What about the mice on Auckland Island?

Written by James Russell

View over Terror and Erebus Cove from Deas Head. Photo by J. Russell

View over Terror and Erebus Cove from Deas Head. Photo by J. Russell

Antipodes Island was not the only New Zealand subantarctic island to be colonised by mice. Mice have been reported on Campbell Island but would have been out competed by Norway rats and hence never made it beyond the buildings. Mice also reached Auckland Island and nearby smaller Enderby Island. Whereas the date mice ship-wrecked on Antipodes Island is known to be around the early 20th century, on Auckland Island mice arrived much earlier. They were first recorded in 1840 by a United States expedition, but likely had already been present for some time, especially since cats were also recorded at that time and had probably been introduced in a failed attempt to control mice. This puts the arrival of mice on Auckland Island sometime after 1820 (Taylor 1968), not long after their Western discovery by Lord Bristow in 1806. This is in fact one of the earliest records for mice in New Zealand, which were otherwise first recorded in 1824 on Ruapuke Island in Foveaux Strait following the wreck of the Elizabeth-Henrietta. Even then mice did not make it far, not being recorded in the North Island until the 1830s, and the South Island until the 1850s (Ruscoe and Murphy 2005). Although the mice on Antipodes Island are genetically unique in New Zealand, the mice of the Auckland Islands match those in the upper North Island, including the Bay of Islands where mice were first recorded in the 1830s (Searle et al. 2009). This adds credence to the hypothesis that mice on Auckland Island probably originated from whalers visiting the fertile Auckland Island wintering grounds of southern right whales, having stopped over at the Bay of Islands to re-supply.

HMNZS Wellington entering Port Ross, Auckland Islands. Photo by J.Russell

HMNZS Wellington entering Port Ross, Auckland Islands. Photo by J.Russell

Coastal rata forest and stream on Auckland Island. Photo by J. Russell

Coastal rata forest and stream on Auckland Island. Photo by J. Russell

In Easter 2015 the Navy from HMNZS Wellington provided logistical support to DOC and a team of biologists to visit the main Auckland Island and undertake studies of the introduced mammals currently present; pigs, cats and mice. This provided an opportunity to compare the mouse population dynamics with Antipodes Island, as well as cast an eye to future management options for these pests on Auckland Island. At over 45,000 hectares eradication of any mammalian pest is a daunting task on the main island. Pigs have decimated the megaherbs on the island, and cats have essentially eradicated seabirds. Thankfully nearby Adams Island was spared. Mice on nearby Enderby Island were eradicated in 1993, as an unintended side-effect of the rabbit eradication which took place (Torr 2002), marking what was to remain the largest mouse eradication in the world for quite some time.

James Russell from the University of Auckland was part of the team visiting the Auckland Islands in Easter 2015. His role was to study the cat and mouse populations on the main island with Grant Harper as well as conduct invertebrate sampling to compare with other subantarctic islands. To both their surprise, mice were almost undetectable on Auckland Island. With two intensive trapping grids in both coastal rata forest and upland tussock, totalling over 650 trapping nights, only one mouse was caught, equating to less than one mouse per hectare. This was in contrast to estimates of mice on the Antipodes Island coast reaching over 150 per hectare at the same time of year. The only place mice were readily caught was around the hut, even though this was only 50 metres from the trapping grid. This scarcity of mice also meant that the invertebrates they found on Auckland Island were much more similar to mouse-free islands in the Antipodes such as Bollons and Archway Island (Russell 2012), including large beetles and isopods. Overall this is encouraging news for Auckland Island, as low mice numbers means less food for cats (Harper 2010a), but raises interesting questions about what drives mouse population increases on Auckland Island, such as in winter 2007 when higher numbers of mice were caught (Harper 2010b).

References:

Harper, G. A. (2010a). Diet of feral cats on subantarctic Auckland Island. New Zealand Journal of Ecology, 34(2), 259-261. http://newzealandecology.org/nzje/2928

Harper, G. A. (2010b). Habitat use by mice during winter on subantarctic Auckland Island. New Zealand Journal of Ecology, 34(2), 262. http://newzealandecology.org/nzje/2927

Ruscoe, W. A. & Murphy E. C. (2005) House mouse. The handbook of New Zealand mammals. Oxford University Press, Auckland, 204-221.

Russell, J. C. (2012). Spatio-temporal patterns of introduced mice and invertebrates on Antipodes Island. Polar biology, 35(8), 1187-1195.

Searle, J. B., Jamieson, P. M., Gündüz, İ., Stevens, M. I., Jones, E. P., Gemmill, C. E., & King, C. M. (2009). The diverse origins of New Zealand house mice. Proceedings of the Royal Society B: Biological Sciences, 276(1655), 209-217.

Taylor, R. H. (1968). Introduced mammals and islands: Priorities for conservation and research. Proceedings of the New Zealand Ecological Society, 15, 61-67.

Torr, N. (2002). Eradication of rabbits and mice from subantarctic Enderby and Rose Islands. Turning the tide: the eradication of invasive species. IUCN SSS Invasive Species Specialist Group, Gland, Switzerland, 319-328.