Abstract

The Okarito brown kiwi (Apteryx mantelli “Okarito”) is a unique population (subspecies) of kiwi limited to the Okarito forest, southern Westland, South Island, New Zealand. A retrospective review of field notes over a 9-year period, from 10 March 1994 through 8 May 2002, identified 58 kiwi with ocular lesions in one or both eyes out of a monitored population of approximately 160 birds. The nature of ocular abnormalities in this subspecies of kiwi was characterized by clinical ophthalmic examination with refraction of 11 free-ranging and four captive Okarito brown kiwi from 17 June through 21 June 2002. All adults were of unknown age, though minimal ages of 4–20 years were known. Juvenile birds were considered to be less than 4 years of age. All (four) juveniles and three adults had normal eye exams. Ocular abnormalities (n=eyes affected) included: buphthalmia (1), phthisis bulbi (2), corneal edema (4), corneal vascularization (2), nuclear sclerosis (8), cataracts (11), subluxated and luxated cataractous lenses (3) and vitreal opacity (1). Three birds in good physical condition had chronic ocular lesions associated with severe visual dysfunction. A high frequency of ocular lesions exists in this discreet population of kiwi. The nature and frequency of ocular lesions are suggestive of this population being aged. This is also compatible with a population model with a high incidence of chick and juvenile mortality associated with predation by introduced mammals. Studies have been initiated to investigate the impact of visual dysfunction on breeding success.