Department of Evolution, Ecology, and Organismal Biology, University of California, Riverside, United States of America.
Department of Biological Sciences, Texas Tech University, United States of America.
Horm Behav. 2019 Aug;114:104536. doi: 10.1016/j.yhbeh.2019.05.005. Epub 2019 Jul 25.
Motherhood is energetically costly for mammals and is associated with pronounced changes in mothers' physiology, morphology and behavior. In ~5% of mammals, fathers assist their mates with rearing offspring and can enhance offspring survival and development. Although these beneficial consequences of paternal care can be mediated by direct effects on offspring, they might also be mediated indirectly, through beneficial effects on mothers. We tested the hypothesis that fathers in the monogamous, biparental California mouse (Peromyscus californicus) reduce the burden of parental care on their mates, and therefore, that females rearing offspring with and without assistance from their mates will show differences in endocrinology, morphology and behavior, as well as in the survival and development of their pups. We found that pups' survival and development in the lab did not differ between those raised by a single mother and those reared by both mother and father. Single mothers spent more time in feeding behaviors than paired mothers. Both single and paired mothers had higher lean mass and/or lower fat mass and showed more anxiety-like behavior in open-field tests and tail-suspension tests, compared to non-breeding females. Single mothers had higher body-mass-corrected liver and heart masses, but lower ovarian and uterine masses, than paired mothers and/or non-breeding females. Mass of the gastrointestinal tract did not differ between single and paired mothers, but single mothers had heavier gastrointestinal tract compared to non-breeding females. Single motherhood also induced a flattened diel corticosterone rhythm and a blunted corticosterone response to stress, compared to non-breeding conditions. These findings suggest that the absence of a mate induces morphological and endocrine changes in mothers, which might result from increased energetic demands of pup care and could potentially help maintain normal survival and development of pups.
母亲身份对哺乳动物来说是能量消耗巨大的，伴随着母亲生理、形态和行为的显著变化。在约 5%的哺乳动物中，雄性会协助雌性养育后代，并能提高后代的存活率和发育水平。尽管雄性的这种育幼行为的有益后果可以通过直接作用于后代来介导，但也可以通过对母亲的有益影响来间接介导。我们检验了这样一个假设，即一夫一妻制、双亲养育的加州鼠（Peromyscus californicus）中的雄性会减轻其配偶的育幼负担，因此，那些有和没有雄性协助养育幼崽的雌性在内分泌、形态和行为方面以及其幼崽的存活率和发育水平上会存在差异。我们发现，实验室中单独由母亲抚养的幼崽和由母亲和父亲共同抚养的幼崽的存活率和发育情况没有差异。单独的母亲比配对的母亲在喂食行为上花费更多时间。与非繁殖期的雌性相比，单独和配对的母亲在开阔地测试和悬尾测试中表现出更多的焦虑样行为，且体脂更少、瘦体重更多。与配对的母亲和/或非繁殖期的雌性相比，单独的母亲肝脏和心脏的去脂质量更大，而卵巢和子宫的质量更小。单独的母亲的胃肠道质量与配对的母亲没有差异，但比非繁殖期的雌性更大。单独的母亲也会引起皮质酮昼夜节律变平，以及对压力的皮质酮反应减弱，与非繁殖期的条件相比。这些发现表明，缺乏配偶会导致母亲在形态和内分泌方面发生变化，这可能是由于幼崽照顾的能量需求增加所致，并且可能有助于维持幼崽的正常存活率和发育。
