Date Thesis Awarded


Access Type

Honors Thesis -- Access Restricted On-Campus Only

Degree Name

Bachelors of Science (BS)




Paul D. Heideman

Committee Members

Eric L. Bradley

John D. Griffin

Randolph A. Coleman


The study of life-history strategies asks how the timing of reproduction, fecundity, offspring size, and related measures affect fitness. This thesis attempts to answer the following question: Does a change in hormone levels correlate with or cause a change in life-history strategies of an organism? Using two selection lines of Peromyscus leucopus, we investigated the variation in several hormone levels between the two mouse lines. The responsive line responds to a short day length by suppressing reproduction. The non-responsive line maintains reproduction in short days. There were no significant differences between lines in their mean levels of peripheral Insulin-like Growth Factor-1 (IGF-1). However, levels of IGF-1 were correlated with a number of reproductive measures in our mice. We conclude that levels of IGF-1 hormone, while related to reproduction, are not a likely source of evolutionary change in our mice. There were significant differences in levels of testosterone between photoperiods, but not between lines. We conclude that levels of testosterone are related to the photoperiod change, but not the difference between our selection lines. There were no significant differences in levels of estrogen between photoperiods or lines. However, serum effects may have affected the estrogen assay that was used. We conclude that there may be no significant differences in levels of estrogen, but these results should be confirmed with a more reliable assay.

Creative Commons License

Creative Commons License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 License.


Thesis is part of Honors ETD pilot project, 2008-2013. Migrated from Dspace in 2016.

On-Campus Access Only