...It isthe general observation that in most cases of prolonged pregnancies theoffspring are males...
U.S. Department of Agriculture 「Special Report on Diseases of Cattle」
...When entire litters are lost at anearly age, to predation, or other causes, productivity is muchincreased, with perhaps only short intervals between pregnancies...
Henry S. Fitch 「Ecological Observations on the Woodrat, Neotoma floridana」
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