Ecology of The Ngaio Weevil

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Ecology of The Ngaio Weevil
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Outcomes - The development of a low impact survey
method for rare insects on off-shore islands.
Measurement of habitat, distribution and
population of Ngaio Weevil will be undertaken,
and results publicised Survey possible locations
for the translocation of the Ngaio Weevil.
Develop a draft of an educational resource for
teaching Ecology in Year 12 Biology   Key
Learning Objectives Develop my knowledge,
understanding and skills About the latest
techniques in ecological monitoring regarding
habitats, population distributions and population
size. Develop my knowledge and understanding
of The Ngaio Weevils habitat, distribution and
population and the unique ecosystem on Stephens
Island, an ecosystem with possibly the highest
number and biomass of top level predators in the
world and home to many endemic species. The
latest techniques in management and conservation
of nationally endangered species.
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Step 1 Information Gathering - summary of
information known
Description A large, flightless weevil, about 15
- 23 mm long (Kuschel Worthy 1996). Distribution
Keepers Bush and Ruston Bush on Stephens Island
(Gibbs Allen 1990), but apparently fairly rare
there now (R. Emberson pers. comm. 1999).
Historically present in North and South
Canterbury (Worthy Holdaway 1996 Kuschel
Worthy 1996). Not seen for 17 years until 1990
(Note from Gibbs to ranger) Habitat Adults are
usually found on ngaio (Myoporum laetum) (Gibbs
Allen 1990) Sign of Presence Feeding notches on
ngaio leaves (Gibbs Allen 1990). Threats The
quantity of recently dead ngaio could be limiting
if their larvae utilise this as a food source.
Some predation from tuatara is also possible
(Gibbs Allen 1990). Work Undertaken to Date
Three weevils seen over three nights along a
limited section of the ridge track by Ruston Bush
in 1995. One of the weevils was seen on two
different evenings. Another weevil was seen in
daylight on the lower edge of Ruston Bush
prior to starting evening searches (I. Millar
pers. comm. 2000). Priority Research, Survey, and
Monitoring 1) Establish a survey technique, and
survey Stephens Island to get an estimate of
population size (R. Emberson pers. comm. 1999 I.
Millar pers. comm. 1999). Management Needs 1)
Investigate options for establishing a new
population on a rodent free island in the
Marlborough Sounds. The lack of basic knowledge
of the weevils biology and ecology may pose a
problem to translocation (Marris 1996b), and it
will depend on results of the survey because
there may be insufficient numbers to translocate
(I. Millar pers. comm. 1999). Previous sightings
Sightings of Weevil from people collated and
recorded to narrow searching
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Step 2 Stephens Island Tree planting 8-16th
August
Aims
Learn about flora and flora on the island to get
an idea about the ecosystem
Start searching Ngaio to find out what species
are eating its leaves and try to identify feeding
sign for the Ngaio Weevil
Night Searching no Weevils seen!
Survey Island for suitable habitat
Test gear
Tree planting
Start blog at www.ngaioweevil.blogspot.com
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Step 3 Initial Project planning
Reading on survey methods, similar species, any
research on Stephens Island to understand the
species there and the ecosystem as a whole
Making contact with past visitors, rangers,
scientific researchers, entomologists to get
information on similar species and sighting
locations for the Ngaio Weevil over the last 20
years
Literature survey (very little known)
Visit other islands to look for similar habitat
to that on Stephens regarding future translocation
Design Sampling method
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Step 4 Stephens Island Frog Monitoring 5-15th
September
Refine sampling method and concentrate searching
on habitat surveyed on last trip
Another chance to search for Ngaio Weevils with
warmer nights
Species monitoring
A team of 4 that can search on the way to and
from the frog bank
4 Weevils seen in 10 nights of searching
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Step 5 Final Planning
Take part in species work with Takahe on Maud
Island
Further research based on learning from frog trip
Seek advice
5.5 week Trip preparation and logistics
Meet DOC Entomologist/Technical staff
Visit islands that may be possibilities for
translocation
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Step 6 5 weeks on Stephens Island 9 Ocober-17th
November
Keep one weevil and follow it over one week to
find out about its behaviour, feeding
preferences, daytime shelter
Begin sampling all the possible tracks
400 sightings and over 200 Ngaio Weevils
individually marked
Mark-recapture study in smaller area, once a
dense population was found
Find other population areas to increase genetic
diversity for any translocation
Carry out other island tasks as required
Begin translocation proposal
Tuatara study with Victoria University
Measure time, height and diameter of tree,
temperature, weather, length and mass of weevil,
gps location, activity, host plant, height on
plant
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Step 7 Publish findings and look for
translocation site
Data entry of 20 measurements for 530 sightings
Write up report
Complete translocation proposal
Three day visit to Te Kakaho to check habitat
suitability
Email interested parties my report