Conservation
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Introduction | Threats | Solutions | What can You do?

Logging

Orangutans have specific habitat demands and are particularly vulnerable to the ongoing loss, degradation and fragmentation of pristine forests in South-East Asia. It must be realized that some of the timber trees are the major food source of orangutans and even selective logging leads to a reduced orangutan density and affects their behavior. Orangutans rest less frequently and during shorter periods of time, they travel during longer periods and their feeding bouts become shorter, altogether potentially leading to fatigue, lethargy and dete-rioration of health conditions.

The most crucial long-term primary effects of logging on a forests’ plant community are (1) the disruption of the hydrology of the area and (2) the exposure of soil to the vicissitudes (a change of circumstances affecting forest life) of climate, notably higher radiation/heat.
The secondary effects are usually much more devastating:
1. Fires: usually uncontrollable and deliberately set in logged/ encroached forests during the dry season. As an example, during the drought of 97-98 at least 50.000 km2 were lost in Borneo alone. The economic losses associated were between 26 million to 6 billion dollars (Int. Herald Tribune April 20th 1998). All affected forests were within the distribution range of orangutans.
2. Areas unaffected by fires are drastically influenced. All trees in adjacent areas (close to areas burned down) die due to (heat) radiation and accelerated desiccation.
3. Poisonous smog created by fires provokes considerable health hazards all over Southeast Asia. Usual attempts to treat symptoms (training and equipping brigades) have no effect except in more weists of financial and human resources.

During (illegal) logging orangutans usually flee as an effect of the noisy operations (rashing down trees). However resident orangutans (opposite to commuters and wanderers) may often try to stay and they will probably get killed because they remain in the trees during the cut-down.
In addition, this initial disturbance is often intensified by illegal hunting/ deliberate harassment of any ape detected by the logging crew: chased, cornered and isolated in a tree that is subsequently cut down. If the orangutan survives to the crash against the ground, it is usually clubbed and slashed to death, to be butchered and eaten if it is an adult. If it is an adolescent or juvenile it is captured alive for ‘amusement’ or sold as pet.
It should be easy to prevent this kind of serious mismanagement urging the members of logging companies to punish harassment of wild apes and supply enough protein from domestic stock for the workers.
Logging crews and foresters sometimes consider that orangutans’ density increases because of higher incidences of long calls given in response to the noise of crashing trees. What actually happens is that orangutans flee to ranges of their neighbors and in this way the number of orangutans in some patches of undisturbed forest that have survived may suddenly rise to several times the usual density. The confrontation of immigrant dominant males between each other and/or local dominant males is known to cause major injuries that can lead to death. Such displacement can readily cause “shock-wave” of refugee impact on the surrounding populations and on the carrying capacity of invaded habitat. This situation leads to general starvation. Nowadays, nearly all logging operations are carried for timber extraction and/or for the establishment of palm oil plantations.

Moreover logging which leads to the fragmentation of the forest canopy increases the vulnerability of orangutans to predation. It can also influence the susceptibility of animals to diseases (general decline of physical conditions) and may facilitate higher probability of infestations due to a greater incidence of parasites and disease vectors.


Hunting and Poaching

Hunting of orangutans for subsistence and/or religious purposes is still continuous. On Borneo and Sumatra tribal people are known to hunt them and Dayaks (Bornean tribe) have been known to be extremely fond of orangutan meat for a long time (1911). As described by Dammermen (1937), Dayaks usually hunt with blowpipe using poisoned darts (lethal mixture of sap of tree Antiaris toxicaria and the liana Strychnos ignatii). Ironically, the fruits of these lethal species are highly favored by the orangutans. Dayak darts have had an effective exterminating impact on orangutans’ populations because hunting success goes up to 90% when using this technique.