Introduction

Kiwi are a group of five species of closely related ratites endemic to New Zealand. Originally thought to be a mammal by early biologists, the kiwi evolved some peculiar physical characteristics to enable its flightless and nocturnal existence. Instead of well-developed eyes like most birds, kiwi have relatively small eyes and it has been suggested that kiwi probably do not have particularly good vision. Instead, they have highly developed other senses that serve them better in the dark. The kiwi has its external nares at the tip of its long bill, which it uses to probe to find food. Although it has long been known that kiwi have a large olfactory bulb, portraying a highly developed sense of smell, it was recently discovered that kiwi also have a well-developed sensory organ in their bill tip. Mechanoreceptors sit in small pits within the bone at the tip of their bill, which allow them to sense invertebrates moving underground, and research suggests this is their primary sense for locating food. Although invertebrates make up the majority of their diet, kiwi also eat seeds, berries and leaves, and less commonly, they have been known to eat freshwater crayfish, bracket fungi and frogs. Kiwi also have a very well-developed sense of hearing, with large external auditory meatuses.

Prior to human inhabitation of New Zealand, there were no terrestrial mammals which preyed on birds, and subsequently, many of New Zealand's avian species lost their ability to fly. Instead, they could safely live on the forest floor, and kiwi roost in underground burrows during the day. Their lack of requirement for flight means they developed vestigial wings and instead of pneumatic hindlimb bones like other avian species, they have strong muscular hindlimbs. Kiwi are also reproductive oddities, with two ovaries instead of one like other birds, and a very large egg. In the brown (Apteryx mantelli), and little spotted kiwi (A. owenii), the male kiwi solely incubates the egg (usually one per clutch), which takes around 83 days to hatch. Incubation is shared between the male and female in the other species of kiwi. Kiwi chicks are precocial, relying on their yolk sac for sustenance for the first week to ten days of their life. Usually, they venture out of the burrow around day five. Chicks leave their parents' territory anywhere from age four-six weeks (brown kiwi), to a year [great spotted kiwi (A. haastii)] or up to seven years [rowi (A. rowii)]. Kiwi are long lived, with males reaching sexual maturity around 18 months and females laying their first eggs at around three years of age in captivity. In the wild, females usually lay their first eggs between three to five years of age.

Kiwi are also reported to have a lower body temperature than other birds, with a temperature between 37–38°C, compared with 39–42°C in other birds. Kiwi are sexually dimorphic, with females larger, with a longer bill, than males (Anonymous 2012).

All five species of kiwi are classified as endangered, threatened, or vulnerable to extinction. Two species, rowi and Haast tokoeka (A. australis, Haast) are critically endangered. Since the introduction of mammals by humans in the mid-1800s, it has been estimated that numbers of kiwi have declined by at least 90% in most North Island forests (Basse et al. 1999; McLennan et al. 2004). In the absence of conservation management, less than 5% of all kiwi chicks hatched reach adulthood (Basse et al. 1999; McLennan et al. 1996). This is far fewer than the 19% recruitment rate needed to maintain a stable population (Basse et al. 1999). Predation by introduced stoats (Mustela erminea) and, to a lesser extent cats (Felis catus), are the biggest threats to young kiwi (McLennan et al. 1996; Colbourne et al. 2005; Anonymous 2012). In contrast, adult kiwi exceed the prey size threshold of cats and stoats and it has been shown that juvenile kiwi are much less vulnerable to stoats when they reach a weight of 800 grams, at around four months of age (Basse et al. 1999; McLennan et al. 2004). Secondary factors contributing to overall population decline include predation of eggs by possums and other mustelids, and predation of adults by dogs and ferrets (Colbourne et al. 2005). Other contributing causes of population decline include habitat loss, iatrogenic injuries via road traffic accidents or trap injuries, and disease.

To improve the chances of recruitment of young kiwi into the population, a captive rearing programme, dubbed 'Operation Nest Egg' (ONE), was developed in 1994 (Colbourne et al. 2005). In this programme, kiwi eggs or newly hatched chicks are taken to be reared predator-free, either in a captive centre, on a predator-free island, or within mainland sanctuaries, which serve as crèches. Chicks are released back in the wild once they are large enough to survive successfully in the presence of stoats and cats (Colbourne et al. 2005). Kiwi, raised through this programme, have a 65% chance of survival to adulthood, compared with less than 5% of birds from unmanaged wild populations (Colbourne et al. 2005; Anonymous 2012). In one location, survival to 6 months of released Operation Nest Egg chicks reached 81% compared with 11% in adjacent unmanaged forest areas (Colbourne et al. 2005).

The Wildbase Hospital at Massey University treats injured or ill kiwi from all around New Zealand, and since opening in 2002, the hospital has treated more than 180 kiwi representing all five species. This study looks at the presentations and outcomes of kiwi treated at the Wildbase hospital between 2002–2009.

Materials and Methods

Data were collected and analysed from clinical records of all kiwi, which were sent to and treated at Wildbase Hospital, Massey University. Records were examined to determine the initial presentation and outcome.

Results

A total of 93 kiwi were treated at Wildbase Hospital between January 2003 and November 2009. The lowest recorded annual caseload was in 2003, where just four kiwi were treated and the highest number of kiwi treated in any one year was 25 in 2008. There was an overall steady increase in cases over the seven-year period.

Brown kiwi represent the majority of the birds treated (85/93). Representatives from each of the other four species were also treated: great spotted (2/93), little spotted (1/93), rowi (2/93), and Haast Tokoeka (2/93). Other taxa of Southern tokoeka (Fiordland, Stewart Island) were not treated at the Wildbase Hospital during this period.

The majority of the birds treated were from wild populations (41/93), followed by Operation Nest Egg (ONE) kiwi either in captivity (31/93) or crèches (11/93), then captive birds (10/93). Overall, a total of 60 (64.5%) of birds were returned to their origin after treatment. ONE birds fared best, with a 74% return rate, and 70% of captive birds were returned to their captive home. 54% (22/41) of wild birds were released back to the wild, and 17% (7/41) of wild kiwi were placed in captive homes following treatment. Overall, a total of 26% kiwi died in hospital (15/93) or were euthanised (9/41). At the time of this study, two birds were still in hospital. The number of birds returning to their origin has increased, from 25% in 2003 to a peak of 87% in 2007 (Table 1).

Table 1. Outcomes of kiwi treated at Wildbase Hospital, 2003–2009

With a total of 34/93 (37%) of cases, trauma was the most common presentation during this time period. In 12/93 (13%) cases, a diagnosis of illness was not made. Other presentations included congenital (5/93, 5%); dermatitis (5/93, 5%); parasitic (5/93, 5%); starvation (5/93, 5%); ocular disease (3/93, 3%); pneumonia (3/93, 3%); toxicity (3/93, 3%); yolk sac disease (3/93, 3%); egg related (2/93, 2%); and hardware ingestion (2/93, 2%). Other presentations made up the remaining 11/93 cases (12%).

Traumatic presentations were further divided into inciting insult as determined by the veterinarian in charge of the case, and outcomes were analysed (Table 2).

Table 2. Traumatic injuries seen in kiwi and their outcomes (Wildbase Hospital, 2003–2009)

Results

The number of sick kiwi seen at the Wildbase Hospital has steadily increased during this study period. In the subsequent three years (Jan 2010-July 2012), an additional 90 kiwi have been admitted to the centre. This is likely to be the result of an increase in awareness of the hospital, as well as the establishment of trust and confidence in the veterinary clinic and those working with kiwi in the field/captive institutes.

Traditionally, brown kiwi have been the most commonly managed birds within captivity, Operation Nest Egg, and in the wild. Increasingly, conservation management of other species through various conservation strategies has seen an increasing requirement for veterinary input into these species; however, numbers seen at Wildbase Hospital are still low. ONE of rowi, great spotted kiwi and Haast tokoeka are undertaken by institutions from the South Island of New Zealand, and these organisations usually utilise local veterinarians first, only referring cases to Wildbase (in the North Island) if necessary.

The number of birds returned to their site of origin is considered a successful outcome of treatment. In general, the number of birds with a successful outcome has steadily increased during this period. Potential reasons for this increase are twofold. A heightened awareness by conservation staff to the services offered by Wildbase Hospital, and an increase in education regarding the increased prognosis with early referral of sick kiwi, means that more birds are sent to the hospital, and sent earlier in their disease process. At the same time, veterinary staff at Wildbase have increased their expertise in treating sick kiwi, for example development of orthopaedic and blood transfusion techniques. Improvements in techniques for nutritional support, physiotherapy and other husbandry techniques have also increased the prognosis for many of our kiwi patients.

References

1.  Anonymous (2012). Kiwis for kiwi. <www.kiwisforkiwi.org>. Downloaded 3 October 2012.

2.  Basse B, McLennan JA, Wake GC. Analysis of the impact of stoats, Mustela erminea, on northern brown kiwi, Apteryx mantelli, in New Zealand. Wildlife Res. 1999;26:227–237.

3.  Colbourne RM, Bassett S, et al. The Development of Operation Nest Egg as a Tool in the Conservation Management of Kiwi. Science for Conservation Wellington, Department of Conservation. 2005;259: 24pp.

4.  McLennan JA, Dew L, Miles J, Gillingham N, Waiwai R. Size matters: predation risk and juvenile growth in North Island brown kiwi. New Zeal J Ecol. 2004;28:241–250.

5.  McLennan J, Potter M, Roberston H, Wake G, Colbourne R, Dew L, Joyce L, McCann A, Miles J, Miller P, Reid J. Role of predation in the decline of kiwi, Apteryx spp., in New Zealand. New Zeal J Ecol. 1996;20:27–35.