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Beyond Kapiti - A decade of invasive rodent eradications from New Zealand islands.
BRB
Available Online

Keith Broome

New Zealand, an archipelago of more than 2000 islands, has a terrestrial fauna especially depauperate in native land mammals. Kiore (Rattus exulans) was the first of four rodent species introduced by people. A project to eradicate invasive rats from Kapiti Island in 1996, represented a turning point in the technology, complexity and scale at which managers of natural heritage on New Zealand islands could operate. This paper includes case studies of some significant projects targeting rodents, sometimes with other introduced mammals, undertaken in the 12 years following Kapiti. Details of the methods, costs, results and outcomes are provided for Kapiti, Whenua Hou, Tuhua, Campbell, Raoul, Hauturu, Taukihepa, and Pomona islands, collectively representing a total of over 23,000 ha of habitat cleared of introduced mammals. Research and trials undertaken in the Kapiti project provided the basis for future environmental risk assessments, allowing other projects to focus on knowledge gaps. New trends in invasive species eradication in New Zealand include more challenging multi-species eradication projects, some of which are undertaken by self- funded community groups. To summarise the lessons of the New Zealand experience: a programmatic approach is recommended which will fit each eradication within a context or framework of goals for those islands; address biosecurity issues at the outset; build capability to attempt the most challenging and rewarding projects; facilitate investment in monitoring and manage expectations of stakeholders to ensure their ongoing support. Success breeds success but is never guaranteed.
Impacts of aerial 1080 possum control operations on North Island robins and moreporks in Pureora 1997 and 1998
BRB
Available Online

Knegtmans, Jaap W.

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Powlesland, Ralph G.

,

Styche, Andrew

1999
This is the final report describing the results from the second and third years of a three-year programme to determine the costs and benefits of aerial 1080 possum control operations to North Island robins (Petroica australis longipes) and moreporks (Ninox novaeseelandiae) in Pureora Forest Park, North Island, New Zealand. During this study robins were individually colour-banded, and moreporks radio-tagged in both treatment and non-treatment study areas. A poison operation using carrot baits in August 1997 covered 8577 ha and incorporated the 300 ha Waimanoa study area. A poison operation using cereal baits in August 1998 covered just the 200 ha Long Ridge study area. After the 1997 operation, very few possums remained alive and rat foot-print tracking indices remained very low during the robin nesting season (September 1997 February 1998). Similarly, possum and rat population indices were much reduced after the 1998 operation, but rats and possums were found in a small portion of the study area, presumably because it did not receive baits. Following both the 1997 and 1998 poison operations, there was no significant difference in the proportion of banded robins that disappeared from the non-treatment and treatment study areas. During the 1997/98 nesting season, the nesting success of robins was significantly better in the treatment area than in the non-treatment area. One year after the poison operation (spring 1998), the robin population in the treatment area had increased by 37% on the number present just prior to the poison operation, compared with 16.3% in the non-treatment area. No radio-tagged moreporks were available in the treatment area during the 1997 poison operation, and all three radio-tagged in each of treatment and non-treatment areas were still alive two months after the poison operation in 1998.
Monitoring possum numbers following 1080 poison control at Mapara reserse
BRB

Stephens, Theo

1992
1080 poisoned baits (Wanganui No. 7) were aerially spread throughout the three blocks of Mapara reserve in September 1990 and again in October 1991 to control possums. Changes in possum abundance were monitored by trapping, using a modified version of Seber's "removal method". A trapping method was chosen in preference to spotlight counts, bait take and pellet counts because a suitable control area, critical to these methods, was not available; traps were already in place on permanent sets; and trapping contributes to the control objective. The removal index was considered more suitable for monitoring than the simpler catch per unit effort index (number of possums caught per 3 trap-nights) because the latter is affected by variation in possum catchability, as well as possum abundance. The removal method depends on obtaining declining catches on successive nights. There is a significant risk that the method will not give a meaningful result if trapping intensity is inadequate or if nightly variation in catchability is excessive. The catch per unit effort index is still available if an abundance index based on the removal method is unobtainable. The 1990 poison operation reduced possum numbers to 21% of pre-poison abundance (95% Confidence Limits (CL) were 13.8% and 28.2%). During the following year, possum numbers built up to 39.5% (95% CL 28.7% and 50.3%) of pre-poison abundance and 1991 poison operation caused a non-significant reduction to 32.2% (95% CL 21.8% and 42.6%). Thus the September 1991 operation probably did not reduce possum densities to the level attained in October 1990. The reason for the poor kill following the 1991 poison drop is unknown, although several possibilities are identified.