37,493 research outputs found
Eliciting a predatory response in the eastern corn snake (Pantherophis guttatus) using live and inanimate sensory stimuli: implications for managing invasive populations
North America's Eastern corn snake (Pantherophis guttatus) has been introduced to several islands throughout the Caribbean and Australasia where it poses a significant threat to native wildlife. Invasive snake control programs often involve trapping with live bait, a practice that, as well as being costly and labour intensive, raises welfare and ethical concerns. This study assessed corn snake response to live and inanimate sensory stimuli in an attempt to inform possible future trapping of the species and the development of alternative trap lures. We exposed nine individuals to sensory cues in the form of odour, visual, vibration and combined stimuli and measured the response (rate of tongue-flick [RTF]). RTF was significantly higher in odour and combined cues treatments, and there was no significant difference in RTF between live and inanimate cues during odour treatments. Our findings suggest chemical cues are of primary importance in initiating predation and that an inanimate odour stimulus, absent of simultaneous visual and vibratory cues, is a potential low-cost alternative trap lure for the control of invasive corn snake populations
Multiple Trophic Levels in Soft-Bottom Communities
In order to assess the general applicability of recent field experiments with predatory infauna, we searched the literature and found 48 well-documented cases of infaunal consumption by such predators. In 63 % of the cases detailed enough to make a determination, the predators ate other predators. Multiple trophic levels within the infauna are probably a common feature of many soft-bottom communities
Ants biting amphibians: A review and new observations
Antagonistic interactions between insects and amphibians are the subject of many scientific articles, mostly concerning amphibian predation on insect, but many fewer examples exist of the opposite situation. In this article we review available information from the literature and add our own observations collected during amphibian pitfall trap monitoring in 2012–2016 in Western Poland, as well as discuss potential conservation implications of observed behavior. We identified a total of 29 cases involving 94 individual ants attacking four species of Anura, Rana temporaria, Pelophylax esculentus complex, Bufo bufo, and Pelobates fuscus, and biting their back, cloaca, armpits, or hind legs. Bites were inflicted by three ant species: Myrmica rubra, Lasius fuliginosus, and Formica polyctena. The number of ants found on an amphibian was positively and significantly correlated with its body length. To date, direct damage by ants on amphibians was reported mainly from the tropics in general predation accident. However, as we document here, it is probably a more common phenomenon, especially in some ecological traps or during pitfall trapping, which is a common method to mitigate road mortality of frogs and toads
Effects of Red-Backed Salamanders on Ecosystem Functions
Ecosystems provide a vast array of services for human societies, but understanding how various organisms contribute to the functions that maintain these services remains an important ecological challenge. Predators can affect ecosystem functions through a combination of top-down trophic cascades and bottom-up effects on nutrient dynamics. As the most abundant vertebrate predator in many eastern US forests, woodland salamanders (Plethodon spp.) likely affect ecosystems functions. We examined the effects of red-backed salamanders (Plethodon cinereus) on a variety of forest ecosystem functions using a combined approach of large-scale salamander removals (314-m2 plots) and small-scale enclosures (2 m2) where we explicitly manipulated salamander density (0, 0.5, 1, 2, 4 m−2). In these experiments, we measured the rates of litter and wood decomposition, potential nitrogen mineralization and nitrification rates, acorn germination, and foliar insect damage on red oak seedlings. Across both experimental venues, we found no significant effect of red-backed salamanders on any of the ecosystem functions. We also found no effect of salamanders on intraguild predator abundance (carabid beetles, centipedes, spiders). Our study adds to the already conflicting evidence on effects of red-backed salamander and other amphibians on terrestrial ecosystem functions. It appears likely that the impact of terrestrial amphibians on ecosystem functions is context dependent. Future research would benefit from explicitly examining terrestrial amphibian effects on ecosystem functions under a variety of environmental conditions and in different forest types
Smelling out predators is innate in birds
The role of olfaction for predation risk assessment remains barely explored in birds, although predator chemical cues could be useful in predator detection under low visibility conditions for many bird species. We examine whether Great Tits Parus major are able to use the odour of mustelids to assess predation risk when selecting cavities for roosting. We analysed whether the response to predator chemical cues is innate and assessed whether the antipredatory response is associated with exploratory behaviour, a proxy for the personality of birds. In a choice experiment in aviaries, we offered naïve adult Great Tits of known personality two nest-boxes, one control and one experimental. The experimental nest-box had the odour of a mustelid predator or a strong new odour without biological significance, the control nest-box contained no odour. When one of the cavities contained the odour of a predator, birds avoided the use of either of the two offered nest-boxes, whereas there was no avoidance of boxes when one of the nest-boxes contained a control odour. There was no relationship with exploratory behaviour. We show that the ability to use the chemical cues of predators is innate in birds, but individual differences in the response to predator chemical cues cannot be explained by the personality of the bird.
Evolving collective behavior in an artificial ecology
Collective behavior refers to coordinated group motion, common to many animals. The dynamics of a group can be seen as a distributed model, each “animal” applying the same rule set. This study investigates the use of evolved sensory controllers to produce schooling behavior. A set of artificial creatures “live” in an artificial world with hazards and food. Each creature has a simple artificial neural network brain that controls movement in different situations. A chromosome encodes the network structure and weights, which may be combined using artificial evolution with another chromosome, if a creature should choose to mate. Prey and predators coevolve without an explicit fitness function for schooling to produce sophisticated, nondeterministic, behavior. The work highlights the role of species’ physiology in understanding behavior and the role of the environment in encouraging the development of sensory systems
Predator avoidance in extremophile fish
Extreme habitats are often characterized by reduced predation pressures, thus representing refuges for the inhabiting species. The present study was designed to investigate predator avoidance of extremophile populations of Poecilia mexicana and P. sulphuraria that either live in hydrogen sulfide-rich (sulfidic) springs or cave habitats, both of which are known to have impoverished piscine predator regimes. Focal fishes that inhabited sulfidic springs showed slightly weaker avoidance reactions when presented with several naturally occurring predatory cichlids, but strongest differences to populations from non-sulfidic habitats were found in a decreased shoaling tendency with non-predatory swordtail (Xiphophorus hellerii) females. When comparing avoidance reactions between P. mexicana from a sulfidic cave (Cueva del Azufre) and the adjacent sulfidic surface creek (El Azufre), we found only slight differences in predator avoidance, but surface fish reacted much more strongly to the non-predatory cichlid Vieja bifasciata. Our third experiment was designed to disentangle learned from innate effects of predator recognition. We compared laboratory-reared (i.e., predator-naïve) and wild-caught (i.e., predator-experienced) individuals of P. mexicana from a non-sulfidic river and found no differences in their reaction towards the presented predators. Overall, our results indicate (1) that predator avoidance is still functional in extremophile Poecilia spp. and (2) that predator recognition and avoidance reactions have a strong genetic basis
'Selfish herds' of guppies follow complex movement rules, but not when information is limited
Under the threat of predation, animals can decrease their level of risk by moving towards other individuals to form compact groups. A significant body of theoretical work has proposed multiple movement rules, varying in complexity, which might underlie this process of aggregation. However, if and how animals use these rules to form compact groups is still not well under- stood, and how environmental factors affect the use of these rules even less so. Here, we evaluate the success of different movement rules, by comparing their predictions with the movement seen when shoals of guppies ( Poecilia reticulata ) form under the threat of predation. We repeated the experiment in a turbid environment to assess how the use of the movement rules changed when visual information is reduced. During a simulated predator attack, guppies in clear water used complex rules that took multiple neighbours into account, forming compact groups. In turbid water, the difference between all rule predictions and fish movement paths increased, particularly for complex rules, and the resulting shoals were more fragmented than in clear water. We conclude that guppies are able to use complex rules to form dense aggregations, but that environmental factors can limit their ability to do so
Lead (Pb) concentrations in predatory bird livers 2010 and 2011: a Predatory Bird Monitoring Scheme (PBMS) report
The Predatory Bird Monitoring Scheme (PBMS; http://pbms.ceh.ac.uk/) is the umbrella project that encompasses the Centre for Ecology & Hydrology’s National Capability contaminant monitoring and surveillance work on avian predators. By monitoring sentinel vertebrate species, the PBMS aims to detect and quantify current and emerging chemical threats to the environment and in particular to vertebrate wildlife.
Lead (Pb) is a highly toxic metal that acts as a non-specific poison affecting all body systems and has no known biological requirement. Sources of Pb in the environment include lead mining, the refining and smelting of lead and other metals, the manufacture and use of alkyl lead fuel additives, and the use of lead ammunition.
The present study is the first two years of a PBMS monitoring programme to quantify the scale of exposure to [and associated risk from] Pb in predatory birds. The aim is to quantify the extent of exposure to lead [as assessed from liver residues] in two predatory bird species, the red kite (Mivus milvus) and the sparrowhawk (Accipiter nisus). The red kite is a scavenger and, as such, is particularly at risk from consumption of Pb ammunition in unretrieved game. Sparrowhawks prey predominantly upon live passerine birds that are unlikely to be shot in the UK; likely sources of exposure are diffuse Pb contamination although some individuals may also be exposed to Pb particles ingested by their prey. We also examined the liver Pb isotope ratios in to explore whether they can be used to ascribe likely sources of any Pb detected in the birds.
Red kites had significantly higher Pb concentration than those measured in sparrowhawks but the majority of sparrowhawks and all the red kites had liver Pb concentrations below those thought to cause clinical and sub-clinical adverse effects in Falconiforme species. There was overlap in the liver Pb isotope ratios of red kites and sparrowhawks yet there was evidence of separation between the two species. There was also evidence of overlap with the isotope signature for coal and for Pb shot but the isotope signatures in the bird livers were distinct from
that of petrol Pb. The Pb isotope pattern observed in the red kites and sparrowhawks in the current study may reflect the fact that liver Pb concentrations were low in the small sample of birds that were analysed and may have been a result of exposure to low-level, diffuse contamination.birds.
Red kites had significantly higher Pb concentration than those measured in sparrowhawks but
the majority of sparrowhawks and all the red kites had liver Pb concentrations below those
thought to cause clinical and sub-clinical adverse effects in Falconiforme species. There was
overlap in the liver Pb isotope ratios of red kites and sparrowhawks yet there was evidence of
separation between the two species. There was also evidence of overlap with the isotope
signature for coal and for Pb shot but the isotope signatures in the bird livers were distinct from
that of petrol Pb. The Pb isotope pattern observed in the red kites and sparrowhawks in the
current study may reflect the fact that liver Pb concentrations were low in the small sample of
birds that were analysed and may have been a result of exposure to low-level, diffuse
contamination
Kohalike ja invasiivsete röövtoiduliste suurselgrootute elupaigakasutus ja toitumissuhted Läänemere põhjaosas
Väitekirja elektrooniline versioon ei sisalda publikatsiooneRöövtoidulised suurselgrootud, peamiselt vähilaadsed, on rannikumere toitumisvõrgustikes oluliseks lüliks põhjaelustiku ja kalade vahel ning ühtlasi nad reguleerivad väiksemate selgrootute arvukust. Läänemere põhjaosas elas selle rühma esindajaid seni ainult kaks liiki – läänemere krevett (Palaemon adspersus) ja põhjamere garneel (Crangon crangon). Hiljuti lisandusid neile kohalikele liikidele kaks võõrliiki – elegantne krevett (Palaemon elegans) ja rändkrabi (Rhithropanopeus harrisii). Kohalike ja võõrliikidest röövtoiduliste suurselgrootute leviku, elupaigaeelistuste ja toitumise uurimiseks kasutati olemasolevaid põhjaelustiku leviku andmeid, spetsiaalselt uuritavatele liikidele suunatud proovide kogumist loodusest ja laborikatseid, kus rakendati muuhulgas loomade raadiomärgistamist. Võõrliigist kreveti levik oli ulatuslikum kui kohalike krevettide levik. Võõrliik oli kohalike krevettidega võrreldes enam seotud elupaikadega, millele on iseloomulikud etrofeerumise tunnused (kõrge toitainete kontsentratsioon, lühiealiste niitjate vetikate suur hulk). Krevettide toitumisuuringud näitasid, et uuritud Palaemon liikide toitumisintensiivsus ja toidu kooseis ei erinenud. Seega on kohaliku ja võõrkreveti roll rannikumere toiduvõrkudes sarnane, ent võõrliik võib troofilisi suhteid ümber kujundada piirkondades, kus kohalikud krevetid puuduvad. Kõige kitsama elupaigakasutusega oli põhjamere garneel ja Palaemon liikidest oli võõrliigi P. elegans spetsialiseerumise tase mõnevõrra kõrgem kui kohalikul liigil. R. harrisii eelistas põisadruga (Fucus vesiculosus) elupaika mis viitab sellele, et põisadruga elupaik pakub krabile aastaringset stabiilset elupaika ja et mitmekesine põhjakooslus võib saada seetõttu krabidest oluliselt mõjutatud. Doktoritöö tulemused näitasid, et elupaikade iseloom ja seisund mõjutab kohalike ja võõrliikide levikumustreid ning võõrliikidest selgrootute kiskjate saabumine ja kiire levila laienemine Läänemere põhjaosas toovad kaasa täiesti uue ökoloogilise funktsiooni (suuremõõtmeline kiskja) või juba varem regionaalselt esinenud funktsiooni leviku piirkondadesse, kus see varem puudus.Decapod crustaceans, such as crabs and shrimps play an important role in coastal ecosystems as they prey on small benthic invertebrates and at the same time they are an important food item for fishes. Until recently, this group of macroinvertebrates consisted of only a few species in the northern Baltic Sea, including only two species of native shrimps – Crangon crangon and Palaemon adspersus. However, very recently two non-native crustacean predators arrived – the shrimp Palaemon elegans and the crab Rhithropanopeus harrisii. Data from available databases were used together with field sampling and laboratory experiments (incl. radio frequency positioning technology) to describe the geographical distribution, habitat selection, and feeding of native and invasive predatory crustaceans in the coastal areas of the northern Baltic Sea. The distribution of the non-native P. elegans was wider than that of native species. P. elegans was associated with lower salinity, higher concentrations of nutrients and higher proportions of ephemeral filamentous algae, relative to P. adspersus. According to results of the experiment on feeding activity, P. elegans performs a similar role in the coastal food web as the native congener, although it may rearrange trophic interactions and introduce new ecological function in the most eutrophicated areas previously lacking any native shrimp. Among the studied shrimps, C. crangon had the highest habitat specialization. The non-native P. elegans showed slightly higher habitat specialization compared to the native P. adspersus. The invasive crab R. harrisii preferred habitats with bladder wrack where the diverse native community may become heavily impacted by this novel large-bodied predator. This thesis showed that the successful establishment of non-native predatory invertebrates can introduce new ecological functions (large-bodied predators) or considerably strengthen already existed ones, while the heterogeneity of habitats has varying effects on the distribution patterns of native and invasive species
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