Prey Categories Research Articles

Ontogeny in Feeding Behaviour of Chocolate Mahseer, Neolissocheilus hexagonolepis in Captive Environment

The paper embodies to determine the sequential pattern of feeding behaviour of chocolate mahseer in pond condition. The diet composition of different developmental stages of Neolissochilus hexagonolepis during fry, fingerling and juvenile were determined based on the analysis of 98 specimens (17 fries, 43 fingerlings and 38 juveniles), collected from the pond environment of Mahseer Hatchery Complex of ICAR- DCFR, Bhimtal. Zooplanktons were the most dominant prey category (%F = 129.38, %N = 45.73) in fry, while phytoplankton's were the most dominant prey items in fingerling (%F = 139.59, %N = 63.67) and juvenile (%F = 233.88, %N = 70.84). The results of the study revealed that fry and juvenile seems to have a higher feeding activity in relation to fingerling and the diet of the fish varies with different stages of development. Hence, the fry are carni-omnivore while fingerlings and juveniles are herbi - omnivore.

Feeding preferences and responses to prey in insular neonatal Florida cottonmouth snakes

AbstractCottonmouth snakes residing on certain Gulf coastal islands of Florida feed largely by scavenging fish that are dropped or regurgitated by colonial nesting birds. Because of the relative isolation of these snakes and their long association with bird rookeries, it is of interest to inquire whether snakes exhibit any dietary preference, or whether consumption of fish remains strictly opportunistic. Here we examine whether there are differences in prey acceptance between insular and mainland naive, neonatal cottonmouths, and whether insular snakes develop preferences for particular prey items. We report that both insular and mainland snakes accept a range of similar prey items including fish, mice and lizards. We also report that naive insular neonates tend to accept fish earlier following birth than they accept mammalian prey. When naive neonates are fed only a single specific prey item, fish or mammal, during the first year of life, individuals preferentially follow odors that are associated with the sole dietary prey to which they have been conditioned. However, following conditioning on either prey category (fish or mice) these snakes also eat the non‐conditioned prey (mice or fish, respectively) when presented with the opportunity. Our results suggest that young cottonmouths might adjust foraging strategy to match prey availability, while retaining flexibility in feeding behavior based in inherent dietary breadth. Thus, the insular population can occupy a broad trophic niche while fine‐tuning foraging behaviors to match the local conditions.

A comparison of ringed and bearded seal diet, condition and productivity between historical (1975–1984) and recent (2003–2012) periods in the Alaskan Bering and Chukchi seas

Reductions in summer sea ice in the Chukchi and Beaufort seas are expected to affect what has been an ice-adapted marine food web in the Pacific Arctic. To determine whether recent decreases in sea ice have affected ice-associated marine predators (i.e., ringed, Pusa hispida, and bearded seals, Erignathus barbatus) in the Bering and Chukchi seas we compared diet, body condition, growth, productivity, and the proportion of pups harvested (an index of weaning success) for seals of each species harvested by 11 Alaskan villages during two periods; a historical (1975–1984) and a recent period (2003–2012). We also examined how changes in indices of seal health may be correlated with the reduction of sea ice characteristic of the recent period. For ringed seals ⩾1year of age, the % frequency of occurrence (%FO) of Arctic cod (Boreogadus saida), walleye pollock (Gadus chalcogramma), rainbow smelt (Osmerus mordax), and Pacific herring (Clupea pallasi) increased from the historic to the recent period, while the %FO of invertebrates decreased for both pups and seals ⩾1year of age. For bearded seals ⩾1year of age, the %FO of Arctic cod, pricklebacks, and flatfish increased during the recent period, while the %FO of saffron cod (Eleginus gracilis) decreased for pups. Although invertebrates did not change overall for either age class, decreases occurred in 10 of 24 specific prey categories, for bearded seals ⩾1year of age; only echiurids increased. The %FO of gastropods and bivalves increased for pups while isopods and one species of shrimp and crab decreased in occurrence.During the recent period ringed seals grew faster, had thicker blubber, had no change in pregnancy rate, matured 2years earlier, and a larger proportion of pups was harvested than during the historical period. Correlations with spring ice concentration showed that the growth and blubber thickness of seals ⩾1year of age, blubber thickness of pups, and the proportion of pups in the harvest all declined for ringed seals when ice concentrations were higher in the historic period. However, only the correlations between high ice concentrations and growth of ringed seals ⩾1year of age and the proportion of ringed seal pups in the harvest were statistically significant. Although growth of bearded seals ⩾1year of age was slower during the recent period, it was similar to the average over the entire time series, and blubber thickness increased. Pup growth and blubber thickness did not change between periods. There was no change in pregnancy rate, but females matured 1.6years earlier, and a larger proportion of pups were harvested. Correlations with spring ice concentration showed that the growth of seals ⩾1year of age, the growth of pups, blubber thickness of pups, and proportion of pups in the harvest also declined for bearded seals when sea ice concentrations were higher. However, no relationships between bearded seals and sea ice were statistically significant. Overall, our results suggest that ringed seals in the Alaskan Bering and Chukchi seas have adjusted to changes in diet, are growing faster and possibly weaning more pups in the recent compared to the historic period. These patterns are less evident for bearded seals. Although the ringed and bearded seals we examined have not exhibited the declines in body condition, growth, or reproduction observed in other populations, continued monitoring and comparison among seal populations is vital to understanding the effects of changing environmental conditions in the Pacific Arctic region.

Structure of a Caatinga anuran assemblage in Northeastern Brazil

Based on data on diet and microhabitat use, we investigated the importance of current (ecological) and historical factors (phylogenetic) in the organization of an anuran assemblage in temporary ponds in a Caatinga area in Northeastern Brazil. The objective of this study was to verify how diet and microhabitat use influence the community structure, and their determinants. Niche breadth based on microhabitat use was relatively low for all species; thus, we also observed a spatial segregation between Hylidae and other families. The closely related species exhibit a more similar diet; the main prey categories used by Caatinga anurans were Coleoptera, insect larvae and Formicidae. The pseudo-community analysis based on diet and microhabitat use revealed that the observed niche overlap did not differ statistically from random, indicating a lack of detectable competition for these resources. The Canonical Phylogenetic Ordination (CPO) analyses revealed no significant phylogenetic effect on the assemblage, neither for diet nor for microhabitat use. Results suggest that predation and hydroperiod may be the most important factors in determining assemblage patterns, but more studies are needed to support this hypothesis. Keywords: community, Amphibia, ecological factors, historical factors.

Diet and reproductive aspects of the exotic gecko gehyra mutilata (Wiegmann, 1834) (Sauria: Gekkonidae) in the urban area of Chapala, Jalisco, Mexico

We studied the diet and described some reproductiveaspects (body size, clutch size, size and egg volume, and nesting site) of the exotic gecko Gehyra mutilata in the urban area from Chapala, Jalisco, Mexico, during a period of nine months (April-December, 2013). A total of 113 adult individuals were captured, where 101 revealed to have stomach contents. We found a total of 1,563 food items, which were identified and grouped into 13 prey categories: Araneae, Blattodea, Coleoptera, Dermaptera, Diptera, Gastropoda, Hemiptera, Hymenoptera: Formicidae and Non-Formicidae, Isopoda, Lepidoptera, Orthoptera, Squamata (Gekkonidae) and Trichoptera. Diptera (Nematocera) was the most important food category in abundance (91.6%), relative frequency (34.2%), volume (68.8%), and relative importance (94.8%). Other uncountable food items as plant material and eggshell remains were present in the diet. The number of prey per stomach were between 1 to 140, with a mean of 15.5 ± 25.56, the prey volume mean was 0.29 ± 0.76 ml, with a range of <0.01 – 2.90 ml. Males had fewerprey items in their stomachs than females, but no significant differences were found between sexes. Diet diversity (1D) between males and females was evaluated, which was similar with almost two effective food categories for both sexes. The trophic niche overlap between sexes showed a high numeric and volumetric similarity in their diet. Snout-vent length did not significantly differ between males and adult females. The mean clutch size was 2 eggs, even though the nesting site can be composed of larger egg clusters. The nesting sites consisted on holes, crevices and inside electric installations on building walls. The mean egg length was 10.47 ± 0.541, with a mean width of 8.40 ± 0.256, while the mean volume was 387.92 ± 43.297 mm3. The present study suggests that the opportunist habits of G. mutilata are a determinant factor on its diet composition within the urban area of Chapala.

Feeding ecology of the common sun skink, Eutropis multifasciata (Reptilia: Squamata: Scincidae), in the plains of central Vietnam

We studied the feeding ecology of Eutropis multifasciata in the tropical plains of central Vietnam to understand better the foraging mode, spatiotemporal and sexual variation in dietary composition, and rarefaction curves of prey-taxon richness for males and females. Stomach contents (n = 161) were collected from October 2013 to May 2014 using a nonlethal stomach-flushing technique. A total of 680 food items (624 animal items and 56 plant items) was found in 161 stomachs of skinks, representing 19 unique animal categories. We found that the diet of E. multifasciata is composed mainly of small, sedentary and clumped prey and that this skink specialises on spiders, insect larvae, snails, grasshoppers and crickets (with a combined importance index of 60%). Dietary composition, prey size and total prey volume in E. multifasciata changed between dry and rainy seasons and among regions. The total volume of food items consumed by males was larger than that of females, and the diversity and evenness index of prey categories were larger in males than in females. However, using rarefaction curves revealed that females have the higher prey-taxon richness after points between 130 and 140 prey items for frequency, and between 160 and 170 prey items for number of items, and the differences were not statistically significant. The foraging behaviour of E. multifasciata best fits a ‘widely foraging’ model.

Consumption by marine mammals on the Northeast U.S. continental shelf

The economic and ecological impacts of fish consumption by marine mammals, the associated interactions with commercial fish stocks, and the forage demands of these marine mammal populations are largely unknown. Consumption estimates are often either data deficient or not fully evaluated in a rigorous, quantitative manner. Although consumption estimates exist for the Northeast United States (NEUS) Large Marine Ecosystem, there is considerable uncertainty in those estimates. We examined consumption estimates for 12 marine mammal species inhabiting the regional ecosystem. We used sensitivity analyses to examine metabolically driven daily individual consumption rates, resulting in a suite of feasible parameter-pair ranges for each of three taxonomic groups: mysticetes, odontocetes, and pinnipeds. We expanded daily individual consumption to annual consumption based on abundance estimates of marine mammals found on the NEUS continental shelf coupled with estimates of annual residence time for each species. To examine consumptive removals for specific prey, diet compositions were summarized into major prey categories, and predatory removals by marine mammal species as well as for total marine mammal consumption were estimated for each prey taxa. Bounds on consumption estimates for each marine mammal species were determined using Monte Carlo resampling simulations. Our results suggest that consumption for these 12 marine mammal species combined may be similar in magnitude to commercial fishery landings for small pelagic and groundfish prey groups. Consumption by marine mammals warrants consideration both as a source of mortality in assessments of prey-stocks, and to determine marine mammal forage demands in ecosystem assessment models. The approach that we present represents a rigorous, quantitative method to scope the bounds of the biomass that marine mammals are expected to consume, and is appropriate for use in other ecosystems where the interaction between marine mammals and commercial fisheries is thought to be prominent.

Feeding ecology of Long-eared Owls in winter: an urban perspective

Capsule Although considered as a specialist predator of Microtus voles, the Long-eared Owl Asio otus may adapt its diet according to the local prey availability. We reviewed the diet of this nocturnal raptor in urban environments during the winter, using studies which reported the ingested biomass relating to different prey categories and so energy intake could be considered. The species was confirmed to feed mainly on Microtus, but in some area rats dominated the ingested biomass.

Trophic Niche and Feeding Strategy of the White Stork (Ciconia ciconia) during different Phases of the Breeding Season

Assessing feeding conditions and variations of diet composition over the breeding season is of great help in the understanding of the ecological niche of species. In meeting this aim, the White Stork's ( Ciconia ciconia) diet was studied based on the analysis of 87 regurgitation pellets collected from Batna (Northeast Algeria). A set of 2138 prey-items were identified and classified into 61 different prey-species belonging to seven classes, 13 orders, 29 families and 51 genera. The White Stork has a diverse diet (food niche breadth, FNB = 14.5, Shannon index H’ = 4.4 bits), mainly composed of arthropods, of which 94% of prey-items are insects that represent 8% of total prey biomass. The White Stork constantly fed on the remains of chicken foraged from rubbish dumps (biomass = 68.74%) and small mammals (biomass = 14.41%) as these prey categories constitute a source of high energy, particularly during the period of chick rearing. GLMs applied for diet characteristics revealed a significant variation in numbers of prey individuals between breeding phenological stages. While variations of other diet parameters (biomass, species richness, FNB, H’, H'max and evenness) were not statistically influenced by breeding phenology. All diet characteristics were significantly correlated with the period of chick development, which is the key period for breeding success; suggesting an increase in parental investment and feeding effort. Our findings suggest that the White Stork performs a balance in order to satisfy its food requirements by compensating reciprocally between intake of prey numbers and their biomass regardless of the phenological stage of reproduction.

Diet of adult and juvenile golden jackals (Canis aureus) during cubs` dependency stage

Golden jackal populations in the Balkans are increasing and spreading its range. Nowadays vagrant specimens are reaching the northern parts of Europe. As one of the prerequisites for actual population increase is a solid food base, we examined the feeding habits of adult and juvenile jackals in Serbia in the period of cub dependency stage. Stomach content of 49 adults and 28 cubs from period July-October were analyzed. Juvenile jackals had less diverse diet than the adults, represented with eight food categories. During this part of the year, jackals of both age categories were mostly consuming small mammals. Moreover, they were the main prey category in the diet of juveniles (49.82 %B and 32.08 %O). No game species were recorded in the diet of juvenile jackals. During their first summer and autumn, jackal cubs already manifest the opportunistic feeding behavior. They take advantage of easily accessible food sources such as fruit and slaughter leftovers from domestic ungulates and poultry.

Response to habitat modification by foraging Dark-chanting Goshawks Melierax metabates in a West African savanna

SummaryAnthropogenic habitat alteration has probably contributed significantly to the decrease of raptor populations in West African savannas. To evaluate the impact of habitat degradation on foraging by sedentary Afrotropical raptors, we investigated the differences in microhabitat selection, foraging effort and energy returns between Dark-chanting Goshawks Melierax metabates inhabiting natural and transformed savannas in Cameroon. We expected that the agro-ecosystems in the transformed savannas have become unprofitable for Dark-chanting Goshawks due to scarcity of food resources. In both savanna types we radio-tracked six mated, adult males during the non-breeding season and determined foraging effort, by time spent at each perch and distance covered between perches, and energy intake through estimation of the energy value of prey items. Goshawks in natural habitats had smaller home-ranges and exploited their range more intensively than Goshawks in transformed habitats. In both natural and transformed habitats, Goshawks selected foraging patches with comparatively tall trees, underlining their importance to foraging Goshawks. The extent of shrub and herbaceous layer cover, agriculture cover, and tree density were other important predictors of foraging patch use, but their importance differed between habitats. The extent of shrub, herbaceous layer and agriculture cover were positively associated with foraging patch use in transformed habitats, suggesting that cultivated fields and ground vegetation support important prey resources for Goshawks in agro-ecosystems. The composition of broad prey categories to the diet, foraging effort and returns were comparable between habitats. However, we found indications that the proportion of heavy-bodied lizard species among reptile prey items was higher in natural than transformed habitats, whereas on average smaller lizards were more commonly caught in the latter. Mean herbaceous layer height and tree density within home ranges, both higher in natural habitat, were negatively related to prey capture rates. Tree clearance and livestock grazing thus favored greater prey capture rates in transformed habitat, offsetting a lower meal energy value compared to natural habitat. We conclude that foraging Dark-chanting Goshawks may cope with moderate land transformation, but practices focused on conservation of tall trees and ground vegetation cover would be beneficial by maintaining important prey resources and their exploitability under growing land pressure.

Seasonal dietary shifts and food resource exploitation by the hog badger (Arctonyx collaris) in a Chinese subtropical forest

Spatial and temporal fluctuations in the availability of food resources can affect adaptive foraging strategies substantially, with the potential to promote temporal dietary switching and specialisation among generalist carnivores. To understand this relationship better at the causal level, we examined spatial and temporal variation in diet composition and diversity in the hitherto little-known hog badger (Arctonyx collaris), in comparison to the environmental abundance of principal food resources, in a subtropical forest of central China. Here, hog badgers fed predominantly on earthworms and fruits, complemented with arthropod imagoes and invertebrate larvae, whereas vertebrate prey categories (mammals, birds and reptiles) were consumed infrequently. We observed strong seasonal variation in the consumption of different food categories. Earthworms predominated during spring, fruits in autumn, and earthworms, complemented by arthropods, in summer, with hog badgers apparently hibernating in winter. Fluctuation in dietary preferences between seasons and habitats correlated only partially with environmental food abundance; in autumn, when fruit abundance peaked, and despite a concomitant peak in earthworm abundance, hog badgers exhibited a dietary shift, indicating a preference for fruit, over earthworms. This resulted in autumnal minima in seasonal food niche breadth and evenness values. We conclude that, in this region, hog badgers exhibited a generalist diet but switched between food categories in response to changes in environmental seasonal abundance.

Trophic Ecology ofPhysalaemus ephippifer(Anura, Leptodactylidae) in Eastern Amazonia

Abstract One of the main aspects of natural history is trophic ecology, which affects survival and population size. In the present study, we registered the contribution of prey types to the diet of Physalaemus ephippifer and tested for differences in diet according to sex and season (rainy and dry) of three populations of P. ephippifer in eastern Amazonia. We analyzed frequency of occurrence, trophic amplitude, feeding overlap, and food importance index for each prey category. We analyzed 102 specimens (69 males and 33 females) and observed that the most important prey categories were termites and ants. The most important prey category for females during rainy season included coleopteran larvae, whereas during dry season the most important prey category was termites. In both seasons, the most important prey category for males was ants. We did not observe any seasonal or sexual variation in the diet of P. ephippifer. On the other hand, during the rainy season, coleopteran larvae and termites were the most ...

Sexual Dimorphism and Diet ofPseudis tocantins(Anura, Hylidae, Pseudae)

Abstract. The genus Pseudis (Hylidae) includes aquatic frogs distributed throughout South America east of the Andes. Few papers have been published on the ecology of these species, despite the great interest their gigantic larvae raise among herpetologists. Pseudis tocantins has a widespread distribution along the Tocantins-Araguaia hydrographic basin in Brazil and virtually nothing has been published about its natural history and ecology. The present work aimed to evaluate, based on 159 specimens from 13 populations, sexual dimorphism in size and shape and diet composition of P. tocantins along most of its known distribution. Females were significantly larger than males and body shape differed significantly between sexes, with tibia length and tympanum diameter as the variables contributing the most to this difference. We found 13 prey categories in frog’s stomachs, with Araneae, Odonata, and Orthoptera being the most important items, respectively. Aquatic animals were also part of the species diet (even...

Trophic interactions of common elasmobranchs in deep-sea communities of the Gulf of Mexico revealed through stable isotope and stomach content analysis

Deep-water sharks are abundant and widely distributed in the northern and eastern Gulf of Mexico. As mid- and upper-level consumers that can range widely, sharks likely are important components of deep-sea communities and their trophic interactions may serve as system-wide baselines that could be used to monitor the overall health of these communities. We investigated the trophic interactions of deep-sea sharks using a combination of stable isotope (δ13C and δ15N) and stomach content analyses. Two hundred thirty-two muscle samples were collected from elasmobranchs captured off the bottom at depths between 200 and 1100m along the northern slope (NGS) and the west Florida slope (WFS) of the Gulf of Mexico during 2011 and 2012. Although we detected some spatial, temporal, and interspecific variation in apparent trophic positions based on stable isotopes, there was considerable isotopic overlap among species, between locations, and through time. Overall δ15N values in the NGS region were higher than in the WFS. The δ15N values also increased between April 2011 and 2012 in the NGS, but not the WFS, within Squalus cf. mitsukurii. We found that stable isotope values of S. cf. mitsukurii, the most commonly captured elasmobranch, varied between sample regions, through time, and also with sex and size. Stomach content analysis (n=105) suggested relatively similar diets at the level of broad taxonomic categories of prey among the taxa with sufficient sample sizes. We did not detect a relationship between body size and relative trophic levels inferred from δ15N, but patterns within several species suggest increasing trophic levels with increasing size. Both δ13C and δ15N values suggest a substantial degree of overlap among most deep-water shark species. This study provides the first characterization of the trophic interactions of deep-sea sharks in the Gulf of Mexico and establishes system baselines for future investigations.

Food habit of the endangered yellow-spotted newt Neurergus microspilotus (Caudata, Salamandridae) in Kavat Stream, western Iran

Diversity and abundance of macroinvertebrate fauna were simultaneously determined in selected benthic samples and in regurgitated stomach contents in Neurergus microspilotus in Kavat Stream (western Iran) during April and May 2012. The aim of this study was to determine the degree of reliance of this species to benthic macroinvertebrates during their reproductive season in aquatic habitat. Twenty-one taxa of macroinvertebrates were identified in the benthic samples while 19 taxa were presented in the regurgitated stomach contents. Data obtained from benthic samples showed that the most abundant macroinvertebrate groups included Lumbricidae (27.2%), Mycetophilidae (20.06%), Gammaridae (12.19%), and Plananariidae (9.3%). Data obtained from 45 stomach contents indicated that on average the highest importance values combining number, frequency, and volume for prey categories consumed included Mycetophilidae (14.03%), Baetidae (13.68%), Corbiculidae (12.57%), Gammaridae (10.8%), and Lumbricidae (9.34%). N. microspilotus also consumed small stones, plant materials, and their own eggs (0.91%). The analysis of selectivity in feeding using Ivlev’s index showed that the prey taxa that appeared to be preferred (E i > 0.5) were generally rare in the environment. Comparison between benthic macroinvertebrates and those taken by the newt demonstrates that although high similarity (Sorenson index of 78.94%) exists between the two communities, the dominance of the items taken by N. microspilotus (Simpson index = 0.32) is higher than that of the benthic community (Simpson index = 0.20) indicating that the newts rely on fewer number of species with higher proportion of individual prey items. Feeding habits of 45 N. microspilotus have shown that the newts rely extensively on Mycetophilidae, Baetidae, Corbiculidae, Gammaridae, and Lumbricidae as important food items for N. microspilotus.

The conflict between cheetahs and humans on Namibian farmland elucidated by stable isotope diet analysis.

Large areas of Namibia are covered by farmland, which is also used by game and predator species. Because it can cause conflicts with farmers when predators, such as cheetahs (Acinonyx jubatus), hunt livestock, we assessed whether livestock constitutes a significant part of the cheetah diet by analysing the stable isotope composition of blood and tissue samples of cheetahs and their potential prey species. According to isotopic similarities, we defined three isotopic categories of potential prey: members of a C4 food web with high δ15N values (gemsbok, cattle, springhare and guinea fowl) and those with low δ15N values (hartebeest, warthog), and members of a C3 food web, namely browsers (eland, kudu, springbok, steenbok and scrub hare). We quantified the trophic discrimination of heavy isotopes in cheetah muscle in 9 captive individuals and measured an enrichment for 15N (3.2‰) but not for 13C in relation to food. We captured 53 free-ranging cheetahs of which 23 were members of groups. Cheetahs of the same group were isotopically distinct from members of other groups, indicating that group members shared their prey. Solitary males (n = 21) and males in a bachelor groups (n = 11) fed mostly on hartebeest and warthogs, followed by browsers in case of solitary males, and by grazers with high δ15N values in case of bachelor groups. Female cheetahs (n = 9) predominantly fed on browsers and used also hartebeest and warthogs. Mixing models suggested that the isotopic prey category that included cattle was only important, if at all, for males living in bachelor groups. Stable isotope analysis of fur, muscle, red blood cells and blood plasma in 9 free-ranging cheetahs identified most individuals as isotopic specialists, focussing on isotopically distinct prey categories as their food.

Prey density in non-breeding areas affects adult survival of black-legged kittiwakes Rissa tridactyla

In migratory birds, environmental conditions in both breeding and non-breeding areas may affect adult survival rates and hence be significant drivers of demographic processes. In seabirds, poor knowledge of their true distribution outside the breeding season, however, has severely limited such studies. This study explored how annual adult survival rates of black-legged kittiwakes Rissa tridactyla on Hornoya in the southern Barents Sea were related to temporal vari- ation in prey densities and climatic parameters in their breeding and non-breeding areas. We used information on the kittiwakes' spatiotemporal distribution in the non-breeding season gained from year-round light-based tracking devices (geolocators) and satellite transmitters, and kittiwake annual adult survival rates gained from a multistate capture-mark-recapture analysis of a 22 yr time series of colour-ringed kittiwakes. In the post-breeding period, kittiwakes concen- trated in an area east of Svalbard, in the winter they stayed in the Grand Banks/Labrador Sea area, and in the pre-breeding period they returned to the Barents Sea. We identified 2 possible prey categories of importance for the survival of kittiwakes in these areas (sea butterflies Theco- somata in the Grand Banks/Labrador Sea area in winter and capelin Mallotus villosus in the Bar- ents Sea in the pre-breeding season) that together explained 52% of the variation in adult survival rates. Our results may have important implications for the conservation of kittiwakes, which are declining globally, because other populations use the same areas. Since they are under the influ- ence of major anthropogenic activities including fisheries, international shipping and the offshore oil and gas industry, both areas should be targeted for future management plans.

Reproduction and diet of Hyla euphorbiacea (Anura: Hylidae) in a pine-oak forest of southeastern Puebla, Mexico

We studied some reproductive characteristics and diet of the hylid frog Hyla euphorbiacea in a pine-oak forest from Sierra Negra, southeastern Puebla, Mexico. The breeding season lasted from June to September; during this period males exhibited monthly variation in gonadal activity, whereas females did not. Sexual size dimorphism was observed, with females being larger than males, and female size was positively correlated with number and diameter of ovarian follicles. Diet during the rainy season was composed of invertebrates, classified into 16 prey categories. The most important was Lepidoptera (larvae), followed by Coleoptera (adults), and Araneae. Diet diversity and trophic niche overlap between sexes were relatively high. We discuss some recent findings and biological characteristics of H. euphorbiacea, which potentially make this species more susceptible to population declines than other members of the genus.

Hábitos alimentarios del pargo mancha <i>Lutjanus guttatus</i> (Pisces: Lutjanidae) en Los Cóbanos y Puerto La Libertad, El Salvador

Abstract: A total of 175 spotted snapper Lutjanus guttatus were collected monthly in the Los Cobanos and Puerto La Libertad, El Salvador, from January to December 2000 to determine its feeding habits. The fishes studied ranged 9.8 - 58.0 cm in total length. Were collected using push-net and hook and line. This snapper is a bentonic opportunistic carnivorous predator. The total biomass of the stomach contents was 260.5 g. Crustaceans (Squillidae, Portunidae, Dynomenidae. Penaeidae, Sicyoniidae, Callianassidae), were the most abundant group: they accounted for 50.4% of the total biomass. Numerically, Portunus asper was the most abundant prey. Ontogenic differences were observed in the diet. In juveniles (16 cm TL). at any time of the year, the most frequent and abundant components were crustaceans and in adults were crustaceans, fishes and mollusks. The relative importance of different components of the diet was assessed with two indexes that combine. in different ways. percentage frequency of occurrence, percentage number and percentage weight of prey categories. The commercial use this resource and the absence of management strategies are discussed.