A retrospective study of native wild birds and reptiles admitted to three New Zealand wildlife hospitals due to predation by cats

AIMS

To investigate the types of wildlife affected and outcomes of hospitalisation for native wild birds and reptiles admitted to three wildlife hospitals in New Zealand following predation by cats.

METHODS

We reviewed hospital records of three wildlife hospitals (Wildbase Hospital (WBH) in Palmerston North; The Wildlife Hospital - Dunedin (DWH); and The Nest Te Kōhanga (TNTK) in Wellington) for cases of native species with a submission history or diagnosis of predation by cats over the period 2006-2022. Frequency analysis and cross-tabulation of the data were carried out using the factors wildlife hospital, animal order, species, and case outcome.

RESULTS

Native wildlife (n = 639) presented following predation by cats to the three wildlife hospitals comprised 598 (93.6%) birds from 31 species and 41 (6.4%) reptiles from eight species. The mortality rate of these patients combined was 61.8% (395/639), with the other 38.2% (244/639) being released from hospital to rehabilitation facilities, released to the wild, or, for a small number, put into permanent captive placements. The most common species of birds admitted due to predation by cats were tūī (Prosthemadera novaeseelandiae; n = 173), silvereyes (Zosterops lateralis; n = 142), sacred kingfishers (Todiramphus sanctus; n = 100) and kererū (Hemiphaga novaeseelandiae; n = 70). There was an overall trend to increasing numbers of wildlife admitted for predation by cats over the period of this review, but the different operating periods of the three hospitals should be considered. Each of the three hospitals saw a different mix of species, with Wellington's TNTK seeing the widest diversity of species affected.

CONCLUSIONS

Predation by cats was a common cause of native birds and reptiles being admitted to all three wildlife hospitals and a diversity of urban and rural wildlife were affected.

CLINICAL RELEVANCE

Predation by cats causes significant mortality in wildlife patients admitted to wildlife hospitals despite best current treatment. Cat management strategies in Aotearoa New Zealand should consider the welfare and health of wildlife.

Surgical repair of a meningoencephalocoele in a kākāpō (Strigops habroptilus)

CASE HISTORY

A kākāpō (Strigops habroptilus) chick hatched on an off-shore island of New Zealand with a small white mass protruding through the cranial skin of the head. The chick's growth followed a normal pattern for kākāpō but at 3 weeks of age the cranium mass was non-reducible and fixed in place and the chick was removed from the island for diagnostic imaging and hand-rearing.

CLINICAL FINDINGS AND TREATMENT

A computed tomography (CT) examination revealed a full-thickness circular defect in the central cranium with suspected herniation of brain and dura. Surgery was performed at 37 days of age, and the herniated dura was dissected from the open fontanelle. Attempts to reduce the herniated tissue were unsuccessful, so the herniated dura and cortex were clamped and resected. The dura was closed and the periosteum of the skull was scarified and monofilament polypropylene mesh was secured tautly over the fontanelle. The mesh graft was infused with autologous bone marrow harvested from the ulna in an attempt to stimulate osteogenesis in the mesh repair. The skin flap was then closed. Post-operative recovery and healing were without complication. A CT examination 4 weeks after surgery showed no recurrence of the hernia, and a composite of mesh and scar over the open fontanelle which had reduced in diameter. The chick was released back onto an off-shore island with a radio transmitter and it continues to be monitored regularly.

PATHOLOGICAL FINDINGS

The tissue resected at surgery consisted of a cylindrical core of cerebral parenchyma overlain by a mildly hyperplastic epidermis, and large amounts of oedematous fibrovascular tissue arising from the leptomeninges.

DIAGNOSIS

Rostral parietal meningoencephalocoele.

CLINICAL RELEVANCE

This is the first report of successful surgical resolution of a meningoencephalocoele in any bird. Techniques from human neurosurgery were adapted for the unique anatomical features of the avian skull. The risks of the procedure included increased intra-cranial pressure resulting in anaesthetic complications or death, cerebrospinal fluid leakage, meningitis or recurrence of the meningoencephalocoele. In the longer term, there was a risk of developmental deficits in cognition or behaviour. None of these complications eventuated in the short to medium term, probably due to the small size of the meningoencephalocoele.