The PCSU and HPI-CESU Technical Reports 1974 - current

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This collection presents the Pacific Cooperative Studies Unit (PCSU) and the Hawaii-Pacific Islands Cooperative Ecosystem Studies Unit (HPI-CESU) Technical Reports. The collection represents reports from 1974 to the present.


The Pacific Cooperative Studies Unit
& The Hawaii-Pacific Islands cooperative
Ecosystems Studies Unit
University of Hawaii at Manoa
3190 Maile Way
St. John Hall #408
Honolulu, HI 96822-2279


Recent Submissions

Now showing 1 - 10 of 212
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    An assessment of lethal trap performance and efficacy at Haleakala National Park
    ( 2022-06) Kekiwi, Erika ; Purdy, Kayla ; Kaholoaa, Raina ; Natividad Bailey, Cathleen
    Control of non-native predators is vital for managing resources at Haleakalā National Park and has been ongoing since the 1970s. A 2016 evaluation of the trapping program suggested incorporating lethal traps to improve capturing predators. A revised Predator Control Management Plan was developed based on this evaluation, including lethal traps. Since lethal traps can catch non-target species, including federally listed threatened and endangered species, evaluating these traps was necessary. This project assessed three lethal traps for performance and efficacy: Goodnature® A24, DOC 250, and Belisle 220 Super X body grip traps. We evaluated the use of exclusionary box designs and careful trap placement to determine if these features would prevent the capture of non-target species. Captures of species for each trap and interactions of target and non-target species with traps were examined to evaluate trap and exclusion device performance. Wildlife cameras paired with all lethal traps showed no interactions or “unacceptable” interactions with traps or trap boxes by native species, including federally listed species. Capture rates from lethal and live traps were compared in similar areas. Of captures from Goodnature traps, 99% were rats, and 1% were mongooses. Of DOC 250 captures, 71% were mongooses, 25% were rats, and 4% were cats. Body grip traps did not capture any animals during the evaluation period but captured one mongoose during the efficacy period. Goodnature traps had the highest capture rate for rats, followed by DOC 250 and cage traps. DOC 250 had the highest capture rates for mongooses, followed by cage traps. Staff noted that although lethal traps require considerable labor for initial setup, lethal traps required much less labor to monitor than live traps and were advantageous in remote areas. This study suggests that incorporating lethal traps could greatly benefit the predator control program at Haleakalā National Park.
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    Best Management Practices to Protect Endangered and Native Birds at Solar Installations in Hawai`i
    (Pacific Cooperative Studies Unit, 2021-11) Penniman, Jay F. ; Duffy, David C.
    Solar Energy facilities in Hawaiʻi are a growing major source of low carbon emission energy generation as the state strives to reduce emissions of greenhouse gasses to prevent the worst predictions of global climate change. It is incumbent upon developers of these facilities to consider wildlife impacts and take measures to mitigate for them. While the technology is relatively new there are evolving best management practices that should be undertaken. We identify five endangered waterbird species, three listed seabird species, and one raptor of conservation concern, that have been or may be at risk from solar energy generation facilities in Hawaiʻi. In addition, there are migratory species: fifteen waterbirds and seventeen shorebirds that may be vulnerable. We review relevant literature for impacts and consequences of wildlife interactions with solar energy facilities and recommend best management practices to minimize wildlife impacts. Design considerations for minimizing wildlife impacts are identified, and must be implemented and followed by monitoring to identify and quantify downed wildlife incidents and further development of effective mitigation strategies.
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    Update on the status of the avifauna of Lehua Islet, Hawai'i, including initial response of seabirds to rat eradication
    (Pacific Cooperative Studies Unit, 2021-08) Raine, André ; Vanderwerf, Eric ; Khalsa, Mele ; Rothe, Jennifer ; Driskill, Scott
    Lehua Islet is a small volcanic islet located 1 km north of Ni‘ihau, protected by the State of Hawai‘i as a Seabird Sanctuary because of its large seabird colonies. Between December 2011 and May 2021, data was collected using a variety of methods to provide an update of the islet’s avifauna, with a particular focus on seabirds. In 2017 a rat eradication project was undertaken to remove the Polynesian Rat Rattus exulans and the islet was officially declared rat free on 20 April 2021. This report therefore provides both an update on the status of the avifauna of Lehua and an assessment of the initial impact of the rat eradication project on breeding seabirds. A total of 39 bird species were recorded on Lehua over the study period, including 18 seabird species (9 confirmed breeding). The most numerous breeding seabird was the Wedge-tailed Shearwater Ardenna pacifica, estimated at 22,226 ± 2,981bp. Lehua is therefore an important refuge for this species, which suffers significant predation by cats and dogs across the Main Hawaiian Islands. Several species, particularly burrow-nesting seabirds, responded positively to rat eradication. The most dramatic changes occurred in the Bulwer’s Petrel Bulweria bulwerii breeding population. This species was rarely encountered before eradication, but numbers of burrows located, the percentage of burrows where adults were confirmed breeding and two measures of nest success increased after eradication. Wedge-tailed Shearwaters also responded positively, with Mayfield Nest Success Estimates significantly higher in the three years after rats were eradicated than in the two years before eradication (t=2.37, p=0.02). Conversely, one species - the endangered Band-rumped Storm-petrel Oceanodroma castro - appeared to decline after rat eradication (as measured via call rates on acoustic sensors), although the change was not significant. Rat eradication has been a critical milestone in the conservation of Lehua Islet, and further natural recovery of seabirds can be expected. Future management actions will be key for capitalizing on the early successes of the rat eradication project. These include social attraction of seabirds that have been extirpated from the islet and habitat restoration through invasive plant removal and outplanting of native species. Regular control of the two remaining non-native predators (Barn Owl Tyto alba and Cattle Egret Bubulcus ibis) on the islet by well-trained predator control specialists will also be critical, as Barn Owls could reverse conservation gains and prevent new seabird species from colonizing. Lastly, ensuring a rigorous biosecurity program and monitoring strategy is vital to prevent reinvasion.
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    2019 Kiwikiu Conservation Translocation Report
    ( 2021-03-15) Warren, Christopher C. ; Berthold, Laura K. ; Mounce, Hanna L. ; Luscomb, Peter ; Masuda, Bryce ; Berry, Lainie
    The U.S. Fish & Wildlife Service (USFWS) Recovery Plan for the kiwikiu (Maui Parrotbill; Pseudonestor xanthophrys) (USFWS 2006) recommended establishing a second population within its historical range to protect the species from catastrophic loss in its small current range. In addition to the inherent threats of a small population and small range size, the current kiwikiu population is located on the windward (northeastern) slope of Haleakalā where they are under threat from severe weather events and frequent rainfall that have been shown to reduce reproductive success. The Kahikinui region of Maui on the leeward (southern) slope of Haleakalā was selected as the site of a new population of kiwikiu. Nakula Natural Area Reserve (NAR) was selected as the first release site to begin establishing the species in the Kahikinui region. The Maui Forest Bird Working Group (MFBWG; hereafter “the working group”) wrote a comprehensive Kiwikiu Reintroduction Plan (MFBWG 2018). After many years of preparation, which included building infrastructure, controlling predators, and reducing mosquito densities in Nakula NAR, 14 kiwikiu were transferred to the site: seven wild birds translocated from Hanawī NAR and seven from a conservation breeding facility managed by San Diego Zoo Global. The birds from the conservation breeding facility and the wild were moved to Nakula NAR in mid-October 2019 and releases were completed a few weeks later. After release, birds were monitored using radio telemetry through November 2019 at which point all birds either had died or disappeared (except for one individual that was transferred back to the conservation breeding facility). Necropsies indicated avian malaria as the primary cause of death for all recovered individuals and little hope remains for the few remaining missing birds at the site. Unexpectedly high densities of mosquitoes were later confirmed within the release site. Further investigation revealed that the translocated wild individuals tested positive for the malaria parasite prior to the move to Nakula NAR. In this report, we discuss the strategies that were employed during the kiwikiu translocation, the outcome of those actions, and the steps moving forward for both future release improvements and recovery strategies for the kiwikiu.
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    Updated avifauna of Mokuʻaeʻae Rock Islet 2019
    (Pacific Cooperative Studies Unit, 2020-04) Raine, André ; Rothe, Jennifer ; Driskill, Scott
    Mokuʻaeʻae Rock Islet, located off the North shore of Kauaʻi is protected as a Hawaiʿi State Seabird Sanctuary. In the late 1970s it was also the site of a cross-fostering project for the endangered Newell’s Shearwater Puffinus newelli. Few avifauna surveys have been undertaken on the islet, with the most recent prior to this report being undertaken by the Kauaʿi Endangered Seabird Recovery Project (KESRP) in 2013 and 2015 respectively. For this study, the islet was surveyed in June and October of both 2018 and 2019. Burrow searches were conducted across the entire islet to obtain breeding population estimates for each species and to assess whether there was any recent sign of Newell’s Shearwater breeding activity. Two Song Meters (Wildlife Acoustics, SM2+) were also deployed each year at the same two locations, with data collected for two months in June and July. Auditory surveys were also conducted in June 2018 for two hours after sunset and one and a half hours before sunrise. A total of 17 bird species was recorded over the course of the two years, consisting of eight seabird species (of which three – Bulwer’s Petrel Bulweria bulwerii, Wedge-tailed Shearwater Ardenna pacifica and Red-tailed Tropicbird Phaethon rubricauda - were confirmed breeding), one native waterfowl species (Nene Branta sandvicensis, which is the first confirmed breeding record on the islet for this species), five migratory species, and three introduced species. As with previous searches of the islet, there was no sign of Newell’s Shearwater breeding activity and only a handful of calls recorded, concurring with previous reports that the cross-fostering project on the islet was not successful. Despite this, the islet remains an important sanctuary for the three seabird species recorded as breeding on the islet during the surveys and remains the only known breeding colony of Bulwer’s Petrel on Kauaˈi. Depredation by the introduced Barn Owl Tyto alba was identified as a significant threat to seabirds breeding on the islet. Future management actions are suggested to improve the islet for breeding seabirds.
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    Evaluating the risk of avian disease in reintroducing the endangered Kiwikiu (Maui Parrotbill: Pseudonestor xanthophrys) to Nakula NAR, Maui, Hawai‘i
    (Pacific Cooperative Studies Unit, 2019-03) Warren, Christopher ; Berthold, Laura ; Mounce, Hanna ; Foster, Jeffrey ; Sackett, Loren
    Avian malaria and other introduced diseases have had profound negative effects on Hawaiian honeycreepers, contributing to numerous extinctions and severely limiting the ranges of the remaining species. These diseases, concordant with habitat loss, are thought to restrict many species to narrow ranges at high elevations where cooler climates restrict reproduction of both the malaria parasite, Plasmodium relictum, and its mosquito vector, Culex quinquefasciatus. The Kiwikiu (Maui Parrotbill, Pseudonestor xanthophrys) is a critically endangered honeycreeper that formerly existed throughout Maui and Moloka‘i but now occupies roughly 30 km2 above 1400 m above sea level (asl) on the windward slopes of Haleakalā volcano. The species is thought to be highly susceptible to avian malaria based on its limited range and reported mortality in related species. The primary conservation action proposed for Kiwikiu is to expand the species’ range by reintroducing Kiwikiu to high elevation native forests on the south-facing leeward slope of Haleakalā. As part of an assessment of the suitability of the proposed release site, Nakula Natural Area Reserve, we sought to evaluate the risk of avian disease (i.e., avian malaria and pox) to the future Kiwikiu population. To do this, we trapped adult mosquitoes and surveyed for larvae throughout the release area in 2015–2016. We also tested blood samples from common bird species in Nakula using quantitative polymerase chain reaction analyses to estimate disease prevalence within the current bird population at the release site. To compare disease prevalence to habitat currently occupied by Kiwikiu, we also trapped mosquitoes and tested avian blood samples from common species in The Nature Conservancy’s Waikamoi Preserve in 2016. Unexpectedly, we captured adult and larval C. quinquefasciatus at much higher rates in Nakula than those reported from similar locations at comparable elevations (1530-1620 m asl) throughout Hawai‘i but did not capture C. quinquefasciatus in Waikamoi (1675-1700 m asl). Although leeward slopes receive far less rainfall than windward slopes, the drainages in Nakula contain small pools of water that can provide suitable breeding habitat for the mosquitoes. The frequency of high-flow periods in streams in Waikamoi may regularly “flush out” pools, reducing larval habitat. In contrast, the warmer temperatures and long periods between high-flow events may allow mosquitoes to persist year-round in Nakula. In contrast to mosquito capture rates, analysis of blood samples revealed similar or lower rates of avian malaria in two common honeycreeper species in Nakula compared to similar sites. We also found several individuals of two common honeycreeper species (i.e. Hawaiʻi ʻAmakihi [Chlorodrepanis virens] and ʻIʻiwi [Drepanis coccinea]) captured above 1900 m asl in Waikamoi to be positive for avian malaria. These results suggest that 1) although the persistence of mosquitoes represents an increased risk of infection in Nakula, the Plasmodium parasite may still be physiologically limited by environmental conditions at the release site, 2) the management of mosquitoes (e.g. biopesticides) is advisable to reduce infection risk, and 3) Kiwikiu may be at higher risk in its current range than previously considered. While creating a second population of Kiwikiu in Nakula is critical to safeguarding this species from extinction, mitigating the threat of avian malaria on a larger scale will be the only way to achieve island-wide recovery.
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    Experimental restoration trials in Nakula Natural Area Reserve in preparation for reintroduction of Kiwikiu (Pseudonestor xanthophrys)
    (Pacific Cooperative Studies Unit, 2019-01) Warren, Christopher ; Mounce, Hanna ; Berthold, Laura ; Farmer, Chris ; Leonard, David ; Duvall, Fern
    The native montane mesic forest in the Kahikinui region of Maui, Hawai‘i USA has been degraded by non-native ungulates for over a century. This has resulted in large areas of non-native grassland and savanna with small intact native forest patches, mainly in steep gulches. The Nakula Natural Area Reserve (NAR), on the southwestern slope of Haleakalā volcano, was selected as the site of the reintroduction of Kiwikiu (Pseudonestor xanthophrys), a critically endangered songbird currently found only in a small range on the northern slope of the volcano. This area was selected for the reintroduction because it is located within a mesic koa (Acacia koa) forest representing some of the best potential habitat outside of the current Kiwikiu range. Historic accounts noted the Kiwikiu’s affinity for koa as a foraging substrate, although little koa forest remains on Maui. Intensive forest restoration has created new habitat and enhanced the existing habitat in Nakula to the point where the reserve may now be capable of supporting a small population of Kiwikiu and other native birds. As a precursor to reintroduction efforts, we designed experimental trials to inform managers of the most efficient and effective techniques to restore the forest in Nakula NAR and surrounding region. Trial plots were established in open grass-dominated areas within a fenced, ungulate-free portion of the reserve to investigate natural regeneration, outplanting, and seed broadcast as restoration techniques under a number of conditions. Treatments to suppress and/or remove non-native grass were implemented as these grasses likely reduce germination of native seedlings and potentially influence outplanting success. Some plots were treated with herbicide and the dead grass biomass was removed to expose bare topsoil in a subset of these plots. Additional plots were established under mature koa trees to investigate natural recruitment and the success of these same restoration techniques in this microhabitat. In two years, natural regeneration was largely limited to ‘a‘ali‘i (Dodonea viscosa) and koa, and was enhanced by the application of herbicide followed by the removal of the grass biomass. Outplanting survivorship was high in most species, exceeding 80% after two years in five of seven species. Treatment application had little effect on survivorship, but the growth rates in four of the seven species planted was greatest in plots where herbicide was applied prior to planting. Seed broadcast was not found to be an effective treatment of producing seedlings. Based on our results, we recommend non-native grass biomass removal combined with outplanting as the primary method of forest restoration in Nakula NAR and the surrounding region.
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    The Nihoku Ecosystem Restoration Project: A case study in predator exclusion fencing, ecosystem restoration, and seabird translocation
    (Pacific Cooperative Studies Unit, 2018-09) Young, Lindsay C. ; Behnke, Jessica H. ; Vanderwerf, Eric A. ; Raine, André F. ; Mitchell, Christen ; Kohley, C. Robert ; Dalton, Megan ; Mitchell, Michael ; Tonneson, Heather ; DeMotta, Mike ; Wallace, George ; Nevins, Hannah ; Hall, C. Scott ; Kim, Uyehara
    Newell’s Shearwater (Puffinus auricularis newelli; NESH) and Hawaiian Petrel (Pterodroma sandwichensis; HAPE) are both listed under the Endangered Species Act of 1973 and are declining due to collisions with power lines and structures, light attraction, predation by feral cats, pigs, rats, and introduced Barn Owls, habitat degradation by feral ungulates (pigs, goats) and invasive exotic plants. Protection of NESH and HAPE on their nesting grounds and reduction of collision and lighting hazards are high priority recovery actions for these species. Given the challenges in protecting nesting birds in their rugged montane habitats, it has long been desirable to also create breeding colonies of both species in more accessible locations that offer a higher level of protection. Translocation of birds to breeding sites within predator exclusion fences was ranked as priority 1 in the interagency 5-year Action Plan for Newell’s Shearwater and Hawaiian Petrel. In 2012, funding became available through several programs to undertake this action at Kilauea Point National Wildlife Refuge (KPNWR), which is home to one of the largest seabird colonies in the main Hawaiian Islands. The project was named the “Nihoku Ecosystem Restoration Project” after the area on the Refuge where the placement of the future colony was planned. The Nihoku Ecosystem Restoration Project is a result of a large partnership between multiple government agencies and non-profit groups who have come together to help preserve the native species of Hawaii. There were four stages to this multi-faceted project: permitting and biological monitoring, fence construction, restoration and predator eradication, followed by translocation of the birds to the newly secured habitat. The translocation component is expected to last five years and involve up to 90 individuals each of NESH and HAPE. Prior to fence construction, baseline monitoring data were collected in order to provide a record of initial site conditions and species diversity. Surveys were conducted quarterly from 2012-2014, investigating diversity and richness of plant, invertebrate, mammalian, and avian species. A 650 m (2130 ft) long predator proof fence was completed at Nihoku in September 2014, enclosing 2.5 ha (6.2 ac), and all mammalian predators were eradicated by March 2015. From 2015-2017, approximately 40% of the fenced area (~1 ha) was cleared of non-native vegetation using heavy machinery and herbicide application. A water catchment and irrigation system was installed, and over 18,000 native plants representing 37 native species were outplanted in the restoration area. The plant species selected are low-in-stature, making burrow excavation easier for seabirds while simultaneously providing forage for Nene (Branta sandvicensis). Habitat restoration was done in phases (10-15% of the project per year) and will be continued until the majority of the area has been restored. In addition to habitat restoration, 50 artificial burrows were installed in the restoration to facilitate translocation activities. From 2012-2017 potential source colonies of NESH and HAPE were located by the Kauai Endangered Seabird Recovery Project (KESRP) with visual, auditory, and ground searching methods at locations around Kauai. The sites that were selected as source colonies for both species were Upper Limahuli Preserve (owned by the National Tropical Botanical Garden; NTBG) and several sites within the Hono o Na Pali Natural Area Reserve system. These sites had high call rates, high burrow densities to provide an adequate source of chicks for the translocation, and had active predator control operations in place to offset any potential impacts of the monitoring. Translocation protocols were developed based on previous methods developed in New Zealand; on the ground training was done by the translocation team by visiting active projects in New Zealand. In year one, 10 HAPE and eight NESH were translocated, and the goal is to translocate up to 20 in subsequent years for a cohort size of 90 birds of each species over a five year period. Post-translocation monitoring has been initiated to gauge the level of success, and social attraction has been implemented in an attempt to attract adults to the area. It is anticipated that the chicks raised during this project will return to breed at Nihoku when they are 65-6 years old; for the first cohort released in 2015 this would be starting in 2020. Once this occurs, Nihoku will be the first predator-free breeding area of both species in Hawaii.
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    A report on the guano-producing birds of Peru (“Informe sobre Aves Guaneras”)
    (Pacific Cooperative Studies Unit, 2018-07) Vogt, William ; Dufffy, David Cameron
    (Modified from the original) Vogt studied the Guanay Cormorant (Phalacrocorax bougainvillii), Peruvian Booby (Sula variegata), and Peruvian Pelican (Pelecanus thagus) for almost three years (1938 - 1940). The nesting range of these species extends from 04035'S to 380S, covering an area of considerable geographical diversity. The climate is briefly described. The report contains details of the oceanography and marine biology of a part of the nesting range of the birds, and a rejection of the theory that a warm southward-flowing surface current causes major changes on climate and breeding season for guano birds. The histories of past abnormal years and their effects on the birds are reported. The average density of Guanay Cormorant nests is 313.9 ± 3.76 per 100 m2. The ecological efficiency of the islands and their microclimates are linked. The Guanay Cormorant is limited to nesting on the windy parts of the island, which are the coolest, as there is an inverse relation between wind and temperature. A detailed description of the social behavior of the Guanay Cormorant, including its feeding and nesting, is given. Nesting is concentrated in spring and summer. The breeding season keeps the adults on the island for four months every year. The average Guanay Cormorant clutch size is 3.13 ± 0.101 eggs and incubation lasts 27 days. Nesting in large colonies protects nests because fewer birds are at the edges in larger colonies. Various causes of mortality are described. The only significant predator of the Guanay Cormorant may be the Andean Condor (Vultur gryphus). Food is probably the most important limiting factor for the birds. There is a correlation between the abundance of food for birds and the abundance of diatoms. Each Guanay Cormorant eats approximately 215 g/day of food and no more than 316 g/day. Annually, each Guanay Cormorant eats 78.4 to 115.4 kg/year of the Peruvian Anchoveta (Engraulis ringens) and produces approximately 15.8 kg of guano per year. The quantity of fish consumed by birds in the year prior to the guano harvest of 1940 was between 711,903 and 917,150 metric tons. Based on extensive data, this is much lower than previous estimates. Each ton of guano is the result of 4.95 - 7.3 tons of fish consumed, but the guano that the company removes from the islands is only a small proportion of the guano that the birds deposit at sea, where it may act as an important fertilizer for plankton. Preliminary studies suggest that anchoveta are migratory. I have rejected, because of a lack of supporting data, the theory that anchoveta are still present during food shortages, but at depths too great for them to be taken by birds. A preliminary study of 1,427 anchoveta indicated a marked reduction in the year-classes hatched in the spring and summer of 1939 and 1940, when the birds died of hunger. Anchoveta spawned in 1938 were the most abundant. The Peruvian Anchoveta appears similar in biology to the California Sardine (Sardinops sagax caerulea). The commercial anchoveta fishery should be carefully monitored as it represents one of the most serious potential threats to the guano industry. Various interactions of the birds and humans are discussed. I review the history of the guano birds, based on available data, from the pre-Columbian period to the present. The ecologies of the Peruvian Booby and Peruvian Pelican are discussed. Each species seems to occupy a distinct niche so that, within broad limits, the three do not compete with one another. Interactions or the synecology of plants and animals connected with the guano birds appear to be so complex that they require more thorough study. Various management methods are suggested that might allow an increase in the numbers of birds and the proportion of guano harvested. Various management methods are suggested that might allow an increase in the numbers of birds and the proportion of guano harvested.
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    Post-implementation assessment of novel rodent control devices for protection of high elevation endangered species at Hawai`i Volcanoes National Park
    (Pacific Cooperative Studies Unit, 2017-12) Coad, Heather ; McDaniel, Sierra ; Misajon, Kathleen ; Forbes-Perry, Charlotte
    Invasive species, including rats, threaten the existence of many of Hawai`i’s native species pushing them to the brink of extinction. Hawai`i Volcanoes National Park has a long history of successfully managing ecosystems and providing rare species habitat through systematic invasive species control. Landscape level rodent control is prohibitively expensive; however, localized control has proven cost-effective while providing significant resource benefit. A trapping program using self-resetting Goodnature® A24 technology was implemented at two remote sites in Hawai`i Volcanoes National Park in an effort to protect five endangered plant species and three endangered bird species from black rat (Rattus rattus) predation. This trapping method has been successfully implemented on other islands, but implementation requirements are site specific. Techniques and maintenance schedules were investigated specifically for subalpine dry shrubland environments and also high elevation wet forest environments. Trap performance, recommended grid spacing, and a new chocolate long-life lure formula were evaluated over the course of this investigation. Apparent rodent control trends and subsequent native species responses were captured over the course of four months by conducting biweekly trap visits and analyzing motion triggered camera footage. Clear declines in rodent activity were documented at each site during the four month intensive monitoring period. At least 38 rodents were removed from the subalpine dry shrubland test site during this period, while at the high elevation wet forest site at least 102 rodents were removed. It is suspected that the number of total kills was underestimated using available monitoring techniques. Trapping activity appeared to prevent major damage to flowers and diminish damage to fruit of endangered Campanulaceae species at the forested test site, however it is unclear what effect trapping efforts had on native bird species at the subalpine shrubland site. Management recommendations differ by site. For subalpine shrubland sites, trap spacing should not exceed 100m x 100m to control M. musculus or R. rattus; tighter spacing may be necessary. In high elevation wet forests spacing traps at 50m x 50m is recommended to effectively reduce R. rattus populations. Pre-baiting traps is not advised to minimize potential damage done by rodents gnawing on depressurized traps. Concurrent trapping for feral cats and other scavengers, or strategic trapping schedules, are recommended to mitigate potential secondary predator attraction for sensitive sites such as Hawaiian petrel nesting areas. Schedule of trap maintenance should include monthly lure checks and ‘refreshment’ squeezes, regardless of site ecosystem. Scent of the lure diminishes between refreshment visits in arid environments and may be masked by algae or mold in wet environments. Use of the Goodnature® automatic lure pump should be considered to potentially alleviate this issue. In both environments standard lure bottles were found to last through the 16 week monitoring period. Lure was found to remain attractive to rodents, after refreshment squeezes as long as 36 weeks after deployment at the forested site. Trap maintenance should be scheduled to check CO2 status no later than 12 weeks after deployment, regardless of site ecosystem, to detect exhausted CO2 or malfunctioning traps, and at monthly maintenance visits if possible. Use of a surrogate pest such as a rubber rat to test fire through the trap shroud is advised to accurately simulate a strike, and ensure functionality of digital strike
Copyright held by the Cooperative National Park Resources Studies Unit, University of Hawaii at Manoa, Department of Botany.