Department of Pathobiology, Ontario Veterinary College, University of Guelph, 419 Gordon St, Guelph, ON, N1G2W1, Canada.
Facultad de Medicina Veterinaria y Agronomía, Universidad de las Americas, Manuel Montt 948, 7500000, Santiago, Chile.
Oecologia. 2022 Jun;199(2):343-354. doi: 10.1007/s00442-022-05200-0. Epub 2022 Jun 9.
The success of maternal foraging strategies during the rearing period can greatly impact the physiology and survival of dependent offspring. Surprisingly though, little is known on the fitness consequences of foraging strategies during the foetal period. In this study, we characterized variation in maternal foraging strategy throughout pregnancy in a marine top predator (South American fur seal, Arctocephalus australis), and asked if these shifts predicted neonatal health and postnatal survival. We found that during early pregnancy all pregnant females belonged to a single, homogenized foraging niche without evident clusters. Intriguingly though, during late pregnancy, individual fur seal mothers diverged into two distinct foraging niches characterized by a benthic-nearshore and a pelagic-offshore strategy. Females that shifted towards the benthic-nearshore strategy gave birth to pups with greater body mass, higher plasmatic levels of glucose and lower levels of blood urea nitrogen. The pups born to these benthic females were eight times more likely to survive compared to females using the pelagic-offshore foraging strategy during late pregnancy. These survival effects were mediated primarily by the impact of foraging strategies on neonatal glucose independent of protein metabolic profile and body mass. Benthic-nearshore foraging strategies during late pregnancy potentially allow for the greater maternal transfer of glucose to the foetus, leading to higher chances of neonatal survival. These results call for a deeper understanding of the balance between resource acquisition and allocation provided by distinct foraging polymorphisms during critical life-history periods, and how this trade-off may be adaptive under certain environmental conditions.
母兽在育幼期觅食策略的成功与否，对依赖其生存的幼崽的生理和存活有着重大影响。然而，令人惊讶的是，人们对于胎儿期觅食策略的适应意义却知之甚少。在本研究中，我们描述了一种海洋顶级捕食者（南极大环海豹，Arctocephalus australis）在整个孕期的觅食策略变化，并探讨了这些变化是否能预测新生儿的健康和产后的存活率。我们发现，在妊娠早期，所有怀孕的母兽都属于单一的、同质化的觅食生态位，没有明显的聚类。然而，在妊娠晚期，个别大环海豹母兽分化为两种截然不同的觅食生态位，一种是近岸底栖觅食，另一种是远海洄游觅食。向近岸底栖觅食策略转变的母兽所产幼崽的体重更大，血糖水平更高，血尿素氮水平更低。与在妊娠晚期采用远海洄游觅食策略的母兽相比，这些近岸母兽所产幼崽的存活率高出 8 倍。这些生存效应主要是由觅食策略对新生儿血糖的影响介导的，而与蛋白质代谢谱和体重无关。妊娠晚期的近岸觅食策略可能使母兽向胎儿输送更多的葡萄糖，从而提高新生儿的存活率。这些结果呼吁我们更深入地了解在关键生命史阶段，不同觅食多态性之间资源获取和分配之间的平衡，以及这种权衡在某些环境条件下如何具有适应性。
