Although there are no snakes or dangerous wild animals in New Zealand, you should be aware of the following:
Variable Weather - Weather conditions in New Zealand alpine areas can change rapidly. Be prepared for cold wet weather, whatever the time of year.
Sand flies - In wetter areas, particularly in Fiordland, sand flies can be pests, but are effectively controlled by use of an insect repellent.
Giardia - Giardia is a water-borne parasite that causes diarrhoea. To avoid contracting it, it is best not to drink water from lakes, ponds or rivers without first boiling, chemically treating or filtering it.
Sunburn - New Zealand's clear, unpolluted atmosphere and relatively low latitudes produce sunlight stronger than much of Europe or North America, so be prepared to wear hats and sun block if you plan to be out in the sun for more than 15 - 20 minutes.