Higher mortality of smaller sika deer fawns

Bodyweight, breast girth and hind-foot length were compared in sika deer fawns (Cervus nippon Temminck) that were shot or had died naturally. The study site was Mount Goyo, in northern Japan. Samples were collected in January and February every year from 1982 to 1991 for the dead fawns and from 1990 to 1992 for the living fawns. The average bodyweight and the variation in bodyweight was significantly smaller in the dead fawns than in the living ones, suggesting a higher mortality rate in smaller fawns. The mean breast girth and hind-foot length were also significantly smaller in the dead fawns. Two possibilities are suggested: (i) the smaller fawns were born later than the larger fawns and grew at normal rates; or (ii) the smaller and larger fawns were born in a similar period but grew at different rates thereafter.     

Human Prenatal Investment Affected by Maternal Age and Parity

This paper investigates the effects of mother's age and parity on the prenatal allocation of resources in sons and daughters using a sample of 6994 in 20- to 34-year-old mothers from Granada (Spain). This study tests the Trivers–Willard allocation model, which predicts that, depending on the mother's condition, there can be a bias from 50/50 expected investment in the sexes. The results show that mothers of 25–29 age class produce relatively heavier sons compared to younger mothers, suggesting a bias in the allocation of resources before birth favoring neonate boys. This extra investment in boys appears to be related more to the mother's age than to her parity. Offspring of multiparous mothers had shorter gestation length, but multiparous mothers of the 25–29 age class had boys with a longer gestation than the younger ones. The 25–29 age class mothers are in the peak of fertility and they are presumably in better condition than the other mothers in the study sample. The results suggest that Granada women performed a sex-biased prenatal investment favoring sons by prolonging the gestation period. An index of boys' extra birth weight is proposed as a suitable variable to measure the maternal prenatal investment.     

Is a foetus developing in a sterile environment?

Novel findings in microbiology question the long‐standing paradigm that a healthy pregnancy implies a sterile uterus. It now seems that the placenta is frequently colonized with bacteria, and a placental microbiome has been identified. Recent literature findings are summarized here, and an attempt is made to separate pathological bacterial presence from a naturally occurring microbiome.     

与年龄相关的Logistic种群增长方程的局部稳定性

本文讨论与年龄相关的人口增长Logistic模型在平衡人口结构附近的局部稳定性。借助于文[2][6]中方法,研究死亡率函数是与年龄相关的。首先我们导出平衡方程,从平衡方程可以证明当两个参数值即临界出生率δB与临界死亡率δD满足一定关系时,稳定性完全被确定;在其它一些关系时,稳定性与不稳定性问题有待以后深入研究。最后,用实例过进一步阐明这些结果。