A molecular approach to identifying the relationship between resource use and availability in Eurasian otters (Lutra lutra)

Abstract

In South Korea, the Eurasian otter (Lutra lutra (Linnaeus, 1758)), a semi-aquatic carnivore, is found mainly in lower order streams that tend to have a low abundance of preferred prey fish species. To investigate the relationship between resource use and availability, we used DNA barcoding to identify otter diet items in 24 otter spraints (faeces) from 16 sites along the Nakdong River basin from 4 to 6 June 2014. At these sites fish availability was assessed using scoop nets and casting nets. Fish formed the bulk of otter diet, which included also frogs, mammals, and reptiles. By DNA barcoding (success rate: 72.38%), we identified 79 prey items from 105 bone remains. The diet comprised mostly fish, but frogs, mammals, and reptiles were also identified. The fish fauna and otter diet composition differed significantly. Across the study sites, members of the Cyprinidae dominated in netted samples, but occurred less frequently in otter diet. Because most Cyprinidae are fast swimmers, otters also fed on benthic fishes and frogs, suggesting limited foraging flexibility in otters and specialization on more slowly moving prey.

DNA metabarcoding-based diet survey for the Eurasian otter (Lutra lutra): Development of a Eurasian otter-specific blocking oligonucleotide for 12S rRNA gene sequencing for vertebrates

“…Previous studies [31–33] demonstrated that 12S rRNA gene sequences provide accurate identification of most of fishes including teleosts at species level, highlighting the 12S rRNA gene as an ideal marker for diet analyses of Eurasian otters. Additionally, we confirmed that fish species identified in this study are in agreements with fish species detected from spraints by a previous study [10] and spatial distributions of their habitats in Korea [34].…”

“…Similar to the previous findings [35–37], the majority of the detected fishes belonged to the family Cyprinidae (Fig 4) among which Carassius auratus (crucian carp) was the most dominant species detected across all spraints (Fig 5). A previous study also reported that Cyprinidae was the most dominant diet by the Eurasian otters along a river basin in South Korea [10]. C .…”

“…Both of these frog species inhabit Korea [43], and a study reported Rana spp. in spraints collected along a river basin in Korea [10]. However, they were not abundant, with mean relative abundances of 2.7% for Pelophylax nigromaculatus and 0.5% for Rana spp., suggesting that frogs are not primary diets of the Eurasian otters during this time of the year at our sampling site possibly because of the sufficient availability of fishes.…”

“…Nonetheless, knowledge is limited regarding their detailed taxonomies in part due to limited resolving power of traditional morphological methods [9]. Meanwhile, Hong et al [10] used a Sanger sequencing-based approach to identify vertebrate species for each individual bone remain isolated from spraints. However, this approach is laborious and requires technical expertise that limits the capacity of information generation.…”

Spatial genetic structure in the Eurasian otter (Lutra lutra) meta-population from its core range in Italy

“…Could this be an evidence of dispersal of these otters along the coastal sea line? It is reported that the Eurasian otter, thanks to its plasticity, may live along the sea coast (Elmhirst, 1938;Kruuk & Hewson, 1978;Chanin, 1985;Panzacchi et al, 2011) and can expand its home range to include salt water when suitable prey fish are scarce (Crowley et al, 2013;Lanszki et al, 2014;Mulville, 2015;Hong et al, 2019), like other medium-sized carnivores (Doncaster & Woodroffe, 1993;Eide et al, 2004), even though it requires access to fresh water for the cleaning of the fur (Kruuk & Balharry, 1990;Beja, 1996). Furthermore, many reports from zoophilic enthusiasts (on social networks) would corroborate this hypothesis, but further investigations are necessary.…”