MODIFIED SEXUAL PHOTOPERIODICITY IN COTTONTAIL RABBITS

¹ From the Shade Swamp Sanctuary, Farmington, Connecticut

1. Three pairs of cotton-tail rabbits were confined in dens and runways and subjected to increased lighting at night from October 10 onward. Controls were not lighted but fed similarly.

2. The original objective, induction of winter litters, was not attained because, after varying times of lighting, one member of the pair killed the other and replacements were made on schedule.

3. Sex organs of males were modified to complete sperm formation in twenty-three days in December and January and mating libido reached, accompanied by breeding conditions of the epididymis. Controls showed mating libido but no spermatogenesis nor epididymal activation.

4. Lighted females mated and made nests; and one lined its nest with fur. Controls mated but made no nests. No pregnancies resulted with any female until April.

5. The induced changes indicate that these rabbits can be brought into breeding condition in winter by increased lighting, but modification of the method used and the provision of warmed nest-boxes are necessary for successful winter breeding and rearing of these animals.