The issue of what biosecurity or quarantine provisions would come into
being following a rat and feral cat eradication on Great Barrier have to
be carefully considered. What has to be remembered is that this island
would become an ‘open sanctuary’ – a place where people come and go all
the time. Biosecurity measures must therefore be practical and not
unduly inconvenience people or freight movement.
Some examples of how this works in practice elsewhere:
Tawharanui Regional Park
Practical and minimizing inconvenience to visitors is how biosecurity
measures work at Tawharanui Regional Park. This 588ha park has 160,000
visitors a year and is bounded by a 2.5 km pest proof fence. Visitors
gain access through the fence by way of an electronically operated gate.
Tawharanui has a large well-used camping facility (280 person capacity)
and people are simply asked when they make their camp booking to ensure
their gear is pest free. Over summer months campers are also provided
with a mouse trap for their camp site as mice are still present on the
park. On arrival in the park (over summer) visitors are given a pamphlet
about the pest free status of the park and can attend talks by the
rangers. The park holds 1200 sheep and c. 250 cattle and stock trucks
move freely in and out of the park. While it has a pest proof fence
right across the peninsula, pests can, and do, enter through the beach
ends. Much monitoring, baiting, and trapping is done inside and outside
the fence to ensure invaders are identified and caught. Although Great
Barrier will not have a predator fence the principles of practical
biosecurity measures still apply.
Existing biosecurity measures:
A good place to start when looking at what ‘quarantine'
GBIs would need is to look at what already exists for keeping us Norway
rat, possum, hedgehog, and mustelid free. The Auckland Regional Council,
under the Auckland Regional Pest Management Strategy has a mandate for
managing Biosecurity risks
on the island. All houses coming to the island are inspected for
unwanted ‘passengers’ and smaller buildings such a sheds are to be
included in the near future. The Hauraki Gulf Controlled Area includes
Barrier for restricted access for possums, mustelids (stoats, ferrets,
weasels), deer, wallabies and feral goats. Both the carrier and the
owner of any of these species stand to cop a hefty fine if they are
caught bringing these animals into this restricted area. The ARC
reinforced the law about this by prosecuting the boaties who brought pet
ferrets to the island some years back.
Biosecurity measures are already underway at Tryphena, Whangaparapara,
and Port FitzRoy wharf environs, supported by the Auckland Regional Council,
Department of Conservation, and the Auckland City Council. The ARC
contracts the WHRBC Trust to carry out monthly monitoring for Norway
rats and stoats at Tryphena and Whangaparapara wharves while Department
of Conservation maintains stoat traps in the Port FitzRoy wharf
environs. As another partner in this Biosecurity programme Auckland City
provides bait stations which are deployed and maintained by Twomey and
Warrick around the rubbish bins at all three wharves. The objective of
this programme is to hopefully identify if a Norway rat or mustelid has
arrived – their paw prints may show in the ten monitoring tunnels at
each area – and to dispatch any such invader with the baits provided in
the area. This programme provides part time work for a local and
additional work for the local rubbish contracting business.
Practically speaking, biosecurity has to be realistic and cost
effective. Because of the size of the island only the pathways of
highest risk can be focused on – currently highest risk areas for
invasion are the island’s three main wharves which is where current
biosecurity measures are targeted.
If rats and feral cats were removed from the island, this current
biosecurity programme area would most likely be extended to other entry
points, like the Okupu wharf and the wharf at Orama, as it is the
freight and vehicle carrying boats that pose the most likelihood of
harbouring an invasive species. There have been some meetings with
Sealink to discuss this – currently the company has a private contractor
that maintains rat bait on their vessels and the Auckland Regional
Council assists with pest control around their yard environs. It would
only take the addition of rat and/or mustelid sniffing dogs to check all
cargo and vehicles on the Auckland side (including Fullers) to improve
detection. Not unlike what happens at Auckland airport with the beagles
sniffing bags and cargo. Pest-specific sniffer dogs are already used in
Private boats also pose a risk, albeit a relatively low one, of
harbouring an invader. It’s very obvious when you have a rat on board a
boat. Of the large number of private boats that visit each year, a
relatively small number actually dock, most people come in by small
craft to the wharf areas. An unnoticed rat or mustelid in such craft is
unlikely and directions for reporting such an incursion would be
publicized. Large numbers of private boats land on the beach at Tiritiri
Matangi every year, but they have never had a rat jump ship there.
The Auckland Regional Council and Department of Conservation are working
together on ideas and options for appropriate signage to the Hauraki
Gulf islands emphasizing their unique environments that need to be kept
free of unwanted pests. It advertises in local boating magazines and the
like, giving the same message.
It is considered that a pest incursion by air poses a pretty low risk,
however monitoring and baiting provisions could also be established
around the two airports. The cost of extending biosecurity
measures for Barrier should not be expensive and DOC, Auckland
Regional Council, and Auckland City would be looking at ways they can
plan for these costs in the long term.
Rats being rats we must assume that there will be incursions – it’s how
we provide for that event that is important. A single rat or two does
not mean that the whole island would need to be eradicated again. Even
if a breeding population re-established it would certainly be detected,
and could be dealt with before it spread over the whole island. The
current Open sanctuaries like Tawharanui and Tiri provide well thought
out plans for dealing with these events and there is current
research being carried out at Auckland University and Landcare Research
on the behaviour of rats when they first arrive in an environment free
of rats. So far there is early evidence that ship rats, our most likely
invader following an eradication, stay close to the place where they
land for a number of days. Practically this means that ensuring that
monitoring and control measures are established in places where rodents
are most likely to come ashore will likely be most effective. Monitoring
and control measures do not need to be in extensive grids throughout the
island nor does every property owner need to be involved. Identifying
and having measures around the areas of highest risk as stated above is
likely to be all that is required.
All mainland areas and islands that
are pest-free face
the risk of re-invasion. Ulva Island, off Stewart Island, has had
rat incursions because they can swim to it from the main island. All
incursions have been spotted through monitoring and the rats dealt with.
No rat free island out of swimming range has been re-invaded to date.
The main aim of future biosecurity measures will be for them to be as
effective as possible with minimum inconvenience to locals and visitors.
Surely, a few moments waiting while a cheeky trained dog sniffs your
gear is not too much to ask – not when the benefit to the island’s
environment would be so huge.