Age structure of six populations of old-field mice,Peromyscus polionotus

Summary

An accurate age-estimating technique, based on biochemical changes in eye lens protein, was used to study age structures of six populations of the old-field mouse,Peromyscus polionotus. A new mathematical procedure permitted quantitative comparisons of these populations. Four inland populations had essentially the same median ages (75–84 days), maximum ages (248–297 days) and relative production rates (56–58% of the surviving population had been born in the 100 days prior to sampling). Approximately 50% of the females were old enough to have weaned a litter. One inland population had a lower median age (49 days), a lower maximum age (181 days) and a higher relative production rate (73%). Relatively fewer females (38%) could have weaned a litter. The single beach population was also different, with higher median age (180 days), and lower relative production rate (2%). All females were old enough to have weaned a litter. Maximum age was essentially the same as for the four similar, inland populations. Factors which may have contributed to observed differences in these populations are discussed.