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.
Citations
More filters
TL;DR: In this paper, the authors use the risk allocation hypothesis as a guide to examine how different risk factors influence vigilance quantity and quality in Cape ground squirrels, Xerus inauris.
50 citations
Cites background from "Vigilance Behaviour in Grazing Afri..."
...There is wide acceptance that feeding rates compromise time allocated to vigilance (Pulliam 1973; Underwood 1982; Arenz & Leger 2000; Fritz et al. 2002) and that individuals must achieve an optimal balance between these divergent activities (Lima & Dill 1990)....
[...]
TL;DR: Changes in ranging behavior and other activities of vervet monkeys (Cercopithecus aethiops) after a wildfire eliminated grass cover in a large area near the study group's home range are described.
Abstract: Here we describe changes in ranging behavior and other activities of vervet monkeys (Cercopithecus aethiops) after a wildfire eliminated grass cover in a large area near the study group's home range. Soon after the fire, the vervets ranged farther away from tall trees that provide refuge from mammalian predators, and moved into the burned area where they had never been observed to go before the fire occurred. Visibility at vervet eye-level was 10 times farther in the burned area than in unburned areas. They traveled faster, and adult females spent more time feeding and less time scanning bipedally in the burned area than in the unburned area. The burned area's greater visibility may have lowered the animals' perceived risk of predation there, and may have provided them with an unusual opportunity to eat acacia ants. Am. J. Primatol. 71:252–260, 2009. © 2008 Wiley-Liss, Inc.
50 citations
Cites background or result from "Vigilance Behaviour in Grazing Afri..."
...Our findings for adult female vervets are consistent with other studies that have documented a decrease in vigilance with decreasing degree of obstructive cover [e.g. Lagory, 1986; Martella et al., 1995; Metcalfe, 1984; Underwood, 1982]....
[...]
...Prey animals often appear to prefer areas with less ground cover or shorter plants [Carey, 1985; Cowlishaw, 1997; Deutsch & Weeks, 1992; Hill & Weingrill, 2007; Rasmussen, 1983; Underwood, 1982] because a reduction in ground cover increases visibility for them, presumably enabling them to detect predators more easily [Deutsch & Weeks, 1992; Götmark et al....
[...]
...…prefer areas with less ground cover or shorter plants [Carey, 1985; Cowlishaw, 1997; Deutsch & Weeks, 1992; Hill & Weingrill, 2007; Rasmussen, 1983; Underwood, 1982] because a reduction in ground cover increases visibility for them, presumably enabling them to detect predators more easily [Deutsch…...
[...]
TL;DR: The results suggest that only some prey individuals may gain anti-predator benefits by reducing their time spent scanning when in larger groups, and propose that some females exhibit higher levels of social vigilance than others, and that this social vigilance increases with group size, cancelling out any group-size effect on anti- predator vigilance for those females.
Abstract: The mean vigilance of animals in a group often decreases as their group size increases, yet nothing is known about whether there is individual variability in this relationship in species that change group sizes frequently, such as those that exhibit fission-fusion social systems. We investigated variability in the relationship between group size and vigilance in the eastern grey kangaroo (Macropus giganteus) by testing whether all individuals showed decreased vigilance with increased group size, as has been commonly assumed. We carried out both behavioural observations of entire groups of kangaroos and focal observations of individually recognised wild female kangaroos. As in other studies, we found a collective group-size effect on vigilance; however, individuals varied in their vigilance patterns. The majority (57%) of the identified individual kangaroos did not show significant group-size effects for any of the recorded measures of vigilance. The females that did not show a negative group-size effect were, on average, more vigilant than those females that did show a group-size effect, but this difference was not significant. We propose that some females exhibit higher levels of social vigilance than others, and that this social vigilance increases with group size, cancelling out any group-size effect on anti-predator vigilance for those females. Our results therefore suggest that only some prey individuals may gain anti-predator benefits by reducing their time spent scanning when in larger groups. The large amount of variation that we found in the vigilance behaviour of individual kangaroos highlights the importance of collecting and analysing vigilance data at the individual level, which requires individual recognition.
49 citations
Cites background from "Vigilance Behaviour in Grazing Afri..."
...…followed the pattern of diminishing vigilance with increasing group size previously recorded in this species (Jarman 1987; Pays et al. 2007a), other macropodid species (Blumstein et al. 1999) and a wide variety of other mammals (Underwood 1982; Burger and Gochfeld 1992; Illius and FitzGibbon 1994)....
[...]
...1999) and a wide variety of other mammals (Underwood 1982; Burger and Gochfeld 1992; Illius and FitzGibbon 1994)....
[...]
TL;DR: It is found that a foraging preference for early successional species can generate multiple plant communities that persist within a herbivore's territory, and if juveniles are selective when searching for territories during their dispersal phase, then herbivores can also generate persistent and distinct plant communities over larger spatial scales.
Abstract: Plant community structure is often the result of interactions between succession, disturbance, and dispersal. While some disturbances may be highly stochastic (e.g., flooding or landslides), other types of disturbance are closely linked to the current successional state of the community (e.g., fire or herbivory). For example, when herbivores preferentially feed on early successional species they may generate conditions favorable for these species and thus create a positive feedback. Positive feedbacks may create multiple stable equilibria within plant communities. We demonstrate the presence of these positive feedbacks using experiments conducted in a restored California grassland. We found that pocket gophers (Thomomys bottae) preferentially forage in areas dominated by annual species, and gopher foraging activity increases the abundance of annual plants. We use a Markov chain model to identify how the foraging behavior, dispersal behavior, and population dynamics of territorial herbivores can structure a plant community across multiple spatial scales. The model is loosely based on the biology of pocket gophers, though it is general enough to be applicable to other territorial herbivores with foraging preferences. We find that a foraging preference for early successional species can generate multiple plant communities that persist within a herbivore's territory. If juveniles are selective when searching for territories during their dispersal phase, then herbivores can also generate persistent and distinct plant communities over larger spatial scales. In this case, fixed regions of the landscape may become occupied by herbivores for long periods (many herbivore generations) and be composed of a range of successional plant species, whereas the remaining landscape is abandoned by herbivores and becomes dominated by late successional species. This structuring of the landscape occurs even though we assume that the entire landscape is intrinsically identical.
48 citations
Cites background from "Vigilance Behaviour in Grazing Afri..."
...…palatable through the course of succession (Bakker et al. 1983, Bazely and Jefferies 1986, Huntly and Inouye 1988) or so dense that it inhibits foraging efficiency by obstructing forager movement (van De Koppel et al. 1996) or ability to see predators (Underwood 1982, Lagory 1986, Loughry 1993)....
[...]
TL;DR: This is the first study to compare such abilities among several community members with variable natural histories, and it discusses future experiments that would more systematically examine development of these skills in young ungulates.
Abstract: A growing body of evidence suggests that a wide range of animals can recognize and respond appropriately to calls produced by other species. Social learning has been implicated as a possible mechanism by which heterospecific call recognition might develop. To examine whether familiarity and/or shared vulnerability with the calling species might influence the ability of sympatric species to distinguish heterospecific alarm calls, we tested whether four ungulate species (impala: Aepyceros melampus; tsessebe: Damaliscus lunatus; zebra: Equus burchelli; wildebeest: Connochaetes taurinus) could distinguish baboon (Papio hamadryas ursinus) alarm calls from other loud baboon calls produced during intra-specific aggressive interactions (‘contest’ calls). Overall, subjects’ responses were stronger following playback of alarm calls than contest calls. Of the species tested, impala showed the strongest responses and the greatest difference in composite response scores, suggesting they were best able to differentiate call types. Compared with the other ungulate species, impala are the most frequent associates of baboons. Moreover, like baboons, they are susceptible to both lion and leopard attacks, whereas leopards rarely take the larger ungulates. Although it seems possible that high rates of association and/or shared vulnerability may influence impala’s greater ability to distinguish among baboon call types, our results point to a stronger influence of familiarity. Ours is the first study to compare such abilities among several community members with variable natural histories, and we discuss future experiments that would more systematically examine development of these skills in young ungulates.
48 citations
Cites background from "Vigilance Behaviour in Grazing Afri..."
...Perhaps due to their vulnerability to both leopards and lions, impala are highly vigilant compared to other ungulates (Underwood 1982)....
[...]
References
More filters
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)...
[...]
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)....
[...]
...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....
[...]
...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....
[...]
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)....
[...]