In full swing: assessment of trade in orang-utans and ... - WWF UK

Table 11.
Number of gibbons and orang-utans appearing in trade in 2003 on Java/Bali and potential impact to the wild
population.
Observed or estimated number *
Number lost from wild
population*** per year
Percentage lost to wild
population per year
Bird Rescue Zoos** Scenario 1 Scenario 2 Scenario 1 Scenario 2
markets centres
H. moloch 0 15 56 116 291 2.72 6.86
H. agilis 84 19 36 323 1142 0.16 0.57
H. albibarbis 24 9 23 119 395 0.12 0.39
H. lar 0 0 0 0 0 0 0
H. muelleri 12 1 19 53 170 0.02 0.06
H. klossi 0 1 1 1 2 0 0
S. syndactylus 108 43 78 485 1683 0.13 0.47
P. pygmaeus 60 29 107 321 1058 0.8 2.65
P. abelii 0 1 12 10 24 0.13 0.33
*For bird markets, as a measure the estimated number of gibbons offered for sale on an annual basis was calculated based on the assumption that 31 markets were
included that were each surveyed over a one-month period. This multiplied by 12 gives the annual total.
**This includes gibbons and orang-utans in private hands
*** Wild population is based on Table 2 of this report
For other species, most notably the Javan Gibbon and the Bornean Orang-utan, the total number of individuals traded
on Java and Bali are large enough to have a significant impact on their populations. In both scenarios, the estimated
number of Javan Gibbons traded on Java and Bali in 2003 exceeds several per cent of the remaining wild population.
For the Bornean Orang-utan, at least in the less conservative scenario, also several per cent of the wild population are
involved. Having reached this conclusion, it may be worthwhile to explore the underlying assumptions of the model to
a greater extent to see whether or not the observed pattern for these two species is indeed real or is merely an artefact of
the methodology employed. There are several assumptions in the model that may overestimate the mortality rates as
presented in Table 11, including:
1. The source populations (bird markets, zoological gardens and rescue centres) are not independent.
Individuals observed at bird markets may later be present in zoos or the rescue centres, and therefore the
numbers cannot be simply added as to derive the total number of individuals traded. This may be a valid
argument for the bird markets, but not for the rescue centres and zoos, as no gibbon or orang-utan present at the
rescue centres was derived from zoos, and no gibbons or orang-utans that at one time were present in the
rescue centres have been placed in a zoo. Assuming that all gibbons and orang-utans observed at bird markets
at one time or another do end up in either a zoo or in one of the rescue centres, and thus discarding all data from
bird markets, will have no effect on the Javan Gibbon but will lower the mortality rates of Bornean Orang-utans
in the least conservative scenario to 1.15%. Note that there was a high consistency in species composition and
numbers between the 2003 survey data, and the average for the period 1994-2003, and restricting the analysis
to 2003 data only does not lead to significant differences in the outcome of the model.
2. Turnover is considerably higher than assumed in the model. Many of the gibbons and orang-utans that have
been observed at markets, in zoos, and when arriving at the rescue centres are still very young, and are
therefore likely to have been recently removed from the wild. Hence, the population of gibbons and orang-
IN FULL SWING:ASSESSMENT OF TRADE IN ORANGUTANS AND GIBBONS ON JAVA AND BALI,INDONESIA 34