Predation Attempts Research Articles

Variation in foraging activity influences area-restricted search behaviour by bottlenose dolphins.

Area-restricted search (ARS) behaviour is commonly used to characterize spatio-temporal variation in foraging activity of predators, but evidence of the drivers underlying this behaviour in marine systems is sparse. Advances in underwater sound recording techniques and automated processing of acoustic data now provide opportunities to investigate these questions where species use different vocalizations when encountering prey. Here, we used passive acoustics to investigate drivers of ARS behaviour in a population of dolphins and determined if residency in key foraging areas increased following encounters with prey. Analyses were based on two independent proxies of foraging: echolocation buzzes (widely used as foraging proxies) and bray calls (vocalizations linked to salmon predation attempts). Echolocation buzzes were extracted from echolocation data loggers and bray calls from broadband recordings by a convolutional neural network. We found a strong positive relationship between the duration of encounters and the frequency of both foraging proxies, supporting the theory that bottlenose dolphins engage in ARS behaviour in response to higher prey encounter rates. This study provides empirical evidence for one driver of ARS behaviour and demonstrates the potential for applying passive acoustic monitoring in combination with deep learning-based techniques to investigate the behaviour of vocal animals.

Predation attempt by a long-tailed weasel Neogale frenata on a Holcosus gaigeae lizard

Predation attempt by a long-tailed weasel Neogale frenata on a Holcosus gaigeae lizard

Predation attempt by a Southern Heath Monitor, Varanus rosenbergi (Varanidae), on a Western Shingleback Lizard, Tiliqua rugosa (Scincidae), in Southwest Australia

Predation attempt by a Southern Heath Monitor, Varanus rosenbergi (Varanidae), on a Western Shingleback Lizard, Tiliqua rugosa (Scincidae), in Southwest Australia

Predation attempt on a Slow Worm (Anguis fragilis) by a House Sparrow (Passer domesticus)

Predation attempt on a Slow Worm (Anguis fragilis) by a House Sparrow (Passer domesticus)

Predation attempt on a Slow Worm (Anguis fragilis) by a House Sparrow (Passer domesticus)

Predation attempt on a Slow Worm (Anguis fragilis) by a House Sparrow (Passer domesticus)

Malformed individuals of the trilobiteEstaingia bilobatafrom the Cambrian Emu Bay Shale and their palaeobiological implications

AbstractMalformed trilobite specimens present important insight into understanding how this extinct arthropod group recovered from developmental or moulting malfunctions, pathologies, and injuries. Previously documented examples of malformed trilobite specimens are often considered in isolation, with few studies reporting on multiple malformations in the same species. Here we report malformed specimens of the ellipsocephaloid trilobiteEstaingia bilobatafrom the Emu Bay ShaleKonservat-Lagerstätte(CambrianSeries 2, Stage 4) on Kangaroo Island, South Australia. Ten malformed specimens exhibiting injuries, pathologies, and a range of teratologies are documented. Furthermore, five examples of mangled exoskeletons are presented, indicative of predation onE. bilobata. Considering the position of malformed and normal specimens ofE. bilobatain bivariate space, we demonstrate that the majority of malformed specimens cluster among the larger individuals. Such specimens may exemplify larger forms successfully escaping predation attempts, but could equally represent individuals exhibiting old injuries that were made during earlier (smaller) growth stages that have healed through subsequent moulting events. The available evidence from the Emu Bay Shale suggests that this small, extremely abundant trilobite likely played an important role in the structure of the local ecosystem, occupying a low trophic level and being preyed upon by multiple durophagous arthropods. Furthermore, the scarcity of malformedE. bilobataspecimens demonstrates how rarely injuries, developmental malfunctions, and pathological infestations occurred within the species.

A delicate balance: wolves exploiting dogs’ predation attempts in central Italy

A delicate balance: wolves exploiting dogs’ predation attempts in central Italy

Crossing the valley of non-intimidating conspicuousness: evolution of warning coloration through the lens of fitness landscapes.

The initial evolution of conspicuous aposematism is a longstanding evolutionary paradox: while the benefits of conspicuousness in aposematic signals have been demonstrated, they rely on predators being familiar with the conspicuous signals and avoiding them. In a system dominated by naïve predators, the appearance of conspicuousness would be expected to increase detection and attack rate by the predators. Hence, it is unclear how such signals could become established in a naïve community. We suggest that this problem may usefully be framed in the terms of fitness landscapes, an idea used for conceptualizing the mapping between genotype/phenotype and fitness. The evolution of conspicuousness can be thought of as a special case of valley crossing, which concerns the transition of populations between fitness peaks, when such a transition imposes an initial decrease in fitness. Crypsis may be regarded as a local fitness peak, hindering predators' ability to detect prey; for an unpalatable species, conspicuous aposematism may constitute a higher-still fitness peak, preventing predation attempts altogether and allowing access to niches unavailable to species encumbered by the necessity to remain concealed from predators. However, in order to reach this higher peak, the population must first cross the valley of non-intimidating conspicuousness, in which the prey is conspicuous but the predators are not yet deterred. Using terms borrowed from the concept of fitness landscapes, we categorize several solutions suggested previously in the literature as either concerning changes in the fitness landscape or as illuminating possible ridges connecting the two peaks, which emerge from unconsidered dimensions of the fitness landscape. We suggest that considering this question through the lens of fitness landscapes not only facilitates useful categorization of previously suggested solutions but may also prove useful for thinking about novel ones.

Unwrapping broken tails: Biological and environmental correlates of predation pressure in limbless reptiles.

Studying species interactions in nature often requires elaborated logistics and intense fieldwork. The difficulties in such task might hinder our ability to answer questions on how biotic interactions change with the environment. Fortunately, a workaround to this problem lies within scientific collections. For some animals, the inspection of preserved specimens can reveal the scars of past antagonistic encounters, such as predation attempts. A common defensive behaviour that leaves scars on animals is autotomy, the loss of a body appendage to escape predation. By knowing the collection site of preserved specimens, it is possible to assess the influence of organismal biology and the surrounding environment in the occurrence of autotomy. We gathered data on tail loss for 8189 preserved specimens of 33 snake and 11 amphisbaenian species to investigate biological and environmental correlates of autotomy in reptiles. We applied generalized linear mixed effect models to evaluate whether body size, sex, life-stage, habitat use, activity pattern, biome, tropicality, temperature and precipitation affect the probability of tail loss in limbless reptiles. We observed autotomy in 23.6% of examined specimens, with 18.7% of amphisbaenian and 33.4% of snake specimens showing tail loss. The probability of tail loss did not differ between snakes and amphisbaenians, but it was higher among large-sized specimens, particularly in adults and females. Chance of tail loss was higher for diurnal and arboreal species, and among specimens collected in warmer regions, but it was unaffected by biome, precipitation, and tropicality. Autotomy in limbless reptiles was affected by size-dependent factors that interplay with ontogeny and sexual dimorphism, although size-independent effects of life-stage and sex also shaped behavioural responses to predators. The increase in probability of tail loss with verticality and diurnality suggests a risk-balance mechanism between species habitat use and activity pattern. Although autotomy is more likely in warmer regions, it seems unrelated to seasonal differences in snakes and amphisbaenians activity. Our findings reveal several processes related to predator-prey interactions involving limbless reptiles, demonstrating the importance of scientific collections to unveil ecological mechanisms at different spatio-temporal scales.

Report of an attack on a howler monkey Alouatta sara by a group of collared peccaries Dicotyles tajacu at a mammal clay lick in Madre de Dios, Peru.

Howler monkeys Alouatta are almost exclusively arboreal. They will, however, occasionally descend to the forest floor to conduct geophagy at clay licks if these are present within their home range. They do this to incorporate certain minerals into their diet and/or for detoxification purposes. Clay licks are risky areas however, especially for arboreal mammals, as visiting them requires the monkeys to leave the safety of the trees. This has been confirmed by observed predation attempts on howler monkeys by large felines at clay licks. We report an additional risk for howler monkeys descending to the forest floor that has not previously been considered, namely potential attacks by collared peccaries Dicotyles tajacu. Camera traps were placed at three different clay licks in the Taricaya Ecological Reserve, located in the southeastern Peruvian Amazon, to monitor the fauna within the reserve. On 4 June 2017, the camera traps registered a lethal attack on a howler monkey by a group of collared peccaries at one of the clay licks.

Patterns of predation and meat-eating by chacma baboons in an Afromontane environment

Abstract Meat-eating among non-human primates has been well documented but its prevalence among Afromontane baboons is understudied. In this study we report the predatory and meat-eating behaviours of a habituated group of gray-footed chacma baboons (Papio ursinus griseipes) living in an Afromontane environment in South Africa. We calculated a vertebrate-eating rate of 1 every 78.5 hours, increasing to 58.1 hours when unsuccessful predation attempts were included. A key food source was young antelopes, particularly bushbuck (Tragelaphus scriptus), which were consumed once every 115 observation hours. Similar to other baboon research sites, predations seemed mostly opportunistic, adult males regularly scrounged and monopolised prey, there was no evidence they used an active kill bite, and active sharing was absent. This is the first baboon study to report predation of rock python (Python sebae) eggs and likely scavenging of a leopard (Panthera pardus) kill (bushbuck) cached in a tree. We also describe several scramble kleptoparasitism events, tolerating active defence from antelope parents, and the baboons inhibiting public information about predations. In the latter case, baboons with meat often hid beyond the periphery of the group, reducing the likelihood of scrounging by competitors. This often led to prey carcasses being discarded without being fully exploited and potentially providing resources to scavengers. We also highlight the absence of encounters with numerous species, suggesting the baboons are a key component of several species’ landscapes of fear. Given these findings it seems likely that their ecological role in the Soutpansberg has been undervalued, and such conclusions may also hold for other baboon populations.

Disturbance‐dependent Yellow‐legged Gull (Larus michahellis) predation on Larid chicks decreases with chick age

Predation is one of the key factors shaping the dynamics of animal populations. In birds, nest loss due to predation can be a significant cause of low reproductive success. Ground‐nesting birds are among the bird groups most susceptible to predation, mainly because their nests are easily accessible to a broad suite of potential predators. For these birds, anthropogenic disturbances can generate changes in nest predation risk by altering their antipredator behaviour and also by altering the behaviour of the predator species, i.e. the predator becoming much more aware of predation opportunities due to frequent disturbances and/or motivated to repeat predation attempts when some are successful. To date, most previous studies investigating this have focused on a single effect, either predation or disturbance, on chick survival. It remains unknown how the risk of predation with and without disturbance varies with chick age. In this study, we used behavioural observations to assess how the interaction between predators and disturbance affects predation risk in chicks and how this interacts with chick age. Specifically, we investigated the effect of disturbance caused by humans and stray dogs on the predation of Slender‐billed Gull Chroicocephalus genei chicks by Yellow‐legged Gulls Larus michahellis, and whether this depended on the age of the chicks. Our results revealed that disturbance had a significant positive effect on predation measures of Slender‐billed Gull chicks by Yellow‐legged Gulls, but that this effect was mediated both by disturbance type and the age of chicks. Stray dogs entering the colony had a stronger disturbance effect on chicks than passing humans, increasing predation risk by Yellow‐legged Gulls. Our results also showed that chick age interacts with disturbance type to determine the predation risk. This is probably mediated by chicks' capacity to escape predation by gathering in a single large crèche that runs into the water when disturbed. To preserve Slender‐billed Gull colonies in one of its few remaining breeding sites in Tunisia, and as gulls tend to react even when the disturbance occurs relatively far from the colonies, it is crucial to (1) restrict human access to dikes and islets where large colonies breed and (2) construct artificial islets attractive to gulls and inaccessible to stray dogs.

Influence of tail injury on the development of Neotropical elegant treefrog tadpoles

Anuran larvae in aquatic environments are important prey items for several vertebrate and invertebrate species. Besides avoiding predation, there are some strategies that may reduce the physical damage in those tadpoles that survive the predation attempt. For example, the injured tadpole tail can regrow after a predator bite, but few studies have examined the consequences of such injury. We examined the consequences of three levels of injury to the tail and how this influenced development and feeding behavior of tadpoles of the Neotropical elegant treefrog, Dendropsophus elegans. We collected spawns and kept them in the laboratory until tadpoles reached Gosner’s stages 28 to 35. Then, they were separated in four experimental groups: individuals with tail trimmed in 30, 50 or 70 % of its length, and a control group, with no tail removing. We counted the days until metamorphosis, calculated the Scaled Mass Index (SMI) through weight and length of newly-metamorphosed, and evaluated the feeding frequency to evaluate the influence of tail amputation on them. We found that the time until metamorphosis was positively related to the extent of the amputation, but SMI and feeding behavior were not influenced. As the time to metamorphose is related to the survivorship chances of individuals: i.e., if the aquatic environment is with high density of predators, it would be advantageous to rapidly metamorphose out of the water. However, tail injury delays the metamorphose process, which could influence the survival of the individual.

Discriminating predation attempt outcomes during natural foraging using the post-buzz pause in the Japanese large-footed bat, Myotis macrodactylus

ABSTRACTBats emit a series of echolocation calls with an increasing repetition rate (the terminal buzz) when attempting to capture prey. This is often used as an acoustic indicator of prey-capture attempts. However, because it is directly linked to foraging efficiency, predation success is a more useful measure than predation attempts in ecological research. The characteristics of echolocation calls that consistently signify predation success across different situations have not been identified. Owing to additional influencing factors, identification of these characteristics is particularly challenging for wild bats foraging in their natural environment compared with those in flight chambers. This study documented the natural foraging behavior of wild Japanese large-footed bats (Myotis macrodactylus) using synchronized acoustic and video recordings. From the video recordings, we could assign 137 attacks to three outcome categories: prey captured (51.8%), prey dropped (29.2%) and failed attempt (19%). Based on previous indications from laboratory studies that the length of the silent interval following the terminal buzz (post-buzz pause) might reflect the prey-capture outcome, we compared post-buzz pause durations among categories of attack outcomes. The post-buzz pause was longest in the case of successful capture, suggesting that the length of the post-buzz pause is a useful acoustic indicator of predation success during natural foraging in M. macrodactylus. Our finding will advance the study of bat foraging behavior using acoustic data, including estimations of foraging efficiency and analyses of feeding habitat quality.

Predation on artificial caterpillars following understorey fires in human‐modified Amazonian forests

AbstractTropical forests are facing several impacts from anthropogenic disturbances, climate change, and extreme climate events, with potentially severe consequences for ecological functions, such as predation on folivorous invertebrates. Folivory has a major influence on tropical forests by affecting plant fitness and overall seedling performance. However, we do not know whether the predation of folivorous arthropods by birds, mammals, reptiles, and other arthropods is affected by anthropogenic disturbances such as selective logging and forest fires. We investigated the impacts of both pre‐El Niño human disturbances and the 2015–2016 El Niño understorey fires on the predation of 4500 artificial caterpillars across 30 Amazonian forest plots. Plots were distributed in four pre‐El Niño forest classes: undisturbed, logged, logged‐and‐burned, and secondary forests, of which 14 burned in 2015–16. We found a higher predation incidence in forests that burned during the El Niño in comparison with unburned ones. Moreover, logged‐and‐burned forests that burned again in 2015–16 were found to have significantly higher predation incidence by vertebrates than other forest classes. However, overall predation incidence in pre‐El Niño forest disturbance classes was similar to undisturbed forests. Arthropods were the dominant predators of artificial caterpillars, accounting for 91.5% of total predation attempts. Our results highlight the resilience of predation incidence in human‐modified forests, although the mechanisms underpinning this resilience remain unclear.Abstract in Portuguese is available with online material.

Flexible reprogramming of Pristionchus pacificus motivation for attacking Caenorhabditis elegans in predator-prey competition

Animals with diverse diets must adapt their food priorities to a wide variety of environmental conditions. This diet optimization problem is especially complex for predators that compete with prey for food. Although predator-prey competition is widespread and ecologically critical, it remains difficult to disentangle predatory and competitive motivations for attacking competing prey. Here, we dissect the foraging decisions of the omnivorous nematode Pristionchus pacificus to reveal that its seemingly failed predatory attempts against Caenorhabditis elegans are actually motivated acts of efficacious territorial aggression. While P.pacificus easily kills and eats larval C.elegans with a single bite, adult C.elegans typically survives and escapes bites. However, non-fatal biting can provide competitive benefits by reducing access of adult C.elegans and its progeny to bacterial food that P.pacificus also eats. We show that the costs and benefits of both predatory and territorial outcomes influence how P.pacificus decides which food goal, prey or bacteria, should guide its motivation for biting. These predatory and territorial motivations impose different sets of rules for adjusting willingness to bite in response to changes in bacterial abundance. In addition to biting, predatory and territorial motivations also influence which search tactic P.pacificus uses to increase encounters with C.elegans. When treated with an octopamine receptor antagonist, P.pacificus switches from territorial to predatory motivation for both biting and search. Overall, we demonstrate that P.pacificus assesses alternate outcomes of attacking C.elegans and flexibly reprograms its foraging strategy to prioritize either prey or bacterial food.

Predation attempt by a Tropical House Gecko, Hemidactylus mabouia (Gekkonidae), on a Cuban Blue Anole, Anolis allisoni (Dactyloidae) in south-central Cuba

Predation attempt by a Tropical House Gecko, Hemidactylus mabouia (Gekkonidae), on a Cuban Blue Anole, Anolis allisoni (Dactyloidae) in south-central Cuba

Specific Turbulence- and Chaoborus-Induced Morphotypes Affect the Streamlining Properties of Daphnia cucullata

Inducible defenses are a wide-spread defensive mechanism inDaphnia. For example,D. cucullatais known to form different adaptive morphologies under changing environmental conditions. In this species, predator presence elicits defensive helmets. Defended animals perform better and survive more frequently in predation attempts. Another peculiarity ofD. cucullatais that they develop these defenses also in response to turbulence. The mechanisms that underly this defensive effect are so far unclear. Therefore, we investigated the three-dimensional morphology of the typical, the turbulence- andChaoborus-exposed morph and analyzed their surface and volume alterations. We furthermore measured the swimming velocities of these morphs. With the determined shapes and the measured velocities, we simulated the drag force under different angles of attack and determined the energy necessary to move through the water. In the light of previous findings and hypotheses we here discuss biomechanical mechanisms that improveD. cucullata’s fitness in the investigated environments.

Shaking things up: the unique feeding behaviour of western banded geckos when consuming scorpions

AbstractPredators that feed on dangerous prey species must evolve mechanisms to reduce the likelihood of injury or death during a predation attempt. Scorpions are prime examples of dangerous prey items for insectivores, because they can inflict a venomous and potentially fatal sting when attacked. Despite this risk, the western banded gecko (Coleonyx variegatus), a generalist insectivore, occasionally preys on dune scorpions (Smeringurus mesaensis). We use high-speed videography to examine the modulation of prey capture biomechanics in relationship to prey type. The capture of undefended evasive (cricket) and non-evasive (worms) prey follows previous studies of lizard attack kinematics. However, we have discovered a unique shake-feeding behaviour used by western banded geckos when feeding on scorpions, whereby the gecko bites the scorpion, then performs very rapid side-to-side shaking with its head and body. Given the speed and violence of shake-feeding, we suggest that geckos shake the scorpion to cause mass trauma and subsequent immobility or, potentially, to break the stinger and render the scorpion harmless. This behaviour might be widespread among geckos that feed on these dangerous prey species.

Reduced avian predation on an ultraviolet-fluorescing caterpillar model

Abstract Many caterpillars exhibit patterns of ultraviolet (UV) fluorescence, although its purpose is unclear. We used realistic plasticine models of a fluorescing caterpillar species, the Polyphemus moth, Antheraea polyphemus (Lepidoptera; Saturniidae), adorned with fluorescent paint treatments and unpainted controls to quantify bird predation in two hardwood forested regions of New York State, United States of America. In separate field studies, significantly more birds struck deployed model caterpillars that had no UV fluorescence. More strikes on unpainted and clear paint treatments suggest paint itself did not impact predation, whereas similar predation attempts on bird and human-visible fluorescent dummies suggest that UV fluorescence and not UV reflectance was responsible for the observed effect. A second study found the dummy’s location on the tree was also important, but the low number of bird strikes limited analyses. Although our results do not identify a mechanism, fluorescence may function to deter or avoid predation. Our study contributes to a growing body of work investigating the importance of UV patterns in arthropods and highlights a potentially fruitful area of future research on predator–prey relations.