Predation Danger Research Articles

Food web interactions of two breeding Arctic shorebird species, little stint Calidris minuta and red knot Calidris canutus, are shaped by their elevational distribution

Birds often have to choose their nest site location along a food safety axis, balancing nest predation danger with the food requirements of themselves and their offspring. This is probably most important for precocial species, such as most shorebirds, in which both chicks and parents need access to food resources in the surroundings of the nest, at least during the first days of life of the chicks. In many Arctic ecosystems, shorebird nests are typically prone to predation by both avian and terrestrial predators, especially in lemming-poor years. Among other factors, the strength of the trophic interactions between shorebirds, their prey, and their predators depend on how all of these are distributed across space. During two breeding seasons in northern Taimyr, North-Central Russia, we investigated how the spatial distribution of red knot Calidris canutus and little stint Calidris minuta nests and broods overlaps with the local food landscape and also with the distribution of avian predators and their main prey, lemmings. We found that the two shorebird species use different habitats that vary in arthropod community structure in accordance with the birds’ diet: while little stints selected lower elevations where chironomid midges Chironomidae are more abundant, red knots selected higher elevations where crane flies Tipulidae are more abundant. Furthermore, little stints share low-elevation habitats with lemmings and predators, while red knots inhabit higher elevations averted by both lemmings and avian predators. We found higher nest predation for little stint nests than for red knots nests, especially in a low-lemming year. Our results thus support the idea that food web interactions are driven by landscape and community aspects.

New bands in the sleep stages of spider monkeys (Ateles geoffroyi): Electroencephalographic correlations and spatial distribution.

The study of electroencephalographic (EEG) signals in nonhuman primates has led to important discoveries in neurophysiology and sleep behavior. Several studies have analyzed digital EEG data from primate species with prehensile tails, like the spider monkey, and principal component analysis has led to the identification of new EEG bands and their spatial distribution during sleep and wakefulness in these monkeys. However, the spatial location of the EEG correlations of these new bands during the sleep-wake cycle in the spider monkey has not yet been explored. Thus, the objective of this study was to determine the spatial distribution of EEG correlations in the new bands during wakefulness, rapid eye movement (REM) sleep, and non-REM sleep in this species. EEG signals were obtained from the scalp of six monkeys housed in experimental conditions in a laboratory setting. Regarding the 1-21 Hz band, a significant correlation between left frontal and central regions was recorded during non-REM 2 sleep. In the REM sleep, a significant correlation between these cortical areas was seen in two bands: 1-3 and 3-13 Hz. This reflects a modification of the degree of coupling between the cortical areas studied, associated with the distinct stages of sleep. The intrahemispheric EEG correlation found between left perceptual and motor regions during sleep in the spider monkey could indicate activation of a neural circuit for the processing of environmental information that plays a critical role in monitoring the danger of nocturnal predation.

Avian wings can lengthen rather than shorten in response to increased migratory predation danger.

Increasing predation danger can select for safety-enhancing modifications to prey morphology. Here, we document the multi-decade wing lengthening of a Pacific flyway migrant, the western sandpiper (Calidris mauri), and contrast this with contemporaneous wing shortening of the closely related semipalmated sandpiper (C. pusilla) on the Atlantic flyway. We measured >12,000 southbound western sandpipers captured from 1978 to 2020 at a major stopover site in British Columbia. Wing length increased at 0.074 mm year-1 (SE = 0.017; p < .0003) for adults, and 0.087 mm year-1 (SE = 0.029; p < .007) for juveniles. These rates are of similarly large magnitude (4%-5% overall), but opposite in direction, to the rate we previously reported for semipalmated sandpiper adults (-0.103 mm year-1). In both species, the change is specific to wings rather than being part of a general body size change. We interpret both trends as responses to the ongoing strong increase of peregrine falcon (Falco peregrinus) populations since the mid-1970s, an important predator encountered by these species in contrasting ways during migration. Western sandpipers and peregrine migrations have temporal and spatial overlap. Longer wings enhance migratory speed and efficiency, enabling western sandpipers to decrease overlap by advancing to safer zones ahead of falcon passage. In contrast, semipalmated sandpipers primarily encounter peregrines as residents at migratory staging sites. Shorter wings improve acceleration and agility, helping migrants to escape attacks. Juvenile western sandpiper wing length also shows a component additive to the lengthening trend, shifting between years at 0.055 mm day-1 with the highly variable snowmelt date, with wings shorter following early springs. On the Pacific flyway, the timing of peregrine southward passage advances with snowmelt, increasing the relative exposure of juveniles to post-migratory resident peregrines. We interpret this annual wing length adjustment as an induced defense, made possible because snowmelt timing is a reliable cue to danger in the upcoming migration.

Predation danger during active migration: insights from a tagged Bar-tailed Godwit depredated by a breeding Peregrine Falcon

Predation danger during active migration: insights from a tagged Bar-tailed Godwit depredated by a breeding Peregrine Falcon

Visual object detection biases escape trajectories following acoustic startle in larval zebrafish

In this study, we investigated whether the larval zebrafish is sensitive to the presence of obstacles in its environment. Zebrafish execute fast escape swims when in danger of predation. We posited that collisions with solid objects during escape would be maladaptive to the fish, and therefore, the direction of escape swims should be informed by the locations of barriers. To test this idea, we developed a closed-loop imaging rig outfitted with barriers of various qualities. We show that when larval zebrafish escape in response to a non-directional vibrational stimulus, they use visual scene information to avoid collisions with obstacles. Our study demonstrates that barrier avoidance rate corresponds to the absolute distance of obstacles, as distant barriers outside of collision range elicit less bias than nearby collidable barriers that occupy the same amount of visual field. The computation of barrier avoidance is covert: the fact that fish will avoid barriers during escape cannot be predicted by its routine swimming behavior in the barrier arena. Finally, two-photon laser ablation experiments suggest that excitatory bias is provided to the Mauthner cell ipsilateral to approached barriers, either via direct excitation or a multi-step modulation process. We ultimately propose that zebrafish detect collidable objects via an integrative visual computation that is more complex than retinal occupancy alone, laying a groundwork for understanding how cognitive physical models observed in humans are implemented in an archetypal vertebrate brain. VIDEO ABSTRACT.

Semi-intensive shrimp farms as experimental arenas for the study of predation risk from falcons to shorebirds.

Varying environmental conditions and energetic demands can affect habitat use by predators and their prey. Anthropogenic habitats provide an opportunity to document both predation events and foraging activity by prey and therefore enable an empirical evaluation of how prey cope with trade‐offs between starvation and predation risk in environments of variable foraging opportunities and predation danger. Here, we use seven years of observational data of peregrine falcons Falco peregrinus and shorebirds at a semi‐intensive shrimp farm to determine how starvation and predation risk vary for shorebirds under a predictable variation in foraging opportunities. Attack rate (mean 0.1 attacks/hr, equating 1 attack every ten hours) was positively associated with the total foraging area available for shorebirds at the shrimp farm throughout the harvesting period, with tidal amplitude at the adjacent mudflat having a strong nonlinear (quadratic) effect. Hunt success (mean 14%) was higher during low tides and declined as the target flocks became larger. Finally, individual shorebird vigilance behaviors were more frequent when birds foraged in smaller flocks at ponds with poorer conditions. Our results provide empirical evidence of a risk threshold modulated by tidal conditions at the adjacent wetlands, where shorebirds trade‐off risk and rewards to decide to avoid or forage at the shrimp farm (a potentially dangerous habitat) depending on their need to meet daily energy requirements. We propose that semi‐intensive shrimp farms serve as ideal “arenas” for studying predator–prey dynamics of shorebirds and falcons, because harvest operations and regular tidal cycles create a mosaic of foraging patches with predictable food supply. In addition, the relatively low hunt success suggests that indirect effects associated with enhanced starvation risk are important in shorebird life‐history decisions.

Sheltered preservation in Ordovician trilobites

Abstract. Articulated holaspid specimens of Placoparia Hawle and Corda, 1847 and Eoharpes Raymond, 1905 entombed inside cephalopod conchs and under the remains of large illaenid, asaphid, cyclopygid and dalmanitid trilobites from the Middle Ordovician Šárka Formation of the Prague Basin (Czech Republic) are described and discussed. Two such samples were also found in the overlying Dobrotivá Formation of Middle/Late Ordovician age. Four articulated juvenile exoskeletons of Placoparia preserved under a cephalon of the cyclopygid trilobite Degamella Marek, 1961 represent the first record of shelter strategy of non-holaspid trilobites. The sheltered preservation of trilobites could be explained by a hiding behaviour associated with the danger of predation, storm disturbances, seeking for food or high vulnerability after moulting. It is obvious that Placoparia and Eoharpes deliberately entered the restricted space under skeletal parts of large trilobites or inside cephalopod conchs. These exceptional finds provide a new insight in the life strategy of some Ordovician benthic trilobites and are classified as cases of “frozen” behaviour.

Migrant Semipalmated Sandpipers (Calidris pusilla) Have Over Four Decades Steadily Shifted Towards Safer Stopover Locations

Peregrine falcons (Falco peregrinus) have undergone a steady hemisphere-wide recovery since the ban on DDT in 1973, resulting in an ongoing increase in the level of danger posed for migrant birds, such as Arctic-breeding sandpipers. We anticipate that in response migrant semipalmated sandpipers (Calidris pusilla) have adjusted migratory behaviour, including a shift in stopover site usage towards locations offering greater safety from falcon predation. We assessed semipalmated sandpiper stopover usage within the Atlantic Canada Shorebird Survey dataset. Based on 3,030 surveys (totalling 32M birds) made during southward migration, 1974 - 2017, at 198 stopover locations, we assessed the spatial distribution of site usage in each year (with a ‘priority matching distribution’ index, PMD) in relation to the size (intertidal area) and safety (proportion of a site’s intertidal area further than 150m of the shoreline) of each location. The PMD index value is > 1 when usage is concentrated at dangerous locations, 1.0 when usage matches location size, and < 1 when usage is concentrated at safer locations. A large majority of migrants were found at the safest sites in all years, however our analysis of the PMD demonstrated that the fraction using safer sites increased over time. In 1974, 80% of birds were found at the safest 20% of the sites, while in 2017, this had increased to 97%. A sensitivity analysis shows that the shift was made specifically towards safer (and not just larger) sites. The shift as measured by a PMD index decline cannot be accounted for by possible biases inherent in the data set. We conclude that the data support the prediction that increasing predator danger has induced a shift by southbound migrant semipalmated sandpipers to safer sites.

Red knots (Calidris canutus islandica) manage body mass with dieting and activity.

Mass regulation in birds is well documented. For example, birds can increase body mass in response to lower availability and/or predictability of food and decrease body mass in response to increased predation danger. Birds also demonstrate an ability to maintain body mass across a range of food qualities. Although the adaptive significance of mass regulation has received a great deal of theoretical and empirical attention, the mechanisms by which birds achieve this have not. Several non-exclusive mechanisms could facilitate mass regulation in birds. Birds could regulate body mass by adjusting food intake (dieting), activity, baseline energetic requirements (basal metabolic rate), mitochondrial efficiency or assimilation efficiency. Here, we present the results of two experiments in captive red knots (Calidris canutus islandica) that assess three of these proposed mechanisms: dieting, activity and up- and down-regulation of metabolic rate. In the first experiment, knots were exposed to cues of predation risk that led them to exhibit presumably adaptive mass loss. In the second experiment, knots maintained constant body mass despite being fed alternating high- and low-quality diets. In both experiments, regulation of body mass was achieved through a combination of changes in food intake and activity. Both experiments also provide some evidence for a role of metabolic adjustments. Taken together, these two experiments demonstrate that fine-scale management of body mass in knots is achieved through multiple mechanisms acting simultaneously.

Predator-induced fear causes PTSD-like changes in the brains and behaviour of wild animals

Predator-induced fear is both, one of the most common stressors employed in animal model studies of post-traumatic stress disorder (PTSD), and a major focus of research in ecology. There has been a growing discourse between these disciplines but no direct empirical linkage. We endeavoured to provide this empirical linkage by conducting experiments drawing upon the strengths of both disciplines. Exposure to a natural cue of predator danger (predator vocalizations), had enduring effects of at least 7 days duration involving both, a heightened sensitivity to predator danger (indicative of an enduring memory of fear), and elevated neuronal activation in both the amygdala and hippocampus – in wild birds (black-capped chickadees, Poecile atricapillus), exposed to natural environmental and social experiences in the 7 days following predator exposure. Our results demonstrate enduring effects on the brain and behaviour, meeting the criteria to be considered an animal model of PTSD – in a wild animal, which are of a nature and degree which can be anticipated could affect fecundity and survival in free-living wildlife. We suggest our findings support both the proposition that PTSD is not unnatural, and that long-lasting effects of predator-induced fear, with likely effects on fecundity and survival, are the norm in nature.

Media for sex education in elementary school: Which one is better?

In the last decade, the problem of child sexual violence is very prevalent, therefore the need for the application of sex education in elementary school children. This is done to provide knowledge about sex education that is tailored to the stage of child development and to avoid the danger of predators of violence and sexual abuse. Providing knowledge about sex education will be better if there are supporting media in its delivery. Regarding the good media in teaching sex education to elementary school children there are currently two namely electronic and print media. Although there are two media to introduce sex education, but they have not shown maximum results, both media have their advantages and disadvantages. This paper aims to review the literature in the delivery of sex education in elementary schools using electronic and print media. The results or reviews in this discussion are expected to provide information that can be used as a theoretical and methodological basis for further research in the use of sex education delivery media for elementary students.

Risk allocation: acute and chronic predator exposure have contrasting effects on Song Sparrow (Melospiza melodia) singing behaviour

Increasing the danger posed by predators may cause prey animals to alter their behaviour. For example, they may be more vigilant and so feed more slowly. Breeding male Song Sparrows (Melospiza melodia (A. Wilson, 1810)) spend much time in conspicuous, loud song, which is an important behaviour for territorial defense and for mate attraction. We measured their singing behaviour in relation to both chronic (active Cooper’s Hawk (Accipiter cooperii (Bonaparte, 1828)) nest nearby) and acute (playback of hawk calls) predator exposure. We found that proximity to a Cooper’s Hawk nest had little or no influence. In contrast, the response to acute exposure was strong and immediate: Song Sparrows reduced the song rate and the proportion of time spent singing, lowered perch height, and increased concealment. The decline in the amount of song during the few minutes following playback attributable to the acute exposure was 34.6%. We analyze these results in light of theories about how animals adjust risk taking in response to predation danger. Given that the numbers of their predators have risen steadily for the past few decades and affect the level of singing, we consider the implications for trend estimates of songbird populations based on surveys using auditory methods.

Playbacks of Asian honey bee stop signals demonstrate referential inhibitory communication

Referential communication provides a sophisticated way in which animals can communicate information about their environment. Previously, research demonstrated that honey bee stop signals encode predator danger in their fundamental frequency and danger context in their duration. Here, we show that these signals also encode danger in their vibrational amplitude. Stop signals elicited by the more dangerous predator, the large hornet (Vespa mandarinia) had significantly 1.5-fold higher vibrational amplitudes than those elicited by the small hornet predator (Vespa velutina). We measured the freezing vibrational response thresholds, and show that natural signals exceed these response thresholds. Finally, with artificial playbacks of the vibratory stop signal, we demonstrate that these signals referentially encode the danger that foragers experience at food source. Stop signals elicited by the larger and significantly more dangerous predator (V. mandarinia) were significantly 1.4-fold more inhibitory than stop signals elicited by the smaller and less dangerous predator (V. velutina).

Isolate the DNA of Musca domestica (Diptera: Muscidae) with Study of the aspect of their Larval and Pupal Behavior

Current study included two sections: the first section include collection of samples Musca domestica flies rearing in cages which containing artificial food for nutrition and superfluity it, in order to get to several generations of it, then had selected some samples of larvae and adults for the purpose of extracting DNA, by use the method of Beye and Raeder,1993,this method succeeded to isolate the DNA from larvae, while the method didn’t get through adults because of the speed of growth and cells divisions in the larval stage, as compared with adult . As to The second section is which put dozens of larvae with the wet nutrimental at a home garden and watch the behavior of the larvae to migration looking for pupal stage places, found from the results that most of larvae were left dry nutrition environment look for most the driest places, it were passed distance ranging between 30-40 cm for purpose of the stop and quiet to get ready to enter into pre-pupal stage, and then as to aspect of place of pupae showing results that most larvae preferred to hide under the leaves and plants residues that provide it with a safe place to hide from danger of predators, or devours and camouflage, and then cracks in the soil and the walls.

Identifikasi Kandungan Senyawa Fitokimia Pada Daun dan Akar Lamun di Pantai Samuh Bali

Seagrass is the only flowering plant which has a true roots, leaves, and stems, an angiosperm plant that adapted to live entirely in the ocean. Seagrass produces several compounds which produced through secondary metabolism, one of the secondary metabolism is the phytochemicals. Seagrass ecosystem in Tanjung Benoa was discovered along Samuh Beach, where 9 kinds of seagrass species were found around the seagrass ecosystem in Tanjung Benoa. Samuh Beach has a tranquil water conditions and sandy substrate. The activities of marine tourism and hotel waste disposal in Tanjung Benoa waters cause major ecological pressure and physical pressure for the seagrass ecosystem. This study aims to determine the content of phytochemicals in the leaves and roots of seagrass. Screening method was used to determine the content of bioactive alkaloids, flavonoids, saponins, steroids, and tannin compounds. Each of these compounds has an important role in the seagrass. The existence of chemical compounds of the flavonoid, alkaloid and steroid groups in the roots and leaves of Cymodocea rotundata seagrass, Enhalus acoroides, Thalassia hemprichi, Halophila ovalis, Halophila minor, Halodule uninervis and Sryngodium isoetifolium in this study indicate that the seven species of seagrass has potential as a natural chemical antifouling, antifungal, and antibacterial.Then the seagrass will be protected from the danger of predators or epiphanies that interfere with the growth of seagrass and the ecosystems on Samuh Beach will remain intact.

Experimental addition of cover lowers the perception of danger and increases reproduction in meadow voles (Microtus pennsylvanicus)

Predation danger is pervasive for small mammals and is expected to select strongly for behavioural tactics that reduce the risk. In particular, since it may be considered a cost of reproduction, predation danger is expected to affect the level of reproductive effort. We test this hypothesis in a population of meadow voles (Microtus pennsylvanicus (Ord, 1815)) under seminatural conditions in field enclosures. We manipulated the voles’ perception of predation danger by adjusting the available cover and measured giving up density (GUD) in food patches to verify that the perception of danger differed between high- and low-cover treatments. Treatments did not differ in actual predation rate, in vole density, or in the quantity or quality of food. During the experiments, we measured indices of vole reproductive effort including activity (electronic detectors), foraging intensity (fecal plates), and the number of young produced (livetrapping). Voles in the high-cover (lower danger) treatments were more active, foraged more, and produced 85% more young per female per trap period than voles in the low-cover (higher danger) treatment. We briefly discuss the population consequences of this adaptive behavioural flexibility.

Male vigilance and presence are important for foraging by female Chinese grouse in the pre-incubation period

In some monogamous birds, males invest more time in vigilance than females, especially during the pre-incubation period. As behaviors are time costly, there is a tradeoff between vigilance and feeding behavior. Male vigilance can be regarded as a male investment in their mates and may benefit the female by reducing the danger of predation, increasing her probability of survival, and allowing more time for her to forage to obtain more resources for egg production and incubation. In this study, we documented the proportion of time spent in vigilance and feeding by Chinese grouse Tetrastes sewerzowi with their mates and alone during the pre-incubation period, and then estimated male vigilance under more severe predation pressures through predator call playback. Our results indicated that paired male Chinese grouse spend more time in vigilance than unpaired males and paired females and could alter their activity budgets in response to the social context (i.e. with and without their mate) and an experimental e...

Long-term continental changes in wing length, but not bill length, of a long-distance migratory shorebird.

We compiled a >50‐year record of morphometrics for semipalmated sandpipers (Calidris pusilla), a shorebird species with a Nearctic breeding distribution and intercontinental migration to South America. Our data included >57,000 individuals captured 1972–2015 at five breeding locations and three major stopover sites, plus 139 museum specimens collected in earlier decades. Wing length increased by ca. 1.5 mm (>1%) prior to 1980, followed by a decrease of 3.85 mm (nearly 4%) over the subsequent 35 years. This can account for previously reported changes in metrics at a migratory stopover site from 1985 to 2006. Wing length decreased at a rate of 1,098 darwins, or 0.176 haldanes, within the ranges of other field studies of phenotypic change. Bill length, in contrast, showed no consistent change over the full period of our study. Decreased body size as a universal response of animal populations to climate warming, and several other potential mechanisms, are unable to account for the increasing and decreasing wing length pattern observed. We propose that the post‐WWII near‐extirpation of falcon populations and their post‐1973 recovery driven by the widespread use and subsequent limitation on DDT in North America selected initially for greater flight efficiency and latterly for greater agility. This predation danger hypothesis accounts for many features of the morphometric data and deserves further investigation in this and other species.

The redistribution of non-breeding dunlins in response to the post-DDT recovery of falcons.

Large-scale changes in predator populations are occurring worldwide due to (re-)introductions, over-exploitation, or recovery after decimation by pesticides and persecution. These widespread changes may affect the distribution of their prey. We studied the continental-scale distributions of non-breeding Calidris alpina pacifica and C. a. hudsonia (Pacific and Atlantic dunlins, respectively), as numbers of their major predators-peregrines (Falco peregrinus) and merlins (F. columbarius; together 'falcons')-increased after DDT was banned in 1973. For the period 1975-2010 we compiled the number of dunlins and falcons in each of 244 Christmas Bird Count circles, which cover most of the dunlins' non-breeding ranges. Over the study period, falcons increased by 6.5- (Pacific) and 3.1- (Atlantic) fold, spread to more count circles, and the number of dunlins per falcon fell. The annual total count of the two dunlin sub-species fluctuated strongly and independently. We measuredannual aggregation as the expected proportion of a subspecies total found on the same count circle as a randomly selected dunlin. The average aggregation of Pacific dunlins (0.117) was about double that of Atlantic dunlins (0.059), with annual variation largely attributable to changes in a few large count circles. The slope of the aggregative response to year-on-year changes in dunlin numbers was identical on the two coasts. The response to the ongoing falcon increase was positive and significant on the Pacific and slightly negative on the Atlantic. We interpret these results using a version of the ideal free distribution that includes predation danger.

Individual shifts toward safety explain age-related foraging distribution in a gregarious shorebird

Although age-related spatial segregation is ubiquitous, the underlying mechanisms are poorly understood. Here, we aim to elucidate the processes behind a previously established age-related foraging distribution of red knots (Calidris canutus canutus) in their main wintering area in West Africa (Banc d’Arguin, Mauritania). Based on 10 years of observations of 1232 uniquely color-ringed individuals of 1 to 18+ years old, we examined whether the observed age-related foraging distribution resulted from 1) spatial differences in mortality or 2) age-related shifts in habitat use. Using multistate capture–recapture modeling, we showed that with age foraging red knots moved away from the shoreline, that is, to areas with fewer surprise attacks by raptors. Considering uncertainties in the subjective gradient in predation danger with increasing distance from shore (as assessed from correlations between vigilance and distance from shore in foraging birds), we applied 2 different danger zone boundaries, at 40 m and 500 m from shore. Between years, red knots had a much higher chance to move from the dangerous nearshore area to the “safe” area beyond (71–78% and 26% for 40-m and 500-m danger zone boundary, respectively), than vice versa (4% and 14%). For neither danger zone boundary value did we find differences in annual mortality for individuals using either dangerous or safe zone, so the move away from the shore with age is attributed to individual careers rather than differential mortality. We argue that longitudinal studies like ours will reveal that ontogenetic shifts in habitat use are more common than so far acknowledged.