Seasonal coat color distribution of Mustela frenata Long-tailed Weasel in North America

1. Seasonal coat color distribution of Mustela frenata (Long-tailed Weasel) in North America

2. Seasonal coat color distribution of Mustela frenata (Long-tailed Weasel) in North America 1. Seasonal coat color change

3. Seasonal coat color change All three species of N. Amercian weasels and other species of mammals from arctic foxes, hares and lemmings, molt to a white coat in the winter and brown coat in the summer

4. Seasonal coat color change In species that do change and have been studied, the change from one color to another is the result of a molt, the loss of fur, of one color, and the growth of fur of a different color.

6. Why molt to white? White coat offers a thermal advantage -

7. Why molt to white? White coat offers a thermal advantage -

8. Why molt to white? White coat offers a thermal advantage - Not likely

9. Why molt to white? White coat offers a thermal advantage - Not likely

11. Suggested influences of north/south distribution Temperature - populations differ in response to temperature (King 1989) Pop. Living in climatic extremes do not need flexibility of those found in area of transition. A temp. switch is what determines color of molt. Studies by Rothschild(1942), Feder (1990)�etc demonstrated coat color is directly related to area of origin for individuals. Unlikely that mechanism determining color change would be present at the individual level rather then population as a whole.

12. Suggested influences of north/south distribution Assuming an individual changes color to escape detection, then it makes sense that the transition zone is maintained by natural selection. The disadvantage of remaining brown must be severe because all Arctic weasels turn white in the winter

13. Suggested influences of north/south distribution Hewson & Watson (1979) looked at the relationship between winter whitening, snow cover, and temperature in Scotland and Yorkshire Found that differences in proportion turning white between different regions and altitudes within regions were positively associated with number of days of snowfall and snow lie and inversely with monthly minimum temperature.

14. What we do know? The fall molt is initiated by photoperiod. Individual fall molt color change appears to be genetically determined. Days of snow lie, not temperature, influence proportion of white individuals found. The color of hair growth following molt appears to be determined by the presence or absence of MSH - acts as an intracellular blocking factor

15. Where are we going? Would transition zone outlined by Hall (1951) be located in same areas today? DNA and breeding experiments over several generations. May provide an opportunity to study natural selection in short time frame. Is new white growth the result of the prolactin inhibition or the high levels of melatonin that cause inhibition of MSH?

16. Bissonnette, T. and E. Wilson. 1939. Shortening daylight periods between May 15 and September 12 and the pelt cycle of the mink. Science. 89:418. Feder, S. 1990. Environmental determinants of seasonal coat color change in weasels (Mustela erminea) from two populations. M.S. Thesis. University of Alaska Fairbanks. Feist, D. and R. White. 1989. Terrestrial mammals in cold. In advances in Comparative and Environmental Physiology, vol. 4, edited by L. Wang, Springer-Verlag Berlin Heidelberg. Hall, E.R. 1951. American Weasels. University of Kansas Museum of Natural History. 4:1-466. Hewson, R. and A. Watson. 1979. Winter whitening of stoats (Mustela erminea) in Scotland and Northeast England. Journal of Zoology. 187:55-64

17. King, C.M. 1989. The Natural History of Weasels and Stoats. Comstock Publishing Association., Cornell University Press, N.Y. Rust, C.C. 1965. Hormonal control of pelage cycles in the short tailed weasel (Mustela erminea bangsi). General and Comparative Endocrinology. 5:222-231.