Above Picture:  How hungry?  A House Mouse on Marion Island during winter, photograph by Ivan Dalgleish

This post continues an occasional series that features the several scientific papers that give information on attacks by House Mice on the birds of Marion Island.  For the first post in the series click here. 

John Parkes (Kurahaupo Consulting, Christchurch, New Zealand) published in the 2019 Proceedings of an international Island Invasives Conference held in 2017 in Dundee, Scotland on the timing of aerial baiting to eradicate House Mice on Marion Island, suggesting a bait drop should occur during March to May rather than in mid-winter. 

The conference paper’s abstract follows: 

“Aerial baiting from helicopters with a bait-sowing bucket and GPS to ensure coverage with anticoagulant toxins in cereal-based baits can reliably eradicate rodents on islands. Current best practice for temperate islands is to bait in winter when the rodents are not breeding, rodent numbers are lowest so competition for toxic baits is lowest, natural food is likely to be scarce, and many non-target species are absent from the island. However, short winter day lengths at high latitudes restrict the time helicopters can fly and poor weather in winter may increase risks of failure. This paper notes precedents from cool-temperate islands where baiting was not conducted in winter and then uses the extensive data on mice on Marion Island to explore whether current recommendations for winter baiting based on breeding and natural food availability are important risk factors in determining time of year to bait. Marion Island mice do not breed between early May and late September, mouse densities reach a maximum in May and minimum in November, but the biomass of main natural food (invertebrates) do not fluctuate greatly over the year. This means the per capita food availability is least in autumn and increases through winter to most in spring and summer. The weight of the stomach contents of mice is also highest in winter. Based on this per capita food parameter mice are likely to be most hungry between about March and May suggesting baiting would be more effective in this period (perhaps towards the end of it when breeding stops) than in the more traditional winter season.” 

With thanks to John Parkes, Kurahaupo Consulting, Christchurch, New Zealand. 

Reference:  

Parkes, J.P. 2018.  Timing aerial baiting for rodent eradications on cool temperate islands: mice on Marion Island.  In: Veitch, C.R., Clout, M.N., Martin, A.R., Russell, J.C. & West, C.J. (Eds).  Island Invasives: Scaling up to meet the Challenge.  Gland, Switzerland: IUCN.  pp. 36-39. 

 

John Cooper, Member, Scientific and Technical Advisory Group, Mouse-Free Marion Project, 09 September 2021