Reproductive parameters of female orangutans (Pongo pygmaeus wurmbii) 1971–2011, a 40-year study at Tanjung Puting National Park, Central Kalimantan, Indonesia

Abstract

This study presents reproductive parameter data gathered by direct observation over a 40-year period (1971-2011) of the provisioned free-ranging population of orangutans at Camp Leakey in Tanjung Puting National Park, Central Kalimantan, Indonesia. Age at first reproduction, interbirth interval (IBI), sex ratio at birth, and infant mortality for 19 female orangutans (11 first-generation wild-born ex-captive mothers and 8 second-generation mothers) are included in this analysis. Age at first reproduction among the first-generation mothers was similar to that among wild orangutans, while second-generation mothers had a significantly earlier age at first reproduction. IBIs were similar among first-and second-generation mothers and were significantly shorter than those recorded in studies of wild orangutan populations. There was an expected male-biased sex ratio at birth and a slightly higher than expected rate of infant mortality when compared to wild populations. Infant mortality was primarily seen among second-generation mothers who gave birth before the age of 12, and among first births of some first-generation mothers. These results lend support to the ecological energetics hypothesis, which predicts that increased diet quality leads to a faster rate of reproduction. Abstract This study presents reproductive parameter data gathered by direct observation over a 40-year period of the provisioned free-ranging population of orangutans at Camp Leakey in Tanjung Puting National Park, Central Kalimantan, Indonesia. Age at first reproduction, interbirth interval (IBI), sex ratio at birth, and infant mortality for 19 female orangutans (11 first-generation wild-born ex-captive mothers and 8 second-generation mothers) are included in this analysis. Age at first reproduction among the first-generation mothers was similar to that among wild orangutans, while second-generation mothers had a significantly earlier age at first reproduction. IBIs were similar among first-and second-generation mothers and were significantly shorter than those recorded in studies of wild orangutan populations. There was an expected male-biased sex ratio at birth and a slightly higher than expected rate of infant mortality when compared to wild populations. Infant mortality was primarily seen among second-generation mothers who gave birth before the age of 12, and among first births of some first-generation mothers. These results lend support to the ecological energetics hypothesis, which predicts that increased diet quality leads to a faster rate of reproduction.

Reintroduction of confiscated and displaced mammals risks outbreeding and introgression in natural populations, as evidenced by orang-utans of divergent subspecies

“…Given the size and scale of the reintroduction programme, however, Rani and Siswoyo may simply prove the tip of the iceberg. Galdikas estimates that, of the 90 orang-utans she reintroduced to Camp Leakey, at least 80 were probably alive by the time the programme there ceased, although a number had disappeared into the forest 45 . These include two males and one female that were confiscated from the same owner as Siswoyo, though acquired by him at different times and thus potentially from different sources.…”

“…In the case of all these reintroductions — including those by Galdikas — few records are published or publicly available to specify the exact number of animals released, or when or where those releases occurred. Few attempts have been made to document their outcomes 45 56 .…”

“…In 1971, however – when Galdikas and Brindamour established their pioneering research and reintroduction site, Camp Leakey, in Tanjung Puting National Park – all orang-utans were classified as a single species, P. pygmaeus . Over 14 years, Galdikas and Brindamour rehabilitated and released more than 90 ex-captive or displaced orang-utans into the wild at Camp Leakey, on the southernmost promontory of Central Kalimantan 44 45 . Most were confiscated from illegal captivity in the pet trade.…”

Male orang-utan bimaturism and reproductive success at Camp Leakey in Tanjung Puting National Park, Indonesia

“…2). At least 90 excaptive and displaced orang-utans of near-equal sex ratio were released there from 1971 until 1985 (Yeager 1997;Galdikas and Ashbury 2013), complementing a wild population of around 6000 individuals (Singleton et al 2004). The number of orang-utans living in the study area, and thus comprising the study population, cannot be practically quantified over the long term: Inevitably, the population demographics have fluctuated over the site's 43-year history.…”

Developing and evaluating the impact of an interpretive booklet on local and international visitors’ conservation learning at Sepilok Orangutan Rehabilitation Centre

“…However, to date, limited studies have explored people's knowledge, attitudes and behaviours (i.e., conservation learning) about this critically endangered species. Research about orangutans has been directed to biological aspects such as behaviour (Call & Tomasello, 1994;Cartmill & Byrne, 2007), reproduction (Galdikas & Ashbury, 2013;Maggioncalda, Sapolsky, & Czekala, 1999), and genetics (Caeiro, Waller, Zimmermann et al, 2013).…”