SOCIAL VIGILANCE BEHAVIOUR of the CHACMA BABOON, PAPIO URSINUS by K
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SOCIAL VIGILANCE BEHAVIOUR OF THE CHACMA BABOON, PAPIO URSINUS by K. R. L. HALL 1) (Dept. of Psychology, Bristol, England) (Rec. 15-XII-1959) 1. INTRODUCTION Accounts of the behaviour of wild baboon groups when raiding a plan- tation, crossing a road, foraging for their food or resting in areas where predators may attack them, frequently refer to "sentry" or "sentinel-posting". FiTZSiMMOrrs (19m), in a mixed naturalistic-fictional account of baboon life, describes baboons posting sentries on either side of a dirt road to give warning of the approach of vehicles while the troop foraged for ants. ELLIOTT (r913), introducing the Papio genus, says: "When engaged in any operation considered dangerous, a sentinel is always posted in some favourable place to give warning of a foe's approach and enable the de- predators to escape" (p. m6). Specifically with reference to the Chacma baboon, ELLIOTT quotes from a correspondent in the Grahamstown area of South Africa who writes that" ... when resting a sentinel or two is always placed on top -of a rock in order to warn the troop of approaching danger" (p. 136). ALLEE (1931) quotes JOHN PHILLIPS as follows: "The sentinel is exceedingly sharp and detects the least noise, scent, or appearance of man or leopard. In East Africa I have seen other species of baboon behaving in the same manner. The sentinels are often the largest, strongest males, that is with the exception of the real leader of the group; they will remain faithfully at their post 'waughing'... despite the proximity of danger. Upon these notes of warning reaching the ear of the leader, he will im- I) I wish to thank my colleagues in Cape Town, in particular Professor MONICA WILSON,Mr P. HUMPHRIS,Mr D. DE KOCK,and Mr I. SKEET,for their invaluable help with the field work on many occasions. I wish also to thank Dr N. TINBERGEN, University of Oxford, for his valuable comments. Contributions towards travelling expenses and equipment were received from the Fourcade Bequest and the Staff Research Fund of the University of Cape Town. The Division Council of the Cape, responsible for the administration of the Cape of Good Hope Nature Reserve, granted us accommodation and camping facilities for which I am greatly indebted. The Serval cat was kindly loaned to us by Dr CROMPTON,Director of the South African Museum. 262 mediately assemble the leaders of the group, marshaling the males at the rear and along the sides, the females and young at the forefront, or within the cordon of males; he himself will alternatively lead or bring up the rear, according to the plan of flight or the degree of danger. When things get too hot for the sentinels, they scamper off a short distance, mount some high position, and give a further warning to the leader" (p. 349). SHORTRIDGE (1934) likewise reports of the baboons in South West Africa that: "Several adult males invariably post themselves as sentinels whilst the remainder forage for food" (p. 7). Sentries thus posted pass the alarm along, warning the whole troop which may be widely scattered for feeding. ROBERTS (I95I) states that "... when foraging, young males are usually stationed to keep a look-out from some high point, and upon giving the alarm bark, the whole troop makes for safe refuge in the hills or moun- tains nearby" (p. 9). BoLWIG (1959), describing baboon troops in the Kruger National Park, says: "Idle males usually squat on the ground or on rocks, tree trunks or other elevated points, preferably behind a bush, a stone, or some other object ... Males squatting in this fashion act as sentinels and warn the troop by their loud barks when danger approaches" (p. 139). ZUCKERMAN (1932) pointed out the inadequacy of the observational sup- port for any special social function of "sentinels" and the confusion borne of the terminology when he said: "The use of the term 'sentinel' is al- together unjustifiable. There is no evidence of any kind that special members of a troop are placed on its outskirts for the specific purpose of 'doing sentry-go', and, so far as can be observed, any baboon of a pack who happens to see an approaching human being will bark. Moreover, all care- ful and experienced observers agree that a man may often stumble close upon a pack of baboons when passing over a ridge on one of their rocky hills. Such accidental encounters could hardly be possible if sentries were posted in the manner suggested in some accounts" (p. 206). ZucKExMnrr's assessment has not been invalidated by any evidence since that date. Misleading terminology has persisted, and no systematic and ob- jective evidence has been reported on what I propose to call 'Social Vigi- lance' in baboon groups. The following is a summary of the statements made: I) When resting, carrying out any operation involving danger, or fora- ging for food, certain animals of a group are "invariably" to be seen pro- minently placed so as to give warning to the group or its 'leader' by barking. 2) Under the same circumstances, certain animals are "usually" thus seen. 3) The animals specifically concerned in such vigilance are adult males, young males, idle males, or the largest and strongest males other than the 'real leader'. .