Predation Success Research Articles

Light at night disrupts trophic interactions and population growth of lady beetles and pea aphids.

Natural variation in light has historically correlated with seasonality, providing an honest cue to organisms with seasonal life history cycles. However, with the onset of widespread light at night (LAN), the reliability of light as a cue has decreased in polluted areas, making its timing or intensity potentially clash with temperature trends. These clashing cues may influence biological systems on multiple levels. Yet, a few studies have connected behavioral underpinnings and larger community-level processes, resulting in a knowledge gap bridging individual-, population-, and community-level responses to mismatched cues. We experimentally investigated impacts of cool temperature and LAN on a lady beetle-aphid-fava system to test how light and temperature influenced aphid population growth and their underlying behavioral drivers. We used Coccinella septempunctata and Coleomegilla maculata beetles to understand the interaction of the environment and predation on pea aphid (Acyrthosiphon pisum) population growth. Aphids and their predators reacted differently to variation in light and temperature, influencing the strength of aphid-driven and predator-driven dynamics in the different conditions. We observed evidence of aphid-driven dynamics in the cool, light conditions where aphids excel and exhibited strong anti-predator behavior. In contrast, we found stronger predator-driven dynamics in warm conditions where lady beetle predatory success was higher. Overall, we found that LAN has context-dependent effects on insect communities due to the varied responses each player has to its environment.

Spatial Memory Drives Foraging Strategies of Wolves, but in Highly Individual Ways

The ability of wild animals to navigate and survive in complex and dynamic environments depends on their ability to store relevant information and place it in a spatial context. Despite the centrality of spatial memory, and given our increasing ability to observe animal movements in the wild, it is perhaps surprising how difficult it is to demonstrate spatial memory empirically. We present a cognitive analysis of movements of several wolves (Canis lupus) in Finland during a summer period of intensive hunting and den-centered pup-rearing. We tracked several wolves in the field by visiting nearly all GPS locations outside the den, allowing us to identify the species, location and timing of nearly all prey killed. We then developed a model that assigns a spatially explicit value based on memory of predation success and territorial marking. The framework allows for estimation of multiple cognitive parameters, including temporal and spatial scales of memory. For most wolves, fitted memory-based models outperformed null models by 20 to 50% at predicting locations where wolves chose to forage. However, there was a high amount of individual variability among wolves in strength and even direction of responses to experiences. Some wolves tended to return to locations with recent predation success—following a strategy of foraging site fidelity—while others appeared to prefer a site switching strategy. These differences are possibly explained by variability in pack sizes, numbers of pups, and features of the territories. Our analysis points toward concrete strategies for incorporating spatial memory in the study of animal movements while providing nuanced insights into the behavioral strategies of individual predators.

Climate change may plunder the facultative top predator Yellow-throated Martin from the Hindu-Kush Himalayan Region

The mountain ecosystems are fragile because of topography and extreme climatic conditions. The Hindu-Kush Himalayan (HKH) region is a biodiversity-rich ecosystem and highly vulnerable to climate change and anthropogenic activities among the mountains. In HKH, the climate change impacts on ecologically specialist species are already evident, but generalist species are not much studied. One such generalist species distributed throughout the HKH is Yellow-Throated Marten (YTM) (Martes flavigula Boddaert, 1785), a facultative predator that occupies the Southern flank of the HKH. The YTM is one of the least studied animals distributed up to 4510-m elevation. The HKH covers 61 terrestrial ecoregions and 304 Protected Areas (PAs). An ecologically successful facultative predator of the region is seriously threatened because of habitat loss and climate change. Hence, we used an ensemble model to map the distribution of suitable habitats and their representativeness in terms of ecoregions and PA coverage. The results indicated that by 2050, the distribution range might decline to 58.78% and 49.33% with reference to the current scenario under the representative concentration pathway (RCP) 4.5 and 8.5 scenarios, respectively. The species may lose much of its range, mainly in the eastern part of the HKH landscape. Furthermore, the centroid of the distribution may also shift to the northwest, thereby abandoning many areas and occupying new refugia. The Upper Gangetic plains moist deciduous forests ecoregion possess the highest suitable habitats for the YTM, with a mean value of 0.744. At the same time, the existing PA network represents only 12.2% of its suitable habitat in HKH. Hence, for the long-term viability of the species, there is a need to enhance protection and improve habitat quality.

TEMPERATURE-BASED AMBUSH SITE SELECTION IN SIDEWINDER RATTLESNAKES (CROTALUS CERASTES)

Body temperature influences the activity and behavior of reptiles, with warmer body temperatures typically being associated with improved performance. Nocturnal ambush-hunting rattlesnakes would therefore benefit from selecting warmer substrate hunting sites, allowing them to stay in ambush longer as the environment cools and, presumably, to have a higher probability of striking prey successfully. Here, we tested whether free-ranging sidewinder rattlesnakes (Crotalus cerastes) might select ambush sites based on substrate temperature. We used a thermal imaging camera to measure snake body temperature and substrate temperature at ambush sites and random locations. Rattlesnake body temperature showed a strong positive correlation with substrate temperature at the ambush site, and the substrate at ambush sites was significantly warmer than randomly chosen sites. This suggests snakes might select ambush sites based on substrate temperature. Desert pit vipers appear highly attuned to environmental conditions and might integrate several criteria to select microhabitats that increase predation success.

Beyond the encounter: Predicting multi-predator risk to elk (Cervus canadensis) in summer using predator scats.

There is growing evidence that prey perceive the risk of predation and alter their behavior in response, resulting in changes in spatial distribution and potential fitness consequences. Previous approaches to mapping predation risk across a landscape quantify predator space use to estimate potential predator‐prey encounters, yet this approach does not account for successful predator attack resulting in prey mortality. An exception is a prey kill site that reflects an encounter resulting in mortality, but obtaining information on kill sites is expensive and requires time to accumulate adequate sample sizes.We illustrate an alternative approach using predator scat locations and their contents to quantify spatial predation risk for elk (Cervus canadensis) from multiple predators in the Rocky Mountains of Alberta, Canada. We surveyed over 1300 km to detect scats of bears (Ursus arctos/U. americanus), cougars (Puma concolor), coyotes (Canis latrans), and wolves (C. lupus). To derive spatial predation risk, we combined predictions of scat‐based resource selection functions (RSFs) weighted by predator abundance with predictions that a predator‐specific scat in a location contained elk. We evaluated the scat‐based predictions of predation risk by correlating them to predictions based on elk kill sites. We also compared scat‐based predation risk on summer ranges of elk following three migratory tactics for consistency with telemetry‐based metrics of predation risk and cause‐specific mortality of elk.We found a strong correlation between the scat‐based approach presented here and predation risk predicted by kill sites and (r = .98, p < .001). Elk migrating east of the Ya Ha Tinda winter range were exposed to the highest predation risk from cougars, resident elk summering on the Ya Ha Tinda winter range were exposed to the highest predation risk from wolves and coyotes, and elk migrating west to summer in Banff National Park were exposed to highest risk of encountering bears, but it was less likely to find elk in bear scats than in other areas. These patterns were consistent with previous estimates of spatial risk based on telemetry of collared predators and recent cause‐specific mortality patterns in elk.A scat‐based approach can provide a cost‐efficient alternative to kill sites of quantifying broad‐scale, spatial patterns in risk of predation for prey particularly in multiple predator species systems.

Impacts of Light and Food Availability on Early Development of Cassiopea Medusae

The Cassiopea genus is an emergent focus for behavioral, ecological, and genetic research. Cassiopea ephyrae, a key intermediate in the life cycle of this benthic jellyfish, have been left out of much work on the genus. Here we investigate the Cassiopea xamachana ephyra response to six combinations of light and feeding regimes. We show that zero light condition results in fast bleaching of ephyrae and significant reductions in bell size and predation success. We also show that ephyrae starved in sub-compensation level light experienced only meager reductions in size over 42 days, and those starved in zero light were still largely recoverable at 28 days. Developmental trajectories on various metrics of Cassiopea xamachana ephyrae were significantly impacted by both light and feeding level in the first 42 days of life.

In natura sit-and-wait behaviour and predation success of a Neotropical dance fly (Diptera: Hybotidae)

ABSTRACT In this study, we provide detailed ethological notes on the predation behaviour of Chvalaea yolkamini Jaume-Schinkel, Soares & Barros, 2020, a neotropical sit-and-wait dance fly from Mexico, with description and video evidence of hunting and feeding behaviours. Furthermore, we analysed in situ predation success in relation to biotic and abiotic factors (prey size, prey taxonomic group, temperature, humidity and perch height). We observed 94 individuals for a total of ~15.68 hours. Chvalaea yolkamini uses its hind legs armed with spikes to strike and handle prey, while its short proboscis pierces and sucks on intersegmental areas as they are less sclerotised. Feeding time ranged from 1.27 to 15.24 minutes. In addition, C. yolkamini was more successful when attacking large-sized prey, but apparently the limit for prey size is the predator’s own size. The individuals were more successful when ambushing large Brachycera than relatively small nematocerous Diptera and Hemiptera. No influence of temperature and humidity was detected, but higher perches favoured predation success. Our study supplies the first detailed information on the perching and hunting behaviour of a sit-and-wait hybotid fly. We advance hypotheses that may be investigated by including covariables, such as wind and prey colouration, with a view to further our comprehension of the sit-and-wait behaviour in predatory animals.

The genetic architecture underlying prey-dependent performance in a microbial predator

Natural selection should favour generalist predators that outperform specialists across all prey types. Two genetic solutions could explain why intraspecific variation in predatory performance is, nonetheless, widespread: mutations beneficial on one prey type are costly on another (antagonistic pleiotropy), or mutational effects are prey-specific, which weakens selection, allowing variation to persist (relaxed selection). To understand the relative importance of these alternatives, we characterised natural variation in predatory performance in the microbial predator Dictyostelium discoideum. We found widespread nontransitive differences among strains in predatory success across different bacterial prey, which can facilitate stain coexistence in multi-prey environments. To understand the genetic basis, we developed methods for high throughput experimental evolution on different prey (REMI-seq). Most mutations (~77%) had prey-specific effects, with very few (~4%) showing antagonistic pleiotropy. This highlights the potential for prey-specific effects to dilute selection, which would inhibit the purging of variation and prevent the emergence of an optimal generalist predator.

The spatial ecology of black-backed jackals (Canis mesomelas) in a protected mountainous grassland area

An animal’s ability to traverse a landscape and utilise available resources is vital for its survival. The movement patterns of an animal provide insight into space use, activity patterns and ecological requirements that are imperative for successful farming and wildlife management practices. Home ranges are often used as a measurement of space use, which provides a quantitative value of an animal’s movement patterns in relation to various biological factors. A factor that is often overlooked in the analysis of movement patterns is the effect of moon phase, despite its known impact on the activity and hunting success of nocturnal predators. We live-trapped, radio-collared and monitored five black-backed jackals (Canis mesomelas) in the Golden Gate Highlands National Park, South Africa, between 2018 and 2019 to determine the impact of various environmental factors on movement patterns. Annual home ranges varied between individuals, were larger in subadults and overlapped between three jackals. Space use and travel velocity suggested a crepuscular activity pattern with a reliance on nocturnal activity and limited diurnal activity. Individual space use suggested variation between moon phases, although overall variation was negligible. Jackals travelled farther during new moon, compared with full moon, with the most notable difference between 23:00 and 04:00. Our results suggest that jackal behaviour does not align with the predation risk hypothesis. Space use and travel velocities varied between seasons, possibly because of differences in activity during mating and pupping periods. Our study confirms the flexibility in jackal space use and suggests a possible relationship with moon phase. To properly understand movement patterns at an individual and population level, we encourage additional research about jackals and various environmental factors via multidisciplinary collaborations.

Multiple cues guarantee successful predation by a Neotropical wasp

Abstract Predatory social wasps are well studied in several aspects; however, foraging behaviour, especially that which takes place away from the nest at often unpredictable locations, or specialized behaviours to find and subdue prey are not well understood. In the Brazilian tropical savanna, the Polistinae wasp Brachygastra lecheguana is specialized in preying on some endophytic weevil larvae which develops inside floral buds. We hypothesized that these wasps utilize a combination of different mechanisms such as visual, chemical (odour) and possible tactile cues to find the weevil larvae. Using a combination of experimental manipulations (visual; chemical; visual/chemical) we tested the wasp’s ability to detect the endophytic larvae in the field. Additionally, we checked the ability of this wasp to detect vibrations produced by the weevils inside the buds. Our results suggest that the B. lecheguana wasp utilizes a sequence of eco-physiological mechanisms to find the endophytic larva inside floral buds: sight, smell, and perhaps touch. The use of multiple cues by this wasp guarantees such a high rate of predation on endophytic beetles that the wasp may have positive implications (reduction in weevils’ infestation) for the future of the host plant’s reproduction.

Does tagging transparent fish increase predation risk? A laboratory study with glass eel (Anguilla anguilla) and sea bass (Dicentrarchus labrax).

Barriers in the estuaries of the rivers prevent the immigration of glass eels (Anguilla anguilla) arriving on the European coast every spring. This leads to an unnatural accumulation of migrating glass eels below the barriers, and this may lead to additional losses in glass eels by piscivorous fish. The proportion of predation losses can be estimated using mark‐recapture techniques and abundance estimates in combination with stomach content analysis of piscivorous fish. Nonetheless, whether tagging transparent glass eels increases predation risk and what the digestion rate of glass eel is in piscivorous fish are unknown. This study aimed to determine whether there is an increased predation risk for tagged glass eel; it also studies glass eel digestion status in piscivorous fish after appointed time frames. A laboratory experiment with 48 trials was conducted. Tagged (visible implanted elastomer, VIE) and untagged glass eels were exposed to small (19.1–24.4 cm) and large (31.9–43.5 cm) sea bass (Dicentrarchus labrax) during a 2 h trial. In 48% of the trials, successful predation was present and 13% showed clear predation attempts in which bass did not capture glass eels. No significant difference was found in predation rate between tagged and untagged glass eels and between red and blue tagged glass eels. Large sea bass predated more, but all sizes consumed glass eel under laboratory conditions. Stomach content analysis showed intact glass eel bodies 4–6 h after ending the 2 h trial and parts of glass eel bodies up to 16–18 h. This study showed that tagging does not increase predation in mark‐recapture studies using VIE‐tags in transparent glass eel. It also shows that the proportion of predation in relation to local glass eel abundance can be estimated if stomach content analysis is conducted within 4–6 h after predation.

Prey and stage preference of Acanthaspis pedestris Stål (Hemiptera : Reduviidae) on pests of cotton (Gossypium hirsutum)

In India, agriculture is currently suffering an annual loss of about rupees 8.5 million due to insect pests. As chemical control is having many side effects and after effect, biological control is the best alternative to protect the crop from pest insects. Among the predator's assassin bug is one of the promising biocontrol agents. Therefore, a study was conducted to evaluate the efficacy of the A. pedestris, prey and stage preference on two lepidopteran cotton pests, Helicoverpa armigera Hubner and Spodoptera litura Fabricius. The assessment of a predator's ability to capture and consume the relevant stadia of the targeted insect pest enables one to effectively utilize a natural enemy for biocontrol in the agricultural ecosystem. Steady increase in prey consumption was recorded by means of the progression of the developmental stages of the predator. The adult female consumed more than the adult male. The consumption of predators was observed to be decreased with the advancement of prey stages. The First and 2nd instar A.pedestris were limited in their ability to capture large-sized prey in both the prey species. The predator's success in pest control depends on its willingness to eat the target prey. Cotton leaf worm S. litura was the preferred prey among the two prey species.

Carnosaurs as Apex Scavengers: Agent-based simulations reveal possible vulture analogues in late Jurassic Dinosaurs

The Morrison Formation of the Late Jurassic Period is characterized by its diverse assemblage of sauropods, several species of which reached the size of modern cetaceans. While much scientific attention has concerned their biology in life, researchers have yet to examine how their massive carcasses may have influenced the evolution of other dinosaurs in their communities, such as theropods. Theropod consumers local to this faunal system are typically described as powerful apex predators at the top of local food webs, but instead, may have been shaped by competition for carrion resources generated as a byproduct of their giant sauropod neighbors. To test this hypothesis, we wrote a series of agent-based simulations (ABS). Specifically, we simulated allosaurid consumer behavior versus spatially distributed sauropod carcass resources such as could be expected in ecosystems like that represented in the Morrison Formation. We incorporated conditions to test how competition among consumers, seasonality, and predation success influenced carnosaur survival both with and without carrion-abundant systems. Trials of the ABS resulted in a strong selective advantage for allosaurs as obligate scavengers because of the high metabolic and survival costs associated with predation of large vertebrates. Allosaurs with increased predatory success over peers failed to succeed competitively unless the probability of scavenging opportunities fell below a certain threshold and a significant proportion of herbivores were available as prey targets, which might not have been the case in sauropod-dominated systems. Our results may explain why carnosaurs like Allosaurus did not evolve powerful bite forces, binocular vision, or advanced cursorial adaptations. Given the enormous supply of sauropod carrion, they were under no resource-based selective pressure to overpower prey and may have evolved as terrestrial vulture analogues. This also may explain why the absence of sauropods in certain environments led to more obvious predatory adaptations in theropods such as tyrannosaurs. Tyrannosaurs may have been forced to meet their energy budgets by hunting, because non-sauropod carrion production was too low to support them passively.

Shell-breaking predation on gastropods by Badister pictus (Coleoptera, Carabidae) with strikingly asymmetric mandibles.

The adults and larvae of some groups in the coleopteran family Carabidae are known to prey on snails (Mollusca: Gastropoda). Most species of the carabid tribe Licinini are believed to feed on live snails. However, the snail-eating behavior of only a few species has been studied. Whether adults of the licinine genus Badister can prey on live snails was tested by providing 155 live snails of 20 species (eleven terrestrial and nine aquatic species) to adults of Badister pictus Bates, 1873, and observing their behavior under laboratory conditions. Six of the 20 snail species have an operculum that can close the aperture of the shell. Each B. pictus adult attacked all of the snails provided. Badister pictus successfully preyed on ten terrestrial and six aquatic snail species. These beetles used their strikingly asymmetrical mandibles to break the dextral shells along the dorsal part of the whorls from the outer lip of the aperture towards the apex, allowing subsequent consumption of the soft bodies. However, 41.9% of snails could not be eaten by B. pictus adults. The rate of predation success by B. pictus decreased with increasing shell size and thickness of snails. In addition, the presence of an operculum decreased the rate of predation success by B. pictus. The results show that the shell size, thickness, and operculum of some snail species could play important roles in preventing B. pictus mandibles from breaking the shells. Therefore, Badister beetles may exert selective pressure on the evolution of defensive shell structures in small-sized snails.

Effect of macroarthropods on Drosophila suzukii peri‐oviposition events: an experimental screening

AbstractSpotted wing drosophila, Drosophila suzukii (Matsumura) (Diptera: Drosophilidae), is an invasive pest which causes important damage to fruit crops, in particular in strawberry and cherry fields in Europe and North America. So far, its interaction with local fauna remains poorly studied, whereas it could give insight in the possibilities of biological control by using local predators. Indeed, no sustainable means of controlling populations of this fruit fly have been found, and alternative methods of pest management are needed. Here we compared the efficiency of 16 selected macroarthropods present in strawberry and cherry fields and farm structures from northern France. Most of them have never been tested against D. suzukii for their ability to disrupt its egg‐laying behavior and/or to prey upon it under experimental conditions. A set of 17 morphological and behavioral traits potentially associated with the predation success of macroarthropods was measured. We counted nearly 16 000 eggs laid by female D. suzukii on artificial substrate in 1 008 experimental arenas. We observed an egg difference ranging from +65 to –98% in the presence of an arthropod, compared to control arenas (without arthropods), with an overall mean decrease of 44%. Some macroarthropod predatory species, mostly spiders (from the families Agelenidae, Salticidae, and Lycosidae) and the centipede Lithobius forficatus (L.), were efficient at killing the flies before they could lay eggs. Other species, such as the carabids Limodromus assimilis (Pontoppidan) and Poecilus cupreus (L.), or the woodlouse Porcellio scaber (Latreille), reduced egg‐laying despite a lower predation rate. The macroarthopods’ traits mainly involved in predation and disruption of oviposition were the size of their body and their mobility. Our results add novel information about the acceptability of D. suzukii as prey for common macroarthropods of the local fauna. This experimental approach provides a first pre‐selection of promising macroarthropods that could be interesting in the control of D. suzukii populations.

Kinematics of prey capture and histological development of related organs in juvenile seahorse

The seahorse is a typical suction feeder with an elongated, tubular snout and a small terminal mouth. It is important to determine the details of this unique prey-capture behavior to improve the survival rate during seahorse breeding, especially for juveniles. In this study, we described the sucking process and characterized the kinematics in juvenile lined seahorse (Hippocampus erectus) at different ages (1–30 days after parturition; DAP) using a high-speed video system, and also investigated the histological basis of the feeding-related organs, including snout, eye, and intestine. The sucking of juvenile seahorses can be divided into four steps: searching, locating, capturing, and swallowing. Seahorses capture prey mainly based on the vision system, and histological results revealed a developed visual acuity in the newborn seahorses, so that they were able to prey once after releasing from the male seahorse's brood pouch. The attack distance, maximum snout width, capture success rate, and daily food intake of juvenile seahorses increased with maturation. A remarkable inflection point, in the snout expansion rate, successful predation rate, and growth rate, occurs at about 10 DAP, when calcification of the snout bones was completed. In addition, the intestines of newborn seahorses were short and quite simple, but developed rapidly during the first 20 DAP. These findings provide a better understanding of prey capture kinematics and nutritional physiology, and will be beneficial for improving the feeding strategies for juveniles during large seahorse breeding.

Comparison of Multipiscivore Foraging Success on Native and Invasive Prey Fish under Variable Light Intensities

AbstractPiscivorous fishes attack and consume a variety of prey; however, few studies have examined interactions of multiple predators with multiple prey species. The situational complexity of foraging at different times of day was explored by examining the interactions of paired native predators (Burbot Lota lota or Smallmouth Bass Micropterus dolomieu) with either native (Mottled Sculpin Cottus bairdii) or invasive (Round Goby Neogobius melanostomus) benthic prey. The study allowed the comparison of a pursuit predator (Smallmouth Bass) and an ambush predator (Burbot). Trials were performed under natural relevant lighting conditions with downwelling light intensity and emission spectrum matched to the irradiance at a 10‐m depth in the St. Louis River estuary during the summer at night, civil twilight, sunrise, and midmorning. Smallmouth Bass were more active and initiated 1,510 reactions that resulted in the successful capture of 61 Round Goby and 103 Mottled Sculpin, whereas Burbot initiated 475 reactions resulting in 24 successful retentions, including 9 Round Goby and 15 Mottled Sculpin. The percentage of successful retentions was greater for Smallmouth Bass (10.9%) than for Burbot (5%). Reaction probabilities to each prey differed significantly, which resulted in a two‐fold increase in attacks on Mottled Sculpin compared with Round Goby within the same time period. Reaction distances for both predators did not differ regarding prey species, but Smallmouth Bass reacted from farther away than did Burbot (maximum reaction distances of 159 and 98 cm, respectively). Greater success of native predators on native prey has likely caused higher mortality on native prey populations due to greater predator success, while capturing invasive prey decreases the net energy intake.

Natural enemies of herbivores maintain their biological control potential under short-term exposure to future CO2, temperature, and precipitation patterns.

Climate change will profoundly alter the physiology and ecology of plants, insect herbivores, and their natural enemies, resulting in strong effects on multitrophic interactions. Yet, manipulative studies that investigate the direct combined impacts of changes in CO2, temperature, and precipitation on the third trophic level remain rare. Here, we assessed how exposure to elevated CO2, increased temperature, and decreased precipitation directly affect the performance and predation success of species from four major groups of herbivore natural enemies: an entomopathogenic nematode, a wolf spider, a ladybug, and a parasitoid wasp. A four‐day exposure to future climatic conditions (RCP 8.5), entailing a 28% decrease in precipitation, a 3.4°C raise in temperature, and a 400 ppm increase in CO2 levels, slightly reduced the survival of entomopathogenic nematodes, but had no effect on the survival of other species. Predation success was not negatively affected in any of the tested species, but it was even increased for wolf spiders and entomopathogenic nematodes. Factorial manipulation of climate variables revealed a positive effect of reduced soil moisture on nematode infectivity, but not of increased temperature or elevated CO2. These results suggest that natural enemies of herbivores may be well adapted to short‐term changes in climatic conditions. These findings provide mechanistic insights that will inform future efforts to disentangle the complex interplay of biotic and abiotic factors that drive climate‐dependent changes in multitrophic interaction networks.

Virtual Reality Camera Technology Facilitates Sampling of Interactions Between Reef Piscivores and Prey

AbstractPredation is an important process influencing the structure of fish communities. There are multiple approaches used to quantify predatory interactions, and all approaches are beneficial but have their limitations. For example, food habit studies only represent results of successful predation events, direct observations by divers are time limited by both depth and temperature as well as observer effects, acoustic approaches cannot directly identify species, and video has field-of-view constraints when using standard cameras. While no approach is without constraints, the recent availability of small off-the-shelf virtual reality (VR) video cameras that can be used in marine environments offers a more spatially comprehensive field-of-view for conducting studies of community composition and species interactions both on the seafloor and in the overlying water column. Here, we demonstrate an approach for collection and analysis of data from stationary VR video to quantify predator-prey interactions at subtropical reefs in Gray’s Reef National Marine Sanctuary (NW Atlantic). This approach does not substitute for other widely used census and behavioral research approaches but augments those with unique analytical products and interpretation.

Bottom‐up effect of eradications: The unintended consequences for top‐order predators when eradicating invasive prey

Abstract The eradication of invasive species from islands yields significant conservation returns. However, novel challenges continue to arise as projects expand in their scope, complexity and scale. Prey‐loss and secondary poisoning were historically considered to have limited impact on native top‐order predators when planning eradications, but this has rarely been tested quantitatively. We used a 10‐year timeseries of Brown Skua Stercorarius antarcticus lonnbergi breeding surveys and isotopic dietary analysis on Macquarie Island to investigate how prey‐loss and secondary poisoning deaths resulting from the eradication of an abundant invasive prey species, European rabbits Oryctolagus cuniculus, affected a top‐order predator. Skua nest density declined from 7.14 nests/km2 (95% CI: 6.01–8.27) in the presence of rabbits (pre‐eradication) to 3.73 nests/km2 (95% CI: 2.96–4.51) in the first 3 years after the eradication of rabbits, before showing signs of recovery in the 4 years thereafter. However, breeding success dropped from 1.01 chicks/nest (95% CI: 0.76–1.26) to as low as 0.38 chicks/nest (95% CI: 0.23–0.53) with little evidence of recovery. Secondary poisoning affected a greater number of skuas than anticipated prior to the eradication, including skuas nesting in areas where rabbits were not typically hunted as prey. We highlight that invasive prey often replace native prey in the diet of native predators rather than provide an additional source of food, and rapid eradication of non‐native prey can have long‐term impacts for predators, particularly when recovery of native prey is slow. Synthesis and applications. Monitoring programmes that complement large‐scale eradication projects and address (a) trophic‐driven declines in predator populations and (b) population‐level impacts of secondary poisoning are integral to ensuring bottom‐up effects of eradications are anticipated and adequately quantified. If prey deficits caused by eradication of invasive prey are expected to be severe but short‐lived, supplementary feeding programmes may buffer against increased predation pressure on native prey and reduced breeding success of native predators. Alternatively, if the rapid recovery of native prey is not expected to occur naturally, breeding programmes and translocation of native prey prior to assist recovery of native predators should be considered to support ecosystem restoration.