Effects of mice on Antipodes

Written by Chrissy Wickes

Comparison between Bollons Island and the main Antipodes Island provides an opportunity to compare biodiversity on a mouse free island with an island where mice are present.

The influence mice are having on the ecosystem through the removal and/ suppression of various species is affecting the nutrient cycle on the main island.

Mice are thought to be impacting on the invertebrates, the vegetation and the birds on the main Antipodes Island.

Loxomerus. Photo by J. Marris

Loxomerus. Photo by J. Marris

 

Mice impacts on invertebrates

The most obvious impact mice are having is on the invertebrates.

Through comparison with mouse free offshore islands research teams have consistently confirmed mice are having significant impact on the abundance and diversity of invertebrates on the main Antipodes Island.

“The extinction of two species from the main Antipodes Island is believed to be due to mouse predation. Live specimens of Loxomerus n. sp. have been collected only from Bollons Island, where it is relatively common. Dead remains of this species were collected from dry rock of volcanic spatter cones on Antipodes Island by P. M. Johns (pers. comm. 1999) during the 1969 University of Canterbury expedition but no live specimens were found” (Marris 2000).

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Senecio radiolatus ssp. Photo by B. Rance

Senecio radiolatus ssp. Photo by B. Rance

 

Mice impacts on vegetation

“There are three potential impacts upon the flora that could result from the presence of mice. These are browsing of plants, seed predation and indirect impacts resulting from impacts to fauna” (Rance 2014).

An example is the possible effects on the distribution and abundance of the Nationally Critical Lepidium oligodontum (Cooks scurvy grass) which may have been compromised by mice consuming its seed. In addition the endemic, Senecio radiolatus ssp. Antipodes (Antipodes groundsel) is found in surprisingly low numbers, and like other megaherbs it is likely its seeds are targeted by mice for food. As a semi-annual, it may have a mice- compromised presence on the fertile upland plains of the Antipodes (Geoff Rogers 2014).

Vegetation monitoring, including the establishment of permanent vegetation plots occurred in 2014. Information gathered from these plots will provide us with a better understanding of plant communities, the impacts of mice on communities and species and to measure the recovery of potentially mouse sensitive flora species.

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Reischek's parakeet feeding on seeds. Photo by K. Walker

Reischek’s parakeet feeding on seeds. Photo by K. Walker

 

Mice impacts on birds

After visiting Bollons Island and the main Antipodes Island in 2014, researcher Denise Fastier made the following comment regarding affects of mice on bird species; “Overall the number of snipe seen/heard were orders of magnitude greater on Bollons than the main island – we saw around the same number in just over half a day with essentially one observer (Brian and I were together all day) as the team of 10 saw in the following 2.5 weeks on the main Antipodes island. I would expect the removal of mice will change that.” This remarkable difference in population densities between the two islands is particularly obvious for snipe but anecdotally mice seem to be impacting all four endemic land bird species through competition; Antipodes parakeet (Cyanoramphus unicolor), Reischek’s parakeet (Cyanoramphus hochstetteri), Antipodes Island snipe (Coenocorypha aucklandica meinertzhagenae) and Antipodes Island pipit (Anthus novaeseelandiae steindachneri).

The Black-bellied Storm Petrel (Fregetta tropica) is also abundant and breeding on Bollons Island but is in low numbers and not breeding on the main Antipodes Island. This too could be attributed to mice predation (Imber et al., 2005) (Angel et al., 2009 pg. 1748) (nzbirdsonline.org.nz).

Similarly the subantarctic little shearwater (Puffinus elegans) only breeds on the mouse free offshore islands, indicating that they are unable to coexist with mice on the main Antipodes Island. Mice may also be affecting the breeding success of the Antarctic terns (Sterna vittata bethunei) (nzbirdsonline.org.nz).

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Resources:

http://nzbirdsonline.org.nz/

Angel A., Wanless R.M.,Cooper J. 2009. Review of impacts of the introduced house mouse on islands in the Southern Ocean: are mice equivalent to rats? Biol Invasions, 2009, 11:1743–1754.

Marris, J. W. M. June 2000. The beetle (Coleoptera) fauna of the Antipodes Islands, with comments on the impact of mice; and an annotated checklist of the insect and arachnid fauna. Journal of The Royal Society of New Zealand, Volume 30 Number 2, pp 169-195.

Rance B. 2014. Antipodes Island flora and vegetation report. Unpublished report; Department of Conservation. Unpublished.

Rogers, Geoff. 2014. Feasibility of incorporating plants and vegetation in performance monitoring of the eradication of mice from Antipodes Island. Unpublished.