Prophylactic Mobbing via Chick-a-Dee Calls in Wintering Willow Tits (Poecile montanus)

The Common Redpoll Carduelis flammea is a highly social flocking bird which forms cohesive groups outside the breeding season. Being small birds (12-15g), they need to forage almost continuously during a few hours of daylight in winter to meet their energy demands. Although predation risk is reduced as a result of improved surveillance of many eyes, increased flock size may also increase the agonistic interactions among individuals within the flock and as a consequence lower the probability of detection of a predator’s approach. To examine whether Common Redpolls, living in relatively large winter flocks, are more exposed to avian predators than small passerines living in groups of only a few individuals, I recorded the responses of Common Redpolls, Willow Tits Poecile montanus and Great Tits Parus major to a life-like stuffed specimen of two different predators, the Siberian Jay Perisoreus infaustus (body length 30 cm) and the Hooded Crow Corvus cornix (50 cm). After the presentation of a predator model, Redpolls returned to the seed sites on the average earlier than the tits, and significantly so versus both tit species after exposure to the Siberian Jay, and for Great Tits after exposure to the Hooded Crow. Whereas Willow and Great Tits seemed to pick up sunflower seeds in the snow without much competition, Common Redpolls displayed a more conspicuous, aggressive, intraspecific behaviour. Thus, the individual vigilance of Common Redpolls was most likely reduced and exposure time to predation increased. The seed-eating Common Redpolls may be more food-stressed than the year-round resident Willow Tits that have stored food within their territories. If so, Common Redpolls may be forced to take greater predation risks because of a higher hunger level. If the differences in return times after exposure to a predator model reflected an adaptation to perceived predation risk, the Common Redpolls apparently evaluated the Siberian Jay as less dangerous than did the tits.

Asymmetric information transfer can shape the social structure of animal groups. Birds in mixed-species flocks can gain antipredation benefits by relying on both personal and social information, ultimately increasing their survival. However, not all species in a flock contribute danger-related information equally, leading to complex patterns of information flow between species. Understanding these differences in information flow and usage among species is key to exploring the mechanisms underlying the formation of such social assemblages. In this study, we combined mixed-species flock surveys with playback experiments to investigate the asymmetric information transfer about danger between leader and follower species in the montane forests of Taiwan. The playback experiments included four treatments: predator calls (personal information), leader and follower mobbing calls (social information) and control. We predicted that leader species would be better at detecting threats than follower species and that the mobbing calls of leader species would elicit stronger antipredator responses in mixed-species flocks than those of follower species. As predicted, and more striking than anticipated, leader species were always the first to initiate mobbing calls in response to predator calls, suggesting strong asymmetry in predator detection and/or danger communication between the two species' roles. Moreover, our results showed that birds responded much more strongly to the playback of predator calls than to playback of mobbing calls. Contrary to our prediction, there was not a greater antipredator response to mobbing calls given by leader compared to follower species. Here, we propose that larger conspecific group sizes and associated kin-selected behaviour could drive leader species to develop superior antipredator signalling systems, potentially leading to asymmetric information transfer about predation risk between species. We also suggest that mutual antipredator benefits may be common in mixed mobbing flocks, promoting positive interactions among bird species, and ultimately strengthening the cohesion and formation of mixed flocks.

Understanding animal space us is a fundamental concern in Ecology. Predator-prey interactions are a behavioral response game where predators try to find prey, and prey are trying to avoid the predators, thereby shaping animal space use and habitat selection. In the process both predator and prey tradeoff between risk avoidance and food acquisition in order to maximize their fitness. As such predator-prey dynamics have fascinated many generations of ecologists. At the same time the impact of human activities on ecosystem processes have become increasingly evident over the years and almost all habitats on earth today have been altered to some degree by humans. As a consequence humans can be considered as ecological players of ecosystem processes that shape the behavior and demography of their commensal species. In the presence of humans large top predators may be downgraded in the food chain or compete with humans for their prey. Furthermore prey species themselves have to tradeoff between risk avoidance towards humans or their natural predators. It was the goal of this thesis to look at various aspects involved in shaping the space use patterns of the Eurasian lynx (Lynx lynx) and its main prey, the European roe deer (Capreolus capreolus) and to characterize the spatiotemporal drivers of habitat selection and risk avoidance of both players in a human dominated environment. By focusing on both predators and prey I identify different key components of the behavioral response game between Eurasian lynx and European roe deer. In the first chapter I investigated how tradeoffs between risk avoidance and resource abundance in human-altered environments affect habitat selection of Eurasian lynx. In particular, I studied how spatial scale interacts with the intrinsic behavioral state of Eurasian lynx in shaping the response to temporal and spatial fluctuations in human activity and prey availability. I show that lynx tradeoff between anthropogenic risk and prey density by using areas of high prey density during times of low human disturbance. This tradeoff differs among behavioral states and is dependent on the spatial scale considered. In the second chapter I focused on the prey and tested how lynx and humans interact in shaping space use patterns of roe deer during the hunting season in fall. Multiple predators of a single prey may positively or negatively interact with each other via their prey. The same may be true for human hunters that compete with natural predators for the same prey. I explored how roe deer tradeoff between hunting and lynx predation risk and whether hunting increases the deer’s susceptibility to lynx predation. I found that roe deer avoid areas of high hunting risk during the hunting season at the expense of higher exposure to lynx predation risk. Furthermore there was strong evidence that lynx increased their hunting effort and hunting success during this time period. The results provided strong evidence that hunters facilitated lynx predation which resulted in superadditive mortality for deer during the hunting season. In environments with limited resources and time antipredator behavior may come at costs that ultimately affect prey demography. The strength of such non-consumptive effects (NCE) largely depends on the hunting mode of the predator. Ambush predators exert stronger NCE than active predators as they provide more persistent cues about predation risk than their widely roaming counterparts. While evidence comes from different taxonomic groups, evidence from large mammalian predator-prey systems is rare and equivocal. In the third chapter I looked at the occurrence and strength of NCE of the ambush predator, the Eurasian lynx on its main prey the European roe deer. According to ecological prediction I found that lynx evoked strong NCE that increased non-lynx-related mortality of roe deer in the study area. In summary, I focused in this thesis on identifying key drivers involved in shaping space use patterns of a large ambush predator and one of its main prey. Furthermore I characterized the spatiotemporal drivers of food acquisition and risk avoidance of both players in a human dominated environment. The presented results illustrate the tradeoffs between risk avoidance and food acquisition that affect decision making of all animals and show the potential costs of these tradeoffs in the form of reduced survival or reproduction. Finally the findings highlight the role of humans as ecological drivers of Ecosystem processes and may help developing efficient wildlife management plans that are needed for the conservation of large predators and their prey alike in human altered environements.

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 574:85-95 (2017) - DOI: https://doi.org/10.3354/meps12187 Hunted hunters: an experimental test of the effects of predation risk on juvenile lemon shark habitat use K. L. Stump1,2,*, C. J. Crooks3, M. D. Fitchett4, S. H. Gruber1,2, T. L. Guttridge2 1Department of Marine Biology and Ecology, University of Miami Rostenstiel School of Marine and Atmospheric Science, 4600 Rickenbacker Causeway, Miami, Florida 33149, USA 2Bimini Biological Field Station Foundation, 9300 SW 99th Street, Miami, Florida 33176, USA 3University of Manchester, Oxford Road, Manchester M13 9PL, UK 4Department of Marine Ecosystems and Society, University of Miami Rosenstiel School of Marine and Atmospheric Science, 4600 Rickenbacker Causeway, Miami, Florida 33149, USA *Corresponding author: kristine.stump@gmail.com ABSTRACT: Predation effects can occur either through consumption or as risk effects, which can include alterations in prey behavior to decrease encounters, detection and/or capture by predators. Perceived predation threats lead to behavioral responses which may manifest as changes in habitat use by the prey, and these effects can be significant and even greater in population-level consequences and across multiple trophic levels than consumptive effects. In Bimini, Bahamas, juvenile lemon sharks (Negaprion brevirostris, Poey 1868) use mangrove-fringed shorelines as nursery areas in part due to protection afforded from predators, namely, large conspecifics. We investigated small-scale use (on the order of meters) of artificial mangrove structure by juvenile N. brevirostris as an antipredatory response to perceived predation risk. Controlled experimental trials were conducted on semi-captive individuals to compare the degree to which sharks used artificial subtidal refugia when solitary, with a size-matched conspecific and with a potential predator (large conspecific). Test shark size and predator presence were significant drivers of artificial mangrove use. There was a negative relationship between body size and refuge use in the presence of a predator, indicating that size is an important factor influencing antipredatory behavior. Test sharks exhibited a high degree of social swimming behaviors with size-matched conspecifics, but the presence of a large conspecific predator elicited fright reponses. This study provides the first experimental evidence of the influence of intraspecific predator-prey interactions on juvenile shark habitat use and demonstrates use of subtidal structure as a habitat-specific escape tactic. KEY WORDS: Risk effects · Risk of predation · Habitat loss · Mangroves · Predator-prey interactions · Refuge Full text in pdf format PreviousNextCite this article as: Stump KL, Crooks CJ, Fitchett MD, Gruber SH, Guttridge TL (2017) Hunted hunters: an experimental test of the effects of predation risk on juvenile lemon shark habitat use. Mar Ecol Prog Ser 574:85-95. https://doi.org/10.3354/meps12187 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 574. Online publication date: July 04, 2017 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2017 Inter-Research.

Territorial males may adopt a mating tactic that yields greater reproductive success but that at the same time increases the risk of predation. Plasticity in reproductive behavior can reflect a balance between sexual selection and natural selection. In this study, we sought to verify the effect of predation risk on territorial behavior of males of the solitary bee Ptilothrix fructifera (Apidae). Males of the species employ alternative mating tactics and can be territorial in defense of larval food sources. By manipulating predator models in the field, we tested whether (1) males avoid perch flowers containing predator models; (2) males alternate between mating tactics when their territory is associated with a predation risk; and (3) female foraging on flowers in a territory is altered in the presence of a predator model. We measured the responses of males and females in flowers containing and not containing a model of a spider or a stuffed bird. The results show that territorial males of P. fructifera alter their territorial behavior when faced with a high risk of predation. They do not abandon their territory or change to a non-territorial mating tactic, but instead change the use of their territory, avoiding flowers containing predator models or perching on other flowers when the previous flower presented a potential predation risk. Female P. fructifera decreases the frequency of their visits to flowers and the length of time spent there in the presence of a spider model. In short, in the face of predation risk, females and males alter their behaviors at the cost of less efficient foraging and searching for partners, respectively.

Size-dependent interactions in salt marsh fish (Fundulus heteroclitus Linnaeus) and shrimp (Palaemonetes pugio Holthuis)

Animals develop familiarity with specific areas through repeated use, gaining detailed knowledge of local conditions, such as food availability, predator presence, and landscape features, which can directly impact fitness. While site familiarity has been widely studied in the context of foraging and breeding, no studies have assessed the fitness consequences of using familiar locations near key sleeping sites. Moreover, studies on site familiarity have generally focused solely on predation risk, overlooking the potential influence of harvest. To further our understanding of the fitness impacts of site familiarity, we used GPS data from 106 male wild turkeys ( Meleagris gallopavo ) to quantify among‐individual differences in site familiarity, measured as proximity to familiar roosting sites, and examined how among‐individual differences in site familiarity related to susceptibility to both predation and harvest. We found substantive individual differences, with some males consistently remaining closer to familiar roosting areas than others. Male wild turkeys that exhibited greater site familiarity and stayed near familiar roosting sites were more likely to survive the hunting season, suggesting that site familiarity may facilitate hunter avoidance, possibly through increased knowledge of hunter activity. However, males that displayed greater site familiarity and occurred closer to familiar roosting sites had elevated predation risk, indicating a trade‐off in which spatial predictability may benefit individuals under one mortality source while exposing them to another. Our findings, together with prior research, challenge the assumption that site familiarity is inherently beneficial and emphasize the importance of evaluating space use behaviour in the context of multiple, interacting mortality risks. In harvested populations, such insights are especially valuable for understanding how animals navigate trade‐offs between predation and harvest risk, which can deepen our understanding of species responses to human activity. Read the free Plain Language Summary for this article on the Journal blog.

Sentinel dwarf mongooses, Helogale parvula, exhibit flexible decision making in relation to predation risk

Animals are expected to engage in behavioral decision-making that minimizes their risk of predation; these decisions can cause non-lethal predator effects to behavior and spatial use. Our goal was to determine whether non-lethal effects of a common predator, coyotes (Canis latrans), could affect the behavior of a declining reptile, the Mojave Desert tortoise (Gopherus agassizii), hereafter tortoise. We exposed captive tortoises to olfactory and visual cues of coyotes and measured their resulting foraging behavior, burrow use, and other antipredator behaviors. We also measured risk of coyote predation in wild tortoises based on burrow use. Willingness to feed and time spent feeding were unaffected by the presence of coyote urine, but higher air temperatures at the start of feeding caused a decrease in time spent at their food dish. Captive tortoises chronically exposed to coyote urine did, however, spend more time in their burrows than when exposed to rabbit urine. When exposed to a coyote decoy, captive tortoises showed more general antipredator behaviors than those exposed to a control stimulus (deer decoy). Wild tortoises were less likely to be depredated by coyotes, if they were encountered in burrows more frequently. Predator olfactory and visual cues exerted non-lethal effects on captive tortoises through behavioral adjustments to their refuge-seeking behavior, which was a behavior linked to decreased coyote predation risk for wild tortoises. Human-subsidized predator populations may negatively affect declining species, including reptiles, as a result of behavioral modifications in response to predator cues. Predators can affect behavior of animals through olfactory and visual cues, which can have measurable effects on prey populations. Changes in prey behavior in response to predator presence can occur at the expense of opportunities to forage or reproduce, leading to decreased survival and reproduction. We tested behavioral responses of captive Mojave Desert tortoises to olfactory and visual cues of coyotes, which are a common predator in the Mojave Desert and subsidized by human food sources. Foraging behavior of captive tortoises was strongly affected by air temperatures at the start of feeding, but not coyote cues. Captive tortoises did, however, increase the amount of time they spent in burrows when coyote urine was present and showed greater fearfulness at the presentation of coyote urine combined with coyote models. Increased burrow use was associated with lower risk of coyote predation in wild tortoises, which suggested an advantage to increased refuge use when coyotes were detectable. Responses by tortoises suggest that coyote cues on the landscape affect tortoises through behavioral pathways that result in increased refuge use.

Dichotomies in perceived predation risk of drinking wallabies in response to predatory crocodiles

In many species, individuals gather information about their environment both through direct experience and through information obtained from others. Social learning, or the acquisition of information from others, can occur both within and between species and may facilitate the rapid spread of antipredator behaviour. Within birds, acoustic signals are frequently used to alert others to the presence of predators, and individuals can quickly learn to associate novel acoustic cues with predation risk. However, few studies have addressed whether such learning occurs only though direct experience or whether it has a social component, nor whether such learning can occur between species. We investigate these questions in two sympatric species of Parids: blue tits (Cyanistes caeruleus) and great tits (Parus major). Using playbacks of unfamiliar bird vocalizations paired with a predator model in a controlled aviary setting, we find that blue tits can learn to associate a novel sound with predation risk via direct experience, and that antipredator response to the sound can be socially transmitted to heterospecific observers, despite lack of first-hand experience. Our results suggest that social learning of acoustic cues can occur between species. Such interspecific social information transmission may help to mediate the formation of mixed-species aggregations.

Predation of fish assemblages in seagrass meadows was examined in the field and in tank experiments. Lure trolling indicated that (1) total abundance of fish was higher on bare sediment where small fish ( 15 cm) predominated; (3) large ambush predators, primarily the grass goby and European eel, were almost completely restricted to seagrass; (4) the predation mode in seagrass was almost entirely ambushing or stalk-attacking, while the predation mode on bare sediment was almost entirely chase-attacking; (5) ambush predation was far more successful than chase-attack predation; and (6) overall predation risk was approximately three times higher in seagrass. Tank experiments showed that piscivory success of the grass goby was higher than that of the most common chase-attacker, the black goby, and the presence or absence of artificial seagrass, regardless of density, had no significant effect on predation success of either species. Guts of the grass goby contained food items of a wider size range that averaged twice the size of those of the black goby. Our results confirm our prediction that the risk of predation, especially of small/juvenile fish, is higher in seagrass meadows than at adjacent bare substrate, and this risk differential is explained by the presence of larger, more efficient ambush predators restricted to seagrass, and the scarcity of large chase-attack predators in the Novigrad Sea.

We studied the abundance of arthropod food within spruce Picea abies in relation to the foraging site selection of tits Parus and the Goldcrest Regulus regulus in winter in Central Sweden. Arthropods, spiders in particular, were most abundant in upper tree parts and in the outer sections of branches. There was a high correlation between food abundance and bird density, based on proportional use of foraging sites over eight sections of spruce suggesting that food distribution is a major factor influencing the segregative distribution of the four bird species. However, the distribution of the bird species cannot be explained solely by food abundance. In outer tree parts there were fewer birds than expected from arthropod biomass. A possible explanation is that the risk of predation by Pygmy Owls Glaucidium passerinum is higher there, reducing the net benefit of foraging in the tree parts with highest food abundance. A further support for the impact of predation comes from the fact that it is the socially least dominant species, the Goldcrest and the Coal Tit P. ater, that use the outer tree parts. Crested Tits P. cristatus are highest in dominance rank, but they mainly forage in the inner tree parts. Willow Tits P. montanus are second in the dominance, but have the lowest food abundance in their foraging sites. Both interspecific competition over food, and the site-dependent risk of predation, seem to govern the ways in which the four bird species select their foraging sites in spruce in winter.

ABSTRACTSmall mustelids are ‘snake‐like’ mammals adapted to hunt small rodents, which are their principal prey, in tunnels leaving practically no refuge for the prey. Prey rodents have adaptive behaviours to situations where the predation risk from mustelids is high, including reduced activity and escape by climbing. Small mustelids may affect prey population dynamics directly through killing (increased mortality) and/or indirectly through behavioural changes in prey as a response to the presence of mustelids (predation risk). The Predator‐Induced Breeding Suppression hypothesis (PIBS) states that a trade‐off between survival and reproduction should lead to delayed breeding under temporarily high predation risk, so that the mere presence of predators may reduce reproductive output. Current results suggest that small mustelids mainly affect prey population growth rate directly through killing. In many cyclic rodent populations, small mustelid predation is a major mortality factor, and experimental evidence supports the hypothesis that these predators drive prolonged summer declines in prey. In contrast, the evidence for PIBS is controversial. Experimental evidence shows that the indirect effects of small mustelids on prey populations are negligible during the best breeding season. However, in other seasons, the presence of predators may indirectly affect prey populations, although this has not been studied experimentally. Prey rodents may decrease mobility as a response to high predation risk by small mustelids, and this reduction in mobility decreases feeding. Reduced feeding affects the energy reserves of voles, and may delay maturation or lower the size of the first litter.

In the presence of predators, animal* may reduce or alter their mating activities. There has been little experimental study of whether mating behavior varies with the level of predation risk. Two species of moths, Pseudaletia unipuncta (Noctuidae) and Ostrinia nubilalis (Pyralidae), significantly reduced their mate-seeking behavior under high levels of simulated predation risk. Male moths aborted upwind flight in a pheromone phime, and females stopped releasing pheromone in response to sounds simulating the echolocation calls of bats. For 0. nubilalis, but not for P. unipuncta, the response varied significantly with the level of predation risk. Interspecific differences in behavioral responses likely reflect differences in physiological auditory sensitivity and/or behavioral thresholds. Female behavioral responses to sounds simulating the calls of bats that glean their prey from surfaces were significantly weaker than their responses to sounds resembling the calls of aerially hawking bats; these results support the neurophysiological data that the calls of gleaning bats are relatively inaudible to moths. This study indicates that some animals can modify their reproductive activities in response to auditory cues from predators. Key words: bats, mating behavior, moths, Ostrinia nubilalis, pheromone, predation risk, Pseudaletia unipuncta, ultrasound. [Behav Ecol 9:552-558 (1998)]