May 21, 2009 - Earth News.  Two female orangutans have been seen cannibalising the bodies of their recently deceased babies. Such behaviour has never before been recorded in any great ape species.

 

The two incidences occurred just one month apart in the same region of forest in Indonesia.

 

The conservationist who witnessed both incidences suspects they were examples of

aberrant behaviour, triggered by stressful living conditions suffered by both mothers.

 

Humans aside, chimpanzees were the only great apes known to engage in cannabilism, the

eating of members of the same species. The behaviour had also been inferred but not seen

in gorillas, after the remains of infants were found in the faeces of two adults.

 

But until now, no ape has been recorded eating its own offspring.

 

"Cannibalism has been documented in chimpanzees and reported in gorillas. Never before

has any ape species been seen treating its own offspring as a consumable resource," says

David Dellatore of Oxford Brookes University, in Oxford, UK.

 

That was until Dellatore begun tracking orangutans living in Bukit Lawang, an area of forest

within the Gunung Leuser National Park in Sumatra, Indonesia.

 

Dellatore, who now works with the Sumatran Orangutan Society based in Medan, Sumatra,

initially monitored the physical health of once captive orangutans that have been

rehabilitated and released back into the wild.

 

But soon he noticed that tourists in the area were interacting closely with the apes. Despite

a ban on doing so, some tourists would feed or touch the semi-wild apes. So Dellatore

switched his research to monitoring the behavioural health of the orangutans, following

them from dawn till dusk.

 

During this research he twice witnessed female apes he recognised eating the corpses of

their recently deceased babies.

 

"While following Edita, whose infant had just died in the forest, on the eighth day myself

and my assistant Tumino saw her begin to consume the corpse," Dellatore says.

 

"At first we did not believe it, but there was no mistaking it. Edita was engaging in filial, or

mother-infant cannibalism."

 

"Then a month later I was following Ratna by myself, whose infant had also just died, and

observed her also cannibalising her dead infant."

 

Seeing the first instance surprised Dellatore, while he found the second even more

shocking.

 

"Such behaviour had never been seen before in more than four decades of orangutan

research. Surely it's not happening here twice in a one month period?" Dellatore recalls

asking himself.

 

But Dellatore managed to collect further evidence of the second event. "I recovered a fallen

piece of the infant's skeleton that Ratna spat out, as well as rather clear video footage of

the event."

 

Grieving mothers

 

Dellatore is unsure why the orangutans behaved so. "It makes little evolutionary sense for

orangutan females to kill their infants, nor is there any evidence that this happened here,"

he reports in the journal Primates.

 

But he points out that it is not uncommon for orangutans and other nonhuman primate

mothers to carry their deceased infants. "It may be part of a grieving process," he says.

Indeed, Edita, a 23 year old female, carried and protected the body of her one year old

infant for seven days, occasionally inspecting it while vocalising a whimper. Only on the

eighth day did she start to consume it, when it was already heavily decomposed. Twenty

year old Ratna's seven month old infant appeared unwell a few days before death.

 

Dellatore is reluctant to make any definitive claims as to why the behaviour occurred. But

he suspects that the mothers' stressed upbringing may have triggered their later actions.

"Semi-wild orangutans are all exposed to considerable traumas, such as witnessing the

deaths of their own mothers," he says. To feed the pet trade, an orangutan is often

captured from the wild as an infant, with its mother being killed as she would not otherwise

let her baby go. Captive orangutans also suffer long periods of social isolation.

 

"Studies have shown that early social deprivation can have deleterious effects on later levels

of cognitive ability. It is possible that the cannibalism events are an extension of these

effects," he says.

 

Although rare, mothers have been recorded cannibalising their infants in a few species of

monkey. In galagoes, another primate species also known as bushbabies, the behaviour has

been linked to stressful living conditions.

 

The presence of tourists may also be stressing the apes.

 

Dellatore supports proper ecotourism in the area, which can bring in important funds that

can help conserve the great apes. But he says too many tourists visit and interact with the

apes without a sense of environmental or social responsibility.

 

His organisation is running an ecotourism development programme in Bukit Lawang to try

and mitigate these problems.

 

Story written by Matt Walker, Editor, Earth News.

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Note from OURF President, Gary Shapiro: Dave Dellatore's research on orangutan

behavior was funded, in part, through the LP Jenkins Fellowship, one of the education

initiatives administered by the Orang Utan Republik Foundation.