This work was carried out at the Department of Biology, Division of Zoology at the University of Oulu. I wish to thank the Head of the Department and all the staff for providing excellent working facilities for the research.
I am most grateful to my supervisor Docent Esa Hohtola for valuable advice, guidance, and support throughout this study. I wish to thank the leader of our working group, Docent Seppo Saarela, for giving me invaluable support and encouragement during this work. I also thank Professor Emeritus Raimo Hissa for introducing me the fascinating area of thermoregulation and for helping me in many ways. My nearest colleague, Phil. Lic. Hannele Säkkinen, has also been a great help and support for me, and her company and cheerful laughter has always kept me in a good mood. I wish to thank Mrs Annikki Tervonen, Mr Jorma Toivonen and Ms Marja-Liisa Martimo for excellent technical assistance. I thank Professor Matti Järvilehto, Docent Ahti Pyörnilä, Mrs Riitta Harjula, Ph.D. Tuija Liukkonen-Anttila, Ph.D Ahti Putaala and postgraduate students M.Sc. Mauri Hautaniemi, M.Sc. Satu Mänttäri and M.Sc. Mirja Laurila for giving me numerous valuable advice and for making my working days pleasant. Our skilful technician, Matti Rauman, solved many almost impossible technical problems. I wish to thank my former colleagues M.Sc. Tiina Mäkinen and M.Sc. Juha Siekkinen, the staff of the Zoological Gardens, and the office and the library personnel of the Department for their help. This study was financed by the Academy of Finland, the University of Oulu (the Thule Institut, the Department of Biology and the Faculty of Science) and the Societas Physiologicae Finlandiae ry. I highly appreciate the comments of Docent Hannu Rintamäki and Ph.D. G. Henk Visser regarding this thesis. I also thank Phil. Lic. Ian Morris-Wilson for revising the language of the summary of the thesis. Finally, I wish to express warmest thanks to my parents Terttu ja Olavi for their support and encouragement during my studies.