Introduction
On October 5, 2011, the container vessel Rena struck Astrolabe Reef in New Zealand's Bay of Plenty, carrying 1770 tonnes of heavy fuel oil and 1330 containers. Over the following week, around 350 tonnes of heavy fuel oil was released, impacting the shoreline and local wildlife.
The ensuing oil spill response was led by Maritime New Zealand (MNZ), with Wildbase (formerly the NZ Wildlife Health Centre) at Massey University leading the oiled wildlife response (OWR). Wildbase has had a contractual arrangement with MNZ for preparedness and response to oil spills impacting wildlife since 1998, including management of the National Oiled Wildlife Response Team. One of the key strengths with New Zealand's oil spill response system is the full integration of OWR within the National Oil Spill Response Contingency Plan. This meant that wildlife personnel and equipment were mobilised within hours of the Rena grounding, and a functional search and collection operation and oiled wildlife facility were up and running within 36 hours of the incident.
Rapid collection and treatment of affected wildlife is integral to a successful oiled wildlife response in order to minimise effects of the oiling. Direct effects of oil on avian wildlife include external contamination of plumage, leading to a reduction in insulation, waterproofing, buoyancy, and interfering with the ability of the bird to fly or, in the case of penguins, to propel them through the water. Ingestion or inhalation of oil through either direct exposure or via preening can lead to organ toxicity, including intestinal, renal and hepatic damage. Other impacts include anaemia, immunosuppression, and an inhibition of ovarian function. Indirect effects of oiling include food source and critical habitat contamination, and a decrease in reproductive success via secondary contamination of eggs.
Techniques for oiled wildlife response include hazing to move wildlife away from contaminated sites; pre-emptive capture to prevent wildlife from becoming oiled; and collection of oiled wildlife for rehabilitation and release, or for euthanasia.
Materials and Methods
A wildlife response capability was rapidly established, including a wildlife planning team based within the Incident Command Centre to co-ordinate an effective oiled wildlife response in concert with the overall oil-spill response. An Oiled Wildlife Facility (OWF) was set up at the local wastewater treatment plant using a combination of mobile response equipment, existing infrastructure, and the erection of temporary facilities. The OWF had the capacity to house and treat up to 500 oil-affected birds.
Wildlife field teams were formed to search and collect oiled wildlife from oil-affected mainland and island sites, including day and night operations. Live oiled birds were collected and promptly transported to the Oiled Wildlife Facility (OWF). All dead birds (both oiled and non-oiled) found by field teams during the first 7 weeks of the spill response were also collected and examined by a wildlife pathologist to ascertain the cause of death.
On admission to the OWF, a veterinarian immediately assessed all live oiled birds, including a complete physical examination and blood collection to ascertain packed cell volume (PCV) and total plasma protein (TPP). Each bird was given an individual identification using a temporary plastic leg or flipper band. Stabilisation of patients was initiated, including fluid therapy (usually oral) and decontamination of oil-affected mucous membranes using saline flushes. Birds were then placed in the contaminated bird zone, which was heated to allow hypothermic birds to regain their body temperature. This area was also well ventilated to prevent a build-up of volatile hydrocarbons. Twice-daily force feeding was initiated, first using a fish slurry, but switching to whole fish as soon as possible. Birds were also treated with twice-daily gavaged fluids at a rate of 60 ml/kg BID, and once daily oral itraconazole (10 mg/kg) for aspergillosis prophylaxis. Birds were regularly assessed to ascertain their suitability to undertake the wash procedure. The minimal criteria for wash include the correction in hydration and body temperature, adequate bodyweight, a bright and responsive demeanor, and a PCV of at least 30% (CHECK) and TPP at least 25g/L. Birds were then washed using international best practice guidelines. This includes the use of warmed water (40–41°C), softened to 3–5 grains of hardness (30–50 mg calcium carbonate/L) with 1–2% household dish washing detergent. In accordance with recommendations from various international oiled wildlife response organisations, DawnTM detergent was sourced from the USA as the preferred product in this response. Once birds went through a thorough wash and rinse process, they were moved to and housed in the post-wash stabilisation site within the non-contaminated zone of the OWF. Here, birds were fed twice daily with whole anchovies, as well as oral fluids and itraconazole as previously described. Re-establishment of feather integrity was facilitated via daily swimming in freshwater in order to stimulate birds to preen and realign feather barbules. This action is necessary to restore the waterproofing properties of the feathers. The length of swim time was progressively increased with an end goal of 100% waterproofness after a six-hour swim test. Due to the lengthy duration of the oil spill response, aviaries were constructed with inbuilt swimming pools to house birds for extended periods of time.
Birds were released once the following criteria were satisfied: the ongoing threat of further habitat contamination was deemed minimal; the habitat for release was clean; birds were bright, alert and responsive and they exhibited no other medical conditions, symptoms of illness or disease; the bird displayed normal behaviours; blood values fell within normal range for that species (NB: for little blue penguins, an acceptable PCV ranged from 38–48% and total protein 25–65 g/L); salt glands had been reactivated; body weight was within 10% of normal for the age and sex of species concerned; and their waterproofing was restored (this was assessed by the six-hour swim test with no sign of water penetration through feathers). Birds were released in the area they were collected from, using a combination of public and low-key releases, either off the beach or from boats close to shore.
New Zealand dotterels, a critically endangered endemic shorebird, were identified as being at significant risk of becoming oiled. In an attempt to mitigate this risk, a pre-emptive capture programme was instigated. Birds were caught using noose mats and individually marked with a numbered metal leg band at capture. Where possible, breeding pairs were caught together. Dotterels were initially housed indoors in ventilated plastic crates with a sand substrate and shade-cloth roof, and were force fed until they converted to self-feeding on a diet of Wombaroo Insectivore mix, minced ox-heart and live mealworms. Once self-feeding birds were shifted to purpose-build outdoor aviaries, which were designed to incorporate shade-cloth walls to limit traumatic injuries and a natural sand substrate. Aviaries were also provided with additional cage furniture and shelter. Birds were held individually and visual barriers were used to reduce aggression and stress. Food was presented in bowls in the middle of a salt-water tray to promote foot health, and an additional freshwater tray was provided for bathing and drinking. Birds were closely examined and weighed twice weekly. Release criteria included a cleaned environment for release with minimal risk of further oiling; a satisfactory clinical examination by a veterinarian; negative results for avian malaria and enteric Salmonella spp.; and an adequate body weight (> 130 grams).
Results
A total of 420 oiled live birds were collected during the entire spill response. Little blue penguins (Eudyptula minor) made up the majority of admissions with 383 live oiled birds admitted between 7th October 2011 and 17th January 2012. Additional oiled bird admissions included 6 shearwaters, 19 petrels, 5 shags and 7 other various species. At the peak of the wildlife response, 347 live oil-affected birds (excluding NZ dotterels) were in care. After treatment and rehabilitation, the first public release of penguins occurred on 22nd November, with the majority released by late December. Overall, 375 birds were released back to the wild, including 365 little blue penguins. A total of 45 birds were euthanised or died in care.
Sixty endangered New Zealand dotterels were pre-emptively captured to protect them from becoming oiled. Five birds had a degree of heavy fuel oil contamination of the feathers that required birds to be washed. About two-thirds of birds had oil contamination of the legs that was able to be resolved with alcohol wipes on capture. After being held in captivity for a median time of 49 days (range 39–61 days), 54 birds were released to the wild. Six birds developed respiratory distress and died of aspergillosis. The incidence of aspergillosis increased with length of time in captivity, and it was largely refractory to treatment with systemic and nebulised anti-fungal therapeutics.
Between 7th October and 22nd November 2011, a total of 2030 coastal and marine birds, 23 terrestrial birds, 9 unidentified birds, 17 NZ fur seals and 4 whales were found dead and were collected during the Rena wildlife response. Of these, those oiled included 1367 (67%) of coastal/marine birds; 6 (26%) of terrestrial birds; 3 (33%) of unidentified birds; 3 (18%) of NZ fur seals; and 0 (0%) of whales. It should be noted that in some cases, it was not possible to identify whether birds were oiled pre or post-mortem.
Discussion
Due to the prolonged nature of the incident and associated ongoing threat of oiling, affected wildlife were kept in captivity longer than ideal. Despite this, a 95% release rate of little blue penguins was achieved. Of the remaining oiled birds, four shags (80%) were released, but only 19% of the remaining admissions were released. Pododermatitis was the major complication associated with the rehabilitation of oiled penguins.
All oiled and rehabilitated penguins were microchipped, and a two-year post-release monitoring study is currently underway to compare the survival and breeding success of oil-treated penguins to a control group of penguins.
Captive management of NZ dotterels during this response achieved a 90% survival rate over a period of about 2 months. Deaths were solely due to respiratory aspergillosis, but intensive captive husbandry was required to switch the birds to a captive diet, to minimise traumatic injuries and to manage pododermatitis. While the captive management of shorebird species as a pre-emptive strategy to minimise the effects of oil spills carries significant costs and risks to the birds, our experience suggests it should be considered in the emergency management of high-priority species. A post-release study is currently underway to investigate dispersal and survival of released NZ dotterels, and to assess the impacts of pre-emptive capture on breeding success. This monitoring started immediately post-release, and will continue for at least two subsequent breeding seasons.