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Bats are voracious predators of insects, and many insects have ears sensitive to the high-frequency echolocation calls of bats. Eared insects show a variety of defences when they detect bat echolocation calls. Professor Brock Fenton was an early contributor to the field of bat-insect interactions, inspiring many students to pursue investigations that have advanced our understanding of the relationship between predators and prey. Reflecting on the integrative nature of Dr. Fenton's research, this review highlights research on the evolutionary arms race between gleaning insectivorous bats and katydid prey. Studies on this system have enhanced the field of sensory ecology by illuminating how animal auditory systems can encode and distinguish between signals that overlap in their acoustic properties but have very different consequences for the listener (sex or death). These studies also inform us about the ecological and evolutionary selection pressures on signalers and receivers that can shape mate attraction and predator avoidance behaviour. In particular, many Neotropical katydids rely on preventative instead of reactive defences against gleaning bats, likely due to the regular presence of echolocation calls from non-gleaning bats that reduce the information content of predator cues. We conclude with suggestions for future research on these fascinating animals. Key words: biosonar, Chiroptera, echolocation, evolutionary arms race, hearing, sensory ecology, Tettigoniidae, Introduction Research on the interactions between bats and insects has a long history of integrating neurophysiological, behavioural, and ecological approaches (ter Hofstede and Ratcliffe 2016). The studies of Professor M. [...]

Common loon (Gavia immer (Brunnich, 1764)) foraging patterns and the relative importance of cisco (Coregonus artedi Lesueur, 1818) in the diets of loons were evaluated for the Whitefish Chain of Lakes, a set of coldwater cisco refuge lakes in Minnesota, USA. Environmental DNA metabarcoding of loon fecal samples detected 15 fish species. Yellow perch (Perca flavescens (Mitchill, 1814)), mimic shiner (Notropis volucellus (Cope, 1865)), and cisco were the most prominent prey detected across the study lakes. We observed a shift in fish species consumed, with increases in detections of mimic shiner and cisco DNA among loon fecal samples collected in August and September. In some locations, suitable oxythermal habitat became restricted throughout the summer, forcing cisco into surface waters, which potentially increased their vulnerability to loon predation. Conversely large foraging aggregations of loons were observed during late summer through fall at locations with ample oxythermal habitat and abundant cisco populations. We hypothesize that cisco were sought by loons as a high-calorie prey resource prior to migration. Conservation efforts directed at preserving water quality in important cisco refuge lakes are likely to benefit common loons through enhancement of both the forage base, for resident and migrating birds, and breeding habitat suitability. Key words: cisco, common loon, Coregonus artedi, diet, environmental DNA (eDNA) metabarcoding, foraging patterns, Gavia immer, Introduction Common loons (Gavia immer (Brunnich, 1764)) are facultative piscivores (Barr 1996), opportunistically foraging primarily on yellow perch (Perca flavescens (Mitchill, 1814)), sunfish species (Lepomis spp. Rafinesque, 1819), and minnows [...]

INTRODUCTION The life history of most Arctic and sub-Arctic species is closely tied to the sea ice. Thus, changes in sea ice features (e.g., extent, timing) have a myriad of [...]

For over 150 years, hatchery-origin anadromous salmon and trout have been reared and released throughout the Pacific Northwest to mitigate for lost habitat and sustain harvest opportunity. Some studies demonstrate that introgression of hatchery and naturally produced fish may constrain conservation efforts through maladaptive genetic processes. However, empirical demonstrations of the influence of these genetic interactions on population productivity are lacking, making it difficult to assess their importance relative to other drivers of productivity. We estimated the effect of the proportion of hatcheryorigin spawners (pHOS), proportionate natural influence (PNI), and hatchery fish releases on natural adult winter steelhead recruitment in the Hood River, Oregon, over a 27-year period of record. Adult winter steelhead productivity was not associated with pHOS and PNI. However, natural winter steelhead productivity was positively associated with ocean conditions, stream flow, and hatchery fish release numbers, while negatively associated with pinniped abundance. Our analysis highlights the importance of quantifying the influence of hatchery programs on fish production relative to environmental factors known to affect natural-origin anadromous fish recruitment. Key words: Oncorhynchus mykiss, stock recruitment, Bayesian, state-space, hatchery supplementation, predation, habitat, productivity Pendant plus de 150 ans, des saumons et truites anadromes issus d'ecloseries ont ete eleves et relaches dans toute la region du nord-ouest du Pacifique de l'Amerique du Nord afin de contrer les impacts de la disparition d'habitats et de maintenir des possibilites de recolte. Certaines etudes demontrent que l'introgression de poissons produits en ecloseries et naturellement pourrait restreindre l'efficacite d'efforts de conservation par le biais de processus genetiques mesadaptes. Des demonstrations empiriques de l'influence de ces interactions genetiques sur la productivite des populations manquent toutefois, de sorte qu'il est difficile d'evaluer leur importance par rapport a celle d'autres facteurs influant sur la productivite. Nous avons estime l'effet de la proportion de geniteurs issus d'ecloseries (pHOS), de la part de l'influence naturelle (PNI) et des lachers de poissons issus d'ecloseries sur le recrutement naturel de saumons arc-en-ciel d'hiver adultes dans la riviere Hood (Oregon) sur une periode de 27 ans. La productivite des saumons arc-en-ciel d'hiver adultes n'est pas associee a la pHOS ou a la PNI. La productivite des saumons arc-en-ciel d'hiver presente toutefois une association positive avec les conditions oceaniques, le debit et le nombre de poissons d'ecloseries relaches, et une association negative avec l'abondance de pinnipedes. Notre analyse souligne l'importance de quantifier l'influence des programmes d'ecloseries sur la production de poissons par rapport a celle de facteurs environnementaux dont l'effet sur le recrutement de poissons anadromes d'origine naturelle est etabli. [Traduit par la Redaction] Mots-cles : Oncorhynchus mykiss, recrutement au stock, bayesien, espace d'etats, lacher de poissons d'ecloseries, predation, habitat, productivite, Introduction Numerous factors have contributed to decline of Pacific salmon (Oncorhynchus spp.) and steelhead (Oncorhynchus mykiss) abundance, including overfishing, urbanization, hydropower development, irrigation, and flood control. Since construction of the [...]

Predation is a crucial ecosystem function, transferring nutrients and shaping the abundance and diversity of animals within communities. On coral reefs, fish-fish predation (i.e., piscivory) is arguably one of the best known ecosystem functions, yet is also one of the least well quantified. Recent work has suggested that the prey capture performance of piscivorous fishes may differ when feeding on actively swimming vs. cryptobenthic fish prey. However, the extent of this difference remains unquantified. Our goal, therefore, was to conduct performance-based experiments comparing piscivorous fishes feeding on two different fish prey types, namely, actively swimming vs. cryptobenthic prey (i.e., prey sitting on the benthos). While predators were able to immediately detect actively swimming prey, when feeding on cryptobenthic prey, predators were generally unable to detect the prey until it moved. Both focal predators, the grabber Pseudochromis fuscus and the engulfer Pterois volitans were less successful at capturing cryptobenthic prey (mean 28% probability of capture), compared to actively swimming prey (85%). Overall, our study demonstrates the heterogeneous nature of fish predation on coral reefs, and the challenges of feeding on different prey functional groups., Author(s): Michalis Mihalitsis [sup.1] [sup.2] [sup.3] [sup.4] , David R. Bellwood [sup.1] [sup.2] [sup.3] , Peter C. Wainwright [sup.4] Author Affiliations: (1) https://ror.org/04gsp2c11, grid.1011.1, 0000 0004 0474 1797, Research Hub [...]

Phenology is an ecologically critical attribute that is commonly coordinated with other plant traits. Phenological shifts may be the result of evolutionary adjustments to persistently new conditions, or they may be transitory, varying with annual fluxes in abiotic conditions. In summer-dry, fire-prone Mediterranean-type climates, for example, many plant lineages have historically migrated from forests to more arid shrublands resulting in adaptive trait changes. These shifts in habitat abiotic conditions and biotic interactions influence morphology of flowers and fruits and interact with phenological timing. The Arbutoideae (Ericaceae) is one lineage that illustrates such modifications, with fruit characters evolving among genera from fleshy to dry fruit, thin to stony endocarps, and bird to rodent dispersal, among other changes. We scored herbarium collections and used ancestral trait analyses to determine phenological shifts among the five Arbutoid genera found in semi-arid climates. Our objective was to determine if phenology shifts with the phylogenetic transition to different reproductive characters. Our results indicate that phenological shifts began with some traits, like the development of a stony endocarp or dry fruits, but not with all significant trait changes. We conclude that early phenological shifts correlating with some reproductive traits were permissive for the transition to other later character changes. Key words: Ericaceae, fire regime, obligate seeding, scatter-hoarding, seed predation. La phenologie est un attribut critique d'un point de vue ecologique qui est generalement coordonne avec d'autres traits des vegetaux. Les changements phenologiques peuvent etre le resultat d'ajustements evolutifs a de nouvelles conditions persistantes, ou transitoires, qui varient avec le flux annuel des conditions abiotiques. Dans les climats mediterraneens secs en ete et sujets aux incendies, par exemple, de nombreux lignages de vegetaux ont historiquement migre des forets vers des zones arbustives plus arides, entrainant des changements en matiere de traits adaptatifs. Ces changements dans les conditions abiotiques de l'habitat et les interactions biotiques influencent la morphologie des fleurs et des fruits et interagiront avec le calendrier phenologique. Les Arbutoideae (Ericaceae) constituent un lignage qui illustre de telles modifications, les caracteres des fruits evoluant parmi les genres, de fruits charnus a secs, d'endocarpes minces a pierreux, et de dispersion par les oiseaux a une dispersion par les rongeurs, entre autres changements. Les auteurs ont analyse des collections d'herbiers et utilise l'analyse de traits ancestraux pour caracteriser les changements phenologiques parmi les cinq genres d'Arbutoides trouves dans des climats semi-arides. Leur objectif consistait a determiner si la phenologie change avec la transition phylogenetique vers des caracteres reproducteurs differents. Leurs resultats indiquent que les changements phenologiques ont commence avec certains traits, comme le developpement d'un endocarpe pierreux ou de fruits secs, mais pas avec tous les changements de traits significatifs. Ils concluent que les changements phenologiques precoces en correlation avec certains caracteres reproducteurs etaient permissifs pour la transition vers d'autres changements de caracteres ulterieurs. [Traduit par la Redaction] Mots-cles : Ericaceae, regime des incendies, semis obligatoire, eparpillement, predation des graines., Introduction Phenological changes that occur in coordination with fruit types is an understudied dimension of fruit evolution compared with dispersal or other traits (Forrest and Miller-Rushing 2010). Most studies investigating [...]

Top predators such as coastal birds are essential components of marine food webs, and understanding their trophic interactions forms an essential basis of food web models. At the same time, the proportion of plastic debris in marine food webs has constantly increased while the degree of plastic ingestion by marine birds is still poorly known. In this study, the diets and microplastic uptakes in two numerous benthivorous bird species in the Wadden Sea were examined microscopically, i.e. the common eider (Sommateria mollissima) indicative for the subtidal and the common shelduck (Tadorna tadorna) indicative for the intertidal area. Eiders (n = 42 carcasses; n = 120 faecal samples) mainly ingested common cockles (Cerastoderma edule). Blue mussels (Mytilus edulis) ranged second and-same as the invasive razor clam (Ensis leei)-occurred more frequently than reflected by historic data. Proportions of gastropods, bristle worms and crustaceans were low. Shelducks (n = 20 carcasses; n = 98 faecal samples) fed mainly on small molluscs, especially C. edule, mud snails Peringia ulvae, and amphipods. Plastic debris was found in 92.9% of the stomachs and 74.2% of the faeces from eiders as well as in 95% of the stomachs and 85.7% of the faeces from shelducks. Filaments in shelduck prey remains were significantly larger, whereas there was no species-specific difference in abundance of filaments. Most plastic consisted of brightly coloured filaments Ë 5 mm. These findings indicate regular uptake and excretion of plastic debris by coastal benthivorous seabirds, both in the subtidal and intertidal realm. The origin and mode of uptake of microplastics are discussed., Author(s): Andreas Bange [sup.1] , Anna Backes [sup.1] , Stefan Garthe [sup.1] , Philipp Schwemmer [sup.1] Author Affiliations: (1) grid.9764.c, 0000 0001 2153 9986, Research and Technology Centre (FTZ), University [...]

The interplay of predator encounters and antipredator responses is an integral part of understanding predatorprey interactions and spatial co-occurrence and avoidance can elucidate these interactions. We conducted hard-part dietary analysis of coyotes (Canis latrans Say, 1823) and space use of coyotes and woodland caribou (Rangifer tarandus caribou (Gmelin, 1788)) to test two competing hypotheses about coyote and caribou predator-prey spatial dynamics using resource selection functions. The high encounter hypothesis predicts that coyotes would maximize encounters with caribou via high spatial cooccurrence, whereas the predator stealth hypothesis predicts that through low spatial co-occurrence with caribou, coyotes act as stealth predators by avoiding habitats that caribou typically select. Our dietary analysis revealed that ~46% of sampled coyote diet is composed of caribou. We found that coyote share space with caribou in lichen-barren habitat in both summer and winter and that coyotes co-occur with caribou in forested habitat during summer, but not during winter. Our findings support predictions associated with the high encounter predator hypothesis whereby coyotes and caribou have high spatial co-occurrence promoting caribou in coyote diet. Key words: Canis latrans, coyote, diet analysis, predator-prey interactions, Rangifer tarandus caribou, resource selection function, stealth predators, woodland caribou. La comprehension de l'influence reciproque des rencontres de predateurs et des reactions anti-predation est essentielle a la comprehension des interactions predateurs-proies, les motifs spatiaux de cooccurrence et d' evitement pouvant permettre d' elucider ces interactions. Nous avons realise une analyse des elements durs de l'alimentation de coyotes (Canis latrans Say, 1823) et de l'utilisation de l'espace par les coyotes et les caribous des bois (Rangifer tarandus caribou (Gmelin, 1788)), dans le but de valider deux hypotheses concurrentes concernant la dynamique spatiale des interactions predateursproies des coyotes et des caribous, en utilisant des fonctions de selection de ressources. L'hypothese des rencontres frequentes predit que les coyotes maximiseraient les rencontres de caribous par l'entremise d'une forte cooccurrence spatiale, alors que l'hypothese de la furtivite des predateurs predit que, par une faible cooccurrence spatiale avec les caribous, les coyotes se comportent comme des predateurs furtifs en evitant les habitats typiquement selectionnes par les caribous. Notre analyse de regimes alimentaires revele que ~46 % des regimes alimentaires de coyote echantillonnes comprennent du caribou. Nous observons que les coyotes partagent l'espace avec des caribous dans des habitats de toundra a lichen en ete comme en hiver et qu'il y a cooccurrence de coyotes et de caribous dans des habitats forestiers en ete, mais pas en hiver. Nos constatations appuient les predictions associees a l'hypothese des rencontres frequentes de predateurs selon laquelle la cooccurrence spatiale des coyotes et des caribous est forte, favorisant la presence de caribous dans l'alimentation des coyotes. [Traduit par la Redaction] Mots-cles : Canis latrans, coyote, analyste du regime alimentaire, interactions predateurs-proies, Rangifer tarandus caribou, fonction de selection de ressources, predateurs furtifs, caribou des bois., Introduction Encounter rates of predators with prey are an integral component of predator-prey dynamics (Brown et al. 1999; Brown 1999). The shared space use of a predator and their prey [...]

An array of predators that consume juvenile salmon (genus Oncorhynchus Suckley, 1861) may account for the poor returns of adult salmon to the Salish Sea. However, the Pacific Great Blue Heron (Ardea herodias fannini Chapman, 1901) is rarely listed among the known salmon predators, despite being regularly seen near salmon streams. Investigating heron predation by scanning nesting sites within 35 km of three British Columbia (Canada) rivers for fecal remains containing passive integrated transponder (PIT) tags implanted in >100 000 juvenile salmon from 2008 to 2018 yielded 1205 tags, representing a minimum annual predation rate of 0.3%-1.3% of all juvenile salmon. Most of this predation (99%) was caused by ~420 adult Pacific Great Blue Herons from three heronries. Correcting for tags defecated outside of the heronry raised the predation rates to 0.7%-3.2%, and was as high as 6% during a year of low river flow. Predation occurs during chick-rearing in late spring and accounts for 4.1%-8.4% of the Pacific Great Blue Heron chick diet. Smaller salmon smolts were significantly more susceptible to Pacific Great Blue Heron predation than larger conspecifics. The proximity of heronries relative to salmon-bearing rivers is likely a good predictor of Pacific Great Blue Heron predation on local salmon runs, and can be monitored to assess coast-wide effects of Pacific Great Blue Herons on salmon recovery. Key words: predation, salmon, Oncorhynchus spp., smolts, Pacific Great Blue Heron, Ardea herodias fannini, chicks, diet, mortality. Un eventail de predateurs consommant des saumons (genre Oncorhynchus Suckley, 1861) juveniles pourrait expliquer les faibles retours de saumons adultes vers la mer des Salish. Le grand heron du Pacifique (Ardea herodias fannini Chapman, 1901) ne figure toutefois que rarement dans les listes de predateurs connus des saumons, bien qu'il soit regulierement observe a proximite de cours d'eau a saumons. Le balayage de sites de nidification dans un rayon de 35 km de trois rivieres britanno-colombiennes (Canada) dans le but de retrouver des restes fecaux contenant des etiquettes a transpondeur passif integre implantees dans plus de 100 000 saumons juveniles de 2008 a 2018 pour etudier la predation par les grands herons du Pacifique a produit 1205 etiquettes, ce qui represente un taux de predation annuel minimum de 0,3 % -1,3 % de tous les saumons juveniles. La majeure partie de cette predation (99 %) est le fait de ~420 adultes des grands herons du Pacifique provenant de trois heronnieres. Apres correction pour les etiquettes defequees a l'exterieur de la heronniere, ce taux passe a 0,7 % - 3,2 %, atteignant meme 6 % durant une annee de faible debit des rivieres. La predation se produit durant l'elevage des heronneaux a la fin du printemps et represente de 4,1 % a 8,4 % du regime alimentaire des heronneaux. Les petits saumoneaux sont significativement plus vulnerables a la predation des grands herons du Pacifique que leurs conspecifiques plus gros. La proximite de heronnieres a des rivieres a saumons est probablement un bon predicteur de la predation par les grands herons du Pacifique de saumons dans les montaisons locales et peut etre surveillee pour evaluer les effets a l' echelle de la cote des grands herons du Pacifique sur le retablissement des saumons. [Traduit par la Redaction] Mots-cles: predation, saumon, Oncorhynchus spp., saumoneaux, grand heron du Pacifique, Ardea herodias fannini, heronneaux, regime alimentaire, mortalite., Introduction Many salmon (genus Oncorhynchus Suckley, 1861) populations in the Pacific Northwest have declined in recent decades (Slaney et al. 1996; Coronado and Hilborn 1998; Gustafson et al. 2007; Scott [...]

Salp grazing is important in shaping planktonic food-web structure. However, little is known about the size ranges of their prey in the field or how grazing impacts size structure. This study investigated the feeding habits of seven different species of salps, representing a variety of sizes and life stages across subtropical and subantarctic waters east of New Zealand. Scanning electron microscopy was used to examine the gut contents of 58 salps, which were then compared to water column plankton communities characterized via epifluorescence microscopy, FlowCam, and flow cytometry. While most of the gut contents resembled ambient waters, substantial differences were found amongst some co-occurring species, such as increased retention of submicron bacteria amongst smaller salps like Thalia democratica. We found that even for those salps capable of feeding on bacteria efficiently, nanoplankton and small microplankton still made up the majority of gut biomass. Larger microplankton were rarer in the guts than in the water column, potentially suggesting an upper size-threshold in addition to the lower size-threshold that has been the focus of most previous work. Salp carbon-weighted predator to prey size ratios were variable, with the majority falling between 1000:1 and 10,000:1 depending largely on the size of the salp. Taken together our results indicate that despite being able to feed on submicron particles, picoplankton make up at most 26.4% (mean = 6.4%) of salp gut carbon and are relatively unimportant to the energetics of most salps in this region compared to nanoplankton such as small dinoflagellates and diatoms., Author(s): Christian K. Fender [sup.1] , Moira Décima [sup.2] , Andres Gutiérrez-Rodríguez [sup.3] , Karen E. Selph [sup.4] , Natalia Yingling [sup.1] , Michael R. Stukel [sup.1] [sup.5] Author Affiliations: [...]

Gyrodinium jinhaense and G. moestrupii were described within the past two decades, but the interactions between these two Gyrodinium species and copepods remain to be studied. To elucidate these interactions, the ingestion rate of the calanoid copepods Acartia spp. feeding on G. jinhaense, G. dominans, and G. moestrupii was determined. The maximum ingestion rates of A. hongi/A. omorii on G. jinhaense and G. dominans (3680 and 3480 ng C predator.sup.-1d.sup.-1, respectively) were similar, but they were considerably higher than that on G. moestrupii (1600 ng C predator.sup.-1d.sup.-1). The largest size and fastest swimming speed of G. moestrupii may be partially responsible for this lowest maximum ingestion rate. The ingestion rates of A. hongi/A. omorii on G. jinhaense, G. dominans, and G. moestrupii at the prey concentrations of both 50 and 100 ng C mL.sup.-1 were higher than those on the heterotrophic dinoflagellates Pfiesteria piscicida and Luciella masanensis but lower than those on the heterotrophic dinoflagellates Stoeckeria algicida and Oxyrrhis marina. Therefore, G. jinhaense, G. dominans, and G. moestrupii are moderate heterotrophic dinoflagellate prey for Acartia spp., Author(s): Moo Joon Lee [sup.1] , Hae Jin Jeong [sup.2] [sup.3] , Yeong Du Yoo [sup.4] , Sang Ah Park [sup.2] , Hee Chang Kang [sup.2] Author Affiliations: (1) grid.443830.8, [...]

Understanding how mesopredators manage the risks associated with apex predators is key to explaining impacts of apex predators on mesopredator populations and patterns of mesopredator space use. Here we examine the spatial response of coyotes (Canis latrans Say, 1823) to risk posed by wolves (Canis lupus Linnaeus, 1758) using data from sympatric individuals fitted with GPS collars in subarctic Alaska, USA, near the northern range limit for coyotes. We show that coyotes do not universally avoid wolves, but instead demonstrate season-specific responses to both wolf proximity and long-term use of the landscape by wolves. Specifically, coyotes switched from avoiding wolves in summer to preferring areas with wolves in winter, and this selection was consistent across short-term and longer term temporal scales. In the summer, coyotes responded less strongly to risk of wolves when in open areas than when in closed vegetation. We also demonstrate that coyotes maintain extremely large territories averaging 291 [km.sup.2], and experience low annual survival (0.50) with large carnivores being the largest source of mortality. This combination of attraction and avoidance predicated on season and landcover suggests that mesopredators use complex behavioral strategies to mediate the effects of apex predators. Key words: coyote, Canis latrans, wolf, Canis lupus, habitat selection, risk, subarctic. La compréhension de la gestion que font les mésoprédateurs des risques associés aux superprédateurs est d'importance clé pour expliquer les impacts de superprédateurs sur les populations de mésoprédateurs et les motifs d'utilisation de l'espace de ces derniers. Nous examinons la réaction spatiale de coyotes (Canis latrans Say, 1823) au risque posé par les loups (Canis lupus Linnaeus, 1758) en utilisant des données sur des individus sympatriques munis de colliers GPS en Alaska (Etats-Unis) subarctique, près de la limite septentrionale de l'aire de répartition des coyotes. Nous démontrons que les coyotes n'évitent pas universellement les loups, mais présentent plutôt différentes réactions selon la saison tant à la proximité des loups qu'à l'utilisation à long terme du paysage par ces derniers. Plus précisément, les coyotes passent de l'évitement des loups en été à une préférence pour des secteurs renfermant des loups en hiver, et cette sélection est cohérente à des échelles temporelles aussi bien courtes que longues. En été, les coyotes réagissent moins fortement au risque posé par les loups quand ils sont dans des secteurs ouverts que dans des secteurs à végétation fermée. Nous démontrons également que les coyotes maintiennent des territoires extrêmement vastes, faisant en moyenne 291 [km.sup.2], et qu'ils présentent un faible taux de survie annuelle (0,50), les grands carnivores constituant la plus grande cause de mortalité. Cette combinaison d'attraction et d'évitement en fonction de la saison et de la couverture du sol indiquerait que les mésoprédateurs emploient des stratégies comportementales complexes pour moduler les effets des superprédateurs. [Traduit par la Rédaction] Mots-clés: coyote, Canis latrans, loup, Canis lupus, sélection de l'habitat, risque, subarctique., Introduction The risk of injury or death by predation is a key driver of animal behavior (Thomson et al. 2006; Valeix et al. 2009; Laundré et al. 2010; Oriol-Cotterill et [...]

Distinguishing the cause and magnitude of capture-related mortality (CRM) in fishes is important for effective management. To better understand CRM in yellowfin tuna (Thunnus albacares) released in the recreational troll fishery off the United States east coast, 48 fish (76-127 cm curved fork length, CFL) were monitored for up to 86 days postrelease with survivorship pop-up satellite archival tags. Recovered data indicated 40 fish were alive at the time of tag detachment and eight died, including six from predation, from 0 to 30 days postrelease. Survival model variants were constructed to independently estimate the rates of immediate capture and handling (CH), postrelease (PR), total CRM (CH + PR), and natural mortality (M) for small ([less than or equal to] 103 cm CFL) and large (>103 cm CFL) fish under different hypotheses and causes of mortality. CH was low (0%-8%) for both size classes but predation was an important component of PR, particularly in the small size class. Total CRM was 51% (95% CI: 26%, 81%) for small and 8% (95% CI: 2%, 30%) for large fish. La determination de la cause et de l'ampleur de la mortalite reliee a la capture (MRC) chez les poissons est importante pour une gestion efficace. Afin de mieux comprendre la MRC des thons albacores (Thunnus albacares) relaches dans la peche sportive a la traine au large de la cote est des Etats-Unis, 48 poissons (longueur courbee a la fourche, LCF, de 76 a 127 cm) ont ete surveilles jusqu'a 86 jours apres leur lacher a l'aide d'etiquettes satellites autodetachables optimisees pour les etudes de survie. Les donnees recueillies indiquent que 40 poissons etaient vivants au moment ou l'etiquette s'est detachee et que huit sont morts, y compris par predation, dans les 30 jours suivant le lacher. Differentes variantes de modeles de survie ont ete construites pour estimer de maniere independante les taux de MRC associe a la capture et la manipulation immediates (CH), post-lacher (PR) et total (CH + PR), ainsi que la mortalite naturelle (M) pour les petits (LCF < 103 cm) et grands (LCF > 103 cm) poissons, etant donne differentes hypotheses et causes de mortalite. Le CH etait faible (0-8 %) pour les deux classes de tailles, mais la predation representait une composante importante du PR, en particulier pour la petite classe de tailles. Le taux de MRC total etait de 51 % (IC de 95 % : 26 %, 81 %) pour les petits poissons et de 8 % (IC de 95 % : 2 %, 30 %) pour les grands poissons. [Traduit par la Redaction], Introduction Understanding capture-related mortality (CRM) in fishes discarded or released in commercial and recreational fisheries is pivotal to effective stock assessment and fishery management. In addition to using the rates [...]

Predation is typically the primary cause of nest failure for songbirds, even within unfragmented forested landscapes. In recent years, video cameras have been used to study causes and patterns of nest failure in a variety of habitats and regions. However, surprisingly few video camera studies have been performed in forests of northeastern North America. Over 5 years, we monitored Veery (Catharus fuscescens) nesting success in a mature forest landscape in northeastern Pennsylvania and used video cameras at a subset of nests to identify the predator assemblage and to describe relevant patterns of predation. Overall, we located 289 nests and recorded 67 of these nests with video cameras. Annual nest survival rates varied substantially across years (0.17-0.44) with this variation driven primarily by the dominant source of nest mortality: predation. Video cameras recorded 40 predation events by 12 predator species. Mammals (7 species), birds (4 species), and snakes (1 species) accounted for 75%, 20%, and 2.5% of predation events recorded, respectively. Predation events occurred during the day more often than expected by chance. Logistic exposure analyses indicated that both camera presence and nest age affected nest survival by influencing predation rates, but date did not. The diverse predator community observed depredating Veery nests led to low nesting success in some years, but also demonstrated that causes of nest failure vary by year and cannot be attributed to any single predator species or group. A greater apparent predation rate at nests with cameras likely resulted from a more frequent visitation rate to these nests by researchers compared to those without cameras and suggests a potential bias with artificially decreased nest survival estimates in years in which cameras were used. Received 20 March 2019. Accepted 12 September 2020. Key words: mature forest, nest predators, Pennsylvania, songbird breeding ecology, video cameras. La depredacion es tipicamente la causa principal del fallo de nidos para los pajaros, atin en al interior de paisajes de bosques sin fragmentar. En anos recientes, se han usado vidcocamaras para estudiar las causas y patrones del fallo de nidos en una variedad de habitats y regiones. Sin embargo, se han llevado a cabo sorpresivamente pocos cstudios con vidcocamaras en bosques cn el noreste de Norteamerica. Durante 5 afios. monitoreamos el exito de anidacion del zorzal Catharus fuscescens en un bosque maduro en el noreste de Pennsylvania y usamos vidcocamaras en un subconjunto de los nidos para identificar el ensamble dc depredadores y para describir los patrones relevantes de depredacion. En total, encontramos 289 nidos y registramos 67 de estos con videocamaras. Las tasas anuales de sobrevivencia de nidos variaron sustancialmente interanualmente (0.17-0.44) siendo esta variation causada principalmente por la fucnte dominante de mortandad en el nido: depredacion. Las videocamaras registraron 40 eventos de depredacion por 12 especies de depredadores. Mamiferos (7 especies), aves (4 especies) y serpientes (1 especie) fueron responsables del 75, 20 y 2.5% de los eventos de depredacion registrados, respectivamente. Los eventos de depredacion tuvicron lugar durante el dia mas frecuentemente dc lo csperado de manera aleatoria. Nuestros analisis de exposicion logistica indican que ambas, la presencia de la camara y la edad del nido afectaron la sobrevivencia del nido influenciando las tasas de depredacion, mientras que la fecha no tiene tal efecto. La diversa comunidad de depredadores observada depredando nidos dc este zorzal tuvo como consecuencia un bajo exito de anidacion cn algunos anos. pero tambien demostro que las causas del fallo de nidos variaron por ano y no pueden ser atribuidos a alguna especie individual o grupo de depredadores. La mayor tasa de depredacion aparente en nidos con camaras posiblemente fue el resultado de una tasa mayor dc visitas en dichos nidos, en comparacion con aquellos sin camaras. Esto sugiere un posible sesgo en las estimaciones de sobrevivencia de nidos, que disminuyo en los anos en que se usaron camaras. Palabras clave: bosque maduro, depredadores de nidos, ecologia reproductiva de pajaros, Pennsylvania, videocamaras., Population declines of many migratory forest songbirds that breed in North America have been attributed, at least in part, to habitat loss and fragmentation (e.g., Askins et al. 1990, Donovan [...]

Teleosts exhibit inter- and intra-specific variation in the size and shape of their brains. Interpopulation differences in gross brain morphology among numerous teleost fish species have been observed and have been partially attributed to plastic changes in response to their environment, including predation. These differences manifest themselves macroscopically, potentially because teleosts retain the capacity for active neuroproliferation into adulthood. Building on previous work, showing chronic exposure to predation can affect brain morphology, we sought to determine whether these differences manifest themselves on a time scale shown to induce phenotypically plastic behavioural changes. In separate trials, we held northern redbelly dace (Phoxinus eos (Cope, 1861) = Chrosomus eos Cope, 1861) and juvenile Atlantic salmon (Salmo salar Linnaeus, 1758) in semi-natural conditions and exposed them to conspecific skin extract as a proxy for predation risk over 2 weeks. After exposure, their brains were excised, photographed, and analyzed for size (multivariate ANOVA) and shape (Procrustes ANOVA). Despite their brief exposure to simulated predation pressure, subjects from both species developed significantly different brain morphologies. Compared with controls, the Atlantic salmon exhibited a different brain shape and smaller optic tecta, whereas the northern redbelly dace had larger brains with more developed olfactory bulbs and optic tecta. Our results highlight the rapidity with which external environment can alter patterns of growth in the brain. Key words: predation risk, gross brain morphology, plasticity, teleost, juvenile Salmo salar, Phoxinus eos, Chrosomus eos. Les téléostéens présentent des variations inter- et intra-spécifiques de la taille et de la forme du cerveau. Des variations de la morphologie grossièreducerveau entre populations pour denombreuses espècesde poissons téléostéens ont été observes et en partie attribuées à des changements plastiques des réactions au milieu, incluant la prédation. Ces différences ont des manifestations macroscopiques, possiblement en raison du fait que les téléostéens adultes conservent la capacité de neuroprolifération active. En partant de travaux antérieurs qui montrent que l'exposition chronique à la prédation peut avoir une incidence sur la morphologie du cerveau, nous avons tenté de déterminer si ces différences se manifestent à une échelle temporelle dont il est démontré qu'elle induit des changements comportementaux plastiques du point de vue phénotypique. Dans des essais distincts, nous avons maintenu des ventres rouges du Nord (Phoxinus eos (Cope, 1861) = Chrosomus eos Cope, 1861) et des saumons atlantiques (Salmo salar Linnaeus, 1758) juvéniles dans des conditions semi-naturelles et les avons exposés pendant deux semaines à de l'extrait de peau de congénères simulant un risque de prédation. Après l'exposition, leurs cerveaux ont été excisés, photographiés et analysés pour en déterminer la taille (analyse de la variance multivariée) et la forme (analyse de la variance procustéene). Malgré la courte exposition à une pression de prédation simulée, les cerveaux des sujets des deux espèces ont subi des changements morphologiques significatifs. Comparés aux témoins, les saumons atlantiques présentaient une forme du cerveau différente et des tectums optiques plus petits, alors que les ventres rouges du Nord avaient des cerveaux plus grands présentant des bulbes olfactifs et tectums optiques plus développés. Nos résultats font ressortir la rapidité avec laquelle le milieu externe peut modifier des motifs de croissance dans le cerveau. [Traduit par la Rédaction] Mots-clés : risque de prédation, morphologie grossière du cerveau, plasticité, téléostéen, Salmo salar juvénile, Phoxinus eos, Chrosomus eos., Introduction Studies have demonstrated high degrees of variability in the brain morphology of teleost fishes, both within and between species (Kotrschal et al. 1998). Within species, variation in brain morphology [...]

Predator-prey cycles rank among the most fundamental concepts in ecology, are predicted by the simplest ecological models and enable, theoretically, the indefinite persistence of predator and prey.sup.1-4. However, it remains an open question for how long cyclic dynamics can be self-sustained in real communities. Field observations have been restricted to a few cycle periods.sup.5-8 and experimental studies indicate that oscillations may be short-lived without external stabilizing factors.sup.9-19. Here we performed microcosm experiments with a planktonic predator-prey system and repeatedly observed oscillatory time series of unprecedented length that persisted for up to around 50 cycles or approximately 300 predator generations. The dominant type of dynamics was characterized by regular, coherent oscillations with a nearly constant predator-prey phase difference. Despite constant experimental conditions, we also observed shorter episodes of irregular, non-coherent oscillations without any significant phase relationship. However, the predator-prey system showed a strong tendency to return to the dominant dynamical regime with a defined phase relationship. A mathematical model suggests that stochasticity is probably responsible for the reversible shift from coherent to non-coherent oscillations, a notion that was supported by experiments with external forcing by pulsed nutrient supply. Our findings empirically demonstrate the potential for infinite persistence of predator and prey populations in a cyclic dynamic regime that shows resilience in the presence of stochastic events. The potential for infinite persistence of planktonic predator and prey cycles is experimentally demonstrated and these cycles show resilience in the presence of stochastic events., Author(s): Bernd Blasius [sup.1] [sup.2] , Lars Rudolf [sup.3] , Guntram Weithoff [sup.4] [sup.5] , Ursula Gaedke [sup.4] [sup.5] , Gregor F. Fussmann [sup.6] Author Affiliations: (1) Institute for Chemistry [...]

A neglected question in the study of communal breeding concerns why alloparental behaviour begins at variously late stages in the breeding cycle. In group-living corvids, the delay tends to be longer in species that are small and (or) typically have only a small nonbreeder complement. This pattern has been attributed to the relatively poor defensive capabilities of such species and their consequently greater need to minimize predator-attracting traffic to the nest or fledglings. We tested this predator avoidance hypothesis with the Canada Jay (Perisoreus canadensis (Linnaeus, 1766)), a species in which the feeding of young by any nonbreeders in the family group is delayed until the fledgling period. We reasoned that, on Anticosti Island, Quebec (Canada), in the absence of squirrels and other nest predators, nonbreeders might be permitted to feed nestlings as well as fledglings, and that breeders might feed nestlings more frequently (with smaller food loads) than on the mainland. We found no evidence for either prediction and thus no support for the predator avoidance hypothesis but suggest that Anticosti Canada Jays may have had insufficient time to evolve behaviour more appropriate for their predator-free environment. Secondarily, we confirmed that in all observed instances, the nonbreeders were offspring of the breeding pair from previous years and that they therefore failed to provision nestlings in spite of an apparent genetic interest to do so. Key words: predator avoidance, communal breeding, Canada Jay, Perisoreus canadensis, Anticosti Island, provisioning rate, feeding rate, nestling, fledgling, red squirrel, Tamiasciurus hudsonicus. Une question trop peu abordee dans l'etude de la reproduction communautaire consiste a savoir pourquoi le comportement alloparental commence a differents moments tard durant le cycle de reproduction. Chez les corvides vivant en groupe, ce delai tend a etre plus long chez les especes petites ou qui ne comptent typiquement qu'un petit nombre d'individus non reproducteurs. Cela a ete attribue aux capacites de defense relativement faibles de ces especes et, donc, a la necessite plus grande pour elles de minimiser le trafic pouvant attirer les predateurs vers le nid ou les jeunes a l'envol. Nous avons teste cette hypothese d'evitement des predateurs chez le mesangeai du Canada (Perisoreus canadensis (Linnaeus, 1766)), une espece dont l'alimentation des jeunes par tout individu non reproducteur dans le groupe familial est retardee jusqu'a la periode suivant l'envol du nid. Nous avons postule que, dans l'lle d'Anticosti (Quebec, Canada), en l'absence d'ecureuils et d'autres predateurs des nids, il pourrait etre permis aux individus non reproducteurs de nourrir les oiseaux niais ainsi que les jeunes apres l'envol, et que les individus reproducteurs pourraient nourrir les oiseaux niais plus frequemment (avec de plus petites charges de nourriture) que sur le continent. Nous n'avons trouve aucune preuve de l'une ou l'autre de ces predictions et, donc, aucune preuve appuyant l'hypothese d'evitement des predateurs, mais nous suggerons que les mesangeais du Canada d'Anticosti pourraient ne pas avoir eu le temps de developper un comportement mieux adapte a un milieu exempt de predateurs. En second lieu, nous avons confirme que, dans tous les cas observes, les individus non reproducteurs etaient des rejetons d'annees anterieures du couple reproducteur et qu'ils n'etaient donc pas arrives a approvisionner des oiseaux niais malgre un apparent interet genetique. [Traduit par la Redaction] Mots-cles : evitement de predateurs, reproduction communautaire, mesangeai du Canada, Perisoreus canadensis, He d'Anticosti, taux d'approvisionnement, taux d'alimentation, oiseau niais, jeune a l'envol, ecureuil roux, Tamiasciurus hudsonicus., Introduction Many aspects of communal breeding have been studied in birds and other vertebrates (Brown 1987; Jennions and Macdonald 1994; Koenig and Dickinson 2004, 2016), but the question of why [...]

Prey are under immense pressure to make context-specific, behavioural decisions. Prey use public information to reduce the costs associated with making inappropriate decisions. Chemical cues are commonly used by aquatic vertebrates to assess local threats and facilitate behavioural decision making. Previous studies on chemosensory assessment of risk have largely focused on damage-released alarm cues, with the cues released by disturbed or stressed prey (i.e., disturbance cues) receiving less attention. Disturbance cues are 'early-warning signals' common among aquatic vertebrates that may warn conspecific and heterospecific prey guild members of potential risk. Initially, we conducted a series of laboratory studies to determine (i) if guppies (Poecilia reticulata Peters, 1859) produce and respond to disturbance cues and (ii) if relative concentration (donor group size) determines response intensity. Secondly, we examined if guppies and convict cichlids (Amatitlania nigrofasciata (Gunther, 1867)) show similar response patterns to their own vs. heterospecific disturbance cues. Our results suggest that guppies exhibit increased predator avoidance behaviour to conspecific disturbance cues (relative to water from undisturbed conspecifics) and increased donor group size lead to stronger antipredator responses. However, although guppies and cichlids respond to each other's disturbance cues, we found no effect of donor group size towards heterospecific disturbance cues. Our results suggest that disturbance cues are not generalized cues and present a degree of species-specificity. Key words: disturbance cues, public information, predator avoidance, guppy, Poecilia reticulata, convict cichlid, Amatitlania nigrofasciata, heterospecific donors, conspecific donors. Les proies sont assujetties aune enorme pression les poussant a prendre des decisions comportementales en fonction du contexte. Elles se servent d'information publique pour reduire les couts associes a la prise de mauvaises decisions. Des signaux chimiques sont souvent utilises par des vertebres aquatiques pour evaluer les menaces locales et faciliter la prise de decisions comportementales. Les etudes anterieures sur l'evaluation chimiosensorielle du risque se sont principalement interessees aux signaux d'alarme decoulant de prejudices subis, les signaux produits par des proies perturbees ou stressees (c.-a-d. les signaux de perturbation) recevant moins d'attention. Les signaux de perturbation sont des << signaux d'alerte rapide >> repandus chez les vertebres aquatiques, qui peuvent avertir des membres conspecifiques et heterospecifiques de la guilde de proies d'un risque potentiel. Nous avons initialement realise une serie d'etudes en laboratoire visant a determiner (i) si les guppys (Poecilia reticulata Peters, 1859) produisent des signaux de perturbation et y reagissent et (ii) si la concentration relative (taille du groupe de donneurs) determine l'intensite de la reaction. En deuxieme lieu, nous avons verifie si les guppys et les cichlides a bandes (Amatitlania nigrofasciatus (Gunther, 1867)) presentent des motifs de reaction semblables aux signaux de perturbation d'individus conspecifiques et heterospecifiques. Nos resultats donnent a penser que les guppys presentent un comportement d'evitement des predateurs plus fort en presence de signaux de perturbation de conspecifiques (par rapport a de l'eau venant de conspecifiques non perturbes) et qu'une plus grande taille du groupe de donneurs produit des reactions anti-predateurs plus fortes. Si les guppys et les cichlides reagissent a leurs signaux de perturbation mutuels, nous n'avons toutefois note aucun effet de la taille du groupe de donneurs sur les signaux de perturbation d'individus heterospecifiques. Nos resultats portent a croire que les signaux de perturbation ne sont pas des signaux generalises et qu'ils sont, a un certain degre, propres a l'espece. [Traduit par la Redaction] Mots-cles: signaux de perturbation, information publique, evitement des predateurs, guppy, Poecilia reticulata, cichlide a bandes, Amatitlania nigrofasciatus, donneurs heterospecifiques, donneurs conspecifiques., Introduction Predation risk is a pervasive selection pressure, shaping the behavioural phenotypes of prey animals. In fact, in response to the nonconsumptive effects of predation (Preisser et al. 2005), prey [...]

Diet specialization has important consequences for how individuals or species deal with environmental change that causes changes in availability of prey species. We took advantage of a 'natural experiment'--establishment of a commercial insect farm--that introduced a novel prey item, black soldier flies (Hermetia illucens (Linnaeus, 1758)), to the diet-specialist European Starling (Sturnus vulgaris Linnaeus, 1758). We investigated evidence for individual diet specialization (IDS) and the consequences of diet specialization and exploitation of novel prey on breeding productivity. In all 4 years of our study, tipulid larvae were the most common prey item. Soldier flies were not recorded in diets in 2013-2014; however, coincident with the establishment of the commercial insect farming operation, they comprised 22% and 30% of all prey items in the diets of European Starling females and males, respectively, in 2015. There was marked individual variation in use of soldier flies (4%-48% and 2%-70% in females and males, respectively), but we found little evidence of dichotomous IDS, i.e., where only some individuals have a specialized diet. We found no evidence for negative effects of use of soldier flies on breeding productivity: brood size at fledging and chick quality (mass, tarsus length) were independent of the number and proportion (%) of soldier flies returned to the nest. Key words: insect farming, European Starlings, diet specialization, tipulid, Hermetia illucens, breeding productivity, specialist-generalist. La specialisation du regime alimentaire a d'importantes consequences pour la maniere dont les individus ou les especes reagissent aux changements environnementaux qui modifient la disponibilite d'especes de proies. Nous avons tire profit d'une <>, l'etablissement d'une ferme a insectes commerciale, qui introduisait une nouvelle proie, la mouche soldat noire (Hermetia illucens (Linnaeus, 1758)), pour l'etourneau sansonnet (Sturnus vulgaris Linnaeus, 1758), une espece dont le regime alimentaire est specialise. Nous avons examine les indices de specialisation du regime alimentaire individuel (IDS) et les consequences de la specialisation du regime alimentaire et de l'exploitation de nouvelles proies sur la productivite reproductrice. Pour toutes les 4 annees de l'etude, les larves de tipules constituaient les proies les plus frequentes. Des mouches soldats n'ont pas ete observees dans les regimes alimentaires en 2013-2014; cependant a la suite de l'etablissement de la ferme a insectes commerciale, elles representaient 22 % et 30 % de toutes les proies individuelles chez les femelles et les males, respectivement, en 2015. Une variation marquee entre individus de l'utilisation de mouches soldats (4 %-48 % et 2 %-70 % chez les femelles et les males, respectivement) a ete notee, mais peu d'indices d'IDS dichotome, c'est-a-dire une situation dans laquelle seuls certains individus ont un regime alimentaire specialise. Nous n'avons note aucun indice d'effets negatifs de l'utilisation de mouches soldats sur la productivite reproductrice; la taille des couvees au moment de l'envol du nid et la qualite des oisillons (masse, longueur du tarse) etaient independantes du nombre et de la proportion (%) de mouches soldats rapportees au nid. [Traduit par la Redaction] Mots-cles: culture d'insectes, etourneau sansonnet, specialisation du regime alimentaire, tipule, Hermetia illucens, productivite reproductrice, specialiste-generaliste., Introduction Ecological specialization is a key concept in ecology and evolutionary biology and the question of what governs the dietary niche of an animal has long been a central focus [...]

Steroid hormones play critical organizational and activational roles during vertebrate development, impacting everything from sexual differentiation to metabolic activity. For oviparous species such as birds, these hormones are transferred from female to egg during follicle maturation, and differences in relative and absolute concentrations of the steroid hormones may reflect differences in life history, developmental, and ecological conditions. Prior work on yolk steroid hormones has focused on a handful of candidate hormones (e.g., testosterone, androstenedione, and corticosterone), but we used high-performance liquid chromatography with tandem mass spectroscopy (LC-MS-MS) to quantify 27 yolk steroids from the eggs of seven shrubland bird species (American Robin, Turdus migratorius Linnaeus, 1766; Brown-headed Cowbird, Molothrus ater (Boddaert, 1783); Brown Thrasher, Toxostoma rufum (Linnaeus, 1758); Eastern Towhee, Pipilo erythrophthalmus (Linnaeus, 1758); Field Sparrow, Spizella pusilla (A. Wilson, 1810); Gray Catbird, Dumetella carolinensis (Linnaeus, 1766); Northern Cardinal, Cardinalis cardinalis (Linnaeus, 1758)). In addition to comparing steroid profiles across species, we conducted exploratory analyses to determine how the hormones clustered using a principal component (PC) approach and if PCs were correlated with aspects of egg resources (relative egg size, proportion yolk), life-history traits (embryonic and nestling development speed), and nest-predation risk (daily survival rate (DSR)). We documented substantial interspecific variation in both absolute and proportional endocrine profiles. PCAs indicated that glucocorticoids generally clustered together (PC1), but other classes of steroids did not. PC2 and PC3 strongly covaried with egg resources, DSR, and development speed, suggesting that they reflect adaptive patterns of maternal hormone deposition.Key words: avian community, egg composition, life history, maternal effects, nest predation, shrubland, steroid hormones, yolk.Les hormones steroides jouent des roles cles d'organisation et d'activation durant le developpement des veitebres, en influencant differents aspects qui vont de la differenciation sexuelle a l'activite metabolique. Pour les especes ovipares comme les oiseaux, ces hormones sont transferees de la femelle aux oeufs durant la maturation des follicules, et des differences sur le plan des concentrations relatives et absolues d'hormones steroides peuvent refleter des differences sur le plan du cycle biologique et des conditions developpementales ou ecologiques. Si les travaux anterieurs sur les hormones steroides dans le vitellus ont mis l'accent sur quelques hormones candidates (p.ex. testosterone, androstenedione et corticosterone), nous utilisons la chromatographie en phase liquide de haute performance jumelee a la spectrometrie de masse (LC-MS-MS) pour quantifier 27 steroides vitellins d'oeufs de sept especes d'oiseaux de milieux arbustifs (merle d'Amerique, Turdus migratorius Linnaeus, 1766; vacher a tete brune, Molothrus ater (Boddaert, 1783); moqueur roux, Toxostoma rufum (Linnaeus, 1758); tohi a flancs roux, Pipilo erythrophthalmus (Linnaeus, 1758); bruant des champs, Spizella pusilla (A. Wilson, 1810); moqueur chat, Dumetella carolinensis (Linnaeus, 1766); cardinal rouge, Cardinalis cardinalis (Linnaeus, 1758)). En plus de comparer les profils de steroides entre especes, nous avons mene des analyses exploratoires pour determiner comment les hormones se regroupent par une approche basee sur les composantes principales (CP) et si les CP sont correlees a des aspects des ressources de l'ceuf (taille relative de l'oeuf, proportion de vitellus), a des caracteres du cycle biologique (rythme de developpement des embryons et des oiseaux niais) et au risque de predation des nids (taux de survie quotidien (TSQ)). Nous documentons une variation interspecifique considerable dans les profils endocriniens tant absolus que proportionnels. L'ACP indique que les glucocorticoides se regroupent generalement (PC1), mais que ce n'est pas le cas d'autres classes de steroides. Les CP2 et CP3 presentent une forte covariance avec les ressources de l'cuf, le TSQ et le rythme de developpement, ce qui porte a croire qu'elles refletent des motifs d'adaptation du depot d'hormones maternelles. [Traduit par la Redaction]Mots-cles: communaute aviaire, composition de l'oeuf, cycle biologique, effets maternels, predation des nids, milieu arbustif, hormones steroides, vitellus., IntroductionFemale birds have the ability to impact the condition and survival of their offspring via differential allocation of egg resources. These maternal effects can reflect condition-dependent allocation strategies, in which [...]

The identification of when, how and where animals feed is essential to estimate the amount of energy they obtain and to study the processes associated with prey search and consumption. We combined the use of animal-borne video cameras and accelerometers to characterise the body and head movements associated to four types of prey capture behaviours in the Magellanic Penguin (Spheniscus magellanicus). In addition, we evaluated how the K-Nearest Neighbour (K-NN) algorithm recognized these behaviours from acceleration data. Finally, we compared the total capture and the capture per unit time (CPUT) derived by identifying prey capture events using the K-NN algorithm to that derived by counting undulations in the dive profile ('wiggles'). During captures, body and head movements were highly variable in the tridimensional space. Energy expenditure (i.e., VeDBA values) during diving periods with prey captures was from three to four times higher than during controls diving periods (i.e., with no capture events). The K-NN classification resulted effective and showed accuracy scores above 90% when considering both head and body related features. In addition, when captures were estimated using the K-NN method, the CPUT was similar or higher to that estimated by counting wiggles. Our study contributes to the knowledge of the trophic ecology of this species and provides an alternative method for estimating prey consumption in the Magellanic Penguin and other diving seabirds., Author(s): Monserrat Del Caño [sup.1] , Flavio Quintana [sup.1] , Ken Yoda [sup.2] , Giacomo Dell'Omo [sup.3] , Gabriela S. Blanco [sup.1] , Agustina Gómez-Laich [sup.4] Author Affiliations: (1) grid.423606.5, [...]

We developed a foraging model for young fishes that incorporates handling and digestion rate to estimate daily food consumption. Feeding trials were used to quantify functional feeding response, satiation, and gut evacuation rate. Once parameterized, the foraging model was then applied to evaluate effects of prey type, prey density, water temperature, and fish size on daily feeding rate by age-0 (19-70 mm) pallid sturgeon (Scaphirhynchus albus). Prey consumption was positively related to prey density (for fish >30 mm) and water temperature, but negatively related to prey size and the presence of sand substrate. Model evaluation results revealed good agreement between observed estimates of daily consumption and those predicted by the model ([r.sup.2] = 0.95). Model simulations showed that fish feeding on Chironomidae or Ephemeroptera larvae were able to gain mass, whereas fish feeding solely on zooplankton lost mass under most conditions. By accounting for satiation and digestive processes in addition to handling time and prey density, the model provides realistic estimates of daily food consumption that can prove useful for evaluating rearing conditions for age-0 fishes. Nous avons developpe un modele d'approvisionnement pour les jeunes poissons qui integre la manipulation et le taux de digestion pour estimer la consommation quotidienne de nourriture. Des essais d'alimentation ont ete utilises pour quantifier la reponse fonctionnelle d'alimentation, la satiete et le taux d'evacuation gastrique. Une fois parametre, le modele d'approvisionnement a ete utilise pour evaluer les effets du type de proie, de la densite de proies, de la temperature de l'eau et de la taille des poissons sur le taux d'alimentation quotidien d'esturgeons blancs (Scaphirhynchus albus) de moins d'un an (19-70 mm). La consommation de proies etait positivement reliee a la densite de proies (pour les poissons de >30 mm) et a la temperature de l'eau, mais negativement reliee a la taille des proies et a la presence d'un substrat de sable. Les resultats d'evaluation du modele indiquent une bonne concordance entre les estimations observees de la consommation quotidienne et les estimations predites par le modele ([r.sup.2] = 0,95). Les simulations a l'aide du modele montrent que les poissons se nourrissant de larves de chironomides ou d'ephemeropteres pouvaient prendre du poids, alors que les poissons ne se nourrissant que de zooplancton perdaient du poids dans la plupart des conditions. En tenant compte de la satiete et de processus digestifs en plus du temps de manipulation et de la densite de proies, le modele fournit des estimations realistes de la consommation quotidienne de nourriture qui peuvent s'averer utiles pour evaluer les conditions de croissance de poissons de moins d'un an. [Traduit par la Redaction], Introduction Factors affecting growth and survival of fishes during their early life history can have an important influence on recruitment dynamics (Madenjian and Carpenter 1991; Fulford et al. 2006). Yet [...]

Abstract: Resource competition and apparent competition have both been suggested as the cause of mule deer (Odocoileus hemionus (Rafinesque, 1817)) decline concurrent with white-tailed deer (Odocoileus virginianus (Zimmerman, 1780)) increase. [...]

Abstract: Predation danger is pervasive for small mammals and is expected to select strongly for behavioural tactics that reduce the risk. In particular, since it may be considered a cost [...]

Predation on cod (Gadus morhua) eggs by sprat (Sprattus sprattus) and herring (Clupea harengus) is known to be one of the processes influencing reproductive success of the eastern Baltic cod and has been reported to have contributed to lack of recovery of the stock in the 1990s. This study quantifies the predation on cod eggs in the Bornholm Basin, the major spawning area of cod in the central Baltic Sea, in the 1990s in comparison with the second half of the 2000s. The analyses involve estimating daily consumption rates of predator populations, which are then compared with corresponding daily egg production rates. As a methodological advancement compared with earlier studies, spatially resolved information on predator distribution and abundance is utilized in quantifying predator stock size. This resulted in more realistic consumption estimates in relation to overall egg production compared with earlier studies that consistently overestimated predation pressure by clupeids. Our results suggest a generally lower predation pressure on cod eggs in the mid- to late 2000s, due to a combination of reduced predator abundance and lower daily rations by individual predators. Il est etabli que la predation des reufs de morue (Gadus morhua) par les sprats (Sprattus sprattus) et les harengs (Clupea harengus) est un des processus qui influencent le succes de reproduction de la morue de la mer Baltique orientale, et des rapports indiquent qu'elle contribuerait a expliquer l'absence de retablissement du stock dans les annees 1990. L'etude quantifie la predation des reufs de morue dans le bassin de Bornholm, le principal lieu de frai des morues dans la partie centrale de la mer Baltique, dans les annees 1990 comparativement a la deuxieme moitie des annees 2000. Les analyses comprennent l'estimation des taux de consommation quotidiens de populations de predateurs, qui sont ensuite compares aux taux de production d'reufs quotidiens correspondants. Une avancee methodologique par rapport aux etudes anterieures consiste en l'utilisation d'information spatialement resolue sur la repartition et l'abondance des predateurs pour quantifier la taille des stocks de predateurs, ce qui produit des estimations plus realistes de la consommation au vu de la production d'reufs globale comparativement a celles d'etudes anterieures, qui surestimaient uniformement la pression de predation par des clupeides. Nos resultats indiqueraient une pression de predation generalement plus faible sur les reufs de morue au milieu et a la fin des annees 2000 decoulant de la combinaison d'une moins grande abondance de predateurs et de plus faibles rations quotidiennes individuelles par predateur. [Traduit par la Redaction], Introduction In the Baltic Sea, cod (Gadus morhua) is the main predator fish (Sparholt 1994), being both of high ecological and commercial importance (e.g., Rudstam et al. 1994; Kornilovs et [...]

Knowing the species and life stages of prey that predators consume is important for understanding the impacts that predation may have on prey populations, but traditional methods for determining diets often cannot provide sufficient detail. We combined data from two methods of scat analysis (DNA metabarcoding and morphological prey ID) to quantify the species and life stages of salmon (Oncorhynchus spp.) consumed by harbour seals (Phoca vitulina) in the Strait of Georgia, Canada, where juvenile Chinook (Oncorhynchus tshawytscha) and coho (Oncorhynchus kisutch) salmon survival is poor. Harbour seals primarily consumed adult salmon of lesser conservation concern in the fall (August-November): chum (Oncorhynchus keta: 18.4%), pink (Oncorhynchus gorbuscha: 12.6%), sockeye (Oncorhynchus nerka: 7.4%), Chinook (7.1%), and coho (1.8%). However, the opposite species trend occurred during the spring when seals preferred juvenile salmon of greater conservation concern (April-July): coho (2.9%), Chinook (2.9%), sockeye (2.5%), pink (1.4%), and chum (0.8%)--percentages that can equate to many individuals consumed. Our data suggest that harbour seals select juveniles of salmon species that out-migrate at ages >1 year and provide evidence of a potential causal relationship between harbour seal predation and juvenile salmon survival trends. Il importe de connaitre l'espece et l'etape du cycle biologique des proies que les predateurs consomment afin de comprendre les impacts que la predation peut avoir sur les populations de proies. Dans bien des cas, les methodes traditionnelles de determination du regime alimentaire ne peuvent toutefois fournir assez de details. Nous avons combine des donnees de deux methodes d'analyse d'excrements (meta-codes-barres d'ADN et identification morphologique des proies) pour quantifier l'espece et l'etape du cycle biologique de saumons (Oncorhynchus spp.) consommes par des phoques communs (Phoca vitulina) dans le detroit de Georgia (Canada), ou la survie des saumons quinnats (Oncorhynchus tshawytscha) et cohos (Oncorhynchus kisutch) juveniles est faible. Les donnees indiquent que, a l'automne (d'aout a novembre), les phoques communs consomment principalement des saumons adultes dont la conservation est moins preoccupante, a savoir des saumons ketas (Oncorhynchus keta : 18,4 %), roses (Oncorhynchus gorbuscha : 12,6%), rouges (Oncorhynchus nerka : 7,4%), quinnats (7,1%) et cohos (1,8%). Cependant, cette tendance est inversee au printemps (d'avril a juillet), alors que les phoques privilegient des saumons juveniles dont la conservation est plus preoccupante, a savoir des saumons cohos (2,9%), quinnats (2,9%), rouges (2,5%), roses (1,4%) et ketas (0,8%), ces pourcentages pouvant equivaloir a de nombreux individus consommes. Nos donnees laissent croire que les phoques communs choisissent des juveniles d'especes de saumon qui migrent vers la mer a des ages de plus d'un an et indiqueraient une possible relation de causalite entre la predation par les phoques communs et les tendances de survie des saumons juveniles. [Traduit par la Redaction], Introduction Predators can have different net effects on ecological communities depending on the life stage of prey they consume (Hastings 1983; 1988; Werner and Gilliam 1984). This is because prey [...]

ABSTRACT Major rocky intertidal predators in the northeast Pacific such as sea stars, whelks, and birds can consume foundation species such as mussels and thereby affect zonation patterns and diversity [...]

ABSTRACT The tropically associated black mangrove (Avicennia germinans) is experiencing a climate-induced range shift and expanding into salt marshes of northern Florida, southern Louisiana and most recently, Horn Island, MS. [...]

Predation on reptiles and amphibians by whooping cranes (Grus americanus) is widely reported, but all published data are anecdotal or based on singular observations, and mostly refer to isolated predation events. Some observers consider reptiles and amphibians to only be occasional prey items of whooping cranes. I report observations that show reptiles and amphibians to be an important food source for reintroduced whooping cranes in Louisiana, particularly in spring months, in that they might become a significant source of high-value food during the cranes' nesting season., INTRODUCTION Presence of amphibians and reptiles (hereafter A&Rs) in the diet of cranes (Gruidae) is known mostly from anecdotal reports and opportunistic observations (Archibald and Meine, 1996). For the whooping [...]

Abstract--Temperature data received post mortem in 2008-13 from 15 of 36 juvenile Steller sea lions (Eumetopias jubatus) that had been surgically implanted in 2005-11 with dual life history transmitters (LHX [...]

Trophic interactions in complex mesopelagic ecosystems are generally poorly understood, but tracing diet remains of predators provides key insights into these. In many cases, however, the prey remains obtained from predator stomachs are unidentifiable by visual inspection and identification depends on new molecular techniques. Here, we search for predators on larvae of the critically endangered European eel (Anguilla anguilla), a species which has shown a dramatic decline in recruitment to the stock. We sampled for predators among mesopelagic fishes using pelagic trawling in the known area of spawning and larval distribution of A. anguilla in the Sargasso Sea. We aimed at developing a species-specific quantitative PCR (qPCR) system, targeting the nd4-region of mitochondrial DNA (mtDNA), to search for eel remains in the stomachs of 17 mesopelagic fish taxa (62 specimens). Remains of A. anguilla were confirmed in 9.7% of all fish stomachs investigated, representing six species (Lampanyctus cuprarius, L. photonotus, Myctophum selenops, Notoscopelus caudispinosus, Melamphaes typhlops, and Chauliodus danae). Thus, our study documents that mesopelagic fishes in the Sargasso Sea to some extent predate the A. anguilla larvae, motivating further studies on upper-level trophic interactions in this oceanic ecosystem., Author(s): Mads Reinholdt Jensen [sup.1] [sup.2] , Steen Wilhelm Knudsen [sup.1] , Peter Munk [sup.3] , Philip Francis Thomsen [sup.2] , Peter Rask Møller [sup.1] Author Affiliations: (Aff1) 0000 0001 [...]