RESUMEN
Suckling of a non-filial calf, or allosuckling, is an extreme case of allomaternal care in mammals. There have been many hypotheses postulated in an attempt to explain this behaviour; however, the supporting evidence differs, together with the conclusions drawn from the investigated variables. Previously, suckling bout rejection was analysed, and the milk theft and reciprocity hypotheses were both determined as the most appropriate explanation of allosuckling in giraffe. In this study, seven hypotheses were tested using different behavioural parameters, namely suckling bout frequency, suckling bout duration, and time spent suckling. It is well-documented that these parameters are associated with various aspects in ungulate biology; for example, suckling rejection typically reflects milk intake and parent-offspring conflict, whereas the suckling bout duration and frequency is associated with social behaviours (affiliation, bonding, social stress). In total, 22 nursing females and 47 suckling calves were observed, in four Czech zoos during a five-year period. The correlation of the observed parameters between the reciprocal female-calf dyads was found to be in line with the reciprocity hypothesis. In addition, non-filial calves tried to steal the milk from non-maternal females, supporting the milk theft hypothesis. Thus, the results support both the reciprocity and milk-theft hypotheses as the most plausible explanation of allosuckling in giraffe, and illustrates the importance of using suckling bout duration and frequency, and the time spent suckling, as behavioural parameters that may aid in explaining the extremity of maternal investment, such as allosuckling.
Asunto(s)
Animales Lactantes , Conducta Alimentaria , Jirafas/fisiología , Lactancia , Leche , Animales , FemeninoRESUMEN
Despite being regularly bred in zoos, giraffes remain a challenge, especially in terms of feeding. Assessment of factors influencing growth and weight changes during ontogeny, as well as analysis of weight fluctuations in adult individuals, may become a critical point in captive diet evaluation. Knowledge about weight is a crucial husbandry tool; however, such data are rarely acquired. Using a unique dataset from regularly weighed Rothschild giraffes (Giraffa camelopardalis rothschildi) from Prague zoo, we determined the growth functions of male and female giraffes and calculated weight gains during giraffe ontogeny. The mean weights of adult males and females were 1307 ± 52 and 835 ± 45 kg, respectively confirming the large overall dimensions of G. c. rothschildi in comparison with other giraffe subspecies. As the giraffe is a polygynous species showing considerable sexual dimorphism, we expected male calves to have larger first weights and faster growth during the most intensive period of maternal care. Growth rates and daily weight gains were higher in males than in females during the whole postnatal period. Males grew faster and longer than females. However, differences in weight between males and females appeared as late as after 1 year of age. The weight of adult males and non-pregnant adult females fluctuated significantly across seasons, being the highest during the autumn and winter months, respectively which may reflect the different effects of sexual activity and feeding ratios in males and females. Zoo Biol. 35:423-431, 2016. © Wiley Periodicals, Inc.
Asunto(s)
Animales de Zoológico , Peso Corporal/fisiología , Jirafas/fisiología , Crianza de Animales Domésticos/normas , Animales , República Checa , Conducta Alimentaria/fisiología , Femenino , Jirafas/crecimiento & desarrollo , Masculino , Estaciones del Año , Factores SexualesRESUMEN
Wild giraffes live in extensive groups in the fission fusion system, maintaining long social distances and loose social bonds. Within these groups, resources are widely distributed, agonistic encounters are scarce and the dominance hierarchy was reported in males only, while never deeply analysed. In captivity, the possibility to maintain inter-individual distances is limited and part of the resources is not evenly distributed. Consequently, we suggest that agonistic encounters should be more frequent, leading to the establishment of the dominance hierarchy. Based on the differences in resource-holding potential, we suggested that the rank of an individual would be affected by age and sex. Based on hypotheses of prior ownership, we tested whether rank was positively affected by the time spent in a herd and whether it was stable in adult females, which were present long-term in the same herd. We originally monitored four herds of Rothschild giraffes (Giraffa camelopardalis rothschildii) in Dvur Králové zoo (n = 8), Liberec zoo (n = 6), and two herds in Prague zoo: Prague 1 (n = 8) and Prague 2 (n = 9). The Prague 1 and Prague 2 herds were then combined and the resulting fifth herd was observed over three consecutive years (2009, 2010, and 2011) (n = 14, 13, and 14, respectively). We revealed a significantly linear hierarchy in Dvur Králové, Prague 2 and in the combined herd in Prague. Rank was significantly affected by age in all herds; older individuals dominated the younger ones. In females, rank was positively affected by the time spent in the herd and adult females in Prague maintained their rank during three consecutive years. This study represents the first analysis of the dominance hierarchy in the captive giraffe, and discusses the behavioural flexibility of the social structure in response to monopolisable resources in a captive environment.