|SREL Reprint #0336|
of Radiation on Reproduction of Irradiated Cotton Rats (Sigmodon hispidus)
Trapped from Enclosed Areas of Natural Habitat
R. Pelton and Ernest E. Provost
Each month for four successive months four different
groups of wild female cotton rats (eight females per group) were irradiated at
dose levels ranging from 500 to 1200 R at a dose rate of about 20 R/min.
These animals were released into 1-acre outdoor enclosures with four
control females and four untreated males. Data
from recaptured females revealed that breeding activity did not produce a
lowered resistance to radiation. Susceptibility
to radiation damage within the months encompassed by these experiments
apparently did not change. A direct
relationship between dose level and prevalence of pregnancy was shown.
Sex ratios of progency of irradiated females were essentially 50:50, and
no gross abnormalities in the young were observed.
Litter sizes decreased from controls to 750 R. Higher doses did not further decrease litter sizes thus
lending credence to the idea that a pool of resistant acolytes remained shortly
after irradiation and resulted in viable fetuses.
The effects (maternal and genetic) of radiation on the females apparently
resulted in a severe selection pressure acting on the animal before implantation
of young (or shortly thereafter), since the number of placental scars equaled
the number of young born. The dose
level at which even immediate breeding is unsuccessful in the cotton rat under
natural conditions was not adequately established by these experiments.
SREL Reprint #0336
Pelton, M.R. and E.E. Provost. 1971. Effects of radiation on reproduction of irradiated cotton rats (Sigmodon hispidus) trapped from enclosed areas of natural habitat. p. 1048-1054. In Third National Symposium on Radioecology, edited by D.J. Nelson. ORNL CONF 710501 P2. Oak Ridge, TN.