Orangutans – probably more interesting than you

ResearchBlogging.orgIn the past few years there has been a recent spate of articles concerning orangutan intelligence. So, as I’m fairly bored, and in need of a break from university work, I’ve decided to write a bit of an essay on some of these finds.

Orangutans… They’re orange, right?

Correct; but Pongo pygmaeus abelii are so much more than just some arboreal orange ape that eats a lot of fruit. In fact, these great apes, the last surviving members of the genus Pongo, are highly resourceful and intelligent creatures, as evident in their ability to make and use tools, perform calculated reciprocity and even whistle a tune.

Making tools to smash termite mounds, innit!

Compared with the latter two behavioural traits mentioned, the ability to use and manufacture tools is something shared with other non-human species, including Chimpanzees (Pan troglodytes) and New Caledonian Crows (Corvus moneduloides) amongst others. Essentially, Orangutans habitually use and make tools to obtain food, with some tools showing surprising innovation, as described by Masayuki Nakamichi (2003):

The special tool (i.e. stick with a sponge) made by the adult female in this study (Josephine) consisted of two parts and each had its own function; i.e. the stick was used to push the sponge into the hole and to extract it again, while the sponge, which could not be used without the stick, was used to soak up more food.

Perhaps more interestingly, the conclusions offer intriguing insights into differences between captive and wild orangutans, with the former being far more gregarious (not necessarily by choice) in contrast to observations in the wild, where orangutans tend to lead a rather solitary existence (cue the anthropomorphic ‘awww’). Nakamichi thinks such captive, group-living orangutans are key in understanding their true cognitive potential, adding:

In particular, by examining the performance of group-living orangutans in novel tasks including tool-using and tool-making, we can evaluate the importance of gregariousness and tolerance for social transmission, as proposed by Van Schaik et al. (1999), and thus gain more information about how much sociality influences the process of building new cognition structures in orangutans.

This last sentence tempts me to offer some of my own, highly speculative thoughts on human evolution, though I imagine anyone reading this will be able to extrapolate such inferences for themselves. Instead, I’ll leave you with a nice photo of the termite muncher in action:

Yum, yum some, um, termites
Yum, yum some, um, termites

Where’s my tokens?

Next on the agenda is their surprising ability for calculated reciprocity (just to be clear: the cultural anthropological meaning of reciprocity should not to be confused with its alternative usage in evolutionary biology). But what is calculated reciprocity? According the criteria set by the authors:

To qualify reciprocal giving as ‘calculated giving with return expectancy’, it must be shown that (i) giving occurs intentionally from one partner to another, (ii) partners know the value of the traded items for both sides and (iii) partners expect given items to be returned.

Basically, it’s an act of reciprocity where one participant benefits the other, with the express purpose of getting a return for these services at a later date, which in our case is being tested for in two orangutans, Bim and Dok. Now, transfers in exchange for services are ripe throughout the animal kingdom, but calculated reciprocity was believed, until Bim and Dok came along, to be a unique behavioural characteristic of humans. It’s easy to understand why this belief has held dominance for such a long time. After all, when performing calculated reciprocity, humans are weighting costs against benefits and keeping tract of transactions over a period of time; choosing to return, or call upon, favours at a later date. It’s all about intentionality (and the subtle intricacies that it comes loaded with).

In their study, Dufour et al provide Bim and Dok with some tokens, which they can use in exchange for food from the experimenters (those bourgeois, elitist tyrants). In a slight twist, however, the tokens belonging to one orangutan correspond to food rights for the other orangutan, and vice versa. For example, Bim is hungry and is in need of food, but all he has are these stupid tokens that no-longer get him food (they were previously trained with three different token-exchange types). So, Bim asks Dok for her tokens instead, by making a gesture-based request, and when he uses them the experimenter provides food. So, Bim is now a happy (perhaps slightly bemused) orangutan, and quickly makes use of his new discovery.

Initially, these transfers were one way (Bim asks, Dok gives), but as time progressed the balance of power shifted somewhat — Dok was now calling in her overdue favours from Bim (see figure 1, below). As you can see from the graph, the number of token transfers taking place begins to even out between Dok and Bim by time they reach series 4; even if Bim was still being a bit of an ass.

Number of partner-value tokens (including banana peel) transferred by individuals (excluding the offspring) in each of the four series (diamonds, Dok; squares, Bim).
Figure1: Number of partner-value tokens (including banana peel) transferred by individuals (excluding the offspring) in each of the four series (diamonds, Dok; squares, Bim). (Dufour et al., 2008)

Uncovering these abilities in orangutans is probably a bit confounding for chimp (and other great ape) researchers, as these species have thus far failed to grasp the concept of calculated reciprocity, even though they possess sufficient cognitive abilities. This victory for orangutan fans leads nicely into the paper’s conclusion, which proudly states:

This is the first experimental demonstration in non-human primates of the occurrence of calculated reciprocity through the repeated exchanges of goods. It is currently unclear whether simply increasing the number of trials or slightly changing the procedure by compelling orang-utans to exchange with their partner to get valuable tokens was the reason for the appearance of a more sophisticated token transfer system. The intentionality behind giving, the computation based on expected returns, in addition to the shared knowledge of the value of the traded items showed that calculated reciprocity underpinned the transfers of goods [my emphasis].

There you have it: orangutans can develop a bilateral, reciprocal trading system. It’ll be interesting to see if future studies, involving multiple agents, will result in a market-like system. Perhaps they might just all kill each other. Humans don’t really give much insight as to which way this will go.

Whistle away…

The ability to voluntarily produce learned sounds is a key component of language, which is why we do not usually associate such abilities with great apes and other primate species. Yet once again, orangutans prove us wrong. Meet Bonnie, a 30 year old, captive orangutan who, after hearing a jolly zoo keeper whistling, decided she’d give it a go — and surprise, surprise she managed it. Quite impressive, especially considering she wasn’t explicitly taught this ability. Though, as Babel’s Dawn also points out, apes can make ad hoc gestures, with some theorists arguing that language grew out of such abilities; just see Kanzi for a similar account of unforced, naturalistic learning. Like Babel’s Dawn, I’m not completely convinced by the paper, mainly because Bonnie learnt to whistle of her own accord, and as a result was not rigorously observed. Simply put: we don’t know how this ability developed. But importantly it did develop, and with this knowledge future researchers can perhaps offer an explanation. Until then, here’s Bonnie whistling away:

…Okay, so it’s not quite the quality of whistling that endears itself to Simon Cowell’s exacting standards. In fairness, there are plenty of people who can’t perform this task, with Bonnie proving human abilities aren’t always a step ahead of our evolutionary relatives. Oh, and one more thing: Orangutans are actually a reddish brown, not orange. Don’t you know anything?


M Nakamichi (2004). Tool-use and tool-making by captive, group-living orangutans (Pongo pygmaeus abelii) at an artificial termite mound Behavioural Processes, 65 (1), 87-93 DOI: 10.1016/j.beproc.2003.07.002

V. Dufour, M. Pelé, M. Neumann, B. Thierry, J. Call (2009). Calculated reciprocity after all: computation behind token transfers in orang-utans Biology Letters, -1 (-1), -1–1 DOI: 10.1098/rsbl.2008.0644

Serge A. Wich, Karyl B. Swartz, Madeleine E. Hardus, Adriano R. Lameira, Erin Stromberg, Robert W. Shumaker (2008). A case of spontaneous acquisition of a human sound by an orangutan Primates DOI: 10.1007/s10329-008-0117-y

4 thoughts on “Orangutans – probably more interesting than you”

  1. I have heard suggestions that the only reason orangs are solitary in the wild is that thousands of years of human encroachment has made their habitats too poor to support the usual ape troops.

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