Predator Deterrence Research Articles

Caudal Spine Morphology and Puncture Performance of Two Coastal Stingrays

A diagnostic characteristic of stingrays in the family Dasyatidae is the presence of a defensive, partially serrated spine located on the tail. We assessed the contribution of caudal spine morphology on puncture and withdrawal performance from two congeneric, co-occurring stingrays, the Atlantic stingray, Hypanus sabinus, and the bluntnose stingray, Hypanus say. Spines exhibited a high degree of morphological variability. Stingray spines were serrated along 50.8% (H. sabinus) or 62.3% (H. say) of their length. Hypanus say had a greater number of serrations along each side of the spine (30.4) compared with H. sabinus (20.7) but the pitch did not differ between species. We quantified spine puncture and withdrawal forces using porcine skin as a model for human skin. Puncture and withdrawal forces did not differ significantly between species, or within H. say, but withdrawal force was greater than puncture force for H. sabinus. We incorporated micro-computed tomography scanning to quantify tissue mineral density and found that for both species, the shaft of the spine was more heavily mineralized than the base, and midway (50%) along the length of the spine was more heavily mineralized than the tip. The mineralization variability along the spine shaft may create a stiff structure that can fracture once embedded within the target tissue and act as an effective predator deterrent.

20-Hydroxyecdysone, from Plant Extracts to Clinical Use: Therapeutic Potential for the Treatment of Neuromuscular, Cardio-Metabolic and Respiratory Diseases.

There is growing interest in the pharmaceutical and medical applications of 20-hydroxyecdysone (20E), a polyhydroxylated steroid which naturally occurs in low but very significant amounts in invertebrates, where it has hormonal roles, and in certain plant species, where it is believed to contribute to the deterrence of invertebrate predators. Studies in vivo and in vitro have revealed beneficial effects in mammals: anabolic, hypolipidemic, anti-diabetic, anti-inflammatory, hepatoprotective, etc. The possible mode of action in mammals has been determined recently, with the main mechanism involving the activation of the Mas1 receptor, a key component of the renin–angiotensin system, which would explain many of the pleiotropic effects observed in the different animal models. Processes have been developed to produce large amounts of pharmaceutical grade 20E, and regulatory preclinical studies have assessed its lack of toxicity. The effects of 20E have been evaluated in early stage clinical trials in healthy volunteers and in patients for the treatment of neuromuscular, cardio-metabolic or respiratory diseases. The prospects and limitations of developing 20E as a drug are discussed, including the requirement for a better evaluation of its safety and pharmacological profile and for developing a production process compliant with pharmaceutical standards.

A Tail's Tale: Biomechanical Roles of Dorsal Thoracic Spine of Barnacle Nauplii.

Many marine invertebrates have complex life histories that begin with a planktonic larval stage. Similar to other plankton, these larval invertebrates often possess protruding body extensions, but their function beyond predator deterrence is not well-documented. For example, the planktonic nauplii of crustaceans have spines. Using the epibiotic pedunculate barnacle Octolasmis spp., we investigated how the dorsal thoracic spine affects swimming and fluid disturbance by comparing nauplii with their spines partially removed against those with intact spines. Our motion analysis showed that amputated Octolasmis spp. swam slower, in jerkier trajectories, and were less efficient per stroke cycle than those with intact spines. Amputees showed alterations in limb beat pattern: larger beat amplitude, increased phase lag, and reduced contralateral symmetry. These changes might partially help increase propulsive force generation and streamline the flow, but were insufficient to restore full function. Particle image velocimetry further showed that amputees had a larger relative area of influence, implying elevated risk by rheotactic predator. Body extensions and their interactions with limb motion play important biomechanical roles in shaping larval performance, which likely influences the evolution of form.

Female putty-nosed monkeys (Cercopithecus nictitans) vocally recruit males for predator defence.

Alarm calls can trigger very different behavioural changes in receivers and signallers might apply different alarm call strategies based on their individual cost-benefit ratio. These cost-benefit ratios can also vary as a function of sex. For instance, male but not female forest guenons possess loud alarms that serve warning and predator deterrence functions, but also intergroup spacing and male–male competition. In some forest guenons, the context specificity and alarm call repertoire size additionally differs between females and males but it remains unclear if this corresponds to similar sexual dimorphisms in alarm calling strategies. We here experimentally investigated whether general female and more context-specific male alarm calls in putty-nosed monkeys (Cercopithecus nictitans) had different effects on the opposite sex's behaviour and whether they might serve different female and male alarm calling strategies. We presented a leopard model separately to the females or to the male of several groups while ensuring that the opposite sex only heard alarm calls of target individuals. While female alarms led to the recruitment of males in the majority of cases, male alarms did not have a similar effect on female behaviour. Males further seem to vocally advertise their engagement in group defence with more unspecific alarms while approaching their group. Males switched alarm call types once they spotted the leopard model and started mobbing behaviour. Females only ceased to alarm call when males produced calls typically associated with anti-predator defence, but not when males produced unspecific alarm calls. Our results suggest that sexual dimorphisms in the context specificity of alarms most likely correspond to different alarm calling strategies in female and male putty-nosed monkeys.

Snake slough in birds’ nests acts as a nest predator deterrent

The use of snake slough as nest material by birds is considered an adaptive behavior to avoid nest predation. Here, we conducted predation experiments to test the hypothesis that the snake slough in nests of crested mynas (Acridotheres cristatellus) had anti-predatory effects. We put snake slough and white-rumped munia (Lonchura striata) eggs in the nest boxes to compare egg predation by Swinhoe’s striped squirrels (Tamiops swinhoei), one of the main predators of cavity-nesting birds. In addition, we conducted experiments to examine if Swinhoe’s striped squirrels identified the snake sloughs in the nest by vision or olfaction, and if the length of snake sloughs has effect on the predation rate. Our results showed that in the anti-predatory experiment, the egg predation rate (on days 3, 6) and the predation rate at which the squirrels first arrived the nest box were significantly lower in the experimental group than in the control group. In the olfaction experiment, there was no significant difference in both the predation rate (on days 1, 3, 6) and the predation rate at which the squirrels first arrived the nest box between the two groups. In the vision experiment, the predation rate at which the squirrels first arrived the nest box was significantly lower in the experimental group (hung snake slough) than in the control group (hung cotton strip). In the slough length experiment, the length of snake slough did not have a significant effect on the predation rate. These results suggest that the snake sloughs in bird nests can effectively deter nest predators, mainly via visual effect. Our study provided strong experimental evidence for the hypothesis that snake slough in birds’ nests acts as a nest predator deterrent.

Seed dispersal, directed deterrence and germination in gifboom (Hyaenanche globosa; Picrodendraceae) seeds

We investigated seed dispersal, directed deterrence and germination in the Cape narrow-endemic plant Hyaenanche globosa (gifboom). We found that gifboom seeds were predominantly removed and cached by the known scatter-hoarding specialist, small mammal, Acomys subspinosus, a first case of scatter-hoarding in the Picrodendraceae and the first case of a recalcitrant seed being scatter-hoarded in Cape fynbos. This represents an unusual exception to most hard-seeded, dormant scatter-hoarded seeds. In contrast, the ubiquitous, generalist, small mammal Micaelamys namaquensis, which is known to consume a variety of seeds, ignored gifboom seeds. The seeds, which contain the toxins, appear to have a directed deterrence effect on this common seed predator. We show that imbibed gifboom seeds produce copious mucilage, due to pectins, which aid in germination. Gifboom seeds appear to have two novel mechanisms for increasing seed to seedling survival, including toxins for seed predator deterrence and mucilage production for enhanced germination.

Ultimate causes of antipredator vocalizations in a nonhibernating squirrel

Communication plays an integral role in facilitating intra- and interspecific interactions. The study of signal function and content reveals the rules that govern such interactions, informing hypotheses in behavioural ecology and evolution. The ubiquitous nature of antipredator vocalizations in ground squirrels provides a useful model for studying the evolution of communication. Conspecifics in many ground squirrel species respond to antipredator vocalizations, and sociality functions as a strong selective force favouring more informative antipredator vocalizations. However, studies of a single antipredator vocalization system in both social and nonsocial contexts are relatively scarce, preventing diagnosis of selective forces other than sociality. We conducted a 2-year study to test two alternative hypotheses relating to the function of antipredator vocalizations in a nonhibernating squirrel, the Harris’ antelope squirrel, Ammospermophilus harrisii. We hypothesized that if vocalizations function as a predator deterrent, callers should be of equal sex ratio and vocalize year-round. If vocalizations function primarily as a warning to offspring, callers should be predominantly female and vocalize only when juveniles are above ground. We found that spontaneous callers were predominantly female but vocalized throughout the year. We also found that call bouts varied in trill number, which could hold additional layers of information. Our results suggest that antipredator vocalizations function as both a predator deterrent and a warning to offspring. Antipredator vocalizations with multiple functions or receivers are subject to a greater compilation of selective forces that may induce communicative complexity to arise.

Effectiveness of non-lethal predator deterrents to reduce livestock losses to leopard attacks within a multiple-use landscape of the Himalayan region.

Lethal measures are widely adopted by local communities and governments to manage human-wildlife conflicts. Such measures lead to large scale decline of carnivore populations globally with trophic cascades on ecosystems and questionable impacts on human-wildlife conflicts. Mitigating human-carnivore conflicts through non-lethal measures will protect endangered predators and secure livelihoods. However, information on the effectiveness of such measures are extremely limited and hence cannot be applied in developing scientific evidence. Further to develop human-carnivore coexistence models, it is important for local community members, biologists and wildlife managers to actively participate in conservation programs. We evaluated the response of a non-lethal visual deterrent (i.e. fox lights) to deter leopard attacks on livestock within a multiple-use landscape of western Himalaya through community engagement. We monitored 16 experimental sites and 17 control sites within 27 villages and recorded data on livestock depredation by leopards between April 2018 to April 2019. A multivariate analysis was conducted to determine the influence of landscape predictors and animal husbandry practices on livestock depredation by leopards within the vicinity of human settlements. We found that visual deterrents discouraged common leopards to predate on livestock (cows and goats). We also demonstrated that community based conservation initiatives are successful in mitigating human-carnivore conflicts within large semi-natural landscapes. We suggest developing site specific coexistence strategies and adopting non-lethal measures to safeguard carnivores, livestock and humans within shared landscapes.

Post‐embryonic development of Fritzolenellus suggests the ancestral morphology of the early developmental stages in Trilobita

AbstractTrilobite development has been intensively explored during the past decades, but information on ancestral character combinations in the early developmental stages of trilobites remains unknown. Trilobites of the superfamily Olenelloidea are one of the earliest diverging groups. Study of their development coupled with the development of other early diverging trilobite groups can provide information on the ancestral morphology of trilobite early stages. Herein we describe numerous well‐preserved specimens of the olenelloid trilobite Fritzolenellus lapworthi. The earliest stages have circular cephala bearing intergenal spines and lacking genal spines. During subsequent development, morphological changes involve the modification of the cephalic shape from circular to semicircular, expansion of the frontal glabellar lobe, gradual shortening of intergenal spines and origin and prolongation of genal spines. Trunk development of Fritzolenellus suggests that macropleurae and macrospine development are two independent processes and that the origin of the opisthotrunk is linked with the onset of phase 5 of cephalic development. The morphology of the early developmental stages of Fritzolenellus and of some related taxa differs in many aspects from the morphology of equivalent stages of some other members of Olenelloidea. Consequently, two basic morphotypes are recognized during the early development of Olenelloidea: the Fritzolenellus and the Olenellus morphotypes. Comparison with Fallotaspidoidea and Redlichiina indicates that early developmental stages of these taxa share character combinations that are typical for the Fritzolenellus morphotype. Such a comparison suggests that characters defining the Fritzolenellus morphotype are ancestral for Trilobita. The Olenellus morphotype is probably a derived condition within Olenelloidea and might be related to predator deterrence.

Defensive Venoms: Is Pain Sufficient for Predator Deterrence?

Pain, though unpleasant, is adaptive in calling an animal’s attention to potential tissue damage. A long list of animals representing diverse taxa possess venom-mediated, pain-inducing bites or stings that work by co-opting the pain-sensing pathways of potential enemies. Typically, such venoms include toxins that cause tissue damage or disrupt neuronal activity, rendering painful stings honest indicators of harm. But could pain alone be sufficient for deterring a hungry predator? Some venomologists have argued “no”; predators, in the absence of injury, would “see through” the bluff of a painful but otherwise benign sting or bite. Because most algogenic venoms are also toxic (although not vice versa), it has been difficult to disentangle the relative contributions of each component to predator deterrence. Southern grasshopper mice (Onychomys torridus) are voracious predators of arthropods, feeding on a diversity of scorpion species whose stings vary in painfulness, including painful Arizona bark scorpions (Centruroides sculpturatus) and essentially painless stripe-tailed scorpions (Paravaejovis spinigerus). Moreover, southern grasshopper mice have evolved resistance to the lethal toxins in bark scorpion venom, rendering a sting from these scorpions painful but harmless. Results from a series of laboratory experiments demonstrate that painful stings matter. Grasshopper mice preferred to prey on stripe-tailed scorpions rather than bark scorpions when both species could sting; the preference disappeared when each species had their stingers blocked. A painful sting therefore appears necessary for a scorpion to deter a hungry grasshopper mouse, but it may not always be sufficient: after first attacking and consuming a painless stripe-tailed scorpion, many grasshopper mice went on to attack, kill, and eat a bark scorpion even when the scorpion was capable of stinging. Defensive venoms that result in tissue damage or neurological dysfunction may, thus, be required to condition greater aversion than venoms causing pain alone.

Flash behavior in mammals?

Conspicuous coloration in animals has many possible functions including signaling to conspecifics, or predator deterrence through confusion, intimidation, and duping; the last includes flash behavior where predators are deceived into looking for conspicuous cues exhibited in flight but that are hidden when the animal comes to rest. In an effort to see if flash behavior occurs in mammals, we made predictions about situations where conspicuous coloration (as based on human assessment) might occur in artiodactyls and lagomorphs, and other predictions as to where such coloration might be found under an intraspecific signaling hypothesis. Using phylogenetically controlled analyses, we found that across species of artiodactyls, conspicuous rumps are more likely to have evolved in larger-sized group-living species supporting an intraspecific signaling function; this was not replicated in lagomorphs. Examining those artiodactyls that can facultatively expose color patches (putative flash behavior), we discovered that this trait occurred in artiodactyls that are solitary or living in very small groups irrespective of their body size. It is therefore possible that species such as white- and black-tailed deer, which display white rumps and tails during pursuit but hide them when stationary, are using flash behavior to confuse the predator into looking for the wrong object and thereby avoid detection and suggests that this form of antipredator defense in mammals needs greater attention. We found no effects of group size or body mass on conspicuous tail or ear markings in these taxa. Many mammals have conspicuous markings on their appendages and hindquarters, the function of which is mostly unknown. We matched these markings in rabbits, hares, and pikas and in bovids and cervids to both body size and group size across species. We found that conspicuous rumps are found in group living ungulates but when we separated these into conspicuous hindquarters always on display or that could be hidden, we found that hidden markings were principally found in species living alone or in very small groups irrespective of their body size. These species may expose conspicuous patches during flight but hide them at rest fooling the predator into searching for the wrong object, a relatively newly researched defense mechanism called flash behavior.

The effect of cyanogenic glucosides and their breakdown products on predation by domestic chicks

Cyanogenic insects release cyanide and other breakdown products that are thought to make them unpalatable to predators. Cyanogenic lepidopterans such as Heliconius butterflies and Zygaena moths are rejected by vertebrate predators, but the role played by these compounds in predator deterrence is poorly explored. Here I report tests undertook with captive domestic chicks (Gallus gallus) to evaluate the effect of cyanoglucosides, linamarin and prunasin and their breakdown products. In insects as well as plants, cyanoglucosides are enzymatically broken down when the tissue is disrupted as in the case of a predator attack. The aliphatic linamarin releases cyanide and acetone upon breakdown, while prunasin is an aromatic cyanoglucoside that releases cyanide and benzaldehyde. Using concentrations that mimicked the concentration of Heliconius butterflies, I ran trials with naive chicks by offering palatable prey laced with chemicals resulting from cyanoglucoside breakdown. I categorized prey acceptance and compared the behavior of the predators towards test and control prey. Prey coated with cyanide and benzaldehyde were rejected by the birds, while acetone elicited some avoidance behavior. Intact cyanoglucosides were not rejected by the predators presumably because of fast ingestion time or lack of enzymes to break it down. Rejection of cyanide-laced prey confirms the protective nature of cyanoglucosides against a vertebrate predator. The rejection of the pungent but not toxic benzaldehyde and the potential effect of acetone suggest that cyanoglucosides could be detected via smell as well by taste. These results provide support for cyanoglucosides as defensive chemicals of aposematic lepidopterans and related arthropods.

Variation of chemical compounds in wild Heliconiini reveals ecological factors involved in the evolution of chemical defenses in mimetic butterflies.

Evolutionary convergence of color pattern in mimetic species is tightly linked with the evolution of chemical defenses. Yet, the evolutionary forces involved in natural variations of chemical defenses in aposematic species are still understudied. Herein, we focus on the evolution of chemical defenses in the butterfly tribe Heliconiini. These neotropical butterflies contain large concentrations of cyanogenic glucosides, cyanide‐releasing compounds acting as predator deterrent. These compounds are either de novo synthesized or sequestered from their Passiflora host plant, so that their concentrations may depend on host plant specialization and host plant availability. We sampled 375 wild Heliconiini butterflies across Central and South America, covering 43% species of this clade, and quantify individual variations in the different CGs using liquid chromatography coupled with tandem mass spectrometry. We detected new compounds and important variations in chemical defenses both within and among species. Based on the most recent and well‐studied phylogeny of Heliconiini, we show that ecological factors such as mimetic interactions and host plant specialization have a significant association with chemical profiles, but these effects are largely explained by phylogenetic relationships. Our results therefore suggest that shared ancestries largely contribute to chemical defense variation, pointing out at the interaction between historical and ecological factors in the evolution of Müllerian mimicry.

Ants indirectly reduce the reproductive performance of a leafless shrub by benefiting aphids through predator deterrence

Ant–aphid mutualisms can generate cascade effects on the host plants, but these impacts depend on the ecological context. We studied the consequences of ant–aphid interactions on the reproductive performance of a Mediterranean leafless shrub (Retama sphaerocarpa), through direct and indirect effects on the arthropod community. By manipulating the presence of ants and aphids in the field, we found that ants increased aphid abundance and their persistence on the plant and reduced aphid predators by nearly half. However, the presence of ants did not affect the abundance of other plant herbivores, which were relatively scarce in the studied plants. Aphids, and particularly those tended by ants, had a negative impact on the plant reproductive performance by significantly reducing the number of fruits produced. However, fruit and seed traits were not changed by the presence of aphids or those tended by ants. We show that ants favoured aphids by protecting them from their natural enemies but did not indirectly benefit plants through herbivory suppression, resulting in a net negative impact on the plant reproductive performance. Our study suggests that the benefits obtained by plants from hosting ant–aphid mutualisms are dependent on the arthropod community and plant traits.

Phylogenetic diversity of dimethylsulfoniopropionatedependent demethylase gene dmdA in distantly related bacteria isolated from Arctic and Antarctic marine environments

Dimethylsulfoniopropionate (DMSP) is mainly produced by marine phytoplankton as an osmolyte, antioxidant, predator deterrent, or cryoprotectant. DMSP is also an important carbon and sulfur source for marine bacteria. Bacteria may metabolize DMSP via the demethylation pathway involving the DMSP demethylase gene (dmdA) or the cleavage pathway involving several different DMSP lyase genes. Most DMSP released into seawater is degraded by bacteria via demethylation. To test a hypothesis that the high gene frequency of dmdA among major marine taxa results in part from horizontal gene transfer (HGT) events, a total of thirty-one bacterial strains were isolated from Arctic Kongsfjorden seawater in this study. Analysis of 16S rRNA gene sequences showed that, except for strains BSw22118, BSw22131 and BSw22132 belonging to the genera Colwellia, Pseudomonas and Glaciecola, respectively, all bacteria fell into the genus Pseudoalteromonas. DmdA genes were detected in five distantly related bacterial strains, including four Arctic strains (Pseudoalteromonas sp. BSw22112, Colwellia sp. BSw22118, Pseudomonas sp. BSw22131 and Glaciecola sp. BSw22132) and one Antarctic strain (Roseicitreum antarcticum ZS2-28). Their dmdA genes showed significant similarities (97.7%–98.3%) to that of Ruegeria pomeroyi DSS-3, which was originally isolated from temperate coastal seawater. In addition, the sequence of the gene transfer agent (GTA) capsid protein gene (g5) detected in Antarctic strain ZS2-28 exhibited a genetically closely related to that of Ruegeria pomeroyi DSS-3. Among the five tested strains, only Pseudomonas sp. BSw22131 could grow using DMSP as the sole carbon source. The results of this study support the hypothesis of HGT for dmdA among taxonomically heterogeneous bacterioplankton, and suggest a wide distribution of functional gene (i.e., dmdA) in global marine environments.

Effect of some plant essential oils on the orientation and predation capacity of the predatory spider Pardosa pesudoannulata

Abstract Investigating the potential side-effects of plant essential oils to natural enemies is necessary before applying them in the field to control insect pests. In the present laboratory study, the attractancy/repellency of two plant oils to the spider Pardosa pseudoannulata was evaluated using a paired choice method. An individual spider was allowed to choose between the odors of essential oils extracted from Piper nigrum, Litsea cubeba, or their mixture and the control within 10 min. The predation deterrent was evaluated by observing the predation of caged spiders supplied with 20 nymphs or adults of Nephotettix cincticeps pre-treated with essential oils in 24 h. Results revealed that P. nigrum and L. cubeba oil had no significant influence on the orientation of the predator in all tested concentrations. However, the mixture of P. nigrum and L. cubeba triggered significant attraction to P. pseudoannulata at 100 and 1000 ppm. Significant reduction of predation was observed with increasing concentration of the mixture and P. nigrum alone. The predation rate in the L. cubeba assay was not significantly different among the tested concentrations. In all cases, predation was higher on nymphs than on adult stages. We did not observe any interaction effect between the life stages and concentrations. To our knowledge, this is the first study discussing the potential influence of plant essential oils on orientation and predation of P. pseudoannulata. Based on these results, some essential oils and their combinations may influence the orientation of P. pseudoannulata and might affect its predation capacity. Further field studies are needed, but these findings suggest caution regarding the selection and application of plant extracts used for biological control in rice fields.

Lizard calls convey honest information on body size and bite performance: a role in predator deterrence?

When encountering predators, prey animals often signal their ability to fight or flee to discourage the predator from an attack or pursuit. A key requirement for evolutionary stability of these predator-deterrent signals is that they convey honest information on the prey’s fighting or fleeing performance. In this study, we investigate the enigmatic ‘distress call’ of the lacertid lizard Psammodromus algirus, and test whether it conveys reliable information on an individual’s body size, and bite and sprint performance. Our acoustic analyses revealed a complex spectral structure in the vocalization of P. algirus, showing a wide frequency bandwidth, multiple harmonics, and a marked frequency modulation. This spectral design may allow such calls to be perceived by multiple potential predators, as it was assessed by a literature search comparing the call frequency range with the hearing ranges of P. algirus’ top predators. In addition, we found considerable inter-individual variation in the call design of lizards (‘call signatures’), which was linked with inter-individual variation in body size and maximum bite force, but not with sprint speed (a proxy of escape performance). As a whole, our study supports the hypothesis that the vocalizations of P. algirus lizards have the potential to serve as honest calls to deter predators. Further research on the behavioural response of predators towards lizard calls is essential in order to unravel the true predator deterrence potential of these calls. When eye-to-eye with a predator, prey animals may signal their ability to fight or flee to convince the predator not to attack or pursue them. Reptiles typically use visual displays to deter predators, but fascinatingly, Psammodromus algirus lizards have been observed to vocalize when encountered by predators. Here, we explored the acoustic properties of these calls and examined whether they convey honest information on a lizard’s fighting and fleeing performance. Our recordings indicate that the acoustic profile of the calls fall within the hearing sensitivity of the lizard’s top predators. Moreover, our experiments show a significant link between the acoustic profile of lizard calls and lizard fighting ability, but not with fleeing ability. Together, our results imply that these lizard calls have predator deterrence potential. Additionally, this study provides the first evidence of honest acoustic signalling of performance in a reptile.

Observation on rapid physiological color change in Giant tree frog Rhacophorus smaragdinus (Blyth, 1852) from Namdapha Tiger Reserve, Arunachal Pradesh, India

Many poikilotherms have the ability to change body color for homeostatic regulation, conspecific communication or predator deterrence. Physiological color change is a rapid, reversible mode of color change regulated by neuromuscular or neuroendocrine system and has been observed in several anuran species. Here we report the occurrence of physiological color change in the tree frog Rhacophorussmaragdinus (Blyth, 1852) (Amphibia, Anura, Rhacophoridae) for the first time from Namdapha Tiger Reserve, Arunachal Pradesh, India. Probable proximate causes of the behavior are discussed along with an overview of physiological color change in species of the family Rhacophoridae and nature of color change observed.

Multiple modalities in insect warning displays have additive effects against wild avian predators

Allocation to different components of defence has been suggested as an explanation for the existence of multiple aposematic morphs in a single population. We tested whether there are trade-offs between warning colouration and chemical defence or whether these have an additive effect when combined, using blue tits (Cyanistes caeruleus) as predators and the polymorphic wood tiger moth (Arctia plantaginis) as prey. We used artificial edible models (with and without the moths’ defensive fluids) with paper wings whose colour and pattern properties matched those of real moths. When the models were presented sans defensive fluids or when the fluids were presented without colour cues, we detected no differences in initial avoidance between the two morphs. However, when the colour and chemical cues were combined, differences emerged. White wings elicited higher latency to approach regardless of the defensive fluids applied on them. After approach, however, the defensive fluids of both morphs presented on moth models elicited higher latency to attack than a water control, hinting at a repellent odour. Fluids of white moths rendered lower amounts of prey eaten regardless of wing colour, while yellow moths’ fluids provoked the highest occurrence of beak wiping behaviour. Our findings highlight the importance of accounting for interactive effects between different signal modalities, as these can create patterns not detectable when examined in isolation. Understanding these interactions is vital to determine how different components of multimodal warning displays provide protection at different stages of a predation event and, potentially, how multiple morphs can co-occur in a population.Significance statementThere are many things that can stop a predator attacking a prey such as looking scary or smelling bad, but if a predator does take a bite, tasting bad can make the difference between life and death for the prey. When combined with bright conspicuous colours, both repellent odours and deterrent tastes (i.e. chemical defences) can help predators learn to avoid unprofitable prey. However, it is unclear whether it is really the sum of these visual and chemical signals that most effectively deters predators or whether one is more important than the other. Examining the effects of warning colour and chemical defence in white and yellow wood tiger moths on wild-caught birds, we show that neither aspect of the moths’ defence in isolation is as effective for predator deterrence as the sum of both.

Buzz Kill: Function and Proteomic Composition of Venom from the Giant Assassin Fly Dolopus genitalis (Diptera: Asilidae).

Assassin flies (Diptera: Asilidae) inject paralysing venom into insect prey during hunting, but their venoms are poorly characterised in comparison to those produced by spiders, scorpions, or hymenopteran insects. Here we investigated the composition of the venom of the giant Australian assassin fly Dolopus genitalis using a combination of insect microinjection assays, calcium imaging assays of mammalian sensory neurons, proteomics and transcriptomics. Injection of venom into blowflies (Lucilia cuprina) produced rapid contractile paralysis (PD50 at 1 min = 3.1 μg per fly) followed by death, and also caused immediate activation of mouse dorsal root ganglion neurons (at 50 ng/μL). These results are consistent with venom use for both prey capture and predator deterrence. Paragon searches of tandem mass spectra of venom against a translated thoracic gland RNA-Seq database identified 122 polypeptides present in the venom, including six linear and 21 disulfide-rich peptides. Some of these disulfide-rich peptides display sequence homology to peptide families independently recruited into other animal venoms, including inhibitor cystine knots, cystine-stabilised α/β defensins, Kazal peptides, and von Willebrand factors. Numerous enzymes are present in the venom, including 35 proteases of the S1 family, proteases of the S10, C1A, M12A, M14, and M17 families, and phosphatase, amylase, hydrolase, nuclease, and dehydrogenase-like proteins. These results highlight convergent molecular evolution between the assassin flies and other venomous animals, as well as the unique and rich molecular composition of assassin fly venom.