Caudal distraction by rat snakes (Colubridae, Elaphe ): a novel behavior used when capturing mammalian prey

Caudal movement in snakes may serve either a predatory (e.g., caudal luring) or defensive (eg., rattling, aposematism) function. I describe a new behavioral pattern of tail movement in snakes. Gray rat snakes ( Elaphe obsoleta spiloides ) foraging on small mammals ( Mus domesticus ) moved their tails in an erratic, whiplike fashion after detecting their prey in the vicinity. The thrashing movement in the horizontal plane was audibly and visually obvious, resulting in displacement of leaf litter around the tail. All subjects displayed the behavior, but not in all foraging episodes. Shorter durations of caudal distraction resulted in greater predator success during the 1st attempt at prey capture. Caudal distraction may facilitate prey capture by gray rat snakes by direction the attention of prey away from the approaching head of the snake.     

Regional and seasonal diet of the Western Burrowing Owl in south central Nevada

We examined diets of Western Burrowing Owls ( Athene cunicularia hypugaea ) based on contents of pellets and large prey remains collected year-round at burrows in each of the 3 regions in south central Nevada (Mojave Desert, Great Basin Desert, and Transition region). The most common prey items, based on percent frequency of occurrence, were crickets and grasshoppers, beetles, rodents, sun spiders, and scorpions. The most common vertebrate prey was kangaroo rats ( Dipodomys spp.). True bugs (Hemiptera), scorpions, and western harvest mice ( Reithrodontomys megalotis ) occurred most frequently in pellets from the Great Basin Desert region. Kangaroo rats ( Dipodomys spp.) and pocket mice (Perognathinae) were the most important vertebrate prey items in the Transition and Mojave Desert regions, respectively. Frequency of occurrence of any invertebrate prey was high (>80%) in samples year-round but dropped in winter samples, with scorpions and sun spiders exhibiting the steepest declines. Frequency of occurrence of any vertebrate prey peaked in spring samples, was intermediate for winter and summer samples, and was lowest in fall samples. With the possible exception of selecting for western harvest mice in the Great Basin Desert region, Western Burrowing Owls in our study appeared to be opportunistic foragers with a generalist feeding strategy.     

Reptiles as principal prey? Adaptations for durophagy and prey selection by jaguar (Panthera onca)

We examined the evidence supporting the hypothesis that jaguars (Panthera onca) have morphological and behavioural adaptations to facilitate reptile predation. Jaguars’ head and bite features show adaptations to durophagy (consumption of hard-integumented prey) that are very unusual within the genus Panthera. These include: thick canines, well-developed head muscles and a fatal bite directed to braincase or nape. These characteristics have been previously considered an adaptation for the consumption of reptilian prey, whose thick integument poses a challenge to predation. Although causation of any trait as result of natural selection is hard to demonstrate with ecological evidence, its consequences can be suggested and predictions made. Here, through a review of the literature on jaguar predatory habits, we tallied the evidence for saurophagy against environmental characteristics correlated with jaguar predation on reptiles. We offer a new explanation for the presence of those traits, based on the selection patterns, prey abundances and main predation habits over the geographic range of the jaguar. We believe that these features allow jaguars to overcome dangerous and/or armoured prey by dispatching them rapidly through a bite to the head or nape. Reptile consumption is restricted to areas of high reptile abundance while dangerous or armoured prey is consistently preyed upon throughout the jaguar’s distribution, and selected even when their abundance is low. This questions the validity of the saurophagy hypothesis. We believe that these results are relevant to jaguar conservation and management, because some of the main prey species are severely threatened over their range, and because threatened reptiles are also consumed as prey.     

Diet and feeding behaviour of the Neotropical parrot snake (Leptophis ahaetulla) in northern Brazil

Specimens (289) of Leptophis ahaetulla from northern Brazil and western Maranhão were examined for the composition of stomach contents. Most prey items were tree frogs, especially those of the family Hylidae (90%). Most of the anurans identified belong to the Scinax ruber species group (27%) and Scinax sp. (25%). Prey size was significantly related to snake length but not to head length. There was no significant difference related to sex in either case. Both sexes preyed on small to medium‐sized items (3–10% of snake snout–vent length). Leptophis ahaetulla seems to manipulate captured prey before ingestion since most of the prey items (83.6%) were swallowed head‐first. Leptophis ahaetulla is primarily diurnal and semi‐arboreal, inhabits disturbed and undisturbed forest, and forages primarily on the ground and in fallen vegetation, where its prey items are likely to be found at rest.     

Studies on the predatory biology of Oriental dacetine ants (Hymenoptera: Formicidae) II. Novel prey specialization in Pyramica benten

The predatory biology of the ant Pyramica benten, a short‐mandibulate form in the tribe Dacetini, Myrmicinae, was studied in the field and laboratory. Pyramica benten prefers disturbed habitats, where they hunt predominantly collembolans of Entomobryidae. Laboratory observation and experiments revealed that this ant hunted such entomobryids more efficiently than collembolans of Tomocelidae and Isotomidae. The hunting behaviour of the ants is characterized by their grabbing the prey near the mouthparts and ambushing without approaching the prey. Success in this stealthy hunting is most probably enhanced by luring the prey with body smearing using organic material. Strumigenys are closely related to Pyramica but they are long‐mandibulate forms. Both genera are speciose and specialized predators on Collembola. Coleoptera is another group that has evolved specialized predators on Collembola so these dacetines and the coleopterans are compared for their hunting tactics and species diversity.     

Effects of turbidity on feeding rates of Lahontan cutthroat trout ( Oncorhynchus clarki henshawi ) and Lahontan redside shiner ( Richardsonius egregius )

The spawning of Lahontan cutthroat trout ( Oncorhynchus clarki henshawi ) in Summit Lake, Nevada, has reportedly declined since the early 1970s, coincident with the appearance of Lahontan redside shiner ( Richardsonius egregius ) in the lake. We investigated the relative predatory abilities of the 2 fish species foraging on live Daphnia magna in turbidity conditions commonly observed in Summit Lake. Experiments were performed under controlled light and temperature condition. In separate trials we fed trout and shiner 1 of 3 size classes of D. magna (1.7 mm, 2.2 mm, and 3.0 mm) at 6 levels of turbidity ranging from 3.5 to 25 NTU. Feeding rates for both species varied inversely with turbidity for all prey sizes. Feeding rates of shiner were greater than trout at all turbidity levels. In low turbidity (5 TNU), shiner consumed approximately 3% more prey during 2-h feeding trials. However, at high turbidity levels, the difference in feeding rates between species was proportionally higher (10%). At high turbidity levels (≥ 20 NTU) trout predation rates were relative insensitive to prey size. However, shiner continued to consume more, larger prey at the highest turbidity levels. These results indicate that Lahontan redside shiner may be superior to Lahontan cutthroat trout as zooplankton predators at high turbidity levels, and may explain the recent success of shiner in Summit Lake.     

Disentangling prey-handling efficiency of larval newts through multivariate prey trait analysis

Multivariate prey trait analysis is a functional approach to understand predator–prey relationships. In the present study, six prey macroinvertebrate ecological traits were used to identify several key factors in the handling efficiency of seven predatory larval newt species. The results revealed a remarkable similarity in the feeding behaviour among species, suggesting a foraging behaviour convergence among species in the prey-handling efficiency of larval newts. Nevertheless, larvae of some newt species showed clear preferences for particular categories of ecological trait; for example, Lissotriton vulgaris tended to feed on macroinvertebrate taxa with random trajectory, and Calotriton asper fed on macroinvertebrate taxa with high agility. In contrast, Mesotriton alpestris showed a clear ability to feed on prey with movable accessories (cases/tubes) and patterned concealment. This study shows how multivariate approaches can complement traditional diet analyses, and the method has wide applicability across life-stages and species.     

Stinger utilization and predation in the scorpion Paruroctonus boreus

The utilization of the stinger and the predatory technique of the scorpion, Paruroctonus boreus, was studied under laboratory conditions. During the study, 83 feedings were observed. Age of the scorpions and the percentage of prey stung by them were used to classify the scorpions into groups. The scorpions aged 13–61 days always stung prey. After 62 days the scorpions began to selectively utilize the stinger. Utilization declined until it reached 30 percent in the adult stage. The stinger is apparently necessary for prey capture only in the early life stages.       

Large mixed-species dispersal flights for predatory and scavenging aquatic Heteroptera and Coleoptera, northern Arizona, USA

We report 4 incidents of large (hundreds to hundreds of thousands of individuals) mixed-species flights of predatory and scavenging aquatic Heteroptera and Coleoptera. The events occurred on normal (mostly clear, calm) autumn 2005 and spring 2006 late afternoons near Flagstaff, Arizona. Flight days were either near the full moon or in advanced waning lunar periods. At least 18 species were involved in the flights, with as many as 16 species (7 species of Heteroptera in 3 families, 9 species of Coleoptera in 2 families) in a single flight. Heteroptera (especially from the family Corixidae) were 2–4 orders of magnitude more numerous than Coleoptera. The diasporas plummeted, with much direct mortality, onto green metal roofs, and the largest event lasted more than 2 hours. Even after 2 days, uninjured individuals failed to resume their flights. The literature suggests that such flights occur for autumn movement to winter habitats or for location of springtime habitats for reproduction. The relative proportions of species in flocks were similar neither to the relative proportions in the region nor to those in nearby livestock watering tanks, indicating that the flights consisted of nonrandom assemblages of species. These events are rare or unique observations of coordinated movement of mixed predatory and scavenging invertebrate species.     

Predatory behaviour in Deltochilum: convergent evolution or a primitive character within a clade?

We present data on predatory behaviour in Deltochilum cupreicolle viridescens, which belongs to the subgenus Aganhyboma, and we contrast it with the behaviour of a species from the subgenus Deltohyboma. By this comparison we can investigate whether the predatory behaviour in Deltochilum could have appeared independently in these two subgenera, or if the behaviour is so similar that it suggests a single origin in a possible ancestor exclusive to those two groups. These laboratory studies on the behaviour of Deltochilum c. viridescens individuals on diplopods are described and divided into the following stages: (1) approach and recognition of the diplopod; (2) attack and death of the prey; (3) on-site feeding; (4) transport of the diplopod. The results found here strengthen the hypothesis of a primitive and highly specialized behaviour within a possible clade formed by the predatory species of Diplopoda.     

Diet of pine martens Martes martes L. in west Scotland

Diet of pine martens in a coastal Atlantic oakwood in western Scotland was assessed over a period of two years (1996-8) in the context of strong potential competition from a diverse guild of other predators also largely dependent on preferred small rodent prey. Analysis of prey remains in fresh droppings showed that despite the potential for competition, martens still preyed extensively on small mammals and birds, preying preferentially on voles and particularly Microtus agrestis L. Invertebrates were also important dietary items, with high intake of beetles (and particularly Geotrupes sp.) from March to September. Predation on birds and intake of earthworms were highest over the winter period; fruits (bramble and rowan berries) were also important over the autumn and (ivy berries) late winter. The diet described is similar to that recorded in other studies, with no significant shifts due to potential competition from other predatory birds and mammals on the same species-poor prey base. However, marten activity in the area was subject to sudden seasonal decline in both sign and sightings and it seems possible that the animals may be making gross range shifts in periods of relative scarcity of high quality foods, moving substantial distances to track local availability of preferred prey.     

Diet composition of an invasive population of Lithobates catesbeianus (American Bullfrog) from Argentina

The American bullfrog Lithobates catesbeianus has been introduced around the world, with invasive populations reported from almost all South American countries. A population of this species was introduced in the Calingasta department of San Juan province, which is an arid environment in western Argentina. This work provides information on the dietary composition of an invasive population of L. catesbeianus, and compares the degree of dietary overlap between adults and juveniles. Stomach contents of 169 bullfrogs (82 adults and 87 juveniles) were analysed. Adults consumed 40 prey taxa and Hymenoptera (Insecta) was the most numerous prey item (41.8%), followed by Araneae (13.6%) and Aeglidae (13.4%). Juveniles consumed 29 prey taxa and Hymenoptera constituted the highest percentage in prey number (77.2%). The trophic overlap niche index at the same level shows a value of 0.64 overlap in dietary community between adults and juveniles of this bullfrog. Aeglidae was volumetrically the most important trophic item (25.4%), followed by Anura (25.02%). Our results showed that cannibalism in bullfrogs is more common than the consumption of native anurans, coinciding with that reported in other populations of introduced bullfrogs. The high similarity in the diets of both size classes and the association between the size of the predator and prey suggest that the impact caused by bullfrogs throughout their ontogeny is high and probably has an impact on their prey. Freshwater crabs are the main items in the diet of Lithobates catesbeianus in other introduced populations and are usually the most conspicuous at our study site. The crabs in freshwater ecosystems are part of the lowest trophic level in the food chain. The major threats to the southern region’s freshwater crabs include deforestation, farming and exotic species. Lithobates catesbeianus has a generalist diet and high overlap between adults and juveniles.     

The evolution of prey‐wrapping behaviour in spiders

We traced the evolution of silk use by spiders in attacks on prey by combining previous publications with new observations of 31 species in 16 families. Two new prey‐wrapping techniques are described. One, in which the spider holds a tense line (often covered with viscid silk) with both legs IV and applies it to the prey with a simultaneous movement of both legs, may be a synapomorphy linking Theridiidae, Nesticidae, and Synotaxidae. The other, in which the spider stands over the prey and turns in place, is apparently very ancient; it occurs in Theraphosidae, Tengellidae, and Agelenidae. The use of legs IV to wrap prey is described for the first time in Filistatidae and Scytodidae. Using a recent phylogeny of spiders, we propose that prey wrapping with legs IV has evolved convergently at least four times. We propose that prey wrapping originally evolved from egg‐sac construction behaviour.     

Patterns of coral damage associated with the 2004 Indian Ocean tsunami at Mu Ko Similan Marine National Park,Thailand

On 26 December 2004, a severe earthquake in Sumatra caused a series of tsunami waves to strike southwestern coastal areas of Thailand. In this study, we investigated the patterns of tsunami‐related damage to coral reefs at Mu Ko Similan Marine National Park. The results showed that the percent of damaged corals ranged from 7.2% to 39.7% of the total live coral cover, and the intensity of the coral damage was high at depths deeper than 10 metres at most study sites. In addition, massive and tabulate coral forms were the most susceptible to tsunami damage. The surveys also revealed that a high degree of coral damage occurred where the reef slope gradually dropped away from the shoreline. Therefore, coral communities and coastal profiles can be major factors influencing the movement of the currents generated by the tsunami and consequently may affect the pattern of coral damage by the tsunami.     

Antipredator defence mechanism in the amphidromous shrimp Xiphocaris elongata (Decapoda: Xiphocarididae): rostrum length

Predators may affect prey through inducible defences that can alter prey phenotype. The shrimp Xiphocaris elongata exhibits a short rostrum (SR) in the absence of fish predators and a long rostrum (LR) in their presence. The long rostrum in X. elongata is inducible by the predatory fish Agonostomus monticola (mountain mullet). Our objective was to test whether the long rostrum is an effective antipredator defence against A. monticola in different stages of predator–prey interactions (i.e. choice, attacks, bites, rejections, handling time and survival). We conducted behavioural experiments in fish tanks in which we fed A. monticola simultaneously with (1) one LR shrimp and one SR shrimp, or (2) one LR shrimp and one shrimp which originally had a long rostrum but whose rostrum was cut (LR[S]). We scored the fish behaviours in terms of choice, unsuccessful attacks, bites, rejections and handling time. We also conducted mortality experiments in closed artificial pools in which we exposed (1) 10 LR and 10 SR shrimp or (2) 10 LR and 10 LR[S] shrimp to A. monticola, and quantified shrimp survival after 24 h. In the trials with LR and SR shrimp, A. monticola tended to attack SR shrimp first. LR shrimp were unsuccessfully attacked, bitten and rejected more than SR individuals. Handling time was higher for LR shrimp. The mortality experiments show higher survival of LR shrimp. In the trials with LR and LR[S] shrimp, A. monticola tended to attack LR[S] shrimp first. Unsuccessful attacks were similar for LR and LR[S]. There were more bites and rejections and longer handling time for LR shrimp. Survival was similar for LR and LR[S] shrimp in the mortality experiments. This study provides evidence in support of the hypothesis that the long rostrum in X. elongata is an effective antipredator defence against A. monticola by conferring benefits in most stages of the predator–prey interactions.     

Predation on invasive land gastropods by a Neotropical land planarian

Studies on the predatory behaviour of land planarians have focused mainly on established invasive species, while the feeding habits of non-invasive planarians are poorly understood. We analyse the predatory behaviour of Obama ladislavii, a land planarian native to southern Brazil that is common in both natural and human-disturbed areas. Observations were performed in the laboratory. Several groups of invertebrates were offered as possible prey and interactions between these invertebrates and planarians were recorded. Obama ladislavii fed on the introduced land gastropods Bradybaena similaris, Helix aspersa and Deroceras laeve, ignoring other invertebrates. Once potential prey were identified, we tested the ability of O. ladislavii to recognize and follow slime trails, and demonstrated the planarian’s ability to follow chemical trails from prey in the environment. The consumption of exotic species indicates a flexible, generalist diet that is consistent with the ability of O. ladislavii to adapt to environments altered by human activities. Thus, this species may become invasive if introduced outside of its original distribution, but it also has the potential to be used in biological control programs for pest management in its native range.     

Ectoparasitism and phoresy in Thysanoptera: the case of Aulacothrips dictyotus (Heterothripidae) in the Neotropical savanna

Thrips are cosmopolitan and abundant insects with great diversity in the Neotropics, but taxonomic and crop pest aspects comprise almost all of our knowledge of these insects. Here we describe a unique case of an ectoparasite species, Aulacothrips dictyotus Hood (Heterothripidae), which infests and also uses as dispersal vector (phoresy behaviour) the hemipteran Enchenopa brasiliensis (Membracidae). Thrips fix themselves on the ventral region of their hosts, at the junction of thorax and abdomen. Phoresy takes place when the attached thrips are transported to other plants and/or host aggregations. Phoresy is a useful long range dispersal mechanism for this weakly flying thrip species. Out of the 6000 species of thrips described, most are phytophagous and fungivorous, and only A. dictyotus performs ectoparasitism and phoretic behaviour.     

Diverse mechanisms of feeding and movement in Cyclorrhaphan larvae (Diptera)

Direct observation, filmed behaviour and morphological analysis were used to investigate mechanisms of larval feeding and movement in 20 species of Cyclorrhapha (Diptera). Feeding mechanisms refer to techniques of gathering food close to the pharynx entrance prior to sucking it in. A total of 12 mechanisms were recorded. Contrasting mechanisms were associated with saprophagy, phytophagy, mycophagy and zoophagy. Larvae had role-specific, compartmentalised bodies. The rear compartment grips substrates enabling the front ones to scan for food by sweeping from side to side or up and down. The front compartments extend or lunge to gather food or grip substrates during locomotion. Lower cyclorrhaphans had more disparate mechanisms than higher cyclorrhaphans. In the latter, the size, shape and movements of the thorax, pseudocephalon and head skeleton are diverse. Influences on this diversity are food quality and access conditions at development sites. Movement capabilities and functions were established for many components.     

Biology and life history of the araneophagic assassin bug Stenolemus bituberus including a morphometric analysis of the instars (Heteroptera,Reduviidae)

Stenolemus bituberus is an araneophagic “assassin bug” (Heteroptera; Reduviidae; Emesinae) that typically is found living in spider webs. We documented the life history of S. bituberus in the field for 13 months, determining its developmental phenology and microhabitat characteristics as well as describing its mating and predatory behaviour. We also included a morphometric analysis of the instars. Our study revealed that S. bituberus is univoltine with five juvenile instars. Although S. bituberus is found in the webs of spiders from a wide range of genera, it is found most commonly in the webs of Achaearanea, Badumna, Pholcus, and Stiphidion. Multiple juveniles often were found on a single web, but adults tended to be more solitary. Stenolemus bituberus appears to have two distinct hunting strategies: “stalking”, in which they slowly approach the spider, make contact and then strike; and “luring”, in which they attract the spider within range by manipulating the silk with their legs.     

Two heads are better than one: false head allows Calycopis cecrops (Lycaenidae) to escape predation by a Jumping Spider,Phidippus pulcherrimus (Salticidae)

The deflection of attack from vital organs to the wing margin is regarded as an important adaptation in hairstreak butterflies. However, this “lose-little-to-save-much” strategy akin to the detachable lizard's tail had never been tested experimentally. The present study tests the “false head” hypothesis by exposing a hairstreak butterfly, Calycopis cecrops, as well as many other Lepidoptera species as controls, to the attacks of the jumping spider, Phidippus pulcherrimus. The results unambiguously indicate that the “false head” is a very efficient strategy in deflecting attacks from the vital centres of the hairstreak butterfly whereas other similar-sized Lepidoptera fall easy prey. Predator fatigue resulting from unsuccessful attacks was also observed, suggesting that jumping spiders can learn to avoid attacking prey they cannot capture, which would increase the efficiency of the “false head” as a defensive mechanism.