New Zealand: A Wildlife Extinction Hot Spot

Like the fauna and flora of the Galapagos, Hawaii and Madagascar, many of the animals and plants of New Zealand are unique. Some 85 million years ago these islands separated from the great southern continent of Gondwanaland and evolution took an independent path. In the absence of land mammals, birds and reptiles dominated the terrestrial fauna, filling ecological niches occupied elsewhere by our hairy cousins. A cooler climate and lack of mammalian predators enabled some species to become huge and flightless allowing them to exploit a wide range of climatic zones, habitats and food sources (McGlone 2009). Some, like the moas (Dinorthidae) and Haast's eagle (Harpagornis moorei) have become extinct, while others like kiwi (Apteryx spp.) and the kakapo (Strigops habroptila) are struggling to survive in the face of enormous pressure from habitat loss and a host of introduced mammalian predators. Since the arrival of humans some 750–1000 years ago, nearly half of New Zealand's vertebrate fauna has become extinct (Holdaway 2009) and, of what remains, 255 species are classified as threatened with extinction (Ministry of Environment 2007).

Kakapo: A New Zealand Icon

Once common throughout New Zealand, the kakapo was thought to be extinct until a small number of males were located in Fiordland in 1974. A second population, ultimately estimated to number 200 birds, was discovered on Stewart Island/Rakiura in 1977. This population included breeding females. Unfortunately feral cats rapidly decimated most of these birds before they were air-lifted to safety on predator-free islands (Morris, Smith 1988). In 1996 there were just 50 known birds and an intensive management program to build up the population was started in the late 1980s (Department of Conservation 1996). As a result, the population, in July 2012, stood at 126 birds.

Kakapo are in a family of their own, the Strigopidae, with no close living relatives. They are endemic to New Zealand with a collection of unique features that make them both endearing and fascinating. Anatomically they are the heaviest and only flightless parrot with a shallow keel (sternum) and markedly reduced pectoral (i.e., flight) muscles. Compensating for their lack of flight are very stout and strong feet and legs adapted to climbing, and wings and tail feathers that provide balance when clambering from branch to branch or running through the undergrowth. Their beautiful plumage of emerald green with black barring, combined with their ability to stand still for long periods, provides an extraordinarily effective camouflage within their native forest habitat. Consistent with their nocturnal habits, the birds have an owl-like facial disc and excellent hearing. A strong beak with transverse serrations on the ventral surface of the rhinotheca (upper bill), together with a fleshy tongue, enable the birds to chew and squeeze the nutrients from the leaves, fruits, seeds, grasses and other vegetation on which they live. Kakapo have a very large, pendulous crop in which to store this low protein, high fibre diet prior to digestion through their relatively simple stomach and intestinal tract.

Within the parrot order (Psittaciformes) kakapo are also unique in having a lek breeding system in which males establish a courting site in which to display and attract females. Males weigh on average 2.1 kg and females 1.45 kg, but, seasonally, weights can increase by as much as 25%. During the breeding season, (stimulated every 2–7 years by the 'masting' (fruiting) of certain trees, especially the rimu (Dacrydium cupressinum), each male clears an elevated area of vegetation to create what is called a 'track and bowl' system. Within this bowl the bird emits a low frequency 'boom' by massively inflating its cervico-cephalic air sacs. This attracts females for mating following which the female lays 2–4 eggs within a natural hole or cavity at ground level. Female kakapo are very diligent and protective mothers, incubating their eggs over a 30 day period and then feeding the chicks a diet comprised almost exclusively of rimu fruit until fledging at around 10 weeks of age (Eason et al. 2006; Jakob-Hoff, Gartrell 2012).

Conservation Management

With such a small founder base, it is not surprising that fertility and hatching success are both low. Consequently considerable efforts are made to enhance reproductive success. This has included dietary supplementation, artificial insemination, and intensive monitoring of all nest sites. A full-time, dedicated team of conservation professionals, working for the New Zealand Department of Conservation (DOC), is responsible for the management of the population including research to expand understanding of the species' biology.

During the breeding seasons each nest is closely monitored using closed circuit television signals transmitted to a 'nest minder' who camps nearby but out of sight of the nest. Chicks are warmed with small heat pads if the mother is away foraging for an excessive amount of time and all chicks are carefully examined and weighed each night while she is off the nest. Failure of the rimu fruits to mature can leave the birds with insufficient food to raise their chicks. This is the most common reason for interventions which include fostering chicks from a kakapo with multiple chicks to one with infertile eggs and hand-rearing in a dedicated facility for some or all of the rearing period. When reared in groups the birds do not imprint on people and therefore rapidly become independent once released post-weaning.

Delivery of Veterinary Services

Veterinary involvement in the health care of this free-ranging population over the last two decades has been extensive. In addition to periodic medical and surgical interventions, veterinarians have contributed their expertise to establishment of preventative health programs. These include disease surveillance, development of reference ranges for health evaluation, application of artificial insemination techniques, disease risk analysis to develop disease risk mitigation strategies, necropsy examination of dead birds, provision of advice on a range of wildlife health issues and research into clinical syndromes as they have arisen.

The successful delivery of a veterinary service in support of free-ranging birds resident on remote islands necessitates a close, collaborative relationship with the team of wildlife rangers responsible for their care. This team is knowledgeable and skilled in monitoring and handling these birds as well as being adept in the field techniques required for collection of diagnostic samples and working in the physically demanding terrain in which the birds live. To provide a service throughout the year, it has also been important to create and maintain a collaborative network of veterinarians with the necessary expertise in avian medicine and surgery. For the past six years the New Zealand Centre for Conservation Medicine (NZCCM) at Auckland Zoo has been responsible for coordinating this service. In this role we have been exceptionally fortunate in having the active involvement and support of well qualified veterinarians based in private practice (Elles Road Veterinary Centre in Invercargill and Mt Albert Veterinary Clinic in Auckland) as well as Massey University's New Zealand Wildlife Health Centre and Wellington Zoo. Practitioners from the USA and Spain have also provided significant support from time to time.

Hospitalisation

Each kakapo carries a radio transmitter and can therefore be tracked. They are largely solitary birds and do not adapt easily to captive conditions. To minimise stress we aim to maintain unwell birds as close to their natural environment as feasible. In some cases birds can be held in naturally planted pens on the island while diagnostic samples are collected and the birds' behaviour closely monitored. Telephone and e-mail communication between the rangers and vet, supplemented by digital photographs of the patient, can go some way towards assessing the situation and providing some initial treatment. However, hospitalisation is sometimes necessary. In these cases the bird is housed in strict biosecure containment to ensure they are not exposed to pathogens that they may transfer to their island home when discharged. The hospital ward is furnished with as much natural forage as available with leafy branches to climb on, chew and hide behind. Despite this, tube feeding with an artificial diet is generally necessary to maintain hydration and body condition. As the birds normally live in a colder climate air conditioning is needed in summer to avoid possible hyperthermia.

Conditions Associated with Intensive Management

Intensive management has been extremely successful in maximising the reproductive output of the remaining kakapo. However, the result has been that many chicks that would not have survived without intervention have been successfully reared. An unintended consequence of this has been that some of these birds may be less robust than their parents. This may have contributed to the susceptibility of three young birds that died of erysipelas shortly after transfer from one island to another. This infection was traced to a reservoir in seabirds sharing the same island (Gartrell et al. 2005).

Subsequent sero-surveillance demonstrated that most kakapo had been previously exposed to the causative agent, Erysipelothrix rhusiopathiae (Moorhouse 2011, pers comm). More recently a sub-adult bird was found in an emaciated state and died shortly thereafter due to disseminated aspergillosis while another young adult succumbed to peracute salmonellosis (Jakob-Hoff, unpublished).

The hand-rearing process itself has subjected chicks to diets and a rearing environment very different to that experienced in nature. As the salvage of these chicks has generally been due, in part, to the failure of the natural rimu fruit to fully mature, it has been necessary to substitute this with a commercially available parrot-rearing feed. While this has been highly successful, most hand-raised chicks experience episodes of gut stasis, (sometimes complicated by regurgitation which may result in aspiration pneumonia) and/or an infectious enteritis which occasionally has progressed to life-threatening septicaemia.

A more recent perplexing problem has been a number of cases of exudative cloacitis affecting both young and mature birds. Unfortunately most cases have been quite advanced when first noted and secondary infections and self-trauma have made it difficult to establish the initiating cause. A trichomonad-like organism has been associated with some of these cases but this organism also appears to be a natural part of the gut flora. (Jakob-Hoff, Gartrell 2012) Further studies are underway to establish the identity and prevalence of this organism within the kakapo population.

Conclusions

Kakapo are unique New Zealanders for whom great efforts are being made to ensure a viable future. Veterinarians will continue to play an important role as members of their conservation recovery team.

References

1.  Department of Conservation 1996. Kakapo Recovery Plan 1996–2005: Threatened Species Recovery Plan. No. 21. Wellington, New Zealand: Department of Conservation.

2.  Eason D, Elliot GP, Merton DV, et al. Breeding biology of kakapo (Strigops habroptilus) on offshore island sanctuaries, 1990–2002. Notornis. 2006;53:27–36.

3.  Gartrell BD, Alley MR, Mack H, et al. Erysipelas in the critically endangered kakapo (Strigops habroptilus). Avian Pathol. 2005;34:383–387.

4.  Holdaway R. Extinctions - New Zealand extinctions since human arrival. In: Te Ara - the Encyclopedia of New Zealand. Updated 2-Mar-09. URL: www.TeAra.govt.nz/en/extinctions/4. 2009.

5.  Jakob-Hoff R, Gartrell B. Veterinary care of kakapo. In: Miller RE, Fowler ME, eds. Fowler's Zoo and Wild Animal Medicine, Current Therapy. Vol 7. Elsevier Saunders; 2012:304–311.

6.  McGlone M. External links and sources. In: Te Ara - The Encyclopedia of New Zealand. Updated 20-Oct-09 URL: http://www.teara.govt.nz/en/evolution-of-plants-and-animals. 2009.

7.  Ministry of Environment, Environment New Zealand Summary. Ministry for the Environment. Manatü Mö Te Taiao, Wellington, New Zealand. 2007.

8.  Morris R, Smith H. Wild South: Saving New Zealand's Endangered Birds. Auckland: TVNZ in association with Century Hutchinson NZ Ltd; 1988.