Ecology of a widespread large omnivore,Homo sapiens,and its impacts on ecosystem processes

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Influence of Fruit Availability on the Fission–Fusion Dynamics of Spider Monkeys (<Emphasis Type="Italic">Ateles geoffroyi</Emphasis>)

Socioecological theory proposes that the flexibility in grouping patterns afforded by fission–fusion dynamics allows animals to cope with spatiotemporal variability in food abundance. We investigate the influence of fruit tree abundance and foraging environment heterogeneity on fission–fusion dynamics in a group of spider monkeys (Ateles geoffroyi) in the Yucatan peninsula, Mexico. We collected 1300 h of behavioral data and 23 samples of biweekly ecological data from August 2009 to July 2010. We measured fission–fusion dynamics through the temporal variation in the size and composition of subgroups, the spatial dispersion within and between subgroups, and the frequency of fissions and fusions. We measured habitat-wide food abundance of preferred species, including two that differ greatly in their relative abundance: Brosimum alicastrum (a hyperabundant resource) and Ficus spp. (a not so abundant resource but often represented by large trees). We evaluated the foraging environment heterogeneity through the variance in the number of trees with fruit between species. Our results show that, although habitat-wide food abundance is important, the availability of key resources strongly influences the spider monkeys’ fission–fusion dynamics. When there was a high abundance of fruit of Brosimum, subgroups tended to be more stable, smaller, and mixed sex, and their members remained close. In contrast, when Brosimum trees with fruit were scarce, females often formed large, more fluid and dispersed subgroups. Foraging environment heterogeneity had a positive effect on within-subgroup spatial dispersion and rates of fission and fusion. The complex relationships we have uncovered suggest that the flexibility afforded by fission–fusion dynamics is an adaptation to highly variable foraging environments.     

Interspecific Interactions Between Cebus capucinus and Other Species: Data from Three Costa Rican Sites

Capuchins exhibit considerable cross-site variation in domains such as foraging strategy, vocal communication and social interaction. We report interactions between white-faced capuchins (Cebus capucinus) and other species. We present comparative data for 11 groups from 3 sites in Costa Rica that are ecologically similar and geographically close, thus reducing the likelihood that differences are due solely to genetic or ecological differences. Our aim is to document both the range of variation and common elements across sites and situations. We also consider factors that contribute to the variation or consistency or both, including social learning, local ecology, and temperament. We consider 4 categories of allospecifics: (1) vertebrate prey, (2) potential predators, (3) feeding competitors, and (4) neutral species. Although we cannot rule out local differences in ecology, our data suggest that social learning may account for at least some cross-site differences in behavior toward allospecifics. Our strongest finding is that boldness, aggression and pugnacity are displayed consistently across sites, groups and circumstances, even in interactions with neutral species, which reflects a critical aspect of species-specific temperament in Cebus capucinus that has been evolutionarily developed and reinforced through highly opportunistic foraging, strong predator defense, and active hunting. We suggest directions for future research, particularly in regard to primate temperament as an evolved trait with consequences for fitness.     

Fishing Long-Fingered Bats (Myotis capaccinii) Prey Regularly upon Exotic Fish

The long-fingered bat Myotis capaccinii is a European trawling bat reported to feed on fish in several Mediterranean locations, but the ecological circumstances of this behavior have not yet been studied. To elucidate the importance of fishing in this bat''s diet, we evaluated the frequency and seasonal variation of fish remains in 3,000 fecal pellets collected from M. capaccinii at a nursery roost in Dénia (Eastern Iberian Peninsula) in 2008, 2009, and 2010. Fish consumption occurred evenly throughout the year. All otoliths found in feces were identified as belonging to the surface-feeding fish Gambusia holbrooki. Measuring otoliths, we estimated that the mean size of consumed fish was significantly smaller than the mean measured for available fish, suggesting that the long-fingered bat''s relatively small body may constrain its handling of larger prey. Of note, one bat had eaten 15 fish, showing that fish may be a locally or seasonally important trophic resource for this species. By capturing 15 bats and radio-tracking the four with the most fish remains in their droppings, we also identified fishing areas, including a single fishing ground comprising several ponds within a golf course. Ponds hold a high density of G. holbrooki, suggesting that the amount of fish at the water surface may be the principal factor triggering fishing. The observed six-fold increase in percentage of consumed fish across the study period may be related to recent pond-building in the area. We discuss whether this quick behavioral response is a novel feature of M. capaccinii or an intrinsic feature that has erupted and faded locally along the species'' history.     

The choice of foraging strategy as a mechanism for the coexistence of <Emphasis Type="Italic">Myrmica</Emphasis> species (Hymenoptera,Formicidae) in a multispecific ant association

The foraging behavior and some mechanisms responsible for differentiation of ecological niches were studied in five Myrmica species that frequently coexist in nature. These species were assigned to three life forms according to the preference of litter or grass cover in the course of foraging. The group foraging of Myrmica was found to be a labile communicative system, affected by the layered distribution of species and competition with closely related species. In cases when species of the same life form shared a hunting area, or when their foraging layers overlapped by over 75%, some specific hierarchical interactions were observed: the colonies of the suppressed species changed the layer of foraging or ceased to forage in groups, collecting food instead as single predators. In most cases, the prevalence-subdominance relations between the associations studied were absent.     

Indirect cues in selecting a hunting site in a sit‐and‐wait predator

Sit‐and‐wait predators use relatively simple rules for their decisions to choose and leave a patch, such as using the direct presence of prey to select a hunting site. However, the direct presence of prey can only be used when there is a highly visited patch in the proximity of the predator. Therefore, it is plausible that sit‐and‐wait predators also exploit indirect cues of prey presence and, consequently, use associative learning to select a hunting site. The present study tests for the role of associative learning in a sit‐and‐wait predator species for which the ecology is well understood: Misumena vatia Clerck crab spiders. An ecologically relevant scenario is used by selecting flower colour as the conditioned stimulus and prey presence as the unconditioned stimulus. The results provide no evidence that M. vatia crab spiders use the association between flower colour and food presence for selecting a hunting site. After a training phase of being exposed to a colourful artificial flower highly visited by bees, spiders select a hunting site independently of its colour during the testing phase. Investigations of similar scope and ecological relevance are required with other sit‐and‐wait predators to identify the conditions promoting the use of associative learning for foraging site selection when animals face an unpredictable food supply.     

Crab spider hunting performance is temperature insensitive

1. Laboratory and field experiments showed that the hunting performance of two flower-dwelling crab spiders, Misumenops asperatus and Misumenoides formosipes, was thermally insensitive over a broad range of temperatures normally experienced by these spiders. 2. In the laboratory, HP, a behavioural metric of spider hunting performance, was similar for spiders of a given species over an ≈ 30 °C temperature range. 3. Spiders in the field captured predominantly hymenopterans and dipterans, and field hunting performance, measured as the number of prey captured per spider per day, also proved to be unaffected by temperature. 4. These findings counter the general rule that physiological/ecological performance in terrestrial arthropods is temperature dependent. 5. Freedom from temperature constraints on the capacity of crab spiders to capture prey may be due to the use of venom and/or to muscle physiological adaptations for anaerobic metabolism. 6. Wide thermal performance breadth increases the spectrum of prey available to M. asperatus and M. formosipes by allowing spiders to hunt prey active during cooler periods of the day as well as those active during warmer periods. 7. Wide thermal performance breadth also benefits M. asperatus and M. formosipes due to adult phenology; both species experience a seasonal temperature shift during the adult phase.     

Winter coexistence in herbivorous waterbirds: Niche differentiation in a floodplain,Poyang Lake,China

The classical niche theory supports the idea that stable coexistence requires ecological differences between closely related species. However, information on waterbirds coexistence in the entirely landlocked freshwater system of Poyang Lake is not well understood, especially when the available biomass of their food in the area decreases. In this study, we tested the ecological segregation mechanisms in the 2015/2016 and 2016/2017 wintering periods among eight herbivorous waterbirds (including the Siberian crane Grus leucogeranus, hooded crane Grus monacha, white‐naped crane Grus vipio, common crane Grus grus, greater white‐fronted goose Anser albifrons, bean goose Anser fabalis, swan goose Anser cygnoides, and tundra swan Cygnus columbianus) at Poyang Lake. Using field observations and species niche and foraging habitat selection models, we investigated the abundance, distribution, and food sources of these eight waterbird species to quantify and compare their habitat use and ecological niches. Our results showed that niche segregation among the waterbirds, with respect to food types, time, and spatial location, allow them to coexist and use similar resources. The water level gradually receded in the sub‐lakes of the Poyang Lake, which could provide food sources and various habitats for wintering herbivorous waterbirds to coexist. We demonstrated that the differences in habitat use could mitigate interspecific competition, which may explain the mechanism whereby waterbirds of Poyang Lake coexist during the wintering period, despite considerable overlap in the dietary niches of herbivorous waterbirds.     

Foraging errors play a role in resource exploration by bumble bees (Bombus terrrestris)

If the cognitive performance of animals reflects their particular ecological requirements, how can we explain appreciable variation in learning ability amongst closely related individuals (e.g. foraging workers within a bumble bee colony)? One possibility is that apparent ‘errors’ in a learning task actually represent an alternative foraging strategy. In this study we investigate the potential relationship between foraging ‘errors’ and foraging success among bumble bee (Bombus terrestris) workers. Individual foragers were trained to choose yellow, rewarded flowers and ignore blue, unrewarded flowers. We recorded the number of errors (visits to unrewarded flowers) each bee made during training, then tested them to determine how quickly they discovered a more profitable food source (either familiar blue flowers, or novel green flowers). We found that error prone bees discovered the novel food source significantly faster than accurate bees. Furthermore, we demonstrate that the time taken to discover the novel, more profitable, food source is positively correlated with foraging success. These results suggest that foraging errors are part of an ‘exploration’ foraging strategy, which could be advantageous in changeable foraging environments. This could explain the observed variation in learning performance amongst foragers within social insect colonies.     

Population aspects of sexual dimorphism in Mustelidae from the example of four species (Mustela lutreola, Neovison vison, Mustela putorius, and Martes martes)

Size sexual dimorphism was studied on 695 crania of four species of the Mustelidae. According to the degree of increasing differences between sexes, the species were arranged in the following order: common marten (Martes martes), European mink (Mustela lutreola), American mink (Neovison vison), and black polecat (Mustela putorius). The value of dimorphism characterizes the ecological flexibility of species and is an integrated population characteristic. It was demonstrated that M. martes occupies a specific and relatively narrow ecological niche of the forest ecosystem and joins weak competitive relations with smaller species of Mustelidae. The level of sexual dimorphism in M. lutreola and N. vison, as well as M. putorius, reflects the tension of their interspecific relationships in a given territory. A high level of sexual dimorphism in M. putorius is caused by further divergence of the ecological niches of males and females, being a compensatory mechanism, which mitigates the consequences of toughened environmental requirements.     

Foraging in space and time structure an African small mammal community

We used live-trapping and foraging to test for the effect of habitat selection and diet on structuring a community of six small mammals and one bird within the Soutpansberg, South Africa. We established grids that straddled adjacent habitats: woodland, rocky hillside, and grassland. Trapping and foraging were used to estimate abundance, habitat use, and species-specific foraging costs. The species with the highest abundance and foraging activity in a habitat, activity time, or food was considered the most efficient and presumed to have a competitive advantage. All species exhibited distinct patterns of spatial and temporal habitat preference which provided the main mechanism of coexistence, followed by diet selection. The study species were organized into three assemblages (α diversity): grassland, Rhabdomys pumilio, Dendromus melanotis, and Mus minutoides.; woodland, Aethomys ineptus and Micaelamys namaquensis; and rock-dwelling, M. namaquensis and Elephantulus myurus. Francolinus natalensis foraged in open rocky areas and under wooded islands within the grassland. Species organization across the habitats suggested that feeding opportunities are available within all habitats; however, distinct habitat preferences resulted from differing foraging aptitudes and efficiencies of the competing species. At Lajuma, species distribution and coexistence are promoted through distinct habitat preferences that were shaped by competition and species-specific foraging costs. The combination of trapping and foraging provided a mechanistic approach that integrates behavior into community ecology by ‘asking’ the animal to reveal its perspective of the environment. Using spatial and temporal foraging decisions—as behavioral indicators—enables us to guide our understanding for across-taxa species coexistence.     

Seasonal variation in the diet of the serotine bat (Eptesicus serotinus): A high-resolution analysis using DNA metabarcoding

Bats play an important role as predators of insect populations but are threatened by a variety of factors, including the loss of foraging habitat and insect declines. Knowledge on trophic interactions, foraging strategies, and hunting areas is key to understanding the ecology of bat species, to assess their impact on ecosystems and to optimize conservation strategies. We investigated seasonal trends in the diet of two nursery colonies of the serotine bat, Eptesicus serotinus, from an intensively farmed agricultural landscape in Germany. Using DNA-metabarcoding of food remains in bat droppings collected from May to July 2018, we identified 254 taxa of 13 arthropod orders to species or genus level, including numerous pest species. Our results indicate an equal use of Coleoptera, Diptera, and Lepidoptera, contradicting previous morphological dietary analyses that had shown beetles to be the most frequent prey. The dietary composition was seasonally highly variable and mainly determined by prey phenology. Dietary richness significantly increased throughout the sampling period, reflecting increasing insect activity with progressing season. Our findings demonstrate that E. serotinus is a generalist forager, linking different habitat types through trophic interactions.     

Reproductive and age classes do not change spatial dynamics of foraging long-fingered bats (Myotis capaccinii)

Spatial dynamics of foraging long-fingered bats (Myotis capaccinii) were studied in the Eastern Iberian Peninsula. We analysed the locations of 45 radio-tracked individuals during three discrete periods through the breeding season and measured the spatial parameters related to their foraging behaviour in order to test whether variations in spatial use occur. Colony range, measured as the minimum convex polygon through all the radiolocations, was 345 km², but the area used during each period was smaller. During pre-breeding, foraging bats gathered at two stretches of different tributary rivers; during lactation, they scattered throughout the river system; and during weaning, they aggregated at a stretch of the main river. Individuals on average flew 5.7 km from roosts to foraging areas, with a maximum absolute distance of 22.7 km. Individual foraging ranges were measured linearly, because the bats foraged mostly along rivers; their values averaged 1.3 km/night and overlapped extensively between neighbouring bats (>65% on average). The sampling period, rather than the bats’ reproductive status, age, or sex, explained the observed variability in spatial distribution and size of hunting sites. We did not find differences in spatial parameters between lactating females and non-lactating bats, nor between juveniles and adults. This is the first study to split the independent effects of season and population class in order to enable unconfounded interpretations of the spatial dynamics of foraging reproductive females and juveniles. We speculate that the relationship between colony size and prey availability ruled the observed changes in foraging area through seasons. The considerable overlap in individual foraging ranges may be a necessary adaption to large colonies forced by the specific roost requirements of the long-fingered bat and the narrow foraging niche they appear to occupy.     

Rapid shifting of foraging pattern by Yakushima macaques (Macaca fuscata yakui) in response to heavy fruiting ofMyrica rubra

We describe short-term changes in foraging behavior by wild Yakushima macaques (Macaca fuscata yakui),which inhabit a warm-temperate broad—leaved forest on Yakushima Island (30°N, 131°E), Japan. Rapid changes of dietary composition, activity budget, and range use by the monkeys occurred from May to June, apparently associated with changes in the availability of the fruit of Myrica rubraBefore the fruit ripened, monkeys spent less time moving and more time feeding on many species of leaves, which accounted for 40% of feeding time. However, when M. rubrabegan to ripen, they fed intensively on the fruit, which accounted for three-fourths of feeding time,though the activity budget remained unaffected As fiuit of M. rubradecreased,the monkeys fed more on the fruit of other species and on insects, and spent more time moving at higher speeds. There marked shifts in foraging pattern occurred within only two months. In terms of moving cost and dietary quality,Yakushima macaques shifted their foraging pattern according to the availability of M. rubrafrom a “low-cost, low-yield” strategy to a “low-cost, high-yield” strategy, and then to a more costly strategy. The ability to make such rapid shifts in foraging pattern may allow the macaques to effectively use the highly variable food supply within their small range.     

Differences in Forage-Acquisition and Fungal Enzyme Activity Contribute to Niche Segregation in Panamanian Leaf-Cutting Ants

The genera Atta and Acromyrmex are often grouped as leaf-cutting ants for pest management assessments and ecological surveys, although their mature colony sizes and foraging niches may differ substantially. Few studies have addressed such interspecific differences at the same site, which prompted us to conduct a comparative study across six sympatric leaf-cutting ant species in Central Panama. We show that foraging rates during the transition between dry and wet season differ about 60 fold between genera, but are relatively constant across species within genera. These differences appear to match overall differences in colony size, especially when Atta workers that return to their nests without leaves are assumed to carry liquid food. We confirm that Panamanian Atta specialize primarily on tree-leaves whereas Acromyrmex focus on collecting flowers and herbal leaves and that species within genera are similar in these overall foraging strategies. Species within genera tended to be spaced out over the three habitat categories that we distinguished (forest, forest edge, open grassland), but each of these habitats normally had only a single predominant Atta and Acromyrmex species. We measured activities of twelve fungus garden decomposition enzymes, belonging to the amylases, cellulases, hemicellulases, pectinases and proteinases, and show that average enzyme activity per unit of fungal mass in Atta gardens is lower than in Acromyrmex gardens. Expression profiles of fungal enzymes in Atta also appeared to be more specialized than in Acromyrmex, possibly reflecting variation in forage material. Our results suggest that species- and genus-level identities of leaf-cutting ants and habitat-specific foraging profiles may give predictable differences in the expression of fungal genes coding for decomposition enzymes.     

An ambusher's arsenal: chemical crypsis in the puff adder (Bitis arietans)

Ambush foragers use a hunting strategy that places them at risk of predation by both visual and olfaction-oriented predators. Resulting selective pressures have driven the evolution of impressive visual crypsis in many ambushing species, and may have led to the development of chemical crypsis. However, unlike for visual crypsis, few studies have attempted to demonstrate chemical crypsis. Field observations of puff adders (Bitis arietans) going undetected by several scent-orientated predator and prey species led us to investigate chemical crypsis in this ambushing species. We trained dogs (Canis familiaris) and meerkats (Suricata suricatta) to test whether a canid and a herpestid predator could detect B. arietans using olfaction. We also tested for chemical crypsis in five species of active foraging snakes, predicted to be easily detectable. Dogs and meerkats unambiguously indicated active foraging species, but failed to correctly indicate puff adder, confirming that B. arietans employs chemical crypsis. This is the first demonstration of chemical crypsis anti-predatory behaviour, though the phenomenon may be widespread among ambushers, especially those that experience high mortality rates owing to predation. Our study provides additional evidence for the existence of an ongoing chemically mediated arms race between predator and prey species.     

Trophic adaptability of late juvenile Atlantic spadefish Chaetodipterus faber (Teleostei: Ephippidae) related to habitat preferences in an estuary in northeastern Brazil

We tested the hypothesis that the highly flexible feeding repertoire of juvenile Chaetodipterus faber reflects their trophic adaptability by quantifying the feeding behaviour of juveniles in situ, for the first time, in a northeastern Brazilian estuary. The fishes presented a preference for alga-rich habitats, irrespective of the substrate type chosen during feeding bouts. The analysis of stomach contents revealed omnivorous feeding habits, indicating that the ingestion of plant material occurs incidentally during foraging for benthic prey hidden under the alga. Particulate feeding in the water column was often as important as bottom feeding on alga-rich substrates. The results of this study are consistent with those of other ephippid species in different coastal environments, which typically exploit an ample diversity of food items from different substrates. Therefore, the flexibility observed in the feeding behavior of the most ephippid species may be a fundamental determinant of the ecological success of this group.     

Foraging strategies of the acellular slime moulds Didymium iridis and Didymium bahiense

Organisms can increase their foraging efficiency by modifying their behaviour according to information about the quality of currently exploited resource patches. Here we examine the effect of food concentration on the foraging strategies of two previously unstudied species of slime mould: Didymium iridis and Didymium bahiense. We studied two main foraging decisions: how long to wait before commencing exploration of the surrounding environment (exploitation strategy) and how intensely to search the environment for new opportunities (exploration strategy). Food concentration did not affect exploitation behaviour in either D. iridis or D. bahiense. Food concentration did affect exploration behaviour in D. iridis, but not in D. bahiense. Encounters with food resources, irrespective of concentration, resulted in increased exploitation and decreased exploration in D. iridis but did not influence foraging behaviour in D. bahiense. We suggest that the varying foraging strategies of slime moulds may have evolved to exploit different resource distributions in their natural environments. We also discuss the potential impact of microbial contamination and differences in handling regimes.     

Behavioural context of multi-scale species distribution models assessed by radio-tracking

Incorporating ecological processes and animal behaviour into Species Distribution Models (SDMs) is difficult. In species with a central resting or breeding place, there can be conflict between the environmental requirements of the ‘central place’ and foraging habitat. We apply a multi-scale SDM to examine habitat trade-offs between the central place, roost sites, and foraging habitat in Myotis nattereri. We validate these derived associations using habitat selection from behavioural observations of radio-tracked bats. A Generalised Linear Model (GLM) of roost occurrence using land cover variables with mixed spatial scales indicated roost occurrence was positively associated with woodland on a fine scale and pasture on a broad scale. Habitat selection of radio-tracked bats mirrored the SDM with bats selecting for woodland in the immediate vicinity of individual roosts but avoiding this habitat in foraging areas, whilst pasture was significantly positively selected for in foraging areas. Using habitat selection derived from radio-tracking enables a multi-scale SDM to be interpreted in a behavioural context. We suggest that the multi-scale SDM of M. nattereri describes a trade-off between the central place and foraging habitat. Multi-scale methods provide a greater understanding of the ecological processes which determine where species occur and allow integration of behavioural processes into SDMs. The findings have implications when assessing the resource use of a species at a single point in time. Doing so could lead to misinterpretation of habitat requirements as these can change within a short time period depending on specific behaviour, particularly if detectability changes depending on behaviour.     

Lionfish predators use flared fin displays to initiate cooperative hunting

Despite considerable study, mystery surrounds the use of signals that initiate cooperative hunting in animals. Using a labyrinth test chamber, we examined whether a lionfish, Dendrochirus zebra, would initiate cooperative hunts with piscine partners. We found that D. zebra uses a stereotyped flared fin display to alert conspecific and heterospecific lionfish species Pterois antennata to the presence of prey. Per capita success rate was significantly higher for cooperative hunters when compared with solitary ones, with hunt responders assisting hunt initiators in cornering the prey using their large extended pectoral fins. The initiators would most often take the first strike at the group of prey, but both hunters would then alternate striking at the remaining prey. Results suggest that the cooperative communication signal may be characteristic to the lionfish family, as interspecific hunters were equally coordinated and successful as intraspecific hunters. Our findings emphasize the complexity of collaborative foraging behaviours in lionfish; the turn-taking in strikes suggests that individuals do not solely try to maximize their own hunting success: instead they equally share the resources between themselves. Communicative group hunting has enabled Pteroine fish to function as highly efficient predators.