Kagu pigs and dogs. New Caledonia lacked mammals (except for bats) before the arrival of humans, and many of its native species have been negatively affected by introduced mammals. Rats have a big impact on nestlings, accounting for 55% of nestling losses. Kagus also suffer from habitat loss caused by mining and forestry. Concern was first raised about the future of the kagu in 1904. The first concrete evidence of the impact of dogs came when a New Zealand researcher's study population was quickly exterminated by dogs in the 1990s, although suspicions about the importance of dogs and other predators had
Kagu some range contraction due to hunting and predation by introduced species. Its original, pre-human distribution, and the extent to which it and its sister species "R. orarius" coexisted in lowland areas of New Caledonia, is still not fully understood and awaits further research into the subfossil record. Kagu are territorial, maintaining year-round territories of around 10–28 hectares (22–62 acres). Within the territory the pairs are solitary during the non-breeding season, and may have separate but overlapping foraging areas. Kagus make a range of different sounds, most commonly while duetting in the morning, each duet lasting about 15 minutes. The kagu's