Nine hundred kiwis and a dog

1989/06/01 Elhuyar Zientzia Iturria: Elhuyar aldizkaria

• Ekologia

Introduced predators are believed to be the main cause of the disappearance of island species. The current literature on this problem did not provide a direct but indirect solution. Therefore, the recent conflict that has occurred between a dog and a kiwi population is going to be an inescapable reality in conservation literature.

New Zealand has lost a large proportion of its species of birds of origin, after the arrival of centuries European. Sympathizers, cats and introduced dogs have been responsible for this, but there has been no concrete evidence, only suspicions. Kiwi, the national bird of New Zealand, has just responded.

He has lived in the forest called Waitangi, the largest common kiwi population in New Zealand (Apteryx australis). Between June and October 1987, biologists marked some specimens of this population and subsequently followed them with radio transmitters.

Common kiwi.

On August 24, 1987, a large female kiwi was found dead. In the next six weeks, other deaths and/or new bones were found. Of the 23 birds marked, 13 died during this period and were located thanks to the radio transmitters. Despite the difficulty of finding unmarked dead specimens, skeletons of ten other specimens were found. At the end of September few kiwi songs were heard and a dog trained to locate the kiwis (not die) found none.

The tooth marks found in the dead and fingers of the area showed that the killer was a dog. The dog was also unique. On September 30 they saw a German fire in the forest and was dead. Then no more kiwi disappeared.

How many kiwis did the dog kill? If he killed thirteen of the twenty-two marked figures, he would kill about 500 of 900 of the entire population, as all birds were in the same danger. The death of five hundred Kiwis in six weeks means that every night he killed twelve. The figure seems high, but since the kiwis have a penetrating smell and a louder cry, the dog had no problems detecting the prey.

This Waitang conflict shows which island species are attackable when a new predator is introduced. Kiwis evolved without mammalian predators and without defenses against dogs. In addition, by proliferating very slowly, the population of Waitang will take 8-20 years to reach the initial figures.

This episode of Waitang shows the importance of controlling introduced animals.