Parks target butterfly predators
Christchurch’s monarch butterfly colonies are about to get a lifeline.
Monarch butterfly colonies were all but wiped out in two city parks last winter and rats are thought to be the number one culprit.
In April last year, Abberley Park in St Albans was home to about
700 butterflies, but by late August eight remained. Burnside Park had
400 in autumn last year and by the end of winter four remained.
Christchurch City Council will spend $1500 buying and installing rat and predator-proof steel bands around trees in both parks. A report, discussed at the council’s social, community development and housing committee yesterday, said there is no scientific evidence that black rats are killing the butterflies, but anecdotal evidence and expert opinion suggests rats are the most likely scenario.
The steel bands are considered a cost-effective solution. They would cost about $180 a tree.
Butterfly specialist Vicky Steele, who has been lobbying the council to do more to prevent the destruction of butterflies, is pleased by the council’s plan.
‘‘The butterflies are not just dissolving and their wings falling off, they are being eaten.’’
Butterfly numbers usually reduce in winter, as they succumb to the weather or lack of food, but not to this level. In 2015 the butterfly mortality rate at Abberley and Burnside Parks was 4 per cent.
Councillor Tim Scandrett said putting rings around the trees is a ‘‘no brainer’’, but the council should also try to reduce the number of rats in its parks.
Council parks biodiversity team leader Dr Antony Shadbolt said trapping would be costly as the traps would need daily checks.