Available online at www.sciencedirect.com ARTICLES Experimental evidence for teaching in wild pied babblers NICHOLA J. RAIHANI * & AMANDA R. RIDLEY † *LARG, Department of Zoology, University of Cambridge yPercy Fitzpatrick Institute of African Ornithology, University of Cape Town (Received 23 March 2007; initial acceptance 25 June 2007; final acceptance 26 July 2007; published online 7 November 2007; MS. number: 9324) Giving calls to alert conspecifics to the presence of food is widespread among mammals and birds. Although the circumstances affecting the function of food-associated calls have been well studied, data on how receivers come to associate these calls with food are lacking. Specifically, the possibility that indi- viduals may be actively taught to associate certain vocalizations with food delivery has not been addressed. In pied babblers, Turdoides bicolor, adults often give purr calls when feeding young and offspring subse- quently associate these calls with food delivery. We investigated how offspring come to associate purr calls with food, specifically addressing the question of whether adults teach nestlings to respond to these calls. Adults use purr calls only in the presence of offspring and purr-calling does not seem to result in immedi- ate, direct benefits to adults. Rather, the function of purr-calling seems to be to promote offspring learning: experimental playbacks show that nestlings learn to respond to purr calls and that purr calls must be re- liably paired with food delivery for learning to occur. By giving purr calls during feeding visits at the nest, adults apparently actively condition nestlings to associate these calls with food. This represents a novel form of teaching among nonhuman animals. Ó 2007 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved. Keywords: communication; food call; pied babbler; playback; recruitment call; teaching; Turdoides bicolor; vocalization Pied babbler, Turdoides bicolor, adults often give a specific purr call (described in Raihani & Ridley 2007) when they feed offspring. Both nestlings and fledglings associate purr calls with food delivery, but respond differently to these calls: nestlings beg, whereas fledglings beg and ap- proach adults who give purr calls (Raihani & Ridley 2007). There are substantial benefits to fledglings when ap- proaching adults that give purr calls because adults use these calls to cause fledglings to move around the territory or away from potentially dangerous situations (Raihani & Ridley 2007). However, how offspring come to associate purr calls with food delivery or why purr calls are also used during the nestling phase when offspring are immo- bile is unclear. We investigated the possibility that adults teach offspring to associate purr calls with food by giving these calls during feeding visits at the nest. Teaching occurs when an individual modifies its behav- iour, at some cost or at least without immediate benefit to itself, to promote learning in a na € ıve individual (Caro & Hauser 1992). The facility to accelerate offspring learning through teaching may be advantageous in species with altricial offspring, if it promotes the acquisition of skills or information of critical fitness value to offspring or if it allows parents to shorten the period that offspring are dependent upon them. For an interaction to be classified as teaching, it must fulfil the following three criteria (Caro & Hauser 1992). (1) The teacher must modify its behaviour only in the presence of a na € ıve pupil. (2) The teacher must pay a cost or at least gain no immediate benefit as a result of the behavioural modification. (3) As a result of the teacher’s behaviour, the pupil must acquire knowledge or learn a skill faster than it would otherwise have done. Caro & Hauser (1992) proposed that teaching in non- human animals was likely to be split into two broad categories. The first category, ‘opportunity teaching’, is Correspondence: N. J. Raihani, LARG, Department of Zoology, Univer- sity of Cambridge, Downing Street, Cambridge CB2 3EJ, U.K. (email: njr29@cam.ac.uk). A. R. Ridley is at the DST/NRF Centre of Excellence, Percy Fitzpatrick Institute, Department of Zoology, University of Cape Town, Rondebosch 7701, Western Cape, South Africa. 3 0003e 3472/08/$30.00/0 Ó 2007 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved. ANIMAL BEHAVIOUR, 2008, 75,3e11 doi:10.1016/j.anbehav.2007.07.024