SREL Reprint #0336




Effects of Radiation on Reproduction of Irradiated Cotton Rats (Sigmodon hispidus) Trapped from Enclosed Areas of Natural Habitat

Michael 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.

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