See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/248902246 Scats can reveal the presence and habitat use of cryptic rock-dwelling macropods Article in Australian Journal of Zoology · January 2006 DOI: 10.1071/ZO05074 CITATIONS READS 20 209 3 authors, including: Anthony D Griffiths David M. J. S. Bowman Charles Darwin University University of Tasmania 69 PUBLICATIONS 1,878 CITATIONS 430 PUBLICATIONS 12,831 CITATIONS SEE PROFILE SEE PROFILE Some of the authors of this publication are also working on these related projects: Fire as an Earth System Process View project Fire and Man View project All content following this page was uploaded by Anthony D Griffiths on 28 April 2015. The user has requested enhancement of the downloaded file. CSIRO PUBLISHING www.publish.csiro.au/journals/ajz Australian Journal of Zoology, 2006, 54, 325–334 Scats can reveal the presence and habitat use of cryptic rock-dwelling macropods Wendy R. TelferA,B, Anthony D. GriffithsA and David M. J. S. BowmanA ASchool for Environmental Research, Charles Darwin University, Darwin, NT 0909, Australia. BCorresponding author. Email: [email protected] Abstract. The rock-dwelling macropod species of the tropics of the Northern Territory, Australia, are behaviourally elusive and difficult to observe in their rugged habitats. Hence, little is understood about their ecology. We evaluated the potential of using scats (faecal pellets) as a survey tool for this faunal assemblage by: (1) developing a key to the scats of the species; (2) examining the rates of loss and decomposition of short-eared rock-wallaby (Petrogale brachyotis) scats in these tropical environments; and (3) comparing the distribution of scats of P. brachyotis with the species’ use of space and habitats as determined with radio-telemetry. Classification tree modelling discriminated the scats of the seven macropod species, primarily on the basis of width. The reliability of identification was greatly improved with larger sample sizes and inclusion of a habitat parameter. Rates of scat loss and decay were variable and the greatest losses occurred in the wet season, particularly on sandy soils. Scat censuses underestimated the total area used by P. brachyotis but the distribution of scats showed the same broad pattern of habitat use found by radio-telemetry. We conclude that scats can accurately indicate the presence and habitat preferences of rock-dwelling macropod species. Introduction Australia that inhabit such rugged, remote areas, a relatively Spoor, particularly scats (faecal pellets), has been widely efficient technique that does not depend on preservation of used by indigenous peoples and hunters to identify the pres- DNA is required. ence and location of animals. Ecologists and land managers There are several critical assumptions that underpin the have also favoured using scats to study wildlife populations use of scats in surveys. First, the scats of the species must be because it is a non-intrusive technique and far less labour identifiable from other sympatric species. This is possible for intensive than traditional methods such as mark–recapture or many macropod species in Australia whose scats have a char- behavioural observations (Putman 1984; Kendall et al. 1992; acteristic and distinct shape (Triggs 1996; Jarman and Webbon et al. 2004). Scats have been used in surveys of a Capararo 1997). However, high rates of identification error range of taxa, including ungulates and carnivores (e.g. Neff sometimes occur. For example in a Tasmanian study, all 1968; Komers and Brotherton 1997; Bonesi and Macdonald observers, including those who frequently identified scats in 2004). In Australia, the technique has provided insights into the field, sometimes incorrectly identified Bennett’s wallaby the ecology and behaviour of various macropod species (Macropus rufogriseus) and pademelon (Thylogale (e.g. Caughley 1964; Hill 1981a; Lunney and O’Connell billardierii) scats (Bulinski and McArthur 2000). The scats 1988; Banks 2001). of the macropods of the Northern Territory have received The successful use of scats in ecological studies of little attention. Triggs (1996) offers photographs and broad macropods suggests that they may be an ideal tool for size categories for some species, and Churchill (1997) sug- investigating the cryptic rock-dwelling macropods of the gests that scats of P. concinna and P. brachyotis are distin- monsoon tropics of northern Australia. The rock-dwelling guishable but does not describe how. Thus it remains unclear macropods of the region (Petrogale brachyotis, P. concinna, whether the scats of the sympatric species can be reliably Macropus bernardus and M. robustus) inhabit steep rocky identified. terrain and flee to shelter when disturbed. The physical If scats are used to determine habitat preference and environment and their wary behaviour present formidable monitor changes in site occupancy of species, it is important challenges to ecologists, and little is known about their to determine whether the loss of scats is equal across habitats ecology (Strahan 1995). It remains uncertain whether scats and between seasons (Perry and Braysher 1986; Southwell can be used effectively to collect information about these 1989). Two processes affect the persistence of scats: decay species. Recent advances in DNA analysis of scats offer occurs in situ by physical weathering and insect activity, and great accuracy in determining the presence of species; loss of scats occurs by factors such as water run-off, wind, however, for the rock-dwelling macropod species of northern fire and removal by invertebrates. Experiments have found © CSIRO 2006 10.1071/ZO05074 0004-959X/06/050325 326 Australian Journal of Zoology W. R. Telfer et al. that environmental conditions and substrate greatly affect short-eared rock-wallaby (Petrogale brachyotis) scats dif- scat longevity. For example, scats persist much longer in ferent between seasons and among substrates in these tropi- cool, dry conditions and disappear rapidly in warm, wet con- cal environments? (3) How does the spatial distribution of ditions (Harestad and Bunnell 1987; Johnson and Jarman scats of P. brachyotis compare with the species’ use of space 1987; Vernes 1999). Also, scats deposited on rocks and in and habitats determined by radio-telemetry? caves may dehydrate quickly and decay slowly (Jarman and Capararo 1997), and those in long grass decay more quickly Methods than those in short grass (Johnson and Jarman 1987). Most Scat identification key studies of persistence have tended to be short-term (1–3 We collected scats from seven macropod species found in the tropics of months: Johnson and Jarman 1987; Vernes 1999) and, there- the Northern Territory (Table 1) from areas where the identification of fore, investigation of the rates of loss and decay of scats over the scats was known (from direct observation, previous studies and/or local knowledge). Scats of the rock ringtail possum (Petropseudes the course of a wet- and dry-season cycle in the monsoonal dahli) were also examined as this species is commonly found in the tropics is warranted. rocky habitats used by the rock-dwelling macropods. Although we When scats are used in surveys of habitat use and forag- recognise that there is some circularity in assuming that scats found in ing range, it is often assumed that the density and distri- the wild came from a particular species, this offered the only feasible bution of scats faithfully reflect the daily and seasonal methodology since some of the species of interest are not held in cap- movement patterns of the species. In the case of macropods, tivity, nor are they trappable. Furthermore, scats of animals in captivity that are fed on vegetable diets are often quite different in size and shape defaecation has been observed to occur frequently while to those of wild animals. For example, we found that the scats of some feeding and infrequently while resting (Hill 1978; Johnson species such as agile wallabies (M. agilis) held at the Territory Wildlife et al. 1987). Thus the density and distribution of scats have Park were quite different in size and shape to scats collected from wild primarily been interpreted as showing which habitats are animals from the population of M. agilis at East Point Reserve, Darwin. used by macropod species for feeding (Caughley 1964; Hill Between 35 and 500 scats per species were measured depending upon the availability of scats, with 2300 scats measured in total. We mea- 1981b; Lundie-Jenkins 1993). However, there has been little sured the size dimensions (length, width and breadth) of each scat with detailed examination of the concordance between the distri- calipers to an accuracy of 0.1 mm (Fig. 1). We also recorded colour butions of scats and the activity patterns and foraging ranges (black, brown, fawn, grey, white or rufous), shape (square, round, rect- of macropod species. Studies in North America have found angular, heart- or tear-shaped), and the presence of ‘squeeze points’(thin that the distribution of deer pellets underestimated their use taperings at the end of scats: Fig. 1). A scat identification key was devel- oped using Classification Tree modelling (Breiman et al. 1984; of some habitats as determined by observation or radio- Feldesman 2002) in the software package R (version 2.0.1, telemetry (Collins and Urness 1981; Loft and Kie 1988). R Development Core Team). Classification trees use binary recursive Clarification of