Longevity

The longest span of records for an individual woodrat recorded was 991 days in a female, already adult when she was first caught on November 18, 1948. Other relatively long spans of records were: 827 days in a male, adult when first caught on March 16, 1952; 754 days in a female, also adult when first captured; 649 days in a male first captured as a juvenile; 465 days in a male, adult when first captured; 409 days in a male, juvenile when first captured; 399 days in a female, juvenile when first captured; 395 days in a female, adult when first captured; 390 days in a female, adult when first captured; 366 days in a male, adult when first captured. Of these eleven individuals (six females and five males) whose records cover more than a year, eight were already adult when first caught. These eleven rats represent only 4.3 per cent of the total number captured. Our study was made at a time when populations were shrinking and disappearing, and obviously individual spans would have been longer if we had been working with a stable population. In most instances the spans of our records represent only small parts of the life spans of the individuals involved. Nevertheless, our records emphasize the potentially greater longevity of the woodrat as contrasted with the various smaller rodents living in the same area. Of several thousand individuals of the genera Mus, Zapus, Reithrodontomys, Peromyscus, Sigmodon, and especially Microtus, none is known to have survived so long as two years, and only a few individuals are known to have survived so long as one year after being marked.