by predation risk.

Can we predict the success of a parasite to colonise an invasive host?

To understand whether a parasite can exploit a novel invasive host species, we measured reproductive performance (number of eggs per female per day, egg size, development rate and size of new imagoes) of fleas from the Negev desert in Israel (two host generalists, Synosternus cleopatrae and Xenopsylla ramesis, and a host specialist, Parapulex chephrenis) when they exploited either a local murid host (Gerbillus andersoni, Meriones crassus and Acomys cahirinus) or two alien hosts (North American heteromyids, Chaetodipus penicillatus and Dipodomys merriami). We asked whether (1) reproductive performance of a flea differs between an alien and a characteristic hosts and (2) this difference is greater in a host specialist than in host generalists. The three fleas performed poorly on alien hosts as compared to local hosts, but the pattern of performance differed both among fleas and within fleas between alien hosts.

How does the presence of a conspecific individual change the behavioral game that a predator plays with its prey?

Behavioral games predators play among themselves may have profound effects on behavioral games predators play with their prey. We studied the behavioral game between predators and prey within the framework of social foraging among predators. We tested how conspecific interactions among predators (little egret) change the predator-prey behavioral game and foraging success.

A predator equalizes rate of capture of a schooling prey in a patchy environment.

Prey individuals are often distributed heterogeneously in the environment, and their abundances and relative availabilities vary among patches. A foraging predator should maximize energetic gains by selectively choosing patches with higher prey density. However, catching behaviorally responsive and group-forming prey in patchy environments can be a challenge for predators.

Everybody loses: intraspecific competition induces tragedy of the commons in Allenby's gerbils.

Interference competition may lead to a tragedy of the commons in which individuals driven by self-interest reduce the fitness of the entire group. We investigated this hypothesis in Allenby's gerbils, Gerbillus andersoni allenbyi, by comparing foraging behaviors of single vs. pairs of gerbils.

The Effect of a Whey Protein Supplement on Bone Mass in Older Caucasian Adults.

Context: It has been assumed that the increase in urine calcium (Ca) that accompanies an increase in dietary protein was due to increased bone resorption. However, studies using stable Ca isotopes have found that dietary protein increases Ca absorption without increasing bone resorption.

Objective: The objective of the study was to investigate the impact of a moderately high protein diet on bone mineral density (BMD).

Zoonotic disease in a peripheral population: persistence and transmission of Leishmania major in a putative sink-source system in the Negev Highlands, Israel.

Populations at the edge of their geographic distributions are referred to as peripheral populations. Very little attention has been given to this topic in the context of persistence of infectious disease in natural populations. In this study, we examined this question using zoonotic cutaneous leishmaniasis (ZCL) caused by Leishmania major in the Negev Desert of Israel as a model system.

To dare or not to dare? Risk management by owls in a predator-prey foraging game.

In a foraging game, predators must catch elusive prey while avoiding injury. Predators manage their hunting success with behavioral tools such as habitat selection, time allocation, and perhaps daring-the willingness to risk injury to increase hunting success. A predator's level of daring should be state dependent: the hungrier it is, the more it should be willing to risk injury to better capture prey.

What do predators really want? The role of gerbil energetic state in determining prey choice by Barn Owls.

In predator-prey foraging games, predators should respond to variations in prey state. The value of energy for the prey changes depending on season. Prey in a low energetic state and/or in a reproductive state should invest more in foraging and tolerate higher predation risk.