COMPETENCIAS EN EL AULA
5. Inconvenientes de la metodología por Pro yectos.
reserve design is the risk of exposing kiwi to increased predation. For this reason
bush corridors and "stepping stones" should be kept as large as possible.
8.3.3 Reserve management
Good reserve design will lessen but rarely eliminate the need for management
(Gilbert
1980).
Management of a species can operate indirectly by manipulation ofthe h abitat and environment, or directly by manipulation of the population .
Population management i s discussed i n the next section
(8.3 .4),
while this sectionconcentrates on the management of the local environment. In particular, the effects
cattle h ave on the quality of kiwi habitat and the effects of mammalian predators on kiwi survival and recruitment are discussed.
Cattle in reserves
The land now comprising Paerata has been grazed almost continuously by cattle during the past
40-50
years. During my study the reserve was grazed in two blocks . The larger1 6 1
ha block was stocked with90
head of cattle, w hile the smaller40
ha block contained25
cattle. Does the high density of kiwi in Paerata i ndicate that grazing and kiwi are compatible? Certainly some local landowners h ave argued this. An opposing view has been that wildlife reserves should be totally closed to cattle.The solution to this problem was not a primary aim of this study, yet the issue is an important one. Kiwi are able to make use of a wide range of habitat types. Kiwi h ave made use of modified habitats such as exotic plantations (e.g. Waitangi S tate Forest) and pasture (e. g. Paerata) but in these situations they have also had access to substantial areas of native bush, scrub, or swamp refuges. These refuges are a n important element in kiwi h abitat that must be protected. Kiwi may be adversely affected where herbivores such as goats, possums or cattle remove the dense vegetation that can serve as daytime refuges for them. In addition to removing potential roost sites by grazing and trampling, overgrazing can reduce regeneration and threaten the long telm integrity of the forest. Kiwi are extremely sensitive around their nests, and it was impossible to know whether disturbance by cattle contributed to the high rate of nest desertion observed in Paerata. Cattle may destroy shallow burrows and possibly crush kiwi inside. No kiwi were known to
1 1 3 h ave died this way during my study, but one nest and the egg it contained were found crushed by cattle one week after the incubating male h ad abandoned the site.
In contrast, there were two ways in which cattle may have been beneficial in Paerata. First, Paerata kiwi spent disproportionately long periods in open bush and near bush edges and less time in thick bush when foraging at night than expected from the relative abundance of these habitat types (S ection 3.3.3). If this reflected food abundance then grazing may have improved this resource within the reserve. S econd, Paerata contained substantial areas of grassland. The immediate removal of c attle would probably result in the grass growing long and rank inhibiting forest regeneration. More research is needed to determine the beneficial and deleterious effects of cattle and grazing on
ki wi
and reserves.Predators
Few kiwi eggs appear to be lost to predators, except perhaps where the kiwi' s range overlaps with that o f the weka (Sec tion 6.4.2). None of the attended eggs observ e d here, and only 5% of those in Hawkes B ay (McLennan 1 9 8 8 ) , were definitely taken by predators. Adult kiwi are large and aggressive, and can probably
defend themselves and their nests against most of the introduced predators.
A
notable exception is the dog. In 1987 a single dog destroyed as many as 500 kiwi in Waitangi S tate Forest in little more than six weeks (Taborsky 1 988a,b; Diamond 1989). It was chance that Taborsky ' s study, involving telemetry, was in progress at the time and record e d the incident. The s i m i l ar des truction of other kiwi populations have no doubt gone unnoticed. Dogs pose a major threat to kiwi, and kiwi reserves should be strictly closed to them.
Juvenile kiwi are probably most at risk from introduced predators. Like adults they are vulnerable to dogs. In addition to this, u ntil they reach sexual maturity (about 2 years old) they are within the size of prey commonly taken by feral cats
(Fitzgerald & Karl 1979), and are also probably taken by mustelids. The annual
fledging rate is extremely low in both Paerata (0.3 chicks/pair/year) (Section 6.3.8) and Hawkes Bay (0.5 chicks/pair/year) (McLennan 1 9 8 8). Therefore even low rates of pred ation among j u ve nile kiwi are likely to h av e devas tating effects on recruitment. Adults may live for 20 years or more, so there could be a considerable time-lag before the loss of recruitment became obvious.
Regular (at least annual) predator monitoring and control programmes need to be instigated in prime kiwi habitats and once every two to four years populations should be surveyed to provide an indication of population trends.
1 14
8.3.4 Population management