Lagomorph and sheep effects on vegetation growth in dry and mesic grasslands in Otago, New Zealand

摘要: Context. Rabbits (Oryctolagus cuniculus) are major pests in the semiarid grasslands of eastern South Island. As benefits a viral biological control agent (rabbit haemorrhagic disease virus) introduced 1997 begin to wane, landowners again faced with costs controlling rabbits. Aim. The study aimed measure extent vegetation growth as rabbit and sheep densities changed enable land managers better justify decisions on pest stock management. Methods. We investigated relationship between seasonal at two replicate sites within each three rabbit-prone areas Otago. At these sites, ambient lagomorphs varied naturally response pest-control operations, whereas density domestic (Ovis aries) according farmers’ husbandry needs. was highly degraded one studied. were present all hares (Lepus europaeus) sites. site, we established exclosures that excluded either herbivores or just sheep. observed rates modelled function prevailing herbivore densities, season site. fitted model used infer expected change biomass under varying lagomorph indices, seasons. Key results. In absence herbivores, predicted grow seasons apart from winter but presence up ~10 seen per kilometre spotlight transect, accumulation follows same pattern herbivores. counts reach 50 kilometre, accumulates only spring summer least maximum stocking for which positive could be maintained model. Conclusions. some grazed while maintaining pasture growth, even high except if rabbit-density indices exceeded ~30 kilometre. most very low maintained, below