Stealing of dunked food in Carib grackles (Quiscalus lugubris)

The use of tool or tool-like food processing behaviours can render animals vulnerable to theft (kleptoparasitism) because (1) large, nutritious items are usually involved, (2) value is added to the food due to long and/or complex handling, and (3) physical control of items is often temporarily lost during handling. In Barbados, Carib grackles (Quiscalus lugubris) immersing items in water before consumption (a behaviour known as food dunking) lose a larger proportion of items to conspecific food thieves than grackles that do not dunk. In this paper, we first show that dunking in Carib grackles functions as a proto-tool food-processing technique that speeds up ingestion. We then examine five potential predictors of kleptoparasitism: only conspecific density and loss of physical control on food were found to influence the probability that birds would be attacked and successfully robbed of food by conspecifics. Grackles could reduce the probability of kleptoparasitism by holding items in the bill while dunking and engaging in head-up displays. These behaviours were used flexibly depending on variation in the risk of kleptoparasitism. We suggest that costs like the ones incurred from theft might limit the profitability and frequency of tool and proto-tool food processing behaviours, creating a context where counter-strategies might be selected.     

Are Cape Ground Squirrels (Xerus inauris) Sensitive to Variation in the Pay‐offs from Their Caches?

For food caching to be adaptive, the benefits of recovery must outweigh the costs of storing an item. One of the costs to cachers is the risk of theft, and therefore, it is predicted that individuals may be sensitive to this theft and show various behavioural strategies to minimise it. In this study, we gave wild Cape ground squirrels (Xerus inauris) a choice between two different coloured items of the same food type: one item with a specific colour that was always artificially removed when cached and the other item with a different colour that was not removed when cached. During the choice presentations, subjects reduced the amount they consumed and cached of the food items with the colour that was experimentally removed when cached, despite the two items only differing in caching pay‐off. This avoidance to choose the food with the colour that was removed occurred over time, which suggests that subjects were using information about the item's pay‐off during cache recovery and this then impacted on successive decisions. This study highlights how the sensitivity to a food item's pay‐off can affect an individual's choice towards items that offer the greater overall reward.     

Sib‐sib communication and the risk of prey theft in the barn owl Tyto alba

Conflicts among siblings are widespread and their resolution involves complex physical and communication tools. Observations in the barn owl Tyto alba showed that siblings vocally communicate in the absence of parents to negotiate priority of access to the impending food resources that parents will bring. In the present paper, we hypothesize and provide correlative evidence that after a parent brought a food item to their progeny, sibling competition involves vocal sib‐sib communication. A food item takes a long time to be entirely consumed, and hence siblings continue to compete over prey monopolization even after parents gave a food item to a single offspring. When physical competition is pronounced and thereby the risk of prey theft is high, the individual that received a prey item consumes it in a concealed place. Concomitantly, nestlings vocalize intensely probably to indicate their motivation to siblings to not share their food item, since this vocal behaviour was particularly frequent in younger individuals for which the risk of being robbed is higher than in their older siblings. Furthermore, nestlings consumed more rapidly a food item when their siblings vocalized intensely presumably because the intensity of siblings’ vocalizations is associated with a risk of prey theft. Our correlative study suggests that sibling competition favoured the evolution of sib‐sib communication under a wide range of situations.     

年龄和性别因素对奇台沙蜥食性的影响

采用胃容物分析法研究年龄和性别因素对奇台沙蜥(Phrynocephalus grumgrzimailoi)食性的影响.共解剖220号浸制标本,取出整胃分离胃容物,鉴别胃容物中的食物种类,统计各种食物组分的数量频率、重量比例、出现频率和相对重要性指数(index of relative importance,IRI).结...     

Spontaneous categorization of vocal imitations in African grey parrots (Psittacus erithacus)

The ability to categorize elements of the environment is a fundamental aspect of information processing. Many experiments demonstrate the ability of birds and non-human primates to classify items according to their perceptual similarities. Few data are available regarding spontaneous classification of items according to a non-perceptual account in non-human animals. Here, we report unexpected results obtained with African grey parrots learning the referential use of French labels. Parrots did not learn the correct labels but they spontaneously produced more labels corresponding to food when a food item was presented to them and more labels corresponding to an object when shown an object item, although they were never rewarded for doing so. These results demonstrate a form of spontaneous categorization by using vocal imitation of the human language.     

Diet of the helmeted guineafowl (Numida meleagris galeata Pallas) in the Waza region of North Cameroon

Through laboratory and field experiments, we investigated the effect of food availability and food nutritive value on food selection by helmeted guineafowl ( Numida meleagris galeata Pallas) during the dry season in the Waza region of North Cameroon. Field study and crop analysis shows that a wide variety of food types are eaten by guineafowl during the dry season. Analysis of 101 crops from wild birds reveals a statistically significant positive correlation between the sodium and water content of food items and the quantity found in the crops. Rhizomes of Stylochiton lancifolius and termites form the bulk of the diet of this species during the dry season. It is concluded that the selection of water‐rich food may be an adaptation to dry environment.     

Growth and social interactions of wild and sea-ranched brown trout and their hybrids

A laboratory study of the social behaviour and growth performance of juvenile brown trout Salmo trutta of wild and sea-ranched origin and their crosses, indicated that the social behaviour of wild and sea-ranched fish differed. Male and female parents seemed to have a different impact on the juveniles. The category having wild mother and sea-ranched father were less aggressive, less active in general, but active in feeding, and therefore had higher growth rates. This pattern arose despite that the feeding rate and the motivation to first get a food item when food was provided did not differ between the groups of fish. Wild fish tended to be most aggressive. If sea-ranched and wild fish have different intrinsic (genetically based) 'life styles', the crosses between wild and sea-ranched fish indicate that there is likelihood for an introgression of genes adapted to hatchery environment into the genetics of wild conspecifics. This is particularly serious when hatchery-reared fish invades wild populations over many years.     

Fecal glucocorticoids as indicators of metabolic stress in female Sykes' monkeys (Cercopithecus mitis albogularis)

Because of their mediating role in the stress response and potential effects on fitness, glucocorticoid (GC) hormones are increasingly used to assess the physiological costs of environmental and behavioral variation among wild vertebrates. Identifying the proximate causes of GC variation, however, is complicated by simultaneous exposure to multiple potentially stressful stimuli. Here, we use data from a partially provisioned social group of Sykes' monkeys to evaluate the effects of potential psychological and metabolic stressors on temporal and individual variation in fecal GC (fGC) excretion among 11 adult females. Despite high rates of agonism over provisioned foods fGCs declined during periods of high provisioning frequency when fruit availability was dominated by neem (Azadirachta indica), an item requiring great feeding effort. Provisioned foods did not prevent fGC increases when availability of the most preferred main fruit item, tamarind (Tamarindus indica), declined drastically. Although rank-related differences in access to provisioned foods and rates of agonism did not lead to an overall effect of rank on fGCs, low-ranking females excreted more fGCs than high-ranking females during a period of high provisioning intensity and low fruit availability. The emergence of this rank effect was associated with elevated feeding effort in all females, a greater access to provisioned items by high-ranking females, and a higher proportion of time spent moving in low-ranking females. Our findings suggest that metabolic stressors were the primary determinants of both temporal and individual variation in fGCs, indicating potential fitness benefits for high-ranking females when food availability is limited.     

The importance of ingestion rates for estimating food quality and energy intake

Testing ecological or socioecological models in primatology often requires estimates of individual energy intake. It is a well established fact that the nutrient content (and hence the energy content) of primate food items is highly variable. The second variable in determining primate energy intake, i.e., the ingestion rate, has often been ignored, and few studies have attempted to estimate the relative importance of the two predictors. In the present study individual ingestion rates were measured in two ecologically very different populations of Hanuman langurs (Semnopithecus entellus) at Jodhpur, India, and Ramnagar, Nepal. Protein and soluble sugar concentrations in 50 and 100 food items. respectively, were measured using standardized methods. Variation in ingestion rates (gram of dry matter per minute) was markedly greater among food items than among langur individuals in both populations, but did not differ systematically among food item categories defined according to plant part and age. General linear models (GLMs) with ingestion rate, protein, and soluble sugar content explained 40-80% of the variation in energy intake rates (kJ/min). The relative importance of ingestion rates was either similar (Ramnagar) or much greater (Jodhpur) than the role of sugar and/or protein content in determining the energy intake rates of different items. These results may impact socioecological studies of variation in individual energy budgets, investigations of food choice in relation to chemical composition or sensory characteristics, and research into habitat preferences that measures habitat quality in terms of abundance of important food sources. We suggest a definition of food quality that includes not only the amount of valuable food contents (energy, vitamins, and minerals) and the digestibility of different foods, but also the rate at which the food can be harvested and processed. Such an extended definition seems necessary because time may constrain primates when feeding competition is intense and foraging is risk-prone.     

Food transfers in immature wild western lowland gorillas (Gorilla gorilla gorilla)

The transfer of food items between individuals has been described in primates as serving an informative purpose in addition to supplementing the diet of immature individuals. This behaviour has yet to be described in western lowland gorillas (Gorilla gorilla gorilla), and results are presented here of observations of food transfers in immature gorillas at Mbeli Bai, Republic of Congo. The frequency of food transfers decreased with increasing immature age, while the frequency of independent feeding and processing of food increased. Transfers between mothers and infants were the most frequent, with infants attempting to take items from the mother. These attempts were not always successful and the item was relinquished on less than 50% of attempts. Mothers also took items from their offspring. The results point to the functional significance of food transfers in western lowland gorillas being informational. In a bai environment, where one species forms the majority of a visiting gorilla’s diet despite other species being available, the initiation of food transfers by immatures is proposed to serve the purpose of familiarising them with which species, and which parts of those species, may be eaten.     

Anti-apostatic selection by wild birds on quasi-natural morphs of the land snail Cepaea hortensis: a generalised linear mixed models approach

Anti-apostatic selection occurs when predators feed disproportionately on rare prey, a process that leads to a decrease in variation within prey populations. Most of the evidence for this phenomenon comes from experiments using artificial prey items distinguished by simple artificial colour differences. We describe an experiment performed at 10 different sites in which we tested whether selection by wild birds is anti-apostatic when presented with high density populations of shells of the polymorphic land snail, Cepaea hortensis , stuffed with pastry. At each site we presented two sorts of populations in sequence: 45 yellow unbanded with 5 yellow banded, and 5 yellow unbanded with 45 yellow banded. Selection was measured using an analysis based on generalised linear mixed models (GLMMs) that has broad applicability to all resource selection studies where extraneous variance is a problem. Using this analytic method, we found that birds altered their behaviour to produce significant anti-apostatic selection in direct response to changes in frequency of the quasi-natural Cepaea morphs.     

The outcome of competition between the two chrysomonads Ochromonas sp. and Poterioochromonas malhamensis depends on pH

We investigated the effect of pH on the competition of two closely related chrysomonad species, Poterioochromonas malhamensis originating from circumneutral Lake Constance, and Ochromonas sp. isolated from a highly acidic mining lake in Austria (pH ∼2.6). We performed pairwise growth experiments between these two species at four different pH ranging from 2.5 to 7.0. Heterotrophic bacteria served as food for both flagellates. Results were compared to growth rates measured earlier in single species experiments over the same pH range. We tested the hypothesis that the acidotolerant species benefits from competitive release under conditions of acid stress. The neutrophilic strain numerically dominated over the acidotolerant strain at pH 7.0, but was the inferior competitor at pH 2.5. At pH 3.5 and 5.0 both strains coexisted. Surprisingly, P. malhamensis prevailed over Ochromonas sp. under moderately acidic conditions, i.e. at the pH where growth rates of the latter peaked when grown alone. Since bacterial food was not limiting, resource competition is improbable. It appears more likely that P. malhamensis ingested cells of its slightly smaller competitor. Adverse effects mediated via allelopathy, either directly on the competing flagellate or indirectly by affecting its bacterial food, might also have affected the outcome of competition.     

Dung avoidance as a possible mechanism in competition between wild and domestic ungulates: two experiments with chamois <Emphasis Type="Italic">Rupicapra rupicapra</Emphasis>

Wild ungulates often adjust spatial behaviour where they coexist with livestock. In European mountains, chamois Rupicapra rupicapra or R. pyrenaica commonly avoid alpine pastures used by domestic sheep. Mechanisms leading to competitive losing out of the wild species are not well understood, but mostly, resource competition is inferred and sometimes demonstrated. We hypothesised that chamois need to minimise the risk of intestinal parasite uptake and therefore would avoid pastures contaminated with sheep dung. We tested this in two experiments by contaminating feeding patches of wild and captive chamois with (parasite-free) sheep faeces. Wild chamois did not avoid grazing sites or plots on which sheep dung had been placed at a (low) density representing the commonly encountered situation in the Swiss Alps. Captive chamois strongly reduced browsing time on small trees given for food when the surroundings of the trees were sprayed with a watery faecal solution. We concluded that the odour signalled a potential high risk of parasite infection to the captive chamois, whereas the density of sheep dung on the grazing site of wild chamois was not high enough to be perceived as a risk. The need to minimise endoparasite uptake from faeces may therefore play a role in driving spatial behaviour of wild ungulates and could result in competitive imbalance between wild and domestic ungulates.     

Costs and benefits of within-group spatial position: a feeding competition model

An animal's within-group spatial position has several important fitness consequences. Risk of predation, time spent engaging in antipredatory behavior and feeding competition can all vary with respect to spatial position. Previous research has found evidence that feeding rates are higher at the group edge in many species, but these studies have not represented the entire breadth of dietary diversity and ecological situations faced by many animals. In particular the presence of concentrated, defendable food patches can lead to increased feeding rates by dominants in the center of the group that are able to monopolize or defend these areas. To fully understand the tradeoffs of within-group spatial position in relation to a variety of factors, it is important to be able to predict where individuals should preferably position themselves in relation to feeding rates and food competition. A qualitative model is presented here to predict how food depletion time, abundance of food patches within a group, and the presence of prior knowledge of feeding sites affect the payoffs of different within-group spatial positions for dominant and subordinate animals. In general, when feeding on small abundant food items, individuals at the front edge of the group should have higher foraging success. When feeding on slowly depleted, rare food items, dominants will often have the highest feeding rates in the center of the group. Between these two extreme points of a continuum, an individual's optimal spatial position is predicted to be influenced by an additional combination of factors, such as group size, group spread, satiation rates, and the presence of producer-scrounger tactics.     

Attraction to and learning from social cues in fruitfly larvae

We examined the use of social information in fruitfly larvae, which represent an ideal model system owing to their robust learning abilities, small number of neurons and well-studied neurogenetics. Focal larvae showed attraction to the distinct odour emanating from food occupied by other larvae. In controlled learning experiments, focal larvae preferred novel odours previously paired with food occupied by other larvae over novel odours previously paired with unoccupied food. When we gave groups of larvae a choice between food patches differing in quality, more larvae aggregated on the higher-quality food, suggesting that attraction to and learning about cues associated with other larvae can be beneficial. Furthermore, larvae were more likely to find the best available food patch in trials when that food patch was occupied by other larvae than in trials when that food patch was unoccupied. Our data suggest, however, that the benefits from joining others may be at least partially offset by the fitness costs of increased competition, because larvae reared in isolation did as well as or better than larvae reared in groups on three key fitness parameters: developmental rate, survival rate and adult dry body mass. Our work establishes fruitfly larvae as a highly tractable model species for further research on the mechanisms that modulate behaviour and learning in a social context.     

Reciprocal preening and food sharing in colour‐polymorphic nestling barn owls

Barn owl (Tyto alba) siblings preen and offer food items to one another, behaviours that can be considered prosocial because they benefit a conspecific by relieving distress or need. In experimental broods, we analysed whether such behaviours were reciprocated, preferentially exchanged between specific phenotypes, performed to avoid harassment and food theft or signals of hierarchy status. Three of the results are consistent with the hypothesis of direct reciprocity. First, food sharing was reciprocated in three‐chick broods but not in pairs of siblings, that is when nestlings could choose a partner with whom to develop a reciprocating interaction. Second, a nestling was more likely to give a prey item to its sibling if the latter individual had preened the former. Third, siblings matched their investment in preening each other. Manipulation of age hierarchy showed that food stealing was directed towards older siblings but was not performed to compensate for a low level of cooperation received. Social behaviours were related to melanin‐based coloration, suggesting that animals may signal their propensity to interact socially. The most prosocial phenotype (darker reddish) was also the phenotype that stole more food, and the effect of coloration on prosocial behaviour depended upon rank and sex, suggesting that colour‐related prosociality is state dependent.     

Seasonal variation in feeding habits and diet selection by wild boars in a semi-arid environment of Argentina

The wild boar, Sus scrofa, was first introduced for hunting purposes in Argentina in 1906 and presently occupies a wide range of habitats. Understanding the food habits of invasive species is important for predicting the effects of animal food consumption on the environment and on human activities, such as farming. The wild boar is an omnivorous, opportunistic species whose diet is determined by the relative abundance of different types of foods. In general, the wild boar’s diet has been widely studied in the world, both as a native and invasive species, but little is known regarding food resource selection in the Monte Desert biome. Our study assessed the seasonal variation in the diet of wild boars, as well as the nutritional quality of consumed items. Further, we determined the diet selection of this species. Diet analyses were based on faecal samples collected over two seasons (wet and dry) in 1 year. Herbs were the most frequently consumed food item, with wild boars showing a selection for them in both seasons. The wild boar uses food resources according to seasonal availability (larger trophic niche breadth under higher plant diversity, as in the wet season). In turn, within each season, it selects items of high forage quality and high carbohydrate contents. In conclusion, this foraging strategy enables wild boar to maximize energy budget through food selection in order to survive in a semi-arid environment such as the Monte Desert.     

Experimental manipulation of the timing of reproduction in the California vole

Summary The potential role of food and water in determining 1) the timing of the normal breeding season in the California vole, and 2) two frequently occurring exceptions to this normal pattern, are explored by using experimentally manipulated enclosed populations. Hypotheses derived from field observations were tested in the enclosed populations by the manipulation of green food, dry food, water, and vole density. The results of three experiments involving five populations are reported. In all populations densities were maintained at near-normal levels (475 to 1750 per ha). In all three experiments, it was shown that breeding was possible in the summer if sufficient food and water were available, although perhaps with reduced litter sizes and rates of growth and reproductive maturation of young. In two cases, severe weight losses and high mortality were induced by insufficient water. When water was provided, survivors recovered weight and reproductive competency in between five weeks and eight months. In three populations, starvation induced weight losses and mortality. In these cases recovery of the voles took only one month or less. In two of these last, the inadequate food situation was produced during the normally wet season by outbreaks of a European slug. It is concluded that available moisture is the most important factor in triggering both the end and beginning of the normal breeding season. Of course, inadequately fed mice do not breed at any season. Summer (dry season) breeding can occur when food and water conditions are adequate due to locally favorable conditions or very low population densities. Prolonged delays in growth and reproduction following the return of favorable conditions are most likely the consequence of chronic and severe water deprivation.     

Food Items Consumed by White-headed Langurs in Fusui, China

We studied the socioecology of white-headed langurs (Trachypithecus leucocephalus) from September 1997 to September 1998 in Fusui Precious Animal Reserve, SW Guangxi, China. We collected data on climate, phenology of food plant species, and foods consumed by langurs living in habitats with different levels of human disturbance. Feeding records showed that the most food is from less common plant species. Young leaves were the staple food item in all langur groups, and consumption correlates with availability. Consumption of mature leaves is not significantly correlated with their availability, but the langurs fed on them, and other food items such as fruits and seeds, when the availability of young leaves was low. Langurs in different areas had broadly similar diets, but they varied most in the proportion of supplementary items such as fruit. Groups in more disturbed habitat did not increase the overall proportion of mature leaves in their diet, but instead maintained their intake of young leaves from a greater diversity of species, and incorporated more immature fruit. Conservationists should direct efforts toward protection of rare plant species providing preferred food items, particularly supplementary foods at times when, and in areas where, preferred food items are less available.     

Male cleaner wrasses adjust punishment of female partners according to the stakes

Punishment is an important deterrent against cheating in cooperative interactions. In humans, the severity of cheating affects the strength of punishment which, in turn, affects the punished individual's future behaviour. Here, we show such flexible adjustments for the first time in a non-human species, the cleaner wrasse (Labroides dimidiatus), where males are known to punish female partners. We exposed pairs of cleaners to a model client offering two types of food, preferred 'prawn' items and less-preferred 'flake' items. Analogous to interactions with real clients, eating a preferred prawn item ('cheating') led to model client removal. We varied the extent to which female cheating caused pay-off reduction to the male and measured the corresponding severity of male punishment. Males punished females more severely when females cheated during interactions with high value, rather than low value, model clients; and when females were similar in size to the male. This pattern may arise because, in this protogynous hermaphrodite, cheating by similar-sized females may reduce size differences to the extent that females change sex and become reproductive competitors. In response to more severe punishment from males, females behaved more cooperatively. Our results show that punishment can be adjusted to circumstances and that such subtleties can have an important bearing on the outcome of cooperative interactions.