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Journal ArticleDOI

Vigilance Behaviour in Grazing African Antelopes

01 Jan 1982-Behaviour (Brill)-Vol. 79, Iss: 2, pp 81-107
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.
Citations
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Journal ArticleDOI
01 Jul 2015-Ethology
TL;DR: Why the maintenance of vigilance is here best explained by the ghosts of predators past, and how, at the temporal scale of a few generations, the ecological factors driving vigilance levels might override the absence of significant risk from large predators.
Abstract: Vigilance is a key to the early detection of predators, but may be costly if it impairs foraging efficiency. Hence, we would expect vigilance to be suppressed and/or counter-selected in predator-free environments, although this might depend on the environmental drivers influencing perceived predation risk. We studied vigilance in two populations of Sitka black-tailed deer (Odocoileus hemionus sitkensis) on Haida Gwaii (Canada) which have not been exposed to predators since they colonized the study islands approx. 60 yr ago. In this context, anti-predator behavior should not have any obvious current benefit. Moreover, its maintenance should be particularly costly in our study populations because these deer have depleted their food resources and, thus, anti-predator behaviors should interfere with time spent searching for scarce resources. We used bait stations equipped with camera traps to assess vigilance under standardized feeding conditions. We expected to observe lower vigilance levels than those observed elsewhere in locations with predators. We investigated how vigilance varied in relation to the amount of bait, the level of visibility, and between day and night. During the day, deer spent, on average, 14% of their time in overt vigilance during foraging bouts, a level similar to, although in the lower range of, values reported at sites where predators are present. Levels of vigilance were lower at night, and decreased with increasing visibility, but not during the day. Deer were less vigilant when bait availability was high, but only when visibility was also high. We discuss why the maintenance of vigilance is here best explained by the ghosts of predators past, and how, at the temporal scale of a few generations, the ecological factors driving vigilance levels might override the absence of significant risk from large predators.

16 citations

Journal ArticleDOI
TL;DR: In this article, the authors studied how a fine-scale risk factor (distance from tree logs) affects ungulate browsing intensity and how this is modified over a landscape scale risk gradient (Distance from human settlements to wolf core) in the Bialowieza forest, Poland.
Abstract: Large carnivores can reduce ungulate numbers by predation and via induced risk effects alter ungulate behavior, indirectly affecting lower trophic levels. However, predator-induced risk effects probably act at different spatial scales, which have often been ignored in trophic cascade studies. We studied how a fine-scale risk factor (distance from tree logs) affects ungulate browsing intensity and how this is modified over a landscape-scale risk gradient (distance from human settlements to wolf core) in the Bialowieza forest, Poland. We found that landscape-and fine-scale risk factors strongly interacted in determining the strength and magnitude of carnivore-induced risk effects on lower trophic levels. In low-risk areas, tree logs reduced browsing intensity in small patches (approx. 4–6 m from logs), whereas in high-risk areas browsing intensity was reduced up to at least 16 m from tree logs. Moreover, the magnitude of these effects changed, with the strongest reduction in browsing intensity around tree logs in high-risk areas (up to 37%) and the smallest in low-risk areas (< 20%). Overall, the results of this study indicate that perceived risk factors act at different spatial scales, where impediments (objects blocking view and escape routes) act as a risk factor at a fine scale and carnivore distribution shapes perceived risk at the landscape scale. Moreover, these risk factors strongly interact, thereby determining the functional role of large carnivores in affecting ecosystem processes. These interactive effects should be incorporated in predator-induced trophic cascade studies to understand patterns of tree regeneration in ecosystems where large carnivores and herbivores live together.

16 citations

Journal ArticleDOI
TL;DR: It is concluded that hunting practise of northern and temperate ungulates where females having calf/calves at heel are intentionally or non-intentionally harvested, may have demographic side effects at least in harsh winters.
Abstract: A common by-product of human harvesting is orphaning of calves in autumn. Despite this, there are few studies in northern and temperate ungulates evaluating the fate of orphaned calves and the potential benefits to offspring and costs to mothers of post-weaning maternal care. We manipulated orphaning and forage distribution during winter for two herds of reindeer (Rangifer tarandus): one nonfed and the other supplementally fed to increase level of interference competition. Both herds consisted of females with and without calves at heel and orphaned calves. We measured survival and somatic losses during winter and distances between mother–calves and adult females–orphans within the herds. All females survived the winter, and there was no evidence of post-weaning maternal cost in terms of female’s mass loss. The winter mortality among calves was negligible and did not differ between orphans as compared to nonorphans. However, nonorphaned calves lost less mass and stayed closer to their mothers than orphans to adult females, suggesting that increased mortality might occur in harsher winters. This tended to be more marked in the fed group where interference competition was more likely due to feed being concentrated both in space and time. Reduced mass loss in nonorphans is therefore most likely due to mothers sharing and defending feeding resources and protecting their offspring from harassment by other herd members during their first winter. We conclude that hunting practise of northern and temperate ungulates where females having calf/calves at heel are intentionally or non-intentionally harvested, may have demographic side effects at least in harsh winters.

16 citations


Cites background from "Vigilance Behaviour in Grazing Afri..."

  • ...3) probably spend less time foraging as reported in low ranked peripheral distributed bison (Bos bison) (Berger and Cunningham 1988) and among several African ungulates (Underwood 1982)....

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Journal ArticleDOI

16 citations


Cites background from "Vigilance Behaviour in Grazing Afri..."

  • ...Mesoherbivores in particular, which are most susceptible to predation, should benefit from increased detectability, enabling them to spend more time foraging and less on predator-avoidance behaviour (Riginos, 2015; Sinclair et al., 2003; Underwood, 1982)....

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  • ...…2), despite less browse availability, suggesting instead that anti-predator benefits make grazing lawns highly attractive to mesoherbivores because of their higher susceptibility to predation (Augustine, 2004; Burkepile et al., 2013; Sensenig et al., 2010; Sinclair et al., 2003; Underwood, 1982)....

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References
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Journal ArticleDOI
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

Journal ArticleDOI
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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Journal ArticleDOI
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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Journal ArticleDOI

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)....

    [...]