Czech Otter Foundation Fund

Successful conservation and management of rare and elusive species requires reliable estimates of population size, but acquisition of such data is often challenging. We compare the two most frequently used methods of assessing abundance of Eurasian otter (Lutra lutra) populations, noninvasive genetic sampling (NGS) based on genotyping of faeces and field surveys using snow tracking. In a 100-km2 oligotrophic otter habitat with linear water bodies, both methods yielded very similar estimates (10–12 individuals). However, in a 100-km2 fishpond area, consisting of a complex network of rivers, fishponds, channels and marshes, genotyping of faeces revealed the presence of a higher number of individuals (46–50 genotypes) than the snow survey (38 individuals). NGS data analysed by capture-mark-recapture (CMR)-based software CAPWIRE provided even higher estimates, being twice the number assessed through snow tracking (76–81 individuals, CI95% = 49–96 and 55–89). Our results suggest that the performance of both NGS and snow tracking is comparable in simple linear habitats, but in complex habitats with very high otter density a combination of genetic and field methods, or CMR analysis using genetic data, is recommended. We emphasise that to obtain reliable estimates using NGS it is necessary to follow strict protocols for detection and elimination of genotyping errors. Based on a literature review and our experience, we suggest improvements that may increase the success rate and efficiency of NGS for otters.

Abstract Over the latter part of the 20th century, Eurasian otter Lutra lutra populations suffered dramatic declines, resulting in extinction or fragmentation of populations in many western and central European countries. Part of the Czech otter population became totally isolated while the Slovak population remained partly connected to the relatively continuous central and eastern European otter distribution range. This paper examines the genetic structure and past demographic history of otters in the Czech and Slovak Republics, using microsatellite nuclear markers amplified from DNA extracted from tissue and faecal samples. A relatively high level of genetic differentiation was found between the Czech and Slovak populations (FST=0.154, P=0.0002), supported by a perfect assignment in Bayesian cluster analysis. Both the Czech and Slovak populations showed significant heterozygosity excess (assuming an infinite allele model), indicating recent population bottlenecks. A very recent population decline was also suggested by coalescent analysis, inferring a drop to c. 25% of past effective population size in both populations. The timing of the decline was in accordance with published data from otter surveys, suggesting that the strongest decline probably occurred between the 1970s and the mid‐1990s. The results of this study confirm that otter populations remain vulnerable to any violent demographic change and, despite the claims of fish‐farmers and anglers for legal culls, it is highly desirable that they remain a strongly protected species in both countries. The spreading and re‐connection of otter populations observed recently is essential for the future health of the populations, and should be supported through habitat conservation.