Estimating the minimum viable population size of kaka (Nestor meridionalis), a potential surrogate species in New Zealand lowland forest

• Published in: Biological conservation Vol. 141; no. 3; pp. 681 - 691
• Main Authors: Leech, Tara J., Gormley, Andrew M., Seddon, Philip J.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01-03-2008; Kidlington, Oxford: Elsevier Science Ltd; Elsevier
• Subjects: animal reproduction; Animal, plant and microbial ecology; Applied ecology; Biological and medical sciences; Conservation, protection and management of environment and wildlife; Eglinton Valley; environmental models; Flagship species; forest ecosystems; Forestry; Fundamental and applied biological sciences. Psychology; General forest ecology; Generalities. Production, biomass. Quality of wood and forest products. General forest ecology; habitat destruction; Indicator species; life history; lowland forests; Minimum critical area; Mustelidae; Nestor meridionalis; Parks, reserves, wildlife conservation. Endangered species: population survey and restocking; parrots; population size; Population viability analysis; Predator control; predators; Psittacidae; stochastic processes; threatened species; trapping; wildlife management; New Zealand; Minimum critical area; Indicator species; Predator control; Eglinton Valley; Flagship species; Population viability analysis; Forests; Taxonomy; Diagnosis (taxonomy); Population number; Biological indicator; Vertebrata; Valley; New species; Predator; Aves; Lowland; Viability; Environmental protection
• ISSN: 0006-3207; 1873-2917
• DOI: 10.1016/j.biocon.2007.12.011

While conservation management is increasingly turning towards an ecosystem-level framework, the focus on a small subset of surrogate species has recognised merit given insufficient time, resources, and expertise. The kaka (Nestor meridionalis), a large threatened New Zealand parrot, is an iconic, visible species in lowland forests. As kaka populations are sensitive to mustelid predation and habitat loss, kaka can act as both a flagship and indicator species for healthy lowland forest ecosystems in New Zealand. To ensure the sustained protection of kaka over a sufficient area, this research aims to estimate the minimum viable population (MVP) size of kaka in the Eglinton Valley, Fiordland, and the management required for population persistence. A post-breeding census, stochastic, age structured Leslie matrix model was developed to estimate the population size having a 95% probability of persistence over 100 years. Scenarios modeling current and alternate management regimes, uncertain life-history traits, and environmental unpredictability were run. The most ‘realistic’ scenario resulted in an MVP size of 258 kaka (155 adults). Maintaining current levels of predator control appears essential to ensure kaka population persistence. An area of >500km2 is proposed to maintain the MVP of kaka based on detailed information on home range size and territory overlap derived from radio-tracking studies. As one of a group of surrogate species in lowland forest ecosystems, kaka may be used to guide management decisions regarding large-scale mustelid trapping and the delineation of habitat area requiring protection in the face of proposed human developments in the region.