The hypothesis that small body size is correlated with preference for young leaves was tested in a community of leaf-chewing insect herbivores feeding on Ficus wassa in a humid tropical forest in Papua New Guinea. Feeding experiments on 48 species of herbivorous insects revealed a negative correlation between body size and a preference for feeding on young leaves. While small species preferred young leaves, large species showed no preferences, or preferred young leaves only slightly. This relationship was found for the entire leaf-chewing community, as well as for many of the constituent taxa on several taxonomic levels, from orders to genera. Taxonomic position of a species played little role in determining its preferences. It is proposed that higher toughness and lower nutrient content may act as complementary defences, which prevent small insects from feeding on mature foliage. While the low nutrient content of mature leaves may affect smaller herbivores due to their relatively higher metabolic rate and lower digestion efficiency, their toughness complicates feeding mechanically and may prevent the compensatory feeding necessary to offset the low nutritive value of mature leaves.
The diet composition and prey selection of grey wolves (Canis lupus) inhabiting the Roztocze and Solska Forest (south-east Poland) was studied based on an analysis of scats collected in 2001-2002 (n = 84) and 2017-2020 (n = 302). In both periods, wolves preyed mainly on wild ungulates (96.5-96.7% of consumed biomass). Roe deer (Capreolus capreolus) was the most critical wolf prey accounting for 57.8% of consumed biomass in 2001-2002 and 49.2% and 2017-2020, but wolves positively select only wild boar (Jacob's selectivity index D = 0.213 in 2001-2002 and 0.710 in 2017-2020) and fallow deer (D = 0.588 only in 2017-2020). The largest species – moose Alces alces and red deer Cervus elaphus – were consumed less than expected from their share in the ungulate community. Predation on medium-sized wild mammals and domestic animals was low, 0.8-2.2% and 1.1-2.7% of the biomass consumed, respectively. The breadth of the wolf diet was very narrow and identical in both study periods (B = 1.07), while the similarity of diet composition was high (α = 0.999). This study indicated the stability of the wolf diet over two decades and the importance of wild boar as a food source for this carnivore.
Food habits of blue sheep, Pseudois nayaur in the Helan Mountains of China were studied from November 2003 to October 2004 to better understand diet composition, seasonal variation, and feeding habitat preference. Blue sheep consumed 41 plant species that contributed >0.01% to the diets. During autumn, winter, and spring, primary species consumed were Stipa spp., Ulmus pumila, and Poa spp. Blue sheep also showed the different preference for these plant species. Graminoids were the largest proportion of the diet (36.7–58.8%) throughout the year, followed by the tree and shrub categories. Sedges were the smallest proportion of the diet (0.7–7.1%). Among the four habitat types, blue sheep showed pronounced preference for montane woodland steppe. Differences in the diets of Helan Mountains blue sheep from those of blue sheep elsewhere may reflect adaptations for geographical range, vegetation, and other factors.
Food composition of otter, Lutra lutra, was studied by the analysis of 349 spraints found during one year period (2003–2004) at the River Kamenice (Czech Republic), where Atlantic salmon, Salmo salar, fry have been stocked regularly since 1998 in a reintroduction programme for the species. Brown trout, Salmo trutta m. fario, dominated otter diet and formed 29% of all prey items and 62% of biomass of all fish eaten. The second most abundant prey (27%) was common sculpin, Cottus gobio, followed by Atlantic salmon, and grayling, Thymallus thymallus. The proportion of salmon in the diet of otters amounted to 14.5% in numerical abundance of all prey items taken and 2% in biomass of fish component of the diet. The majority (71.5%) of fish eaten by otters had a total length between 61 to 200 mm.
This work shows records of seasonal home range shift of radio collared red deer hinds (Cervus elaphus L., 1758) in southern Hungary from a forested block to the surrounding agricultural area every June between 1994–2000. Better quality of agricultural than forest forages is suggested as the main reason for this shift. Two hypotheses were tested: i) red deer consume mainly cultivated plants in the agricultural area and ii) agricultural plants are more nutritious than those in the forest at the time of home range shifting. Composition of forest and agricultural diet was determined by microhistological faeces analysis and the nutritive quality was assessed by the amount of crude protein and crude fibre content. Red deer diet was dominated by browse in the forest (65–85 %) whilst, in agricultural fields, wood species were as important as grasses (26–44 and 39–55 %, respectively). Consumption of cultivated plants was low (under 10 %) in the agricultural area. Nutritive quality of the diet was lower at the agricultural site than in the forest due to lower crude protein and higher crude fibre content. Seasonal home range shift of red deer hinds therefore, could not be explained by better nutritive quality of agricultural plants only. We suggest other factors that could potentially explain this behaviour.
The alimentary tract content composition of 106 European minnow (Phoxinus phoxinus, 25-75 mm TL) and 49 gudgeon (Gobio lozanoi, 31-123 mm TL) captured in August 1996 in the river Larraun (Northern Spain) was investigated in order to analyse their diet composition and interspecific diet overlap. Both species fed mainly on Chironomidae larvae, Trichoptera larvae and terrestrial invertebrates, although trophic diversity was significantly higher for European minnows. The diet composition and the feeding strategy plots revealed a similar ontogenetic shift of the relative contribution or these prey items to a more pronounced generalist feeding strategy as fish of both species grew larger. Additionally, comparisons between diet composition and the benthic macroinvertebrate community revealed that P. phoxinus and G. lozanoi refused Caenidae, showing a preference for Chironomidae and Psychomyidae. The simplified Morisita index proved that the diet overlap between the two species was indeed very high and significant. We discuss how morphological constraints - i.e. mouth size - , prey handling costs and habitat partioning could be responsible for the observed inter- and intra-specific (size-related) changes in diet preferences. However, we suggest that the combination of differential microhabitat use, diel feeding rhythms and diet plasticity could minimize the interspecific competition, allowing co-occurrence of these Cyprinidae species in relatively high densities in this reach of the river Larraun.