Andrén, H., Linnell, J.D.C., Liberg, O., Ahlqvist, P., Andersen, R., Danell, A., Franzén, R., Kvam, T., Odden, J. & Segerström, P. 2002: Estimating total lynx Lynx lynx population size from censuses of family groups. - Wildl. Biol. 8: 299-306.
Counts of reproductive units, i.e. family groups, constitute the main monitoring index for lynx Lynx lynx populations in Scandinavia. However, for some purposes it is necessary to extrapolate from the number of family groups to obtain an estimate of total population size. Using data on survival and reproduction from radio-marked lynx from three Scandinavian study areas, we simulated the lynx population structure in February. The average proportions of family groups out of all independent individuals, i.e. adults and yearlings, in these simulations were 21% ± 2.1 (SD), 22% ± 3.6 and 27% ± 3.1 for the data sets from northern Sweden (Sarek), southeastern Norway (Hedmark) and south-central Sweden (Bergslagen), respectively, and the overall mean for all three study areas was 23% ± 3.8. This translated into extrapolation factors of 6.14 ± 0.44 , 6.24 ± 0.73 and 5.48 ± 0.40 for the three study areas, respectively, leading to an overall mean for all three study areas of 5.95 ± 0.64. We conclude, that it is possible to extrapolate from the number of family groups to obtain an estimate of total lynx population size with a statistical measure of uncertainty.
Key words: census, lynx, monitoring, population simulations, reproduction
Henrik Andrén, Olof Liberg, Per Ahlqvist & Anna Danell, Grimsö Wildlife Research Station, Department of Conservation Biology, Swedish University of Agricultural Sciences, SE-730 91 Riddarhyttan, Sweden - e-mail addresses: henrik.andren@nvb.slu.se (Henrik Andrén); olof.liberg@nvb.slu.se (Olof Liberg); per.ahlqvist@nvb.slu.se (Per Ahlqvist); anna.danell@nvb.slu.se (Anna Danell)
John D.C. Linnell, Reidar Andersen* & John Odden, Norwegian Institute for Nature Research, Tungasletta 2, NO-7485 Trondheim, Norway - e-mail addreses: john.linnell@ninatrd.ninaniku.no (John D.C. Linnell); reidar.andersen@nt.ntnu.no (Reidar Andersen); john.odden@chello.no (John Odden)
Robert Franzén, Swedish Environmental Protection Agency, SE-106 48 Stockholm, Sweden - e-mail: robert.franzen@environ.se
Tor Kvam, Department of Resource Sciences, North-Trøndelag College, Box 145, NO-7702 Steinkjer, Norway - e-mail: tor.kvam@hint.no
Peter Segerström, Vaikijaur 617, SE-962 99 Jokkmokk, Sweden - e-mail: peter.solbritt@jokkmokk.pp.se
*Present address: Department of Zoology, Norwegian University of Science and Technology, NO-7491 Trondheim, Norway
Corresponding author: Henrik Andrén
Received 12 September 2001, accepted 21 January 2002
Associate Editor: Henryk Okarma