Glencore reintroduction project: design and methods
A risk-weighted staged approach was used to decide the number of northern hairy-nosed wombats (Lasorhinus krefftii) to translocate from Epping Forest National Park (Scientific) to the Richard Underwood Nature Refuge. It was planned to move up to 12 animals during the first year, and additional animals in the following year pending the success of the first translocation. However, it was likely that fewer than 12 suitable wombats would be trapped due to the difficulties in trapping wombats.
In determining the number of wombats to translocate, the following things were considered:
Precedent - translocation of southern hairy-nosed wombats
The southern hairy-nosed wombat (Lasiorhinus latifrons) is the closest relative of the northern hairy-nosed wombat and a member of the same genus. It is commonly used as an analogue species.
In the 1970s translocations of southern hairy-nosed wombats were undertaken by the South Australia National Parks and Wildlife Service. Ninety one wombats were translocated from one property to four different locations over three months:
|Date||Release site||Number of wombats|
|29/07/1971||Site 1||4 females|
|11/08/1971||Site 1||5 males 7 females|
|28/08/1971||Site 2||3 males 1 female|
|07/09/1971||Site 2||3 males 4 females|
|12/10/1971||Site 2||11 males 12 females|
|27/10/1971||Site 3||11 males 10 females|
|17/10/1971||Site 4||12 males 8 females|
The wild to wild translocations were successful. Animals were taken to areas where the species had become locally extinct. Limited monitoring showed that at all release sites there were active burrows after several months, and at Site 1, where a follow-up visit was carried out five months after the release, revealed that 10 wombats were still occupying burrows on the property. There were three reported deaths, including two animals that were found lying close to each other with mutilated bodies. These two wombats were most likely killed and mutilated by wild dogs (which do not occur at Epping Forest National Park (Scientific) or the Richard Underwood Nature Refuge as these sites have predator-proof fences). The third wombat was killed by a vehicle on a nearby bitumen highway. This information comes from unpublished reports.
Social behaviour of northern hairy-nosed wombats
There is limited information on the behaviour of northern hairy-nosed wombats due to their fossorial and nocturnal habits (i.e. they spend a lot of their time underground, and usually only come out at night time). Northern hairy-nosed wombats are generally solitary animals, however, they live in clusters of burrows that can be used by 4-5 wombats. Burrow sharing also occurs and usually involves females rather than male and female (Johnson 1991), and therefore the wombats live close to each other and feeding ranges overlap. There was also evidence from the trial translocation at Epping Forest National Park (Scientific) that wombats prefer to be in the presence of other wombats, which was suggested by wombats following the trail or scent of other individuals.
It is important to provide sufficient animals to help establish the social structure of the new colony. From an animal welfare perspective, an effective social structure is a positive factor in individual wellbeing.
Population dynamics - why we are not proposing to use more animals
To establish a new population of a species, it is usually necessary to ensure the founder individuals are selected based on relatedness of individuals. The northern hairy-nosed wombat population at Epping Forest National Park (Scientific) has been as low as 35 individuals, and has therefore been through a genetic bottleneck. Therefore it is not necessary to translocate a large number of wombats in order to get a sample of the species’ genetics.
Additionally, with good feeding conditions, it has been anticipated that translocated wombats would breed successfully. The breeding rate for northern hairy-nosed wombats (measured as the proportion of females breeding in any one year) correlates closely with summer rainfall (Crossman et al. 1994). This averaged 50-75% in the period 1985-89, decreased to only 20% in 1993 during a major drought, and increased slightly to 25% in 1999.
The trial translocation within Epping Forest National Park (Scientific)
In 2006 two sub-adult northern hairy-nosed wombats were translocated from the southern section to the northern section of Epping Forest National Park (Scientific). The outcomes from that trial have significantly influenced the design of the reintroduction project.
Trapping technique currently used for trapping northern hairy-nosed wombats
In some areas of Epping Forest National Park (Scientific), permanent trapping fences enclose areas of habitat that contain the entrances to burrows, with several gaps, or ‘gates’, left open to allow freedom of movement for the wombats.
Trapping involves sealing off all but one or two gates, and placing cage-tunnel traps at the open gates. Historically, traps were set at the gates with most wombat activity. Gates not trapped are temporarily closed during trapping to create a solid barrier around the burrow. Trapping fences are large enough to contain areas of wombat habitat where wombats can feed while trapping is in progress.
Wombats are trapped in walk-through cage-tunnel traps. These are activated when the wombat trips a nylon fishing line strung across the trap 50 mm above the floor. This causes doors at each end of the trap to fall down, trapping the wombat. A transmitter is activated to alert the ranger base that the trap has been set off. This allows the team to quickly respond and ensure that the captured wombat spends the least time possible in the trap. All traps are checked at dawn in case of a transmitter failure and are locked open to ensure that no captures can occur during the day.
Capture and processing of northern hairy-nosed wombats
All non-target species are immediately released from the traps after a quick health check by the team checking the traps. Only personnel experienced in wildlife handling and assessment check activated traps.
Trapped wombats are assessed by the veterinarian as being suitable to receive anaesthetic while still within the trap. Anaesthesia is closely monitored and recorded on a field anaesthetic data sheet. Anaesthetic emergency drugs are on hand and protocols are well rehearsed.
Anaesthetised wombats are processed as quickly and as close to the burrow of capture as possible. During processing, the veterinarian monitors temperature, pulse rate, respiration rate and oxygen level at least every five minutes.
For identification purposes, all new wombat captures have:
- A PIT tag implanted under the skin between the shoulder blades.
- An identification number tattooed on the ear (Right ear for males; Left ear for females).
The following samples may be collected from trapped wombats:
- Blood (up to 26 ml) from the cephalic vein for: genetics and reproductive studies; packed cell volume; serum bank to monitor for disease; complete blood count; and multiple biochemical analysis.
- Faeces (if produced) for dietary, reproductive and genetics studies.
- Skin biopsies of any lesions for disease assessment.
- Hair for genetics and aging studies.
- Ectoparasites, including skin scrapings from animals with major hair loss, to check for the presence of mites which cause sarcoptic mange.
All trapped wombats undergo a thorough health examination and are given a body condition score between 1 and 5. A score of one being very poor, three being good, and 5 being overweight.
Some wombats to be translocated have radio transmitter collars fitted around their necks to a tightness that prevents interference with the animals' normal functions. These collars are secured using bolts that are snipped and filed to ensure smooth edges. The collars are also fitted with timed release devices, designed to allow collars to be released without having to recapture the animal and are programmable to the nearest hour. Collars are fitted by experienced personnel and are checked for tightness by the attending veterinarian.
Wombats to be translocated had collars attached during the first round of trapping to provide time for the animals to habituate to wearing collars. Previous research has found that it takes from ten to eighteen days for an animal to habituate to collars, and during this period the animal displays reduced activity levels. By attaching collars prior to the animals being taken to the Richard Underwood Nature Refuge, it removes one level of stress during the reintroduction of the animal to the release site.
When processing is complete, wombats are placed in a recovery crate. Typical recovery time in the crate is 20-30 minutes, in which time they are either moved to the ranger base to prepare for transport to the translocation site, or to the burrow of capture to be released (if unsuitable for translocation). Recovering wombats are monitored by the veterinarian and must meet the following criteria before being released:
- Wombats are able to stand on their feet, and
- Wombats are orientated and making calculated movements.
If, during processing of a wombat, other wombats are located within traps, a decision is made by the veterinarian and the project manager to proceed with processing of the new animals or releasing them from the traps without processing. This decision is based upon the animal's demeanour, the time of night, the ambient temperature and the stage of processing of the first animal.
Transportation and release of northern hairy-nosed wombats to Richard Underwood Nature Refuge
Before northern hairy-wombats selected for translocation are transported, they all undergo recovery from anaesthesia in a recovery crate.
Wombats to be translocated are then transported by car to the airstrip in the vicinity of Epping Forest National Park (Scientific), transferred onto a fixed-wing aeroplane, and flown to the St George airstrip in the vicinity of the Richard Underwood Nature Refuge. Due to legal restrictions when flying it is not possible to treat animals in the air. On arrival the wombats are checked by a vet, transferred to a car and taken to the starter burrows at the release site. There is a team of staff at the Richard Underwood Nature Refuge to meet the wombats and undertake all activities at the release site.
At all times, transported wombats are kept within a temperature range of 12-28°C. This temperature range is based on burrow temperatures recorded by Jodie McGill, who studied burrow use at Epping Forest National Park (Scientific). During this study, when the temperature outside the burrow was >40°C, the temperature deep in the burrow was no hotter than 28°C, and when ground temperature was below 0°C the temperature deep in the burrow was no lower than 12°C. The maximum daily average temperature at Epping Forest National Park (Scientific) during winter is 21-24°C, which is well within the temperature range maintained within a wombat's burrow. And the average daily minimum temperature at Epping Forest National Park (Scientific) during winter is 6-9°C.
A final assessment of the wombat’s condition is made before the wombat is released down the starter burrow entrance. A barrel is used to plug the burrow entrance, ensuring the wombat will be held in the starter burrow during the daytime and the barrier removed at dusk. Temporarily holding the wombat within the burrow eliminates the risk of the wombat leaving the burrow before fully recovering from the anaesthetic and making decisions affecting its wellbeing while still under the influence of the drugs.
What is a starter burrow?
Shelter for translocated northern hairy-nosed wombats is provided in the form of 'starter burrows'. Starter burrows are drilled into the ground at a depth, width and angle known to be desirable to the wombats based on previous research on burrow architecture and the trial burrows used in the trial translocation in 2006. The provision of starter burrows is to create a secure environment from where the wombats can modify the starter burrow, or use as shelter until they dig their own burrows.
Information for the design of the starter burrow was collected from the measurements taken from four burrows on-site at Epping Forest National Park (Scientific) in June 2006, and information offered by Jodie McGill and Donna Treby (both who have researched northern hairy-nosed wombat burrow design).
Starter burrow design includes the following:
- Burrow angle: This varies markedly between different burrows constructed in different situations. The angle of about 30% has been selected to provide easy access for wombats and stability of the tunnel. Too shallow an angle would make the burrow more prone to collapsing while too steep an angle would not allow the animal the stability of footing to dig effectively.
- Burrow height and width: These were based on the dimensions of a sample of burrows – 450mm to 550mm high and 500mm to 600mm wide.
- Burrow Length: Research has shown that burrow conditions become more stable at 5 meters in length and very stable at 10 metres. The longest burrow at Epping was 90 metres in length. It was not possible to dig a burrow of 10 metres long, of the required height and width using available equipment. The starter burrows were extended as far as possible with the machinery available.
- Burrow Depth: One study of burrow architecture found the mean burrow depth to be 2.5 metres. It was not possible to achieve this depth using available equipment, but the burrows were drilled as deep as the equipment allowed.
Natural wombat burrows can be very long and are not straight, resulting in little or no light reaching the end of tunnels. Due to the lack of depth of the starter burrows, it is beneficial to have a bend in the burrow to reduce the amount of light reaching the end. To achieve this, the first hole was drilled and then a second hole was drilled perpendicular to the first. One of the holes was then backfilled to create a dark, closed end to the tunnel.
Soil and faeces are collected from the capture burrows at Epping Forest National Park (Scientific) and placed within the starter burrows and runs at Richard Underwood Nature Refuge before the wombats are released, in order to make the new burrows familiar to the northern hairy-nosed wombats.
Techniques used to monitor reintroduced northern hairy-nosed wombats
The reintroduced colony of wombats at Richard Underwood Nature Refuge is routinely monitored using the following techniques:
- Infrared monitoring cameras placed near burrows allow the daily activity and natural behaviour of the wombats to be viewed while causing minimal disturbance. The health and condition of the wombats can also be monitored through the use of monitoring cameras.
- Burrow activity is assessed regularly to determine which burrows are being actively used by the wombats and where best to place the monitoring cameras. This is done by inspecting burrow entrances and runways for signs of recent activity including fresh dung, wombat footprints and digging. Used in conjunction with the monitoring cameras, a picture can be formed of the overall wombat activity and burrow use at Richard Underwood Nature Refuge.
- In the early stages of the reintroduction, a number of wombats were fitted with radio tracking collars. These wombats were radio tracked daily to monitor their location and movement using telemetry equipment. A series of fixed telemetry stations, when manned simultaneously, allowed a wombat’s position to be triangulated and their nocturnal movements to be mapped. During the day, handheld radio tracking equipment was used to track a wombat to a particular burrow and its location recorded.