A couple of weeks ago I wrote to L\Kiwi seeking information about pigs as predators of kiwi eggs or chicks. Thanks to those who provided examples - here is my summary of the feedback I received:
Pigs have a surprisingly low impact on kiwi life history compared to stoats and dogs, although they are capable of atching mobile prey. For example Paul Jansen saw a pig predate a weka on D’urville Island: the adult weka was darting in and out while a feral pig was rooting, the pig snapped the weka, ate it, and carried on rooting. Predation of kiwi by pigs seems to be confined to isolated incidents though, and is not an inevitable outcome of pigs living in close proximity of kiwi. For example, on a number of occasions Tommy Herbert has observed fresh pig tracks passing within inches of a kiwi nest that was ultimately successful. There are a small number of examples where pigs may have impacted directly on kiwi or their nests; however it is not always clear whether a pig has killed a kiwi or whether it is scavenging a carcass that was already dead.
Nests disturbed or destroyed - There are 2 records of pigs disturbing nests at Tongariro Forest (nesting attempts database): in one case the incubating kiwi abandoned when the nest was preyed upon by a pig. The egg was found intact, in the open. In the second case, it was not known whether there were 1 or 2 eggs in the nest. Pig predation was observed, and shell fragments were found in the nest after the event.
- A monitored nest was dug up by a pig at Waikaremoana; the pig ate the egg but the associated adult male survived.
Young kiwi killed or scavenged- One juvenile kiwi released in Waimarino was predated or scavenged by a pig at 6 months old. The autopsy showed no additional signs of predation apart from pig.
- There is a single record of a young kiwi being predated by a pig in Huia, the wildlife mortality database. This bird was from Tongariro Forest in 1999. Predation is usually under-recorded in the database because these animals don’t always make it for post mortem exam.
Adults killed or scavenged - One radio-tagged adult was killed or scavenged by a pig at Waikaremoana.
There are some indirect but serious consequences that pig populations can have on kiwi. For example, pigs tipped Fenn boxes over at Waikaremoana (targeting the egg baits) and exposed the traps to kiwi, resulting in one fatality. This problem was subsequently managed by having bases on the tunnels. Several respondents highlighted the fact that pig populations attract hunters with dogs, which are in turn a serious predator of kiwi. In this sense, pigs and dogs are a “package deal” that kiwi could do without.
Regards,
Paul Gasson
