Prey Preference Research Articles

Shell colour, temperature, (micro)habitat structure and predator pressure affect the behaviour of Cepaea nemoralis

Although shell colour polymorphism of the land snail Cepaea nemoralis is a well-known phenomenon, proximate and ultimate factors driving its evolution remain uncertain. Polymorphic species show variation in behavioural responses to selective forces. Therefore, we estimated effects of various environmental factors (temperature, humidity, food availability, (micro)habitat structure and predatory pressure) on behavioural response (frequency of locomotion, climbing and hiding) of C. nemoralis morphs, in experimental and natural conditions. In the experimental part of study, the frequency of locomotion was negatively affected by temperature and the presence of food and positively influenced by the presence of light. Morphs significantly differed in behavioural responses to environmental variability. Pink mid-banded and yellow five-banded morphs climbed less often and hide in shelter more often than yellow and pink unbanded individuals when temperature was low and food was absent. Snails fed most often at moderate temperature compared to low and high temperatures. Field investigations partially confirmed differences among morphs in frequency of climbing, but not in terms of probability of hiding in sheltered sites. In natural colonies, temperature and (micro)habitat structure significantly affected frequency of climbing as well as hiding in shelter. Snails more often hid in sheltered sites where thrushes preyed on Cepaea. Tendency of unbanded morphs to climb trees may have evolved under avian predatory pressure as thrushes forage on a ground. Tendency of banded morphs to hide in sheltered sites may reflect prey preferences for cryptic background. The results implicate that differential behaviour of C. nemoralis morphs compensate for their morphological and physiological limitations of adaptation to habitat.

Black bear (Ursus americanus) and wolf (Canis spp.) summer diet composition and ungulate prey selectivity in Ontario, Canada

Understanding predator-prey dynamics is an important component of management strategy development for wildlife populations that are directly affected by predation. Ungulates often serve as a significant source of prey for many large mammal predators, and patterns of predation are known to influence population dynamics. Although black bear and wolf diets have been investigated extensively, prey preference has been less commonly examined, especially in analyses that take into account age class (i.e., juvenile and adult) of the ungulate prey. We examined black bear (Ursus americanus), wolf (Canis lupus), and hybrids (Canis spp.) prey preference in Ontario based on the availability of three ungulate species—elk (Cervus elaphus), moose (Alces alces), and white-tailed deer (Odocoileus virginianus). We analyzed the presence of prey items in black bear and wolf scats collected over 3 years by examining prey hair cuticular scale patterns. We applied correction factors to frequencies of occurrence of prey items found in predator scat and related diet composition to the availability of ungulates, determined by fecal pellet transect surveys. In addition, non-ungulate diet items were identified to obtain full diet composition profiles. We found that black bear diet consisted of more than 87% vegetation, and they were opportunistic, not selecting for any particular ungulate species in either adult or juvenile age class. Wolf diet was comprised mainly of ungulates (~ 73.2%), muskrat (Ondatra zibethica; ~ 8.5%), and beaver (Castor canadensis; ~ 14.6%), and although moose were at least 1.5 times more abundant then each of the other ungulate prey species in the study area, wolves preferred elk, using moose less than expected. Although we found black bear diet to be opportunistic during the summer, wolves in our study heavily utilized both juvenile and adult ungulates, however, among ungulate species, displayed preference for elk. The preference displayed by wolves provides insight that wildlife managers can use to guide further investigation and assist with the development of strategies to ensure continued elk reintroduction success, and moose and white-tailed deer population sustainability.

Seasonal food habits and prey selection of Amur tigers and Amur leopards in Northeast China

We analyzed the scats of Amur tigers and Amur leopards, and examined their annual and seasonal food habits in Northeast China to comprehend their coexistence. Wild boar had the highest annual and seasonal consumption frequencies by the tigers, while both roe deer and sika deer were mostly preyed by the leopards annually. The three species appeared to be the key preys in terms of high proportion of consumed biomass by the two felids. Our data also revealed numerous mid-sized carnivores and small mammals included in the two felids’ food list. We used the relative abundance and biomass density estimation in prey density estimation to calculate the prey preferences of tigers and leopards, and both methods confirmed that Amur tigers strongly preferred wild boar. However, preference estimations of Amur leopards were not consistant, or even opposite to one another from the two methods. The results of the study suggested that prey preference of predators is largely determined by body size of the prey species. Variation in diet composition of the two felids suggests that resource partitioning may contribute to their coexistence.

Geometric morphometric analysis of skull shape in the Accipitridae

Morphological adaptations for feeding are a conspicuous feature of avian evolution. Accipitrids exhibit a wide range of prey preferences. Skulls of 97 species which were assigned to seven dietary groups in the present study, were compared from the dorsal, lateral, and ventral views using geometric morphometrics. Landmarks were placed on the overall shape of cranium, bill, orbit, nostril, and attachment area for different jaw muscles. The results suggested considerable variations on the shape of bill and cranium, as well as the size of jaw closing muscles, by which can distinguish most of the groups. Scavengers were found to have a more slender and shallower skull, smaller orbits and longer maxilla whereas piscivores have a larger palatine. Mammalivores are characterized by reduced attachment area for the M. adductor mandibular externus superficialis, a relatively large palatine, long maxilla, and caudally positioned quadrate. Insectivores tend to have larger and more anteriorly oriented orbits, a relatively large attachment area for the M. adductor mandibular externus superficialis, and relatively broad and thin bills. Avivores are distinctive in their broad and protrudent caudal cranium. These morphological characteristics have some functional implications, and shed light on further biomechanical research. Moreover, phylogeny and size significantly contribute to skull shape variation.

Grazing impact and prey selectivity of picoplanktonic cells by mixotrophic flagellates in oligotrophic lakes

Mixotrophy by planktonic algae can dominate picoplankton predation in oligotrophic environments. We compared the grazing activity and prey preference of different mixotrophic taxa from natural communities of two oligotrophic shallow lakes (Escondido and Morenito) by performing eight laboratory grazing experiments using three different fluorescent prey (bacteria, picocyanobacteria, and picoeukaryotic algae). Eight taxa of mixotrophic flagellates (MF) corresponding to five different Classes, and two size categories of heterotrophic flagellates were distinguished. Chesson index showed that the ten identified protists preferred picocyanobacteria than bacteria, while picoeukaryotic algae were not ingested by any flagellate. In both lakes, MFs were responsible for ca. 80% of the picoplankton ingestion due to flagellates, and more than 50% of the total grazing impact when considering all flagellates, ciliates, and rotifers. Pseudopedinella spp. (Dictyochophyceae), Chrysochromulina parva (Haptophyceae), and Dinobryon divergens (Chrysophyceae) were the most important predators, while Plagioselmis lacustris (Cryptophyceae) and Chrysophyceae > 5 µm showed the lowest grazing rates. Overall, our findings support the idea of MF being the main picoplankton predators in oligotrophic systems. Besides, we also conclude that herbivory represents a key process in the mixotrophic carbon cycling in oligotrophic environments.

Hellbender Prey Preference Is Superseded by Native and Nonnative Prey Behavior

Abstract Long-term interactions often shape predator–prey relationships in the form of a co-evolutionary “arms race.” The arrival of nonnative species may disrupt these relationships by introducing novel behaviors that shift interactions in favor of one of the participants. Here we investigated the response of an imperiled native predator, the Eastern Hellbender (Cryptobranchus alleganiensis), to nonnative and native crayfish prey. Crayfish constitute an important prey item for hellbenders, and in the northern portion of its range where this research was conducted, the nonnative Rusty Crayfish (Orconectes rusticus) has become the dominant crayfish. The objective of this study was to determine prey choice and feeding success of hellbenders presented with native (Allegheny Crayfish; Orconectes obscurus) and nonnative (Rusty Crayfish) crayfish prey. We tested hellbender chemoreception in discriminating between the native and nonnative prey, analyzed behavioral interactions between hellbenders and crayfish du...

Predation on competing mussel species: Patterns of prey consumption and its potential role in species coexistence

Theoretical and empirical studies have demonstrated that predators can modulate coexistence between prey species and can modify broad patterns of community structure. Although the keystone predator effect (i.e., local coexistence and species diversity mediated by predator consumption) is commonly reported, negative effects of predators on species coexistence are also common. The balance depends critically on the asymmetry of competition, predator preferences for different prey, and the effective mortality rates exerted by predator populations on prey per capita growth rates. Here we studied the role of predation on two competing mussels, the dominant competitor Perumytilus purpuratus that dominates in abundance at most shores, and the subordinate Semimytilus algosus, which is common, but persistently abundant only at a smaller set of shores. We examined the potential for keystone effects by quantifying and evaluating the patterns of mussel consumption rates of sea star (Heliaster helianthus) and crab (Acanthocyclus gayi) predators in laboratory experiments, and under natural field conditions. Field sites with contrasting mussel abundance and recruitment (i.e., different local prey population growth rates) were chosen. Laboratory experiments showed that crabs would first consume Semimytilus over Perumytilus in mixed mussel clumps, while the larger sea star predators made no distinction between mussel species. Regardless of the order in which mussel species were first ingested, consumption rates of the two mussel species through the experiment were not different for either predator species. A similar temporal pattern was partly observable in the field through specific differences in the order of mussel consumption; however, experimental mussels of both species where consumed after the first two months of exposure to predators at both sites. Thus, in this system predation could not foster coexistence between mussel species and it may instead favor the occurrence of local extinction of the subordinate competitor, especially at sites where the smaller and more selective crab predators are relatively more abundant and recruitment of the subordinate species is low. Existing patterns of locally abundant Semimytilus beds are probably related to high site-specific recruitment rates of this species and should be further explored.

Dieta da coruja-buraqueira em ambientes abertos do sul do Brasil 1 Universidade

Athene cunicularia’s diet is composed of vertebrates and invertebrates, whose relative frequencies can change in space or time. We analyse habitat and temporal variation in the weight and the composition of prey in bird pellets. We collected 396 pellets from nine owl couples for six months and in three open habitats: near forest, far from forest, and urban. Mean pellet weight was 1.03 g. August showed pellets 15% heavier and March 22% lighter than average, differing from the other months. Regarding composition of prey, vertebrates occurred more in the pellets during June, July and August, while invertebrates showed higher frequency in summer months in open habitats far from forest. At the lower taxonomic level, we identified the presence of mammals, serpents, amphibians, birds, beetles, ants, spiders, grasshoppers, woodlice, molluscs and cockroaches in the pellets. The diet during winter in open habitats far from forest showed higher presence of mammals, while summer months in open habitats near forest and in urban habitats showed more hymenopterans. The results showed that A. cunicularia preys on a wide spectrum of prey, but we found some preference for specific prey depending on the season and on the open habitat types.Keywords: Atlantic Forest, pellets, spatial effect, time effect.

Immigrants and locally recruited birds differ in prey delivered to their offspring in blue tits and great tits

Natal dispersal is common in animals but the fitness cost of moving from the natal area is not well understood. One reason for a fitness cost is that foraging skills and prey preference learned early in life may be less efficient if the individual settles in a new, unfamiliar habitat. In a 4-year study, we found that immigrant parent blue tits, Cyanistes caeruleus, and great tits, Parus major, were inferior food providers compared to local recruits. In blue tits, immigrants provided smaller prey items than local recruits, whereas in great tits, the immigrants provided fewer green larvae, but relatively more brown larvae, to the offspring than local recruits. We also found that immigrant females laid later or smaller clutches than females locally recruited. The results are consistent with the hypothesis that natal dispersal carries costs related to the learning of foraging skills. However, alternative explanations are that the differences were caused by genetic and/or quality differences between the two groups of birds. We discuss various ecological and behavioural traits that may influence, and be influenced by, the mismatch of foraging between natal and breeding habitats. In altricial birds, yearlings will not have previous foraging experience during breeding and, in addition, immigrants will not have spent a long postfledging period in the new local habitat with their parents. If there are foraging-habitat mismatches as a result of dispersal, researchers should include natal origin in models of optimal foraging, time budgets, reproductive success and survival because performance may be directly related to the early learning environment rather than genetic differences.

Can species-specific prey responses to chemical cues explain prey susceptibility to predation?

The perception of danger represents an essential ability of prey for gaining an informational advantage over their natural enemies. Especially in complex environments or at night, animals strongly rely on chemoreception to avoid predators. The ability to recognize danger by chemical cues and subsequent adaptive responses to predation threats should generally increase prey survival. Recent findings suggest that European catfish (Silurus glanis) introduction induce changes in fish community and we tested whether the direction of change can be attributed to differences in chemical cue perception. We tested behavioral response to chemical cues using three species of freshwater fish common in European water: rudd (Scardinius erythrophthalmus), roach (Rutilus rutilus), and perch (Perca fluviatilis). Further, we conducted a prey selectivity experiment to evaluate the prey preferences of the European catfish. Roach exhibited the strongest reaction to chemical cues, rudd decreased use of refuge and perch did not alter any behavior in the experiment. These findings suggest that chemical cue perception might be behind community data change and we encourage collecting more community data of tested prey species before and after European catfish introduction to test the hypothesis. We conclude that used prey species can be used as a model species to verify whether chemical cue perception enhances prey survival.

DNA metabarcoding of nestling feces reveals provisioning of aquatic prey and resource partitioning among Neotropical migratory songbirds in a riparian habitat.

Riparian habitats are characterized by substantial flows of emergent aquatic insects that cross the stream-forest interface and provide an important source of prey for insectivorous birds. The increased availability of prey arising from aquatic subsidies attracts high densities of Neotropical migratory songbirds that are thought to exploit emergent aquatic insects as a nestling food resource; however, the prey preferences and diets of birds in these communities are only broadly understood. In this study, we utilized DNA metabarcoding to investigate the extent to which three syntopic species of migratory songbirds-Acadian Flycatcher, Louisiana Waterthrush, and Wood Thrush-breeding in Appalachian riparian habitats (Pennsylvania, USA) exploit and partition aquatic prey subsidies as a nestling food resource. Despite substantial differences in adult foraging strategies, nearly every nestling in this study consumed aquatic taxa, suggesting that aquatic subsidies are an important prey resource for Neotropical migrants nesting in riparian habitats. While our results revealed significant interspecific dietary niche divergence, the diets of Acadian Flycatcher and Wood Thrush nestlings were strikingly similar and exhibited significantly more overlap than expected. These results suggest that the dietary niches of Neotropical migrants with divergent foraging strategies may converge due to the opportunistic provisioning of non-limiting prey resources in riparian habitats. In addition to providing the first application of DNA metabarcoding to investigate diet in a community of Neotropical migrants, this study emphasizes the importance of aquatic subsidies in supporting breeding songbirds and improves our understanding of how anthropogenic disturbances to riparian habitats may negatively impact long-term avian conservation.

Insecticides alter prey choice of potential biocontrol agent Philodromus cespitum (Araneae, Philodromidae)

Even though pesticides can have various sublethal effects on behaviour of biocontrol agents, no study to date has investigated the effects of pesticides on the prey choice of generalist predators. Prey choice of generalist predators is among key factors determining the predation pressure they exert on pests, because it influences fitness of predators and consequently their densities and per capita capture rate. Here, we investigated the effect of Integro (a.i. methoxyfenozide) and SpinTor 480 Sc (a.i. spinosad) on prey choice and predatory activity of the spider Philodromus cespitum, which is known significantly to reduce hemipteran and dipteran pests in fruit orchards. We compared the prey preferences of philodromids between the psyllid pest Cacopsylla pyri (Hemiptera, Psyllidae) and beneficial Theridion sp. spiders in laboratory experiments. We found that both pesticides altered the prey preferences of philodromids. While the philodromids in a control treatment preferred theridiid spiders over the psyllid pest, philodromids in the pesticide treatments exhibited no significant prey preferences. The changes in prey preferences were caused by increased predation on the psyllids, while the predation on the theridiid remained similar. We suggest that the changes in prey preferences might theoretically be due to 1) impaired sensory systems, 2) altered taste, and/or 3) altered mobility. In combination with other studies finding reduced predation on fruit flies in P. cespitum after exposure to SpinTor, our results indicate that the sublethal effects of pesticides on predatory behaviour of generalist predators can depend on prey type and/or prey community composition.

Ba/Ca ratios in the non-spinose planktic foraminifer Neogloboquadrina dutertrei: Evidence for an organic aggregate microhabitat

Ba/Ca ratios in many non-spinose planktic foraminifera are markedly higher than those observed in spinose planktic species, but the cause for these high Ba/Ca ratios is not understood. A better understanding of this geochemical anomaly could provide insights into the habitat and/or controls over Ba incorporation in these species and expand their utility in paleoclimate research. In spinose species, shell Ba/Ca depends only on the Ba/Ca ratio of seawater. Proposed explanations for high non-spinose Ba/Ca include (1) the empirical partition coefficient, DBa, differs from the spinose species, (2) shell Ba varies with seawater temperature and pH, or (3) non-spinose foraminifers have a preference for prey that has elevated Ba. We performed laboratory culture experiments to determine DBa for the thermocline-dwelling non-spinose planktic foraminifer Neogloboquadrina dutertrei. We find that the Ba/Ca ratio of foraminiferal calcite secreted in the laboratory varies linearly with the Ba/Ca ratio of the seawater. The DBa for this species, 0.11 ± 0.008 (2SE; 95% CL), is similar to the DBa for spinose species (0.13 ± 0.004, 2SE; 95% CL). As in spinose species, the Ba/Ca ratio of cultured specimens of N. dutertrei is not influenced by culture temperature (12–22 °C) or seawater pHNBS (range 7.8–8.3). However, the Ba/Ca ratio of individual plankton-tow N. dutertrei specimens that completed their lifecycle in the ocean exceeds the Ba/Ca ratio of cultured specimens by up to three orders of magnitude. It is unlikely this difference between cultured specimens and ocean-grown specimens is due to seawater [Ba] variability, since seawater Ba/Ca ratios calculated using our DBa are much higher than exist in the ocean. Rather, we suggest that elevated shell Ba/Ca in plankton tow and fossil N. dutertrei is due to calcification in the microenvironment of marine organic aggregates such as marine snow, where [Ba] is elevated as a result of Ba release from biogenic particulates.

Giraffe Mother-Calf Relationships in the Miombo Woodland of Katavi National Park, Tanzania

Both predator pressure and habitat type influence mother-offspring relationship. Giraffe's herd size and herd composition can be influenced by these two environmental factors. We sought to uncover whether predator pressure and habitat type also have an impact on giraffe mother-calf proximity and time spent together. We studied giraffe mother-calf relationships to compare mother-calf dyadic relationships in dense woodland with those reported in open woodlands. We collected data from three calves (within the first six months after birth) and their mothers at the miombo woodland of Katavi National Park, Tanzania. We observed the mother giraffe leaving or staying with her calf and recorded the initiation and termination of each of these behaviors. We found that the duration of both states was rarely more than 1 h. We never observed a mother leaving her calf for more than 1.5 h, as has been reported in open woodlands. We found that in calf-calf dyads, giraffe were more likely to maintain closer proximity to one another than in female-calf dyads. Our results suggest that the flexibility recorded in mother-calf social relationships is influenced by both social and ecological factors, differing to some extent in tree density, food preference during nursing, and predators' prey preference.

What determines prey selection in owls? Roles of prey traits, prey class, environmental variables, and taxonomic specialization.

Ecological theory suggests that prey size should increase with predator size, but this trend may be masked by other factors affecting prey selection, such as environmental constraints or specific prey preferences of predator species. Owls are an ideal case study for exploring how predator body size affects prey selection in the presence of other factors due to the ease of analyzing their diets from owl pellets and their widespread distributions, allowing interspecific comparisons between variable habitats. Here, we analyze various dimensions of prey resource selection among owls, including prey size, taxonomy (i.e., whether or not particular taxa are favored regardless of their size), and prey traits (movement type, social structure, activity pattern, and diet). We collected pellets of five sympatric owl species (Athene noctua, Tyto alba, Asio otus, Strix aluco, and Bubo bubo) from 78 sites across the Mediterranean Levant. Prey intake was compared between sites, with various environmental variables and owl species as predictors of abundance. Despite significant environmental impacts on prey intake, some key patterns emerge among owl species studied. Owls select prey by predator body size: Larger owls tend to feed on wider ranges of prey sizes, leading to higher means. In addition, guild members show both specialization and generalism in terms of prey taxa, sometimes in contrast with the expectations of the predator–prey body size hypothesis. Our results suggest that while predator body size is an important factor in prey selection, taxon specialization by predator species also has considerable impact.

Harmonia axyridis Does Not Have Obvious Fitness Gain and Preference to the Red Morph of Acyrthosiphon pisum: A Case Study on a Laboratory Strain

Prey selection was assumed to be a vital strategy to maximize the fitness of predators. Visual cues are important for predators to locate a prey, and several species of lady beetles prefer the red morph Acyrthosiphon pisum rather than the green morph in empty containers with different colors. However, the preference of a predator on different color morphs of prey on green plant leaves and the relationship between the fitness of the predator that feeds on the red and green color morphs of A. pisum have not been revealed. In this study, two colonies of the multicolored Asian lady beetle, Harmonia axyridis, a generalist predator, fed on a red morph and a green morph of A. pisum (indicated as RA-Har and GA-Har, respectively) were used to determine their prey preferences on the two morphs of A. pisum on leaf discs. The fourth instars and newly emerged adults of H. axyridis that fed on the two aphid morphs did not show any significant prey preference, except that GA-Har males consumed significantly more green morph than red morph. The fitness of RA-Har and GA-Har, including larval development and body weights of the fourth instars and the newly emerged female adults were not significantly different, and so were the predation capability and fecundity. However, RA-Har had significantly higher larval hatch rate than GA-Har, and tended to produce more eggs on cage walls or plant pots than on broad bean leaves in the cage assays. Our results provide evidences that H. axyridis did not prefer either morph of A. pisum, and also did not show significant effect on fitness. We hope that results from this study will stimulate more studies to reveal the mechanism of colored prey preference of predators.

Dietary changes in predators and scavengers in a nocturnally illuminated riparian ecosystem

Aquatic and terrestrial ecosystems are linked by fluxes of carbon and nutrients in riparian areas. Processes that alter these fluxes may therefore change the diet and composition of consumer communities. We used stable carbon isotope (δ13C) analyses to test whether the increased abundance of aquatic prey observed in a previous study led to a dietary shift in riparian consumers in areas illuminated by artificial light at night (ALAN). We measured the contribution of aquatic‐derived carbon to diets in riparian arthropods in experimentally lit and unlit sites along an agricultural drainage ditch in northern Germany. The δ13C signature of the spider Pachygnatha clercki (Tetragnathidae) was 0.7‰ lower in the ALAN‐illuminated site in summer, indicating a greater assimilation of aquatic prey. Bayesian mixing models also supported higher intake of aquatic prey under ALAN in spring (34% versus 21%). In contrast, isotopic signatures for P. clercki (0.3‰) and Pardosa prativaga (0.7‰) indicated a preference for terrestrial prey in the illuminated site in spring. Terrestrial prey intake increased in spring for P. clercki under ALAN (from 70% to 74%) and in spring and autumn for P. prativaga (from 68% to 77% and from 67% to 72%) and Opiliones (from 68% to 72%; 68% to 75%). This was despite most of the available prey (up to 80%) being aquatic in origin. We conclude that ALAN changed the diet of riparian secondary consumers by increasing the density of both aquatic and terrestrial prey. Dietary changes were species‐ and season‐specific, indicating that the effects of ALAN may interact with phenology and feeding strategy. Because streetlights can occur in high density near freshwaters, ALAN may have widespread effects on aquatic–terrestrial ecosystem linkages.

Feeding ecology of the common dolphin (Delphinus delphis) in Western Iberian waters: has the decline in sardine (Sardina pilchardus) affected dolphin diet?

Predator diet is expected to respond to changes in the abundance of important prey items. We investigated whether common dolphin diet has changed with changes in the pelagic fish community off the Iberian Peninsula in recent years, in particular with reference to the decline of sardine (Sardina pilchardus) and the increase of Atlantic chub mackerel (Scomber colias) and scads (Trachurus spp.), and estimated how much fish was removed by common dolphins in coastal waters of mainland Portugal. Based on analysis of stomach contents of stranded animals from 2010 to 2013 (n = 150), we related diet composition to sardine abundance, dolphin size and sex, season and region. Despite the decline in sardine stocks in recent years, sardines were the most important prey of common dolphins, as was previously reported in the 1990s, followed by chub mackerel and scads. However, small sardines have disappeared from the diet, consistent with recent poor recruitment to the stock. The relative importance of these pelagic species in the diet increased significantly with increasing dolphin length. The dietary importance of chub mackerel also varied regionally, with higher intake on the southern coast. Finally, we compared the estimated biomass of fish removed by dolphins with that taken by fisheries. We found that even with the severe quota restrictions on sardine catches, total biomass removed by fisheries was over five times greater than the estimated removal by common dolphins. Our results confirm the previously reported preference for energy-rich prey, especially sardine, suggesting that common dolphins in Portuguese waters specialise in feeding on this species.

Determining live prey preferences of larval ornamental marine fish utilizing fluorescent microspheres

As the popularity of marine aquaria grows, the potential exists for increased harvest of marine ornamental fishes and invertebrates from the oceans around the world. Aquaculture may be an alternative source to wild capture fisheries if commercial production protocols can be developed for species of interest, however numerous impediments must be overcome. Experiments were conducted on the reef butterflyfish (Chaetodon sedentarius), Pacific blue tang (Paracanthurus hepatus), African moony (Monodactylus sebae) and golden trevally (Gnathanodon speciosus) to evaluate and define prey preferences at first feeding among the rotifer, Brachionus plicatiilis, the copepod, Parvocalanus crassirostris, and the ciliate Euplotes sp., by marking each prey with a different colored fluorescent microsphere. Prey preferences observed at the larval first feeding stage were species specific. Pacific blue tang larvae preferred rotifers above ciliates, and ciliates above copepod nauplii. African moony larvae preferred ciliates and nauplii equally over rotifers. Reef butterflyfish larvae preferred ciliates over rotifers and rotifers over nauplii. Golden trevally larvae preferred nauplii over ciliates, and ciliates over rotifers. Take together these data provide critical information which may aid in development of feeding protocols for marine ornamental species.

Trophic signatures of seabirds suggest shifts in oceanic ecosystems.

Pelagic ecosystems are dynamic ocean regions whose immense natural capital is affected by climate change, pollution, and commercial fisheries. Trophic level-based indicators derived from fishery catch data may reveal the food web status of these systems, but the utility of these metrics has been debated because of targeting bias in fisheries catch. We analyze a unique, fishery-independent data set of North Pacific seabird tissues to inform ecosystem trends over 13 decades (1890s to 2010s). Trophic position declined broadly in five of eight species sampled, indicating a long-term shift from higher-trophic level to lower-trophic level prey. No species increased their trophic position. Given species prey preferences, Bayesian diet reconstructions suggest a shift from fishes to squids, a result consistent with both catch reports and ecosystem models. Machine learning models further reveal that trophic position trends have a complex set of drivers including climate, commercial fisheries, and ecomorphology. Our results show that multiple species of fish-consuming seabirds may track the complex changes occurring in marine ecosystems.