Individual identification via non-invasive genetic sampling has become of prime importance in conservation programmes, as it allows for genetic studies of wild animals without having to trap or observe them (Taberlet & Luikart, 1999).
The Eurasian otter Lutra lutra is currently showing a recovery following a decline throughout its range, and the increasing UK populations are now internationally important. However, even basic information such as population size is difficult to obtain because otters are secretive and the problems associated with assessing numbers from spraint density.
Material for the genetic characterisation of wild Eurasian otters (Lutra lutra) has previously been derived from carcasses and faeces (Dallas & Piertney 1998). Hair samples are however a much more reliable source of DNA than faeces, and offer the opportunity of sampling the living population more effectively. Until now there has been no research into methods of sampling hairs from wild otters or on the DNA extraction efficiency from these hairs. In 2004 - 2005 Natural Research, working with researchers at Glasgow University and the Loch Lomond National Park, funded a pilot study to compare the DNA extraction efficiency from hair samples and spraints, and to develop an efficient method for obtaining hair samples in the wild
The aims of this research were to:
develop an efficient method for obtaining hair samples in the wild and
determine the DNA extraction efficiency from collected hairs
This information would allow the development of suitable methods for studying the population density and movement patterns of otters and to develop a protocol for assessing otter populations.
Hair traps designed to recover a small sample of hair were tested using captive held otters at Chestnut Centre, Peak District, at the Highland Wildlife Park, Kingussie and with wild otters filmed using infra-red cameras on the River Dee in association with the Centre for Ecology and Hydrology at Banchory. The traps were relatively successful in captive environment, but completely unsuccessful in the wild, with otters actively avoiding them. Work is ongoing to improve the efficiency of the hair traps.
Genetic samples were obtained from 15 road-killed otters and paired hair and tissue samples were taken from each otter. DNA was extracted from the tissue samples using a Protinease K digestion in a PCR compatible buffer. Individual root hair segments were treated by two different methods (1) Chelex Ionic bead resin treatment and (2) Protinease K digestion in a PCR compatible buffer. The DNA extracts were typed by PCR for 8 microsatellites using the latest versions of the primers (Dallas et al, 2002).
The Protinease K digestion used for the tissue extraction gave a 100% success rate. The Chelex hair extraction method gave a 55% amplification success rate while the Protinease K method gave a much higher amplification success of 87%.
The DNA extraction efficiency from hairs (55 - 87 %) was considerably greater than that previously reported for spraints (20 %). Further work will firstly develop efficient hair traps and then determine the feasibility of using these methods to study the spatial ecology and population density of otters in the wild.
Click on the citation below for a pdf of a peer-reviewed article about our technique.
Taberlet, P. and Luikart, G. (1999). Non invasive genetic sampling and individual identification. Biological Journal of the Linnean Society 68: 41-55.
Dallas, J. F. and Piertney, S. B. (1998). Microsatellite primers for the Eurasian otter. Molecular Ecology 7: 1247-1251.
Dallas, J. F., Coxon, K. E., Sykes, T., Chanin, P. R. F., Marshall, F., Carss, D. N., Bacon, P. J., Piertney, S. B. and Racey, P. A. (2003). Similar estimates of population genetic composition and sex ratio derived from carcasses and faeces of Eurasian otter Lutra lutra. Molecular Ecology 12: 275-282
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