Predators Research Articles

Are Amphibian Eggs a Precious Food Resource for Cynops pyrrhogaster (Amphibia: Urodela) in Spring?

Most true predators are generalists, and it is difficult to examine their actual diets in the wild. In many cases, the prey that experience a large impact are also not well known. Amphibians are generalist predators that prey mainly on insects, and amphibian species active beginning in spring are considered to prey on food resources other than insects in this season due to the low number of insects. The Japanese red-bellied newt (Cynops pyrrhogaster) is a generalist predator widely distributed in Japan and is known to frequently prey on amphibian eggs. Here, we showed that amphibian eggs are a precious food resource for C. pyrrhogaster in spring. The total weights of stomach contents were compared among seasons and we found that the total weights of stomach contents in spring were the same as those in summer. Also, we examined whether C. pyrrhogaster preys on amphibian eggs instead of insects in spring. The composition of the taxonomic groups in their stomach contents was compared among the seasons, and the indicator groups in their stomach contents were identified in each season. We found that they preyed not only upon insects but also upon amphibian eggs in spring, while they preyed mainly upon insects in summer and autumn. Our results suggest that C. pyrrhogaster preys on amphibian eggs to compensate for the shortage of food in spring when the number of insects is low.

Food habits of the exotic lizard Diploderma polygonatum polygonatum (Agamidae, Squamata, Reptilia) at a World Heritage site, Yakushima Island, Japan

This study investigated the dietary components of an exotic lizard, Diploderma polygonatum polygonatum Hallowell, 1861, at the Yakushima Island World Heritage Site in southern Japan. A total of 430 individuals of various invertebrate species were found in the stomachs of 42 lizards. The most abundant order of prey animals was Hymenoptera (303 individuals in 38 lizards), followed by Coleoptera (36 individuals in 18 lizards) and Lepidoptera (24 individuals in 15 lizards). DNA barcoding was applied to 135 dietary items, and a total of 59 sequences were confirmed. BLAST searches showed that 33 of these 59 sequences presented more than 95% identity to known sequences in the database. These results showed this arboreal lizard captured invertebrates from both ground and arboreal habitats in the introduced area. Although no species on the Japanese Red List were identifiable in the stomachs of the lizards, the database of invertebrate DNA was insufficient to identify the dietary components of this predator at a World Heritage site.

Narrating Disruptive Encounters in the Forest: Hunting, Animal Lives, and Ecology

Over the last century, three popular writers and media personalities have written bestsellers and created TV programs in order to alert the general public to the suffering of wild animals as well as the deleterious effects on young trees caused directly or indirectly by hunting and forestry practices. Austrian journalist and writer Felix Salten published Bambi: A Story of Life in the Woods (1923), using a baby deer’s perspective. German journalist and literary author Horst Stern shocked the nation with his TV program Remarks about the Stag (1971), which shows the brutality of hunting; his 1989 Jagdnovelle (The Last Hunt) weaves together a hunter’s perspective with his prey animal’s experience. In recent years, German forester Peter Wohlleben has shifted the focus from animals to plants by publishing a series of popular books about the forest, starting with The Hidden Life of Trees (2015). This essay examines how Salten, Stern, and Wohlleben all humanize their animal and plant characters, including through a form of “critical anthromorphism” (Mossner)—and are criticized for it. They also incorporate ethology, i.e. observations of animal behavior and the forest environment, as well as scientific knowledge, as they attempt to evoke their audience’s empathy for their nonhuman characters. Hunting pressure and the violent disruption of the lives of the animals leads to an “ecology of fear” instead of an “ecology of subjects” that would align better with changing perceptions of “nature” (Soentgen). Ethical questions concerning the mass killing of Europe’s largest mammals remain as it does not succeed in reducing deer overpopulation or damage to the forest ecosystem, perpetuing Germany’s forest/game conflict.

Experiences with live-capture and radio collaring of lynx Lynx lynx in Norway

Lynx have been captured for radio-collaring as part of three research projects in Norway between 1987 and 1996. Box traps, padded leghold traps, foot snares, combinations of foot snares and leghold traps, chasing animals up trees, catching neonates at lairs, and darting individuals while crossing roads have all been used to capture individuals. Mortality was particularly high (2 of 3 died) in the first project in Aust-Agder and Nord-Trøndelag (1987 - 88). Methodological improvements reduced this mortality rate to one lynx of 17 (6%) in Nord-Trøndelag (1994 - 96) and two of 17 (12%) in Hedmark (1995 - 96). Lessons from these accidents should reduce future mortality even further. Leghold traps and foot snares placed around a carcass of a prey animal killed by the lynx are far more effective than box traps, but maintain a higher risk of injuries. Lynx appeared more likely to return to roe deer carcasses than those of semi-domestic reindeer. There was no selection for lighter lynx. It is important to reduce the time-span between capture and immobilisation to lower the risk of injuries. It is recommended to avoid capturing and immobilising lynx at extremely low or high temperatures. Non-target animals getting caught can pose a minor problem when leghold traps stay open for longer periods.

Cats and dogs as hosts of Blastocystis – What is the evidence?

Blastocystis is one of the most common intestinal parasites observed in human and non-human hosts. Recent meta-analyses have indicated a potential role for pets such as dogs and cats as reservoir hosts of Blastocystis, but the data underpinning this hypothesis are of mixed quality. Reviewing data for 45,894 samples tested for Blastocystis by DNA-based methods and 11,908 subtype observations, a model was developed for calculating indices that could be used for evaluating individual species as natural hosts of Blastocystis, based on weighted products of positivity rates and subtype distributions. Data from cats and dogs were analysed, using other well-sampled hosts (pig, cattle, sheep, goat, and human) as references. Data from cats and dogs meeting the inclusion criteria were entered into the model. The overall positivity rates for pigs, cattle, sheep, goats, humans, dogs, and cats were 40 %, 40 %, 35 %, 28 %, 25 %, 6 %, and 5 %, respectively, with statistically significant lower positivity rates in cats and dogs (p < 0.0001). Indices indicating Blastocystis specificity to host ranged between 0.16 (humans) and 0.49 (cattle) for the reference hosts, whereas indices for cats and dogs were only 0.01 and 0.02, respectively. Finally, indices for ST specificity to host were higher for reference hosts (range, 0.66–0.93) than for cats (0.62) and dogs (0.56). Taken together, the analyses indicate that cats and dogs are not natural or reservoir hosts of Blastocystis and that the sporadic subtype pattern observed in these hosts might indicate exposure to Blastocystis through contaminated water/feed, including Blastocystis colonizing prey animals.

Nature without Suffering: Herbivorisation of Predator Species for the Compassionate Stewardship of Earth’s Ecosystems

Abstract Predation causes suffering and the premature deaths of prey animals. With innovative technologies on the horizon, humanity could phase it out. We argue that herbivorisation, i.e., turning carnivorous species into herbivorous ones with biotechnologies, is better than other strategies for ending predation, because it is the one most likely to preserve environmental values such as biodiversity and receive democratic support. Pressure on vegetation in herbivorised ecosystems would increase, but fertility control could relieve this pressure. We respond to other objections and conclude that the process should be considered as a future megaproject to reduce naturogenic harms.

Insights into Notonecta maculata biology and its consumptive and non‐consumptive effects on Aedes albopictus

AbstractNotonecta species (Hemiptera: Notonectidae) are generalist true predators with a strong impact on the size, structure, and richness of the aquatic communities, particularly on mosquito populations. Juvenile and adult backswimmers not only prey on mosquito larvae (consumptive effect) but their presence can also deter the oviposition of gravid mosquito females (non‐consumptive effect). In this study, we selected a Western Palearctic backswimmer, Notonecta maculata Fabricius, as a predator and deterrent of the highly invasive and health‐threatening Asian tiger mosquito, Aedes albopictus (Skuse) (Diptera: Culicidae). In central Italy, N. maculata is univoltine and overwinters in the adult stage. Females lay eggs from February to the end of May, and the first new adults will emerge in late June; the complete nymphal development requires 44.5 ± 3.1 days. The number of Ae. albopictus larvae preyed on by N. maculata during its growth increases while developing, going from 0.03 ± 0.02 larvae per day for first instar nymphs to 21.38 ± 2.90 for mature adults. Furthermore, the presence of a single N. maculata adult in a mosquito ovitrap is enough to discourage the Ae. albopictus oviposition for up to 5 days. Limiting mosquito populations and, consequently, the transmission of viruses and parasites should be our main goal. Therefore, the integrated management of Ae. albopictus by the use of insecticides and a predator (such as backswimmer juveniles and adults), even if only in specific situations, may be promising and feasible. A more in‐depth knowledge of the biological cycle of N. maculata could help, consequently, to optimize its mass rearing.

Genetic diversity and host specificity of Blastocystis in reptiles, Eastern Thailand

Blastocystis inhabits the digestive tracts of a diverse range of hosts. Transmission patterns, including host specificity, and the clinical and public health significance of Blastocystis in humans remain poorly understood. This study aimed to investigate the distribution and genetic diversity of Blastocystis in herbivorous and carnivorous reptiles in Eastern Thailand. A total of 501 faecal samples were collected from 363 iguanas, 79 bearded dragons, 50 tortoises, and nine snakes in an animal breeding farm in Chonburi Province, Eastern Thailand. Detection and differentiation of Blastocystis was based on amplification, sequencing, and phylogenetic analysis of specific small subunit (SSU) ribosomal RNA genes from faecal DNA extracted from the samples. Altogether 101/501 samples (20 %) were polymerase chain reaction (PCR) and sequencing-positive for Blastocystis, 90 (89 %) of which were from iguanas; the remaining positive samples were from African spurred tortoise (n=6), Bearded dragon (n=3), Leopard tortoise (n=1), and Red-footed tortoise (n=1). Phylogenetic analysis revealed that most of the Blastocystis sequences from iguanas were largely similar, and they were distinct from those of the tortoises. Subtype 17 was found in the three bearded dragons and likely reflected Blastocystis from prey animals. This is the largest survey of Blastocystis in reptiles to date. Remarkable differences in Blastocystis colonization rates and genetic diversity were observed between iguanas and other reptile orders, and what was considered Blastocystis colonization was only observed in herbivorous reptiles.

Red-on-Yellow Queen: Bio-Layer Interferometry Reveals Functional Diversity Within Micrurus Venoms and Toxin Resistance in Prey Species

Snakes in the family Elapidae largely produce venoms rich in three-finger toxins (3FTx) that bind to the α1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\upalpha _1$$\\end{document} subunit of nicotinic acetylcholine receptors (nAChRs), impeding ion channel activity. These neurotoxins immobilize the prey by disrupting muscle contraction. Coral snakes of the genus Micrurus are specialist predators who produce many 3FTx, making them an interesting system for examining the coevolution of these toxins and their targets in prey animals. We used a bio-layer interferometry technique to measure the binding interaction between 15 Micrurus venoms and 12 taxon-specific mimotopes designed to resemble the orthosteric binding region of the muscular nAChR subunit. We found that Micrurus venoms vary greatly in their potency on this assay and that this variation follows phylogenetic patterns rather than previously reported patterns of venom composition. The long-tailed Micrurus tend to have greater binding to nAChR orthosteric sites than their short-tailed relatives and we conclude this is the likely ancestral state. The repeated loss of this activity may be due to the evolution of 3FTx that bind to other regions of the nAChR. We also observed variations in the potency of the venoms depending on the taxon of the target mimotope. Rather than a pattern of prey-specificity, we found that mimotopes modeled after snake nAChRs are less susceptible to Micrurus venoms and that this resistance is partly due to a characteristic tryptophan→\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\rightarrow$$\\end{document}serine mutation within the orthosteric site in all snake mimotopes. This resistance may be part of a Red Queen arms race between coral snakes and their prey.

Harnessing Drones for Snow Leopard Conservation

Censusing snow leopard prey species like argali, ibex or blue sheep, is time-consuming, expensive, and challenging. We tested thermal-sensor-equipped drones to census ungulate populations in Mongolia’s Ikh Nart Nature Reserve. In 2019 and 2022 we used drones to detect wild ibex and argali. Here we report on 2022 findings: ~400 km along 5 fixed transects totaling forty-three missions, including several double count surveys. Drones detected 259 prey animals and 265 livestock; on average, 34% of all sightings were in areas obscured by topographic features from ground-based observers. Overall, tests reinforced the utility of drones for counting ungulates, along with highlighting important issues and future advances for supporting largely autonomous prey surveys. We recommend biologists build upon existing technology to attain an inexpensive, easy to use, and field ready set of equipment and procedures that can reliably improve or replace traditional walking or transect count methods for large prey species.

Prey can detect predators via electroreception in air

Predators and prey benefit from detecting sensory cues of each other's presence. As they move through their environment, terrestrial animals accumulate electrostatic charge. Because electric charges exert forces at a distance, a prey animal could conceivably sense electrical forces to detect an approaching predator. Here, we report such a case of a terrestrial animal detecting its predators by electroreception. We show that predatory wasps are charged, thus emit electric fields, and that caterpillars respond to such fields with defensive behaviors. Furthermore, the mechanosensory setae of caterpillars are deflected by these electrostatic forces and are tuned to the wingbeat frequency of their insect predators. This ability unveils a dimension of the sensory interactions between prey and predators and is likely widespread among terrestrial animals.

Mosquitoes do not influence Cotton Mouse (Peromyscus gossypinus) giving-up densities

Abstract It is commonly recognized that predation and the risk of predation can have profound effects on behaviors and population ecology of prey. Comparatively, little attention has been paid to the trade-offs hosts make to manage the risk of parasitism, but there is evidence that hosts make behavioral trade-offs to avoid parasitism in ways that resemble those made by prey animals under the risk of predation. Mosquitoes are common hematophagous ectoparasites which parasitize a wide range of vertebrates, resulting in blood loss, distraction, and disease transmission. Many hosts engage in defensive behaviors to repel or kill mosquitoes and these behaviors likely come at the expense of activities such as foraging and vigilance for predators. We placed a mosquito attractant (BG-Sweetscent) and repellant (allethrin) near artificial foraging patches in areas where mosquitoes were common and measured the amount of grain left after a night of foraging (giving-up density) to investigate whether mosquitoes influenced Cotton Mouse (Peromyscus gossypinus) foraging. We predicted that in patches with mosquito attractants, mosquito harassment would cause mice to engage in defensive behaviors which would distract or deter them from foraging, resulting in less grain consumption relative to control patches. Conversely, we predicted that in mosquito-repellent patches, mice would experience less harassment, resulting in more grain consumption. Indoor arena trials found no evidence that the mosquito treatments influenced cotton mouse behavior in the absence of mosquitoes. However, we found no evidence that mosquito treatments affected giving-up densities.

Metabarcoding analysis provides insight into the link between prey and plant intake in a large alpine cat carnivore, the snow leopard.

Species of the family Felidae are thought to be obligate carnivores. However, detection of plants in their faeces raises questions about the role of plants in their diet. This is particularly true for the snow leopard (Panthera uncia). Our study aimed to comprehensively identify the prey and plants consumed by snow leopards. We applied DNA metabarcoding methods on 90 faecal samples of snow leopards collected in Kyrgyzstan, employing one vertebrate and four plant markers. We found that argali (Ovis ammon) was detected only from male snow leopards. Myricaraia sp. was the most consumed among 77 plant operational taxonomic units found in snow leopard samples. It frequently appeared in samples lacking any prey animal DNA, indicating that snow leopards might have consumed this plant especially when their digestive tracts were empty. We also observed differences in the patterns of plant consumption between male and female snow leopards. Our comprehensive overview of prey and plants detected in the faeces of snow leopards and other sympatric mammals will help in formulating hypotheses and guiding future research to understand the adaptive significance of plant-eating behaviour in felids. This knowledge supports the enhancement of their captive environments and the conservation planning of their natural habitats.

Tonic immobility behaviour does not differ between fire salamander larvae from ponds and streams.

Tonic immobility is an antipredator defence in which the prey animal remains motionless after physical contact with the predator, pretending to be dead. This behaviour has been observed among a variety of taxa but has received only little attention in amphibian larvae. During our field studies with fire salamander larvae, we observed that larvae from different habitats display tonic immobility after handling. In our study site, we find larvae in pond and stream habitats, that differ in several aspects such as their stress response and their risk-taking behaviour, likely caused by the very different habitat conditions. We measured the time that the tonic immobility behaviour was displayed but found no difference between larvae from the two habitat types. Likewise, we also found no correlation between the size of the larvae and the duration of displaying the behaviour. In conclusion, we found that fire salamander larvae show tonic immobility, but found no evidence that the different habitat conditions influence the tonic immobility behaviour.

Modeling post-Pleistocene megafauna extinctions as complex social-ecological systems

Abstract The role of human hunting behavior versus climate change in the mass extinction of megafauna during the Late Quaternary is much debated. To move beyond monocausal arguments, we treat human–megafauna–environment relationships as social–ecological systems from a complex adaptive systems perspective, to create an agent-based model that tests how human hunting may interact with environmental stress and animal life history to affect the probability of extinction. Using the extinction of Syncerus antiquus in South Africa at 12–10 ka as a loose inspirational case study, we parameterized a set of experiments to identify cross-feedbacks among environmental dynamics, prey life history, and human hunting pressure that affect extinction probability in a non-linear way. An important anthropogenic boundary condition emerges when hunting strategies interrupt prey animal breeding cycles. This effect is amplified in patchy, highly seasonal environments to increase the chances of extinction. This modeling approach to human behavior and biodiversity loss helps us understand how these types of cross-feedback effects and boundary conditions emerge as system components interact and change. We argue that this approach can help translate archaeological data and insight about past extinction for use in understanding and combating the current mass extinction crisis.

The Stone, the Deer, and the Mountain: Lower Paleolithic Scrapers and Early Human Perceptions of the Cosmos

AbstractEvidence from the Levantine Late Lower Paleolithic sites of Jaljulia and Qesem Cave suggests that Quina scrapers, an innovation in a category of tools used mostly for butchery, emerged with changes in hunting practices. Quina scrapers were often made of non-local flint from the Samarian highlands, a home range of fallow deer populations throughout the ages. The predominance of fallow deer in the human diet following the disappearance of megafauna made scrapers key tools in human subsistence. Particular stone tools and particular prey animals, thus, became embedded in an array of practical, cosmological, and ontological conceptions whose origin we trace back to Paleolithic times. The mountains of Samaria, a source of both animals and stone under discussion, were part of this nexus. We present archaeological and ethnographic evidence of the practical and perceptual bonds between Paleolithic humans, animals, stones, and the landscape they shared.

Spatial prey availability and pulsed reproductive tactics: Encounter risk in a canid-ungulate system.

Predation risk is a function of spatiotemporal overlap between predator and prey, as well as behavioural responses during encounters. Dynamic factors (e.g. group size, prey availability and animal movement or state) affect risk, but rarely are integrated in risk assessments. Our work targets a system where predation risk is fundamentally linked to temporal patterns in prey abundance and behaviour. For neonatal ungulate prey, risk is defined within a short temporal window during which the pulse in parturition, increasing movement capacity with age and antipredation tactics have the potential to mediate risk. In our coyote-mule deer (Canis latrans-Odocoileus hemionus) system, leveraging GPS data collected from both predator and prey, we tested expectations of shared enemy and reproductive risk hypotheses. We asked two questions regarding risk: (A) How does primary and alternative prey habitat, predator and prey activity, and reproductive tactics (e.g. birth synchrony and maternal defence) influence the vulnerability of a neonate encountering a predator? (B) How do the same factors affect behaviour by predators relative to the time before and after an encounter? Despite increased selection for mule deer and intensified search behaviour by coyotes during the peak in mule deer parturition, mule deer were afforded protection from predation via predator swamping, experiencing reduced per-capita encounter risk when most neonates were born. Mule deer occupying rabbit habitat (Sylvilagus spp.; coyote's primary prey) experienced the greatest risk of encounter but the availability of rabbit habitat did not affect predator behaviour during encounters. Encounter risk increased in areas with greater availability of mule deer habitat: coyotes shifted their behaviour relative to deer habitat, and the pulse in mule deer parturition and movement of neonatal deer during encounters elicited increased speed and tortuosity by coyotes. In addition to the spatial distribution of prey, temporal patterns in prey availability and animal behavioural state were fundamental in defining risk. Our work reveals the nuanced consequences of pulsed availability on predation risk for alternative prey, whereby responses by predators to sudden resource availability, the lasting effects of diversionary prey and inherent antipredation tactics ultimately dictate risk.

Community's Knowledge of Leopard Cats' Roles in the Cisokan, West Java

Local communities have ways of managing and utilizing forest products, including leopard cats' habitat. Communities have knowledge and perceptions passed down from one generation to the next through community participation in their environment. This activity aims to reveal the community's knowledge regarding the role of leopard cats in the Cisokan. The implementation of this activity consists of collecting issues and data, FGD, and evaluation. The results show that almost all informants do not know the role of leopard cats in controlling prey animal populations and agricultural pests. Although leopard cats prey on domestic birds, they are not considered a nuisance to the community. After a joint discussion with the community regarding the ecological role of leopard cats, 79% of informants understood leopard cats' role in nature, which indirectly supported agriculture. Besides that, 70% of respondents understand that leopard cats should be protected.

Effects of metolachlor and fish cues on tadpole antipredator behaviors

Antipredator behaviors are often crucial for animal survival. In environments impacted by humans, animals may be exposed to a wide array of chemical contaminants due to agriculture, industry, and other activities. Among other effects, these chemical contaminants may influence behaviors prey animals use to cope with predation risk, likely reducing survival by suppressing or even maladaptively reversing normal behavioral responses. Changes in behavioral responses could be the result of impaired detection of cues that indicate predator presence or altered behavioral plasticity in response to predator cues. In a laboratory experiment, we tested the effects of the commonly used herbicide metolachlor on the behavior of tadpoles of the American bullfrog (Lithobates catesbeianus) in both the absence and presence of water conditioned with cues (odor) of fish. We observed several behaviors in the tadpoles reflective of predator avoidance when exposed to combinations of metolachlor (0 or 80 ppb) and the presence or absence of fish cues. We found that metolachlor had size-dependent effects on tadpole activity levels, with larger tadpoles being much less active in the absence of metolachlor but similar in activity to small tadpoles when metolachlor was present. Fish cues similarly had size-dependent effects on multiple tadpole behaviors. Finally, hiding behavior and zone change (movement) behavior of tadpoles in response to fish cues varied depending on the presence of metolachlor and, in the case of zone changes, tadpole size. Our findings indicate that the presence of chemical contaminants has the potential to alter important antipredator behaviors. However, these effects are complex, and size may mediate the nature of the response to both chemical contaminants and predators.

Physiological characterisation of aquatic traps in the epiphytic carnivorous plant Utricularia humboldtii

The suction traps of aquatic Utricularia species are discoid bladders, 1-6 mm long, with their lumen isolated by a mobile trapdoor from the ambient medium. Water is pumped out of the traps to maintain the negative pressure in the reset traps. When a prey animal touches the sensory hairs on the trapdoor it opens, the ambient water along with the prey is sucked inside and the trapdoor is closed again. Utricularia humboldtii is a robust, semiaquatic-epiphytic or terrestrial species from the generic section Orchidioides from South America. The efficiency of its aquatic traps was measured based on trap firing and resetting rates as well as changes in trap thickness due to both mechanically stimulated and spontaneous firings using an electronic sensor. The U. humboldtii traps exhibited relatively low firing and resetting rates. These values are 2 to 20 times lower than those in other aquatic Utricularia species reported in the literature. These results together with the low aerobic respiration rate of sliced traps indicate that the less efficient aquatic traps in U. humboldtii are specialised for catching fine prey items in bromeliad water tanks. A marked lag-period in trap resetting was found to occur during the first 30 min after firing, contradicting the accepted concept of continuous water pumping. Spontaneous trap firings were also observed with the same magnitude as that in stimulated firings. This implies that spontaneous firings occur consistently in all the tested aquatic Utricularia species. However, although they relate to the continuous water pumping mechanism of the traps, their physiological importance has not been fully elucidated.