Survey guidelines for Australia’s threatened non-flying mammals

Central rock rat

Zyzomys pedunculatus

States and territories: Northern Territory.

Regions: Central Australia, with all recent records from the West MacDonnell Ranges (Nano 2008).

Habitat: The central rock rat occupies a range of habitats including tussock and hummock grasslands; low, open woodlands; cliffs; scree slopes; hills and valley floors. Sites are characterised by a high proportion of rock outcrop, stony soil surface and vegetation communities containing the northern cypress pine Callitris glaucophylla and the wattle Acacia macdonnelliensis (Cole & Woinarski 2000).

Habit: Ground-dwelling (possibly shelters in rock crevices).

Avg. body weight: 85 g (Cole 2000).

Activity pattern: Nocturnal.

Diet: Faecal analysis suggests the diet is predominantly plant material, dominated by seed (72 per cent of identifiable particles) and leaf (21 per cent), with slight seasonal variation (Nano et al. 2003). Stem and insects contributed 3 per cent and 4 per cent respectively (Nano et al. 2003).

Breeding: Based on observations of captive populations, litters comprise between one and four young every three months, and juveniles have been captured from wild populations in April, June, July and November (Cole 2000; Nano 2008).

Description

The central rock rat is one of five species of Zyzomys, all of which inhabit rocky regions of Australia. The central rock rat is confined to central Australia, while the other four species are found in restricted distributions across northern Australia. The central rock rat is extremely rare, and several trapping surveys have failed to detect its presence outside the West Macdonnell Ranges since it was last sighted in 1996 (the species was presumed extinct prior to this record). The range of the species is currently unknown (Cole 2000). Population monitoring following the rediscovery recorded a population boom in response to rainfall events, but the species declined dramatically as conditions became drier and a wildfire occurred in May 2002 (Nano 2008).

Very little research has been done on this species, and the biology is essentially unknown. Current threats are unclear, but suspected to be feral predators, altered fire regimes and the expansion of arid zone grazing (Cole 2000).

Survey methods

On the basis of previous surveys, the following survey techniques are recommended to detect the presence of the central rock rat in areas up to 5 hectares in size:

• 
  daytime searches for potentially suitable habitat resources such as rock and boulder outcrops, escarpments, gorges and cliffs (description of the survey technique and recommended effort is provided in Section 3.1)
  
• 
  daytime searches for signs such scats or tracks in sandy substrates surrounding rocks or in caves/overhangs (description of the survey technique and recommended effort is provided in Section 3.2)
  
• 
  collection of predator scats, owl casts or remains in predatory bird/mammal nests/dens (description of the survey technique and recommended effort is provided in Section 3.2)
  
• 
  hair sampling device surveys using a mixture of peanut butter, rolled oats and honey or sultanas conducted according to the description of the technique and the recommended effort outlined in section 3.3.7, as the central rock rat is included among those species distinguishable from hair samples (see Table 2, Section 3.3.7)
  
• 
  Elliott A trapping surveys conducted according to the technique description and recommended effort provided in Section 3.3.9. However, Zyzomys species are particularly susceptible to tail stripping when trapped, and should be handled with care to avoid this occurring
  
• 
  consultation with local people, including leaseholders, station hands, park rangers and field workers and investigating potential Indigenous knowledge of this species’ presence in an area. Consultation is particularly important for this species as it may be present at very low densities for extended periods of time during dry conditions, making it virtually impossible to detect under such conditions
  
• 
  placement of baited camera traps (same as for predator pads) in suitable habitat, which could be conducted in conjunction with hair tubes in remote locations accessed by helicopters (description of the technique is outlined in Section 3.3.6)
  
• 
  possibly spotlight surveys conducted according to the technique description and recommended effort provided in Section 3.3.3.
  

Similar species in range

The central rock rat has an allopatric distribution with other rock rat species and is unlikely to be confused with other species within the area of its known range. However, it is possible that the species may be found at other locations. Hair or tissue samples should be considered for future identification and/or molecular analysis, provided that the appropriate permission and licensing has been granted by the relevant state or territory government organisations.

References

Cole, J. 2000. "Recovery Plan for the Central Rock-rat (Zyzomys pedunculatus)". Unpublished Parks and Wildlife Commission of the Northern Territory report.

Cole. J. and Woinarski, J.C.Z. 2000. Rodents of the arid Northern Territory: conservation status and distribution. Wildlife Research 27: 437-449.
Nano, T.J., Smith, C.M. and Jeffreys, E. 2003. Investigation into the diet of the central rock-rat (Zyzomys pedunculatus). Wildlife Research, 30: 513-518.
Nano, T. 2008. Central Rock Rat Zyzomys pedunculatus, In ‘The Mammals of Australia’ (Eds. S. Van Dyck and R. Strahan) pp. 658-660. (Reed New Holland: Sydney).

Christmas Island shrew

Crocidura attenuata trichura
Regions: Christmas Island, Indian Ocean.

Habit: Unknown, probably mostly ground-dwelling, but may also be partially arboreal (Meek 2000).

Habitat: Primary rainforest with dense leaf litter cover, extending from the plateau to the shoreline (Schulz 2004).

Avg. body weight: 5.3 g (from museum specimens) (Meek 2000).

Activity pattern: Nocturnal.

Diet: Insectivorous.

Breeding: Unknown.

Description

The Christmas Island shrew is the only member of the shrew family (Soricidae) recorded in an Australian territory. The species was once common all over the island and its distinctive shrill squeaks could be heard throughout the rainforest (Lister 1888; Andrews 1900). By 1908 it was considered to probably be extinct, with no specimens either seen or heard during a visit by Andrews (1909). There have been two reports of the species since, once in 1958 and an accidental finding of two single individuals within a couple of weeks in 1985 (Meek 2000; Schulz 2004; Meek 2008). The species has not been recorded since these sightings despite targeted surveys using a range of techniques, or during extensive surveys of other fauna groups on the island. The cause of its decline is unknown and the species is regarded as probably extinct (Meek 2008). Habitat requirements critical for the species’ survival, including the provision of foraging, shelter and breeding resources, are largely unknown.

Survey methods

Based on Meek's (2000) report, further research into trap design is required to enable surveys to be conducted without the interference by crabs. In the absence of crabs, detection methods as employed by Meek (2000) would be appropriate to detect the presence of the species. The recovery plan (Schulz 2004) offers some solutions to these problems, some of which are summarised below. The surveyor should consult Appendix 1 of the recovery plan prior to conducting any survey for the species.

Two possible strategies may be considered: firstly surveying in areas where crabs are excluded, or time surveys in the future to coincide with a reduction in the population density of crabs; or secondly, focus survey effort in the canopy in response to Meek's (2000) suggestion that the species may have been displaced into the canopy by the crabs. Under these conditions, the following survey techniques are recommended to detect the presence of the Christmas Island shrew in areas up to 5 hectares in size (it should be noted that the surveyor should consult the methods detailed in Appendix 1 of the recovery plan prior to conducting any surveys, particularly in relation to site selection):

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  daytime searches for potentially suitable habitat resources such as rainforest habitats with dense leaf litter covered floors (description of the survey technique and recommended effort is outlined in Section 3.1). The recovery plan recommends spending one person hour actively searching under rocks, ground debris, at the base of trees, epiphyte clumps on trunks and in the canopy, and strips of loose bark on trunks and logs (Schulz 2004)
  
• 
  collection of predator scats, owl casts or remains, targeting predatory bird/mammal nests/dens (if they occur on the island) (description of the survey technique and recommended effort is outlined in Section 3.2). The recovery plan also recommends locating nests of birds of prey that occur on the island for collection and analysis of regurgitated and discarded material (Schulz 2004)
  
• 
  pitfall trapping surveys (description of the survey technique and recommended effort is outlined in Section 3.3.8). The recovery plan suggests establishing 10 pitfall traps at a distance of 5 metres apart (each trap 80 millimetres in diameter, minimum depth 250 millimetres). Wire mesh should be hooked into place at the top of each pit to exclude robber crabs (Schulz 2004)
  
• 
  Elliott A/E arboreal trapping surveys (description of the survey technique and recommended effort is outlined in Section 3.3.9 but needs to be modified to include Elliott A traps, or even Elliott E traps rather than the larger Elliott A traps, due to the incredibly small size of the shrew). Lines of 25 Elliot traps should be established on the ground, with an additional 10 traps in the trees (including canopy) or rock faces, preferably in proximity to epiphytes (Schulz 2004). Traps should be surrounded by tied-down mesh to allow shrew passage but to prevent robber crab interference (Schulz 2004). Traps must be checked twice daily (early morning and late afternoon)
  
• 
  at each site position 10 sheets of artificial habitat (for example, corrugated iron sheeting) and ten artificial nest burrows on the ground adjacent to the base of trees or amongst rocks, and regularly check (Schulz 2004).
  

Additional survey techniques that should be considered:

• 
  hair sampling device surveys may be a suitable alternative technique (either ground-based or arboreal as described in Section 3.3.7), as the species is included among those species known to be distinguishable from hair samples (see Table 2, Section 3.3.7). However, the technique is not recommended since tests are needed to establish that a shrew is strong enough to escape from the adhesive tape and that the device is small enough to sample hair from a shrew's back. Should such tests demonstrate that the technique is safe and effective for sampling hair from the Christmas Island shrew (or a similarly sized species), then this may be an alternative detection technique.
  
• 
  since the only recent sightings have been made by members of the public, consultation with local people and tourists, particularly park staff and field workers, is strongly recommended
  
• 
  placement of unbaited camera traps of a design that can resist the high humidity, heavy downpours and tampering by the robber crab for extended periods of time in suitable habitat may be the best technique for locating this elusive species.
  

Similar species in range

The Christmas Island shrew is unlikely to be confused with any other small mammal species on the island.

As there are very few specimens of the Christmas Island shrew, taking of hair or tissue samples should be considered for future identification and/or molecular analysis, provided the appropriate permission and licensing has been granted by the relevant state or territory government organisations.

References

Andrews, C.W. 1900. A monograph of Christmas Island (Indian Ocean): physical features and geology. (British Museum of Natural History: London).
Andrews, C.W. 1909. On the fauna of Christmas Island. Proceedings of the Zoological Society London 1909: 101-103.
Lister, J.J. 1888. On the natural history of Christmas Island in the Indian Ocean. Proceedings of the Zoological Society 1888: 512-513.
Meek, P.D. 2000. The decline and current status of the Christmas Island Shrew Crocidura attenuata trichura on Christmas Island, Indian Ocean. Australian Mammalogy 22: 43-49.
Meek, P.D. 2008. Christmas Island Shrew Crocidura attenuata trichura. In ‘The Mammals of Australia’ (Eds. S. Van Dyck and R. Strahan) pp. 418-419. (Reed New Holland: Sydney).
Schulz, M. 2004. National Recovery Plan for the Christmas Island Shrew (Crocidura attenuate trichura). The Department of the Environment and Heritage, Canberra.