Bridgman L.J.,University of Waikato |
Innes J.,Landcare Research |
Gillies C.,Science and Capability Group |
Fitzgerald N.B.,Landcare Research |
And 2 more authors.
Animal Behaviour | Year: 2013
Control operations for invasive ship rats, Rattus rattus, in New Zealand forests are often followed by increased house mouse, Mus musculus, detections suggesting rats suppress mice. A potential mechanism is intraguild predation, either by interference competition or as simple predatory behaviour. If aggression by rats towards mice is mainly competitive, it should include threat and display features associated with, for example, intraspecific fighting. If predatory, it should lack these features and be associated with feeding. In the first of two captive experiments we observed interactions between paired, live rodents, either side of a wire-mesh screen, and found that most rats were aggressive to mice. This aggression lacked threat and display characteristics typical of encounters with conspecifics and was rarely reciprocated by mice. In a second experiment, euthanized mice were drawn by a line through cages occupied by rats fed either a restricted or unrestricted diet. Rats of both groups attacked and restrained the euthanized mice, and all rats that interacted with the mice ate at least part of them, although food-restricted rats tended to eat more. As the aggressive response of ship rats towards mice lacked threat and display features and was related to feeding, we conclude that it resembles predatory behaviour. Our findings provide a better understanding of the interactions between ship rats and house mice, which hinder their management where they coexist as damaging invaders. However, further research is required to determine whether the results of our captive experiments are consistent with wild rat behaviour. © 2013 The Association for the Study of Animal Behaviour.
Veltman C.J.,Landcare Research |
Westbrooke I.M.,Science and Capability Group |
Powlesland R.G.,Science and Capability Group |
Greene T.C.,Science and Capability Group
New Zealand Journal of Ecology | Year: 2014
Ongoing investigations into bird mortality caused by aerial 1080 poison operations to suppress pest populations will be required because the operational specifications continually change and improve. We summarise recent studies of bird deaths following 1080 operations and present six principles for use in prioritising future research into poison risk for bird populations. A decision tree and supporting flow diagram show how the need for new surveys can be evaluated using these principles. Iterative reporting of surveys and use of the six principles to prioritise new work will enable bird mortality risks to be continually updated in an evidence-base for conservation. © New Zealand Ecological Society.
Jarvie S.,University of Otago |
Jarvie S.,Science and Capability Group |
Monks J.M.,Science and Capability Group
New Zealand Journal of Zoology | Year: 2015
There are few effective or efficient established methods for monitoring cryptic herpetofauna. Footprint tracking tunnels are routinely used to index small mammal populations, but also have potential for monitoring herpetofauna. We evaluated the utility of tracking tunnels for identification of New Zealand lizards using captive- and wild-sourced animals (four skink and eight gecko species). All skink prints that we obtained were indistinct or obscure, but we obtained relatively clear, measurable prints for all gecko species. We found that identification to species level was possible for the two gecko species for which we had a large sample - Naultinus gemmeus and Woodworthia Otago large - using linear discriminant analysis (the best model correctly assigned 96.1% of individuals). Our findings suggest that footprints from tracking tunnels may be used to distinguish between species of geckos. Additional research is needed to assess the ability to further discriminate intra- and inter-genera lizard footprints from tracking tunnels, and the utility of the technique for surveying and monitoring lizard populations. © 2014 © 2014 The Royal Society of New Zealand.
O'Donnell C.F.J.,Science and Capability Group |
Kay Clapperton B.,56 Margaret Ave |
Monks J.M.,Science and Capability Group
New Zealand Journal of Ecology | Year: 2015
The impacts of introduced mammalian predators on the viability of bird populations in forest, river and coastal habitats in New Zealand are well known. However, a common understanding of their impacts in freshwater wetlands is lacking. We review evidence for impacts of introduced mammalian predators on freshwater birds, particularly specialist species restricted to wetlands, and use this information to make predictions about freshwater species likely to be vulnerable to predation. Extinctions and significant declines of freshwater species have been numerous since humans introduced mammalian predators to New Zealand. Anecdotal evidence links predation to the loss of 11 of 14 extinct birds that would have inhabited wetlands. Thirty extant species, particularly ground-nesting species, are still under threat from mammalian predators. All introduced mammalian predator species are abundant and/or widespread in New Zealand wetlands and most have been confirmed to prey upon freshwater bird species. While their precise impacts on the long-term viability of threatened bird populations have not been evaluated, evidence suggests that predation is a serious threat, warranting predator control. An evaluation using documented predation events and ecological traits suggests that six threatened wetland specialists are at high risk of predation: Australasian bittern (Botaurus poiciloptilus), banded rail (Gallirallus philippensis), brown teal (Anas chlorotis), fernbird (Bowdleria punctata), marsh crake (Porzana pusilla), and spotless crake (P. tabuensis). Research is needed on the ecology and behaviour of mammalian predators in wetlands to help understand their impacts on long-term viability of bird populations and to assist in developing and monitoring predator control programmes. © New Zealand Ecological Society.
Buxton R.T.,University of Otago |
Jones C.,Landcare Research |
Moller H.,Science and Capability Group |
Towns D.R.,University of Otago |
Towns D.R.,Auckland University of Technology
Conservation Biology | Year: 2014
Eradication of introduced mammalian predators from islands has become increasingly common, with over 800 successful projects around the world. Historically, introduced predators extirpated or reduced the size of many seabird populations, changing the dynamics of entire island ecosystems. Although the primary outcome of many eradication projects is the restoration of affected seabird populations, natural population responses are rarely documented and mechanisms are poorly understood. We used a generic model of seabird colony growth to identify key predictor variables relevant to recovery or recolonization. We used generalized linear mixed models to test the importance of these variables in driving seabird population responses after predator eradication on islands around New Zealand. The most influential variable affecting recolonization of seabirds around New Zealand was the distance to a source population, with few cases of recolonization without a source population ≤25 km away. Colony growth was most affected by metapopulation status; there was little colony growth in species with a declining status. These characteristics may facilitate the prioritization of newly predator-free islands for active management. Although we found some evidence documenting natural recovery, generally this topic was understudied. Our results suggest that in order to guide management strategies, more effort should be allocated to monitoring wildlife response after eradication. © 2014 Society for Conservation Biology.
Monks J.M.,Science and Capability Group |
Monks A.,Landcare Research |
Towns D.R.,Science and Capability Group
Biological Invasions | Year: 2014
Many conservation decisions rely on the assumption that multiple populations will respond similarly to management. However, few attempts have been made to evaluate indicators of population trends (i.e. population indicator species). Eradication of introduced mammals from offshore islands is a commonly used management technique for conservation of native taxa in New Zealand. Pacific rats and rabbits were eradicated from Korapuki Island in 1986/1987 enabling population recovery of native species that had been suppressed by predation or competition. However, the degree to which species' responses were correlated has not been evaluated. We investigated correlations among lizard population trends on Korapuki Island as a test of the population indicator species concept. Our dataset consisted of captures of the five resident lizard species (three skinks, two geckos) from biannual pitfall trapping over a 10 year period (1986-1995) immediately following rodent eradication. We used a Bayesian modelling approach to examine correlations in population trends (based on mean annual counts) between species. Population trends were positively correlated for all species pairs (substantively for 90 % of pairs) and we detected no negative correlations. Systematic searches for single lizard species may indicate correlated recovery of lizard populations following rodent eradication and provide a cost-effective alternative to traditional 'whole community' monitoring. Our findings support evidence-based use of the population indicator species concept in cases where a shared ecological driver can be identified. © 2013 Springer Science+Business Media Dordrecht.
Buxton R.,University of Otago |
Buxton R.,Colorado State University |
Taylor G.,Science and Capability Group |
Jones C.,Landcare Research |
And 4 more authors.
New Zealand Journal of Ecology | Year: 2016
The size and distribution of colonies of burrow-nesting petrels is thought to be limited partly by the availability of suitable breeding habitat and partly by predation. Historically, the availability of safe nesting habitat was restricted in New Zealand, due to the introduction of rats by humans. More recently, however, habitat has been restored by rat eradication. Petrel colony growth is mediated by both positive and negative density dependence, although it is unclear if, or how, density dependence will affect patterns in post-eradication colony recovery. Here, using burrow density as a proxy for relative abundance, we tested whether petrel colonies increase in density or area after rat eradication by sampling along a chronosequence of (1) five islands from which rats were eliminated 1 to 26 years ago, (2) two islands that never had rats, and (3) an island with rats still present, while controlling for habitat availability. We also measured a time series of burrow densities in plots on each island to compare temporal changes after rat eradication. Using Bayesian hierarchical modelling, after controlling for nesting habitat, we found that mean burrow density increased with time since rat eradication. Burrows remained clustered (i.e. spatially structured), but became more randomly distributed on islands with more time since eradication. Point density mapping indicated that colony extent increased with time since rat eradication, with colonies filling over 70% of surveyed areas on islands by 25 years after eradication. Increases in burrow density and colony area, but maintenance of clustered distribution, suggest both positive and negative density dependence may operate during colony expansion. Understanding patterns in petrel colony recovery is important, not only due to the indispensable role of petrels as island ecosystem engineers, reflecting the recovery of ecosystem functioning, but also to help guide post-eradication monitoring strategies. © New Zealand Ecological Society.
de Lange P.J.,Science and Capability Group
PhytoKeys | Year: 2014
A revision of the New Zealand Kunzea ericoides complex is presented. This paper is the final of a series that has explored the systematics of the New Zealand Kunzea complex using cytological and molecular variation, as well as experimental hybridisations between postulated segregates. As a result of those studies ten species, all endemic to New Zealand, are recognised; seven of these are new. One species, K. triregensis sp. nov., is endemic to the Three Kings Islands and another species K. sinclairii, endemic to Aotea (Great Barrier Island). The North Island of New Zealand has seven species, K. amathicola sp. nov., K. salterae sp. nov., K. serotina sp. nov., K. robusta sp. nov., K. tenuicaulis sp. nov., K. toelkenii sp. nov., and K. linearis comb. nov. Of these, K. linearis, K. salterae, K. tenuicaulis and K. toelkenii are endemic to the North Island, and K. amathicola, K. robusta and K. serotina extend to the South Island which also supports one endemic, K. ericoides. Typifications are published for Leptospermum ericoides A.Rich., L. ericoides var. linearis Kirk, L. ericoides var. microflorum G.Simps., L. ericoides var. pubescens Kirk, and L. sinclairii Kirk, names here all referred to Kunzea. The ecology, conservation, extent of natural hybridisation and some aspects of the ethnobotany (vernacular names) of these Kunzea are also discussed. © Peter J. de Lange.
Grayson K.L.,Victoria University of Wellington |
Grayson K.L.,Virginia Commonwealth University |
Mitchell N.J.,University of Western Australia |
Monks J.M.,Science and Capability Group |
And 3 more authors.
PLoS ONE | Year: 2014
Understanding the mechanisms underlying population declines is critical for preventing the extinction of endangered populations. Positive feedbacks can hasten the process of collapse and create an 'extinction vortex,' particularly in small, isolated populations. We provide a case study of a male-biased sex ratio creating the conditions for extinction in a natural population of tuatara (Sphenodon punctatus ) on North Brother Island in the Cook Strait of New Zealand. We combine data from long term mark-recapture surveys, updated model estimates of hatchling sex ratio, and population viability modeling to measure the impacts of sex ratio skew. Results from the mark-recapture surveys show an increasing decline in the percentage of females in the adult tuatara population. Our monitoring reveals compounding impacts on female fitness through reductions in female body condition, fecundity, and survival as the male-bias in the population has increased. Additionally, we find that current nest temperatures are likely to result in more male than female hatchlings, owing to the pattern of temperature-dependent sex determination in tuatara where males hatch at warmer temperatures. Anthropogenic climate change worsens the situation for this isolated population, as projected temperature increases for New Zealand are expected to further skew the hatchling sex ratio towards males. Population viability models predict that without management intervention or an evolutionary response, the population will ultimately become entirely comprised of males and functionally extinct. Our study demonstrates that sex ratio bias can be an underappreciated threat to population viability, particularly in populations of long-lived organisms that appear numerically stable. © 2014 Grayson et al.
Chilvers B.L.,Science and Capability Group |
Dobbins M.L.,Southern Islands Area Office |
Edmonds H.K.,Te Anau Area Office
New Zealand Journal of Zoology | Year: 2015
Yellow-eyed penguins (hoiho, Megadyptes antipodes) are a Nationally Vulnerable species, restricted in distribution to the lower South Island, Stewart Island/Rakiura, and the New Zealand sub-Antarctic islands. The foraging behaviour of penguins is considered an indicator of marine ecosystems because when breeding they rely on the availability of prey close to their nests. Time-depth recorders were attached to eight nesting hoiho at Port Pegasus/Pikihatiti, Stewart Island. While at sea, hoiho spent 55% of their time diving in water > 3 m deep. Their mean dive depth was 61 ± 6.1 m with mean dive duration 2 ± 0.1 min. Based on bathymetric charts, hoiho could undertake these dives < 10 km from their nesting sites. There was significant variability in hoiho foraging behaviour within New Zealand depending on bathymetry and anthropogenic impacts. Understanding hoiho foraging behaviours could help to determine to what extent they impact on this species' life history and its role as an ecosystem indicator. © 2014 © 2014 The Royal Society of New Zealand.