Trophic ecology of Patagonian flounder Paralichthys patagonicus (Jordan, 1889) in the Argentine-Uruguayan Coastal Ecosystem

Food habits and diet composition of Patagonian flounder Paralichthys patagonicus (Jordan, 1889) were studied on the basis of stomach content analyses from 828 specimens (512 females, 304 males, 12 unsexed) collected during 16 commercial cruises between February 2009 and April 2010 in the Argentine-Uruguayan Coastal Ecosystem (34° S-41° S). A total of 272 stomachs (32.9%) contained food (184 females and 84 males), among which 20 prey taxa were identified. The most important prey category was pelagic fish, primarily Argentine anchovy (Engraulis anchoita), followed by rough scad (Trachurus lathami). Evidence showed that females consumed a higher total wet weight of prey compared to males. Results also suggested a specialised diet over E. anchoita, across all sex and size groups. The estimated trophic level for the population of P. patagonicus was 4.16. This study suggests that P. patagonicus is a tertiary piscivorous consumer of the trophic food web in the region, and reveals changes in the prey consumption compared with previous studies.

Microhabitat use, daily activity pattern and diet of Liolaemus etheridgei Laurent, 1998 (Reptilia: Liolaemidae) in the Andean Polylepis forests of Arequipa, Peru

This study compared the microhabitat use, daily activity pattern and diet of Liolaemus etheridgei Laurent 1998 in two Polylepis woodlands: El Simbral (fragmented) and Tuctumpaya (unfragmented), in Arequipa, Southern Peru. In both populations, we did not detect positive selection for any microhabitat; however, the population at El Simbral showed a negative selection for Polylepys trees while the Tuctumpaya population showed negative selection for Polylepis trees and non-thorny bushes. In El Simbral, active individuals were detected between 9:00 and 15:59h, whereas in Tuctumpaya, we detected active individuals from 8:00 to 17:59h. In both populations, observations of active individuals dropped between 11:00 and 11:59h. We recorded 17 and 23 prey categories in the El Simbral and Tuctumpaya populations respectively. The most important animal prey category in each population was found to be Lygaeidae: Hemiptera, and was the only animal prey category that was selected for in El Simbral and Tuctumpaya. In addition, due to the proportions of plant material found, the El Simbral was found to be omnivorous, whereas the Tuctumpaya population was herbivorous. Trophic niche breadth was broader in Tuctumpaya (B_a= 0.202) than the El Simbral (B_a= 0.147) population, despite there being no significant differences in diet (Permanova: F = 1.036, P = 0.409, permutations = 9999), which is coherent with the high value of trophic niche overlap (O_(j,k) = 0.963). Our compiled data reveal that L. etheridgei shows no selection for any of the resources we define in Polylepis woodlands, on the contrary, it selects negatively against Polylepis trees and non-thorny bushes. The daily activity patterns indicate a bimodal pattern with peaks at 9:00-10:59 and 13:00-13:59 h. The diet of L. etheridgei consists mainly of plants (%W: 66.373), and the most important animal prey category is Lygaeidae: Hemiptera (%IRI = 55.3), which is selected positively.

Feeding Habits of Predatory Thermophilic Fish Species and Species with Subtropical Affinity from Recently Extended Distributional Range in Northeast Adriatic Sea, Croatia

The study investigates feeding habits of thermophilic species and species with subtropical affinity in the fishing catch in the Bay of Medulin (northeastern Adriatic Sea), and contributes to the knowledge about their presence in recently extended distributional range. In our methodology, the presence of the Seriola dumerili, Sphyraena sphyraena, Lichia amia, Coryphaena hippurus, Caranx crysos, Pomatomus saltatrix, and incidence of Trachinotus ovatus is recorded. A total of 220 specimens are captured during 2017, 2018 and 2019. A dietary assessment is performed, and the index of relative importance IRI was calculated for each prey category. Diet overlap is calculated using Schoener’s index, based on IRI. The principal diet of C. hippurus included Sardina pilchardus and Loligo vulgaris. Pomatomus saltatrix consumed species from the Sparidae family and T. ovatus crustaceans from the Mysidacea family. Different species from genus Atherina are represented important foods for L. amia, S. dumerili and S. sphyraena. Diets of significant importance for L. amia included fishes from the family Sparidae, for S. sphyraena from the Carangidae family, and S. dumerili from the Clupeidae and Muliidae families. Our analysis of diet overlap is based on IRI suggests no diet overlap between analysed fish species from Medulin Bay, and that these species utilise differing trophic niches.

Feeding habits of Lithobates megapoda (Anura: Ranidae), a threatened leopard frog used for human consumption, in Lake Chapala, Mexico

The Big-footed Leopard Frog (Lithobates megapoda) is a threatened and endemic species from western Mexico. This species has aquatic habits and it is distinguished by its large size, particularly by the length of its legs, reason for which it is captured for human consumption. Also, knowledge about its natural history is scarce and incomplete. In this study, we analyzed the composition of the diet of L. megapoda on the shore of Lake Chapala, the largest lake in Mexico. A total of 69 adult individuals were collected lifeless in fishing nets, during the rainy season (June-October), of which 48 had stomach contents. A total of 96 prey items were identified, which correspond to 13 prey categories. Fish constituted the most dominant prey category in the diet in terms of number, volume, frequency of occurrence, and relative importance. No significant differences were found in the consumption by prey type (aquatic or terrestrial). However, the aquatic preys had a greater relative importance and were more voluminous than the terrestrial ones. The diversity of prey categories, in terms of prey volume, indicates males may have a higher dietary diversity than females, but we not evaluated possible bias. In addition, a significant effect was found in the interaction of size (SVL) of frogs with the average of prey volume. Females (that are larger than males) consumed prey within a wide volume range and, the larger they are, more voluminous are prey. In this way it is possible that intraspecific competition for trophic resources in the environment is reduced. This study helps us understand the trophic ecology of L. megapoda, a frog species that plays an important role in the food web where it lives, as a predator feeding on aquatic and terrestrial organisms.

Diet of Chiasmocleis cordeiroi Caramaschi and Pimenta, 2003 from the Atlantic Rainforest in southern Bahia, Brazil

We studied the diet of a Chiasmocleis cordeiroi population in a fragment of the Atlantic Forest in the state of Bahia, Brazil. Frogs were collected at night after an explosive breeding event and were transferred to the lab where they were measured, weighed and had their stomach contents retrieved following a stomach flushing protocol. Individuals were later released back into the pond from which they had been collected. Stomach contents were measured and identified to the lowest possible taxonomic level. The most important prey category in the diet of C. cordeiroi was Hymenoptera (Formicidae), as has been already observed for other microhylids. The large number of prey items in the stomach and the low niche amplitude suggest that C. cordeiroi is a specialist using an active foraging strategy to detect its prey.

Autecology of the lizard Colobosauroides cearensis (Squamata: Gymnophthalmidae) from Brazilian semiarid Caatinga

Autecology of the lizard Colobosauroides cearensis (Squamata: Gymnophthalmidae) from Brazilian semiarid Caatinga. Colobosauroides cearensis is a diurnal lizard with a relictual distribution associated with forested habitats in the Brazilian Caatinga Domain. Knowledge of the natural history of this secretive lizard is scarce. Herein, the diet, reproduction, sexual dimorphism, microhabitat use, and thermal ecology of C. cearensis are described based on feldwork in 2015–2017 in the state of Ceará, Brazil. The diet of the lizards is composed exclusively of arthropods, with Formicidae being the most important prey category. Numerical and volumetric niche breadths are 5.52 and 9.2 respectively, and trophic niche overlap between females and males is 0.3. Males are distinguished from females by the larger size of the males and the presence of femoral pores. Colobosauroides cearensis is cryptozoic, inhabiting the leaf litter and having no direct contact with the soil or solar radiation. The average body temperature of the lizards is 30.4 ± 3.3°C, which is positively correlated with the air temperature. Gravid females with fxed clutch size of two eggs are found in early rainy season. Oviposition occurs between April and May (when the highest number of juveniles are observed). Sexual maturity occurs early in males and testicular volume is signifcantly correlated with body size.

Diet of the Viviparous lizard Zootoca vivipara (Lichtenstein, 1823) (Reptilia: Lacertidae) from its southern range

The Viviparous lizard Zootoca vivipara (Lichtenstein, 1823) is widespread across Eurasia, but in Bulgaria it is considered a glacial relict, restricted to the high mountains. In spite of its wide distribution, there is still lack of knowledge on its dietary habits, especially from the southern part of the range. In order to shed light on its diet, we conducted а study in three mountain sites in Bulgaria (Vitosha, Rila and Stara Planina Mtns.). They were visited in 2016 and 2017 during the lizard's active season (May–September); 343 Viviparous lizards were captured by hand and measured and weighed. To investigate the food preferences, we adopted a non-invasive method, obtaining faecal samples, which were then analysed under a stereoscopic microscope. A total of 290 faecal samples that could be assigned to individual specimens with determined age and sex were collected. We calculated the relative abundance and occurrence of each prey category. Data were compared by sex and age classes (immatures vs. adults) as a whole and for each of the three sites. A total of 19 prey categories were detected and the number of categories per study site varied between 16 and 18. The most common invertebrates were Araneae and Auchenorrhyncha. Statistically significant differences between immatures and adults were found as adults showed more diverse diet. No such differences between sexes were detected.

Spring food habits of Wolverine (Gulo gulo) in the Colville River watershed, Alaska

Wolverines (Gulo gulo) are relatively abundant on the North Slope of Alaska, an Arctic ecosystem dominated by tundra habitats that run north from the Brooks Range across a wide coastal plain to the Beaufort Sea. The region contains a range of potential Wolverine prey species, including ungulates (Caribou [Rangifer tarandus], Moose [Alces americanus]), Arctic Ground Squirrel (Urocitellus parryii), and both Soricidae and Cricetidae species. The seasonal composition of these, and other prey species, in the Wolverines’ diet is not well understood. We collected Wolverine scats during spring (March–May) on the North Slope while tracking animals from snowmobiles and with helicopters that visited areas identified as of interest during ground surveys or using global positioning system collared animals. We analyzed prey remains in 48 scat samples based on hair, bone, and other prey fragments. We then calculated frequency of occurrence, percentage of occurrence, and weighted percent volume for each major prey category detected. We confirmed species identity of scats as Wolverine by amplifying the control region of the mitochondrial DNA. We estimated spring diet diversity and richness based on nine major prey categories detected in scats. Ungulates and cricetids together constituted 69% of the Wolverines’ spring diet, with Snowshoe Hare (Lepus americanus) constituting 9%, fox (Vulpes spp.) 6%, Arctic Ground Squirrel 2%, birds 2%, American Beaver (Castor canadensis) less than 1%, and unknown 6%.

Diversity of ants and mites in the diet of the Brazilian frog Chiasmocleis leucosticta (Anura: Microhylidae)

We describe here the diet of the microhylid frog Chiasmocleis leucosticta based on the stomach contents of 72 individuals (47 males and 25 females) collected in pitfall traps at the Reserva Florestal de Morro Grande, state of São Paulo, southeastern Brazil. We identified 1,981 food items distributed in 13 prey categories of arthropods, mainly ants, mites and collembolans. Formicidae was the most abundant and frequent prey category, including 16 genera from seven subfamilies, and data on ant availability in the habitat suggest that C. leucosticta selects ants actively. The second main prey category was Acari, predominantly represented by mites of the suborder Oribatida. This is the first work identifying mites to the family level in the diet of a Microhylidae. There was no statistical difference between males and females regarding diet composition.

Are invasive populations characterized by a broader diet than native populations?

Background Invasive species are among the most significant threats to biodiversity. The diet of invasive animal populations is a crucial factor that must be considered in the context of biological invasions. A broad dietary spectrum is a frequently cited characteristic of invasive species, allowing them to thrive in a wide range of environments. Therefore, empirical studies comparing diet in invasive and native populations are necessary to understand dietary requirements, dietary flexibility, and the associated impacts of invasive species. Methods In this study, we compared the diet of populations of the African clawed frog, Xenopus laevis in its native range, with several areas where it has become invasive. Each prey category detected in stomach contents was assigned to an ecological category, allowing a comparison of the diversity of ecological traits among the prey items in the diet of native and introduced populations. The comparison of diets was also performed using evenness as a niche breadth index on all sampled populations, and electivity as a prey selection index for three out of the six sampled populations. Results Our results showed that diet breadth could be either narrow or broad in invasive populations. According to diet and prey availability, zooplankton was strongly preferred in most cases. In lotic environments, zooplankton was replaced by benthic preys, such as ephemeropteran larvae. Discussion The relative proportions of prey with different ecological traits, and dietary variability within and between areas of occurrence, suggest that X. laevis is a generalist predator in both native and invasive populations. Shifts in the realized trophic niche are observed, and appear related to resource availability. Xenopus laevis may strongly impact aquatic ecosystems because of its near complete aquatic lifestyle and its significant consumption of key taxa for the trophic relationships in ponds.