Tedor J B, Reif J S
J Am Vet Med Assoc. 1978 May 15;172(10):1179-85.
Breed, geographic, and seasonal distributions of canine births registered with the American Kennel Club for the years 1971 to 1973, accompanied by litter size and sex ratio data, were studied. A few breeds accounted for a large portion of the births. The breed distribution of births changed as popularity of various canine types waxed and waned. The geographic distribution of births generally paralleled the pattern of human population and was relatively stable. A distinct, repetitive seasonal distribution of births was evident. Human intervention probably molded much of this pattern, but genetic factors and environmental conditions also were involved. Litter size and sex ratio varied primarily with breed rather than with region or season and hence appeared genetically based.
对1971年至1973年在美国养犬俱乐部登记的犬类出生的品种、地理和季节分布进行了研究，并附带了窝产仔数和性别比例数据。少数品种占出生总数的很大一部分。随着各种犬类类型受欢迎程度的起伏，出生的品种分布发生了变化。出生的地理分布总体上与人口模式相似且相对稳定。明显存在一种独特的、重复性的出生季节分布。人为干预可能塑造了这种模式的很大一部分，但遗传因素和环境条件也有涉及。窝产仔数和性别比例主要随品种而非地区或季节变化，因此似乎基于遗传。
