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Biology 130: Methods in Field Biology

Field Technique:  Scat Analysis



scat analysis

Scat Studies, National Geographic

Scat ID guide

Use of scat-detection dogs to locate scat for population analysis (From RELATIVE ABUNDANCE OF ENDANGERED SAN JOAQUIN KIT FOXES (VULPES MACROTIS MUTICA ) BASED ON SCAT–DETECTION DOG SURVEYS):

We attempted to enhance recovery of scats of kit fox during surveys by using a trained detection dog to locate kit fox scats. It has been previously demonstrated that dogs trained to locate scats of target species can provide a successful method of scat recovery (U. Breiten-moser and C. Breitenmoser-Wursten, unpubl.data; P. Paquet, unpubl. data; Smith et al.,2001, 2003; Wasser et al., 2004). One of the main advantages of using a detection dog to locate scats is that the dog can detect both old as well as fresh scats, and thus, recent past as well as current presence in an area can be determined. Our prior studies showed that dogs are capable of locating kit fox scats that are several weeks to several months old (D. A.Smith et al., unpubl. data).

To determine the reliability of surveys using detection dogs for inventorying kit foxes throughout their range, we evaluated the effectiveness of a trained dog to locate scats in core and satellite population areas with various densities and different habitat conditions. We found that scat-detection dog surveys consistently detected the presence of kit foxes in each population area searched regardless of relative fox density and habitat type (Smith et al., 2005).

Our prior research indicated detection dogs found scats at a mean distance of 4.8 +/- 6.7 m from the transect line (maximum distance = 38.40 m; Ralls and Smith, 2004). Length of survey routes on each property varied depending on the amount of, and access to, suitable kit fox habitat (mean = 10.57 km, range = 1 to 37 km) (Table 1). Previously, we found that scat collection on 30, 1-km transects in 6 areas with known kit fox populations revealed approximately 29.83 +/- 36.60 scats per km (range = 1 to 130) (D. A. Smith et al., unpubl. data). Thus, we chose 1-km transects as the minimum to be searched.

Transect routes used both unpaved roads and vegetation available on survey properties. We chose to survey unpaved roads because, in areas with known kit fox populations, a high proportion of scats were deposited along unpaved roads (Smith et al., 2005). Also, we searched in vegetation because, unlike humans searching for scats, dogs can easily locate scats under those conditions (Smith et al., 2001, 2003). A detection dog-handler team and a navigator walked all survey transects. When the dog registered the presence of a fox scat, it was geo-referenced witha global positioning system (GPS). Scats collected for DNA analysis were stored in plastic bags containing one teaspoon of silica gel for desiccation (FisherScientific, Pittsburgh, Pennsylvania) and were shipped within 7 days of collection to the Genetics Program at the Smithsonian Institution for storage at -20 C.

A review paper compared 11 methods of diet analysis using scat (From REVIEW A comparison and critique of different scat-analysis methods for determining carnivore diet)

We used the following 11 methods to quantify the proportion of food categories in diets. The first four methods hereafter are referred to as qualitative methods, as only absence and presence data are recorded. The remaining methods are classified as quantitative, as the share of each food category in the scats is recorded.

  1. Frequency of occurrence per scat, expressed as the percentage of scats containing a particular food item [occurrence per scat with trace (OccST); Breuer 2005].

  2. Frequency of occurrence per food item,expressed as a percentage of the number of occurrences of one food item of the total number of occurrences of all food items [occurrence per item with trace (OccIT); Breuer 2005].

  3. Frequency of occurrence per scat, not including trace amounts [i.e. items contributing <5% to scat volume; occurrence per scat without trace (OccS); Kamler et al. 2007].

  4. Frequency of occurrence per food item, not including trace amounts [occurrence per item without trace (OccI); Kojola et al. 2004].

  5. Percent volume of remains of each food category in scats, estimated visually to the nearest 5% [percent of the scat volume (VOL); McDonald & Fuller 2005].

  6. Percent mass in scats, obtained by multiplying the proportion of the estimated volume with the scat mass [dry mass of remains in the scat (MASS); Forman 2005].

  7. Biomass ingested calculated using the correction factors of Atkinson et al.(2002), as given by Loveridge and Macdonald (2003; BioAtk).

  8. Biomass ingested calculated using the correction factors of Goszczyn´ski (1974) supplemented with correction factors compiled by Je˛drzejewska and Je˛drzejewski (1998; BioGosz).

  9. Mammalian biomass ingested calculated according to the linear regression model developed by Floyd et al. (1978), using the modifications of Weaver (1993; BioFloyd).

  10. Mammalian biomass ingested calculated according to the linear regression model of Ruehe et al. (2003; BioRue).

  11. Biomass ingested according to the linear regression model of Weaver and Hoffman (1979) using the number of individuals detected (BioWea). Because this method was developed especially for small mammals,we used it only for mammalian prey up to the size of ground squirrels Xerus inauris (650g).

The body mass of species needed for the biomass calculations were taken from Stuart and Stuart (2001). Because it was rarely possible to distinguish between fawns and adult antelopes, we used a mean prey mass of 15kg for all ungulates larger than steenbok Raphicerus campestris, assuming that mainly, but not exclusively, young individuals were consumed.

Excerpted from Effects of Intraguild Predation: Evaluating Resource Competition between Two Canid Species with Apparent Niche Separation

We collected and analyzed scats to determine both kit fox and coyote diets. Scats of these two sympatric canids were distinguished by size, shape, and odor [4142], as well as associated tracks and sign. We drove dirt road transects (114 km) monthly to collect scat for both species and clear the road for the next month’s survey. Transects were distributed throughout the study area and passed through all 7 habitats. A vehicle with a driver and 2 observers drove transects in both directions before considering them clear. A low amount of fox scats on transects necessitated similar clearing and collection of scats at den sites. We classified transects and den sites as either highland or lowland based upon topography and elevation [17]. Once collected, scats were placed in paper bags labeled with month, species, and elevation. After being air dried, scats were transferred to nylon stockings, washed in a washing machine, and air dried. We analyzed indigestible remains using a light microscope for hair identification, and a locally obtained specimen collection for the identification of teeth, bones, and exoskeletons. Presence of individual prey species in each scat was recorded and percent occurrence calculated (no. of occurrences of an item/total no. of occurrences of all food items). We used the number of individuals observed in each prey category comprising >10% of prey item occurrence to model canid distribution. While the size of each prey species varied, we used the occurrence of prey due to the lack of a biomass conversion for kit foxes and the major prey species in their diet. Future studies incorporating a biomass conversion for each prey species could prove useful.

DNA extraction from scat is being used to identify species and individuals, even going so far as to mimic mark recapture to estimate population size (from Estimating Population Size of Mexican Wolves Noninvasively (Arizona)):

Thus far, radiotelemetry has been a satisfactory method. However, collaring and tracking more wolves in the expanding population is expensive. The development of a cost-effective method to estimate Mexican wolf populations will assist the long-term management and recovery of wolves. We are attempting species and individual identification using DNA extracted from wolf scat because scat is both readily available and easy to collect (Putman 1984). Progress in contemporary molecular genetics has made noninvasive genetic sampling of an animal population possible (Goossens et al. 2000, Prugh et al. 2005). The ability to identify an individual through DNA amplification of a scat sample allows us to treat reoccurrences of a genotype in additional samples as marked recaptures. Mark-recapture models may then be used to estimate population size based on collected genotypes. We are currently developing appropriate laboratory, sampling, and field protocols to collect scat and conduct a genetic mark-recapture study of Mexican wolves in a portion of the BRWRA.

We tested our ability to identify individual Mexican wolves in the lab by collecting scat and blood from eight captive wolves at the Sevilleta National Wildlife Refuge in New Mexico. We stored scat samples in 50-ml centrifuge tubes along with silica beads to act as a desiccant (1:4 scat to silica beads by volume), using filter paper barriers to prevent silica dust from embedding itself on the surface of the scat. We extracted DNA from surface scrapings of scat following the protocol for human DNA analysis from stool samples (QIAGEN 2007). We have successfully amplified 10 canid specific microsatellite markers (Ostrander et al. 1993) in the Sevilleta samples. These markers allowed us to obtain individual genotypes for all eight wolves. We are in the process of cross-checking genotypes obtained from scat against those obtained from blood.


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