The accuracy of scat identification in distribution surveys: American mink, Neovison vison, in the northern highlands of Scotland

Abstract

Distribution data for elusive species are often based on detection of field signs rather than of the animal itself. However, identifying field signs can be problematic. We present here the results of a survey for American mink, Neovison vison, in the northern highlands of Scotland to demonstrate the importance of verifying field sign identification. Three experienced surveyors located scats, which they identified as mink scats, at seven of 147 sites surveyed and "possible" mink scats at a further 50 sites. Mitochondrial DNA was successfully extracted from 45 of 75 (60%) scats, collected from 31 of the 57 "positive" sites; sequencing of amplified DNA fragments showed that none of these scats was actually of mink origin. We consider the implications of erroneous survey data and the potential waste of resources and misdirection of conservation/ management actions. We discuss potential methods that may be useful to verify field sign identification, including the use of DNA analysis, and stress that verification is crucial to ensure rigorous and reliable survey data.

Monitoring European wildcat Felis silvestris populations using scat surveys in central Spain: are population trends related to wild rabbit dynamics or to landscape features?

“…The use of scats to carry out this type of ecological study dealing with carnivores has been questioned due to possible misidentification of the specific scat origin (e.g., Davison et al 2002;Janecka et al 2008;Harrington et al 2010). Even so, a number of studies, also based on genetic analyses of scats, showed a high accuracy of the involved surveyors (Zuercher et al 2003;Prugh and Ritland 2005;Barja et al 2007;Harrington et al 2008;Rosellini et al 2008;.…”

“…Thus, according to IUCN quantitative criterion A.2.b, it would be possible to qualify the species as critically endangered, endangered, vulnerable, or near threatened depending on observed reductions of 80%, 50%, 30%, or 20%, respectively, in the proposed AI within a period of 10 years or three generations (IUCN 2001). Only in those areas of Europe with the presence of the other wild felid species, Iberian lynx (Lynx pardinus, Temminck 1827) or European lynx (Lynx lynx, Schreber 1777), could confusion with wildcat scats be possible and genetic analysis of scats would be necessary (Guzmán et al 2004;Alda et al 2008;Harrington et al 2010). Even so, the technical staff and scientists working on recovery programs of Iberian lynx in Spain are convinced that most scats can be differentiated without genetic analyses when field experience is extensive enough (as the size, shape, and color of lynx scats considerably differ; Gil-Sánchez (personal communication)).…”

“…Perhaps the same could be said about European lynx scats (at least, it is expected that their physical measurements, such as the diameter, would be significantly larger than those of wildcat scats). However, in those particular cases in which researchers suspect that scat surveys may not be completely reliable due to any reason (including the lack of sufficient field experience), the data obtained must be verified using complementary methods such as genetic analysis or camera trapping, which cannot be the first option for monitoring wildcat populations across Europe due to their higher economic costs (e.g., Barea-Azcón et al 2007;Harrington et al 2010). Even so, there are many large areas of Europe where the wildcat is the only wild felid species present (Mitchell-Jones et al 1999) so that monitoring based on scat surveys can be applied without identification problems in a wide extent of the wildcat's range.…”

“…In terms of the European wildcat, we urgently need easy and relatively cheap methods for monitoring populations of this threatened species across all of its wide range. It does not seem realistic to propose a large-scale population monitoring on the basis of more expensive or even prohibitive (as recognized by Harrington et al 2010) alternative methods such as genetic analyses or camera trapping. Nevertheless, genetic analyses are needed when facing other types of questions: for example, both the identification of hybrids and the monitoring of their frequency of occurrence within populations over time continue to be relevant for the conservation of the European wildcat genotype (e.g., French et al 1988;Driscoll and Nowell 2010).…”

Seasonal Variation of Coyote Diet in Northwestern Wyoming: Implications for Dietary Overlap with Canada Lynx?

“…Scat is therefore used frequently in wildlife ecology to evaluate the presence/absence of elusive animals (Palomares et al 2002), estimate animal abundances (Hurlbert 1971, Kohn et al 1999, Prugh et al 2008, characterize diets (Reynolds and Aebischer 1991, Symondson 2002, Deagle et al 2005, and investigate animal health or disease ecology (Gompper et al 2003, Liccioli et al 2012. Historically, scats have been identified to species by morphology, but the morphological distinctions among scats produced by mammalian mesopredators can be difficult to discern and improperly identified specimens can confound and even invalidate research (Harrington et al 2009). Despite some successes with field based scat identifications (Zuercher et al 2003, Prugh andRitland 2005), which are more reliable when made in conjunction with additional natural sign (e.g.…”