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

In all, data was collected from 97 studies on the presence or absence of gibbons and orang-utans at bird markets (see
Annex I, Table 13). Combined, these yielded data from 35 bird markets in 22 cities, representing 355 visits from the
period 1994-2003. For each of the 97 studies the number of visits to single bird markets was noted as well as, when
available, the number of months the study lasted. For example, a study that made two visits in April and May was
categorized as having a duration of two months, unless the first visit was at the very end of April and the second at the
very beginning of May, in which case it was entered in the data base as having a duration of just one month. A study
that made 16 weekly visits in the period May-August was categorized as having a duration of four months, just as one
that would have four monthly visits to these markets. Several studies or monitoring schemes visited the same markets
more than once per month. The number of visits made per month was related to the length of the study. That is,
especially those studies that monitor markets over a long period of time were more likely to make multiple visits per
month. Although multiple visits quite possibly do increase the chance of observing those individuals that are not
openly displayed, it is also highly likely that during these visits the same individuals were encountered multiple times.
As such these visits could not be considered independent.
The issue of independence of data remains when single markets are visited over several (consecutive) months. However,
for analysis of market data, the number of survey months was considered a more appropriate unit of survey effort than
number of visits. Only if detailed data were available on the turn-over of gibbons and orang-utans at markets, and how
individuals are moved within and between markets, would the issue of independence of data be able to be settled, and
would enable a more informed decision to be made on what the most appropriate unit of survey effort would have been.
Unfortunately these data were not available nor was it able to be collected; therefore the default unit used is survey
months.
All prices were converted to USD at the appropriate exchange rate at the time the data were collected. For this, the
foreign currency exchange website: http://www.oanda.com/convert/classic was used. In addition, the local currency,
Indonesian Rupiah (IDR) is listed next to the converted USD price.
Statistical analysis
Comparatively large data sets were analysed using parametric tests after the data were checked for normality. When data
sets were small or showed a non-normal distribution, in order to increase readability, instead of transforming the data to
normalize them, non-parametric test were used. As far as possible, in the figures, open symbols were used when the
relationship between two variables was significant at the 5% level, and filled symbols when this was not the case.
Mortality rates due to trade
Based on the Results section concerning the species composition and numbers in bird markets and wildlife rescue
centres, the origin of gibbons and orang-utans arriving at wildlife rescue centres, and the species composition and
origin in zoological gardens, an attempt was made to model the total number of gibbons and orang-utans that are
extracted from the wild annually. These figures could then be compared with the estimates of the total wild population
to allow an assessment to be made of the impact of trade on the conservation of gibbons and orang-utans. For each
population present at bird markets, rescue centres and zoos, parameters included in this model were:
1. Estimated (markets) or observed (rescue centres and zoos) number of individuals present.
2. Coverage as a percentage of the total number of bird markets, rescue centres and zoos present on Java and Bali.
For the rescue centres, this was based on the percentage of the regencies from where individuals were received.
IN FULL SWING:ASSESSMENT OF TRADE IN ORANGUTANS AND GIBBONS ON JAVA AND BALI,INDONESIA 15