Vertebrate Predators Research Articles

A comparative analysis of experimental selection on the stickleback pelvis.

Mechanisms of natural selection can be identified using experimental approaches. However, such experiments often yield nonsignificant effects and imprecise estimates of selection due to low power and small sample sizes. Combining results from multiple experimental studies might produce an aggregate estimate of selection that is more revealing than individual studies. For example, bony pelvic armour varies conspicuously among stickleback populations, and predation by vertebrate and insect predators has been hypothesized to be the main driver of this variation. Yet experimental selection studies testing these hypotheses frequently fail to find a significant effect. We experimentally manipulated length of threespine stickleback (Gasterosteus aculeatus) pelvic spines in a mesocosm experiment to test whether prickly sculpin (Cottus asper), an intraguild predator of stickleback, favours longer spines. The probability of survival was greater for stickleback with unclipped pelvic spines, but this effect was noisy and not significant. We used meta-analysis to combine the results of our mesocosm experiment with previously published experimental studies of selection on pelvic armour. We found evidence that fish predation indeed favours increased pelvic armour, with a moderate effect size. The same approach found little evidence that insect predation favours reduced pelvic armour. The causes of reduced pelvic armour in many stickleback populations remain uncertain.

Skeletal trauma reflects hunting behaviour in extinct sabre-tooth cats and dire wolves.

Skeletal-injury frequency and distribution are likely to reflect hunting behaviour in predatory vertebrates and might therefore differ between species with distinct hunting modes. Two Pleistocene predators from the Rancho La Brea asphalt seeps, the sabre-tooth cat, Smilodon fatalis, and dire wolf, Canis dirus, represent ambush and pursuit predators, respectively. On the basis of a collection of over 1,900 pathological elements, the frequency of traumatic injury across skeletal elements in these two species was calculated. Here we show that the frequency of trauma in the sabre-tooth cat exceeds that of the dire wolf (4.3% compared to 2.8%), implying that the killing behaviour of S. fatalis entailed greater risk of injury. The distribution of traumatic injuries also differed between the two species. S. fatalis, an ambush predator, was injured more often than expected across the lumbar vertebrae and shoulders whereas C. dirus, a pursuit predator, had higher than expected levels of injury in the limbs and cervical vertebrae. Spatial analysis was used to quantify differences in the distribution of putative hunting injuries. Analysis of injury locations discriminated true hotspots from injury-dense areas and facilitated interpretation of predatory behaviour, demonstrating the use of spatial analyses in the study of vertebrate behaviour and evolution. These results suggest that differences in trauma distribution reflect distinct hazards of each species' hunting mode.

Nonpreference ofCeratomia catalpae(Lepidoptera: Sphingidae) to Invertebrate Predators

Aposematic traits such as bright contrasting coloration and gregarious feeding are often signals to predators that a potential prey is unpalatable. Larvae of Ceratomia catalpae (Boisduval) (Lepidoptera: Sphingidae), the catalpa sphinx, show aposematic traits and sequester catalpol, a secondary compound from their host plant Catalpa spp. (Bignoniaceae). Catalpol sequestration by other caterpillar species has been shown to deter both invertebrate and vertebrate predators, but the palatability of C. catalpae has not been explicitly tested. Choice tests were performed with spiders (Hogna carolinensis Walckenaer, Araneae: Lycosidae) and predatory hemipterans (Podisus maculiventris [Say], Hemiptera: Pentatomidae). These tests showed that predators naive to both C. catalpae and the alternate prey Trichoplusia ni (Hubner) (Lepidoptera: Noctuidae) and Manduca sexta (L.) (Lepidoptera: Sphingidae) preferred the alternate species, and that P. maculiventris that were exposed previously to T. ni also preferred T. ni. In nonchoice tests, P. maculiventris grew significantly more slowly upon C. catalpae compared to M. sexta. These results suggest that C. catalpae, like other caterpillars that sequester catalpol, is less palatable to invertebrate predators compared to nonsequestering caterpillar species.

Effects of an invasive predator cascade to plants via mutualism disruption

Invasive vertebrate predators are directly responsible for the extinction or decline of many vertebrate species, but their indirect impacts often go unmeasured, potentially leading to an underestimation of their full impact. When invasives extirpate functionally important mutualists, dependent species are likely to be affected as well. Here, we show that the invasive brown treesnake, directly responsible for the extirpation of forest birds from the island of Guam, is also indirectly responsible for a severe decline in plant recruitment as a result of disrupting the fruit-frugivore mutualism. To assess the impact of frugivore loss on plants, we compare seed dispersal and recruitment of two fleshy-fruited tree species on Guam and three nearby islands with intact disperser communities. We conservatively estimate that the loss of frugivorous birds caused by the brown treesnake may have caused a 61–92% decline in seedling recruitment. This case study highlights the potential for predator invasions to cause indirect, pervasive and easily overlooked interaction cascades.

Predators, Parasites and Heterospecific Aggregations in Chrysomeline Larvae

AbstractGregariousness is a common feature in aposematic insect prey and offers the additional benefit of enhancing the effectiveness of their toxic defences. Aggregations of the aposematic larvae of two species of leaf beetles, Paropsis atomaria and Paropsisterna variicollis, occur together on the same Eucalyptus trees over spring and summer. Conventionally, the colouration of these larvae is thought to provide aposematic protection against vertebrate predators, but supporting evidence is limited. We determine whether environmental preferences contribute to the heterospecific aggregations, and the potential costs for larvae of living in heterospecific aggregations. We surveyed natural aggregations of the larvae of both species in the field and recorded environmental variables of these aggregations. This revealed that heterospecific aggregations occurred more commonly at higher leaf temperatures, and in less visually conspicuous locations. Paropsis atomaria larvae were twice as likely to be found in heterospecific aggregations than Pa. variicollis. Next, we manipulated larval aggregations in the field to investigate the survival and gregarious behaviour of larvae in heterospecific aggregations. The gregarious behaviour of both species of larvae did not differ between heterospecific and monospecific aggregations. Further, the survival of larvae did not significantly differ between heterospecific and monospecific aggregations. We suggest that the preference for P. atomaria larvae to aggregate with Pa. variicollis at higher leaf temperature results in the observed heterospecific aggregations, with a potential benefit of lowerer parasitoidism rates for P. atomaria.

The golden mimicry complex uses a wide spectrum of defence to deter a community of predators.

Mimicry complexes typically consist of multiple species that deter predators using similar anti-predatory signals. Mimics in these complexes are assumed to vary in their level of defence from highly defended through to moderately defended, or not defended at all. Here, we report a new multi-order mimicry complex that includes at least 140 different putative mimics from four arthropod orders including ants, wasps, bugs, tree hoppers and spiders. All members of this mimicry complex are characterised by a conspicuous golden body and an ant Gestalt, but vary substantially in their defensive traits. However, they were similarly effective at deterring predators - even mildly defended mimics were rarely eaten by a community of invertebrate and vertebrate predators both in the wild and during staged trials. We propose that despite the predominance of less defended mimics the three predatory guilds avoid the mimics because of the additive influence of the various defensive traits.

A review of the sentinel prey method as a way of quantifying invertebrate predation under field conditions.

Sentinel prey can provide a direct, quantitative measure of predation under field conditions. Live sentinel prey provides more realistic data but rarely allows the partitioning of the total predation pressure; artificial prey is less natural but traces left by different predators are identifiable, making it suitable for comparative studies. We reviewed the available evidence of the use of both types of invertebrate sentinel prey. Fifty-seven papers used real prey, usually measuring predation on a focal (often pest) species, with studies overwhelmingly from North America. The median predation was 25.8% d-1 . Artificial sentinel prey (45 papers) were used in both temperate and tropical areas, placed more above ground than at ground level. The most commonly used artificial prey imitated a caterpillar. Up to 14 predator groups were identified, registering a median of 8.8% d-1 predation; half the studies reported only bird predation. Predation on real prey was higher than on artificial ones, but invertebrate predation was not higher than vertebrate predation. Invertertebrate but not vertebrate predation was negatively related to prey size. Predation near the Equator was not higher than at higher latitudes, nor in cultivated than noncultivated habitats. The use of sentinel prey is not yet standardised in terms of prey size, arrangement, exposure period or data reporting. Due to the simplicity and ease of use of the method, such standardisation may increase the usefulness of comparative studies, contributing to the understanding of the importance and level of predation in various habitats worldwide.

The meat of the matter: an evolutionary perspective on human carnivory

ABSTRACTNatural selection, as both a process and a scientific concept, is eloquently simple. Unfortunately, this simplicity sometimes belies Darwin’s broader view of evolution as a multifaceted process that proceeds from both ecological pressures and phylogenetic history. Darwin further understood that it is not just physical traits that are transmitted generationally, but also behavioural patterns, both of which are subject to the shaping influences of environment and phylogeny. Chimpanzees, bonobos and humans are the most carnivorous extant primates, an observation that serves as the basis of our extended argument that vertebrate predation is a synapomorphy of these sister taxa. From there, we use archaeological data to trace the inferred polarity of hominin carcass foraging and meat-eating from their first archaeological indications ∼2.6 million years ago (Mya). A review of the early Pleistocene African record demonstrates that taphonomic evidence of a hominin predatory/meat-eating behavioral module clarifies ∼2.0 Mya, a critical time period characterised by traces of advanced carcass foraging, which, in turn, suggest that an earlier phase(s) of vertebrate capture by hominins was/were simpler. In rounding out this meta-analytical consideration of hominin carnivory, we draw on comparative primatology, ecology and archaeology in order to build a holistic model of this fundamental behavioural adaptation.

Too hard to swallow: a secret secondary defence of an aposematic insect.

Anti-predator strategies are significant components of adaptation in prey species. Aposematic prey are expected to possess effective defences that have evolved simultaneously with their warning colours. This study tested the hypothesis of the defensive function and ecological significance of the hard body in aposematic Pachyrhynchus weevils pioneered by Alfred Russel Wallace nearly 150 years ago. We used predation trials with Japalura tree lizards to assess the survivorship of 'hard' (mature) versus 'soft' (teneral) and 'clawed' (intact) versus 'clawless' (surgically removed) weevils. The ecological significance of the weevil's hard body was evaluated by assessing the hardness of the weevils, the local prey insects, and the bite forces of the lizard populations. The existence of toxins or deterrents in the weevil was examined by gas chromatography-mass spectrometry (GC-MS). All 'hard' weevils were instantly spat out after being bitten once and survived attacks by the lizards. In contrast, the 'soft' weevils were chewed and subsequently swallowed. The results were the same regardless of the presence or absence of the weevil's tarsal claws. The hardness of 'hard' Pachyrhynchus weevils was significantly higher than the average hardness of other prey insects in the same habitat and the mean bite forces of the local lizards. The four candidate compounds of the weevil identified by GC-MS had no known toxic or repellent functions against vertebrates. These results reveal that the hardness of aposematic prey functions as an effective secondary defence, and they provide a framework for understanding the spatio-temporal interactions between vertebrate predators and aposematic insect prey.

Determination of Trophic Structure in Selected Freshwater Ecosystems by using Stable Isotope Analysis.

Stable isotope analysis has been used extensively to establish trophic relationships in many ecosystems. Present study utilised stable isotope signatures of carbon and nitrogen to identify trophic structure of aquatic food web in river and rice field ecosystems in Perak, northern peninsular Malaysia. The mean δ13C values of all producers ranged from −35.29 ± 0.21 to −26.00 ± 0.050‰. The greatest δ15N values noted was in zenarchopterid fish with 9.68 ± 0.020‰. The δ15N values of aquatic insects ranged between 2.59 ± 0.107 in Elmidae (Coleoptera) and 8.11 ± 0.022‰ in Nepidae (Hemiptera). Correspondingly, with all the δ13C and δ15N values recorded, it can be deduced that there are four trophic levels existed in the freshwater ecosystems which started with the producer (plants), followed by primary consumer (aquatic insects and non-predatory fish), secondary consumer (invertebrate predators) and lastly tertiary consumer (vertebrate predators).

Variation in bird assemblages and their invertebrate prey in eucalypt formations across a rainfall gradient in south-west Australia

Our previous work has shown how invertebrate food resources influence usage of tree species by birds. Using data from Western Australian forests and woodlands, we extend the findings to indicate how the avifauna is influenced by these resources at the landscape level. The northern dry sclerophyll forest of south-west Australia comprises jarrah (Eucalyptus marginata) to the west, with an abrupt replacement by wandoo (E. wandoo) plus powderbark wandoo (E. accedens) woodland to the east; codominant marri (Corymbia calophylla) trees occur throughout. Knockdown samples have previously indicated that the canopy invertebrate fauna is richer and more abundant in wandoo woodland than in jarrah/marri forest. To provide an indication of their general abundance and diversity in these formations, invertebrates using the trunks of the ubiquitous marri were measured along a transect from jarrah/marri forest to wandoo woodland. Mirroring the canopy, the trunk fauna had high species turnover over short distances. As with the canopy fauna, invertebrate diversity and abundance was higher on marri situated in the wandoo zone than in the jarrah/marri areas, indicating a generally larger invertebrate fauna in the drier regions of the transect. Abundance and diversity of birds, many of which are wholly or partly insectivorous, were measured at the same sites. Birds were more abundant and there were more species in areas with the wandoo species than in those dominated by jarrah/marri. Assemblage composition also differed in the two forest types. It is evident that changes in bird abundance, richness, and assemblage composition are likely determined on a landscape scale by the type, abundance, and diversity of food resources available to them. These patterns of change within forest invertebrate faunas and their primary vertebrate predators need to be considered when making decisions on conserving or managing forest communities in Australia.

A hypothesis to explain accuracy of wasp resemblances.

Mimicry is one of the oldest concepts in biology, but it still presents many puzzles and continues to be widely debated. Simulation of wasps with a yellow‐black abdominal pattern by other insects (commonly called “wasp mimicry”) is traditionally considered a case of resemblance of unprofitable by profitable prey causing educated predators to avoid models and mimics to the advantage of both (Figure 1a). However, as wasps themselves are predators of insects, wasp mimicry can also be seen as a case of resemblance to one's own potential antagonist. We here propose an additional hypothesis to Batesian and Müllerian mimicry (both typically involving selection by learning vertebrate predators; cf. Table 1) that reflects another possible scenario for the evolution of multifold and in particular very accurate resemblances to wasps: an innate, visual inhibition of aggression among look‐alike wasps, based on their social organization and high abundance. We argue that wasp species resembling each other need not only be Müllerian mutualists and that other insects resembling wasps need not only be Batesian mimics, but an innate ability of wasps to recognize each other during hunting is the driver in the evolution of a distinct kind of masquerade, in which model, mimic, and selecting agent belong to one or several species (Figure 1b). Wasp mimics resemble wasps not (only) to be mistaken by educated predators but rather, or in addition, to escape attack from their wasp models. Within a given ecosystem, there will be selection pressures leading to masquerade driven by wasps and/or to mimicry driven by other predators that have to learn to avoid them. Different pressures by guilds of these two types of selective agents could explain the widely differing fidelity with respect to the models in assemblages of yellow jackets and yellow jacket look‐alikes.

Summer time predation on the obligatory off-host stage of an invasive ectoparasite.

Predation can regulate populations and strongly affect invasion success of novel prey. The deer ked (Lipoptena cervi; Linnaeus 1758) is an invasive ectoparasite of cervids that spends a long period of its life cycle outside the host. Prior to this study, virtually nothing was known about natural summer time predation on the deer ked. We aimed to evaluate the magnitude of summer time predation on L. cervi pupae in different habitats and to identify potential predators. We conducted a set of field experiments, where we exposed L. cervi pupae to various ground-dwelling vertebrate and invertebrate predators. The loss of pupae was monitored for different predator guilds. Three habitats of the moose, the main host species, were studied: (1) moist heath forest; (2) dry, logged heath forest; and (3) moist meadow. The results indicate notable summer time predation on L. cervi pupae, and the pupal predation varied within and between habitats, being lowest in the meadow habitat. We found a positive correlation between pupal loss and abundance of the common lizard (Zootoca vivipara), harvestmen (Opiliones), ground spiders (Gnaphosidae) and Formicinae-ants. We conclude that summer time predation during the pupal phase can have a notable local importance for the L. cervi abundance.

English

Large-scale coal mining practices, particularly surface coal extraction and associated valley fills as well as residential wastewater discharge, are of ecological concern for aquatic systems in central Appalachia. Identifying and quantifying alterations to ecosystems along a gradient of spatial scales is a necessary first-step to aid in mitigation of negative consequences to aquatic biota. In central Appalachian headwater streams, apart from fish, salamanders are the most abundant vertebrate predator that provide a significant intermediate trophic role linking aquatic and terrestrial food webs. Stream salamander species are considered to be sensitive to aquatic stressors and environmental alterations, as past research has shown linkages among microhabitat parameters, large-scale land use such as urbanization and logging, and salamander abundances. However, there is little information examining these relationships between environmental conditions and salamander occupancy in the coalfields of central Appalachia. In the summer of 2013, 70 sites (sampled two to three times each) in the southwest Virginia coalfields were visited to collect salamanders and quantify stream and riparian microhabitat parameters. Using an information-theoretic framework, effects of microhabitat and large-scale land use on stream salamander occupancy were compared. The findings indicate that Desmognathus spp. occupancy rates are more correlated to microhabitat parameters such as canopy cover than to large-scale land uses. However, Eurycea spp. occupancy rates had a strong association with large-scale land uses, particularly recent mining and forest cover within the watershed. These findings suggest that protection of riparian habitats is an important consideration for maintaining aquatic systems in central Appalachia. If this is not possible, restoration riparian areas should follow guidelines using quick-growing tree species that are native to Appalachian riparian areas. These types of trees would rapidly establish a canopy cover, stabilize the soil, and impede invasive plant species which would, in turn, provide high-quality refuges for stream salamanders. Key words: Canopy cover, coal mining, Desmognathus, Eurycea, headwater streams, surface mining.

Invasive fire ants contain high levels of mercury

Mercury contamination is a serious environmental concern usually associated with aquatic food webs. We tested for the presence of mercury in winged queens and males of four ant species and found that invasive red imported fire ants (Solenopsis invicta) contain high levels of mercury typical of aquatic insects. Mercury concentrations in male fire ants were 51 % higher than those in females and 89–199 % higher than those in other ant species from the same location. Fire ant sexuals fly long distances on their mating flights and are a major food source for arthropod and vertebrate predators and may thus transfer mercury through food webs.

Protein content of the Hylesia metabus egg nest setae (Cramer [1775]) (Lepidoptera: Saturniidae) and its association with the parental investment for the reproductive success and lepidopterism

Hylesia metabus is a neotropical moth possessing toxic setae, which once in contact with the skin cause a severe dermatitis to humans known as lepidopterism. The only known function of the setae in the life cycle is to provide protection during the mating and egg-hatching stages. Approximately 65% of the protein content of the setae is a cluster of five proteases (28–45kDa) showing sequence homology to other S1A serine proteases. The N-glycans of a 40kDa protease are a mixture of neutral and sulfated G0F structures. The sulfated N-glycans have an important role in triggering the inflammatory response typical of lepidopterism while the proteolytic activity may promote the erosion of blood vessels and tissues causing focal hemorrhages. The presence of Chitinase and a 30kDa lipoprotein is probably related to the antifungal defense. In addition, chitin digestion of the setae may potentiate the inflammatory reaction caused by the toxins due to the formation of chitin adjuvants fragments. The combined effect of proteases and a chitinase may dissuade predating arthropods, by damaging their exoskeletons. Vitellogenin, a bacteriostatic protein, is able to recognize pathogen-associated patterns, which suggests its possible role in protecting the embryonated eggs from pathogenic microorganisms. SignificanceThe present study is the first report describing the different protein species present in the urticating egg nest setae of the neotropical moth Hylesia metabus - the most harmful of the Hylesia moths - causing a severe urticating dermatitis in humans known as lepidopterism. A distinctive feature of the venom is the presence of five different S1A serine proteases probably used to guarantee a more efficient degradation of a wider number of protein substrates. This work confirms that the presence of sulfated N-glycans is not an isolated finding since its presence has been demonstrated in two different proteases affirming that this PTM is of importance for the activation of the inflammatory response typical of lepidopterism. Additionally, this study gives useful information on the defense mechanisms used for protection of its progeny vs. vertebrate predators, fungus, bacteria or other arthropods such as ants. The proteins detected in the egg nest should be seen as an extended parental effort made by the females in order to achieve an optimal reproductive success, thus compensating for the considerable loss of progeny during the larval stages that seriously limits the number of sexually mature adults reaching the reproductive phase.

Um evento incomum de predação de vertebrado por um lagarto insetívoro

The knowledge about Enyalius perditus Jackson, 1978 (Leiosauridae) indicates that the main food items are invertebrates. However, this communication is the first vertebrate predation report, the lizard Hemidactylus mabouia (Moureau De Jonnes, 1818) (Gekkonidae) in a remnant of Atlantic Forest in Ubatuba, state of Sao Paulo, Brazil. This record highlights the lack of knowledge concerning the natural history of E. perditus and adds information about types of prey as food source. Keywords: Atlantic Forest, diet, feeding habits, natural history, prey-predator relationships.

Motive for Killing: What Drives Prey Choice in Wild Predators?

AbstractCarnivorous animals are assumed to consume prey to optimise energy intake. Recently, however, studies using Nutritional Geometry (NG) have demonstrated that specific blends of macronutrients (e.g. protein, fat and in some cases carbohydrates), rather than energy per se, drive the food selection and intake of some vertebrate and invertebrate predators in the laboratory. A vital next step is to examine the role of nutrients in the foraging decisions of predators in the wild, but extending NG studies of carnivores from the laboratory to the field presents several challenges. Biologging technology offers a solution for collecting relevant data which when combined with NG will yield new insights into wild predator nutritional ecology.

Diversity of insulin-like peptide signaling system proteins in Calanus finmarchicus (Crustacea; Copepoda) – Possible contributors to seasonal pre-adult diapause

Calanus finmarchicus, an abundant calanoid copepod in the North Atlantic Ocean, is both a major grazer on phytoplankton and an important forage species for invertebrate and vertebrate predators. One component of the life history of C. finmarchicus is the overwintering dormancy of sub-adults, a feature key for the annual recruitment of this species in early spring. While little is known about the control of dormancy in C. finmarchicus, one hypothesis is that it is an insect-like diapause, where the endocrine system is a key regulator. One group of hormones implicated in the control of insect diapause is the insulin-like peptides (ILPs). Here, C. finmarchicus transcriptomic data were used to predict ILP signaling pathway proteins. Four ILP precursors were identified, each possessing a distinct A- and B-chain peptide; these peptides are predicted to form bioactive heterodimers via inter-chain disulfide bridging. Two ILP receptors, which likely represent splice variants of a common gene, were identified. Three insulin-degrading enzymes were also discovered, as were proteins encoding the transcription factor FOXO, a downstream target of ILP that has been implicated in the regulation of insect diapause, and insulin receptor substrate, a protein putatively linking the ILP receptor and FOXO. RNA-Seq data suggest that some C. finmarchicus insulin pathway transcripts are differentially expressed across development. As in insects, the ILP signaling system may be involved in controlling C. finmarchicus’ organism-environment interactions (e.g., regulation of seasonal sub-adult diapause), a hypothesis that can now be investigated using these data.

Behavioral responses to predation risk in brooding female amphipods (Gammarus pseudolimnaeus)

ABSTRACTPrevious research has shown that brooding female amphipods (Gammarus pseudolimnaeus) are more likely than other adults to be eaten by vertebrate and invertebrate predators under restrictive laboratory conditions. Here, we investigate how the mobility of amphipods that differ in sex or reproductive status varies. Second, we investigate whether any such differences in mobility are associated with differences in predator avoidance behaviors. Male amphipods collected from the field had 18% higher maximum velocity and 44% higher average velocity than females. Non-brooding females had 33% higher maximum velocity than brooding females, but their average velocities were not significantly different. The average velocity of brooding females was negatively correlated with brood size. Brooding females were significantly more likely to aggregate and to seek cover when predator cues were present, whereas the responses of males and non-brooding females were more variable, as predicted by the trait compensation hypothesis. Behavioral plasticity in predator response behavior likely provides a mechanism for brooding females to mitigate predation risk during the period in which their mobility is impaired. These intraspecific differences in predator response may have important implications for stream community ecology and fisheries management.