A comparison of three methods to evaluate otter latrine activity

Abstract

We compared methods commonly used in the field of river otter (Lontra canadensis) ecology to estimate visitation rates. We evaluated visitation rates estimated from 2 survey protocols based on video detection-individual visitation rate (IVR) and recording visitation rate (RVR)-and one indirect method based on scat detection-scat visitation rate (SVR). From August 2011 through August 2012, overall scat detection and cumulative video data from 403 camera-days in 2 latrine sites (River and Pond, at a study site adjacent to the Salt Fork of the Vermilion River near Fairmount, Illinois, USA) located <50 m apart did not reveal monthly or seasonal differences between SVR and video detection methods. We identified positive correlations among the 3 visitation rates and differences between overall IVR and RVR. All 3 methods resulted in peak visitation rates during winter. However, when these data were stratified by latrine site, we found both positive and negative correlations at the River latrine. Our work supports that SVR, IVR, and RVR are valuable methods to estimate otter visitation rates at latrine sites. However, it is clear that even within such a short distance between these 2 latrines, these methods detected differences in site utilization. The significant positive correlation observed between IVR and RVR (overall and by latrine site) suggests these methods can be used interchangeably. Otter detection using SVR may serve as a complementary assessment tool for IVR and RVR. To optimize cross-study comparisons and interpretation of results, future studies should detail the type of otter detection and visitation rate used, how variables are measured, formulas used in the calculation of the visitation rates, and detailed descriptions of scat counting efforts when using scat as a tool to evaluate otter visitation rates. Ó

Potential of restored gravel pits to provide suitable habitats for Eurasian otters in anthropogenic landscapes

“…However, other authors have found high correlation between spraint marking intensity and otter habitat use using camera‐trapping (e.g. Guter et al ; Rivera et al ). Furthermore, molecular genetic research has found a positive correlation between the relative otter spraint density and the number of otter genotypes in the area (Lanszki et al ).…”

Evaluating otter reintroduction outcomes using genetic spatial capture–recapture modified for dendritic networks

“…During 2018, we conducted non-invasive fecal DNA sampling of otter scats at active latrines located along 259 km of the URG dendritic network using a capture-recapture study design (Figure 3; Brzeski et al, 2013;Mowry et al, 2011). To maximize detection rates, we conducted sampling during February-April, which was within the typical river otter breeding season when latrine visitation and defecation rates are highest (Mowry et al, 2011;Rivera et al, 2019).…”

“…Yet, the intrinsic ecological characteristics of many wildlife species often present considerable difficulty in monitoring their populations. One such example is lutrinids, including North American river otters (Lontra canadensis; Figure 1), which are semiaquatic carnivores with strongly territorial but semi-social behavior that display high site fidelity over surprisingly large areas relative to their body size (Hung & Law, 2016;Larivière & Walton, 1998;Rivera et al, 2019;Stevens & Serfass, 2008). Their expansive territories and movement patterns are primarily structured by the hydrographical systems that they inhabit, such as rivers and coastal shorelines, which represent hierarchical dendritic networks comprised of multiple branches of suitable habitats (Brown & Swan, 2010;Campbell Grant et al, 2007).…”

“…Non-invasive genetic sampling of scats deposited at latrines is an efficient method for surveying otter populations, but otter diet and their tendency to defecate on exposed features result in fecal samples having notoriously high DNA degradation rates, poor amplification rates, and non-negligible genotyping error (Aristizábal Duque et al, 2018;Klütsch & Thomas, 2018;Lerone et al, 2014). The presumably high site fidelity of otters to multiple latrines (Gorman et al, 2006;Rivera et al, 2019;Stevens & Serfass, 2008) results in researchers approximately sampling with replacement when using non-invasive scat sampling, because an individual otter can visit multiple latrines multiple times within a single sampling occasion; however, these highly informative multi-site detection data are discarded when using traditional non-spatial models to estimate demographic parameters (e.g., Brzeski et al, 2013;Godwin et al, 2015). Furthermore, for species whose movements are predominantly constrained to within structured dendritic networks, not accounting for such restricted space use can severely bias estimates of population size, density, and thus population growth rate (Efford, 2019;Royle et al, 2013;Sutherland et al, 2015), potentially leading to flawed conservation and management.…”

Marking behaviour and census of Eurasian otters (Lutra lutra) in riverine habitats: what can scat abundances and non-invasive genetic sampling tell us about otter numbers?

“…Otters are secretive, mostly nocturnal living animals, but deposit scats (so-called otter spraints) at conspicuous sites along the watercourse (Reuther et al 2000;Kruuk 2006). Hence, scat count surveys have become a commonly used monitoring approach to ascertain otter distribution range (Reuther et al 2000), habitat selection (Mason and MacDonald 1987;Ottino and Giller 2004;Romanowski et al 2013), activity (Guter et al 2008;Day et al 2016;Rivera et al 2019) and relative abundance (Jefferies 1986;Mason and Macdonald 1987;Strachan and Jefferies 1996). While scat surveys are an approved method to assess otter distribution (the so-called standard survey method according to Reuther et al 2000), doubts and criticism have been raised on the validity and accuracy of this technique for conservation assessments (Reid et al 2013) and to assess population density, as well as habitat utilisation (Kruuk et al 1986;Kruuk and Conroy 1987).…”