From mid December 2005 onwards a grid of over 4300 monitoring stations consisting of rat ‘goodies’ was established over the entire island. This included items such as chocolate, soap and candles as well as chew sticks. Chew sticks are 150mm x 10mm flat ice cream sticks saturated in used cooking oil.
bins of monitoring materials
The grid was checked on a regular basis to look for tooth marks from any remaining rats. In order to make the items more attractive to rats some were coated in chocolate. This proved successful, as long as the chocolate did not melt. To counteract this problem candles were melted down (and the wicks removed), then the moten wax was mixed with cocoa to produce a chocolate flavoured wax block.
The wax blocks were then placed on monitoring stations and in each bait station. They were wired in to prevent crows or ravens removing them.
Only a few sites were found with nibbled candles. In these areas the team started an even more intensive trapping or poisoning campaign using bait coated in chocolate or in bait containing second generation poisons.
By early March 2006 it was apparent that most, if not all, of the rats had been eradicated.
A monitoring grid was established round the island. It was composed of candles, chew sticks and wax blocks impregnated with cocoa. Some sites were in bait stations and others between bait stations. This was checked monthly throughout the summer to detect signs of any surviving rats. No signs were found.
In late September the 2006 the WMIL team returned to Canna, to conduct more detailed monitoring work. This involved setting out a monitoring grid across the island. Regular monitoring, showed no signs of surviving rats, but lots of signs that woodmice had survived (see progress report 43). During December 2006 the monitoring and bait station grid was removed and a permanent monitoring line was established along the coastline of the island. Contingency and quarantine measures were also established to reduce the likliehood of accidental re-introduction of rats to Canna.
Further monitoring work, using the permanent monitoring line, will continue till May 2008 to confirm that all rats have been successfully eradicated.
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