Monday, April 28, 2008

Orangutans at waterside, laryngeal air sacs

Update 03/2010: Orangutan orphans in water
Face always kept above water surface with throat air sac inflated while nose breathing.

Orangutan protects human from crocodile:

You can protect orangutans from extinction:


"Swimming" orangutan, note the throat-neck, likely the bare skin is slightly swollen due to laryngeal air sacs inflated, used when vertical floating or surface sculling with head above water.

Orangutan attempts to hunt fish with spear (likely bamboo, note the nodes [click to enlarge photo]). See here for article on fishing macaque monkeys fishing monkeys

Naturalists were shocked to see the apes go across a river to gain access to some of their favourite fruits at a conservation refuge on Kaja island in Borneo.

Orangutans at Runga river pallas island orphan orangutan sanctuary seen entering water for sweet corn cobs, splashing. No crocs in that area. Probably not swimming. link\

The more stories and "almost swimming' photos, the more doubt arises.
Wading? Yes. Vertical floating? Possible, but probably only if learned in
shallow wetland first. Swimming horizontally? No, no clear evidence of that. Can't blame the folks there for making a fuss about it though, the forest is being destroyed so quickly for oil palm plantations and lumber.

The bottom photo is of two siamang gibbons (lesser apes) which frequently call loudly with inflated air sacs. I hypothesize that ancient hominoids lived in tidal rainforests (estuarboreal), and enlarged throat air sacs were selected (like in frogs) for better vertical flotation and vocalization. Human ancestors remained at the tidal shores but moved from these dense mangroves (per MV) to open shores diving/backfloating at lagoon reefs for shellfish etc. while the ape ancestors followed rivers inland to more arboreal and less aquatic habitat. Humans today do not normally have laryngeal air sacs, however trumpet blowers and glass blowers sometimes develop laryngocoels which are pathological laryngeal air sacs.

The morphology of all extant apes (except the small gibbons) and the skeletal fossils of Lucy & Selam (Australopithecus afarensis) possessing hyoid bones indicate enlarged laryngeal air sacs, while those of Homo neandertalensis and ancient Homo sapiens do not.

Background: Laryngocoele/laryngocele/laryngeal air sac

A laryngocele is usually a cystic dilatation of the laryngeal saccule. The etiology behind its occurrence is still unclear, but congenital and acquired factors have been implicated in its development [1,2]. Laryngoceles appear to be an atavistic remnant from the higher apes (DD: correction, higher apes are not our ancestors, hominoids are ancestral to both Homo and extant apes), particularly those who use their arms with the thoracic cage fixed whilst swinging through the trees (DD: addendum, vertical climbing/floating/wading with arms holding vegetation). ... the laryngocele could have been caused by prolonged and repeated valsalva... the increased air pressure in the larynx may make an already existing laryngocele manifest [1].

Congenitally, the laryngeal saccule is a remnant corresponding to the lateral laryngeal air sacs of the higher anthropoid apes, which may on occasion, manifest suddenly in response to pressure caused by coughing, straining at stool, or trumpet playing (i.e. valsalva maneuvers [used in diving to equalize middle ear pressure]). An acquired laryngocele may develop when the laryngeal ventricle becomes functionally obstructed as a result of an increase in intraglottic pressure, e.g. excessive coughing, playing a wind instrument or obstruction of appendicular ostium [1,2].

Three types of laryngoceles are described. An internal laryngocele is confined to the interior of the larynx and extends posterosuperiorly into the false vocal cord and the aryepiglottic fold; this type appears on laryngoscopy as a smooth swelling of the supraglottis. An external laryngocele extends superiorly to appear laterally in the neck through the opening in the thyrohyoid membrane for the superior laryngeal nerve and vessels; these clinically present as a swelling in the neck at the level of the hyoid bone anterior to the sternocleidomastoid muscle. The simultaneous existence of both features is termed a combined laryngocele [1-4].

The simple laryngocele is an uncomplicated air-filled dilatation of the appendix of the laryngeal ventricle.

Laryngeal air sac in whales, function: Full size right whales forage at the water surface, swim slower than human sport swimmers, and are the fattest whales (float at the surface when dead, which is why whalers called them "right whales"). Pygmy right whales are far less fatty due to their small size and metabolism, so their laryngeal air sac adds buoyancy when foraging on krill copepods near the surface. Apes in shallow water generally seek surface Aquatic Herbaceous Vegetation (AHV) (see the gorilla videos) and only seek bottom foods (water bugs under rocks/leaves) while wading in ankle-deep water. Human ancestors at seashores were tide-affected, and foraged for food from the shallows to perhaps 30+m deep. Because they were enveloped in a thin layer of buoyant thermoinsulative skin fat, denser bones were selected for, bringing the body to neutral buoyancy in seawater (similar to sea otters and walruses).

update: bowhead whales also surface feed and have lar. air sacs, AFAICT no other whales have lar. air sacs and do not typically feed at the surface.

So, bowhead whales, pygmy right whales and apes forage near the water surface and possess laryngeal air sacs; while (ancestral) humans, sea otters, blue whales forage near the sea bottom and lack laryngeal air sacs.

Air sac size quite small (though this is a small whale), compare to 1 liter air sac in orangs or 20-50 liter pharyngeal air sac in walrus. Why did Homo lose the laryngeal air sac? Switch to humming type speech and backfloating and addition of subcutaneous fat layer and stop climbing?

(Stranded) Pygmy right whale dissection, showing lungs and laryngeal air sac at left.

Gorilla foraging in wetland with partly inflated laryngeal air sac:

Note gorilla posture, red scalp, air sac, water just below shoulders.

upright posture - moroto/proconsul aquarboreal climbing/slow brachiating/wading/floating/walking/hanging

red scalp - post-hylobatid hominoid canopy woven nesting mimicry of raptor, grabbing hook-like hand, cooing infant (became hooting in large arboreals), human preemies have lanugo from eyebrows to scalp, which when pulled forward in surprise (eyebrow flash/frown) (or sun avoidance without protruding brows) becomes danger sign to raptor from above, evolutionarily later lost when brain-skull-protruding jaws enlarged.

air sac - visible in photo to the right of the sunlit hair, to left of throat, it is convex ( rather than concave )
due to partly inflated air sac. Human throat would show concave except at adams apple.

water - high enough to give flotation (of face) an advantage


Blindsquirrel said...

The pole appears to be man made. It is far too straight to be something the orang found in the woods.

"the Dude" said...

I know that very straight bamboo and hardwood tree branches in Borneo have been made into blowpipes and spears for thousands of years by hunting and gathering tribes there. The spear seems to be slightly angled at the butt end. I agree it is unusually straight, I don't know the details on the photos, human influence on the orang behavior is very likely. What surprised me most was that the orang ate the fish. DD

redapes said...

The orangutan pictured is just one of hundreds living at the Nyaru Menteng Orangutan Rehabilitation Center, which is operated by the Borneo Orangutan Survival Foundation in Borneo (Indonesia).

Kaja is a small island in the middle of the Rongan River where several dozen orangutans are living until they can be released back into a safe section of the rainforest. The problem is that due to the unchecked spreading of palm oil plantations, the forest is being cut down and orangutans are being slaughtered. This orangutan, like the 650 others at Nyaru Menteng, is an orphan. He watched as his mother was murdered and his forest home was destroyed.

You can see him and the others on the series "Orangutan Island' on Animal Planet.

Because of deforestation by the palm oil industry, orangutans are predicted to be extinct in the wild in less than 10 years. To learn more about orangutans and how to help them, please visit the Orangutan Outreach website at

Thanks, Rich

Richard Zimmerman
Director, Orangutan Outreach
Reach out and save the orangutans!

"the Dude" said...

Richard, thanks, terima kasih, dank u, danke.

The clear cutting for tropical timber and subsequent burning and planting of oil palms for short term gain is economically and sociopolitically beneficial to some of the human population, but devastating to the rich and often unique biodiversity of Borneo.

There are simple answers, but there are no easy answers.