Captive and wild orangutan (Pongo sp.) survivorship: a comparison and the influence of management.

For managers of captive populations it is important to know whether their management provides a species with the physical and social environment that maximizes its survivorship. To determine this, survivorship comparisons with wild populations and long-term evaluations of captive populations are important. Here we provide both for orangutans. We show that survivorship has increased during the past 60 years for captive orangutan populations in zoos. In addition, we show that survivorship of captive orangutans in the past used to be lower than for wild orangutans, but that for recently born (1986-2005) orangutans survivorship is not significantly different from the wild. This indicates that captive management in the past was suboptimal for orangutan survivorship, but that modern management of captive orangutans has increased their survivorship. We discuss the possible factors of modern management that could have influenced this.

Spontaneous use of magnitude discrimination and ordination by the orangutan (Pongo pygmaeus).

The ability to discriminate quantity is descriptive of general cognitive ability. In this study, the authors presented 2 orangutans (Pongo pygmaeus) with a quantity judgment task. Each trial consisted of 2 choices, ranging from 1 to 6 food items in each. The orangutan chose 1 of the quantities, which was removed, and the remaining array was given as a reward. In contrast to chimpanzees previously tested on the same task (S. T. Boysen & G. G. Berntson, 1995; S. T. Boysen, G. G. Berntson, M. B. Hannan, & J. T. Cacioppo, 1996; S. T. Boysen, K. L. Mukobi, & G. G. Berntson, 1999), the orangutans optimized their performance. Orangutans, therefore, attend to differences in magnitude and can spontaneously use ordinality. Results also suggest a cognitive difference between chimpanzees and orangutans.