Can hair traps sample wild boar (Sus scrofa) randomly for the purpose of non-invasive population estimation?

Abstract

Reliable estimation of population size remains a major challenge in wildlife ecology and management. Lately, genotyping of non-invasively obtained tissue samples integrated in a modified capture-recapture approach provides new perspectives. Faeces, moulted feathers, or hairs can be easily sampled in the field. However, an important assumption is homogeneity of sampling across the population. In this pilot study, we tested the suitability of baited barbed wire hair sampling stations ('hair traps') for homogeneous genetic sampling for population estimation. A video system based on a new network internet protocol was used to observe the behaviour of wild boar visiting baited hair traps for gaining information about potential heterogeneities in the individual sampling probability. Within 92 monitoring nights at two sampling stations, 216 wild boar visits were recorded and 142 hair samples containing 2,124 single hairs were collected. Video analysis revealed distinct differences in the behaviour of wild boar with respect to the sampling station which are most likely to result in heterogeneous individual sampling probabilities. Adult and subadult animals differed in their behaviour dependent on their group status. This result indicates that hair sampling with baited hair traps is not suitable for representative non-invasive sampling of free ranging wild boar populations.

Field calibration of blowfly-derived DNA against traditional methods for assessing mammal diversity in tropical forests

“…TFR, comprising logged dipterocarp forest (5°11=N, 102°41=E), is one of 17 ecological linkages recognised in the Malaysia Federal Government's "Central Forest Spine Master Plan for Ecological Linkages" to restore connectivity between four fragmented forest complexes (DTCP and DOF 2012). (Catling et al 1997) Operates 24 h without supervision (Catling et al 1997) Difficult to standardise (varying dimensions, baited/un-baited, and deployment location effects) (Fontúrbel 2010;Torre et al 2010) Medium (Garden et al 2007) Mist nets Frugivorous bats (Stoner and Timm 2004) Readily portable (Kuenzi and Morrison 1998) Must be monitored constantly, as bats can become easily entangled and must be freed individually (Kuenzi and Morrison 1998) Low (Kuenzi and Morrison 1998) Harp traps Insectivorous bats (Kingston et al 2003) Does not require constant monitoring (Tidemann and Woodside 1978) Bulky and not easy to transport (Tidemann and Woodside 1978) High (Tidemann and Woodside 1978) Camera traps Medium to large-bodied mammals (Bernard et al 2013) Effective in detecting species rarely recorded from live traps or direct observations (e.g., Hose's civet, Diplogale hosei; Bernard et al 2013) May under-represent species with specific habitats and unable to distinguish closely related species (e.g., muntjac and mouse-deers; Bernard et al 2013) High (Sanderson and Trolle 2005) Indirect signs Medium to large-bodied ground dwelling mammals (Catling et al 1997) Effective in detecting species inhabiting open areas (e.g., otters and ungulates; Catling et al 1997) Imprecise in species identification (Davison et al 2006;Mumma et al 2014); Accuracy and precision are dependent on field conditions and expertise of identifiers (Silveira et al 2003) Low (Garden et al 2007 (Valderrama et al 1999;Ebert et al 2010) Low (Castro-Arellano et al…”

Monitoring wild pig populations: a review of methods

“…Moreover, when pigs are trapped for the purpose of marking and then release, there can be an understandable reluctance to release a potentially destructive, often invasive species back into the environment. The same heterogeneity issues as indicated earlier also hold forth when attempting "captures" using baited hair traps for genotyping (Ebert et al 2010). Capture heterogeneity weakens population estimates, and if the population is also not closed, density estimates by CMR become more uncertain.…”

“…Collection of samples also needs to consider assumption violations through capture heterogeneity (e.g., Ebert et al 2010), including assumptions of equal capture rates between sex, age, and social classes, important but often overlooked assumptions when analyzing DNA studies.…”

An optimized hair trap for non-invasive genetic studies of small cryptic mammals

“…A minimum of three to ten hair bulbs are needed to reduce genotyping errors significantly (Gagneux et al 1997). The use of hair traps with mechanical devices (e.g., barbwire) or attached glue-like substances to collect plucked hairs is not ideal as it rarely collects high proportions of hairs with roots (Ebert et al 2010;Valderrama et al 1999). Here, we present a new, costefficient, optimized hair trap for non-invasive sampling that uses movable parts to collect efficiently hairs with Communicated by C. Gortázar bulbs.…”