Data included
In the process of selection of species for discussion in this section, only imports from wild, ranched and ‘unknown’ sources, as well as trade reported without a source specified, were considered.
Scientific specimens, which often refer to blood, tissue etc., and other terms that could not easily be related to numbers of individuals (e.g. feathers, hair), were not used as part of the selection process. However, some discussion of the volume of trade in these terms is included if a species was selected for further review based on other terms imported.
In addition to the conversion factors applied to all trade data, the following conversion factors were applied to the data used to select highly traded species so that certain terms could be more easily equated to numbers of individuals.
Conversion factors applied to data used to select highly traded species.
| [l]Converted from: | [l]Converted to: |
|---|---|
| [l]Elephant tusks | [l]No. individuals [1.88 tusks = one elephant (Parker and Martin, 1982 )] |
| [l]Hippopotamus teeth | [l]No. individuals [12 teeth = one hippopotamus] |
Parker, I.S.C. and Martin, E.B. (1982). How many elephants are killed for the ivory trade? Oryx 16 (3): 235-239.
Selection criteria
High volume
Species qualified for selection on the basis of ‘high volume’ trade if imports during 2011 exceeded pre-determined thresholds based on taxa-wide assumptions of general reproductive biology.
High volume (Globally threatened)
The ‘high volume’ trade thresholds were adjusted for all species categorised as Critically Endangered (‘CR’), Endangered (‘EN’), Vulnerable (‘VU’) or Near Threatened (‘NT’) in the 2013 IUCN Red List of threatened species.
Sharp increase
Species qualified for selection on the basis of a sharp increase in trade if the volume of importer-reported imports during 2011 was more than three times the average trade volume of the preceding five-year period (2006-2010).
Species that, despite a sharp increase in trade, were still only traded in very low volumes (i.e. less than 5% of the high volume thresholds not taking into account threat status), were not selected on the basis of this criterion. Newly-listed species meeting this criterion artificially due to the absence of trade records in previous years were also excluded.
Overall increase or decrease
General trends in trade for each species over the ten-year period 2002-2011 were identified by calculating the slope of a best-fit linear function to the trade data. For the purpose of comparison between species, the value of the slope was divided by the mean level of trade (for the ten-year period in question) for each species. Values greater than +0.15 and lower than –0.15 were considered large slopes. The goodness of fit of the trend-line was also taken into consideration; only species with R2 values greater than 0.75 were retained in the final selection.
Species that, despite an overall increase in trade, were only traded in very low volumes (i.e. less than 5% of the high volume thresholds not taking into account threat status), were not selected on the basis of this criterion. Similarly, species selected on the basis of an overall decrease in trade for which there was no trade in 2011 were excluded. In addition, where it is clear that a species qualified artificially on the basis of an overall decrease due to a taxonomic change (e.g. a species split into two or more separate species), these species were also excluded after closer scrutiny.
High variability
Variability was quantified using the coefficient of variation (the standard deviation divided by the mean) of the data over the ten-year period 2002-2011. Taxa were selected on the basis of this criterion if levels of trade showed a coefficient of variation higher than +2.
Only species with non-zero data points in six or more years 2002-2011 were considered for selection. In the case of species added to the CITES Appendices within the period of analysis, only the years since its listing were analysed where a minimum of five years of trade data were available. Species that were traded in very low volumes (less than 5% of the high volume thresholds not taking into account threat status, or totalling less than 100 units over the ten-year period) were also excluded.