Diet of Eastern Imperial Eagle (Aquila heliaca) in Bulgaria: composition, distribution and variation

The Eastern Imperial Eagle (EIE) is a top predator exploiting different prey in different parts of its distribution. In this study, we summarise data collected over a long period of time (for 25 consecutive years), identifying key prey species in the different regions, as well as clarifying seasonal preferences in the eagle’s diet. Most studies on the EIE food composition covering different parts of the species distribution range analyse the breeding season, while data about the winter diet are scarce. To the best of our knowledge, this is the first study detailing the differences in EIE’s dietary preferences between the breeding and the winter periods. We identified 4891 specimens belonging to 196 different taxa, which represents the most comprehensive study considering the diet diversity of this threatened species. Mammals represented the largest proportion of the diet, followed by birds and reptiles. Northern White-breasted Hedgehog was the most common prey, accounting for 25.7% of the total prey caught and 26.75% of the biomass. The European Souslik was the second most important prey with 14.35% participation in the eagle’s diet, but with a 3.75% contribution to the biomass. As we predicted, prey composition and main prey species varied spatially and seasonally. Modelling differences in the EIE diet, we found that the “territory effect” had the strongest impact on the dietary variations. Diet diversity differed significantly between regions (F = 12.6, df = 4, p = 0.01). During the breeding season, eagles fed mainly on Hedgehogs (29.88%), Sousliks (16.85%) and Storks (7.74%), while the winter diet was predominantly small rodents (44.17%) and songbirds (13.96%). We found that top predators, such as EIE, have successfully adapted to a novel food source, which is abundant in the area. The detected flexibility in the diet of the species and its ability to switch to alternative prey, if available, when the primary prey decreased, should be considered when planning species conservation efforts. Investigating the temporal change of the main prey in the eagle’s diet is also crucial for further species conservation measures.

Winter diet of Japanese macaques from Chubu Sangaku National Park, Japan incorporates freshwater biota

The Japanese macaque (Macaca fuscata) is native to the main islands of Japan, except Hokkaido, and is the most northerly living non-human primate. In the Chubu Sangaku National Park of the Japanese Alps, macaques live in one of the coldest areas of the world, with snow cover limiting the availability of preferred food sources. Winter is typically a bottleneck for food availability potentially resulting in marked energy deficits, and mortality may result from famine. However, streams with groundwater upwelling flow during the winter with a constant water temperature of about 5 °C are easily accessible for Japanese macaques to search for riverine biota. We used metabarcoding (Cytochrome c oxidase I) of fecal samples from Japanese macaques to determine their wintertime diet. Here we provide the first robust evidence that Japanese macaques feed on freshwater biota, including brown trout, riverine insects and molluscs, in Chubu Sangaku National Park. These additional food sources likely aid their winter survival.

Wolf–Hunting Dog Interactions in a Biodiversity Hot Spot Area in Northern Greece: Preliminary Assessment and Implications for Conservation in the Dadia-Lefkimi-Soufli Forest National Park and Adjacent Areas

Hunting dog depredation by wolves triggers retaliatory killing, with negative impacts on wildlife conservation. In the wider area of the Dadia-Lefkimi-Soufli Forest National Park, reports on such incidents have increased lately. To investigate this conflict, we interviewed 56 affected hunters, conducted wolf trophic analysis, analyzed trends for 2010–2020, applied MAXENT models for risk-map creation, and GLMs to explore factors related to depredation levels. Losses averaged approximately one dog per decade and hunter showing a positive trend, while livestock depredations showed a negative trend. Wolves preyed mainly on wild prey, with dogs consisting of 5.1% of the winter diet. Low altitude areas, with low to medium livestock availability favoring wolf prey and game species, were the riskiest. Dogs were more vulnerable during hare hunting and attacks more frequent during wolf post-weaning season or in wolf territories with reproduction. Hunter experience and group hunting reduced losses. Wolves avoided larger breeds or older dogs. Making noise or closely keeping dogs reduced attack severity. Protective dog vests, risk maps, and enhancing wolf natural prey availability are further measures to be considered, along with a proper verification system to confirm and effectively separate wolf attacks from wild boar attacks, which were also common.

Changing winter diet of thick-billed murres Uria lomvia in Southwest Greenland, 1990s versus 2010s

Southwest Greenland constitutes an internationally important wintering area for seabirds, including thick-billed murres (Uria lomvia Linnaeus, 1758), but their prey may be affected by the general warming of this sub-Arctic region. We compare murre diet collected in winter in the 1990s and 2010s around Nuuk. Fish made up 36% of the diet (wet mass) and crustaceans 63% in the 1990s, changing to 22% and 78% in the 2010s, respectively. Capelin (Mallotus villosus Müller, 1776) was the dominant fish species, and the smaller contribution in the 2010s coincided with declining densities of capelin around Nuuk. The crustaceans were dominated by two krill species, Meganyctiphanes norvegica M. Sars, 1857, and Thysanoessa inermis Krøyer, 1846. However, M. norvegica was only important in the 2010s (51% wet mass), while T. inermis was dominating the 1990s with 62% wet mass and only 23% in 2010s. The dominance of M. norvegica in the 2010s confirmed our expectations of a gradual “borealization” of this region due to the generally warming sub-Arctic. The smaller contribution of fish in the diet may also support the hypothesis of deteriorating winter conditions for murres. Apart from the diet, plastic was found in 15% of the birds and 53% had parasitic nematods.

PSIV-1 A comparison of chromatography methods to estimate ruminal VFA concentrations

The objective of this study was to describe two chromatography equipment and their methods (EM) and to evaluate their adequacy in estimating ruminal volatile fatty acid concentrations (VFA). Adequacy was assessed through precision and accuracy using three standard mixtures of known acetate, propionate, and butyrate concentrations. The standard mixtures were prepared for VFA analysis using high-performance liquid chromatography (HPLC) or gas chromatography (GC). Each mixture was injected ten times into each EM. The comparison was assessed with rumen fluid samples from four cannulated steers offered three diets at 2% BW. Diet A simulated a forage-based diet offered to cattle during the winter. Diet B simulated a grower-type diet offered to weaned calves. Diet C simulated a finisher-type diet offered to finishing cattle. Rumen fluid was collected three hours after the morning feeding for seven days for each diet and strained through 8 μm porosity fiberglass wool. Two 2-mL aliquots were stored at -20°C for HPLC analysis, while two 8-mL aliquots were diluted with 2 mL of 25% meta-phosphoric acid and stored at -20°C for GC analysis. Chromatograms without a flat baseline were removed from the analysis. For the adequacy evaluation, HPLC (R2 = 0.997; Cb = 0.874) was more precise and accurate at estimating total VFA than GC (R2 = 0.447; Cb = 0.763). When compared with the standards, HPLC estimated less (P < 0.001) total VFA (98.8 ± 10.3 mM) than GC (110.5 ± 17.4 mM). Concentrations for acetate, propionate, and butyrate in rumen fluid samples were estimated for each EM and analyzed using a random coefficients model. Similarly, estimates for acetate, propionate, and butyrate were less for HPLC than GC (P ≤ 0.002). VFA estimation differs depending on EM chosen. Further research should identify the source of difference in VFA estimation from each EM.

Feasting, not fasting: winter diets of cave hibernating bats in the United States

Temperate bat species use extended torpor to conserve energy when ambient temperatures are low and food resources are scarce. Previous research suggests that migratory bat species and species known to roost in thermally unstable locations, such as those that roost in trees, are more likely to remain active during winter. However, hibernating colonies of cave roosting bats in the southeastern United States may also be active and emerge from caves throughout the hibernation period. We report what bats are eating during these bouts of winter activity. We captured 2,044 bats of 10 species that emerged from six hibernacula over the course of 5 winters (October–April 2012/2013, 2013/2014, 2015/2016, 2016/2017, and 2017/2018). Using Next Generation sequencing of DNA from 284 fecal samples, we determined bats consumed at least 14 Orders of insect prey while active. Dietary composition did not vary among bat species; however, we did record variation in the dominant prey items represented in species’ diets. We recorded Lepidoptera in the diet of 72.2% of individual Corynorhinus rafinesquii and 67.4% of individual Lasiurus borealis. Diptera were recorded in 32.4% of Myotis leibii, 37.4% of M. lucifugus, 35.5% of M. sodalis and 68.8% of Perimyotis subflavus. Our study is the first to use molecular genetic techniques to identify the winter diet of North American hibernating bats. The information from this study is integral to managing the landscape around bat hibernacula for insect prey, particularly in areas where hibernating bat populations are threatened by white-nose syndrome.

Winter diet of Long-eared Owls (Asio otus) in the southern Pannonian Plain (Serbia, Vojvodina)

Owl diets undergo qualitative changes across the different regions of their area of distribution. During the four winters (from 2014–15 to 2017–18), Long-eared Owls’ pellets were collected at three winterroosts located at the southern part of Pannonian Plain, in the Serbian province of Vojvodina. In 8070 prey items from pellets, we identified 16 mammal and 32 bird species. The Common Vole was the dominant prey species with a proportion in a range from 27.4% to 71.6%. The Muridae family formed a supplementary part of the diet: Mus sp., wood mouse and harvest mouse, during all winters. Birds were also a major supplementary prey during winter 2014–15, comprising 10.6%. A comparison of our results with the diet of Long-eared Owls wintering at the northern Pannonian plain (southwestern Slovakia) indicated an increase the proportion of some species in the southern part. How different land uses in agriculture and environmental conditions may be reflected in the food supply are discussed in relation to the diet composition of Long-eared Owls and an environment whose is richer provides both growing diversity in the diet of these owls and an expansion of their food niche. Our study described the Long-eared Owl as opportunistic predators expanding their food niche in the presence of diversified prey.

Digestive Adaptations of Both the Fore- and Hind-gut in a Temperate Colobine Monkey

Background: In mammal herbivores, the digestion of fiber usually occurs predominantly in either the foregut or in the hindgut. However, how both gut regions function synergistically in the digestion of fiber and other nutrients has rarely been reported in wild mammals. This requires an integrative study of host anatomy, physiology and gut microbiome. Colobine monkeys (Colobinae) are folivorous, with fiber fermentation primarily occurring in the foregut, with residual fermentation in the hindgut. For the few colobine species that live in temperate regions obtaining energy from fiber during winter is critical but the mechanisms enabling this remain unclear. Results: We studied microbial and morphological digestive adaptations of golden snub-nosed monkeys (GSMs), Rhinopithecus roxellana, a temperate forest colobine from central China. We tested for synergistic foregut and hindgut fiber digestion in a species that experiences high thermal energy demands while restricted to a fibrous, low-energy winter diet. We found that the GSM’s colon has a significantly greater volume than that of other foregut fermenting colobines, and both gut regions of GSMs are dominated by microbial taxa producing enzymes to enable active digestion of complex carbohydrates. The microbiomes of the fore- and hindgut differed significantly in composition and abundance. Although the expression of microbial gene functions for fiber digestion were higher in the foregut than in the hindgut, our microbiome analysis in conjunction with that for morphology, enzyme activity and fiber-protein digestion, suggests complementary fiber and protein metabolism in both gut regions. Conclusions: Our results support that both the GSM fore- and hindgut facilitate fiber digestion, with an enlarged colon consistent as an adaptation to accommodate high throughput of fiber-rich food during winter.