Conspecific Predators Research Articles

Are the ladybugs Cryptolaemus montrouzieri and Exochomus quadripustulatus (Coleoptera: Coccinellidae) candidate predators of Toumeyella parvicornis (Hemiptera: Coccidae)?

Toumeyella parvicornis is an alien pest of recent introduction in Italy that infests stone pines (Pinus pinea L.), its main host plant in Europe. Infestations are currently controlled through endotherapic treatments, but the high costs and the long-term inefficacy highlight the need for alternative control strategies applicable in natural systems as well. An analysis of the effectiveness of autochthonous and naturalized predators is the first step to achieve this goal. This work focused on two candidate predators, Exochomus quadripustulatus and Cryptolaemus montrouzieri (Coleoptera: Coccinellidae), that may potentially control T. parvicornis. The analysis was carried out under laboratory-controlled and semi-field conditions. Laboratory tests were carried out to assess: (i) the predation rate of the ladybugs over different densities of pest preimaginal stages, and (ii) the effect of the presence of heterospecific and conspecific predators on the attractiveness of prey colonies. Semi-field experimentations were carried out by wrapping infested stone pine twigs with net sleeves and applying one of three treatments: (i) Exochomus quadripustulatus, (ii) Cryptolaemus montrouzieri, and (iii) control containing only the pest population. Both the ladybugs were attracted by T. parvicornis, offered as prey. Exochomus quadripustulatus was more attracted to conspecific and heterospecific ladybugs than Cryptolaemus montrouzieri and responded to prey more quickly. The results obtained could be useful for planning further experimentations to explore the potential use of these predators in biological control programs that may be applied in infested areas. Besides the use in an urban context, where pesticide use is strongly limited, the release of natural enemies may help safeguard stone pine forests. © 2024 Society of Chemical Industry.

Investigating conspecific CsRV1 transmission in Callinectes sapidus

A reo-like virus, CsRV1, is found in blue crabs, Callinectes sapidus, from every North American location assessed, including Chesapeake Bay and the Atlantic and Gulf coasts, USA and associated with blue crabs in softshell production. CsRV1-associated crab mortality is prevalent in captive crabs, but it is still unknown how CsRV1 is transmitted. The purpose of this study was to examine the role that conspecific predation or scavenging may play in per os transmission in single exposure and repeated exposure experiments. For viruses without cell culture propagation, repeated exposure experiments have the challenge of presenting the virus consistently during the experiment and across time replicates. In a single-exposure experiment, none of the crabs fed muscle tissue of crabs carrying intense infections of CsRV1 developed CsRV1 infections. In a repeated-exposure trial, using infected muscle tissue prepared in alginate blocks, CsRV1 was detected in 11% of the crabs fed infected tissue but was not significantly different from the control group fed alginate lacking CsRV1. For repeated per os exposure experiments, the study demonstrated the utility of using alginate to present the same homogenous sample of virus, both injected and per os, over time for oral challenge experiments. Conspecific predation and scavenging could be a transmission route, but future work into this and other possible routes of transmission for CsRV1 is important to better understand the role this virus plays in wild crab populations and the soft-shell crab industry.

Diverse strategies that animals use to deter intraspecific predation.

Intraspecific predation is a special case of prey-predator system that is taxonomically widespread. While a heterospecific predator's main goal is to achieve nutrition, intraspecific predation provides conspecifics with other benefits including elimination of competitors for resources and mates. Traditionally intraspecific predation is termed based on the context they occur within, for example egg cannibalism, infanticide and sexual cannibalism. These diverse forms of intraspecific predation and the strategies by which animals are known to deter them are summarized categorically in this review. The diversity of defence strategies animals deploy against conspecific predators is appreciable and raises interesting questions on their evolution for future research.

Cannibalism in the Early Jurassic bony fish Pachycormus macropterus (Teleosteomorpha: Pachycormiformes) and its paleoecological significance

ABSTRACT Cannibalism (conspecific predation) is a surprisingly common and widespread behavior in modern ecosystems; however, direct evidence for cannibalism is strongly lacking in the fossil record. Identifying cannibalism is important to help better understand recondite trophic interactions between extinct species, as well as to detect potential resource pressures and competition in their ecosystems. Here, I describe the first direct evidence for a cannibalistic diet in a pachycormiform fish, based on three exceptionally well-preserved specimens of Pachycormus macropterus (de Blainville, 1818) with conspecific gut contents from the Early Jurassic (Toarcian) of Normandy (France). The generalist diet of Pachycormus is proven to be more complex than previously considered, which has recently been shown to include vampyropod squids, belemnoteuthids, ammonites, and small teleosts. All of the prey fishes were ingested whole in a longitudinal orientation, revealing that Pachycormus actively hunted juveniles of its own kind and was an indiscriminate opportunistic predator. The cannibal individuals themselves are also juveniles, further supporting previous findings for a dietary shift in Pachycormus from piscivorous to teuthophagous over ontogeny. Despite a widespread European distribution of Pachycormus, only specimens from the Normandy area show evidence for cannibalism, suggesting that the more conventional prey resources were either scarce or restricted at the site, prompting Pachycormus juveniles to indiscriminately predate on one another.

Cannibalism in Microlophus Lizards

Cannibalism involves killing and consuming an individual of the same species. Different factors modulate cannibalism, and here we explored whether the diet diversity would mediate the cannibalism propensity in Microlophus lizards. We compiled the available information on diet and cannibalism of the 22 Microlophus species. We found that there is a relatively high incidence of cannibalism within Microlophus, as 41% of the species exhibited this behavior. There are, however, few reports of cannibalism by each species. Cannibalism propensity showed a positive association with diet diversity, which suggests that a generalist diet might provide room for cannibalism in Microlophus lizards. We also found that only adults, mostly males, consume juveniles. Conspecific predation pressure may explain the habitat segregation among age classes reported in some Microlophus species that exhibit cannibalism. Finally, cannibalism appears to be an ancestral condition in Microlophus, as it occurs in the two main clades of this genus. Moreover, Tropidurus, the sister taxon of Microlophus, also includes species that exhibit cannibalism, and the ancestor of these genera may have exhibited cannibalism.

Who let the young-of-the-year (YOY) up? The pelagic habitat as a nursery and feeding ground area for the YOY Argentine hake Merluccius hubbsi Marini, 1933.

The young-of-the-year (YOY) Argentina hake Merluccius hubbsi remained at particular distances off the seabed at pelagic habitat, in a nursery area located in the San Jorge Gulf off south-western Atlantic. Older specimens were daylight distributed near the bottom in the demersal habitat. In this paper the authors show that the pelagic habitat is favourable for YOY hake compared to the surrounding demersal habitat by decreasing the probability of encounter with larger hake protecting the YOY against conspecific predation, and providing a better food supply. From 303 stomachs of pelagic YOY Argentine hake analysed (60-250 mm), 274 (90.43%) contained prey. Pelagic Argentine YOY hake fed almost exclusively on zooplanktonic crustaceans (Euphausia spp. and Themisto gaudichaudii). From 980 demersal specimens (14-82 cm), 572 (58.36%) contained prey, mainly the lobster krill Munida gregaria, followed by other hakes by cannibalism. The intensity of feeding was higher on pelagic layers. The allometric weight-length relationship revealed that the YOY Argentine hake find sufficient food in the pelagic habitat to live and develop, by increasing their relative body thickness. The cannibalism increases from close to zero when the YOY hake are c. 20 m off the seabed, to between 15% (cold season) and 20% (warm season) when they are 10 m off the seabed. These results suggest that the pelagic habitat is a feeding ground for YOY hake, and it is a favourable one compared to the surrounding demersal habitat by protecting the YOY from cannibalism. Pelagic YOY hakes were less abundant and more distant from the bottom during the cold season (14.3 m) than during warm one (11.4 m), probably because of natural mortality and progressive recruitment to demersal habits.

Influence of intraspecific competition for food on the bodyweight of the adult aphidophagous ladybird, Coccinella transversalis

Aggregation of conspecific predators sharing a common prey, influences their bodyweights. We investigated the influence of intraspecific competition of adult ladybirds of Coccinella transversalis Fabricius on their bodyweight feeding on rusty plum aphid, Hysteroneura setariae (Thomas). Adult males and females consumed a significantly greater number of aphids with increase in predator-density, however, the aphid-consumption per predator declined with this increase. The weight gain per predator also decreased linearly with increase in the density of both male and female predators. This indicates that the weight-gain of the predator is a function of the prey consumed. The searching efficiency decreased with increase in predator density due to mutual inference. The mutual interference constants for adult male and female ladybirds were −0.419 and −0.546, respectively. The females consumed a greater number of aphids than males. The killing power of the ladybird denoted by the k-value increased curvilinearly with increase in predator density. We conclude that prey consumption is a function of body size and that the offspring of those that aggregate at low densities in prey-rich habitats develop into large adults.

Behavioral responses of the European mink in the face of different threats: conspecific competitors, predators, and anthropic disturbances

Prey species assess the risk of threat using visual, olfactory, and acoustic cues from their habitat. Thus, they modify their behavior in order to avoid encounters with competitors, predators, and human disturbances that endanger their fitness. European mink (Mustela lutreola) is a critically endangered species that can be preyed upon by larger carnivores and displaced by dominant conspecifics to areas of lower quality, e.g., near to more anthropized localities which may be noisier. In this study, the behavioral responses of 24 European mink were evaluated by conducting an experiment in which the presence of a conspecific competitor was simulated with a visual cue (mirror) and the presence of predators (terrestrial and aerial) with odorous cues. Additionally, they were also exposed to potential sources of anthropic disturbance with acoustic cues (road traffic noise and human voices). Our results showed that European mink were hidden for longer periods of time due to the presence of conspecifics and being exposed to the fecal odors of a terrestrial predator such as dog, but especially when they were exposed to anthropic noises. In the presence of a conspecific, the females and the subadults were the ones who remained hidden for the longest time. As well, they were hidden for longer periods of time due to the presence of conspecifics but in combination with dog feces and anthropic sounds did not induce variations in the response, as both by themselves already triggered an increase in the time they spent hiding. The vigilance model showed the effects of the same factors as the hiding model, but with antagonistic effects in the case of vigilance time which decreased during anthropic noises exposition. Finally, we want to highlight that European mink showed an innate response favorable to all three types of threats, but attention should be focused on human disturbances—as they trigger the most extreme responses—which may affect the rate of survival of this threatened species.

Plant defense responses triggered by phytoseiid predatory mites (Mesostigmata: Phytoseiidae) are species-specific, depend on plant genotype and may not be related to direct plant feeding

Zoophytophagous arthropods can elicit plant defense responses affecting potential prey beyond predation. Phytophagy prevails as the main trigger for these responses, as in the case of Euseius stipulatus (Athias-Henriot) (Mesostigmata: Phytoseiidae), a predator occurring in citrus. Because other triggers cannot be excluded, our aim was to examine whether other phytoseiids co-occurring with E. stipulatus but not engaged in plant feeding [Neoseiulus californicus (McGregor) and Phytoseiulus persimilis Athias-Henriot] could induce similar responses (in terms of herbivore induced plant volatiles, HIPVs, and main defensive pathways), and how these affected the behavior of conspecifics and the shared prey, Tetranychus urticae Koch (Prostigmata: Tetranychidae). N. californicus triggered plant genotype-specific defense responses, including the production of different HIPVs compared to clean plants. However, we could not observe these effects for P. persimilis. T. urticae avoided better protected plants, because of stronger direct or indirect defense. As plants with weaker direct defense levels should offer higher prey densities, and those harboring conspecific predators represent higher risk of cannibalism, predators were expected to behave similarly. However, they did not. Our results demonstrate that plant defense triggered by phytoseiids is species-specific, depend on plant genotype and can be triggered by non-feeding activities. As N. californicus is a highly efficient predator used worldwide, further studies with this species are needed. Likewise, cineol, one of the volatiles identified in the blends triggered by this phytoseiid, could be used to manipulate the prey. These studies could pave the way for a more efficient use of phytoseiids in agroecosystems.

Life history traits of parental care in Crenicichla lepidota (Cichliformes, Geophagini) in the upper Paraguay River basin, Brazil

During focal observations carried out in the Olho d’Água River, upper Paraguay River basin, Brazil, we registered the defensive behaviour of one pair of Crenicichla lepidota attempting to protect their offspring from conspecific and non-specific predators. Adults exhibited substrate-guarding behaviour and displayed primary and secondary anti-predation mechanisms. The primary mechanisms (e.g., fin flicking and flaring, gill extending) were ineffective against conspecific predators or against other species. Secondary mechanisms included charging would-be predators of the offspring, and this tactic was successful against non-specifics. This record confirms, in the wild, agonistic behaviour as an effective secondary defence mechanism used in parental care in Crenicichla lepidota.

Density dependence mediates the ecological impact of an invasive fish

AbstractAimThe way in which habitat heterogeneity and predator density affect predator–prey dynamics, space use and prey risk are understudied aspects of foraging ecology, particularly for invasive species. Likewise, how an invasive species’ impact scales with its abundance is poorly understood. We used a model invasive species—lionfish (Pterois volitans)—to understand emergent multiple predator effects and influences of habitat heterogeneity on consumption rate and prey mortality risk.LocationFlorida, USA.MethodsWe considered effects of both predator and prey abundance on density‐dependent impact. We used functional response methodology to quantify the per‐capita effect of P. volitans, assessing concomitant influences of prey refuge (3 levels) and predator density (3 levels) on predator–prey space use and predation efficiency across increasing prey densities (7 levels). We then assessed intraspecific interaction outcomes by comparing observed per‐capita effects with predicted estimates based on consumption rates of individual predators. This allowed us to detect the presence of emergent multiple predator effects (MPEs) and tease apart density‐dependent impacts.ResultsLionfish predatory impact was mediated by predator and prey density but unaffected by refugia. Despite incongruent patch preferences between predators and their prey, predator impacts were context‐independent. We also detected nonlinear scaling of impact with increasing predator abundance. Pairs of lionfish had the greatest per‐capita effect, whose cumulative impact on prey matched that expected of independently foraging predators. At the highest predator density (four fish), antagonistic multiple predator effects precipitated prey risk reduction, in which we observed the lowest per‐capita effect. Across predator abundances, prey mortality rates were inversely density‐dependent.Main conclusionsQuantifying non‐independent consumptive effects of multiple conspecific predators across levels of prey abundance can inform better prediction and understanding of invasive species' density‐dependent effects. Additionally, consideration of heterogeneity‐mediated FRs and predator–prey spatial distributions may facilitate more precise and realistic predictions of invader impact across their invaded range.

Biological Features of Neoseiulus californicus (Acari: Phytoseiidae) Feeding on Schizotetranychus oryzae (Acari: Tetranychidae) Kept on Rice Leaves

Schizotetranychus oryzae Rossi de Simons attains pest level in rice crops. This study aimed to evaluate the biological features of Neoseiulus californicus (McGregor) feeding on S. oryzae on leaves of flooded rice. We also evaluated N. californicus behavior in response to S. oryzae and conspecific cues. Thirty-two eggs were individually placed in arenas on rice leaves and fed on S. oryzae for the biological test. Three cultivars were used to test the behavior of N. californicus in response to S. oryzae and conspecific cues. The intrinsic rate of increase (rm) of the predator feeding on S. oryzae was 0.21 female/female/day. Schizotetranychus oryzae was considered a suitable prey for N. californicus under laboratory conditions. The results obtained in behavioral tests showed that N. californicus preferred laying eggs on leaves uninfested by S. oryzae and it did not show oviposition preference in arenas with conspecific predator cues. This predator was found in all rice cultivation areas in the state of Rio Grande do Sul, Brazil. Neoseiulus californicus proved to be a control agent for S. oryzae.

Emergent intraspecific multiple predator effects shape estuarine trophic dynamics across a gradient of habitat complexity

Estuarine ecosystems are characterized by heterogeneity in species assemblages and habitat complexity, so prey in these systems are often threatened by multiple predators across a mosaic of habitats. When several predator species or conspecifics co-occur, behavioral interactions between them can introduce non-independence to their predator-prey dynamics, which can alter the fate of shared prey. Habitat complexity may regulate these interactions and further impact prey survivorship. We conducted an experiment that manipulated the densities and identities of two ecologically similar estuarine-dependent predators, Red Drum (Sciaenops ocellatus) and Spotted Seatrout (Cynoscion nebulosus), within three habitat complexities. The resulting survivorships of two shared prey types were utilized to determine whether these predators are substitutable, to examine their inter- and intra-specific trophic interactions, and to investigate the impact of habitat structural complexity on their trophic dynamics. The predators differed in their prey preferences and predation pressures, indicating they are generally not substitutable. Interactions between conspecific predators were particularly important in shaping trophic dynamics, and often resulted in combined predation impacts that either enhanced or reduced the survivorship of shared prey as compared to expected values based on foraging rates of individuals. Minimal evidence of interspecific trophic interactions was detected. The observed emergent multiple predator effects differed among the habitats, and were generally intense in intermediate habitat complexity but were either intense or weak in high habitat complexity, depending on the predator combination. These results collectively indicate that prey regulation in this estuarine trophic system is highly dependent on the predator-prey assemblage and habitat context, and enhances our understanding of how multiple predators interactively shape their shared ecosystem.

Prey density and a conspecific competitor influence multiple predator effects in a crab - clam foraging system

To examine the variation of multiple predator effects and functional response caused by interaction of conspecific predators under different prey density, we established swimming crab, Portunus trituberculatus - Manila clam, Ruditapes philippinarum foraging systems in the laboratory. Specifically, we quantified predation rate, foraging behaviors, and encounter behaviors between predators under different clam density treatments. The main results were as follows: (1) The effect of clam densities on the fighting between the crab individuals leading to the changes of multiple predator effects type. Independent multiple predator effects were observed in double predator treatments under lower clam density treatments (4–8 clams 0.48 m−2). Non-independent multiple predator effects that would reduce the success rate of predator and the prey risk, occurred in double predator treatments under higher clam density treatments (10–25 clams 0.48 m−2). (2) The probability of fighting upon encounter in high clam density treatments were higher than that in low clam density treatments, and it further reduced the probability of capture upon encounter and increased the probability of consumption upon capture. In low clam density treatments, the foraging behaviors of the crabs were not significantly altered in the presence of competitor. (3) The presence of conspecific competitor did not change the type of functional response, while reducing the magnitude of it. The present study provides a foundation for future research on the relationship between predators interaction and prey population dynamic, which can be used to improve the production of crab or clam aquaculture systems.

Hunted hunters: an experimental test of the effects of predation risk on juvenile lemon shark habitat use

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 574:85-95 (2017) - DOI: https://doi.org/10.3354/meps12187 Hunted hunters: an experimental test of the effects of predation risk on juvenile lemon shark habitat use K. L. Stump1,2,*, C. J. Crooks3, M. D. Fitchett4, S. H. Gruber1,2, T. L. Guttridge2 1Department of Marine Biology and Ecology, University of Miami Rostenstiel School of Marine and Atmospheric Science, 4600 Rickenbacker Causeway, Miami, Florida 33149, USA 2Bimini Biological Field Station Foundation, 9300 SW 99th Street, Miami, Florida 33176, USA 3University of Manchester, Oxford Road, Manchester M13 9PL, UK 4Department of Marine Ecosystems and Society, University of Miami Rosenstiel School of Marine and Atmospheric Science, 4600 Rickenbacker Causeway, Miami, Florida 33149, USA *Corresponding author: kristine.stump@gmail.com ABSTRACT: Predation effects can occur either through consumption or as risk effects, which can include alterations in prey behavior to decrease encounters, detection and/or capture by predators. Perceived predation threats lead to behavioral responses which may manifest as changes in habitat use by the prey, and these effects can be significant and even greater in population-level consequences and across multiple trophic levels than consumptive effects. In Bimini, Bahamas, juvenile lemon sharks (Negaprion brevirostris, Poey 1868) use mangrove-fringed shorelines as nursery areas in part due to protection afforded from predators, namely, large conspecifics. We investigated small-scale use (on the order of meters) of artificial mangrove structure by juvenile N. brevirostris as an antipredatory response to perceived predation risk. Controlled experimental trials were conducted on semi-captive individuals to compare the degree to which sharks used artificial subtidal refugia when solitary, with a size-matched conspecific and with a potential predator (large conspecific). Test shark size and predator presence were significant drivers of artificial mangrove use. There was a negative relationship between body size and refuge use in the presence of a predator, indicating that size is an important factor influencing antipredatory behavior. Test sharks exhibited a high degree of social swimming behaviors with size-matched conspecifics, but the presence of a large conspecific predator elicited fright reponses. This study provides the first experimental evidence of the influence of intraspecific predator-prey interactions on juvenile shark habitat use and demonstrates use of subtidal structure as a habitat-specific escape tactic. KEY WORDS: Risk effects · Risk of predation · Habitat loss · Mangroves · Predator-prey interactions · Refuge Full text in pdf format PreviousNextCite this article as: Stump KL, Crooks CJ, Fitchett MD, Gruber SH, Guttridge TL (2017) Hunted hunters: an experimental test of the effects of predation risk on juvenile lemon shark habitat use. Mar Ecol Prog Ser 574:85-95. https://doi.org/10.3354/meps12187 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 574. Online publication date: July 04, 2017 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2017 Inter-Research.

Starvation and a conspecific competitor influence multiple predator effects in a swimming crab (Portunus trituberculatus) - Manila clam (Ruditapes philippinarum) foraging system

To investigate the effect of starvation (0–12days) on multiple predator effects and the mechanisms driving these effects, we established swimming crab (Portunus trituberculatus) - Manila clam (Ruditapes philippinarum) foraging systems in the laboratory. Specifically, we quantified predation rate, foraging behaviors, and encounter behaviors between predators under different foraging system treatments. The main results were as follows: (1) Changes in multiple predator effects were related to fighting between swimming crab individuals resulting from different starvation regimes. Non-independent multiple predator effects were observed that reduced the foraging success of swimming crabs in short-term starvation treatments. However, independent multiple predator effects were observed in normally fed and long-term starvation treatments, and the foraging success of swimming crabs did not change. (2) Under short-term starvation, a high probability of fighting between swimming crabs significantly increased the proportion of time spent handling clams, while the probability of consumption upon capture of clams significantly decreased. However, the foraging behaviors of swimming crabs were not significantly altered by a low probability of fighting upon encounter under no-starvation and long-term starvation. (3) The pattern of foraging time budget of swimming crabs did not change significantly in the presence of conspecific competitors under any starvation level. The present study provides a foundation for future research on the interaction of conspecific predators, which can be used to improve aquaculture systems.

Predation risk between cannibalistic aeshnid dragonflies influences their functional response on a larval salamander prey

AbstractIn size‐structured populations of predators, the threat of cannibalism can influence behavior of prey that are attempting to avoid predation by larger conspecifics, including reducing their foraging rates. Such behavioral responses subsequently release basal prey of both cannibal and non‐cannibal predators from predation risk. However, whether the non‐consumptive effects of cannibalism on conspecific predators varies with basal heterospecific prey density is relatively unexplored. I conducted a laboratory study in plastic containers to test whether cannibalism risk influenced the functional response of dragonflies while foraging on three different densities of larval salamander prey. Dragonfly predators foraged with a Type II functional response, and when exposed to cannibalism cues, per capita feeding rates were lower at high prey densities. Salamander prey mortality rates declined with increasing prey densities, but the presence of cannibalism risk did not influence this pattern. Overall, this study shows that functional response curves of predators can vary in response to whether cannibalism risk is present in their environment across a small range of prey densities. Incorporating synergistic effects of multiple processes, such as non‐consumptive risk factors and prey density, may help further elucidate the processes that structure both predator and prey population dynamics.

Subaerial naticid gastropod drilling predation by Natica tigrina on the intertidal molluscan community of Chandipur, Eastern Coast of India

Chandipur intertidal flat in eastern coast of India is a killing field. The vast stretch of intertidal habitat opens up during the low tide, and is monopolized by a single naticid species which preys extensively on intertidal taxa. The predator, Natica tigrina, wades through the soft sediments and ambushes on epi- or infaunal prey.There were reports on naticid subaerial hunting, where the workers made vivid observations, but only in few instances quantified different aspects of predation. Detailed quantitative analyses of the present study revealed that N. tigrina attacks opportunistically on all infaunal and epifaunal intertidal bivalve and gastropod prey taxa. Drilling frequencies ranged from 9.70% to 67.67% with no apparent relation with relative abundances of the taxa. High drilling frequency on conspecific predation perhaps suggested elimination of the potential competitor as well as a profitable prey. Behavioral data of predation, i.e., stereotypy of site and size of drillholes on prey shells and low prey effectiveness indicated that the predator was highly efficient.

Improving the ecological understanding of species complexes: the case of piscivory and protracted spawning in the carp gudgeon group Hypseleotris spp. (Eleotridae, Teleostei)

Species complexes are a common occurrence in freshwater fish assemblages and may often pose a challenge to the understanding of their ecology. A typical case is the `cryptic' carp gudgeon group Hypseleotris spp. in southeastern Australia, which is thought to comprise four closely related species occurring sympatrically within the Murray-Darling Basin (MDB), where flow delivery scenarios have been proposed for the management and conservation of the native fish faunas. The objective of this study was to provide a deeper insight into the occurrence of piscivory and protracted spawning seasons in Hypseleotris spp. based on six years of sampling, and to cast the findings within the broader context of interrelationships between species complexes and their ecology. It is argued that what has been so far referred to as conspecific predation (cannibalism) in Hypseleotris spp. could be explained alternatively as `congeneric' predation, or even as a combination of both. Furthermore, the presence of larvae all year round should be accounted for when assessing the effectiveness of taxon-specific water allocation programs. Better matching of taxonomy with ecology is, therefore, essential for the successful management and conservation of species complexes, and further insights may be provided through the assessment of altricial/precocial forms.

Cannibalism of an endemic island lizard (genus Gallotia)

Cannibalism is not rare among animals, and particularly in reptiles it is favored by a strong ontogenetic shift in body size and generalized carnivore habits. We looked for evidence of this behavior in a medium-sized lizard, endemic of oceanic islands (Canary Islands), with a high prevalence of a parasite transmitted by cannibalism. Conspecific predation appeared in this lizard, with a rather low incidence (0.76% of fecal pellets included conspecifics), although the analysis of a very large sample (n=11,651 pellets) indicated ontogenetic, sexual, and seasonal patterns of such predation. Only the largest individuals were cannibal, invariably males, which only depredated immature individuals, almost exclusively during the post-hatching period (summer and autumn). Together with other natural-history traits already known for the species (e.g., high density, low breeding output, large offspring), cannibalism adds further evidence that this lizard fits the island syndrome.