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opencc-zeroJan 2024View details →

PFOS negatively impacts prey capture in larval zebrafish

Per- and polyfluoroalkyl substances (PFAS) are widely used in many industrial and domestic applications. The wide range use of PFAS has resulted in unintentional human exposures and bioaccumulation in blood and other organs. Perfluorooctanesulfonate (PFOS) is among the most prevalent PFAS in the environment and has been postulated to affect brain functions in exposed organisms. However, the impacts of PFOS on early neural development have not been well-described. Here, we used zebrafish larvae to assess the effects of PFOS on two fundamental complex behaviors, prey capture and learning. Zebrafish exposed to PFOS concentrations ranging from 2 – 20 µM for differing 48-hour periods were viable through early larval stages. In addition, PFOS uptake was unaffected by the presence of a chorion. We employed two different experimental paradigms; we first assessed the impacts of increasing organismal PFOS bioaccumulation on prey capture and learning, and second, we probed stage-specific sensitivity to PFOS by exposing zebrafish at different developmental stages (0-2 vs 3-5 days post fertilization). Following both assays we measured the amount of PFOS present in each larva. PFOS levels varied in larvae from different groups within each experimental paradigm. Significant negative correlations were observed between larval PFOS accumulation and the percentage of captured prey, while non-significant negative correlations were observed between PFOS accumulation and experienced-induced prey capture learning. These findings suggest that PFOS accumulation negatively affects larval zebrafish's ability to perform complicated multisensory behaviors and highlight potential risks of PFOS exposure to animals in the wild, with implications for human health.

opencc-zeroJan 2024View details →

Data for: Spatial prey availability and pulsed reproductive tactics: encounter risk in a canid-ungulate system

<ol> <li>Predation risk is a function of spatiotemporal overlap between predator and prey, as well as behavioral 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 behavior. For neonatal ungulate prey, risk is defined within a short temporal window during which the pulse in parturition, increasing movement capacity with age, and anti-predation tactics have the potential to mediate risk.</li> <li>In our coyote – mule deer (Canis latrans – Odocoileus hemionus) system, leveraging GPS data collected from both predator and prey, we tested expectations of the shared enemy and reproductive risk hypotheses. We asked two questions regarding risk: (A) how do primary and alternative prey habitat, predator and prey activity, and reproductive tactics (e.g., birth synchrony, maternal defense) influence vulnerability of a neonate encountering a predator? (B) How do the same factors affect behavior by predators relative to time before and after an encounter?</li> <li>Despite increased selection for mule deer and intensified search behavior 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 behavior during encounters. Encounter risk increased in areas with greater availability of mule deer habitat, coyotes shifted their behavior 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.</li> <li>In addition to the spatial distribution of prey, temporal patterns in prey availability, and animal behavioral 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.</li> </ol>

opencc-zeroFeb 2024View details →

Data from: Parental overproduction allows siblicidal bird to adjust brood size to climate-driven prey variation

Parental overproduction is hypothesized to hedge against uncertainty over food availability and stochastic death of offspring and to improve brood fitness. Understanding the evolution of overproduction requires quantifying its benefits to parents across a wide range of ecological conditions, which has rarely been done. Using a multiple hypotheses approach and 30 years of data, we evaluated the benefits of overproduction in the Blue-footed booby, a seabird that lays up to three eggs asynchronously, resulting in an aggressive brood hierarchy that facilitates the death of last-hatched chicks under low food abundance. Results support the resource-tracking hypothesis, as low prey abundance (estimated from sea surface temperature and chlorophyll-a concentration) led to rapid brood reduction. The insurance hypothesis was supported in broods of three, where last-hatched chicks' survival increased after a sibling's death. Conversely, in broods of two, results suggested that parents abandoned last-hatched chicks following first-hatched chicks' deaths. No direct evidence supported the facilitation hypothesis: the presence of a last-hatched chick during development did not enhance its sibling's fitness in the short or long term. The value of last-hatched offspring to parents, as "extra" or "insurance" varied with indices of food abundance, brood size, and parental age. Ninety percent of overproduction benefits came from enabling parents to capitalize on favorable conditions by fledging additional offspring. Our study provides insight into the forces driving overproduction, explaining the adaptiveness of this apparently wasteful behavior and allowing us to better predict how overproduction's benefits might be modified by ocean warming.

Predator metamorphosis and its consequence for prey risk assessment

Living with a diverse array of predators provides a significant challenge for prey to learn and retain information about each predator they encounter. Consequently, some prey respond to novel predators because they have previous experience with a perceptually similar predator species, a phenomenon known as generalization of predator recognition. However, it remains unknown whether prey can generalize learned responses across ontogenetic stages of predators. Using wood frog (Lithobates sylvaticus) tadpole prey we conducted two experiments to explore the extent of predator generalization of different life stages of two different predators: (1) predacious diving beetles (Dytiscus sp.) and (2) tiger salamanders (Ambystoma mavortium). In both experiments, we used chemical alarm cues (i.e., injured conspecific cues) to condition tadpoles to recognize the odor of either the larval or adult stage of the predator as risky. One day later, we tested tadpoles with either the larval or adult predator odor to determine whether they generalized their learned responses to the other life stages of the predator. Tadpoles generalized between larval and adult beetle odors but failed to generalize between larval and adult salamander odors. These results suggest that the odor of some predator species changes during metamorphosis to an extent that reduces their recognisability by prey. This 'predator identity reset' increases the number of threats to which prey need to attend.

Effects of ingesting large prey on the kinematics of rectilinear locomotion in Boa constrictor

Large and stout snakes commonly consume large prey and use rectilinear crawling, yet, whether body wall distention after feeding impairs rectilinear locomotion is poorly understood. After eating large prey (30-37% body mass), all Boa constrictor tested could perform rectilinear locomotion in the region with the food bolus despite a greatly increased distance between the ribs and the ventral skin that likely lengthens muscles relevant to propulsion. Unexpectedly, out of eleven kinematic variables, only two changed significantly (P<0.05) after feeding: cyclic changes in snake height increased by more than 1.5x and the longitudinal movements of ventral skin relative to the skeleton decreased by more than 25%. Additionally, cyclic changes in snake width suggest that the ribs are active and mobile during rectilinear locomotion particularly in fed snakes, but also in unfed snakes. These kinematic changes suggest that rectilinear actuators reorient more vertically and undergo smaller longitudinal excursions following large prey ingestion, both of which likely act to reduce elongation of these muscles that may otherwise experience substantial strain.

Rapid evolution of consumptive and non-consumptive predator effects on prey population densities, bioenergetics and stoichiometry

Predators can strongly influence prey populations not only through consumptive effects (CE) but also through non-consumptive effects (NCE) imposed by predation risk. Yet, the impact of NCE on bioenergetic and stoichiometric body contents of prey, traits that are shaping life histories, population and food web dynamics, is largely unknown. Moreover, the degree to which NCE can evolve and can drive evolution in prey populations is rarely studied. A 6-week outdoor mesocosm experiment with Caged-Fish (NCE) and Free-Ranging-Fish (CE and NCE) treatments was conducted to quantify and compare the effects of CE and NCE on population densities, bioenergetic and stoichiometric body contents of Daphnia magna, a keystone species in freshwater ecosystems. We tested for evolution of CE and NCE by using experimental populations consisting of D. magna clones from two periods of a resurrected natural pond population: a pre-fish period without fish and a high-fish period with high predation pressure. Both Caged-Fish and Free-Ranging-Fish treatments decreased the body size and population densities, especially in Daphnia from the high-fish period. Only the Free-Ranging-Fish treatment affected bioenergetic variables, while both the Caged-Fish and Free-Ranging-Fish treatments shaped body stoichiometry. The effects of CE and NCE were different between both periods indicating their rapid evolution in the natural resurrected population. Both the Caged-Fish and Free-Ranging-Fish treatments changed the clonal frequencies of the experimental Daphnia populations of the pre-fish as well as the high-fish period, indicating that not only CE but also NCE induced clonal sorting, hence rapid evolution during the mesocosm experiment in both periods. Our results demonstrate that CE as well as NCE have the potential to change not only the body size and population density but also the bioenergetic and stoichiometric characteristics of prey populations. Moreover, we show that these responses not only evolved in the studied resurrected population, but that CE and NCE also caused differential rapid evolution in a time frame of 6 weeks (ca. 4-6 generations). As NCE can evolve as well as can drive evolution, they may play an important role in shaping eco-evolutionary dynamics in predator-prey interactions.

Data from: Assessing springtime vertebrate prey of sympatric mesopredators in the southeastern United States using metabarcoding analysis

Coyotes (Canis latrans) colonized the eastern United States over the last century and formed a 3-species predator guild with bobcats (Lynx rufus) and gray foxes (Urocyon cinereoargenteus) across much of the southeastern United States. Diets among the three species vary along with respective impacts on game species such as white-tailed deer (Odocoileus virginianus) and wild turkeys (Meleagris gallopavo). To determine predation impacts on vertebrate prey and dietary overlap in consumption of prey items, we assessed diets of coyote, bobcat, and gray fox during spring, coinciding with white-tailed deer fawning and wild turkey nesting and brood rearing. We sampled across three sites along the Savannah River in South Carolina from mid-May through mid-June of 2020-2021. We collected 180 scat samples along 295.9 kilometers (71.1 – 122.4 km/site) of unpaved secondary roads and used DNA metabarcoding to determine vertebrate diet items. We identified predator species of scat using DNA metabarcoding and species-specific mtDNA fragment analysis (153 were coyotes, 20 bobcats, and seven gray foxes). Overall, we found evidence that two species, coyote and bobcat, consumed deer while all three consumed turkeys. The frequency of deer in the diet varied across sites for coyotes from 62 – 86% and wild turkey was present with a frequency of occurrence of 9% for coyotes, 5% for bobcats, and 14% for gray fox. Vertebrate diet specialization was evident across predator species with a high frequency of deer in coyote diets, rabbits and small mammals in bobcat diets, and herpetofauna in gray fox diets. During deer fawning and wild turkey nesting and brood rearing, dietary overlap appears to be mediated by the disparate selection of prey items, which reduced competition among coyotes, bobcats, and gray foxes. The use of DNA metabarcoding may augment our understanding of dietary preferences within this predator guild by providing increased resolution of diet composition among important game species.

Figure 5 in Portia labiata (Araneae: Salticidae: Spartaeini) as predator and prey of a synanthropic Parasteatoda sp. (Araneae: Theridiidae: Theridiinae)

Figure 5. Prominent arachnologists responsible for the naming of Portia labiata. 1, Tord Tamberlan Teodor Thorell (1830-1901), Swedish arachnologist who first described a female Portia labiata (as Linus labiatus) from Burma in 1887. 2, Ferdinand Anton Franz Karsch (1853-1936), German arachnologist who named the genus Portia in 1878. It was only much later (Wanless 1978) that labiata was recognized as a Portia by Fred Wanless (1940-2017).

Figure 4 in Portia labiata (Araneae: Salticidae: Spartaeini) as predator and prey of a synanthropic Parasteatoda sp. (Araneae: Theridiidae: Theridiinae)

Figure 4 (continued from previous page). 6, Male feeding on a captured spider. 7, Penultimate male feeding on a captured spiderling. This male feed on a series of immatures from this brood. 8, Frontal view of adult male. Note the prominent retrolateral tibial apophysis and basal cymbial apophysis of each pedipalp. Male and female P. albimana have a much more extensive cover of white setae on their face and pedipalps.

Figure 3 in Portia labiata (Araneae: Salticidae: Spartaeini) as predator and prey of a synanthropic Parasteatoda sp. (Araneae: Theridiidae: Theridiinae)

Figure 3. Sequential photos (1-3) showing a nesting female Parasteatoda sp. feeding on a male Portia labiata (Karnataka, 20 JUN 2022). Photo credits: 1-3, Sanath R M.

Figure 2 in Portia labiata (Araneae: Salticidae: Spartaeini) as predator and prey of a synanthropic Parasteatoda sp. (Araneae: Theridiidae: Theridiinae)

Figure 2. Sequential photos (1-12) showing the capture of a female Portia labiata by a female Parasteatodes (Karnataka). The Portia approached this Parasteatodes from a distance but became entangled in her silk as the Parasteatodes wrapped her with more silk (1-3). Subsequently the Portia was bitten (4), then wrapped with more silk, and eaten (9, 11). Photo credits: 1-12, Vipin Baliga.

Figure 4 in Portia labiata (Araneae: Salticidae: Spartaeini) as predator and prey of a synanthropic Parasteatoda sp. (Araneae: Theridiidae: Theridiinae)

Figure 4 (continued on next page). Female (1-2) and male (3-8) Portia labiata from Karnataka. 1, Female guarding her brood. 2, Female feed on a captured spider. 3, Adult male (missing leg L4). 4-5, Adult male feeding on a nematoceran. Note the broad, white bands on the margins of the carapace,

Figure 1 in Portia labiata (Araneae: Salticidae: Spartaeini) as predator and prey of a synanthropic Parasteatoda sp. (Araneae: Theridiidae: Theridiinae)

Figure 1. Sequential photos (1-3) showing a female Portia labiata feeding on a female Parasteatoda sp. that she has captured (Karnataka, 2 FEB 2021). Note the presence of a small kleptoparasitic spider (arrows). Photo credits: 1-3, Abhijith APC.

opencc-zeroApr 2024View details →

Limnomysis benedeni ingestion rate in different prey

Understanding the diet preferences and food selection of invasive species is crucial to better predict their impact on community structure and ecosystem functioning. Limnomysis benedeni, a Ponto-Caspian invasive mysid shrimp, is one of the most successful invaders in numerous European river and lake ecosystems. While existing studies suggest potentially strong trophic impact due to high predation pressure on native plankton communities, little is known of its food selectivity between phyto- and zooplankton, under different food concentrations. Here, we therefore investigated the feeding selectivity of L. benedeni on two commonly occurring prey organisms in freshwaters, the small rotifer zooplankton Brachionus calyciflorus together with the microphytoplankton Cryptomonas sp. present in increasing densities. Our results demonstrated a clear shift in food selection, with L. benedeni switching from B. calyciflorus to Cryptomonas sp. already when the two prey species were provided in equal biomasses. Different functional responses were observed for the two food types, indicating somewhat different foraging mechanisms for each food type. These findings provide experimental evidence on the feeding flexibility of invasive mysid shrimps and potential implications for trophic interactions in invaded ecosystems.

opencc-zeroApr 2024View details →

Data from: Urbanization and primary productivity mediate the predator-prey relationship between deer and coyotes

Predator-prey interactions are important to regulating populations and structuring communities but are affected by many dynamic, complex factors, across larges-scales, making them difficult to study. Integrated population models (IPMs) offer a potential solution to understanding predator-prey relationships by providing a framework for leveraging many different datasets and testing hypotheses about interactive factors. Here, we evaluate the coyote-deer (Canis latrans – Odocoileus virginianus) predator-prey relationship across the state of North Carolina (NC). Because both species have similar habitat requirements and may respond to human disturbance, we considered net primary productivity (NPP) and urbanization as key mediating factors. We estimated deer survival and fecundity by integrating camera trap, harvest, biological and hunter observation datasets into a two-stage, two-sex Lefkovich population projection matrix. We allowed survival and fecundity to vary as functions of urbanization, NPP and coyote density and projected abundance forward to test eight hypothetical scenarios. We estimated initial average deer and coyote densities to be 11.83 (95% CI: 5.64, 20.80) and 0.46 (95% CI: 0.02, 1.45) individuals/km2, respectively. We found a negative relationship between current levels of coyote density and deer fecundity in most areas which became more negative under hypothetical conditions of lower NPP or higher urbanization, leading to lower projected deer abundances. These results suggest that coyotes could have stronger effects on deer populations in NC if their densities rise, but primarily in less productive and/or more suburban habitats. Our case study provides an example of how IPMs can be used to better understand the complex relationships between predator and prey under changing environmental conditions.

opencc-zeroDec 2021View details →

Fish resist temptation from junk food: State-dependent diet choice in reproductive Atlantic cod (Gadus morhua) facing seasonal fluxes of lipid-rich prey

In ecological sciences, animal diets are often simplified to "resources" or "caloric quantities". However, in the present study, we investigated the optimal foraging strategy of Atlantic cod (Gadus morhua) when both macro- and micro-nutritional requirements are accounted for. Proteins cannot be synthesized from fatty acids, so the proteins for gonad development must come from other dietary sources. In addition, micronutrients are required in smaller quantities. For example, for cod, arachidonic acid (ARA) acts as a micronutrient precursor for prostaglandins, which is important for reproduction. We formulated a dynamic state-dependent model to make predictions about optimal diet choice and foraging behavior. We applied the model to a case study in the strait between Denmark and Sweden. The model predicted that energy acquired from dietary protein should be twice that acquired from lipids, with a small increase in the lipid requirements when gonads are growing. The model also predicted that the "energy sparing effect of lipids" made it beneficial to engage in risky foraging activity to supplement a lean diet with a little bit of fat. When we re-constructing the model to also optimize ARA uptake, the cod consumed relatively more ARA-rich crabs in the months prior to spawning, despite the otherwise poor energetic value of this prey. In support of the model predictions, field observations indicated that lipid stores reached a peak shortly after the arrival of the lipid-rich migrating herring and the fatty acid signal of these herring were evident in the liver of nearly all cod. Three month later, only half of the cod contained the herring-derived fatty acid signal, supporting the predicted shift in prey type prior to spawning. From these model predictions and field observations, we conclude that, also in the wild, nutritional requirements can be at least as important as pure energy acquisition.

opencc-zeroFeb 2022View details →

Weak effects of birds, bats and ants on their arthropod prey on pioneering tropical forest gap vegetation

The relative roles of plants competing for resources versus top-down control of vegetation by herbivores, in turn impacted by predators, during early stages of tropical forest succession remain poorly understood. Here we examine the impact of insectivorous birds, bats and ants exclusion on arthropods communities on replicated 5x5 m of pioneering early successional vegetation plots in lowland tropical forest gaps in Papua New Guinea. In plots from which focal taxa of predators were excluded we observed increased biomass of herbivorous and predatory arthropods, and increased density, and decreased diversity of herbivorous insects. However, changes in the biomass of plants, herbivores and arthropod predators were positively correlated or uncorrelated between these three trophic levels and also between individual arthropod orders. Arthropod abundance and biomass correlated strongly with the plant biomass irrespective of the arthropods' trophic position – a signal of bottom-up control. Patterns in herbivore specialization confirm lack of a strong top-down control and were largely unaffected by the exclusion of insectivorous birds, bats and ants. No changes of plant-herbivore interaction networks were detected except for decrease in modularity of the exclosure plots. Our results suggest weak top-down control of herbivores, limited compensation between arthropod and vertebrate predators, and limited intra-guild predation by birds, bats and ants. Possible explanations are strong bottom-up control, a low activity of the higher order predators, especially birds, possibly also bats, in gaps, and continuous influx of herbivores from surrounding mature forest matrix.

opencc-zeroFeb 2022View details →

Thermal plasticity and evolution shape predator-prey interactions differently in clear and turbid water

Warming and eutrophication negatively affect freshwater ecosystems by modifying trophic interactions and increasing water turbidity. We need to consider their joint effects on predator-prey interactions, and how these depend on the thermal evolution of both predator and prey. We quantified how 4°C warming and algae-induced turbidity (that integrates turbidity per se and increased food for zooplankton prey) affect functional response parameters and prey population parameters in a common-garden experiment. We did so for all combinations of high- and low-latitude predator (damselfly larvae) and prey (water fleas) populations to assess the potential impact of thermal evolution of predators and/or prey at a high latitude under warming using a space-for-time substitution. We then modelled effects on the system stability (i.e. tendency to oscillate) under different warming, turbidity and evolutionary scenarios. Warming and turbidity had little effect on the functional response parameters of high-latitude predators. In contrast, warming and turbidity reduced the handling times of low-latitude predators. Moreover, warming increased the search rates of low-latitude predators in clear water but instead decreased these in turbid water. Warming increased stability (i.e. prevented oscillations) in turbid water (except for the "high-latitude predator & high-latitude prey" system), mainly by decreasing the prey's carrying capacity and partly also by decreasing search rates, while it did not affect stability in clear water. Algae-induced turbidity generally decreased stability, mainly by increasing the prey's carrying capacity and partly also by increasing search rates. This resembles findings that nutrient enrichment can reduce the stability of trophic systems. The expected stability of the high-latitude trophic system under warming was dependent on the turbidity level: our results suggest that thermal plasticity tends to destabilize the high-latitude trophic system under warming in clear water but not in turbid water, and that thermal evolution of the predator will stabilize the high-latitude system under warming in turbid water but less so in clear water. The extent to which thermal plasticity and evolution shape trophic system stability under warming may strongly differ between clear and turbid water bodies, with their contributions having a more stabilizing role in turbid water.

opencc-by-nd-4.0Nov 2021View details →

Figure 7 in Spiders that prey on jumping spiders (Araneae: Salticidae)

Figure 7. Wandering spiders preying on salticids. 1-3, Eutichurid spider of the genus Cheiracanthium C. L. Koch 1839 preying on a female salticid of the genus Epeus, in her nest. 4-6, Corinnid of the genus Corinnomma Karsch 1880 feeding on an adult male salticid, Myrmarachne plataleoides. 7, Corinnomma feeding on a salticid of the genus Asemonea O. Pickard- Cambridge 1869. Photo credits: 1-3, 7, Abhijith A. P. C.; 4-6, M. Jithesh Pai.