Introduced mammalian predators, namely stoats, dogs, ferrets and cats, are the main threat to kiwi. Other threats include habitat modification/loss and motor vehicle strike, as well as the small population size and distribution of some species. New avian disease and parasites that may reach New Zealand present a further threat to kiwi populations.
Rowi killed by a stoat
In most parts of the country, stoats are responsible for approximately half of kiwi chick deaths on the mainland. Without management only 10% of kiwi chicks survive to the age of six months. Young kiwi chicks are vulnerable to stoat predation until they reach about one kilogram in weight, at which time they can usually defend themselves against stoats.
Dogs frequently kill adult kiwi and can cause catastrophic declines in local populations.
All dogs, regardless of size, breed, training or temperament are potential kiwi killers. Farm dogs, hunting dogs, visiting dogs and pet dogs are equally attracted to the strong distinctive scent of kiwi.
They may not mean to kill, but kiwi are extremely easily crushed in dog’s jaws, even if just in a playful bite. Kiwi have no sternum (breastbone), so their ribcage is very vulnerable to collapse. It is now recognised that dogs significantly reduce the life expectancy of adult Northland brown kiwi to just 14 years on average.
Read more about dogs and Northland brown kiwi
Uncontrolled, wild or abandoned cats are a threat and kill kiwi chicks. Tests with radio collars on pet cats have shown their ability to wander up to 20 kilometres from home.
Ferrets frequently kill adult kiwi.
There is a possibility of further effects on kiwi populations by introduced mammals, for example competition by rodents for similar food appears to result in delayed growth of kiwi chicks and therefore increased pressure on the overall population at some sites.
Small population size
Risks to small populations of kiwi include loss of genetic diversity, inbreeding and vulnerability to localised dramatic events such as fire, disease or predator increases. Limited dispersal and associated lowered chances of finding a mate in declining, small populations can also lead to lower reproductive rates, worsening the effect of the decline.