Greater Diet Breadth Research Articles

Strolling through a Century: Replicating Historical Bird Surveys to Explore 100 Years of Change in an Urban Bird Community.

AbstractIn 1898, Herbert and Alice Walter started a 5-year survey of birds in Lincoln Park-the largest park in Chicago, Illinois-and summarized their data in an urban birding field guide, Wild Birds in City Parks. Twenty-nine years later, William Dreuth compared the relative frequency of species in the Walters' study to that in his own 5-year Lincoln Park survey. Between 2012 and 2015, we replicated these surveys to investigate a century of bird diversity and community composition change in urban Chicago. While species richness did not change, community composition did. We found that (1) species with a greater diet breadth and (2) species that increased in statewide occupancy were more likely to increase in frequency over time. We conclude that factors at multiple scales brought temporal changes to Chicago's bird community. Overall, this survey highlights the slow and subtle ways in which species may respond to a century of urban intensification.

Effect of landscape type, elevation, vegetation period, and taxonomic plant identification level on diet preferences of Alpine mountain hares (Lepus timidus varronis)

Diet is important for understanding the ecology and evolution of populations. When examining animals’ diets, the lowest taxonomic rank (i.e., species level) is generally used. However, it is questionable whether dietary description varies with respect to the plant taxonomy or with the extent of plant species diversity in landscapes. We studied the diet of the Alpine mountain hare (Lepus timidus varronis) by analyzing the botanical composition of fecal pellets and comparing the results with the availability of food plants. Overall, Alpine mountain hares selected ligneous plants, whereas grasses were neutrally consumed or avoided. Plant identification at the genus and family level revealed the most information, whereas little additional information was gleaned by identifying food plants at the species level. In low-diversity spruce forests and at higher elevations, hares exhibited greater diet breadth compared to high-diversity vegetative mosaics or at lower elevations, even if they had access to the same types of plants. This is likely due to the hares’ need to diversify their diet when plant quantity is low. Greater diet breadth and selection of a larger number of different plant types at the beginning of the plant vegetation growth period suggested that more food plants suitable for Alpine mountain hares were available during this time compared to the end of the vegetation period.

Trophic Ecology of Two Sympatric Frogs with Contrasting Morphology and Habitat Use in a Subtropical Wetland

Abstract Frog diets are influenced by multiple factors, including morphological constraints, habitat use, and seasonal variation in environmental conditions and food availability. This study combined stomach content analysis (SCA), stable isotope analysis (SIA), and estimates of prey availability to investigate the influence of body size and microhabitat use on seasonal variation of the trophic ecology of two sympatric hylids (Pseudis minuta and Scinax squalirostris). We evaluated two hypotheses: (1) the species with larger body and mouth sizes or broader use of microhabitats will have greater diet breadth, and (2) regardless of differences in morphological traits and microhabitat use, diet breadth of both species will be greater during the warmer of two periods. Pseudis minuta exhibited larger body size and mouth width and revealed broader use of microhabitats (mostly within and near major water bodies), whereas S. squalirostris had smaller body size and mouth gape and was found exclusively within or nea...

Ontogenetic food resource partitioning and feeding strategy in claroteid catfish, <i>Clarotes laticeps</i> in the lower River Niger

Clarotes laticeps is an important commercial food fish of the River Niger. Information on its food niche and feeding strategy could be useful for the rational exploitation and conservation of the species. Ontogenetic diet switch was investigated in samples of C. laticeps caught forthnightly, in the lower River Niger between January 2010 and December 2012. Weight, length and gut weight of captured specimens were taken, and distributed into twelve (12) size categories. Stomach contents were analyzed to determine the frequency of occurrence, weight and total number of dietary items in each dietary category, for each size group. Feeding strategy was graphically determined using the stomach content data. Results revealed that juveniles fed more on immature and adult insects, plant materials, detritus and small crustaceans. Medium size categories fed more on crustaceans, frogs, tadpoles and piscivorous materials. The bigger fishes consumed mostly fish and crustaceans, and showed more specialization in feeding, followed by juveniles. Greater diet breadth was found among the mature medium sizes. The study concludes that food partitioning among different sizes of C. laticeps is a major attribute that could contribute to the survival of the fish population in the lower River Niger.Keywords: Ontogenetic, resource partitioning, feeding strategy, Clarotes laticeps, River Niger

Understanding the inter-specific dynamics of two co-existing predators in the Tierra del Fuego Archipelago: the native southern river otter and the exotic American mink

Knowledge about interactions between endangered native southern river otters (Lontra provocax) and introduced American mink (Neovison vison) is essential for effective management of both species. We evaluated competition for spatial and trophic niches between otter and mink in overlapping and non-overlapping areas, comparing distribution, habitat preference, diet and mink marking behavior. We surveyed otter and mink signs along 250 km of Beagle Channel coastline. Habitat suitability models were constructed based on species presence/absence and habitat characteristics, using generalized linear models. Feces were collected for diet analyses. Otters used forested coasts with 12°–32° shoreline slope and without human influence, and our evidence suggests they were not affected by mink presence. Mink preferred forested and shrubland coasts with 10°–28° shoreline slope. Neither human influence nor otter presence affected mink habitat occupation, but in the presence of otters, mink left fewer signs. Otters consumed more aquatic prey than mink, and mink modified their diet in the presence of otters, consuming more exotic small terrestrial mammals and less fish as well as shifting to smaller and shallower fish species that are less consumed by otters. Mink showed more plastic, generalist behavior than otters, being more tolerant of human presence, using more habitat types and having greater diet breadth. At the same time, otters apparently affect mink adversely and could help limit their invasion in sympatric areas. Conservation and recovery of otters, therefore, may produce a secondary benefit of simultaneously reducing the effect of mink, thereby providing an additional way to control this exotic predator’s population.

Tolerance to Dietary Phenolics and Diet Breadth in Three Seed‐eating Birds: Implications for Graminivory

The ability to cope with plant secondary compounds (PSCs) has profound implications for an animal's behavior. In the present study, we assessed the tolerance to dietary phenolics in three seed-eating birds: Zonotrichia capensis, Saltatricula multicolor, and Diuca diuca, which differ in their diet breadth. Seeds in their habitat have distinct chemical composition: grass seeds have less PSCs, specifically, less total phenolics than forb seeds. Based on the detoxification limitation hypothesis and using published data of the natural history of these birds in the central Monte desert, we postulate that predominantly and exclusively graminivorous birds such as D. diuca and S. multicolor, respectively, are less tolerant due, in part, to a lower detoxification capacity than those with greater diet breadth, Z. capensis. To achieve this goal, we measured the food intake of diets varying in their concentration of tannic acid (TA). Indicators of tolerance were body mass change, food, TA and water intake, and glucuronic acid output throughout the experiment. Zonotrichia capensis performed better along the tolerance experiment: it maintained body mass from 0 to 4% TA diet, food and TA intake were higher than the other two species at the end of the experiment, and glucuronic acid output by Z. capensis was greater than D. diuca and S. multicolor from 2% TA diet until the end of the experiment. Our results suggest that Z. capensis is the most tolerant species and this physiological trait may explain their greater diet breadth.

Carnivory, Coevolution, and the Geographic Spread of the Genus Homo

This review traces the colonization of Eurasia by hominids some 1,700,000 years ago and their subsequent evolution there to 10,000 years ago from a carnivorous perspective. Three zooarchaeological trends reflect important shifts in hominid adaptations over this great time span: (1) increasing predation on large, hoofed animals that culminated in prime-adult–biased hunting, a predator–prey relationship that distinguishes humans from all other large predators and is a product of coevolution with them; (2) greater diet breadth and range of foraging substrates exploited in response to increasing human population densities, as revealed by small-game use; and (3) increased efficiency in food capture, processing, and energy retention through technology, and the eventual expansion of technology into social (symbolic) realms of behavior. Niche boundary shifts, examined here in eight dimensions, tend to cluster at 500 thousand years ago (KYA), at 250 KYA, and several in rapid succession between 50 and 10 KYA. Most of these shifts appear to be consequences of competitive interaction, because high-quality, protein-rich resources were involved. Many of the boundary shifts precede major radiations in the equipment devoted to animal exploitation. With a decline in trophic level after 45 KYA, demographic increase irreversibly altered the conditions of natural selection on human societies, from a largely interspecific competitive forum to one increasingly defined by intraspecific pressures. Regionalization of Upper Paleolithic artifact styles is among the many symptoms of this process.

Diet choice in patches: Time-constraint and state-space solutions

Two types of foraging problems, the allocation of time to a given resource patch, and diet choice, generally have been treated as independent problems. Building on the work of Heller (1980) , we present models which simultaneously incorporate both of these problems and make predictions on both diet choice and patch residence time. The first set of models incorporates the influence of time constraints on diet choice. A further model analyzes foraging in patches without any constraints on foraging time. Time constraints are limitations on the time available for foraging which are independent of the behavior of the predator. They may arise from changes in physical factors (e.g. return of the tide) or arrival of predators. If an animal is foraging under time constraints, the mode of prey depletion should influence foraging behavior in one of two ways. (1) If prey encounter rates diminish due to the capture of prey by the predator, then the predator should be less choosy in its choice of diet as the density of high quality prey decreases. However, if the density of prey remains constant (e.g. due to a run of bad luck when no available prey are located) and if the available foraging time is known, the forager should become more selective as the time left in the patch runs out. If the forager is unable to predict the amount of foraging time left (e.g. if the arrival of some disruptive element, such as a predator, is a Poisson process), diet choice will be determined by prey encounter rates but will be unaffected by the length of time remaining. (2) If prey encounter rates diminish due to predator avoidance or competition (and therefore independent of the capture of prey by the forager) then selectivity should decrease as time left approaches zero. Patch residence times under this condition should increase monotonically with an increase in patch quality, travel time and initial prey densities of an average patch. If foraging time is not constrained, predictions about patch residence times and diet choice are qualitatively similar to condition (2) above, even if prey depletion is caused by prey capture. One trend in diet choice is predicted for all conditions in depleting patches: the longer the forager has been in a patch, the greater diet breadth should be. The opposite is predicted for non-depleting patches: diet breadth should decrease for longer residence times. Results from two published studies are interpreted in the context of these predictions.