Diet analysis and feeding ecology

Assuming generalist feeding habits to be the original condition in carabid beetles, we tested
two alternative hypotheses about the evolution of food specialisation: that species specialised
on prey that 1) were already of high quality to the generalists, or 2) were of low quality to the
generalists due to chemical or other defences. We did this by evaluating in laboratory
experiments the food quality to three generalist carnivore species of various prey types,
selected among those on which carabids are known to have specialised (i.e. insects,
earthworms, molluscs, seeds). The carabids used were adults of Pterostichus melanarius
Illiger, Pterostichus versicolor Sturm and Carabus nemoralis Mueller. Insects were highquality
food, earthworms were intermediate, and slugs and seeds were low quality food for all
species. For C. nemoralis, earthworms were the most preferred prey. The results support the
second hypothesis, that food specialisation evolved by breaking the defences of low quality
but presumably abundant prey.

The Chimango Caracara (Milvago chimango) is the raptor species most widely distributed and
abundant in Chile. Despite this, there is very little published information on its natural history and ecology in
that country. To investigate this information shortage, I compared the number of studies on Chilean vs. Argentine
populations of the Chimango Caracara published between January 1900 and August 2015. In my analysis, I only
selected those publications that addressed definite aspects of natural history and basic ecology of the Chimango
Caracara. I expressed the research productivity as a decadal rate of publication (i.e., number of papers published
per decade). Until the 1970s, the amount of articles published was similar between Chile and Argentina. Instead,
from 1980 to 2015 there was a considerable difference in research productivity. While the rate of publication in
Argentina increased from ≈ 1 to ≈ 2.3 articles/year between 1980 and 2015, in Chile it did not exceed 1 article/
year. Since 1980, publications on Chimango Caracaras in Argentina also were more diversified than in Chile. Potential
reasons for the lack of studies on the Chimango Caracaras in Chile include historical factors, “blackout”
of the natural history, dwindling of the field biology, undervaluation of diet studies, exclusion within integrative
approaches, and biases of researchers’ interest. To spark again the interest in studying the Chimango Caracara, I
suggest a number of training and research recommendations. These include promotion of the natural history and
aspecfield
biology, reappraisal of diet studies, to link behavioral studies to biological conservation, and prioritizing
studies contributing to deepen our knowledge of the history of life and basic ecology of the species. In southern
Chile, studies focused to understand the relationship between Chimango Caracaras and native forest are highly
needed.

In recent years the scientific community has shown an increased significant interest in the relationship between biomechanics and diet in extant and extinct primates. Most of these conclusions were based on the analyses of cranial morphology or unworn teeth. However, while tooth morphology can suggest what type of food can be processed, dental wear can tell us how a tooth is used. In this study, we examine the stress distribution in a digital model of a second mandibular molar of Pongo pygmaeus during occlusal loadings, taking into account the macrowear pattern. We combine together two different digital approaches: Finite Element Analysis (FEA) for the study of stress distribution and the Occlusal Fingerprint Analysis (OFA) for the examination of dental macrowear. The OFA results show a flat wear pattern characterized by large Phase II and large buccal phase I facets. On the contrary, the lingual phase I facets are less developed with the exception of facets 5 and 7 that form along ...

Pongo pygmaeus is a large great ape that lives in highly sea- sonal environments of Borneo, where the preferred foods, such as ripe and soft fruits, are often unavailable. During these periods orangutans rely on hard food items, such as nuts and seeds, which become particularly challenging to eat. Is their dental morphology designed to feed on these hard foods? In order to answer this question we employ an innovative digi- tal approach that integrates Finite Element Analysis with oc- clusal molar macrowear. Our preliminary results on a lower second molar (M ) suggest that the feeding behavior of orangutans manly involve crushing masticatory processes and
little shearing, typical of hard-object diets. The morphology of P. pygmaeus M2, with low cusps, thick enamel and a wrinkled occlusal surface seem to minimize tensile stresses in the tooth. The protostylid with its (moderate) buttress-shaped morphol- ogy seems to functionally suffer the high tensile stresses concentrated along the buccal groove of the crown by the extensive load applied on the buccal cusps during maximum intercuspation. Thus, it appears that non-preferred foods (also called fallback foods) such as nuts and seeds have played a major role in the evolutionary and morphological adaptations in P. pygmaeus molars. This new method can be further used to advance our understanding of the diet, morphology and evolution of extinct hominins.

There is a little understanding of how apex carnivores partition their diet to coexist. We studied food habit and trophic niche overlap of two apex carnivores, tiger and leopard in the tropical forest of Similipal tiger reserve, eastern India. We used line transect and scat analysis method, to estimate the prey availability and determine the diet and prey selection of two apex carnivores. Tigers consumed mostly large and medium-sized prey, whereas leopards mostly consumed medium and small-sized prey. Both carnivores were not random in their consumption of prey, sambar and wild pigs were selectively consumed by tigers, whereas leopards selectively consumed wild pigs, barking deer and mouse deer. Dietary overlap between two carnivore species was moderate (Pianka's niche overlap index: 0.55), and trophic niche breadth (Levin's standardized niche breadth) of the leopard (0.52) was greater than that of the tiger (0.37). Overall, tigers exhibited specialized feeding habits, whereas leopards showed generalist feeding habits. Our study highlights the opportunistic nature of leopards and probably a reason for the species successfully coexist with tigers.

The main objective of this work was to develop and validate a robust and reliable “from-benchtop-to-desktop” metabarcoding workflow to investigate the diet of invertebrate-eaters. We applied our workflow to faecal DNA samples of an invertebrate-eating fish species. A fragment of the cytochromecoxidase I (COI) gene was amplified by combining two minibarcoding primer sets to maximize the taxonomic coverage. Amplicons were sequenced by an Illumina MiSeq platform. We developed a filtering approach based on a series of nonarbitrary thresholds established from control samples and from molecular replicates to address the elimination of crosscontamination, PCR/sequencing errors and mistagging artefacts. This resulted in a conservative and informative metabarcoding data set. We developed a taxonomic assignment procedure that combines different approaches and that allowed the identification of ~75% of invertebrate COI variants to the species level. Moreover, based on the diversity of the variants, we introduced a semiquantitative statistic in our diet study, the minimum number of individuals, which is based on the number of distinct variants in each sample. The metabarcoding approach described in this article may guide future diet studies that aim to produce robust data sets associated with a fine and accurate identification of prey items.

This study examines the diet of the round goby (Neogobius melanostomus) in the western basin of Lake Erie. As an inva-sive benthic feeder, the round goby has the potential to affect smallmouth bass and other native species. Round goby (n = 100) were collected during summer 2011 and stomach contents were examined to determine diet patterns and possible ontogenetic diet shifts. Individual round goby were grouped by sex, size (small < 65 mm, large ≥ 65 mm), depth of habitat (shallow < 2 m, deep > 5 m), and habitat type (natural shallows, anthropogenically modified shallows, and deep waters). Gut fullness ranged from 10 to 100% with 23 stomachs presenting 100% fullness. Round goby consumed 27 different food items including abiotic (sand grains, gravel), floral (algae, fine leaved vascular plants), and fauna items. The Index of Relative Importance (IRI) and comparative z-tests were used to assess correlations and differences. Two-way z-tests revealed a significant difference in mouth gape related to size (z = À5.56377, P = 2.64e-08), and habitat depth (z = 3.34262, P = 0.00083). A significant linear correlation was also found between mouth gape standardized by head length (HL) for both males (P = 2.63e-9) and females (P = 1.3e-4). Two-way z-tests also revealed a significant difference in gonadosomatic index (GSI) related to sex (z = 6.07727, P = 6.11248e-10), but not size. A significant difference in gut fullness was also found related to sex (z = À3.34743, P = 0.00082), habitat depth (z = 3.16336, P = 0.00156), and habitat type (z = À2.7398, P = 0.00615). IRI values demonstrated a diet selective of veliger mussels (IRI = 2462.01), juvenile mussels (IRI = 1073.03), cladocer-ans (IRI = 4804.31), and chironomids (IRI = 1012.12). While previous studies have focused on round goby diet shifts from macroinvertebrates to bivalves, most studies did not evaluate changes in diet among multiple categories. Furthering knowledge of multiple aspects of goby diet may aid in developing management techniques to deter future round goby invasion.

Bone collagen stable nitrogen isotope values are reported for modern kangaroos (Macropus spp.) from eight field sites along a 1160 km south-north transect from temperate coastal to arid interior South Australia, in order to investigate d 15 N tissue variability in relation to rainfall and relative humidity. Mean annual rainfall along the transect ranges from 775 mm at Mount Gambier in the southeastern coast to 176 mm at Innamincka in the arid northern interior, while 3pm relative humidity ranges from 73% at coastal Flinders Chase to 36% at Innamincka. In arid habitats (176-238 mm rainfall), the d 15 N values of kangaroo bone collagen become more positive in relation to decreasing mean annual rainfall (r 2 = 0.98), while there is only a weak correlation with relative humidity (r 2 = 0.67). In contrast, in temperate and semi-arid coastal habitats (350-775 mm), there is no correlation between kangaroo bone collagen d 15 N values and rainfall (r 2 = 0.0011) or between d 15 N values and relative humidity (r 2 = 0.0035). Thus, in South Australia, kangaroo bone collagen d 15 N values do not show a simple linear correlation with either rainfall or relative humidity across all habitats. These results suggest that stable nitrogen isotope analyses of herbivore bones obtained from archaeological and palaeontological sites may provide a reliable proxy for past rainfall values in arid-land ecosystems.