“I heard a rustling in a tree near, and, looking up, saw a large red-haired animal moving slowly along, hanging from the branches by its arms. It passed on from tree to tree until it was lost in the jungle, which was so swampy that I could not follow it.”
These are the words of the great naturalist Alfred Russell Wallace, describing how he caught sight of his very first orangutan. Around two weeks later, Wallace found his second individual and, as you would expect for a 19th century British explorer, he shot it dead.
During his fifteen-month stay in Borneo, Wallace ‘collected’ a further 28 orangutans and his tales of slaughter and science are vividly described in his famous tome, The Malay Archipelago (immortalised here by Google).
Wallace wasn’t the only explorer to shoot his way through Borneo’s orangutan population. Odoardo Beccari shot or saw at least 26 individuals in just over 5 weeks, while Emil Selenka collected around four hundred specimens over four years. All of these records attest to the fact that orangutans were relatively common in the late 19th century, such that zealous Europeans had no problems in finding them.
The same can’t be said now. Field scientists working in Borneo rarely see a wild orangutan and when they do, they’re usually alone or in very small groups. You can travel down the very rivers where naturalists once described seeing orangutans many times in the same day, and find only nests.
Today, we might raise an eyebrow at the trigger-happy antics of Wallace and his contemporaries but, at the very least, they carefully documented what they did. And those tales, together with museum collections, have allowed Erik Meijaard from The Nature Conservancy in Indonesia to reconstruct the history of the Bornean orangutan since the 19th century.
Meijaard studied records from 59 Bornean expeditions and found that the odds of encountering an orangutan on any given day have fallen by 6 times in the last 150 years. This downward trend stayed the same even after Meijaard accounted for the fact that expeditions have become shorter and involve fewer people.
In Wallace’s time, explorers relied on the skills of local trackers to find orangutans and the focus was very much on these prized animals. Today, scientists often survey orangutan populations by looking for their nests instead. However, when Meijaard only looked at expeditions that specifically set out to count as many orangutans as possible, he still found a sizeable drop between historic rates and modern ones.
Finally, it’s possible that orangutans have learned to avoid people because of the likelihood of getting shot by an intrepid European. Wallace’s accounts certainly suggest a less cautious attitude than one might expect. But Meijaard argues that orangutans, being largely solitary animals, have little opportunity to learn from the death of other group members. Nor would they learn from individuals who escaped 19th century rifles, for very few did – these slow-moving and large apes were easily shot once spotted. So a more elusive temperament might contribute to the rarity of modern orangutans, but Meijaard thinks that it can’t fully explain it.
With all these possibilities considered and potentially ruled out, the most likely explanation for the downward trend is that it’s real: the ape’s population has actually declined. The genes of the surviving individuals support this conclusion. The genetic similarities between orangutans from the Bornean state of Sabah suggest that the population has fallen by around 10 times in the last one or two centuries. The big question is: why?
Surprisingly, it seems that deforestation hasn’t played a big role. It’s true that logging threatens the safety of orangutans today, but the decline in orangutan numbers was well underway some 120 years before logging kicked off. This industry really intensified during the 1960s and 1970s and during that time, orangutans didn’t suddenly become harder to see. Disease is another possibility, but one with little evidence to back it up.
For Meijaard, one explanation remains – hunting. Orangutans give birth to relatively few young and they have large generation gaps. As such, the adult population takes a long time to replenish. Even before Wallace and his chums arrived in Borneo, orangutans had already been severely hunted by nomadic humans, and been driven to extinction in some parts of Indonesia. Thousands of buried teeth in Borneo and Sumatra harken back to a time when these apes were hunted as commonly as wild pigs.
Once Europeans came on the scene, they weren’t just killed for food any more, but for scientific study, trophies, and the pet trade, while locals continued to kill them for traditional medicine, or as agricultural pests. Ironically, the colonial ban on head-hunting in Sabah may have made matters worse. By suddenly making large tracts of the jungle safe to travel in, the end of head-hunting tribes allowed Western hunters to spread to the jungle, shooting as they went.
Meijaard doesn’t think that his study is the final word on orangutan populations. In fact, he openly wishes that he had better data to work on and hopes that other scientists will take up the challenge. But he says that studies like these are important because they conservationists a better understanding of the real challenges facing a threatened species.
To work out how humans have affected a particular species, you need to know how that creature was faring before we came along. But usually, scientists assess the health of a species after a long period of exploitation and they end up using a baseline that has already been shifted. The result is what Meijaard describes as “historic amnesia”.
This is certainly the case for orangutans – it’s often said that this red ape has a low population density, even in parts of the forest that haven’t been disturbed by logging. The common wisdom says that the orangutan depends on fruit that is sparsely distributed, so a given patch of jungle can only hold so many individuals. This new study suggests that this isn’t true.
This has the potential to change not only our approach to orangutan conservation, but our understanding of their behaviour. Modern individuals are operating at much lower densities than their ancestors used to, and we need to bear that in mind when interpreting the way they act. How differently would they behave if 6 times as many orangutans lived in the same patch of forest?
Reference: PLoS ONE http://dx.doi.org/10.1371/journal.pone.0012042
More on orangutans:
- Orangutans are masters of conserving energy
- Orang-utan study suggests that upright walking may have started in the trees
- Scientists tickle apes to reveal evolutionary origins of human laughter
- Orang-utans use leaves to lie about their size
- Photo safari – Orangutans Part 1, 2, 3 and 4
If the citation link isn’t working, read why here
- I Spy With My Little Eye… - November 7th, 2009 [November 7th, 2009]
- A Crack Opens in the Ethiopian Landscape, Preparing the Way for a New Sea | 80beats - November 8th, 2009 [November 8th, 2009]
- The Politics of Addiction | The Intersection - November 8th, 2009 [November 8th, 2009]
- Finally! An iPhone App That Lets You Track Your Bathroom Habits | Discoblog - November 8th, 2009 [November 8th, 2009]
- Don’t Pack Your Bags Yet—New Planet-Finder Hobbled by Electronic Glitch | 80beats - November 8th, 2009 [November 8th, 2009]
- In Controversial Scent Lineups, a Dog’s Nose Picks Out the Perp | 80beats - November 8th, 2009 [November 8th, 2009]
- Are You a Cognitive Miser? | Cosmic Variance - November 8th, 2009 [November 8th, 2009]
- The Secret Lives and Loves of Great White Sharks | 80beats - November 8th, 2009 [November 8th, 2009]
- Britain’s New Protected Minority: Tree-Huggers | Discoblog - November 8th, 2009 [November 8th, 2009]
- Inspired by Maple Seeds, a Robotic Whirligig Takes To The Skies | Discoblog - November 8th, 2009 [November 8th, 2009]
- New Statesman on Accommodationism | The Intersection - November 8th, 2009 [November 8th, 2009]
- Laser-Powered Robot Climbs to Victory in the Space-Elevator Contest | 80beats - November 8th, 2009 [November 8th, 2009]
- Checking Back In With SEAPLEX | The Intersection - November 8th, 2009 [November 8th, 2009]
- Podcast: An Embarrassment of Genomes | The Loom - November 8th, 2009 [November 8th, 2009]
- A Baby Neutron Star, Swaddled in a Carbon Atmosphere | 80beats - November 8th, 2009 [November 8th, 2009]
- Butterfliiiies… iiinnnn… SPPPAAAAACCCCEEEEE! | Bad Astronomy - November 8th, 2009 [November 8th, 2009]
- My Slate Dialogue with Michael Specter Begins | The Intersection - November 8th, 2009 [November 8th, 2009]
- Musical, Fahrvergnügen-Inspired Staircase Makes Commuters Less Lazy | Discoblog - November 8th, 2009 [November 8th, 2009]
- Laser-Etched Fruit Is an Answer in Search of a Problem | Discoblog - November 8th, 2009 [November 8th, 2009]
- Ares and the carnivals | Bad Astronomy - November 8th, 2009 [November 8th, 2009]
- Toddler Gets a Telescoping, Prosthetic Arm Bone That Grows With Him | 80beats - November 8th, 2009 [November 8th, 2009]
- Neutered HIV Virus Delivers Treatment to Fatally Ill Boys | 80beats - November 8th, 2009 [November 8th, 2009]
- Specter’s First Reply: Denialism Kills People | The Intersection - November 8th, 2009 [November 8th, 2009]
- LRO sees a Moonslide | Bad Astronomy - November 8th, 2009 [November 8th, 2009]
- Al Gore’s New Book: A Focus on Solutions | The Intersection - November 8th, 2009 [November 8th, 2009]
- The Universe Has Us in Its Crosshairs | Bad Astronomy - November 8th, 2009 [November 8th, 2009]
- Makers of Universes | Cosmic Variance - November 8th, 2009 [November 8th, 2009]
- Can Your Pet Catch & Spread Swine Flu? Yes, If Your Pet’s a Ferret | 80beats - November 8th, 2009 [November 8th, 2009]
- Droid 2.0 Vs iPhone | The Intersection - November 8th, 2009 [November 8th, 2009]
- Tangled Bank News: An Excerpt and More | The Loom - November 8th, 2009 [November 8th, 2009]
- LHC Shut Down By Wayward Baguette, Dropped by Bird Saboteur | Discoblog - November 8th, 2009 [November 8th, 2009]
- Careidolia | Bad Astronomy - November 8th, 2009 [November 8th, 2009]
- Slate Reply to Specter Up–We Need a National Dialogue on Synthetic Biology | The Intersection - November 8th, 2009 [November 8th, 2009]
- Pray this doesn’t get passed | Bad Astronomy - November 8th, 2009 [November 8th, 2009]
- You Can’t Make This Stuff Up | Cosmic Variance - November 8th, 2009 [November 8th, 2009]
- Mother Tongue, Indeed: Newborn’s Cries Mimic Mama’s Accent | 80beats - November 8th, 2009 [November 8th, 2009]
- Ripped From the Journals: The Biggest Discoveries of the Week | 80beats - November 8th, 2009 [November 8th, 2009]
- Alternative Landscapes | The Loom - November 8th, 2009 [November 8th, 2009]
- Can an iPhone App Decipher Your Baby’s Cries? | Discoblog - November 8th, 2009 [November 8th, 2009]
- Reminder: Carl Sagan Day | Bad Astronomy - November 8th, 2009 [November 8th, 2009]
- Are There Pesticides in Your Soup? Dunk a Pollution Dipstick to Find Out. | 80beats - November 8th, 2009 [November 8th, 2009]
- Log in and Join the Conference - November 8th, 2009 [November 8th, 2009]
- Conference Ends - November 8th, 2009 [November 8th, 2009]
- Conference Archive Opens - November 8th, 2009 [November 8th, 2009]
- Galaxy Zoo - November 8th, 2009 [November 8th, 2009]
- .Astronomy 2009 Dates - November 8th, 2009 [November 8th, 2009]
- .Astronomy 2009: Programme and venue details - November 8th, 2009 [November 8th, 2009]
- .Astronomy Gets Some IYA Love - November 8th, 2009 [November 8th, 2009]
- 2009 Posters and Imagery - November 8th, 2009 [November 8th, 2009]
- 2009 Sponsors - November 8th, 2009 [November 8th, 2009]
- When in Holland… - November 8th, 2009 [November 8th, 2009]
- The WHAT Cloud? - November 8th, 2009 [November 8th, 2009]
- The Jewel Box - November 8th, 2009 [November 8th, 2009]
- Happy Halloween! - November 8th, 2009 [November 8th, 2009]
- Ares 1-X Launch - November 8th, 2009 [November 8th, 2009]
- Confessions of an Alien Hunter - November 8th, 2009 [November 8th, 2009]
- LRO Spies Apollo 17 Site - November 8th, 2009 [November 8th, 2009]
- Mercury in Color - November 8th, 2009 [November 8th, 2009]
- Hubble and M83 - November 8th, 2009 [November 8th, 2009]
- Cassini Flyby of Enceladus - November 8th, 2009 [November 8th, 2009]
- Preserving A Moth [Science Tattoo] | The Loom - December 12th, 2009 [December 12th, 2009]
- Another Russian rocket spiral lights up the sky | Bad Astronomy - December 12th, 2009 [December 12th, 2009]
- A (Very Gentle) Riddle to Complete Your Saturday - December 12th, 2009 [December 12th, 2009]
- Darwin Gets Swine Flu: The YouTube Edition | The Loom - December 12th, 2009 [December 12th, 2009]
- Happy Slothy Holidays | The Loom - December 12th, 2009 [December 12th, 2009]
- Jetting to Copenhagen | The Intersection - December 12th, 2009 [December 12th, 2009]
- Michael Gerson Attempts Thoughtfulness on “ClimateGate,” Then Gives it Up | The Intersection - December 13th, 2009 [December 13th, 2009]
- Incredible VISTA of the cosmos | Bad Astronomy - December 13th, 2009 [December 13th, 2009]
- Bundle up Sunday Night to Watch the Geminid Meteor Shower | 80beats - December 13th, 2009 [December 13th, 2009]
- “ClimateGate” a PR Disaster That Will Be “Taught in University Communications Courses” | The Intersection - December 13th, 2009 [December 13th, 2009]
- Is Google the Guardian Angel of Rainforests? | 80beats - December 13th, 2009 [December 13th, 2009]
- La ciencia es importante. Una vez mas. | Bad Astronomy - December 13th, 2009 [December 13th, 2009]
- Sensenbrenner Pulls an Inhofe, Asserts Global Warming is an “International Conspiracy” | The Intersection - December 13th, 2009 [December 13th, 2009]
- Let Kids Eat Dirt: Over-Cleanliness Linked to Heart Disease | 80beats - December 13th, 2009 [December 13th, 2009]
- What Are The Best Science Papers Of The Past Decade? | The Intersection - December 13th, 2009 [December 13th, 2009]
- Finally! Math Shows How to Cut Evenly Sized Pizza Slices | Discoblog - December 13th, 2009 [December 13th, 2009]
- Half-baked math | Bad Astronomy - December 13th, 2009 [December 13th, 2009]
- Can “Biological Passports” Save Sports From Doping? | 80beats - December 13th, 2009 [December 13th, 2009]
- Aiiiieeee! Slow down! | Bad Astronomy - December 13th, 2009 [December 13th, 2009]
- Weekly News Roundup: Bad Headlines, Martian moons, and Rotating Houses | Discoblog - December 13th, 2009 [December 13th, 2009]