Responses Of Prey Species Research Articles

Fear and stressing in predator-prey ecology: considering the twin stressors of predators and people on mammals.

Predators induce stress in prey and can have beneficial effects in ecosystems, but can also have negative effects on biodiversity if they are overabundant or have been introduced. The growth of human populations is, at the same time, causing degradation of natural habitats and increasing interaction rates of humans with wildlife, such that conservation management routinely considers the effects of human disturbance as tantamount to or surpassing those of predators. The need to simultaneously manage both of these threats is particularly acute in urban areas that are, increasingly, being recognized as global hotspots of wildlife activity. Pressures from altered predator–prey interactions and human activity may each initiate fear responses in prey species above those that are triggered by natural stressors in ecosystems. If fear responses are experienced by prey at elevated levels, on top of responses to multiple environmental stressors, chronic stress impacts may occur. Despite common knowledge of the negative effects of stress, however, it is rare that stress management is considered in conservation, except in intensive ex situ situations such as in captive breeding facilities or zoos. We propose that mitigation of stress impacts on wildlife is crucial for preserving biodiversity, especially as the value of habitats within urban areas increases. As such, we highlight the need for future studies to consider fear and stress in predator–prey ecology to preserve both biodiversity and ecosystem functioning, especially in areas where human disturbance occurs. We suggest, in particular, that non-invasive in situ investigations of endocrinology and ethology be partnered in conservation planning with surveys of habitat resources to incorporate and reduce the effects of fear and stress on wildlife.

An invasive amphibian drives antipredator responses in two prey at different trophic positions

Abstract Generalist invasive predators consume prey at different trophic levels and generate drastic changes in local communities. However, the long-term effects of predation may be reduced by eco-evolutionary responses of native populations. The capacity of prey species distributed across the trophic network to develop antipredator responses may determine the ecosystem potential to buffer against the invader. The African clawed frog is a major invader on several continents. Because of its large size, generalist diet, and aquatic lifestyle, we predicted the development of antipredator responses in prey species at different trophic levels. We tested for behavioral shifts between populations within and outside the invasive range in the herbivorous snail Physella acuta and the predatory heteropteran, the backswimmer Notonecta glauca. We detected antipredator responses in both prey species. In sympatry, P. acuta stayed higher in the water column, while N. glauca spent more time swimming underwater and less time surfacing when the predator cues were present. In allopatry, P. acuta dived deeper and N. glauca spent more time surfacing and stayed longer still underwater. In both species, sympatric populations showed evidence of olfactory recognition of the frog. Our results show that the introduction of a top predator like Xenopus laevis in the pond ecosystem drives behavioral antipredator responses in species across the trophic network. Eco-evolutionary processes may allow some degree of long-term resilience of pond communities to the invasion of X. laevis.

Short-term thermal responses after exposure to predator odor (TMT) in the house mouse

Exposure to predator cues is believed to induce fear-like responses in prey species and compounds found in the smells of predators, such as TMT (2,5-dihydro-2,4,5-trimethylthiazole) are frequently used to induce such responses. While behavioral changes of rodents after exposure to TMT have been well characterized, only few studies described the associated sympathetic responses. Here, we used non-invasive infrared thermography to assess short-term and fine-scale changes in peripheral body temperature of wild-origin house mice (Mus musculus domesticus) subjected to TMT. Peripheral temperature changes are associated with blood flow regulation occurring when mammals are subjected to emotion-eliciting situations. Our results revealed that confrontation to TMT induced clear peripheral thermal responses characterized by a significant increase in tail temperature and in the maximum peripheral body temperature. The increase in tail temperature is not the typical physiological stress response expected when mice are exposed to a fear-eliciting situation. In addition, mice did not express typical defensive behaviors such as freezing and avoidance. These results suggest that in our experimental conditions, TMT, as an indirect, chemical predator cue, induced arousal rather than fear. In conclusion, this study stresses the need for a deeper exploration of the behavioral and physiological response to predator odors to better understand the emotional responses they induce.

Habitat odor can alleviate innate stress responses in mice

Predatory odors, which can induce innate fear and stress responses in prey species, are frequently used in the development of animal models for several psychiatric diseases including post-traumatic stress disorder (PTSD) following a life-threatening event. We have previously shown that odors can be divided into at least three types; odors that act as (1) innate stressors, (2) as innate relaxants, or (3) have no innate effects on stress responses. Here, we attempted to verify whether an artificial odor, which had no innate effect on predatory odor-induced stress, could alleviate stress if experienced in early life as a habitat odor. In the current study, we demonstrated that the innate responses were changed to counteract stress following a postnatal experience. Moreover, we suggest that inhibitory circuits involved in stress-related neuronal networks and the concentrations of norepinephrine in the hippocampus may be crucial in alleviating stress induced by the predatory odor. Overall, these findings may be important for understanding the mechanisms involved in differential odor responses and also for the development of pharmacotherapeutic interventions that can alleviate stress in illnesses like PTSD.

Predator-avoidance behavior in anuran tadpoles: a new bioassay for characterization of water-soluble cues

In freshwater systems, little is known about the characteristics of chemical cues derived from predators which induce defensive responses in prey species. To elucidate traits of predator chemical cues, we examined chemical cues originating from water incubated by the nymph of the dragonfly Anax parthenope julius, which induces low activity as predator-avoidance behavior in tadpoles of two anuran species, the Japanese tree frog Hyla japonica and the winkled frog Rana (Rugosa) rugosa. H. japonica exhibited a reduction in tail movement time as low activity in response to both untreated incubation water and incubation water that had volatile substances removed by freeze-drying. The response threshold of R. rugosa to chemical cues was determined to be one dragonfly nymph in a water volume between 500 and 5,000 ml. We found that chemical cues inducing predator-avoidance behavior in anuran tadpoles have water-soluble non-volatile characteristics. In this study, we devised both the bioassay to assess the effects of chemical cues and the method to enrich the cues by freeze-drying, which can serve as a tool in the process of identification of unknown chemical cues in freshwater predator-prey interaction.

Oviposition habitat selection in response to risk of predation in temporary pools: mode of detection and consistency across experimental venue.

Natural selection should favor females that avoid ovipositing where risk of predation is high for their progeny. Despite the large consequences of such oviposition behavior for individual fitness, population dynamics, and community structure, relatively few studies have tested for this behavior. Moreover, these studies have rarely assessed the mode of detection of predators, compared responses in prey species that vary in vulnerability to predators, or tested for the behavior in natural habitats. In an outdoor artificial pool experiment, we tested the oviposition responses of two dipteran species, Culiseta longiareolata (mosquito) and Chironomus riparius (midge), to the hemipteran predator, Notonecta maculata. Both dipteran species have similar life history characteristics, but Culiseta longiareolata larvae are highly vulnerable to predation by Notonecta, while Chironomus riparius larvae are not. As their vulnerabilities would suggest, Culiseta longiareolata, but not Chironomus riparius, strongly avoided ovipositing in pools containing Notonecta. An experiment in natural rock pools assessing oviposition by Culiseta longiareolata in response to Notonecta maculata yielded an oviposition pattern highly consistent with that of the artificial pool experiment. We also demonstrated that the cue for oviposition avoidance by Culiseta longiareolata was a predator-released chemical: Notonecta water (without Notonecta replenishment) repelled oviposition for 8 days. Oviposition avoidance and mode of detection of the predator have important implications for how to assess the true impact of predators and for the use of commercially produced kairomones for mosquito control.