The role of mother-offspring contact in wild Bornean orangutans (Pongo pygmaeus morio)

抄録

Primates are known for their slow life history, including relatively long inter-birth intervals and long periods of juvenility. Orangutans (Pongo sp.) are weaned later than other great apes and have the longest inter-birth interval. The mother provides nutrition, transportation, and protection against conspecifics or predator. Since an immature has not yet mastered all the necessary skills for independent survival, it is fully dependent on its mother for the skills it is still learning. Amongst orangutans, Bornean orangutans (Pongo pygmeaus) appear to reach independence slightly earlier than Sumatran orangutans (Pongo abelii.). This study aimed to examine the function of mother-offspring contact and how the function and relationship between the offspring and mother changed as the offspring developed their skills towards independence. For Bornean orangutans, data on offspring development mainly comes from studies on P. p. wurmbii, with little data coming from P. p. morio. This preliminary study on P. p. morio individuals surrounded Danau Girang Field Centre (Sabah, Malaysian Borneo) is a first step towards filling the gap. The study was conducted from January 17^th to May 16^th 2014. Nest to nest focal sampling on four Bornean orangutan offspring (P. p. morio) were conducted when possible. Data were collected on time spent in contact with the mother, behaviors performed during contact time, and proximity to mother. In this study, orangutan offspring were directly dependent on body contact with their mother until three years of age, with the main function of transportation. After the age of three, the dependence becomes more indirect, with a greater importance on proximity to the mother rather than direct body contact. This proximity could serve as protection, assistance in crossing gaps and/or learning skills such as complex food-processing.