Abstract
Abstract: Sampling wild animal populations using non-invasive techniques is advised when dealing with threatened species. Hair samples provide ecological information like species and individual identification. However, hair trapping is scarcely used in otters, due to their aquatic habits. Most studies are with captive individuals, so there is the need to test non-invasive hair trapping methods in otters in the wild. The aim of this study was to develop a simple and cost-effective method to collect hair from otter species in a non-invasive way. The study was carried out in the Paranapanema River, São Paulo State, Brazil, with the Neotropical otter (Lontra longicaudis Olfers, 1818), a protected species. Hair traps (wooden sticks and tree roots with adhesive tape or wax bands) were set during six nights on river banks, otter trails and scent-marking sites. Traps were baited with otter fresh spraints from other river locations. From the 23 traps, 10 (43.7%) were successful in collecting otter hairs, mostly guard-hair. The sticks were much more efficient than the roots at capturing otter hair (70.6.% vs. 0%) as well as adhesive tape when compared to wax (71.4% vs. 0%). Method simplicity and efficiency suggest that it can be a cost-effective way for collecting otter hairs without the need for capturing individuals. This method can be used for: assessment of local otter distribution; collecting otter hair samples for sex and individual identification (by molecular analysis), trophic ecology (by isotopic analyses), ecotoxicology (by contamination analysis) or behaviour ecology (by hormonal and stress levels analysis). More trapping campaigns should be implemented to further test the method's efficiency.
Highlights
Monitoring or sampling wild animal populations is important to increase our scientific knowledge on the structure and functioning of ecosystems and to inform managers and decision-makers, when dealing with elusive and low density species, still lacking relevant ecological information
Among the non-invasive sampling methods that have been developed to survey mammals, hair samples have the advantage of providing ecological information, like species and individual identification (e.g. Foran et al 1997), hormonal and stress levels (Koren et al 2002, Macbeth et al 2010), diet reconstruction based on carbon and nitrogen isotope values (e.g. Hobson et al 2000, Mitani et al 2009, Walter et al 2014) and exposure to environmental contamination (e.g. Pereira et al 2006)
There are some studies addressing the practicability of various field techniques for capturing and radio-tracking otters (e.g. Ó Néill et al 2008), modified body-snares or foot-hold traps (Ben-David et al 1998, Newsome et al 2009) or Hancock traps (Mitchell-Jones et al 1984) are not advised due to safety concerns especially since all but one (North American river otter - Lontra canadensis Schreber, 1777) out of the thirteen existing otter species in the world have a conservation status of Endangered (EN), Vulnerable (VU) or Near Threatened (NT) and decreasing population trends in most of their range (IUCN 2017)
Summary
Monitoring or sampling wild animal populations is important to increase our scientific knowledge on the structure and functioning of ecosystems and to inform managers and decision-makers, when dealing with elusive and low density species, still lacking relevant ecological information. There is an increasing pressure from the public, environmental and scientific bodies to use non-invasive techniques, in particular when surveying mammals (Sikes & Gannon 2011). Otters are semi-aquatic mammals, most of them elusive and shy species, that rest on land but use water in most of its daily activities and most of the times their dens are on the water edges opening directly to water (Kruuk 2006). Traditional capture methods, such as box/ cage traps, tend to have low capture success (Kranz 1995). Non-invasive methods that supply biological samples such as hair trapping should be pursued
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