Survey guidelines for Australia’s threatened non-flying mammals

3.3Direct detection survey methods

Direct detection survey methods include techniques where target fauna are identified from a direct observation. Direct observations include detecting fauna while they are resting or active (for example, diurnal surveys and spotlight surveys), surveying species-specific distinguishing characteristics (for example, hair, tracks or photographic images), recording species-specific calls, and capture methods (for example, pitfall traps, small mammal box traps, cage traps and nest boxes). Descriptions of recognised direct survey for mammals are provided in the following paragraphs. Where appropriate, the descriptions include a review of the benefits and shortcomings obtained from the published literature.
Based on the previously reported use of the techniques and survey effort sourced from published and unpublished sources, the fauna survey guidelines reviewed (see Appendix), and consultation with experts, a recommended survey method has been devised for each technique. The recommended methods comprise details of the technique (for example, equipment and bait) and the minimum survey effort required (for example, number of traps, arrangements of traps and duration of sampling period). The recommended survey effort has been formulated for a stratified sampling design consisting of one hectare survey sites within a subject site up to 5 hectares in size, which can be used as a guide from which survey effort can be calculated for areas of different size.
Importantly, the recommended survey methods are intended to be used as a guide to indicate a minimum survey effort considered appropriate for detecting the listed mammal fauna. They are not designed to guarantee detection, with more or less survey effort likely to be needed for different species at different locations. Variables such as vegetation density, topography and locality differ enormously between the known habitats of the listed mammals; hence one survey standard is unlikely to suit all species. To overcome this, modifications to the survey standards are written into the species profiles where an increased survey effort is considered necessary, or where there is currently not enough information about the biology of the species available to recommend a standard survey method or effort. The standards are devised based on the assumption they will be used by experienced investigators.

3.3.1Diurnal or daytime searches for active fauna

Diurnal or daytime surveys are appropriate for species that are active during the day, or at dawn or dusk. Diurnal surveys are conducted to detect fauna when they are likely to be actively foraging, drinking, emerging from a shelter, resting or basking in the sun. The survey method involves searching for fauna, and may be carried out on foot, from a vehicle or from a hide, which can include the base of a tree as described for stagwatching (see Section 3.3.4).
The manner in which a diurnal survey is conducted will depend on the species and the nature of the subject site. For example, daytime surveys for the numbat are conducted from vehicles on tracks or from planes during aerial surveys (Friend & Thomas 2003). Similarly, rock wallabies, the bridled nailtail wallaby and the Barrow Island euro are sighted from vehicles, aerial surveys or from surveys conducted on foot along transects (for example, Lim et al. 1992, Wong 1994, and see species profiles). Diurnal surveys for rock wallabies are also conducted from observation points or hides. For example, an escarpment may be scanned for basking rock wallabies if the investigator’s view is clear or from a hide at a water source where kangaroos come in to drink.
Recommended standard survey method

The design and effort required to conduct an effective diurnal survey varies so greatly between studies that an overall standard has not been outlined here that is appropriate for the listed mammals. The design of the diurnal survey will be dependent on the nature of the site and the target species. If diurnal surveys are considered appropriate, then investigators should plan in advance the manner in which the survey will optimise the success of detection.

Transects or observation points should be selected in advance, taking into account the distance that would reasonably allow for an accurate sighting. For example, large-sized kangaroos and wallabies are visible at relatively great distances (for example, around 250 metres or more), if the vegetation and other habitat features (such as steep terrain or rock boulders) do not obstruct an observer’s view (CH McElroy pers. obs.). In this case, transects spaced 500 metres apart are appropriate; however, visibility is unlikely to be that good for most species at any given site. Sighting distance should therefore be tested during the habitat investigation stage of the study. Binoculars should always be used to examine the animals and distinguish between species that may be similar in appearance and overlapping in distribution.
As a guide, diurnal surveys conducted on foot should be conducted at a similar speed as that recommended for spotlight surveys (10 metres per minute; Section 3.3.3). The distance between transects can be greater than that recommended for spotlight surveys because the field of view is not limited by the beam of the spotlight. For each one hectare survey site used to representatively sample a subject site up to 5 hectares in size, one 100 metre transect (or two if the observer’s view is obstructed) should be used, with at least four survey sites required.

3.3.2Soil plots / sand trays / predator pads

Soil plots are a modified version of diurnal searches for signs of tracks (Section 3.2.4). This method facilitates the detection of footprints by preparing or laying out a soil/sand substrate on the ground (for example, a 3 metre x 1 metre plot) at locations where fauna are likely to occur. The footprints left in the substrate are then identified to species level by an experienced person (Catling et al. 1997). To maximise the success of recording fauna, it is best if plots are placed where animals are likely to be moving, such as along natural or vehicle tracks, walking tracks, underpasses, or along fauna trails/runways. Soil plots placed on vehicle tracks have been successfully used to survey large and medium-sized ground-dwelling mammals from forests across eastern New South Wales (Catling et al. 2001). The method is also appropriate for detecting small-sized species such as the listed northern hopping mouse which is rarely captured in traps (Woinarski et al. 1999). Care must be taken to ensure weeds or Phytophthora root rot are not introduced.
From their comparison of survey methods in the forests of south-east New South Wales, Catling and colleagues (1997) found that soil plots and hair tubes (Section 3.3.7) provided comparable results in terms of the number of species detected, but soil plots detected more individuals. The greater number of individuals detected in soil plots provided information about abundance and distribution of species that the hair tubes did not. A drawback of soil plot surveys is that tracks of related species cannot be distinguished (for example, small wallabies and potoroos). However, soil plots used in conjunction with hair sampling were more successful survey methods for detecting potoroos than cage traps or spotlighting, which respectively recorded no captures and only one sighting (Catling et al. 1997).
A specialised form of soil plot has been used to detect the presence of predators in an area by luring them to bait placed in the centre of a cleared sand pad (or plot). For example, researchers trying to detect the presence of the kowari in the gibber deserts of South Australia clear circular sized pads (3 metre diameter) of gibbers and rake the sand smooth (Brandle et al. 2002) (see species profiles). A stone covered in tuna oil is placed in the centre of the pad to attract predators to the scent. In this way, predators (for example, the kowari, wild dogs or foxes), are lured to the bait overnight, leaving their footprints in the sand, which are subsequently identified by experienced personnel in the morning.
Recommended survey method

The recommended survey method for soil plots has been based on that described by Catling and colleagues (2001). Using a stratified sampling design of one hectare survey sites within a subject site up to 5 hectares in size, at least three sites should include a soil plot survey as follows:

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  establish at least two one metre wide soil plots (raked substrate with fine grain sand added if required) across vehicle tracks, animal pads or other suitable areas (for example, underpasses under roads) per survey site
  
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  set soil plots for three consecutive nights
  
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  rake plots smooth each morning after the tracks have been identified and recorded, taking plaster casts or photographs of prints that cannot be distinguished in the field (provide a scale for all photographs)
  
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  ensure that the investigator is capable of accurately distinguishing species tracks (for example, demonstrated experience) and is familiar with the tracks of the target fauna, and
  
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  consider having a cast of the target species tracks made from museum specimens in advance to help distinguish tracks in the field by comparing against the cast (S Ingleby pers. comm.).