Significant Predation Pressure Research Articles

Great cormorant (Phalacrocorax carbo sinensis) predation on adult anadromous brown trout (Salmo trutta)

AbstractThe increase in abundance of great cormorants (Phalacrocorax carbo sinensis) over the last decades has caused concern for the sustainability of fish populations. Cormorants are opportunistic piscivorous birds that eat fish from a wide range of species and sizes, in marine, lacustrine and riverine habitats. It has been documented that juvenile salmonids are under significant predation pressure by great cormorants, although knowledge on the predation of adult salmonids by cormorants is limited. In this study, adult anadromous brown trout (Salmo trutta) were tagged over multiple years with PIT tags during their spawning migration in a Danish lowland river. Two nearby cormorant colonies were subsequently scanned for PIT tags to estimate predation rate. It was estimated that by minimum 15.4% of tagged adult sea trout were predated by cormorants. The majority of the individuals were predated in the river, and females were more likely to be predated than males. Moreover, length had a significant effect on predation probability: individuals between 35 and 43 cm had the highest likelihood to be predated, while smaller and larger individuals were less likely to be predated. Our findings challenge the assumption that cormorants do not prey on reproductively mature salmonids. Furthermore, predation of mature individuals may have implications for the recruitment and sustainability of the population.

Records of drill holes and repair scars on Rectithyris subdepressa (Brachiopoda) from the Maastrichtian Kallankurichchi Formation, India

In the post-Paleozoic communities, brachiopods are generally thought to be less attractive prey to predators than bivalves. However, recent studies have documented significant predation pressure on brachiopods throughout the Mesozoic and Cenozoic. The present study is aimed to document predation pressure on the Maastrichtian Rectithyris subdepressa from the Kallankurichchi Formation of the Cauvery Basin, India. While drilling intensity is a direct measure, repair scar frequency measures failed, non-lethal attacks. A drilling intensity of 7% and repair scar intensity of 4% is observed in the present study. These results, along with the stereotype of predatory behavior, such as the preference of size and location of the attack, indicate that both drilling and durophagous predators preyed upon Rectithyris subdepressa and the attacks are not accidental by nature. Although both predatory drill holes and repair scars could be successfully identified, specific groups could not be identified as the predators responsible for these attacks. While previous studies suggested a comparatively lower predation pressure on brachiopods than sympatric bivalves, brachiopods are the only drilled taxa in the Kallankurichchi Formation. While bivalves are the most abundant component, the large size and thicker shell of the epifaunal bivalves may explain the absence of drilling predation on the bivalves.

Microbial predation accelerates granulation and modulates microbial community composition

BackgroundBacterial communities are responsible for biological nutrient removal and flocculation in engineered systems such as activated floccular sludge. Predators such as bacteriophage and protozoa exert significant predation pressure and cause bacterial mortality within these communities. However, the roles of bacteriophage and protozoan predation in impacting granulation process remain limited. Recent studies hypothesised that protozoa, particularly sessile ciliates, could have an important role in granulation as these ciliates were often observed in high abundance on surfaces of granules. Bacteriophages were hypothesized to contribute to granular stability through bacteriophage-mediated extracellular DNA release by lysing bacterial cells. This current study investigated the bacteriophage and protozoan communities throughout the granulation process. In addition, the importance of protozoan predation during granulation was also determined through chemical killing of protozoa in the floccular sludge.ResultsFour independent bioreactors seeded with activated floccular sludge were operated for aerobic granulation for 11 weeks. Changes in the phage, protozoa and bacterial communities were characterized throughout the granulation process. The filamentous phage, Inoviridae, increased in abundance at the initiation phase of granulation. However, the abundance shifted towards lytic phages during the maturation phase. In contrast, the abundance and diversity of protozoa decreased initially, possibly due to the reduction in settling time and subsequent washout. Upon the formation of granules, ciliated protozoa from the class Oligohymenophorea were the dominant group of protozoa based on metacommunity analysis. These protozoa had a strong, positive-correlation with the initial formation of compact aggregates prior to granule development. Furthermore, chemical inhibition of these ciliates in the floccular sludge delayed the initiation of granule formation. Analysis of the bacterial communities in the thiram treated sludge demonstrated that the recovery of ‘Candidatus Accumulibacter’ was positively correlated with the formation of compact aggregates and granules.ConclusionPredation by bacteriophage and protozoa were positively correlated with the formation of aerobic granules. Increases in Inoviridae abundance suggested that filamentous phages may promote the structural formation of granules. Initiation of granules formation was delayed due to an absence of protozoa after chemical treatment. The presence of ‘Candidatus Accumulibacter’ was necessary for the formation of granules in the absence of protozoa.

Video surveillance reveals a community of largely nocturnal Danaus plexippus (L.) egg predators

Monarch butterfly (Danaus plexippus L.) declines in eastern North America have prompted milkweed host plant restoration efforts in non-agricultural grasslands. However, grasslands harbor predator communities that exert high predation pressure on monarch eggs and larvae. While diurnal monarch predators are relatively well known, no studies have investigated the contribution of nocturnal monarch predators. We used video cameras to monitor sentinel monarch eggs and fourth instars on milkweed in southern Michigan to identify predators and determine if nocturnally-active species impose significant predation pressure. We observed ten arthropod taxa consuming monarch eggs and larvae, with 74% of egg predation events occurring nocturnally. Taxa observed attacking monarch eggs included European earwigs (Forficula auricularia L.), tree crickets (Oecanthus sp.), lacewing larvae (Neuroptera), plant bugs (Miridae), small milkweed bugs (Lygaeus kalmii Stal), ants (Formicidae), spiders (Araneae: Salticidae and other spp.), harvestmen (Opiliones), and velvet mites (Trombidiformes: Trombidiidae). Larvae were attacked by ground beetles (Calleida sp.), jumping spiders (Araneae: Salticidae), and spined soldier bugs (Podisus maculiventris Say). Our findings provide important information about monarch predator–prey interactions that could be used to develop strategies to conserve monarchs through reducing predation on early life stages.

Predation on Endangered Species by Cats in the Northern Forests of Okinawa-Jima Island, Japan

Okinawa-jima Island is a part of the Ryukyu Archipelago, Japan and some endemic animals occur. Many of the native animals are limited to the northern part of this island. Here, we examined the predation effect by domestic cats on native species in the northern part of the island. Route surveys were conducted from September 2017 to February 2018, and cats were captured from 2013 to 2018. In total 60 scats (36 by route surveys and 24 from seven captured cats) were collected. At least 16 animal species were found in domestic cats' scats. Traces of endemic Okinawa spiny rats (Tokudaia muenninki) were the most frequently found from scats collected by route surveys (61.1% in total; 71.4% in the core route, set around the distribution area of Okinawa spiny rats), followed by Ryukyu long-furred rats (Diplothrix legata) (16.7% in total; 21.4% in the core route). Our results showed that domestic cats might exert a significant predation pressure on native endemic vertebrates, especially on Okinawa spiny rats.

Dolphin predation pressure on pelagic and demersal fish in the northwestern Mediterranean Sea

Sardine Sardina pilchardus, anchovy Engraulis encrasicolus and European hake Merluccius merluccius represent a significant part of the commercial landings in the Gulf of Lions (northwestern Mediterranean Sea). However, their stocks have shown severe declines during the last decades due to fishing pressure and/or environmental changes. The aim of this study was to estimate the current predation pressure of bottlenose dolphins Tursiops truncatus and striped dolphins Stenella coeruleoalba - which are abundant in the area-on sardine, anchovy and hake. To do so, we developed an original approach based on several data sets and models (aerial surveys, stomach contents, allometric and stock assessment models) and Monte Carlo simulations to incorporate various sources of uncertainty due to data limitations. Despite the uncertainties, the results showed that dolphin predation pressure on sardine and anchovy was extremely low in the Gulf of Lions (all simulations <0.5 % of the available stock), indicating little impact of dolphins on those populations. However, significant predation pressure on hake (median value: 23 %) was detected, a value which might have doubled in the last 30 yr because of hake overfishing. Overexploitation has thus reinforced the natural mortality of hake due to dolphin predation, but this predation pressure remains 2 to 3 times lower than that exerted by fisheries.

Why the damselfish Chromis chromis is a key species in the Mediterranean rocky littoral-a quantitative perspective.

The damselfish Chromis chromis is typically the most abundant fish species in the rocky littoral environment of the Mediterranean Sea, where it feeds in huge shoals on incoming zooplankton and rests near the seabed each night. Research has shown that large populations of C. chromis play a fundamental role by transferring carbon, nitrogen and phosphorus directly from the pelagic system to the littoral in the form of solid and liquid wastes and therefore that this species acts as a vital conduit for nutrients. In addition, C. chromis represents a major prey item for predatory fish and seabirds, it has been shown to exert significant predation pressure on coastal zooplankton populations, but it is also a major consumer of fish eggs and hence may have a strong influence on the dynamics of other fish species. In this review paper the contention is that C. chromis represents a key species in the Mediterranean Sea rocky littoral. This view is supported by quantitative evidence that has been amassed over a number of years, but is collated here for the first time. Chromis chromis is of only minor importance to commercial fisheries (it is usually discarded), but trends in population abundance of this species can be indicative of levels of fishing pressure on other commercial species. It has been demonstrated that where predator numbers are able to recover from intensive fishing (e.g.in marine protected areas; MPAs), this is often mirrored by lower densities of C. chromis. Several papers have championed C. chromis as a possible indicator species for human disturbance. As well as being directly and indirectly affected by fishing, the species is also sensitive to a number of other anthropogenic pressures, most notably poor water quality and noise pollution.

Experimental evaluation of the effects of the novel predators, round goby and mud crab on benthic invertebrates in the Gulf of Riga, Baltic Sea

The number of non-indigenous aquatic species (NIS) has rapidly increased globally. The majority of published evidence on the effects of NIS on local communities is from single species studies in which the interactive effects of NIS are not considered. Here we present experimental evidence of separate and interactive effects of two widespread non-indigenous benthic predators, the round goby (Neogobius melanostomus) and the North American mud crab (Rhithropanopeus harrisii) on benthic invertebrate communities in a shallow coastal ecosystem of the Gulf of Riga, the Baltic Sea. The two species have recently colonized multiple sub-basins of the Baltic Sea and due to their rapid range expansion, increasing densities and local functional novelty, they are expected to have strong separate or interactive effects on native communities. Our laboratory experiment demonstrated that round goby and mud crab exerted a significant predation pressure on different benthic invertebrate species and the effects of the studied predators were largely independent. Predation was stronger at higher temperature compared with low temperature treatment. Among the studied invertebrate species gammarid amphipods were consumed the most. Interestingly, round goby did not prey on the mud crabs despite a large size difference of the studied predators.

An Exceptionally Preserved Three-Dimensional Armored Dinosaur Reveals Insights into Coloration and Cretaceous Predator-Prey Dynamics

Predator-prey dynamics are an important evolutionary driver of escalating predation mode and efficiency, and commensurate responses of prey [1-3]. Among these strategies, camouflage is important for visual concealment, with countershading the most universally observed [4-6]. Extant terrestrial herbivores free of significant predation pressure, due to large size or isolation, do not exhibit countershading. Modern predator-prey dynamics may not be directly applicable to those ofthe Mesozoic due to the dominance of very large,visually oriented theropod dinosaurs [7]. Despite thyreophoran dinosaurs' possessing extensive dermal armor, some of the most extreme examples of anti-predator structures [8, 9], little direct evidence of predation on these and other dinosaur megaherbivores has been documented. Here we describe a new, exquisitely three-dimensionally preserved nodosaurid ankylosaur, Borealopelta markmitchelli gen. et sp. nov., from the Early Cretaceous of Alberta, which preserves integumentary structures as organic layers, including continuous fields of epidermal scales and intact horn sheaths capping the body armor. We identify melanin in the organic residues through mass spectroscopic analyses and observe lighter pigmentation of thelarge parascapular spines, consistent with display, and a pattern of countershading across the body. With an estimated body mass exceeding 1,300kg, B.markmitchelli was much larger than modern terrestrial mammals that either are countershaded or experience significant predation pressure as adults. Presence of countershading suggests predation pressure strong enough to select for concealment in this megaherbivore despite possession of massive dorsal and lateral armor, illustrating a significant dichotomy between Mesozoic predator-prey dynamics and those of modern terrestrial systems.

Insights of Phage-Host Interaction in Hypersaline Ecosystem through Metagenomics Analyses.

Bacteriophages, as the most abundant biological entities on Earth, place significant predation pressure on their hosts. This pressure plays a critical role in the evolution, diversity, and abundance of bacteria. In addition, phages modulate the genetic diversity of prokaryotic communities through the transfer of auxiliary metabolic genes. Various studies have been conducted in diverse ecosystems to understand phage-host interactions and their effects on prokaryote metabolism and community composition. However, hypersaline environments remain among the least studied ecosystems and the interaction between the phages and prokaryotes in these habitats is poorly understood. This study begins to fill this knowledge gap by analyzing bacteriophage-host interactions in the Great Salt Lake, the largest prehistoric hypersaline lake in the Western Hemisphere. Our metagenomics analyses allowed us to comprehensively identify the bacterial and phage communities with Proteobacteria, Firmicutes, and Bacteroidetes as the most dominant bacterial species and Siphoviridae, Myoviridae, and Podoviridae as the most dominant viral families found in the metagenomic sequences. We also characterized interactions between the phage and prokaryotic communities of Great Salt Lake and determined how these interactions possibly influence the community diversity, structure, and biogeochemical cycles. In addition, presence of prophages and their interaction with the prokaryotic host was studied and showed the possibility of prophage induction and subsequent infection of prokaryotic community present in the Great Salt Lake environment under different environmental stress factors. We found that carbon cycle was the most susceptible nutrient cycling pathways to prophage induction in the presence of environmental stresses. This study gives an enhanced snapshot of phage and prokaryote abundance and diversity as well as their interactions in a hypersaline complex ecosystem, which can pave the way for further research studies.

High fecundity and predation pressure of the invasive Gammarus tigrinus cause decline of indigenous gammarids

The North American amphipod Gammarus tigrinus is one of the most aggressive invaders recently expanding its distribution in the European waters. The species was detected in the north-eastern Baltic Sea in 2003 and has rapidly expanded its distribution ever since. This invasive amphipod has been notably successful in shallow, soft and mixed bottom habitats becoming one of the most abundant gammarid colonizing such environments. This study carried out two experiments: (1) an outdoor aquarium experiment to assess interspecific competition among the invasive G. tigrinus and the native Gammarus duebeni and compare their reproductive potential, and (2) an in situ meshbag experiment to determine the effect of adult G. tigrinus and native gammarids on juvenile gammarid amphipods. These demonstrated that the adult G. tigrinus had no effects on the adult G. duebeni; however, the invasive amphipod had higher reproductive potential compared to the native species such as G. duebeni. Moreover, almost all adult gammarids exerted a significant predation pressure on juvenile amphipods. Thus, the combined effect of predation on juvenile amphipods and large brood production of G. tigrinus could be plausible explanations describing increased abundance of G. tigrinus and decrease of local gammarid populations in the north-eastern Baltic Sea but plausibly in similar shallow water habitats in other seas.

Role of eutrophication in structuring planktonic communities in the presence of the ctenophore Mnemiopsis leidyi

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 510:151-165 (2014) - DOI: https://doi.org/10.3354/meps10900 Role of eutrophication in structuring planktonic communities in the presence of the ctenophore Mnemiopsis leidyi Marianne E. McNamara1,2,*, Darcy J. Lonsdale1, Robert M. Cerrato1 1School of Marine and Atmospheric Science, Stony Brook University, Stony Brook, NY 11794-5000, USA 2Biology Department, Suffolk County Community College, Selden, NY 11784, USA *Corresponding author: mcnamam@sunysuffolk.edu ABSTRACT: Increasing evidence implicates anthropogenic activities with recently documented shifts in the abundance and seasonal distribution of gelatinous zooplankton in coastal waters. The ctenophore Mnemiopsis leidyi occurs in mid-Atlantic estuaries in the USA where seasonal blooms occur earlier and in greater magnitude than those studied decades ago. Large densities of adult M. leidyi exert significant predation pressure on mesozooplankton, potentially influencing microplankton abundance and composition. Field-based mesocosm experiments were conducted to examine the individual and interactive roles of ctenophore predation and nutrient loading on the microplankton community using historic and recent abundances of M. leidyi in Great South Bay, New York, USA. High (recent) abundances of M. leidyi exposed to eutrophic conditions influenced plankton community structure in a way that was distinctly different from when the processes occurred separately or under low (historic) abundances. Microplanktonic ciliates exhibited an order of magnitude increase in tanks receiving either nutrient or ctenophore amendments, but increased by 2 orders of magnitude in treatments receiving both ctenophore and nutrient additions. Furthermore, ctenophores recovered from nutrient treatments produced nearly 3 times as many eggs than those reclaimed from ctenophore-only treatments, suggesting that nutrient enrichment enhances fecundity of M. leidyi. Since ciliates are an important prey item for developing M. leidyi, the combined bottom-up and top-down influences of eutrophication and ctenophore predation, respectively, on microplankton may help explain recently documented shifts in the population dynamics of M. leidyi in mid-Atlantic estuaries. KEY WORDS: Mesocosm · Ciliates · Trophic cascade · Mesozooplankton · Nutrient enrichment · Great South Bay Full text in pdf format PreviousNextCite this article as: McNamara ME, Lonsdale DJ, Cerrato RM (2014) Role of eutrophication in structuring planktonic communities in the presence of the ctenophore Mnemiopsis leidyi . Mar Ecol Prog Ser 510:151-165. https://doi.org/10.3354/meps10900 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 510. Online publication date: September 09, 2014 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2014 Inter-Research.

Myctophid feeding ecology and carbon transport along the northern Mid-Atlantic Ridge

Myctophids are among the most abundant fishes in the world׳s ocean and occupy a key position in marine pelagic food webs. Through their significant diel vertical migrations and metabolism they also have the potential to be a significant contributor to carbon export. We investigated the feeding ecology and contribution to organic carbon export by three myctophid species, Benthosema glaciale, Protomyctophum arcticum, and Hygophum hygomii, from a structurally and ecologically unique ecosystem- the Mid-Atlantic Ridge (MAR). Similar to the results of previous studies, the diet of these fishes was primarily copepods and euphausiids, however, gelatinous zooplankton was identified in the diet of B. glaciale for the first time. Ridge section and time of day were significant explanatory variables in the diet of B. glaciale as determined by canonical correspondence analysis, while depth was the only significant explanatory variable in the diet of P. arcticum. Daily consumption by MAR myctophids was less than 1% of dry body weight per day and resulted in the removal of less than 1% of zooplankton biomass daily. Although lower than previous estimates of carbon transport by myctophids and zooplankton in other areas, MAR myctophid active transport by diel vertical migration was equivalent to up to 8% of sinking particulate organic carbon in the North Atlantic. While highly abundant, myctophids do not impart significant predation pressure on MAR zooplankton, and play a modest role in the active transport of carbon from surface waters.

Clonal diversity and turnover in an overwinteringDaphnia pulexpopulation, and the effect of fish predation

SummaryDaphniaare key species in lake ecosystems and are a model system in ecology. Their ecological success is very much due to their dual reproductive mode: females reproduce parthenogenetically when environmental conditions are favourable but switch to sexual reproduction and resting egg production in unfavourable conditions such as winter. Phases of clonal reproduction lower the overall genotypic diversity ofDaphniapopulations due to the random loss of genotypes. During phases of sexual reproduction, new genotypes enhance the genotypic variability of the population and compensate for the loss of clonal lineages.We hypothesised that clonal diversity should be low during the winter months due to high mortality rates (clonal erosion) but will be restored in the spring most likely from the resting egg bank. To test this hypothesis, we investigated the clonal composition of aDaphnia pulexpopulation in a small mesotrophic lake in Norway.Daphniawere sampled every month from September 2007 to September 2010, andc. 60 individuals per month were genotyped using 11 microsatellite markers. Marker resolution was high, and 582 different genotypes could be detected in the 936 individuals analysed.An unexpected complication for the study was the illegal introduction of planktivorous fish into the lake between autumn 2006 and spring 2007. This led to significant predation pressure on theD. pulexpopulation and shifted the cladoceran community to smaller species. However, while theD. pulexpopulation density declined severely over the study years, the overall genotypic variability increased. We observed very high turnover rates, with many clones being present for only a single month. Nevertheless, and as expected, genotypic diversity was higher during summer and lower during winter, and some parthenogenetic individuals seemed to be able to survive the winter. The large majority of new genotypes came from the resting egg bank.We conclude that, due to the new predation pressure, the resting egg bank has become much more important in restocking genotypic diversity as well as forD. pulexabundance. However, despite the buffering capacities of the resting egg bank, the predation pressure will most likely lead to the extinction ofD. pulexin Lake Myravatn.

Dietary success of a ‘new’ key fish in an overfished ecosystem: evidence from fatty acid and stable isotope signatures

The bearded goby Sufflogobius bibarbatus has become a key component of the pelagic food web off Namibia following the crash in pelagic fish populations during the 1970s, and its bio- mass is increasing despite significant predation pressure and apparent life-history constraints. The integrated feeding of the bearded goby was studied from samples collected during April 2008, using stable isotope ratios (δ 13 C, δ 15 N, δ 34 S) and fatty acids, to resolve conflict amongst previous dietary studies based on gut-content analysis and to understand how diet could influence its success within the region. Isotopes of carbon and nitrogen suggest that the now abundant jellyfish could contribute up to 74% of the diet, and δ 34 S signatures indicate that the diatom- and bacteria-rich sulphidic sedi- ments on the central shelf may contribute around 15% to the diet. Fatty acid analyses provided sup- port for sulphur bacterial and jellyfish-feeding amongst gobies, and further suggest that small gobies fed more on zooplankton while large gobies fed more on sedimented diatoms. Both data sets suggest that ontogenetic changes in diet were linked to changes in habitat: pelagic when small, more demersal when large. The study highlights the value of using multiple tracers in trophic studies and indicates that the dietary flexibility of the bearded goby, in conjunction with its behaviour and physiology, likely contributes to its success within the northern Benguela ecosystem.

Site fidelity and sex-specific migration in a mobile apex predator: implications for conservation and ecosystem dynamics

Combining movement behaviour with other ecological information of predators and their prey is essential for an adequate understanding of ecosystem dynamics. The movement patterns of broadnose sevengill sharks, Notorynchus cepedianus, were monitored with acoustic and satellite technology in coastal areas of southeast Tasmania, Australia. Individuals were tagged in two habitats (Norfolk Bay and the Derwent Estuary) for which we had ecological information such as diet, population structure and abundance. Notorynchus cepedianus showed seasonal site fidelity in the use of the coastal habitats. The general pattern was for sharks to exit coastal areas over winter and females to return the following spring and males in summer. Their movement into these coastal areas coincided with high seasonal abundance of their known prey species during summer, suggesting feeding site fidelity. Individuals tagged in two coastal areas showed low spatial and dietary overlap, suggesting localized site fidelity and fine spatial scale resource partitioning. This has rarely been reported for large mobile predators. Both satellite and acoustic methods showed that males make northerly migrations during winter to distances of at least 1000 km. The combined use of tracking, diet and abundance information demonstrated that N. cepedianus are likely to exert significant predation pressure on prey inhabiting these areas during summer. Overall, this study highlights the benefit of complementing movement data with other ecological information to understand the habitat use of large mobile predators and their potential influences on ecosystem structure and function.

Captive-reared burrowing owls show higher site-affinity, survival, and reproductive performance when reintroduced using a soft-release

A remaining challenge for animal reintroductions is how best to aid individuals transitioning from captivity into the wild. We tested two techniques – ‘soft’ vs. ‘hard’ release – in a 7-year study on endangered Western burrowing owls ( Athene cunicularia hypugaea) in British Columbia, Canada. Traditionally, captive-reared yearling adults were released into the wild, as pairs, directly from artificial burrows (hard-release). Only 46% of 201 owls released in this way (2001–2004) stayed at release sites. To test for improved success, soft-releases were performed in the same manner as concurrent hard-releases (2005–2007), except above-ground enclosures confined each soft-release pair to the vicinity of their burrow for 2 weeks before complete release. Of 140 soft-released owls, 86% stayed at release sites; whereas, 66% of 100 hard-released owls stayed. Breeding-season survival was 70% for soft-released owls vs. 50% for hard-released owls. On average, soft-released owls produced 50% more fledglings than concurrently hard-released owls. Post-fledging survival was 69% and first-year return rate was 7.0% for fledglings from soft-released parents, compared to 50% and 4.0% for fledglings from hard-release parents. Ultimately, 0.17 offspring were recruited into the local wild breeding population per soft-released pair, compared to 0.05 local recruits per hard-released pair. We recommend that enclosure-based soft-releases be used for reintroduction of burrowing owls in British Columbia and elsewhere in North America. We encourage other tests for improved release success with soft-releases, particularly for species with a high tendency for dispersal or those likely to experience significant predation pressure.

Behavioral types as predictors of survival in Trinidadian guppies (Poecilia reticulata)

Studies of the fitness consequences of behavioral types often focus on isolated behaviors and ignore potential across-context correlations that may affect fitness. This approach leads to heterogeneous results across studies because correlations themselves may be adaptive in populations under significant predation pressure. We quantified suites of behaviors in 4 different contexts and identified a consistent behavioral syndrome in a population of Trinidadian guppies (Poecilia reticulata). We then measured fitness effects of the correlated behaviors that made up this syndrome and found that more active, bold, and exploratory individuals survived longer when exposed to a predator. Behavioral syndromes may, therefore, be advantageous in populations under significant predation risk if an individual's behavior in the presence of a predator is an honest signal of escape abilities. Interestingly, we also found a significant effect of the individual cichlids (Aequidens pulcher) used as predators in our experiments. We suggest that future studies should test whether interactions between predator behavior and prey behavioral types maintain behavioral variation. Copyright 2010, Oxford University Press.

Does Experimentally Induced Conspicuous Coloration Increase Risk of Predation and Conspecific Aggression in First-Year Collared Lizard Males?

Abstract I used paint to manipulate the coloration of first-year collared lizard males in the field to test whether conspicuous coloration increases risk of predation and/or aggression from dominant same-sex conspecifics, or resulted in decreased activity as a consequence of either or both increased attention from predators or socially dominant conspecifics. First-year collared lizard males are a good system for this study because their coloration is less developed than that of older males, they may suffer significant predation pressure, and instead of defending territories, they use stealthy tactics to avoid aggression from older socially-dominant males. To test these potential costs, I enhanced the coloration of first-year males in a conspicuous group by painting them similar to older territorial males, used brown paint similar to that of conspecific females to alter coloration in an inconspicuous group, and painted a control group with water. I then recorded census and focal observation data on these m...

Differential impact of adults and nymphs of a generalist predator on an exotic invasive pest demonstrated by molecular gut-content analysis

Generalist predators have the capacity to regulate herbivore populations through a variety of mechanisms, but food webs are complex and defining the strength of trophic linkages can be difficult. Molecular gut-content analysis has revolutionized our understanding of these systems. Utilizing this technology, we examined the structure of a soybean food web, identified the potential for adult and immature Orius insidiosus (Hemiptera: Anthocoridae) to suppress Aphis glycines (Hemiptera: Aphididae), and tested the hypotheses that foraging behaviour would vary between life stages, but that both adults and immatures would exert significant predation pressure upon this invasive pest. We also identified the strength of trophic pathways with two additional food items: an alternative prey item, Neohydatothrips variabilis (Thysanoptera: Thripidae), and an intraguild predator, Harmonia axyridis (Coleoptera: Coccinellidae). A. glycines constituted a greater proportion of the diet of immature O. insidiosus, but N. variabilis DNA was found in greater frequency in adults. However, both life stages were important early-season predators of this invasive pest, a phenomenon predicted as having the greatest impact on herbivore population dynamics and establishment success. No adult O. insidiosus screened positive for H. axyridis DNA, but a low proportion (2.5%) of immature individuals contained DNA of this intraguild predator, thus indicating the existence of this trophic pathway, albeit a relatively minor one in the context of biological control. Interestingly, approximately two-thirds of predators contained no detectable prey and fewer than 3% contained more than one prey item, suggesting the possibility for food limitation in the field. This research implicates O. insidiosus as a valuable natural enemy for the suppression of early-season A. glycines populations.