J. M., LORENZO MORENO
2. Orden de 20 febrero de 2006, de la Consejería de Educación y Cultura por la que se establecen medidas relativas a la mejora de la convivencia
Rats are probably widespread at all altitudes in New Caledonian forests, but their densities were unknown. They lived in the low altitude Pare Riviere Bleue (Utocart
1 992), and I often noticed their caches of empty nut shells on the ground at Pic Ningua (above 950 m in altitude), but rarely saw them at night in forest there. The Polynesian rat has not been documented preying on kagu chicks or eggs, but it preyed on the eggs and chicks of ground-nesting seabirds (Wirtz 1 972, Booth et al. 1 996).
Ship rats (a dangerous predator of birds nests and present in New Caledonia before
1 9 1 2; Atkinson 1 985) may exclude the smaller and weaker Polynesian rat from forest at Parc Riviere Bleue as the former were only caught in forest there (Utocart 1 992).
The Norway rat R. norvegicus, present on the island (Atkinson 1 985), has not been seen in forest at the Pare (Utocart 1 992), so the ship rat may be the main potential rat predator of kagus. Some evidence suggested that ship rats might be predators of kagu
Chapter 4 148
chicks rather than their eggs (Utocart 1 992); eggs in 1 1 unprotected (no rat poison laid nearby) kagu nests at Parc Riviere Bleue were not attacked by rats, but chick survival rate increased when rat poison was laid around 1 3 kagu nests (within a 1 00 m radius of nests when incubation began and again one week before the chicks hatched). However, the large increase in kagu numbers in the Parc, mostly from nests not protected by rat poison, indicated that rat predation had not been an important factor causing kagu decline there. Rats may also compete with kagus for soil and litter prey like snails (Warner 1948).
Feral cat scats were widespread on tracks and roads over the island (ThioUay
1 989, pers. obs.). I found scats on my walking tracks in the forest at Pic Ningua up to
1 kIn from the road, confirming Fitzgerald and Karl' s ( 1 986) finding that feral cats travel some distance into unbroken tracts of dense vegetation. There has been only
one documented case of cat predation on a kagu (a one-year-old bird, section 4.3.2),
and no records of them killing chicks or mature adults. Feral cat diets worldwide mostly consist of mammalian prey when these animals are present, and this is
consistent with my inspection of cat scats at Pic Ningua which contained mostly rat or mouse Mus musculus fur. Australian feral cats took mammals up to 2 kg in
bodyweight (Paltridge et al. 1 997), therefore cats can potentially prey on adult kagus.
Feral pigs were widespread in the island' s forests (Thiollay 1 989, pers. obs.), and they caused considerable rooting damage to the forest floor in many areas (e.g., at Parc Riviere Bleue; Utocart 1 992). Feral pig rooting causes extensive damage to rainforest vegetation in Australia and Hawaii, and pigs compete with native fauna like North American turkeys Meleagris gallopavo (reviewed in Pavlov et al. 1 992).
Miller and Mullette ( 1 985) presented strong circumstantial evidence that pig predation was the major factor in the decline of the Lord Howe Island woodhen; the distributions of the two species did not overlap and remaining birds were in areas inaccessible to pigs. In New Caledonia though, kagus co-existed with pigs (e.g., at Parc Riviere Bleue and my high altitude study areas). However, eggs in two of the 26
kagu nests Utocart ( 1 992) observed at Parc Riviere Bleue from 1 986- 1 99 1 were assumed eaten by pigs based on evidence of nest damage. Along with rats, pigs may also compete with kagus by reducing their food supplies (Warner 1 948, Hay 1 986,
Chapter
4 149 Dogs were numerous throughout Grande Terre in association with human presence, and I often saw them walking unaccompanied along road margins, especially in the vicinity of human settlements. In tribal villages, dogs have become an integral part of tribal life since their introduction. Official control of stray dogs was minimal, even in the three towns (Noumea, Poya, and Pouembout) where dog registration was a requirement. When pigs became feral, and rusa deer were introduced, the use of dogs for hunting in forest also increased. The dog-related deaths of many kagus at Pic Ningua were the first direct evidence that dogs were a serious threat to the birds. This supported past observations (section 4. 1 ), and circumstantial evidence suggesting this from Parc Riviere Bleue. Management there by predator control, a halt to hunting game, and kagu introductions since 1 980 had reversed kagu decline (section 1 .2). Predator control included shooting and poisoning cats, pigs and dogs. It was difficult to pinpoint the main factor(s) responsible for the increased kagu numbers at the Parc because the management of humans, introduced predators and kagus had been carried out simultaneously. However, hunters and stray dogs had been eliminated from the Parc or were very rare there. The change in the numbers of cats and pigs there is unclear, but their presence in areas subject to poisoning and shooting (along and close to roads; Utocart 1 992) has probably been reduced (Y. Letocart pers. comm.).The lack of kagus in the northern regions of Grande Terre (Hunt 1 996a), particularly on Panie Massif, may also be circumstantial support for dogs being important kagu predators. This was because the occurrence of dogs and/or hunters with dogs may have been much greater there than in the southern parts of Grande Terre (Seitre and Seitre 1 990, pers. obs.). Local people commonly cited packs of stray and/or feral dogs as the reason for the disappearance of kagus from Panie Massif (Seitre and Seitre 1 990, Hunt 1 992). A considerable amount of other qualitative evidence also pointed to a greater dog problem in the north. I observed deer carcasses in the Tipindje River south of Hienghene that locals said resulted from these animals trying to escape packs of dogs. Men from the tribal village of Haut Coulna (on the southwest side of Mt Panie) regularly shot stray dogs in forest around their village because they killed deer (G. Bouerou pers. comm.). Also, a higher density of tribal villages exists near forest towards the north of Grande Terre, where dogs were also first introduced (section 4.4.2).
4.4.4 Conclusion
Chapter 4 150
A substantial decline in kagu numbers within potential habitats has occurred since European settlement in New Caledonia, for example in selectively logged forests. The effect of Melanesian presence, other than habitat destruction, on the distribution of kagus before Europeans arrived is largely unknown. Although the data were few and mainly circumstantial and/or negative evidence, they suggested that kagu decline since 1 853 was related to humans and/or dogs. First, the data failed to implicate mammalian predation or competition from animals other than humans and dogs, the effects of habitat fragmentation, or habitat specialisation by birds. Second, circumstantial support for dog predation (with or without humans) was the kagu distribution pattern in 1 99 1 ; more birds in remoter areas. This pattern would be consistent with a widespread kagu distribution in forest before human arrival and subsequent greater predation on adults in areas closer to human activity. Fraser et al.
( 1 995) demonstrated in stream fish that predation can cause such population fragmentation. This process would also explain the anomalous lack of kagus in the northern regions even in large and remote tracts of forest, in association with an increased frequency of dogs and/or hunters in those areas compared to forest elsewhere. Given these two points and that dogs are dangerous predators of kagus, predation by dogs (alone and with humans) appeared to be the parsimonious explanation for kagu decline. However, one should not draw conclusions about causal agents of decline from associations (Caughley 1 994), and further research is needed to see whether rats, cats and pigs are serious resident predators of kagus.
The spacing behaviour of kagu pairs, which might reflect the nature of their food supplies (section 1 .5) and be facilitated by the kagu' s apparent ability to live for long periods without drinking water (Hunt 1 996b), may have provided protection from rapid extinction (Jeggo 1978). Most rail species have broken distributions in close association with water (Taylor 1 996), and this may have been the case for many of the flightless rail species that became extinct throughout the Pacific (Steadman 1 989 1995), including in New Caledonia (Porphyria kukwiedei Balouet and Olson 1 989, and possibly T. laJresnayanus), after animal invasions. Clumped distributions near water may have made many rail species more vulnerable. A similar set of circumstances to those of the kagu may have enabled the brown kiwi to persist in a relatively widespread distribution in Northland, New Zealand. The recent arrival of ferrets Mustela Jura, dangerous introduced predators of kiwis and resident in forest (McLennan et al. 1 996), in southern Northland may have caused the apparently recent large reduction in brown kiwi numbers in that area (Miller and Pierce 1 995).