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Keeping check of the iguana population on St. Eustatius.
All iguanas large enough and with sufficient loose skin by the nuchal crest (neck area) are 'beaded'. This means that we give them coloured glass UV-resistant bead tags in between two dorsal spines, as described in the beading manual by Binns & Burton (2007). Each bead code represents a unique colour code that allows for visual identification of individual iguanas, even from a distance.
Beads that we use are available in seven different main colours namely: Black (B), Pale blue (P), Yellow (Y), Orange (O), Green (G), Red (R) and White (W), and several lesser used colours. Bead codes are read from the outside in. For example a code with the outer bead as white, middle bead as black and the inner bead (closest to the skin) as blue would be noted as WBP. Beads are given to iguanas sizing from approximately 26cm Snout-vent length onward. Beading is only performed on (sub) adults, as fast growing juveniles would be affected by the beads, which could result in abnormal growth.
PIT tag is the abbreviation for 'Passive Integrated Transponder'. These electronic tags the size of a grain of rice are injected just under the iguanas' skin. These tags are invisible from the outside. The reason we give these to iguanas additionally to beading, is to ensure that we can still identify an individual even if bead tags were lost. Also beading is often not possible with smaller iguanas, yet a PIT tag can be administered from approximately the age of 1 and up. Furthermore if any are trafficked for the pet trade, we would be able to identify them.
By using a PIT tag scanner we can identify the code of each iguana with a PIT tag. The downside of PIT tags is that iguanas have to be caught to be scanned, as scanners only work up to 10 - 20cm from a tag.
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