Anthony Rendall (Centre for Integrative Ecology, School of Life and Environmental Sciences, Deakin University, Melbourne Australia) and colleagues have published in the open-access journal PloS One on the use of camera traps to detect activity by rodents among breeding Short-tailed Shearwaters Puffinus tenuirostris on Phillip Island, Australia

The paper’s abstract follows:

“Invasive rodent species have established on 80% of the world’s islands causing significant damage to island environments.  Insular ecosystems support proportionally more biodiversity than comparative mainland areas, highlighting them as critical for global biodiversity conservation.  Few techniques currently exist to adequately detect, with high confidence, species that are trap-adverse such as the black rat, Rattus rattus, in high conservation priority areas where multiple non-target species persist.  This study investigates the effectiveness of camera trapping for monitoring invasive rodents in high conservation areas, and the influence of habitat features and density of colonial-nesting seabirds on rodent relative activity levels to provide insights into their potential impacts.  A total of 276 camera sites were [sic] established and left in situ for 8 days.  Identified species were recorded in discrete 15 min intervals, referred to as ‘events’.  In total, 19 804 events were recorded.  From these, 31 species were identified comprising 25 native species and six introduced.  Two introduced rodent species were detected: the black rat (90% of sites), and house mouse Mus musculus (56% of sites).  Rodent activity of both black rats and house mice were positively associated with the structural density of habitats.  Density of seabird burrows was not strongly associated with relative activity levels of rodents, yet rodents were still present in these areas.  Camera trapping enabled a large number of rodents to be detected with confidence in site-specific absences and high resolution to quantify relative activity levels.  This method enables detection of multiple species simultaneously with low impact (for both target and non-target individuals); an ideal strategy for monitoring trap-adverse invasive rodents in high conservation areas.”

Short-tailed Shearwater, photograph by Mark Carey

Reference:

Rendall, A.R., Sutherland, D.R., Cooke, R. & White, J. 2014.  Camera trapping: a contemporary approach to monitoring invasive rodents in high conservation priority ecosystems.  PloS One doi:10.1371/journal.pone.0086592.

John Cooper, ACAP Information Officer, 20 August 2014

Frances Zewe (Ecosystem Management, School of Environmental and Rural Sciences, University of New England, Armidale, Australia) and colleagues have published in the journal Australian Mammalogy on trapping alien Black Rats Rattus rattus but not native Swamp Rats R. lutreolus on a Wedge-tailed Shearwater Puffinus pacificus island.

The paper’s abstract follows:

“Novel bait stations can be used as a targeted method of delivering bait by exploiting behavioural traits of the target species.  On Muttonbird Island, New South Wales, the black rat (R. rattus) has been baited to aid the conservation of the island’s wedge-tailed shearwater (Ardenna pacifica) colony, which may result in poisoning of the sympatric swamp rat (Rattus lutreolus).  We aimed to design a bait station that R. rattus could reach, but that R. lutreolus could not.  We found that 11 (92%) of 12 captive R. rattus reached the bait chambers by climbing a 50-cm vertical pipe, whereas only four (18%) of 22 R. lutreolus reached these bait stations.  In a field trial on Muttonbird Island R. rattus entered the bait chamber on an average of 5.3 events per night of vertical bait station deployment, but R. lutreolus did not enter the stations.  In a field trial on the mainland at a site with a high density of R. lutreolus, this species was detected in one vertical bait station five times, equating to an average of 0.017 events per night of vertical bait station deployment.  We conclude that R. rattus readily climbs a 50-cm pipe to enter the bait station, whereas R. lutreolus rarely or never does on Muttonbird Island or at the mainland site.”

Wedge-tailed Shearwater, photograph by Alan Burger

Reference:

Zewe, F., Meek, P., Ford, H. & Vernes, K. 2014.  A vertical bait station for black rats (Rattus rattus) that reduces bait take by a sympatric native rodent.  Australian Mammalogy 36: 67-73.

John Cooper, ACAP Information Officer , 19 August 2014

The Wedge-tailed Shearwater Puffinus pacificus is the only seabird currently known to breed within the James Campbell National Wildlife Refuge on the Hawaiian island of Oahu.  Reproductive success is unknown but predation is reported as a limiting factor.  An intensive, year-round predator control programme aims to reduce the impact of invasive predators.

Several other seabird species have been identified for introduction by the refuge’s 2011 conservation plan because of their habitat preferences at other breeding sites in Hawaii that resemble the conditions at the Refuge.  These include Laysan Albatross Phoebastria immutabilis and Black-footed Albatross P. nigripes.  These species are currently observed along the Refuge coastline and in the general vicinity.  Laysan Albatrosses have attempted to breed near the Refuge in the past but were thought to have been killed by domestic dogs; introduced albatrosses would thus need to be protected by a predator-proof fence.

“As rising sea levels begin to negatively impact important seabird nesting sites in more vulnerable remote Pacific islands, nesting sites on the main Hawaiian Islands (which are generally higher in elevation) will become increasingly important,” including for Laysan Albatrosses.

Laysan Albatrosses, photograph by Ross Wanless

One possible source for founders of a new seabird colony could be Laysan Albatross eggs from the exchange programme at the Pacific Missile Range Facility Barking Sands on Kauai where eggs are removed to reduce risks of bird air strikes (click here).  The chicks from these eggs could then be hand reared at the refuge and allowed to fledge from the colony site.

Reference:

O‘ahu National Wildlife Refuge Complex 2011.  James Campbell National Wildlife Refuge Draft Comprehensive Conservation Plan and Environmental Assessment.  Honolulu: U.S. Fish & Wildlife Service.  283 pp.

John Cooper, ACAP Information Officer, 18 August 2014

Last month, ACAP Latest News reported on plans to rid New Zealand’s Great Mercury Island of its alien rats and cats (click here).

Great Mercury Island

News is in from the Department of Conservation that two aerial bait drops were successfully completed on Great Mercury last week (click here).  Time will tell –in about two years’ time - whether the island has become rat free, helping its breeding Grey-faced Petrels Pterodroma macroptera gouldi.

The Mercury Islands are a group of seven islands eight kilometres off the north-east coast of the North Island of New Zealand.  The six smaller islands in the group are rodent free after eradication operations between 1987 and 1997 removed Pacific Rats Rattus exulans.  They have been identified as an Important Bird Area by BirdLife International because they support up to 3000 breeding pairs of Pycroft's Petrels Pterodroma pycrofti, as well as Little Shearwaters Puffinus assimilis.  Removing rats from Great Mercury will help with biosecurity for the rest of the island group: all rat-free seabird islands.

“Removing the rats and feral cats from the island involved precisely targeted aerial applications of bait using specially designed buckets carried by helicopter.  The helicopter pilots use satellite navigation (GPS) technology to ensure the bait is spread only where intended.”

This year marks 50 years since the first New Zealand island was made pest free.  Ruapuke/ Maria Island was declared pest free in 1964 after the successful removal of Norway Rats Rattus norvegicus.

Read more on the Great Mercury operation here.

John Cooper, ACAP Information Officer, 17 August 2014