|
|
Nevin, J. A., & Shettleworth, S. J. (1966). An analysis of contrast effects in multiple schedules. J Exp Anal Behav, 9(4), 305–315.
|
|
|
|
Clutton-Brock, T. H., Russell, A. F., Sharpe, L. L., Brotherton, P. N., McIlrath, G. M., White, S., et al. (2001). Effects of helpers on juvenile development and survival in meerkats. Science, 293(5539), 2446–2449.
Abstract: Although breeding success is known to increase with group size in several cooperative mammals, the mechanisms underlying these relationships are uncertain. We show that in wild groups of cooperative meerkats, Suricata suricatta, reductions in the ratio of helpers to pups depress the daily weight gain and growth of pups and the daily weight gain of helpers. Increases in the daily weight gain of pups are associated with heavier weights at independence and at 1 year of age, as well as with improved foraging success as juveniles and higher survival rates through the first year of life. These results suggest that the effects of helpers on the fitness of pups extend beyond weaning and that helpers may gain direct as well as indirect benefits by feeding pups.
|
|
|
|
Cancedda, M. (1990). [Social and behavioral organization of horses on the Giara (Sardinia): distribution and aggregation]. Boll Soc Ital Biol Sper, 66(11), 1089–1096.
Abstract: In this paper some considerations on the environment of the 42 Kmq of the volcanic-basaltic Giara tableland are discussed. Conditioning by the environment and its effect on the distribution of a population of 712 horses is illustrated in view of their social and behavioural organization.
|
|
|
|
Keiper, R. R. (1986). Social structure. Vet Clin North Am Equine Pract, 2(3), 465–484.
Abstract: Socially feral horses live in stable social groups characterized by one adult male, a number of adult females, and their offspring up to 2 years of age. Extra males either live by themselves or with other males in bachelor groups. The bands occupy nondefended home ranges that often overlap. Many abnormal behaviors seen in domestic horses occur because some aspect of their normal social behavior cannot be carried out in captivity.
|
|
|
|
Craig, J. V. (1986). Measuring social behavior: social dominance. J. Anim Sci., 62(4), 1120–1129.
Abstract: Social dominance develops more slowly when young animals are kept in intact peer groups where they need not compete for resources. Learned generalizations may cause smaller and weaker animals to accept subordinate status readily when confronted with strangers that would be formidable opponents. Sexual hormones and sensitivity to them can influence the onset of aggression and status attained. After dominance orders are established, they tend to be stable in female groups but are less so in male groups. Psychological influences can affect dominance relationships when strangers meet and social alliances within groups may affect relative status of individuals. Whether status associated with agonistic behavior is correlated with control of space and scarce resources needs to be determined for each species and each kind of resource. When such correlations exists, competitive tests and agonistic behavior associated with gaining access to scarce resources can be useful to the observer in learning about dominance relationships rapidly. Examples are given to illustrate how estimates of social dominance can be readily attained and some strengths and weaknesses of the various methods.
|
|
|
|
Collery, L. (1974). Observations of equine animals under farm and feral conditions. Equine Vet J, 6(4), 170–173.
|
|
|
|
Kiley, M. (1972). The vocalizations of ungulates, their causation and function. Z. Tierpsychol., 31(2), 171–222.
|
|
|
|
Kitchen, D. M., Cheney, D. L., & Seyfarth, R. M. (2005). Male chacma baboons (Papio hamadryas ursinus) discriminate loud call contests between rivals of different relative ranks. Anim. Cogn., 8(1), 1–6.
Abstract: Males in multi-male groups of chacma baboons (Papio hamadryas ursinus) in Botswana compete for positions in a linear dominance hierarchy. Previous research suggests that males treat different categories of rivals differently; competitive displays between males of similar rank are more frequent and intense than those between disparately ranked males. Here we test whether males also respond differently to male-male interactions in which they are not directly involved, using playbacks of the loud 'wahoo' calls exchanged between competing males in aggressive displays. We played paired sequences of vocal contests between two adjacently ranked and two disparately ranked males to ten subjects, half ranking below the signalers in the call sequences and half above. Subjects who ranked above the two signalers showed stronger responses than lower-ranking subjects. Higher-ranking subjects also responded more strongly to sequences involving disparately ranked, as opposed to adjacently ranked opponents, suggesting that they recognized those individuals' relative ranks. Strong responses to sequences between disparately ranked opponents might have occurred either because such contests typically involve resources of high fitness value (defense of meat, estrous females or infants vulnerable to infanticide) or because they indicate a sudden change in one contestant's condition. In contrast, subjects who ranked lower than the signalers responded equally strongly to both types of sequences. These subjects may have been able to distinguish between the two categories of opponents but did not respond differently to them because they had little to lose or gain by a rank reversal between males that already ranked higher than they did.
|
|
|
|
Bergman, T. J., Beehner, J. C., Cheney, D. L., & Seyfarth, R. M. (2003). Hierarchical classification by rank and kinship in baboons. Science, 302(5648), 1234–1236.
Abstract: Humans routinely classify others according to both their individual attributes, such as social status or wealth, and membership in higher order groups, such as families or castes. They also recognize that people's individual attributes may be influenced and regulated by their group affiliations. It is not known whether such rule-governed, hierarchical classifications are specific to humans or might also occur in nonlinguistic species. Here we show that baboons recognize that a dominance hierarchy can be subdivided into family groups. In playback experiments, baboons respond more strongly to call sequences mimicking dominance rank reversals between families than within families, indicating that they classify others simultaneously according to both individual rank and kinship. The selective pressures imposed by complex societies may therefore have favored cognitive skills that constitute an evolutionary precursor to some components of human cognition.
|
|
|
|
Fischer, J., Hammerschmidt, K., Cheney, D. L., & Seyfarth, R. M. (2002). Acoustic features of male baboon loud calls: influences of context, age, and individuality. J Acoust Soc Am, 111(3), 1465–1474.
Abstract: The acoustic structure of loud calls (“wahoos”) recorded from free-ranging male baboons (Papio cynocephalus ursinus) in the Moremi Game Reserve, Botswana, was examined for differences between and within contexts, using calls given in response to predators (alarm wahoos), during male contests (contest wahoos), and when a male had become separated from the group (contact wahoos). Calls were recorded from adolescent, subadult, and adult males. In addition, male alarm calls were compared with those recorded from females. Despite their superficial acoustic similarity, the analysis revealed a number of significant differences between alarm, contest, and contact wahoos. Contest wahoos are given at a much higher rate, exhibit lower frequency characteristics, have a longer “hoo” duration, and a relatively louder “hoo” portion than alarm wahoos. Contact wahoos are acoustically similar to contest wahoos, but are given at a much lower rate. Both alarm and contest wahoos also exhibit significant differences among individuals. Some of the acoustic features that vary in relation to age and sex presumably reflect differences in body size, whereas others are possibly related to male stamina and endurance. The finding that calls serving markedly different functions constitute variants of the same general call type suggests that the vocal production in nonhuman primates is evolutionarily constrained.
|
|
