Goldwater N.,Wildland Consultants Ltd |
Perry G.L.W.,University of Auckland |
Clout M.N.,University of Auckland
Austral Ecology | Year: 2012
Efforts to eradicate multiple mammal pests from offshore islands and fenced mainland 'habitat islands' often fail to remove mice, and such failures can result in a dramatic change in the food-web whereby the removal of larger mammal pests facilitates a population explosion of mice through predator and competitor release. We investigated the ecological responses of house mice to the removal of mammalian predators from a 500-ha fenced sanctuary at Tawharanui, northern New Zealand. Data on population structure and body condition of mice trapped in 2007, in four habitat types within the sanctuary, were compared with baseline data collected in 2001, before mammal control operations commenced. We hypothesized that: (i) in the absence of mammalian predators mouse densities would increase in all habitat types that provide vegetation cover, and (ii) in the absence of mammalian competitors mice would become heavier due to greater access to food resources. Mouse densities were significantly higher in 2007 than in 2001 in three habitat types. The high density of mice in forest - where none were trapped prior to control - suggests a competitive release, in which mice profited from the removal of ship rats. No mice were caught in the presence of ship rats on a forest trap-line at a control site outside the sanctuary. Mice trapped in 2007 were significantly heavier than those trapped in 2001, and significantly heavier than mice trapped at the control site. Greater access to food in the absence of competing and predatory mammals probably explains the heavier body weight of Tawharanui mice. There has been a significant change in the mammalian food-web at Tawharanui, such that the house mouse is now the primary pest. A rapid and dramatic increase in mouse numbers is likely to adversely impact invertebrates and seedling recruitment, which in turn could affect ecosystem functions. © 2012 The Authors. Austral Ecology © 2012 Ecological Society of Australia.
Pawson S.M.,New Zealand Forest Research Institute |
Ecroyd C.E.,New Zealand Forest Research Institute |
Seaton R.,Golder Associates |
Shaw W.B.,Wildland Consultants Ltd |
Brockerhoff E.G.,New Zealand Forest Research Institute
New Zealand Journal of Ecology | Year: 2010
The contribution of exotic plantation forests to the conservation of New Zealand's flora and fauna is a somewhat controversial issue, partly because the establishment of some plantations involved the conversion of indigenous vegetation. Such conversion no longer occurs within the professional forest industry and there is a growing appreciation of the contribution of 'production' land, including plantation forests, to the protection of New Zealand's unique indigenous biodiversity. This paper provides a comprehensive synthesis of information currently available on threatened species known to occur in New Zealand's plantation forests. Based on an evaluation of the published literature, unpublished reports, national threatened species databases, and personal observations we have compiled records of 118 species classified by the Department of Conservation as threatened that occur in plantations. Of these species, 16 are classified as 'Nationally Critical', 17 'Nationally Endangered' and 17 'Nationally Vulnerable', while the majority are classified as either in 'Gradual Decline', 'Sparse' or 'Range Restricted'. We highlight the direct and indirect benefits of plantations to various threatened taxa and draw attention to the missed conservation opportunities that are generated by a lack of understanding and the somewhat 'puritanical' views of New Zealand's mainstream conservation paradigm. We also discuss some of the potential negative consequences of plantations such as their potential function as 'population sinks' and 'ecological traps'. We conclude with a discussion of future research opportunities that aim to improve the conservation value of plantation forests. © New Zealand Ecological Society.
Renner M.A.M.,Herbarium |
Beadel S.M.,Wildland Consultants Ltd
New Zealand Journal of Botany | Year: 2011
Taeniophyllum norfolkianum is recorded for New Zealand from the Waipu Ecological District in Northland. Plants were found on twigs and branches of gorse in retired pasture reverting to indigenous forest. New Zealand plants share with Norfolk Island plants the tri-lobed labellum with prominent apical spine, but differ in their larger, bright yellow flowers, conspicuously papillate penduncle and rachis and smaller plant size. Taeniophyllum norfolkianum brings the number of epiphytic orchid species indigenous to New Zealand to nine. © 2011 The Royal Society of New Zealand.
Randall L.A.,Center for Conservation and Research |
Smith D.H.V.,Center for Conservation and Research |
Smith D.H.V.,Wildland Consultants Ltd |
Jones B.L.,Center for Conservation and Research |
And 2 more authors.
PLoS ONE | Year: 2015
A detailed understanding of the population dynamics of many amphibian species is lacking despite concerns about declining amphibian biodiversity and abundance. This paper explores temporal patterns of occupancy and underlying extinction and colonization dynamics in a regionally imperiled amphibian species, the Northern leopard frog (Lithobates pipiens) in Alberta. Our study contributes to elucidating regional occupancy dynamics at northern latitudes, where climate extremes likely have a profound effect on seasonal occupancy. The primary advantage of our study is its wide geographic scale (60,000 km2) and the use of repeat visual surveys each spring and summer from 2009-2013. We find that occupancy varied more dramatically between seasons than years, with low spring and higher summer occupancy. Between spring and summer, colonization was high and extinction low; inversely, colonization was low and extinction high over the winter. The dynamics of extinction and colonization are complex, making conservation management challenging. Our results reveal that Northern leopard frog occupancy was constant over the last five years and thus there is no evidence of decline or recovery within our study area. Changes to equilibrium occupancy are most sensitive to increasing colonization in the spring or declining extinction in the summer. Therefore, conservation and management efforts should target actions that are likely to increase spring colonization; this could be achieved through translocations or improving the quality or access to breeding habitat. Because summer occupancy is already high, it may be difficult to improve further. Nevertheless, summer extinction could be reduced by predator control, increasing water quality or hydroperiod of wetlands, or increasing the quality or quantity of summer habitat. © 2015 Randall et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Smith D.H.V.,Center for Conservation Research |
Smith D.H.V.,Wildland Consultants Ltd |
Jones B.,Center for Conservation Research |
Randall L.,Center for Conservation Research |
Prescott D.R.C.,Environment Canada
Herpetological Conservation and Biology | Year: 2014
Amphibians are declining and require improved monitoring to overcome data deficiency and to improve population estimation. To improve monitoring of two anurans in the prairie province of Alberta, Canada, we conducted repeat daytime surveys at 68 aquatic sites across 90,000 km2. We used single- and multi-season occupancy models to evaluate covariates of detection probability (p) for Northern Leopard Frogs (Lithobates pipiens) and Boreal Chorus Frogs (Pseudacris maculata). Single surveys did not perform well in any season for either species. The principal method for detecting Northern Leopard Frogs was visual sightings in summer; Boreal Chorus Frogs were best detected by their breeding calls in spring. Northern Leopard Frog’s p correlated with temperature (+) and wind (−) and was highest in summer. Boreal Chorus Frog probability of detection correlated with temperature (+), observer (−), and visual obstruction (−), and was highest in spring. Therefore, daytime surveys will be more effective for Northern Leopard Frogs in summer and for Boreal Chorus Frogs in spring. Whereas multi-species surveys often yield important information on amphibians, our study suggests species-specific surveys that quantify and maximize detection probability can improve the collection of data for conservation of threatened species. © 2014. Des Smith. All Rights Reserved.