Individuality in the groans of fallow deer (Dama dama) bucks D. Reby 1 , J. Joachim 1 , J. Lauga 2 , S. Lek 3 and S. Aulagnier 1 1 Institut de Recherche sur les Grands Mammife Áres, I.N.R.A., B.P. 27, 31326 Castanet-Tolosan cedex, France; email: reby@toulouse.inra.fr 2 CNRS UMR 5552 LET, Bat 4R3, Universite  Paul Sabatier, 118 route de Narbonne, 31062 Toulouse cedex, France 3 CNRS UMR 5576 CESAC, Bat 4R3, Universite  Paul Sabatier, 118 route de Narbonne, 31062 Toulouse cedex, France (Accepted 30 September 1997) Abstract Vocal signatures and individual recognition are documented in a wide range of avian and mammalian species, but little is known about cervids. However, the existence of individual characteristics in cervid vocalizations is highly probable, as the individual morphology of their vocal organ determines the spectral structure of the uttered signal. Here, we report the presence of individual characteristics in the spectral structure of fallow deer groans recorded during the rutting period. We digitized 147 vocalizations from four adult males and transformed each of them into a power spectrum of 32 values in order to represent the frequency distribution of the sound power. A neural network discrimination with cross validation performed on the resulting variables allowed us correctly to identify 87.9 % of the tested vocalizations. The spectrum characteristics of an individual remained stable over the rutting period, and probably over several consecutive ruts (the vocalizations of one male recorded during a previous rutting period were also correctly classi®ed). We therefore conclude that the groan may constitute a vocal signature. The individually structured groan may provide a valuable basis for individual recognition during the breeding season and therefore may play an important role in the social interactions observed during this period. Key words: Dama dama, vocalization, individual calls INTRODUCTION The potential for individual recognition has been found in the spectral dynamics of the vocalizations of many mammalian families (spider monkeys, Ateles geoffroyi: Chapman & Weary, 1990; timber wolves, Canis lupus: Tooze, Harrington & Fentree, 1990; spotted hyenas, Crocuta crocuta: East & Hofer, 1991a; mouse lemurs, Microcebus murinus: Zimmerman & Lerch, 1993; harbour seals, Phoca vitulina: Hanggi & Schusterman, 1994; sea otters, Enhydra lutris: McShane et al., 1995). Concerning cervids, only two studies deal with individual differences in vocalizations: McComb (1988) found individual differences in roars emitted by red deer (Cervus elaphus) stags during the rutting period. In reindeer (Rangifer tarandus), vocalizations also aid mutual individual recognition between mother and young (Epsmark, 1971, 1975). Fallow deer bucks, like most polygynous cervid males, call loudly during the rutting period. Bucks generally groan repeatedly to females while approaching, herding or chasing them, as well as to mature and young males (Braza, Garcia & Alvarez, 1986). The fallow deer groan is a short, low-pitched and stereotyped vocalization. It sounds guttural and comes from a vibration of the vocal cords that is probably produced during inhalation (Gilbert, 1968, pers. obs.). Here, we analyse the acoustic structure of groans uttered by four fallow deer bucks in order to identify the presence of information concerning individuality within the signal structure. METHODS Study area and animals The study was carried out in a private enclosure located 25 km north-east of Toulouse, France. Ninety percent of this 130 ha enclosure is wooded. The remainder consists of a 1.6 ha clearing in the middle of the enclosure and a few small glades. The fallow deer population originates from 4 animals introduced in 1978 from a neighbouring farm. Two more individuals were imported from Scotland in 1986. The population reached 130 individuals in October 1993, including 39 fawns, 64 mature does (1 year old), 20 young bucks, and 7 mature bucks (3 years old). All J. Zool., Lond. (1998) 245, 79±84 # 1998 The Zoological Society of London Printed in the United Kingdom