Introducing an innovative semi‐captive environment for the Philippine tarsier (Tarsius syrichta)

In response to demands for research, captive breeding, and tourism, a semi‐captive environment was created for the Philippine tarsiers (Tarsius syrichta) in Corella, Bohol, Philippines. The 7600‐m² enclosure was continuous with the surrounding habitat, and utilized a unique predator control fence design and a lighting system to attract nocturnal insects. During 2 years of observation, the locations of over 500 tarsier sleeping sites were recorded. Tarsiers were found to prefer dense, low‐level vegetation in secondary forests, with perching sites averaging 2 m above the ground. Up to 10 tarsiers were observed within the enclosure at one time, which is a high density compared to densities based on home‐range estimates for wild tarsiers in the vicinity of the study site. In addition, the tarsiers were observed to be more social than previously reported. Zoo Biol 24:101–109, 2005. © 2005 Wiley‐Liss, Inc.     

Distribution and feeding behaviour of field populations of the water cricket Velio, caprai (Hemiptera)

1. The distribution of individuals, prey capture success and prey choice were studied in a water cricket (Velia caprai) population in southern Ireland. Groups of different sizes were observed in the field during the summer and all potential prey animals entering the groups were counted. Surface drift samples were collected to assess the proportion of profitable prey items. 2. Two types of Velia groups were observed: mixed groups (adults and juvenile instars 4 and 5) and juvenile groups (instars 1–3), A greater proportion of the available prey was captured by the mixed groups. 3. Individuals in large groups had a lower capture rate than individuals in small groups. 4. No differences in capture rates could be found between males, females and juveniles, but differences in prey choice were apparent. Females captured more large prey than expected. 5. Water cricket distribution in the stream did not follow the ‘ideal free’ model; too few individuals were found at the most profitable sites. Food might not be the limiting factor during summer, and other factors such as intraspecific interference and predator avoidance could be more important.     

The effects of prey species on food conversion efficiency and growth of an insectivorous lizard

Little is known about the effects of different prey species on lizard growth. We conducted a 6‐week study to determine the relative effects of prey species on growth parameters of hatchling western fence lizards, Sceloporus occidentalis. Lizards were fed house cricket nymphs, Acheta domesticus, or mealworm larvae, Tenebrio molitor. The effects of prey species on growth were determined by measuring prey consumption, gross conversion efficiency of food [gain in mass (g)/food consumed (g)], gain in mass, and gain in snout–vent length. Lizards grew well on both the prey species. However, lizards that fed on crickets consumed a significantly higher percentage of their body mass per day than those fed mealworms. Nevertheless, lizards that consumed mealworms ingested significantly more metabolizable energy, had significantly higher food conversion efficiencies, significantly higher daily gains in mass, and significantly greater total growth in mass than lizards that fed on crickets. Zoo Biol 27:181–187, 2008. © 2008 Wiley‐Liss, Inc.     

Presampling sensory information and prey density assessment by wolf spiders (Araneae, Lycosidae)

Decisions regarding foraging patch residence time and the assessmentof patch quality may be mediated by various sources of information.This study examined the use of sensory cues by hunting spidersto assess prey density in the absence of prey capture. Adultfemale wolf spiders [Schizocosa ocreata (Hentz); Lycosidae]had food withheld for 4 days and then were exposed to artificialforaging patches containing four densities of crickets (0, 3,10, 20) with different sensory stimuli (visual and vibratoryinformation, visual only, and vibratory only). The spiders werenot allowed to feed during trials, and patch residence timewas recorded. The spiders varied patch residence time basedon sensory cues alone and spent more time in patches with higherprey density. With visual information only, spiders could apparentlydistinguish among prey densities almost as well as with visualand vibratory cues combined, but residence time did not differamong prey densities when only vibratory information was presented.Measurements of vibration levels produced by cricket activityunder experimental sensory treatments conform to test results,suggesting that visual detection of crickets is important inpatch assessment used in determining patch residence time.     

Passive sound localization of prey by the pallid bat (Antrozous p. pallidus)

Summary The pallid bat (Antrozous p. pallidus) uses passive sound localization to capture terrestrial prey. This study of captive pallid bats examined the roles of echolocation and passive sound localization in prey capture, and focused on their spectral requirements for accurate passive sound localization.Crickets were used as prey throughout these studies. All tests were conducted in dim, red light in an effort to preclude the use of vision. Hunting performance did not differ significantly in red light and total darkness, nor did it differ when visual contrast between the terrestrial prey and the substrate was varied, demonstrating that the bats did not use vision to locate prey.Our bats apparently used echolocation for general orientation, but not to locate prey. They did not increase their pulse emission rate prior to prey capture, suggesting that they were not actively scanning prey. Instead, they required prey-generated sounds for localization. The bats attended to the sound of walking crickets for localization, and also attacked small, inanimate objects dragged across the floor. Stationary and/or anesthetized crickets were ignored, as were crickets walking on substrates that greatly attenuated walking sounds. Cricket communication sounds were not used in prey localization; the bats never captured stationary, calling crickets.The accuracy of their passive sound localization was tested with an open-loop passive sound localization task that required them to land upon an anesthetized cricket tossed on the floor. The impact of a cricket produced a single 10–20 ms duration sound, yet with this information, the bats were able to land within 7.6 cm of the cricket from a maximum distance of 4.9 m. This performance suggests a sound localization accuracy of approximately ±1° in the horizontal and vertical dimensions of auditory space. The lower frequency limit for accurate sound localization was between 3–8 kHz. A physiological survey of frequency representation in the pallid bat inferior colliculus suggests that this lower frequency limit is around 5 kHz.     

Gleaning bat echolocation calls do not elicit antipredator behaviour in the Pacific field cricket, <Emphasis Type="Italic">Teleogryllus oceanicus</Emphasis> (Orthoptera: Gryllidae)

Bats that glean prey (capture them from surfaces) produce relatively inconspicuous echolocation calls compared to aerially foraging bats and could therefore be difficult predators to detect, even for insects with ultrasound sensitive ears. In the cricket Teleogryllus oceanicus, an auditory interneuron (AN2) responsive to ultrasound is known to elicit turning behaviour, but only when the cricket is in flight. Turning would not save a cricket from a gleaning bat so we tested the hypothesis that AN2 elicits more appropriate antipredator behaviours when crickets are on the ground. The echolocation calls of Nyctophilus geoffroyi, a sympatric gleaning bat, were broadcast to singing male and walking female T. oceanicus. Males did not cease singing and females did not pause walking more than usual in response to the bat calls up to intensities of 82 dB peSPL. Extracellular recordings from the cervical connective revealed that the echolocation calls elicited AN2 action potentials at high firing rates, indicating that the crickets could hear these stimuli. AN2 appears to elicit antipredator behaviour only in flight, and we discuss possible reasons for this context-dependent function.     

The Effect of Variation in Prey Movement on the Predatory Response of Jacky Lizards (Amphibolurus muricatus)

The sensory systems of animals have evolved to meet the demands of functionally critical events. Animals that rely on visual motion cues must ignore irrelevant movement and only attend to certain characteristics that warrant further consideration. For the Australian jacky lizard ( Amphibolurus muricatus ), movement is essential for detecting potential prey. Here we examine whether differences in the actual motion characteristics of a simulated prey item influence predatory behaviour. We begin with direct observations of responses to live prey items to define an ordinal scale for subsequent video playback experiments involving a synthetic prey item (an animated cricket). In expt 1, we show that the responses of lizards to the synthetic prey were matched to those given in response to video of an actual cricket. In expt 2 we manipulated the movement patterns of the synthetic cricket based on motion analysis of actual prey movement. Manipulating motion characteristics did not influence the level of predatory behaviour observed, however, lizards showed sustained predatory behaviour to stimuli with speed characteristics that were matched to those of real crickets. We discuss the possibility that recent experience of prey movement in captivity has influenced the foraging behaviour of these lizards.     

Males make poor meals: a comparison of nutrient extraction during sexual cannibalism and predation

Cannibalism is hypothesized to have evolved as a way to obtain a high-quality meal. We examined the extraction of lipid and protein by female wolf spiders, Hogna helluo, during sexual cannibalism of males and predation of crickets. Most food-limited females did not cannibalize males but immediately consumed a size-matched cricket. When consuming male H. helluo and crickets, female H. helluo only consumed 51% of the male body while they consumed 72% of the cricket body. While males had higher protein content in their bodies than crickets and other insects, female H. helluo ingested similar amounts of protein from male H. helluo and crickets. Female H. helluo extracted 47% of the protein present in male H. helluo and 67% of the protein present in crickets. Females were able to extract nearly all of the lipid present in male H. helluo and crickets. However, crickets and other insects had almost 4 times higher lipid content than male H. helluo. The ratio of lipid to protein consumed from crickets appeared more similar to the nutritional requirements of egg production than that of males. Taken together, female hesitancy to engage in cannibalism, low extraction of nutrients from males and a low ratio of lipid to protein in the food extracted from males suggest that males may be poor-quality prey items compared to common insects such as crickets.     

Chemical‐Mediated Predator Avoidance in the European House Cricket (Acheta domesticus) is Modulated by Predator Diet

Chemical information often mediates interactions between predators and prey, and threat‐sensitivity theory includes predictions that prey species should respond to chemical signatures of predators in a manner that is commensurate with the level of the assessed threat. Using the European house cricket (Acheta domesticus), we explored the influence of diet‐derived cues from the centipede Scolopocryptops sexspinosus on anti‐predator behavior in three laboratory experiments. In experiment 1, we compared the amount of time that adult female crickets spent on untreated filter paper and filter paper exposed to centipedes fed either the larvae of Hermetia illucens (black soldier fly), crickets, or a mixture of fly larvae and crickets. We discovered that crickets spent significantly less time on filter paper exposed to centipedes fed crickets only or a mixture of crickets and fly larvae compared with blank filter paper or filter paper exposed to centipedes fed fly larvae only. In our second experiment, we compared the amount of time that crickets spent on blank filter paper and filter paper exposed to adult female conspecifics to rule out the possibility that crickets simply avoid all filter paper exposed to metabolic by‐products, and crickets exhibited no discrimination. In our third experiment, we tested the potential effects of diet order on anti‐predatory behaviors. Specifically, we compared the amount of time that adult female crickets spent on filter paper exposed to centipedes fed fly larvae followed by crickets and filter paper exposed to centipedes fed crickets followed by fly larvae. We discovered no diet sequence effect. Our study demonstrates that European house crickets are sensitive to the chemical cues of their centipede predators, but only when centipedes have fed upon crickets.     

Reproductive cycles in Tarsius bancanus

The reproductive condition of three pairs of Bornean tarsiers (Tarsius bancanus) was documented for 16 months. Each pair was housed separately under a constant photoperiod (L:D = 11.5:12.5) similar to that in their native habitat. Reproductive cycles of females were monitored visually for 6 months and were then monitored with vaginal smears and measurements of external genitalia for an additional 10 months. Progressive proliferation and cornification of vaginal epithelial cells during proestrus and estrus was accompanied by an enlargement of the external genitalia. Cycle lengths averaged 24.0 ± 3.2 days. The external genitalia were swollen each cycle for a period of 6–9 days. Copulations occurred on the 1st day of estrus, which lasted 1–3 days. No menstruation was observed. There was no evidence of seasonality of estrous cycles with this photoperiod. Testicular measurements of males showed no overt seasonal changes. There was variation in testicular size, and one male copulated at a range of testicular sizes. The data indicate that T. bancanus has estrous cycles similar to those of prosimian primates and some New World monkeys and that these cycles occur throughout the year under constant photoperiodic conditions.     

A captive behavioral enrichment study with Asian small-clawed river otters (Aonyx cinerea)

Asian small-clawed river otters (Aonyx cinerea) were given the opportunity to hunt for and capture live crickets (Acheta domestica) in a public interactive display. The otters learned the experimental routine during the first day of exposure. Different response levels were recorded at each of three capture sites, A, B, and C. The animals showed continued motivation for hunting despite the fact that there was no deprivation and the crickets represented an insignificant part of the diet. Besides live crickets, other items—cat food, dead crickets, and gelatin capsules—were introduced for five days each. The otters made the most captures per opportunity for live crickets, followed, in order of preference, by dead crickets, cat food, and gelatin capsules. Although gelatin capsules were found to be the least motivating prey item, the otters hunted for them whenever they were offered. Thus, any active opportunity to produce a change in their environment was rewarding to the otters.     

Landscape and weather determinants of prey availability: implications for the Lesser Kestrel Falco naumanni

Spatial and temporal variation in prey abundance have been shown to impact the time of breeding and breeding success of birds. Understanding the ecological requirements of preferred prey can help develop management measures to improve food supply for target species. For the colonial Lesser Kestrel Falco naumanni, mole crickets Gryllotalpa spp. are one of the most important prey items during the mate‐feeding period. Lesser Kestrel colonies with higher mole cricket consumption had earlier egg‐laying dates, suggesting that differences between individuals in the time of breeding could be caused by differences in the diet. Moreover, the mean number of mole crickets in pellets was significantly correlated with clutch size (in one of the studied years) and egg volume. Thus, the impact of environmental variables and land use on mole crickets is likely to be relevant to Lesser Kestrel conservation. Weekly consumption of mole crickets was higher following an increase in either precipitation or minimum temperature values. Furthermore, mole cricket consumption was higher in colonies surrounded by higher quality soils and in wetter areas and years. Predicted probability of mole cricket occurrence in surveyed watercourse margins suggested a positive relationship between soil penetrability and mole cricket occurrence. Among variables that might be the target of management, the presence of riparian vegetation positively influenced the occurrence of mole crickets, whilst tillage and sowing of streambeds were revealed as the most important threats. We suggest that the maintenance of native vegetation in the margins of watercourses could improve soil resilience to erosion, increase water retention, soil penetrability and fertility, and provide a food supply and shelter for mole crickets. Overall, the implementation of such recommendations is likely to benefit other farmland species known to consume mole crickets, including several endangered species.     

Knowing the Risk: Crickets Distinguish between Spider Predators of Different Size and Commonness

Predators unintentionally release chemical and other cues into their environment that can be used by prey to assess predator presence. Prey organisms can therefore perform specific antipredator behavior to reduce predation risk, which can strongly shape the outcome of trophic interactions. In contrast to aquatic systems, studies on cue‐driven antipredator behavior in terrestrial arthropods cover only few species to date. Here, we investigated occurrence and strength of antipredator behavior of the wood cricket Nemobius sylvestris toward cues of 14 syntopic spider species that are potential predators of wood crickets. We used two different behavioral arena experiments to investigate the influence of predator cues on wood cricket mobility. We further tested whether changes in wood cricket mobility can be explained by five predator‐specific traits: hunting mode, commonness, diurnal activity, predator–prey body–size ratio, and predator–prey life stage differences. Crickets were singly recorded (1) in separate arenas, either in presence or absence of spider cues, to analyze changes in mobility on filter paper covered with cues compared with normal mobility on filter paper without cues; and (2) in subdivided arenas partly covered with spider cues, where the crickets could choose between cue‐bearing and cue‐less areas to analyze differences in residence time and mobility when crickets are able to avoid cues. Crickets either increased or reduced their mobility in the presence of spider cues. In the experiments with cues and controls in separate arenas, the magnitude of behavioral change increased significantly with increasing predator–prey body size ratio. When crickets could choose between spider cues and control, their mobility was significantly higher in the presence of cues from common spider species than from rare spiders. We therefore conclude that wood crickets distinguish between cues from different predator species and that spiders unintentionally release a species‐specific composition and size‐dependent quantity of cues, which lead to distinct antipredator behavior in wood crickets.     

Space and substrate use in captive western tarsiers,Tarsius bancanus

Tarsiers are considered “vertical clingers and leapers” but there are few empirical data available concerning actual substrate- or space- use patterns in any of the three species. In this paper we examine these patterns in four wild-caught, captive Tarsius bancanusmaintained in large enclosures designed to promote natural behavior. We find that this species uses space in a distinctly nonrandom manner, exhibiting a preference for midlevel heights and upright, small-diameter substrates. The observed space-utilization pattern was best explained by strong preferences for specific heights and not by the distribution of prey items, preferred substrate types,or substrate angles. Unlike wild T. bancanus,which reportedly forage consistently on the ground, these tarsiers did not forage on the floor of the enclosures despite the abundance of food there.     

The Feeding Behaviour of a Sit-and-Wait Predator,Ranatra dispar (Heteroptera: Nepidae): The Combined Effect of Food Deprivation and Prey Size on the Behavioural Components of Prey Capture

Previous work has shown a significant effect of hunger on the predatory behaviour in a sit-and-wait predator Ranatra dispar, the water stick insect (Bailey 1986 a). The experiments reported here were designed to investigate the combined effect of prey size and hunger on the predatory behaviour in order to identify which behavioural components are effected. It was found that the hunger level determines whether R. dispar will initially be aroused or not but the distance at which the arousal takes place is influenced by the size of the prey. This is believed to reflect the capacity and interrelation between visual and mechanoreceptor, sensory organs. The decision to strike at a prey is, although again influenced by hunger, significantly affected by prey size. The distance of the prey when the strike takes place is affected by hunger not the size of the prey. The outcome of the strike is determined by the size of the prey, not the hunger level of the predator. This is believed to reflect the relationship between strike trajectory, leg morphology and prey size. Food deprivation affects all components of predatory behaviour of R. dispar leading up to prey capture, by increasing not only distance of response but also the number of strikes, hits, and captures per unit presentation of prey. It does not affect capture efficiency which remains at about 70 to 80 %. Food deprivation also increases the range of prey sizes that R. dispar responds to and attempts to capture. The effect of food deprivation is considered to reflect a motivational change in responsiveness to particular prey stimuli usually described as a sensitization of particular stimulus-response relations rather than the food deprivation affecting the sensory mechanisms. The predatory success in relation to size of model prey suggested a hypothetical size that could be captured, irrespective of predator motivational level, which is based primarily on the relationship between the shape of the grasping leg and size of prey.     

Factors shaping latitudinal patterns in communities of arboreal spiders in northern Europe

Predator effects on herbivores are often referred to as examples of biotic interactions that weaken with latitude, but more studies are needed to test for the generality of this pattern. To further the understanding of large‐scale geographical patterns in abundance and diversity of predatory arthropods, from 2008–2011 we explored spider communities in the canopies of primary forest trees of the boreal zone (Pinus sylvestris, Picea abies, Betula pubescens and B. pendula) along five latitudinal gradients in northern Europe, from 59 to 70°N and from 10 to 60°E. The abundance of arboreal spiders in Norway and Finland was about a half of that in Russia, presumably due to more intensive forest management in Scandinavia. The abundance, taxonomic and functional diversity of arboreal spiders generally decreased with latitude; however, actual weather conditions during the study years had little effect on this pattern. Coniferous species supported higher abundance and diversity of arboreal spiders than birches, but the poleward decrease in either abundance or taxonomic diversity of arboreal spiders did not differ between coniferous and deciduous tree species. In contrast, functional diversity on birches decreased with latitude greater than on coniferous trees. Euryphagous spiders showed stronger decrease with latitude in terms of both abundance and taxonomic diversity than more specialized (steno‐ and oligophagous) spiders. We attribute the general decrease in density and diversity of spiders with latitude to an increased pressure from apex predators (birds) rather than to direct effects of climate or changes in prey abundance. The abundance of spiders declined with the latitude to the greater extent than the densities of their potential prey did, suggesting a decrease in the strength of predator–prey interactions towards the north.     

Temporal Shifts in Conspicuousness: Mate Attraction Displays of the Texas Field Cricket, Gryllus texensis

Conspicuous mate attraction displays can simultaneously draw the attention of potential mates and predators, placing the signaller in peril of becoming prey. The balance between these countervailing forms of selection has the potential to shape mate attraction displays. Male Texas field crickets (Gryllus texensis; Orthoptera) signal acoustically to attract mates. Mating signals also attract acoustically orienting parasitoid flies (Ormia ochracea; Tachinidae). Both the abundance of female crickets and parasitoid flies fluctuates throughout the night. We show mate attraction displays exhibit diel shifts that correlate positively with expected female cricket presence and negatively with expected parasitoid fly activity. During early evening, when parasitoids are most common and mating is scarce, crickets signal less often and with reduced conspicuousness. During the second half of the evening, when sexually receptive females are abundant and parasitoids are scarce, crickets signal more often and with enhanced conspicuousness. These diel shifts in mate attraction displays do not appear to result from male crickets detecting parasitoid flies or female crickets and altering their behaviour accordingly. Males in close proximity to parasitoid flies or female crickets do not signal differently than lone males. Instead, diel pattern shifts in mate attraction displays appear to be a selective response to trade‐offs between natural selection via parasitism and sexual selection via mate choice.     

Parasite‐induced Changes in the Anti‐predator Behavior of a Cricket Intermediate Host

Many parasites with complex life cycles are known to modify their host phenotype to enhance transmission from the intermediate host to the definitive host. Several earlier studies explored these effects in acanthocephalan and trematode parasites, especially in aquatic ecosystems; however, much less is known about parasite‐mediated alterations of host behavior in terrestrial systems involving nematodes. Here, we address this gap by investigating a trophically transmitted nematode (Pterygodermatites peromysci) that uses a camel cricket (Ceuthophilus pallidipes) as the intermediate host before transmission to the final host, the white‐footed mouse (Peromyscus leucopus). In a laboratory experiment, we quantified the anti‐predatory responses of the cricket intermediate host using simulated predator cues. Results showed a decrease in jumping performance among infected crickets as compared with uninfected crickets, specifically in terms of frequency of jumps and jumping distance. Additionally, the relationship between parasite load and frequency of jumps is negatively correlated with the intensity of infection. These behavioral modifications are likely to increase vulnerability to predation by the definitive host. An analysis of the age‐intensity pattern of infection in natural cricket populations appears to support this hypothesis: parasites accumulate with age, peak at an intermediate age class before the intensity of infection decreases in older age groups. We suggest that older, heavily infected crickets are preferentially removed from the population by predators because of increased vulnerability. These results show that cricket intermediate hosts infected with P. peromysci have diminished jumping performance, which is likely to impair their anti‐predatory behavior and potentially facilitate parasite transmission.     

Jamaican Field Cricket Mate Attraction Signals Provide Age Cues

Older males often have a mating advantage, either resulting from the fact that they live longer or resulting from the fact that they both live longer and signal this to females. Male field crickets signal acoustically to attract potential mates. Some field cricket mating signals provide cues about male age while others do not. We explored whether male Jamaican field crickets, Gryllus assimilis, mating signals change with age. Our results show that older males produce chirps with longer pulses, more pulses, at higher pulse and chirp rates, and their chirps are both longer and louder than those produced by younger males. Our findings suggest that Jamaican field cricket mating signals provide cues about male age, explaining between 10% and 54% of the variation in signaling traits. Females might be able to use these mating signal differences to distinguish between older and younger mates.