Chillingham Cattle: Dominance and Affinities and Access to Supplementary Food

A herd of cattle of natural sex ratio and age distribution, inhabiting a 134-ha park in northern England, was studied during supplementary feeding in 4 winters. Interactions could be summarised by conventional dominance hierarchies, more strictly linear and less stable among males than among females. Personal associations among individuals were not important, but affinities among social classes were, in determining the composition of feeding groups. Dominant males often fed in the same groups as dominant females. Dominant animals were less often seen to feed alone, implying that social dominance did not confer exclusive access to food. Cattle often fed in groups of two or three; certain combinations (notably those including two males, or one male and one female, or three calves) were stable, others unstable, notably combinations of females and calves, or of two or three females. This implies that females may defend resources more vigorously against other females than males do against other males.     

Warming and Resource Availability Shift Food Web Structure and Metabolism

Climate change disrupts ecological systems in many ways. Many documented responses depend on species'' life histories, contributing to the view that climate change effects are important but difficult to characterize generally. However, systematic variation in metabolic effects of temperature across trophic levels suggests that warming may lead to predictable shifts in food web structure and productivity. We experimentally tested the effects of warming on food web structure and productivity under two resource supply scenarios. Consistent with predictions based on universal metabolic responses to temperature, we found that warming strengthened consumer control of primary production when resources were augmented. Warming shifted food web structure and reduced total biomass despite increases in primary productivity in a marine food web. In contrast, at lower resource levels, food web production was constrained at all temperatures. These results demonstrate that small temperature changes could dramatically shift food web dynamics and provide a general, species-independent mechanism for ecological response to environmental temperature change.     

Temperature, Food Availability, and the Development of Marine Invertebrate Larvae

SYNOPSIS. Marine invertebrates develop in waters that extendfrom the poles to the equator, experiencing the full range ofenvironmental temperature and food conditions. How selectionhas modified their development under the influence of thesetwo factors has been a matter of debate. In this paper we arguethat the primary influence on developmental rate is temperature,while other factors such as food availability are much lessimportant. From existing literature we demonstrate that (1)developmental rates of both lecithotrophic and planktotrophicasteroids decrease in a similar way from the tropics to thepoles, as they do also in other groups of invertebrates (echinoids,molluscs, crustaceans), and (2) rates of development at anyone temperature cluster around the function describing the effectof temperature, without any relationship to egg size, suggestingthat developmental rates are near the maximum for a given temperatureregardless of other variables such as nutrition. We also investigatedthe response of development to temperature in four species ofplanktotrophic asteroids, one tropical, one temperate, two polar.There was limited temperature compensation among these fourspecies, but little or no apparent ability to compensate forthe retarding effects of reduced temperature within species.Arrhenius analysis of the data suggests that Q₁₀ values forthe upper region of each species' tolerance range are approximately2, indicating that enzyme-based reactions have evolved to beclosely integrated with uncatalyzed, temperature-dependent,physicalchemical processes. Values of Q₁₀ at lower regions ofthe tolerance range, on the other hand, range between 9.5 and14.7, indicative of abrupt temperature-dependent shifts in reactionequilibria, or in the organization of macromolecules and membranes.We conclude that temperature itself, rather than egg size, food,or other variables, best explains observed latitudinal differencesin developmental rates in marine invertebrates.     

Testosterone and Linear Social Dominance Status in Captive Male Dabbling Ducks in Winter

Dominance hierarchies play an important role in avoidance and/or solving conflicts in gregarious species. In dabbling ducks (Anas species), dominance allows for feeding‐site monopolization in winter quarters where resources are generally limited. In addition, male social rank should theoretically favour access to mates. Dominance rank can be associated with morphological traits, and is often correlated with aggressiveness, a behavioural trait generally related to high testosterone levels. In this study, we investigated the existence of a winter group structure based on dominance relationships and tested for a linear hierarchy, in three species of captive male dabbling ducks (mallard Anas platyrhynchos, pintail A. acuta and wigeon A. penelope). We then analysed the relationship between dominance ranks, morphological parameters and testosterone levels measured in early (Oct.) and mid‐winter (Dec./Jan.). We found that the three male groups of the three species exhibited a linear hierarchy. Testosterone levels differed during winter and between species. Morphologic measurements, body mass and body condition were not correlated with individual dominance ranks, whereas dominant males had higher testosterone levels than subordinates. The slopes of the relationships were similar between species and winter period, but the y‐intercepts differed between species and between early and mid‐winter phases. The linear hierarchy found in the three species indicates that dominance relationships strongly structure dabbling duck groups in winter. Lack of correlation between rank and morphological characters, but correlation of rank with testosterone levels suggests that social rank is more dependent on behavioural traits such as aggressive behaviour. The differences between species and winter periods are discussed in relation to migration and wintering phenology.     

Dominance, Status Signals and Coloration in Male Mandrills (Mandrillus sphinx)

Where individuals contest access to a resource, escalated physical fighting presents a risk to all involved. The requirement for mechanisms of conflict management has led to the evolution of a variety of decision rules and signals that act to reduce the frequency of aggression during competitive encounters. We examined strategies of conflict management in male mandrills (Mandrillus sphinx) living in two semi‐free‐ranging groups in Gabon. Adult male mandrills are large (31 kg), with long canines, making the costs of conflict potentially very high. We found that males formed dominance hierarchies, but that male–male relationships were characterized by avoidance, appeasement and ignoring. Fights were rare, but could result in death. Examination of the relationship between dominance and signaling showed that males use facial and gestural signals to communicate dominance and subordinance, avoiding escalated conflict. Male mandrills also possess rank‐dependent red coloration on the face, rump and genitalia, and we examined the hypothesis that this coloration acts as a ‘badge of status’, communicating male fighting ability to other males. If this is the case, then similarity in color should lead to higher dyadic rates of aggression, while males that differ markedly should resolve encounters quickly, with the paler individual retreating. Indeed, appeasement (the ‘grin’ display), threats, fights and tense ‘stand‐off’ encounters were significantly more frequent between similarly colored males, while clear submission was more frequent where color differences were large. We conclude that male mandrills employ both formal behavioral indicators of dominance and of subordination, and may also use relative brightness of red coloration to facilitate the assessment of individual differences in fighting ability, thereby regulating the degree of costly, escalated conflict between well‐armed males.     

Shoaling Decisions in Angelfish: The Roles of Social Status and Familiarity

Abstract Past research has shown that angelfish, Pterophyllum scalare , are capable of discriminating between shoals composed of familiar dominant and subordinate companions, whereas they show no preference for shoals of unfamiliar conspecifics. In this study, the relative importance of familiarity and social status (shoal factors) on the shoaling decision of juvenile angelfish, which also differed in social status (individual factor), was investigated as very little is known about such tradeoffs in fishes. Dominant and subordinate individuals were given the choice to shoal with a group of conspecifics composed of familiar dominants vs. unfamiliar dominants and composed of familiar subordinates vs. unfamiliar subordinates. The findings demonstrate that fish with different social status differed in their shoaling preference. Subordinate test fish showed a preferential association with familiar subordinates over unfamiliar subordinates, but preferred the unfamiliar shoal over the familiar one when both shoals were constituted by dominant individuals. The shoaling behaviour shown by dominant test fish, on the other hand, indicated no significant preference for any of the shoals regardless of their composition. A replicate preference test carried out 2 h 30 min after the first one indicated that the association pattern was relatively consistent. Results suggest that angelfish are able to differentiate between the stimulus shoals and demonstrate that the pervasive influence of familiarity on the shoaling decision may be restrained or overridden by the composition of the familiar shoals and the social status of the test fish.     

Feeding and Stocking Up: Radio-Labelled Food Reveals Exchange Patterns in Ants

Food sharing is vital for a large number of species, either solitary or social, and is of particular importance within highly integrated societies, such as in colonial organisms and in social insects. Nevertheless, the mechanisms that govern the distribution of food inside a complex organizational system remain unknown.Using scintigraphy, a method developed for medical imaging, we were able to describe the dynamics of food-flow inside an ant colony. We monitored the sharing process of a radio-labelled sucrose solution inside a nest of Formica fusca. Our results show that, from the very first load that enters the nest, food present within the colony acts as negative feedback to entering food. After one hour of the experiments, 70% of the final harvest has already entered the nest. The total foraged quantity is almost four times smaller than the expected storage capacity. A finer study of the spatial distribution of food shows that although all ants have been fed rapidly (within 30 minutes), a small area representing on average 8% of the radioactive surface holds more than 25% of the stored food. Even in rather homogeneous nests, we observed a strong concentration of food in few workers. Examining the position of these workers inside the nest, we found heavily loaded ants in the centre of the aggregate. The position of the centre of this high-intensity radioactive surface remained stable for the three consecutive hours of the experiments.We demonstrate that the colony simultaneously managed to rapidly feed all workers (200 ants fed within 30 minutes) and build up food stocks to prevent food shortage, something that occurs rather often in changing environments. Though we expected the colony to forage to its maximum capacity, the flow of food entering the colony is finely tuned to the colony''s needs. Indeed the food-flow decreases proportionally to the food that has already been harvested, liberating the work-force for other tasks.     

Dominance and deference: Men inhibit creative displays during mate competition when their competitor is strong

Dominance is a form of social status based on an individual's ability to inflict costs (e.g. physical aggression) onto others. Subordinate individuals defer to dominant individuals in order to avoid physical aggression. We hypothesized that relatively subordinate men defer to dominant men by inhibiting creative displays during mate competition. Male participants were led to believe they were competing for a date with an attractive female. Participants believed they were competing against either a strong or weak male. During an interview with the attractive female, participants were prompted to display their creativity to the female by telling funny jokes and interesting stories. We found that participants competing against a strong male were less likely to tell jokes and less likely to tell stories. Additionally, participants competing against a strong male told jokes that were less funny and less elaborate.     

Experiments in Globalisation,Food Security and Land Use Decision Making

The globalisation of trade affects land use, food production and environments around the world. In principle, globalisation can maximise productivity and efficiency if competition prompts specialisation on the basis of productive capacity. In reality, however, such specialisation is often constrained by practical or political barriers, including those intended to ensure national or regional food security. These are likely to produce globally sub-optimal distributions of land uses. Both outcomes are subject to the responses of individual land managers to economic and environmental stimuli, and these responses are known to be variable and often (economically) irrational. We investigate the consequences of stylised food security policies and globalisation of agricultural markets on land use patterns under a variety of modelled forms of land manager behaviour, including variation in production levels, tenacity, land use intensity and multi-functionality. We find that a system entirely dedicated to regional food security is inferior to an entirely globalised system in terms of overall production levels, but that several forms of behaviour limit the difference between the two, and that variations in land use intensity and functionality can substantially increase the provision of food and other ecosystem services in both cases. We also find emergent behaviour that results in the abandonment of productive land, the slowing of rates of land use change and the fragmentation or, conversely, concentration of land uses following changes in demand levels.     

Food and the Status Quest: An Interdisciplinary Perspective

Food and the Status Quest: An Interdisciplinary Perspective. Polly Wiessner and Wulf Schiefenhövel. eds. Providence, RI: Berghahn Books, 1996. 294 pp.     

Impact of Environmental Disturbance on the Stability and Benefits of Individual Status within Dominance Hierarchies

Changes in environmental conditions affect social interactions and thus may modify an individual's competitive ability within a social group. We subjected three‐spined sticklebacks, Gasterosteus aculeatus, housed in groups of four individuals, to environmental perturbations to assess the impact on dominance hierarchy stability. Hierarchy stability decreased during increased turbulence or lowered water levels (‘simulated drought’) whereas control hierarchies became more stable in a constant environment. The dominant individual either became more aggressive and remained dominant during the environmental manipulation or was usurped by a lower rank member. Only simulated drought affected rates of aggression where levels of aggression were higher after the water level was dropped which may be the result of an increased encounter rate in these conditions. When there were large size differences between the group members, the dominant individual performed the greatest amount of aggression and ate the largest proportion of food and there was little aggressive behaviour from the lower ranks. In groups of similar‐sized individuals, aggression was much higher. The benefit of being dominant was to gain weight over the experimental period whereas ranks 2 and 3 lost weight. The lowest rank, 4, actually gained weight over the experimental period. This study suggests that it would benefit an individual to be dominant, highly aggressive and gain weight or be submissive, avoid aggressive interactions and, by sneakily obtaining access to food, also gain weight. Altering environmental conditions has a profound effect on social behaviour in this study.     

Interactions between Seagrass Complexity,Hydrodynamic Flow and Biomixing Alter Food Availability for Associated Filter-Feeding Organisms

Seagrass shoots interact with hydrodynamic forces and thereby a positively or negatively influence the survival of associated species. The modification of these forces indirectly alters the physical transport and flux of edible particles within seagrass meadows, which will influence the growth and survivorship of associated filter-feeding organisms. The present work contributes to gaining insight into the mechanisms controlling the availability of resources for filter feeders inhabiting seagrass canopies, both from physical (influenced by seagrass density and patchiness) and biological (regulated by filter feeder density) perspectives. A factorial experiment was conducted in a large racetrack flume, which combined changes in hydrodynamic conditions, chlorophyll a concentration in the water and food intake rate (FIR) in a model active filter-feeding organism (the cockle). Results showed that seagrass density and patchiness modified both hydrodynamic forces and availability of resources for filter feeders. Chlorophyll a water content decreased to 50% of the initial value when densities of both seagrass shoots and cockles were high. Also, filter feeder density controlled resource availability within seagrass patches, depending on its spatial position within the racetrack flume. Under high density of filter-feeding organisms, chlorophyll a levels were lower between patches. This suggests that the pumping activity of cockles (i.e. biomixing) is an emergent key factor affecting both resource availability and FIR for filter feeders in dense canopies. Applying our results to natural conditions, we suggest the existence of a direct correlation between habitat complexity (i.e. shoot density and degree of patchiness) and filter feeders density. Fragmented and low-density patches seem to offer both greater protection from hydrodynamic forces and higher resource availability. In denser patches, however, resources are allocated mostly within the canopy, which would benefit filter feeders if they occurred at low densities, but would be limiting when filter feeder were at high densities.     

Distributions of Competing Container Mosquitoes Depend on Detritus Types, Nutrient Ratios, and Food Availability

Coexistence of competitors may result if resources are sufficiently abundant to render competition unimportant, or if species differ in resource requirements. Detritus type has been shown to affect interspecific competitive outcomes between Aedes albopictus (Skuse) and Aedes aegypti (L.) larvae under controlled conditions. We assessed the relationships among spatial distributions of detritus types, nutrients, and aquatic larvae of these species in nature. We collected mosquitoes, water, and detritus from artificial containers across 24 Florida cemeteries that varied in relative abundances of Ae. aegypti and Ae. albopictus.We measured nutrient content of fine particulate organic matter in water samples as total N, P, and C and ratios of these nutrients. We quantified food availability via a bioassay, raising individual Aedes larvae in the laboratory in standard volumes of field-collected, particulate-containing water from each cemetery. Quantities of detritus types collected in standard containers were significant predictors of nutrients and nutrient ratios. Nutrient abundances were significant predictors of relative abundance of Ae. aegypti, and of larval survival and development by both species in the bioassay. Survival and development of larvae reared in particulate-containing water from sites decreased with decreasing relative abundance of Ae. aegypti. These data suggest that N, P, and C availabilities are determined by detritus inputs to containers and that these nutrients in turn determine the feeding environment encountered by larvae, the intensity of interspecific competition among larvae, and subsequent relative abundances of species at sites. Detritus inputs, nutrients, and food availability thus seem to contribute to distributions of Ae. aegypti and Ae. albopictus in cemetery containers throughout Florida.     

Relationship Status and Relationship Instability,but Not Dominance,Predict Individual Differences in Baseline Cortisol Levels

We investigated variation in baseline cortisol levels in relation to relationship status (single or in a relationship), relationship characteristics (length, stability, presence or absence of clear dominance), or individual attributes (dominant or subordinate status, relative physical attractiveness, relationship worries). Study participants were 77 men and 75 women aged between 18 and 38 years. Individuals in romantic relationships had lower cortisol levels than singles. Individuals of African ethnicity, however, showed the opposite pattern. Individuals who perceived their relationship to be highly unstable had higher cortisol levels. Aside from African-Americans, married individuals reported the lowest relationship instability and the lowest cortisol levels, followed by individuals in long-term relationships, and by individuals in short-term relationships. The presence or absence of clear dominance in the relationship, dominance status, or relationship worries did not affect cortisol levels. Therefore relationship status and relationship instability were better predictors of variation in cortisol (presumably through stress-related mechanisms) than individual attributes.     

Sampling Effects on Food Availability Estimates: Phenological Method,Sample Size,and Species Composition1

It is currently recognized that the method used to collect phenology data can affect the resulting pattern. However, to date, the underlying influences have not been examined. To examine potential methodological biases, we investigated the effects of phenological method, sample size, and species composition on phenological patterns using data collected to estimate food availability for three primate species in Ranomafana National Park, Madagascar. Two phenological methods were compared: selected tree observations and systematic transect monitoring. By generating bootstrapped subsamples derived from the transect tree data set, we simulated two selected tree data sets and subsequently compared the observed and bootstrapped values. Although the observed values fell within the bootstrapped confidence inrervals, suggesting no significant effects of sampling protocol or sample size, additional lines of evidence suggest otherwise. Observed samples composed of different plant species, whether based on species attributes such as life-form or categories such as food versus nonfood plants, consistently produced different phenological patterns. Wide confidence intervals of the bootstrapped samples indicate high individual variation in reproductive activity within the species sampled. Finally, we compared how well the selected tree and the transect methods represented food items used by all three primate species studied and found that transect methods sampled a wider diversity of food items, including rare foods, and a higher percentage of main primate food items than selected tree methods.     

Indirect Costs of Parasitism are Shaped by Variation in the Type of Immune Challenge and Food Availability

Parasites can inflict indirect fitness costs to their hosts by eliciting costly immune responses. These costs depend on the type and amount of immunostimulants presented to the host immune system but also on the amount of resources available to fuel host immune responses. Here, we investigated how the relative costs of two different types of immune challenge are modulated by variation in food availability. We injected nestling tawny owls (Strix aluco) with either 10 μg of phytohaemagglutinin (PHA) or 20 μg of lipopolysaccharide (LPS), and subsequently raised them under two different food regimes (food-restricted vs. ad libitum). After controlling for food consumption, we found that LPS-injected nestlings lost more body mass than PHA-injected ones only when food-restricted. We also found that body mass gain of owlets fed ad libitum decreased with the intensity of the skin swelling response against LPS, but not PHA. These experimental and correlative results suggest that nestling tawny owls suffered greater immune costs when treated with LPS than PHA, and that variation in the costs of two different types of immune challenge can be exacerbated under conditions of low food availability. Our study highlights the importance of taking into consideration the interplay between host immunity and nutrition in the study of indirect costs of parasitism.     

Home Range Size Variation in Female Arctic Grizzly Bears Relative to Reproductive Status and Resource Availability

The area traversed in pursuit of resources defines the size of an animal’s home range. For females, the home range is presumed to be a function of forage availability. However, the presence of offspring may also influence home range size due to reduced mobility, increased nutritional need, and behavioral adaptations of mothers to increase offspring survival. Here, we examine the relationship between resource use and variation in home range size for female barren-ground grizzly bears (Ursus arctos) of the Mackenzie Delta region in Arctic Canada. We develop methods to test hypotheses of home range size that address selection of cover where cover heterogeneity is low, using generalized linear mixed-effects models and an information-theoretic approach. We found that the reproductive status of female grizzlies affected home range size but individually-based spatial availability of highly selected cover in spring and early summer was a stronger correlate. If these preferred covers in spring and early summer, a period of low resource availability for grizzly bears following den-emergence, were patchy and highly dispersed, females travelled farther regardless of the presence or absence of offspring. Increased movement to preferred covers, however, may result in greater risk to the individual or family.     

Estimation of Dietary Iron Bioavailability from Food Iron Intake and Iron Status

Currently there are no satisfactory methods for estimating dietary iron absorption (bioavailability) at a population level, but this is essential for deriving dietary reference values using the factorial approach. The aim of this work was to develop a novel approach for estimating dietary iron absorption using a population sample from a sub-section of the UK National Diet and Nutrition Survey (NDNS). Data were analyzed in 873 subjects from the 2000–2001 adult cohort of the NDNS, for whom both dietary intake data and hematological measures (hemoglobin and serum ferritin (SF) concentrations) were available. There were 495 men aged 19–64 y (mean age 42.7±12.1 y) and 378 pre-menopausal women (mean age 35.7±8.2 y). Individual dietary iron requirements were estimated using the Institute of Medicine calculations. A full probability approach was then applied to estimate the prevalence of dietary intakes that were insufficient to meet the needs of the men and women separately, based on their estimated daily iron intake and a series of absorption values ranging from 1–40%. The prevalence of SF concentrations below selected cut-off values (indicating that absorption was not high enough to maintain iron stores) was derived from individual SF concentrations. An estimate of dietary iron absorption required to maintain specified SF values was then calculated by matching the observed prevalence of insufficiency with the prevalence predicted for the series of absorption estimates. Mean daily dietary iron intakes were 13.5 mg for men and 9.8 mg for women. Mean calculated dietary absorption was 8% in men (50^th percentile for SF 85 µg/L) and 17% in women (50^th percentile for SF 38 µg/L). At a ferritin level of 45 µg/L estimated absorption was similar in men (14%) and women (13%). This new method can be used to calculate dietary iron absorption at a population level using data describing total iron intake and SF concentration.