of 1948-49 and 1949-50, Fitch found that most rats lost
weight and hardly any, even those that were short of adult size, made
gains.

The following records of a male born in the spring of 1949 show rapid
growth and attainment of adult size in his first summer, cessation of
growth during the winter, and resumption of growth, with attainment of
near-maximum size the following spring.

June 16, 1949 96 gms.
September 26, 1949 230 gms.
September 27, 1949 230 gms.
October 18, 1949 260 gms.
October 27, 1949 250 gms.
October 29, 1949 220 gms.
November 8, 1949 235 gms.
November 15, 1949 245 gms.
November 24, 1949 240 gms.
November 26, 1949 240 gms.
November 30, 1949 240 gms.
December 20, 1949 260 gms.
February 18, 1950 230 gms.
April 5, 1950 290 gms.
April 7, 1950 300 gms.
October 7, 1950 320 gms.
November 29, 1950 345 gms.
March 23, 1951 340 gms.

Another example, showing winter cessation of growth in a male at even
smaller size is shown below. This was in the winter of 1950-1951.

November 9 145 gms.
November 28 175 gms.
November 29 165 gms.
January 10 180 gms.
January 11 175 gms.
March 1 225 gms.
March 23 200 gms.

_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 i