KAIMANAWA FERAL HORSES AND THEIR ENVIRONMENTAL IMPACTS

• Published in: New Zealand journal of ecology 1991-01, Vol.15 (1), p.49-64
• Main Author: ROGERS, G.M.
• Format: Article
• Language: English
• Subjects: Animal population density; Animal, plant and microbial ecology; Applied ecology; Biological and medical sciences; Endangered plants; Fertility; Forest habitats; Fundamental and applied biological sciences. Psychology; Grassland animals; Grazing; Horses; Permanent grasslands; Plants; Population ecology; Tillers; Tussock grasslands; Vegetation; Wild horses; Woodland grasslands
• ISSN: 0110-6465; 1177-7788; 1177-7788

Feral horses (Equus caballus L.) occupy 64 000 ha of montane-subalpine tussock grassland in the south-western Kaimanawa Mountains, an area zoned for military training. Since 1979, the population has increased at 16.7% per annum, reaching 1102 in 1990. The most extensive habitat, red tussock (Chionochloa rubra) grassland, was variably affected by horses; tussocks in restricted mesic sites were heavily grazed and mostly eliminated, but those in extensive xeric grasslands showed little impact. The mixed hard tussock (Festuca novae-zelandiae)/red tussock grasslands on basin floors and plateaux, which had already been degraded by early European farming, were suffering further depletion from horse grazing. The restricted, high altitude Chionochloa pallens tussock communities were being eliminated rapidly through preferential grazing. Oligotrophic bogs, on the summits and basin floors were largely intact, whereas high nutrient flushes were severely affected by trampling and grazing. Horses appeared to have had little impact upon Nothofagus forest understoreys. Ten plant species, several of which are vulnerable nationally, occur in the North Island only within the wild horse range. The habitats of five of them were damaged by horses. Throughout the wide basins and plateaux of the north, horses compromised floristic, rare plant habitat, and landscape nature conservation values. Their numbers may therefore have to be controlled.