Chemical signals in giant panda urine (Ailuropoda melanoleuca)

Abstract

9. INTRODUCTION Behavioral and non-behavioral cues regulate many aspects of social interactions related to vertebrate reproduction. Among the non-behavioral cues, visual and chemical (pheromones; Karlson and Liischer, 1959) stimuli release specific behavioral or endocrine reactions in the recipient. Mechanisms of their release into the environment are manifold and secretion with urine represents one principle. The giant panda, an endangered species with a low reproductive rate in captivity (Hu and Wei, 1990) and an uncertain future in the wild, is a solitary mammal with only infi'equent visual and vocal contact with conspecifics (Schaller et al., 1985). However, both inter-and intrasexual overlapp of territories is substantial, affording frequent opportunities for chemical communication. The panda is a mono-estrus, seasonal breeder with a brief single receptive period of 24 -72 hours each spring (Kleiman et al., 1979; Kleiman, 1983; Schaller et al., 1985). Because of their solitary way of life, female individuals have to attract males in time. Therefore, the female panda has an active role in initiating and managing the interactions of the pair prior to mating (Kleiman et al, 1979), and marking behaviour of females occurs predominantly during the mating season (Kleiman, 1979; Schaller et al., 1985). The endocrine events associated with the periovulatory period have been described by measuring urinary steroid hormone metabolites. The excretions of estrogens by the female increased approximately eight days prior to observed matings, was at maximum during the preceptive period, and decreased to basal levels during the period of receptivity (Bonney et al, 1982; Hodges et al., 1984). In captivity, successful reproduction depends on the ability of animal managers to detect estrus for the accurate timing of pairing and artificial insemination. For that purpose the estrogen course as well as behavioural and morphological indices were used for reproductive management. Preceptive behaviour can include initiation and maintenance of proximity and establishment of contact. Scent undoubtedly plays an important role in coordination of mating, e.g. to attract males, to signal estrus, and to act as an aphrodisiac. Both sexes possess a large anogenital gland that secretes volatile components which include a series of short-chain fatty acids (C2-C6; Swaisgood et al., 1999). Urine also appears to function as a chemical signal (Swaisgood et al., 2000) Male pandas show intensive vocalisation and marking behaviour in response to urine from estrus females (Swaisgood et al., 1999). Scent marking of females was present six days before the estrogen peak but not afterwards (McGeehan et al., 2002). Thus we hypothesised that female panda urine might possess estrus-related signals and that urinary volatiles, which might serve as pheromones in panda communication, could probably be used to evaluate ovarian function. Pheromones may represent more informative indicators of behavioural and physiological conditions than measurements of circulating or excreted hormones, which do not have a communication function. Using a combined approach of hormonal analysis and solid-phase microextraction (SPME; Arthur and Pawliszyn, 1990) in combination with GC-MS analyses of urinary volatiles, it should be possible to detect reproductive stage-related substances. The present study aimed to identify estrous related substances and assess their reliability for monitoring ovarian function. 2. MATERIALS AND METHODS