National Recovery Plan for the Christmas Island Shrew (Crocidura attenuata trichura)
Prepared by Martin Schulz for
The Department of the Environment and Heritage, 2004
ISBN 0 642 55011 5
Appendix 1 : Targeted survey
Objective: To locate extant populations of the Christmas Island Shrew.
The survey must be undertaken by a consultant with either previous field survey experience of Crocidurine shrews or extensive expertise using a wide range of survey techniques in targeted surveys for small mammal species within Australia. The consultant must have good lateral thought with the ability to use adaptive targeted survey strategies.
To be conducted for one month sample periods in both the dry and wet seasons of each year for the five-year timeframe of the Recovery Plan or until extant populations have been located and the distribution fully assessed.
Following from the survey of Meek (2000), a stratified survey across all primary plateau and terrace rainforest communities and in ecotones between these and other vegetation communities should be undertaken using a variety of additional or modified techniques.
Sites should be selected in primary plateau and terrace rainforest at 2km2 intervals across the island. All sites need to be outside of crazy ant infestations or sites treated by aerial baiting in September 2002. Initially it is recommended survey effort be concentrated on the western section of the island (west of Margaret Beaches on the north coast and South Point on the south coast), with the following areas to be investigated as high priority:
- 1985 shrew localities: plateau rainforest adjacent to the Shrine in LB4 and terrace rainforest at No 1 Dale.
- plateau rainforest linking the two 1985 localities, including Ferguson, Murray, Bean and Camp Hill areas.
- terrace rainforest between North West Point and Egeria Point.
- terrace and plateau rainforest from Jones Point east to The Blowholes.
- terrace and plateau rainforest along north coast from North West Point east to the eastern end of Margaret Beaches.
Logistically it is not feasible to obtain coverage of the entire island on each visit, both in terms of distances involved and the requirement to check traps frequently. Instead, it is recommended that a number of contiguous 2km² areas be surveyed simultaneously.
For each 2km² sector, the following land features be selected on different survey visits:
a. Coastal 2km² areas:
- Ecotone of terrace rainforest and coastal vegetation or shoreline.
- Terrace rainforest on ecotone with inland cliffs and scree slopes.
- Primary rainforest on ecotone with inland cliffs and scree slopes.
b. Inland 2km²areas:
- Primary rainforest with rock outcropping.
- Primary rainforest without rock outcropping.
The location of each site must be permanently marked and accurate coordinates recorded using a GPS to enable revisits.
Survey Timing and Duration:
Where possible, survey visits to be timed to coincide with reduced land crab activity (e.g. Robber Crab moulting period in March/April). Each site to be sampled for seven consecutive days, which is longer than normally necessary to reach asymptotes in species accumulation curves for small insectivores, such as shrews (after Goodman & Jenkins 1998).
Survey techniques typically used to detect and capture shrews are pitfall trapping and live trapping using a variety of trap designs, such as Sherman, Longworth and Elliott traps. Standard techniques are difficult to use on the island due to the problem of crab interference. All survey methods must take crab interference into consideration.
Survey techniques listed below are to be used at all standard sites selected. Additionally, the consultant must have the option to use an adaptive survey strategy trialling new techniques or modifications to the following listed techniques. Additional strategies could include the use of waterproofed infra-red video camera systems at permanent feeding stations, both on the ground and in the canopy (e.g. following the field-tested design of Ross Meggs; Faunatech, P.O. Box 1655, Bairnsdale, Victoria, 3875; firstname.lastname@example.org); automated playback that would enable sampling a number of localities simultaneously; and use of shrew pheromone from SE Asian shrews as an attractant. Where time permits, opportunistic sampling using the standard survey techniques listed below at additional locations is to be encouraged.
1. Pitfall Trapping
Pitfall trapping is a common technique for locating Crocidurine shrews in the Northern Hemisphere and Asia. Lister (1888) recorded the capture of three individuals in pitfall traps on the island, but did not specify the nature of the traps used. Meek (2000) used pitfall traplines (12 pits along a 25 m line; diameter 250 mm and 80 mm) at three sites in the Dales - Winifred Beach area. Rolls of rigid underground powerline cable cover (300 mm X 4 mm) were used as a drift fence. Segments of PVC tubing (100 mm X 40 mm) were placed at the bottom of pits to act as refuge sites for captured animals from Robber Crab predation.
Establish ten pitfall traps of PVC tubing (maximum diameter: 80mm, minimum depth: 250mm, each trap capped by heavy duty wire mesh (e.g. steel) at a distance of 5m apart with the upper rims flush with ground level. Drift fence similar to that used by Meek (2000) or utilise mobile crab fences developed by PAN (M. Jeffrey, pers. comm.). The small diameter tubing coupled with the wire mesh capping of a spacing to exclude Robber Crabs and the majority of other crabs. This wire mesh is to be hooked into place at the top of each pit. Each pitfall trap to have non-absorbent cotton wool or coconut fibre to be placed in the base to serve as shelter. Additionally, each pitfall trap to have a securely fitting lid for when pits not in use.
2. Live Trapping
Lines of twenty-five Longworth/Sherman/or finely tuned Elliott traps be established at intervals of 10m on the ground (after Haim et al. 1997), with an additional 10 traps sited in trees (including canopy) or rock faces, preferably in proximity to epiphytes. Traps to be baited with a range of baits including: rolled oats, peanut butter and sunflower seeds, as well as a presumed shrew specific mixture of ikan billis (fish) soup powder, flour and water (after Meek 2000). Each trap to be surrounded by guyed or tied-down wire mesh of sufficient mesh spacing to allow shrew passage but to prevent Robber Crab interference. To provide protection against high temperatures non-absorbent cotton wool or other insulative material must be placed in each trap. Traps must be checked twice daily (early morning and late afternoon) to minimise shrew mortality.
3. Call Playback
Earlier naturalists commented on the short shrill squeak of the shrew commonly heard throughout the island (Lister 1888, Andrews 1900). No information is provided as to the time of day or conditions when calls were heard. At each site, conduct two call playback sessions: within two hours after dawn and within two hours following dusk. Each session to consist of a thirty minute listening period, followed by a ten-minute period of playing the call of related Crocidura shrews, followed by another thirty minute listening period.
4. Active Searching
The shrew was recorded living in holes in rocks and roots of trees (Andrews 1900). At each site, spend one person hour actively searching under rocks, ground debris and at the base of trees with the aid of a rake and gemmie bar.
5. Artificial Habitat and Nest Burrows
At each site, position ten sheets of artificial habitat (such as corrugated iron sheeting) flush with the ground adjacent to the base of trees or amongst rocks. These sheets to be regularly checked.
At each site, place ten artificial nest burrows (made of two layers of PVC tubing) at the base of canopy trees, following the same design and dimensions as used for the Earless Dragon Tympanocryptis lineata pinguicolla (designed by P. Robertson, Wildlife Profiles P/L, P.O. Box 500 Heidelberg, Victoria 3084; email@example.com).
6. Hair Funnels and Hair Tubes
Shrews readily investigate novel objects and frequently defaecate on the inside of such objects (Churchfield et al. 2000). At each site, locate five hair funnels (Faunatech) and five hair tubes (following the design of Suckling 1978) 20 m apart on the ground, and five hair funnels and five hair tubes in trees (including in the canopy) or on rock faces adjacent to epiphytes. The hair funnels/hair tubes are to be baited with the same mixture as for Longworth/Elliott traps. Each trap to be surrounded by guyed or tied-down wire mesh of sufficient mesh spacing to allow shrew passage, but to prevent Robber Crab interference. These traps to be regularly checked for hairs and scats.
7. Epiphyte and Loose Bark Search
There is a possibility that the shrew uses epiphytes as shelter sites (Meek 2000). At each site, where feasible, search epiphyte clumps on the trunk and in the canopy, and strips of loose bark on trunks and logs for sheltering shrews. This search to be conducted by manual light beating of the clump/bark with the aim of disturbing sheltering shrews.
8. Predator Gut and Scat Analysis
At each site, any predator scats and regurgitations be collected for analysis after each survey period. Additionally, encourage Parks Australia North staff to retain and be trained to identify the gut contents of all feral cats killed during control programs and randomly.
Both on site and elsewhere, locate nests of the Nankeen Kestrel Falco cenchroides, Christmas Island Goshawk Accipiter fasciatus natalis and Christmas Island Hawk-Owl Ninox natalis, for the collection and analysis of regurgitated and discarded material.