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The Chemical Basis of Odour Recognition in the Eurasian or European Otter, Lutra lutra
PI: Joerg D. Hardege
The naturally low density of otter populations together with their shy and elusive behaviour (a trait) of many mammal species, especially the mustelids) makes direct observation very difficult. For this reason field signs, particularly spraints (otter droppings and/or anal gland secretion) have been used for many years in an attempt to help monitor populations by establishing trends in both numbers and habitat preference (Green & Green, 1980/87/97; Jefferies, 1989).
To date this has been the best available monitoring method, but there has been some controversy over its validity. It has been argued that whilst spraints may be useful in monitoring otter distribution, their worth as a tool for monitoring otter numbers is limited. Kruuk et al. (1986) advise caution when using spraint surveys as a method when assessing habitat utilisation by otters.
After decades of decline, not only in Britain, but right across their ‘Eurasian’ range, otters are slowly returning. With the validity of available surveying methods being called into question, reliable information regarding established, expanding and introduced/translocated otter populations is scarce. When the results from such surveys are used as the basis for conservation and management decisions the need for a solid surveying technique is both evident and essential.
Scent-marking, territoriality & individual recognition
The pattern of faecal marking in many carnivore species suggests a role in territorial marking (Macdonald, 1980). If such a system were to work however, there would have to be a level of differentiation between individual scent marks.
Sprainting behaviour in otters has been linked with home range advertisement and territorial marking (Erlinge, 1967, 1968; Kruuk & Hewson, 1978) as well as resource marking (Kruuk, 1995). Otters therefore must at least possess the ability to differentiate between spraints of known and unknown individuals, or more specifically to separate its own smell from those of others. If an otter were able to demonstrate ‘recognition’, i.e., the ability to distinguish several spraints from a single individual, then this would mean that a wild otter could visit numerous spraint piles and know whether the same individual had visited them all, providing a spatial history. Behavioural work by Trowbridge (1983) on captive otters established that otters do indeed possess this ability.
Additionally if part of the message conveyed included information about the age of the spraint, an otter would not only know whether a certain individual had visited a certain location, but when…giving a spatio-temporal history.
If scent material is used for individual recognition, then it needs to be stable when placed in the environment for periods of time that at least match the frequency that a scent-mark will be encountered. If a scent mark is to be representative of an individual then it must possess this sort of stability (Albone & Perry, 1975; Albone et al.1977; Preti et al. 1977).
There are two main ways that individual identity could be conveyed:
&Mac183; unique individual scent compounds in each of an individual’s spraints. For example, possibly similar to the sex specific scent components in the anal gland secretion of the African mongoose, Herpestes ichneumon. (Hefetz et al., 1984).
&Mac183; spraints of every individual could comprise the same scent components with their relative proportions providing an individual odour ‘fingerprint’?
If the individuality code within spraint odour profiles could be deciphered revealing an individual odour ‘fingerprint’ and a method of ageing spraints found in the field could be developed, then these would prove invaluable tools in monitoring both established otter populations and re-introduced or translocated animals, providing a far more accurate picture than simple spraint surveying.
Scent marking glands associated with the anal region are common in many carnivore species. Anal sacs are common in mustelid species and many studies of mustelid anal gland scent material have been carried out (e.g., pine martens, Martes martes – Pulliainen, 1982; European badger, Meles meles – Kruuk, 1978; American mink, Mustela vison – Sokolov et al., 1980; stoat, Mustela erminea – Erlinge et al., 1982; ferret, Mustela putorius, Crump, 1980).
Despite this, a limited number of studies have been carried out the anal scent sacs of the Eurasian otter, particularly as regards elucidation of secretion chemical constituents (Gorman et al., 1978; Jenkins et al., 1981; Stevens, 2000 unpublished).
The project
This therefore presents an excellent opportunity to revolutionise our ability to monitor otters (both in terms of behaviour and population numbers/distribution), whilst simultaneously increasing our knowledge of the control of social behaviour in semi-aquatic vertebrates.
Gas chromatography coupled with Mass spectrometry will be used to identify the signal components of scent material collected both from captive animals at otter sanctuaries, and from wild animals in the field. A comprehensive study will initially be carried out on spraint material from groups of captive otters, i.e., known individuals.
References
Albone, E.S. (1977) Ecology of mammals – a new focus for chemical research. Chem. in Britain, 13, 92-99.
Albone, E.S. & Perry, G.C. (1975) Anal sac secretion of the Red Fox Vulpes vulpes; volatile fatty acids and diamines: implications for a fermentation hypothesis of chemical recognition. Journal of Chemical Ecology, 2(1), 101-111.
Crump, D.R. (1980) Anal Gland Secretion of the Ferret (Mustela putorius forma furo). Journal of Chemical Ecology, 6, 837-844.
Erlinge, S. (1967b) Home range of the otter, Lutra lutra L., in southern Sweden. Oikos, 18, 186-209.
Erlinge, S. (1968) Territoriality of the otter Lutra lutra L. Oikos, 19, 81-98.
Erlinge, S., Sandell, M. & Brinck, C. (1982) Scent marking and its territorial significance in stoats, Mustela erminea. Animal Behaviour, 30, 811-818.
Gorman, M.L., Jenkins, D. & Harper, R.J. (1978) The anal sacs of the otter Lutra lutra. J.Zool. (Lond.) 186, 463-474.
Green, J. & Green, R. (1980) Otter Survey of Scotland 1977-79. Vincent Wildlife Trust, London.
Green, J. & Green, R. (1987) Otter Survey of Scotland 1984-85. Vincent Wildlife Trust, London.
Green, R. & Green, J. (1997) Otter Survey of Scotland 1991-94. The Vincent Wildlife Trust, London.
Hefetz, A., Ben-Yaacov, R. & Yom-Tov, Y. (1984) Sex specificity in the anal gland secretion of the Egyptian mongoose Herpestes ichneumon. J.Zool. (Lond.) 203, 205-209.
Jefferies, D.J. (1989) The changing otter population in Britain 1700-1989. Biological Journal of the Linnaean Society, 38, 61-69.
Jenkins, D., Makepeace, M. and Gorman, M.L. (1981) Two-dimensional electrophoresis of otter (Lutra lutra) anal gland secretions. Journal of Zoology, London, 195, 558-559.
Kruuk, H. (1978) Foraging and spatial organisation of the European badger, Meles meles L. Behavioural Biology and Sociobiology, 4, 75-89.
Kruuk, H. (1995) Wild Otters. Predation and Populations. Oxford University Press, Oxford.
Kruuk, H., Conroy, J.W.H., Glimmerveen, U. & Ouwerkerk, E. (1986) The use of spraints to survey populations of otters (Lutra lutra). Biological Conservation. 35, 187-94.
Kruuk, H. & Hewson, R. (1978) Spacing and foraging of otters (Lutra lutra) in a marine habitat. Journal of Zoology, London, 185, 205-12.
Macdonald, D.W. (1980) Patterns of scent marking with urine and faeces among carnivore communities. Symposia of the Zoological Society of London, 45, 107-139.
Preti, G., Smith, A.B. & Beauchamp, G.K. (1977) Chemical and behavioural complexity in mammalian chemical communication systems: guinea pigs (Cavia porcellus), marmosets (Saguinus fusicollis) and humans (Home sapiens). In: Chemical signals in vertebrates. D. Müller-Schwarze and M.M. Mozell (eds). Plenum, New York. pp 95-114.
Pulliainen, E. (1982) Scent-marking in the pine marten (Martes martes) in Finnish Forest Lapland in winter. Zeitschrift für Säugetierkunde, 47, 91-99.
Sokolov, V.E., Albone, E.S., Flood, P.F., Heap, P.F., Kagan, M.Z., Vasilieva, V.S., Roznov, V.V. & Zinkevich, E.P. (1980) Secretion and secretory tissues of the anal sac of the mink, Mustela vison: Chemical and histological studies. J.Chem.Ecol. 6, 805-825.
Stevens, R. (2000) Anal scent gland secretion of the otter (Lutra lutra). Final year dissertation (Unpublished)
Trowbridge, B.J. (1983) Olfactory Communication in the European otter Lutra l. lutra. Ph.D. dissert., Univ. Aberdeen, Scotland. 201 pp.
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