Náttúrufræðingurinn - 2009, Síða 45

45
Tímarit Hins íslenska náttúrufræðifélags
Þakkir
Þórir Haraldsson miðlaði upplýsingum af skrá sem hann hefur gert um
hvítabjarnarkomur til Íslands. Sarah Ann Medill í Kanada, Signe N.
Christensen-Dalsgaard í Noregi og Maja Kirkegaard í Kaupmannahöfn
sendu höfundi nýlegar námsritgerðir sínar um rannsóknir á aldri hvíta-
bjarna. Christian Sonne veitti ýmsar upplýsingar um stofninn sem lifir við
Austur-Grænland. Páll Hersteinsson og ókunnur ritrýnir lásu greinina og
gerðu athugasemdir. Þessum aðilum, ásamt samverkafólki við hvíta-
bjarnarrannsóknirnar hér á landi, er þakkað mikilsvert liðsinni.
Heim ild ir
Þórir Haraldsson & Páll Hersteinsson 2004. Hvítabjörn. Í: Íslensk spendýr 1.
(ritstj. Páll Hersteinsson). Vaka Helgafell, Reykjavík. Bls. 102–107.
Ævar Petersen & Þórir Haraldsson 1993. Komur hvítabjarna til Íslands 2.
fyrr og síðar. Í: Villt íslensk spendýr (ritstj. Páll Hersteinsson & Guttormur
Sigbjarnarson). Hið íslenska náttúrufræðifélag og Landvernd, Reykjavík.
Bls. 74–78.
Bjarni Sæmundsson 1932. Spendýrin. Bókaverslun Sigfúsar Eymunds-3.
sonar, Reykjavík. VIII+437 bls.
Gils Guðmundsson & Björn Vignir Sigurpálsson 1978. Öldin okkar. 4.
Minnisverð tíðindi 1961–1970. Forlagið Iðunn, Reykjavík. Bls. 71.
Gorgas, M. 1993. 5. Ursus (Thalarctos) maritimus (Phipps. 1774) – Eisbär.
Í: Handbuch der Säugetiere Europas. Band 5 (ritstj. Stubbe, M. &
Krapp, F.). AULA-Verlag, Wiesbaden. Bls. 300–328.
Stirling, I. 1998. Polar Bears. The University of Michigan Press. 220 bls.6.
Lentfer, J.W. 1984. Polar bear. Í: The Encyclopaedia of Mammals (ritstj. 7.
Macdonald, D.W.). Facts on File Inc., New York. Bls. 92–93.
Rosing-Asvid, Q., Born, E.W. & Kingsley, M.C.S. 2002. Age at sexual 8.
maturity of males and timing of the mating season of polar bears
(Ursus maritimus) in Greenland. Polar Biology 25. 878–883.
Aars, J., Lunn, N.J. & Derocher, A.E. (ritstj.) 2006. Polar Bears. Proceed-9.
ings of the 14th Working Meeting of the IUCN/SSC Polar Bear Special-
ist Group, 20–24 June 2005, Seattle, Washington, USA. Occasional Paper
of the IUCN Species Survival Commission No. 32. 198 bls.
Karl Skírnisson & Páll Hersteinsson 1993. Aldursgreiningar á refum. Í: 10.
Villt íslensk spendýr (ritstj. Páll Hersteinsson & Guttormur Sigbjarnarson).
Hið íslenska náttúrufræðifélag og Landvernd, Reykjavík. Bls. 32–33.
Jensen, B. & Nielsen, L.B. 1968. Age determination in the red fox (11. Vulpes
vulpes L.) from canine tooth sections. Danish Review of Game Biology
5(6). 15 bls.
Grue, H. & Jensen, B. 1979. Review of the Formation of Incremental 12.
Lines in Tooth Cementum of Terrestrial Mammals. Danish Review of
Game Biology 11. 1–48.
Allen, D.S. & Melfi, R.C. 1985. Improvements in techniques for aging 13.
mammals by dental cementum annuli. Proceedings of Iowa Academic
Sciences 92. 100–102.
Lieb, E. 1978. Eriochrome (Solochrome Cyanine R.S.): A superior sub-14.
stitute for haematoxylin in nuclear and myelin sheath staining tech-
niques. Laboratory Medicine 9. 13–19.
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Norway. Population Ecology 47. 267–275.
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bears by counts of cementum growth layer groups. Ursus 10. 449–453.
Christensen-Dalsgaard, S.N. 2006. Temporal patterns in age structure of 17.
polar bears (Ursus maritimus) in Svalbard, with special emphasis on vali-
dation of age determination. MS-ritgerð. University of Tromsø. 69 bls.
Medill, S.A. 2008. Reconstructing life histories using cementum informa-18.
tion recorded in premolars of polar bears (Ursus maritimus). MS-ritgerð,
University of Alberta. 118 bls.
Kirkegaard, M. 2003. History of selected immunological organs in east 19.
Greenland polar bears in relation to levels of organohalogens and age
determination and use of dental structures to determine female reproduc-
tive history in east Greenland polar bears (Ursus maritimus). MS-ritgerð.
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voru í Skagafirði í júní 2008. Óbirt skýrsla. Umhverfisráðuneytið og
Náttúrufræðistofnun Íslands. 14 bls.
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hvítabjörnum sem felldir voru í Skagafirði í júní 2008. Óbirt skýrsla.
Umhverfisráðuneytið og Náttúrufræðistofnun Íslands. 9 bls.
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No. 45. Greenland Institute of Natural Resources, Nuuk. 25 bls.
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and body mass of polar bears in western Hudson Bay. Canadian Journal
of Zoology 73. 1657–2665.
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Um höfundinn
Karl Skírnisson (f. 1953) lauk B.Sc.-prófi í líffræði frá
Háskóla Íslands árið 1977, B.Sc. 120 frá sama skóla árið
1979 og doktorsprófi frá Háskólanum í Kiel í Þýskalandi
árið 1986. Karl vann fyrst á Tilraunastöð Háskóla Íslands
í meinafræði að Keldum á árunum 1979–1981 og hefur
starfað þar við rannsóknir á sníkjudýrum og dýrasjúk-
dómum frá 1987.
Póst- og netfang höfundar/Author’s address
Karl Skírnisson
Tilraunastöð Háskóla Íslands í meinafræði að Keldum
v/ Vesturlandsveg
IS-112 Reykjavík
karlsk@hi.is
(Fig. 4). Each pattern starts with a wide,
translucent band (marked S in Fig. 4)
which is assumed to have appeared in
the year when the cubs were weaned
and the female could feed alone in late
winter, mating occurred and the female
eventually denned. This broad, light
staining band is in all cases followed by
a broad and dense, dark staining incre-
mental line in the cementum (marked H
in Fig. 4). This line was presumably
formed during a winter spent with the
cubs in the den, when the female starved
to a greater extent than in the two sub-
sequent years when two similar but
markedly narrower growth-layer-
groups were formed (marked 2 and 3 in
Fig. 4). Furthermore, a broad, dark-
staining incremental line had appeared
when the female was estimated to have
been five years old. Due to the similari-
ties of this band and the H-marked
bands (Fig. 4) it is suggested that the
female also gave birth to cubs when she
was five years old, cubs that probably
soon died and were not raised because
mating seemed to occur in the follow-
ing spring. Distinct “false” or “accesso-
ry” lines in the cementum layer of the
female (for example those marked with
b and d in Fig. 4) might be attributed to
physiological and hormonal changes
within the reproductive cycle.
In the cementum layer of the male
some of the inconspicuous, dark bands
(labelled a–f, Fig. 5) might be true incre-
mental lines. Thus, the male might
have been older than the estimated 22
½ years. Interestingly, a broad, dark
staining incremental line developed in
the cementum layer when the male
was estimated to have been three years
old. If the aging is correct, this band
would reflect the tough life after wean-
ing when the young bear became inde-
pendent.
Possible reasons for the unusual
behaviour of the two bears swimming
ashore in early summer in Iceland are
discussed.