Vigilance Behaviour in Grazing African Antelopes
TL;DR: Time spent looking varied with position within the group; this effect was strongest in closed habitats, where central animals tended to scan least and feed most, and within species, animals inclosed habitats, those with dense vegetation, tended to spend more time in looking than did animals in the open.
Abstract: African antelope may devote a large proportion of their foraging time to looking around. The factors affecting such vigilance behaviour are examined for grazing antelope, five species being studied in detail. The proportion of time spent looking decreased as species body weight increased. Within species, animals in closed habitats, those with dense vegetation, tended to spend more time in looking than did animals in the open. There was some evidence that vigilance, presumably for predators, was shared by group members, but in one species, impala, vigilance apparently increased with group size and with proximity to neighbours. Time spent looking varied with position within the group; this effect was strongest in closed habitats, where central animals tended to scan least and feed most. Vigilance increased as feeding success decreased, partly due to mutual interference between looking and feeding. The possible social, foraging and predator-detection values of vigilance are discussed. A simple model is introduced to help explain the effects of cover and to facilitate further discussion.
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TL;DR: In this article , the authors compared the antipredator behaviour of two savannah antelopes, topi, Damaliscus lunatus, and Thomson's gazelle, Eudorcas thomsonii, between the relatively undisturbed areas in the interior of the Maasai Mara National Reserve (Kenya) and the peripheral areas next to human settlements by the reserve boundary.
01 Jan 2018
TL;DR: In this article, the social behavior of poultry based on the abundant existing literature for laying hens and meat chickens is discussed, including discussion of reproductive behavior and the impact of sexual conflict on bird fertility and welfare.
Abstract: All poultry species live in groups. These groups can change in structure and composition depending on the season, group size, or availability of resources. Living in groups protects animals from predators and facilitates finding new resources, among other benefits. But living in groups also has negative aspects that can impact on the welfare of poultry, especially in terms of competition for resources reflected in the level of aggressive interactions. Understanding the basic evolutionary principles that caused birds to live together, and their capacity to respond in a dynamic way to changes in the physical and social environment, is crucial to implementing management strategies that reflect the nature of their social behavior, thus allowing optimal welfare. In this chapter, the social behavior of poultry based on the abundant existing literature for laying hens and meat chickens is discussed. The chapter also includes discussion of reproductive behavior and the impact of sexual conflict on bird fertility and welfare.
Dissertation•
01 Jun 2010
TL;DR: Despite the reef supporting over fifty herbivorous fish species and six macroalgal browsing species, a single species, Naso unicornis, was almost solely responsible for the removal of Sargassum biomass, revealing a distinct pattern in browsing across the continental shelf in the northern GBR.
Abstract: Herbivory is a key process structuring plant communities in both terrestrial and aquatic ecosystems, with variation in herbivory often being related to shifts between contrasting groups of primary producers. On coral reefs, regional reductions in herbivores have underpinned shifts from coral-dominance to dominance by fleshy macroalgae. The capacity to remove macroalgae is, therefore, viewed as a key process in both preventing and reversing such transitions. The present study compared the role of macroalgal browsing fishes across two distinct exposure gradients, both among habitats within a single reef and across several reefs spanning the continental shelf, and among patches of differing macroalgal densities. Finally, the role of a second group of herbivorous fishes, the territorial damselfishes, in influencing macroalgal removal rates and shaping macroalgal distributions was explored.
Browsing intensity was quantified across eight habitats of varying depth and wave exposure on a mid-shelf reef in the northern Great Barrier Reef (GBR) using assays of two species of Sargassum. Removal rates of Sargassum varied significantly amongst habitats, with both species displaying broadly similar patterns. Reductions in Sargassum biomass were highest within the shallow habitats on the exposed aspect of the reef (81.4–91.6 %.d-1), lowest within the deeper exposed habitats (3.8–13.4 %.d-1), and intermediate within the sheltered habitats (37.9–76.5 % d-1). Surprisingly the rates of removal of Sargassum displayed no relationship with visual census estimates of the density or biomass of all roving herbivorous fishes or macroalgal browsing fishes, either collectively or independently. Stationary underwater video cameras revealed that, despite the reef supporting over fifty herbivorous fish species and six macroalgal browsing species, a single species, Naso unicornis, was almost solely responsible for the removal of Sargassum biomass. Of the 42,246 bites taken from the Sargassum across all habitats, N. unicornis accounted for 89.8 % (37,982) of the total bites, and 94.6 % of the total mass standardized bites.
Sargassum assays revealed a distinct pattern in browsing across the continental shelf in the northern GBR, with the highest rates of removal recorded on mid-shelf reefs (55.2–79.9 %.d-1) and decreasing significantly on inner-shelf reefs (10.8–17.0 %.d-1). The low removal rates on inner-shelf reefs appeared to be directly related to the high cover of macroalgae on those reefs. Reductions in Sargassum biomass were also initially low on outer-shelf reefs (10.1–10.4 %.d-1), but increased markedly (32.1-73.4 %.5h-1) after the resident fishes were allowed several days to familiarize themselves with the Sargassum. Despite considerable cross-shelf variation in the rates of removal of Sargassum, there was little variation in the agents of macroalgal removal across all reefs. Feeding on the transplanted Sargassum was again dominated by a single browsing species. N. unicornis accounted for 82 % of all mass standardized bites and explained over 80 % of the total variation in the reduction in Sargassum biomass across all reefs and habitats. Although the majority of this feeding activity was recorded on the midand outer-shelf reefs, N. unicornis accounted for over 72 % of the recorded feeding on the inner-shelf reefs.
The territory composition and effect of resident damselfish on the removal of Sargassum was quantified for six common species of damselfish on a mid-shelf reef in the northern GBR. The functional composition of algal communities within territories varied markedly among species. The territories of four species were characterized by algal turfs, while the territories of two species were characterized by foliose and leathery brown macroalgae. Sargassum, a generally rare alga on mid-shelf reefs, was a particularly common alga within Dischistodus prosopotaenia territories. D. prosopotaenia was the only species to retain the transplanted Sargassum, with only a minimal reduction in Sargassum biomass (1.1 %.d-1) being recorded within their territories. In contrast, reductions in Sargassum biomass were high in areas adjacent to D. prosopotaenia territories (83.8 %.d-1), and within and adjacent to the territories of the five remaining damselfish species (76.2 - 92.5 %.d-1). Overall, only D. prosopotaenia provided a refuge for leathery brown macroalgae, and may facilitate the development of this macroalgae on mid-shelf reefs of the GBR.
Habitat patches that varied in the spatial arrangement and density of macroalgae (0.25-6.23 kg.m-2) were created on an inshore reef in the central GBR using transplanted Sargassum. Feeding on the Sargassum was dominated by two species, Kyphosus vaigiensis and N. unicornis. Both species displayed a preference for the relatively open habitat patches with low cover and biomass of Sargassum; only switching to the higher density patches after much of the Sargassum biomass within the lower density patches had been consumed. Similarly, grazing on the algal turf covered substratum within the habitat patches displayed an exponential decline with increasing Sargassum biomass. These feeding preferences appeared not to be related to bottom-up factors as food availability was proportional to macroalgal density for browsers and broadly comparable among habitat patches for grazers. It appears more likely that the avoidance of the higher macroalgal density patches was related to an increase in the perceived risk of predation.
Overall, the consumption rates of Sargassum in the present study provided strong evidence for the potential role of browsing fishes in limiting the distribution of adult Sargassum on mid- and outer-shelf reefs of the GBR. Browsing intensity was, however, moderated by the presence of D. prosopotaenia and the density of the Sargassum presented. These negative interactors are important and provide the mechanistic bases through which Sargassum may colonize new locations, and expand and persist once established. Despite some evidence of latitudinal variation on inshore reefs, the reliance on a single species removing Sargassum across a range of habitats and reefs in the northern GBR was striking. This limited redundancy, both within and across local (0.1 – 40 km) scales, highlights the potential for single-species functional groups and emphasizes the importance of looking beyond biological diversity as a source of ecological stability.
Cites background from "Vigilance Behaviour in Grazing Afri..."
...Alternatively, consumers may avoid complex habitats if their ability to detect predators is reduced (Underwood 1982; Riginos and Grace 2008), or the physical structure obstructs their movements, limiting...
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TL;DR: An agent-based spatially explicit model is used to investigate the effect of contagious fleeing after detection of predators on survival rate and it is found that, as expected, in a residential group, a larger visual field enhances survival rate.
Cites background from "Vigilance Behaviour in Grazing Afri..."
...Empirical observations on groups have been done on many species, for example: antelopes (Underwood 1982, Hunter & Skinner 1998, Kröschel et al. 2017); baboons (Bettridge & Dunbar 2012); marmots (Blumstein et al. 2001); fiddler crabs (Zeil & Hemmi 2006); meerkats and mongoose (le Roux et al 2009);…...
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TL;DR: This paper observed a total of 64 instances of interspecific contact between larger-gregarious sika deer and smaller-solitary Japanese serows over eight years field observations and found that serows showed antagonistic behaviour, such as walk push and chasing, to deer, but could rarely displace deer.
Abstract:
In ungulate assemblages, although interspecific differences in body size and gregariousness are thought to have a direct impact on winning or losing in interference competition, this has not been fully investigated. We observed a total of 64 instances of interspecific contact between larger-gregarious sika deer and smaller-solitary Japanese serows over eight years field observations. Deer-to-serow aggression were never observed. Whereas, serows showed antagonistic behaviour, such as walk push and chasing, to deer, but could rarely displace deer. Serows showed higher alertness to deer than deer did to serows. These results suggest that larger-gregarious ungulates do not necessarily exclude smaller-solitary ones and serows are sensitive to the presence of deer. Differences in aggressiveness and alertness between deer and serows may reflect differences in territoriality: serows may be more sensitive to the invasion of deer into their territory. Serows’ sensitivity to deer may have a negative effect on their population.
References
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TL;DR: Seven major types of sampling for observational studies of social behavior have been found in the literature and the major strengths and weaknesses of each method are pointed out.
Abstract: Seven major types of sampling for observational studies of social behavior have been found in the literature. These methods differ considerably in their suitability for providing unbiased data of various kinds. Below is a summary of the major recommended uses of each technique: In this paper, I have tried to point out the major strengths and weaknesses of each sampling method. Some methods are intrinsically biased with respect to many variables, others to fewer. In choosing a sampling method the main question is whether the procedure results in a biased sample of the variables under study. A method can produce a biased sample directly, as a result of intrinsic bias with respect to a study variable, or secondarily due to some degree of dependence (correlation) between the study variable and a directly-biased variable. In order to choose a sampling technique, the observer needs to consider carefully the characteristics of behavior and social interactions that are relevant to the study population and the research questions at hand. In most studies one will not have adequate empirical knowledge of the dependencies between relevant variables. Under the circumstances, the observer should avoid intrinsic biases to whatever extent possible, in particular those that direcly affect the variables under study. Finally, it will often be possible to use more than one sampling method in a study. Such samples can be taken successively or, under favorable conditions, even concurrently. For example, we have found it possible to take Instantaneous Samples of the identities and distances of nearest neighbors of a focal individual at five or ten minute intervals during Focal-Animal (behavior) Samples on that individual. Often during Focal-Animal Sampling one can also record All Occurrences of Some Behaviors, for the whole social group, for categories of conspicuous behavior, such as predation, intergroup contact, drinking, and so on. The extent to which concurrent multiple sampling is feasible will depend very much on the behavior categories and rate of occurrence, the observational conditions, etc. Where feasible, such multiple sampling can greatly aid in the efficient use of research time.
12,470 citations
TL;DR: An antithesis to the view that gregarious behaviour is evolved through benefits to the population or species is presented, and simply defined models are used to show that even in non-gregarious species selection is likely to favour individuals who stay close to others.
3,343 citations
Additional excerpts
...The 'selfish herd' (HAMILTON, 1971)...
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TL;DR: The paper describes different feeding styles among antelope, in terms of selection of food items and coverage of home ranges, and argues that these feeding styles bear a relationship to maximum group size of feeding animals through the influence of dispersion ofFood items upon group cohesion.
Abstract: The types of social organisation displayed by the African antelope species have been assigned in this paper to five classes, distinguished largely by the strategies used by the reproductively active males in securing mating rights, and the effects of those strategies on other social castes. The paper attempts to show that these strategies are appropriate to each class because of the effects of other, ecological, aspects of their ways of life. The paper describes different feeding styles among antelope, in terms of selection of food items and coverage of home ranges. It argues that these feeding styles bear a relationship to maximum group size of feeding animals through the influence of dispersion of food items upon group cohesion. The feeding styles also bear a relationship to body size and to habitat choice, both of which influence the antelope species' antipredator behaviour. Thus feeding style is related to anti-predator behaviour which, in many species, influences minimum group size. Group size and the pattern of movement over the annual home range affect the likelihood of females being found in a given place at a given time, and it is this likelihood which, to a large extent, determines the kind of strategy a male must employ to achieve mating rights. The effects of the different strategies employed by males can be seen in such aspects of each species' biology as sexual dimorphism, adult sex ratio, and differential distribution of the sexes.
2,088 citations
"Vigilance Behaviour in Grazing Afri..." refers background in this paper
...Such habitat differences may have influenced the evolution of social and anti-predator behaviour in antelope (GEIST, 1974; JARMAN, 1974; ESTES, 1974) and may also affect both predator and prey behaviour on a day to day basis (SCHALLER, 1972; KRUUK, 1972; CURIO, 1976; EDMUNDS, 1974)....
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...If scanning reduces predation, it may take up less of the large animals' time either because both the number and the range of potential predators are smaller (JARMAN, 1974; GEIST, 1974), or because these antelope, being found in large groups, either are (a) less easy for a predator to find, (b) share vigilance with other group members (CARACAO et al....
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...The smaller and, according to JARMAN (1974), the more selective species are those which show significant correlations between the rate of looking and indices of feeding success, supporting the possibility that scanning forms a part of foraging behaviour....
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1,193 citations
Book•
21 Sep 1976
TL;DR: This chapter discusses hunting for Prey, the Diversity of Hunting Methods, and the Motivation Underlying Feeding Responses of Predator-Prey Interactions.
Abstract: 1 Internal Factors.- A. Hunger: Expression through Overt behavior.- I. Predatory Schedules.- 1. Patterns of Satiation.- 2. Feast and Famine.- II. Hunger and Diel Rhythms.- III. The Ramification of Hunger Effects.- 1. Capture-eliciting Prey Stimuli.- 2. Search behavior.- IV. The Motivation Underlying Feeding Responses.- 1. Hunger Thresholds of Feeding Response Components.- 2. The Complexity of Predatory Motivation.- V. The Diversity of Foraging Tactics.- VI. Feeding Components Affected and not Affected by Hunger.- B. The Control of Feeding Responses by Factors Other than Hunger.- I. The Readiness to Hunt.- II. Prey Storing.- III. Providing Food for Dependent Family Members.- C. The Problem of Specific Hungers.- I. Switching of Prey.- II. The Prey-density Predation Curve.- III. Swamping the Appetite of Predators.- D. Daily and Annual Rhythms in Predator-Prey Interactions.- I. Daily Rhythm of Predation.- II. Daily Activity Patterns of the Prey.- III. Annual Rhythm of Predation.- 2 Searching for Prey.- A. Path of Searching and Scanning Movements.- B. Area-concentrated Search.- I. Short-term Area Concentration.- 1. Living Scattered and Area-concentrated Search.- 2. The Nature of the Path Changes.- 3. Search Behavior after the Disappearance of Prey.- II. Long-term Area Concentration.- III. One-prey : One-place Association.- C. Object-concentrated Search.- I. Existence and Properties of "Searching Image".- 1. Ecological Evidence.- 2. Experimental Evidence.- II. Social Facilitation of Searching Image Formation.- III. Searching Image and "Training Bias".- IV. Searching Image and Profitability of Hunting.- 1. Ecological Evidence for Profitability of Hunting.- 2. Experimental Evidence for Profitability of Hunting.- V. Prey-specific Expectation.- VI. Ecological Implications of Searching Image.- 3 Prey Recognition.- A. The Stimulus-specificity of Prey Capture.- I. Capture-eliciting Prey Stimuli.- II. Capture-inhibiting Prey Stimuli.- B. One-prey : One-response Relationships.- C. The Assessment of the Circumstances of a Hunt.- D. Prey Recognition by Prey-related Signals.- E. Prey Stimulus Summation.- F. Novelty Versus Familiarity.- I. The Rejection of Novel Prey.- II. Familiarization with Prey and Its Consequences.- G. The Multi-channel Hypothesis of Prey Recognition.- 4 Prey Selection.- A. Preying upon the Weak and the Sick.- B. Preying upon the Odd and the Conspicuous.- C. The Mechanics of Prey Selection.- D. Evolutionary Implications.- 5 Hunting for Prey.- A. Modes of Hunting.- I. Hunting by Speculation.- II. Stalking and Ambushing.- 1. Stalking.- 2. Ambushing.- III. Prey Attack under Disguise.- IV. Pursuit of the Prey.- 1. Changes of Velocity of Attack (Pursuit).- 2. Interception of the Flight Path.- 3. Counteradaptations of the Prey.- V. Exhausting Dangerous Prey.- VI. Insinuation.- VII. Scavenging and Cleptoparasitism.- 1. Modes and Extent.- 2. Cleptoparasitism and Competition.- 3. Counter-measures of the Robbed.- VIII. Tool-use.- IX. Mutilation.- B. The Diversity of Hunting Methods.- I. Prey-specific Methods.- II. Situation-specific Methods.- III. Mechanisms and Causes of Predatory Versatility.- 1. General.- 2. Individual Predatory Repertories.- 3. The Persistence of Individual Traits.- 4. Predatory Specialization and Structural Modification.- 5. Predatory Versatility in Relation to Prey Availability.- C. Behavioral Aspects of Hunting Success.- I. A Comparison of Hunting Success across Predator Species.- II. Variables Influencing Hunting Success within Predator Species.- III. Aspects of Communal Hunting.- 1. Modes and Properties of Communal Hunting.- 2. Factors Conducive to Communal Hunting.- 3. Benefits of Communal Hunting.- References.- Scientific Names of Animals and Plants.
919 citations
"Vigilance Behaviour in Grazing Afri..." refers background in this paper
...Such habitat differences may have influenced the evolution of social and anti-predator behaviour in antelope (GEIST, 1974; JARMAN, 1974; ESTES, 1974) and may also affect both predator and prey behaviour on a day to day basis (SCHALLER, 1972; KRUUK, 1972; CURIO, 1976; EDMUNDS, 1974)....
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