Ambush Strategy Research Articles

Ambush strategy enhances organisms’ performance in rock–paper–scissors games

We study a five-species cyclic system wherein individuals of one species strategically adapt their movements to enhance their performance in the spatial rock–paper–scissors game. Environmental cues enable the awareness of the presence of organisms targeted for elimination in the cyclic game. If the local density of target organisms is sufficiently high, individuals move towards concentrated areas for direct attack; otherwise, they employ an ambush tactic, maximising the chances of success by targeting regions likely to be dominated by opponents. Running stochastic simulations, we discover that the ambush strategy enhances the likelihood of individual success compared to direct attacks alone, leading to uneven spatial patterns characterised by spiral waves. We compute the autocorrelation function and measure how the ambush tactic unbalances the organisms’ spatial organisation by calculating the characteristic length scale of typical spatial domains of each species. We demonstrate that the threshold for local species density influences the ambush strategy’s effectiveness, while the neighbourhood perception range significantly impacts decision-making accuracy. The outcomes show that long-range perception improves performance by over 60%, although there is potential interference in decision-making under high attack triggers. Understanding how organisms’ adaptation their environment enhances their performance may be helpful not only for ecologists, but also for data scientists, aiming to improve artificial intelligence systems.

Evidence that wolves use cooperative ambush strategies to hunt beavers

Cooperative hunting can confer fitness benefits by increasing foraging efficiency. We documented a breeding pair of wolves in the Greater Voyageurs Ecosystem of Minnesota, USA that appeared to periodically use cooperative ambushing to hunt beavers. The breeding pair primarily chose to wait-in-ambush close to one another (< 65 m) but on different beaver feeding trails, which appears advantageous because: (1) feeding trails are where beavers are most active and vulnerable on land, (2) the probability that the pair encounters a beaver is increased, and (3) either wolf can quickly assist the other in killing a beaver. The cooperative ambush strategy these wolves used appears rare for most social Carnivora but we hypothesize this behavior is widespread in areas of wolf-beaver sympatry. This observation demonstrates that novel insights into the natural history of even well-studied predators are possible when technological advancements are combined with intensive fieldwork.

A nocturnally-active predator is mainly a diurnal hunter

The sit-and-wait hunter, Cerastes vipera, is a presumed nocturnally-active desert snake, although it feeds mainly on the diurnally-active lizard, Acanthodactylus spp. We hypothesized that nocturnal activity of C. vipera is primarily to locate an ambush site, and that Acanthodactylus spp. is predated mainly diurnally. We used the proportion of free-ranging C. vipera that defaecated per day to estimate daily feeding rate, and prey capture per night to estimate nocturnal feeding rate. In adult snakes (n = 161), defaecation was observed in 20.5% and nocturnal feeding in 3.1% per day. The difference between the two estimates represented the diurnal feeding rate, that is, 85% of the daily feeding was diurnal. All vipers ceased movement near midnight, when approximately 50% were in ambush. They maintained their position until morning and four individuals of each sex were followed during the day. These vipers displayed caudal luring in the presence of Acanthodactylus spp., ended ambush at approximately 10:00 when air temperature reached 40 °C, and then moved into a nearby burrow. We concluded that nocturnally-active C. vipera adults are mainly diurnal hunters, but could be classified as cathemeral predators. Diurnal caudal luring and differences in ambush strategy in C. vipera are documented for the first time.

Ambush Marketing Via Social Media: The Case of the Three Most Recent Olympic Games

This study explored the practices and strategies of ambush marketing via social media (SM) during the 2014 Sochi, 2016 Rio, and 2018 PyeongChang Olympic Games. An observational netnography method was adopted to investigate direct industry competitors’ (of the Olympic sponsors) use of SM for the purpose of ambush marketing during the 2014, 2016, and 2018 Games. Data were gathered from the official Twitter accounts of 15 direct industry competitors over the three most recent Games. Despite a series of SM guidelines released by IOC for the 2014, 2016, and 2018 Games, the findings showed that the practice of ambush marketing via SM was evident during each of the Games. Direct industry competitors were found employing four specific ambush strategies, namely, associative, values, coattail, and property infringement. Theoretical and practical implications, as well as an impetus for future research, are suggested.

Wolves choose ambushing locations to counter and capitalize on the sensory abilities of their prey

Abstract Comprehensive knowledge of ambush behavior requires an understanding of where a predator expects prey to be, which is generally unknowable because ambush predators often hunt mobile prey that exhibit complex, irregular, or inconspicuous movements. Wolves (Canis lupus) are primarily cursorial predators, but they use ambush strategies to hunt beavers (Castor canadensis). Terrestrial beaver activity is predictable because beavers use well-defined, conspicuous habitat features repeatedly. Thus, studying where wolves wait-in-ambush for beavers provides a unique opportunity to understand how predators choose ambush locations in relation to prey activity. We searched 11 817 clusters of GPS locations from wolves in the Greater Voyageurs Ecosystem, International Falls, MN, and documented 748 ambushing sites and 214 instances where wolves killed beavers. Wolves chose ambush locations: 1) with olfactory concealment to avoid detection from the highly developed olfactory senses of beavers and 2) close (generally &amp;lt;5 m) to beaver habitat features to take advantage of beavers’ inability to visually detect motionless predators. Our work describes in detail the ambush strategies wolves use to hunt beavers and continues to overturn the traditional notion that wolves rely solely on cursorial hunting strategies. We also demonstrate that ambush predators can anticipate the movements and behavior of their prey due to a fundamental understanding of their prey’s sensory abilities. Wolves, therefore, and likely ambush predators in general, appear capable of simultaneously accounting for abiotic and biotic factors when choosing ambush locations, ultimately allowing them to counter and capitalize on the sensory abilities of their prey.

APOBEC and Cancer Viroimmunotherapy: Thinking the Unthinkable.

The apolipoprotein B mRNA editing enzyme catalytic polypeptide (APOBEC) family protects against infection by degrading incoming viral genomes through cytosine deamination. Here, we review how the potential to unleash these potent DNA mutagens comes at a price as APOBEC DNA mutagenesis can contribute to development of multiple types of cancer. In addition, because viral infection induces its expression, APOBEC is seen as the enemy of oncolytic virotherapy through mutation of the viral genome and by generating virotherapy-resistant tumors. Therefore, overall APOBEC in cancer has received very poor press. However, we also speculate how there may be silver linings to the storm clouds (kataegis) associated with APOBEC activity. Thus, although mutagenic genomic chaos promotes emergence of ever more aggressive subclones, it also provides significant opportunity for cytotoxic and immune therapies. In particular, the superpower of cancer immunotherapy derives in part from mutation, wherein generation of tumor neoantigens-neoantigenesis-exposes tumor cells to functional T-cell repertoires, and susceptibility to immune checkpoint blockade. Moreover, APOBECs may be able to induce suprathreshold levels of cellular mutation leading to mitotic catastrophe and direct tumor cell killing. Finally, we discuss the possibility that linking predictable APOBEC-induced mutation with escape from specific frontline therapies could identify mutated molecules/pathways that can be targeted with small molecules and/or immunotherapies in a Trap and Ambush strategy. Together, these considerations lead to the counterintuitive hypothesis that, instead of attempting to expunge and excoriate APOBEC activity in cancer therapy, it might be exploited-and even, counterintuitively, encouraged.

Out of the burrow and into the nest: Functional anatomy of three life history stages of Ozaena lemoulti (Coleoptera: Carabidae) reveals an obligate life with ants.

The carabid subfamily Paussinae contains many species known to be obligately associated with ants during at least one stage of their life history. Myrmecophilous larvae have been documented for members of the tribe Paussini as well as several genera in the tribes Ozaenini, including Physea and Eustra. Here we describe the first instar larva of Ozaena lemoulti, and find it to be the most highly modified ozaenine larva that we have examined to date. Many structures of the larva suggest that it is a myrmecophile. Unlike all other described ozaenine larvae, which live in burrows that they construct and seal with their terminal disk, the completely unique larval morphology suggests Ozaena has adapted to living without the protection of a burrow and therefore must have a completely different feeding strategy than the typical ambush strategy of burrow dwelling larvae. We hypothesize that Ozaena larvae live in association with ants and use their long legs for running within the nest, and modifications of the mouthparts suggest the larva feeds on soft lightly sclerotized prey, such as ant brood. Our findings support an earlier hypothesis that Ozaena is mymecophilous during the adult stage. Comparisons of the functional anatomy of the eggs, larvae and adult between Ozaena lemoulti and the closely related, non-myrmecophilous general arthropod predator, Goniotropis kuntzeni, provide complementary, yet independent, evidence suggestive of this shift in lifestyle. We also examine and molecularly identify gut contents, providing direct evidence that adult Ozaena exclusively eat Camponotus ants. We conclude that Ozaena represents an independent shift to adopting a life of myrmecophily among beetles classified within the carabid subfamily Paussinae and document the morphological changes at each life history stage associated with the shift to a nest parasite lifestyle.

Merging cranial histology and 3D-computational biomechanics: a review of the feeding ecology of a Late Triassic temnospondyl amphibian.

Finite Element Analysis (FEA) is a useful method for understanding form and function. However, modelling of fossil taxa invariably involves assumptions as a result of preservation-induced loss of information in the fossil record. To test the validity of predictions from FEA, given such assumptions, these results could be compared to independent lines of evidence for cranial mechanics. In the present study a new concept of using bone microstructure to predict stress distribution in the skull during feeding is put forward and a correlation between bone microstructure and results of computational biomechanics (FEA) is carried out. The bony framework is a product of biological optimisation; bone structure is created to meet local mechanical conditions. To test how well results from FEA correlate to cranial mechanics predicted from bone structure, the well-known temnospondyl Metoposaurus krasiejowensis was used as a model. A crucial issue to Temnospondyli is their feeding mode: did they suction feed or employ direct biting, or both? Metoposaurids have previously been characterised either as active hunters or passive bottom dwellers. In order to test the correlation between results from FEA and bone microstructure, two skulls of Metoposaurus were used, one modelled under FE analyses, while for the second one 17 dermal bone microstructure were analysed. Thus, for the first time, results predicting cranial mechanical behaviour using both methods are merged to understand the feeding strategy of Metoposaurus. Metoposaurus appears to have been an aquatic animal that exhibited a generalist feeding behaviour. This taxon may have used two foraging techniques in hunting; mainly bilateral biting and, to a lesser extent, lateral strikes. However, bone microstructure suggests that lateral biting was more frequent than suggested by Finite Element Analysis (FEA). One of the potential factors that determined its mode of life may have been water levels. During optimum water conditions, metoposaurids may have been more active ambush predators that were capable of lateral strikes of the head. The dry season required a less active mode of life when bilateral biting is particularly efficient. This, combined with their characteristically anteriorly positioned orbits, was optimal for ambush strategy. This ability to use alternative modes of food acquisition, independent of environmental conditions, might hold the key in explaining the very common occurrence of metoposaurids during the Late Triassic.

Feeding biomechanics of Late Triassic metoposaurids (Amphibia: Temnospondyli): a 3D finite element analysis approach.

The Late Triassic freshwater ecosystems were occupied by different tetrapod groups including large-sized anamniotes, such as metoposaurids. Most members of this group of temnospondyls acquired gigantic sizes (up to 5 m long) with a nearly worldwide distribution. The paleoecology of metoposaurids is controversial; they have been historically considered passive, bottom-dwelling animals, waiting for prey on the bottom of rivers and lakes, or they have been suggested to be active mid-water feeders. The present study aims to expand upon the paleoecological interpretations of these animals using 3D finite element analyses (FEA). Skulls from two taxa, Metoposaurus krasiejowensis, a gigantic taxon from Europe, and Apachesaurus gregorii, a non-gigantic taxon from North America, were analyzed under different biomechanical scenarios. Both 3D models of the skulls were scaled to allow comparisons between them and reveal that the general stress distribution pattern found in both taxa is clearly similar in all scenarios. In light of our results, both previous hypotheses about the paleoecology of these animals can be partly merged: metoposaurids probably were ambush and active predators, but not the top predators of these aquatic environments. The FEA results demonstrate that they were particularly efficient at bilateral biting, and together with their characteristically anteropositioned orbits, optimal for an ambush strategy. Nonetheless, the results also show that these animals were capable of lateral strikes of the head, suggesting active hunting of prey. Regarding the important skull size differences between the taxa analyzed, our results suggest that the size reduction in the North American taxon could be related to drastic environmental changes or the increase of competitors. The size reduction might have helped them expand into new ecological niches, but they likely remained fully aquatic, as are all other metoposaurids.

Habitat choice and hunting behaviour of the alligator pipefish, Syngnathoides biaculeatus, in captivity

The alligator pipefish, Syngnathoides biaculeatus, is a cryptic species commonly found in seagrass meadows. The fish is shy and slow, and it is unknown how the predaceous fish hunts its mobile prey. This study determined its feeding behaviour in an artificial setting of open and vegetated area in an aquarium. Fish behaviour was observed and studied during the early feeding and post-feeding event. The behaviour of 14 pipefish was individually recorded for a duration of 10 min each for each event, and recorded events were replayed and scored using an event recorder. Fish behaviour and duration were scored following an ethogram based on categories of habitat preference (vegetated/open), body orientation (horizontal/vertical), grasping behaviour (using prehensile tail) and hunting approach (horizontal front/vertical front/horizontal rear/vertical rear). Results showed a greater habitat preference for the vegetated area compared to the open area for both sexes. The pipefish also displayed side rolls resembling the moving blade of seagrass in its natural habitat. There was no orientation preference in either sex, nor between early feeding and post-feeding stages. Non-grasping behaviour was favoured after introduction into the tank and during early feeding by both sexes, while the grasping behaviour was favoured during post-feeding. The pipefish adopted a target-locking strategy while mimicking the seagrass movement as it approached its prey. The ambush strategy was adopted while waiting for its prey to approach it within striking distance. Each pipefish showed four hunting approaches, but there was no concordance on the preferred hunting approach among them. The feeding behaviour of the alligator pipefish incorporating stealth and camouflage appears to show an obligatory dependence on seagrass meadows for its survival.

Repellent activities of dichloromethane extract of Allium sativum (garlic) (Liliaceae) against Hyalomma rufipes (Acari).

Dichloromethane (DCM) extract of garlic (Allium sativum Linn.) bulbs was assessed for its repellent effect against the hard tick, Hyalomma rufipes (Acari: Ixodidae) using two tick behavioural bioassays; Type A and Type B repellency bioassays, under laboratory conditions. These bioassays exploit the questing behaviour of H. rufipes, a tick that in nature displays ambush strategy, seeking its host by climbing up on vegetation and attaching to a passing host. One hundred microlitres (100 µL) of the test solution containing DCM extract of garlic bulbs and DCM at concentrations of 0.35%, 0.7% or 1.4% w/v were evaluated. DCM only was used for control. Tick repellency increased significantly (R2 = 0.98) with increasing concentration (40.03% – 86.96%) yielding an EC50 of 0.45% w/v in Type B repellency bioassay. At concentration of 1.4% w/v, the DCM extract of garlic bulbs produced high repellency index of 87% (male ticks) and 87.5% (female ticks) in the Type A repellency bioassay. Only 4% avoidance of male ticks or female ticks was recorded in the Type B repellency bioassay. In the corresponding controls, the mean numbers of non-repelled male or female ticks were 80% and 41 males or 38 females of 50 ticks in the Type A and Type B repellency bioassays, respectively. The variations in the results could be attributed to the difference in tick repellent behaviours that were assessed by the two repellency bioassays; the Type A repellency bioassay assessed repellent effect of garlic extracts without discriminating between deterrence and avoidance whereas the Type B repellency bioassay only assessed avoidance response. Generally, DCM extract of garlic was repellent against H. rufipes, albeit weak tick repellency was obtained in the Type B repellency bioassay. Furthermore, this study established that the tick repellent activity of garlic extracts is predominantly by deterrence.

Waiting with bated breath: opportunistic orientation to human odor in the malaria mosquito, Anopheles gambiae, is modulated by minute changes in carbon dioxide concentration.

Females of the malaria mosquito, Anopheles gambiae, predominantly obtain blood meals within human dwellings. Being highly anthropophilic, human skin odor offers a reliable, host-specific cue, but the challenge posed by pervasive human odor found indoors from used clothing, bedding etc. remains unclear. Anopheles gambiae spends much of its adult life indoors, constantly exposed to human odor even when dwellings are unoccupied. In landing assays, we found that female mosquitoes respond very weakly to human skin odor alone, suggesting that, alone, it is an ineffective landing cue. Landing, however, was dramatically increased by addition of carbon dioxide at a range of concentrations above ambient. Indeed, this effect was seen even when carbon dioxide was just 0.015% above ambient within the assay cage. The synergistic effect of added carbon dioxide quickly waned, thereby facilitating a highly adaptive "sit-and-wait" ambush strategy, wherein females ignore persistent human odor until a living human is present. Unexpectedly, landing rates in the presence of added carbon dioxide were almost as robust during daytime, when An. gambiae has previously been assumed inactive, possibly facilitating opportunistic feeding at times of day when human dwellings are occupied intermittently. We suggest earlier studies that showed strong upwind flight behavior toward human odor alone could, in fact, have been demonstrating orientation toward a human dwelling rather than toward a living human. This new interpretation of how human odors mediate upwind orientation and landing in An. gambiae is discussed.

Ambush and Active Search in Multistage Predator–Prey Interactions

In this paper, we study a multistage search game. The general situation is described as a predator---prey problem as follows: in a certain region there is a predator and a group of prey. The prey have h different places to go to eat, and every day the group goes to one of these places, but all the days, the herd is forced to go to a certain place, W, say to drink. Simultaneously, the predator has to select a strategy to meet the herd of prey and catch one of them, it can use its ambush strategy, which consists of going to place W, and wait there for the herd, or select a search strategy and go to one of the h different places where the herd goes to eat and search for a prey there. When predator and prey meet each other in one place, predator can catch a prey with a probability depending on the place and on the movement of the predators. Since animals require a minimum consumption of energy over time to survive, we suppose that the predator has to catch a minimum number of prey, K, over a number of days, M. We model this problem as a two-person zero-sum multistage game, which we solve in some situations by giving optimal strategies for prey and for predator and the value of the game.

Weapons of mass intrusion: the leveraging of ambush marketing strategies

Purpose – The study presented in this article aims to examine the impact of the leveraging of three distinct ambush marketing strategies that are under-researched in the literature: Promotion, Event, and Broadcast. Design/methodology/approach – An experiment was conducted where the type of ambush strategy was manipulated (i.e. Promotion, Event, Broadcast, no ambush) as well as the market dominance of the sponsor (i.e. dominant or non-dominant) and the congruence level between the event and the sponsor (i.e. high or low congruence). Findings – Ambush strategies' impacts differ widely. The Broadcast strategy is the most harmful to the identification of the actual sponsor; the Event strategy favors the identification of the pseudo-sponsor as the sponsor, while the Promotion strategy is both harmful to the actual sponsor and beneficial for the pseudo-sponsor. Furthermore, although dominant brands benefit more from their sponsorships, they are more affected by an ambush than non-dominant brands. Research limitations/implications – Only one sponsor and one pseudo-sponsor were considered at a time. In addition, digital media were not investigated as vectors of ambush marketing. Further research where multiple sponsors and pseudo-sponsors are leveraging their associations to an event, using both off and on-line media, needs to be undertaken. Practical implications – Against the Promotion strategy sponsors need to create not only strong but also unique associations with the event. The Event strategy can be circumvented with preemptive smaller scale events. Exclusive access to the program broadcast for event sponsors can protect against pseudo-sponsors. Originality/value – This study is the first to provide empirical evidence regarding the impact of the Promotion, Event, and Broadcast strategies. Previous studies had focused almost exclusively on another strategy: the airing of commercials by pseudo-sponsors during event broadcast against which most sponsors are now effectively protected.

Comparison of the Ontogeny of Hunting Behavior in Pharaoh Cuttlefish (Sepia pharaonis) and Oval Squid (Sepioteuthis lessoniana)

Animals adopt various forms of hunting according to their ecological, morphological, and cognitive features, and their specific hunting skills are acquired ontogenetically in relation to these features. It is noted that cuttlefish and squid hunt prey through the elongation of tentacles used specifically to capture prey. However, these two cephalopods have different lifestyles, leading to questions such as whether hunting skill is acquired similarly after birth and whether tentacle elongation is behaviorally identical. To address these questions, we observed and compared how captive pharaoh cuttlefish (Sepia pharaonis) and oval squid (Sepioteuthis lessoniana) attack prey during their early life stages. Like the adults, S. pharaonis hatchlings used the tentacular lunge attack, whereas S. lessoniana hatchlings used the arm-opening attack. S. lessoniana began to exhibit the tentacular strike attack after 30 days of age. In addition to timing of the emergence of a specific hunting mode, some differences were observed in the physical aspect of hunting behavior. For cuttlefish, maximum tentacle length and maximum speed of tentacle elongation increased from hatching to 30 days of age and then decreased. In contrast, for squid, maximum tentacle length increased from hatching to 30 days of age and then became constant. The distance to prey was positively correlated with maximum length and speed of tentacle elongation in S. pharaonis and with maximum swimming speed in S. lessoniana. These results show that cuttlefish mainly use an ambush strategy and that squid use a pursuit strategy. Possible causes for the ontogenetic differences in hunting behavior are discussed.

Thoughts about hunting: Some things we know and some things we don't know

This paper explores a number of underappreciated “complexities” in the interpretation of the taxonomic composition, sex ratios, and mortality profiles of archaeological faunal assemblages. Some of these complexities arise from the behavior of the animals themselves. For example, when hunters “disturb” animals such as bison in order to maneuver them toward a trap or ambush, the animals rearrange themselves spatially by age and sex in such a way that the subset of animals actually killed may not be a random sample of the living population. Other complexities arise from the fact that some animals are obligate drinkers, while others are not, making the former much more vulnerable to ambush. Hence, for hunters who rely heavily on an ambush strategy, the taxonomic composition of the kill assemblage will be biased toward obligate drinkers regardless of their actual numbers on the landscape. There are also a host of cultural factors that may affect what gets hunted, when hunting takes place, and the way these events are conducted. For example, hunts may occur primarily for prestige, as part of boys' puberty and initiation rites, as payment of bride price or bride service, in the context of establishing alliances or restoring peaceful relations between competing groups, as part of community-wide calendrical or episodic rituals, and for many other socially-grounded reasons. Most of these cultural factors are not easily approached using models drawn from behavioral ecology and, as a consequence, remain understudied by zooarchaeologists.

Foraging strategy switching in an antlion larva

Antlion larvae are typically considered as trap-building predators, but some species of antlions always forage without using pits or only sometimes use pits to capture prey; they can ambush prey without pits. This study examined a species that switches its strategy between pit-trapping and ambushing and asked the mechanism behind the switching behaviour. A dynamic optimization model incorporating tradeoffs between the two strategies was built. The tradeoffs were prey capture success and predation risk (both are higher when pit-trapping). The model predicted that antlions should use the trap-building strategy when their energy status is low and should use the ambush strategy when their energy status is high. These predictions as well as an assumption (i.e., predation risk associated with pit-trapping is higher than that associated with ambushing) of the model were empirically confirmed. The results suggest that antlions flexibly switch between pit-trapping and ambushing to maximize their fitness by balancing the costs and benefits of the two strategies.

Chemosensory responses to chemical and visual stimuli in five species of colubrid snakes

Snakes utilize chemical and visual stimuli during predation, however the emphasis on these cues and which cues are used to initiate predation varies among species. For example, rattlesnakes using the ambush strategy rely on chemical cues to locate an ambush station, then visual and thermal cues to initiate envenomating strikes, then chemical cues again to track prey. By contrast, many natricine snakes use chemical cues to initiate predation, increasing the rate of tongue flicking regardless of whether visual cues are present. The present study examined the individual and interactive effects of chemical and visual stimuli of prey on the predatory behavior of five snake taxa representing three feeding guilds. Bull snakes ( Pituophis catenifer ), Eastern Corn snakes ( Pantherophis guttatus ), and Midland Rat snakes ( Scotophis spiloides ) have a diet primarily consisting of mammals; Western Fox snakes ( Mintonius vulpina ) prey primarily on bird eggs; and Common Kingsnakes ( Lampropeltis getula ) prey equally on mammals and reptiles. Three patterns of response to chemical and visual stimuli of the test prey ( Mus musculus ) were observed. Mammal specialists responded to chemical cues. Fox snakes responded to visual cues, but not to chemical cues. Kingsnakes exhibited increased rates of tongue flicking in response to both chemical and visual stimuli. This study suggests correlations between the evolution of prey preference, foraging ecology and the utilization of chemical or visual stimuli by snakes.

Effects of zebra mussel attachment on the foraging behaviour of a larval dragonfly, Macromia illinoiensis

1. Larvae of Macromia illinoiensis Walsh are often colonised by the zebra mussel, Dreissena polymorpha Pallas, a recent invader to North America. To determine how mussel attachment affects an individual's foraging behaviour, we quantified capture of Hexagenia limbata Hexes mayfly prey and the distance moved by newly-molted final instars before and after an individual's colonisation with zebra mussels. 2. In night trials, larvae sprawled above the sand, and caught more mayflies than individuals in daytime trials, but the estimated distance travelled did not differ. When resting under a layer of sand with only its eyes exposed during the day, an individual could capture a mayfly prey using a sit-and-wait ambush strategy. When sprawled above the sand, some larvae caught prey that rested on their legs. 3. When mussel-free, individuals captured more prey than they did when carrying zebra mussels, although mussel attachment per se did not affect the estimated distance that a larva moved. 4. During day trials, but not night ones, the increasing mussel load of colonised individuals decreased prey capture and the distance moved in an apparent step-wise function. Although the number of mussels carried did not differ, night foragers carried a heavier load. Independent of time of the day, the distance an individual travelled when mussel-free was predictive of the number of prey it caught when colonised, suggesting that the greater general activity of some individuals helped mitigate negative effects that mussel attachment had on prey capture. 5. Our results add to a growing number of negative effects of zebra mussel colonisation on sprawling and hiding dragonfly larvae. Although the impact of these costs on dragonfly populations remains to be determined, a decrease in this guild of predators whose life cycle spans aquatic and terrestrial habitats might have cascading effects across ecosystems.

Arboreal Ants Use the “Velcro® Principle” to Capture Very Large Prey

Plant-ants live in a mutualistic association with host plants known as “myrmecophytes” that provide them with a nesting place and sometimes with extra-floral nectar (EFN) and/or food bodies (FBs); the ants can also attend sap-sucking Hemiptera for their honeydew. In return, plant-ants, like most other arboreal ants, protect their host plants from defoliators. To satisfy their nitrogen requirements, however, some have optimized their ability to capture prey in the restricted environment represented by the crowns of trees by using elaborate hunting techniques. In this study, we investigated the predatory behavior of the ant Azteca andreae which is associated with the myrmecophyte Cecropia obtusa. We noted that up to 8350 ant workers per tree hide side-by-side beneath the leaf margins of their host plant with their mandibles open, waiting for insects to alight. The latter are immediately seized by their extremities, and then spread-eagled; nestmates are recruited to help stretch, carve up and transport prey. This group ambush hunting technique is particularly effective when the underside of the leaves is downy, as is the case for C. obtusa. In this case, the hook-shaped claws of the A. andreae workers and the velvet-like structure of the underside of the leaves combine to act like natural Velcro® that is reinforced by the group ambush strategy of the workers, allowing them to capture prey of up to 13,350 times the mean weight of a single worker.