Short- and long-term effects of litter size manipulation in a small wild-derived rodent

Abstract

Iteroparous organisms maximize their overall fitness by optimizing their reproductive effort over multiple reproductive events. Hence, changes in reproductive effort are expected to have both short-and long-term consequences on parents and their offspring. In laboratory rodents, manipulation of reproductive efforts during lactation has however revealed few shortterm reproductive adjustments, suggesting that female laboratory rodents express maximal rather than optimal levels of reproductive investment as observed in semelparous organisms. Using a litter size manipulation (LSM) experiment in a small wild-derived rodent (the common vole; Microtus arvalis), we show that females altered their reproductive efforts in response to LSM, with females having higher metabolic rates and showing alternative body mass dynamics when rearing an enlarged rather than reduced litter. Those differences in female reproductive effort were nonetheless insufficient to fully match their pups' energy demand, pups being lighter at weaning in enlarged litters. Interestingly, female reproductive effort changes had longterm consequences, with females that had previously reared an enlarged litter being lighter at the birth of their subsequent litter and producing lower quality pups. We discuss the significance of using wild-derived animals in studies of reproductive effort optimization.

Limits to sustained energy intake XXVII: trade-offs between first and second litters in lactating mice support the ecological context hypothesis

“…This contrasts with several previous studies which have suggested that increased nursing costs of larger litters only affect the success of current reproduction (Hare and Murie, 1992;Kenagy et al, 1990;Mappes et al, 1995;Neuhaus, 2000;Oksanen et al, 2001). Instead, the results of the present study are consistent with those of other studies showing a trade-off (Koivula et al, 2003;Lehto Hurlimann et al, 2014) The immediate cost of experimentally elevated litter size was the small size of pups at the time of weaning. For M. musculus, the suggested minimal physiological weaning mass, at which pups reach a state of independence and are able to survive on their own, is around 9 g (König and Markl, 1987).…”

“…litter size at weaning was 276% larger but total litter mass was only 38% greater, resulting in significantly smaller pups in enlarged litters than in reduced ones. Other studies in rodents have shown similar effects of enlarged litters (Lehto Hurlimann et al, 2014;Mappes et al, 1995;Oksanen et al, 2001;Rogowitz, 1998;Speakman et al, 2001). For instance, in common voles, Microtis arvalis, females with an enlarged litter showed increased reproductive effort (i.e.…”

“…For instance, in common voles, Microtis arvalis, females with an enlarged litter showed increased reproductive effort (i.e. higher metabolic rate and alternative body mass dynamics), but weaned smaller pups (Lehto Hurlimann et al, 2014). In contrast, when bank voles, Myodes (=Clethrionomys) glareolus, were supplemented with extra food, enlarging litters had no effect on the weaning size of pups (Koskela , food intake (B), litter size (C), litter mass (D) and pup mass (E) on day 0-18 of lactation.…”

Is metabolic rate a universal ‘pacemaker’ for biological processes?

“…food abundance (Glazier, 2009d). Experimentally enlarged litter sizes result in increased BMR in lactating females of the common vole Microtus arvalis (Pallas) (Hürlimann et al, 2014), thus showing that increased reproductive energy demand can stimulate metabolic rate, rather than vice versa as expected by the metabolic pacemaker assumption. Experimentally enlarged litter sizes result in increased BMR in lactating females of the common vole Microtus arvalis (Pallas) (Hürlimann et al, 2014), thus showing that increased reproductive energy demand can stimulate metabolic rate, rather than vice versa as expected by the metabolic pacemaker assumption.…”

Maternal oxidative stress and reproduction: Testing the constraint, cost and shielding hypotheses in a wild mammal

“…Central to life‐history theory, the “cost of reproduction” hypothesis predicts that breeding individuals should trade‐off high investments into current reproduction with future survival or reproductive prospects (Hirshfield & Tinkle, ; Reznick ; Stearns, ; Williams, ). While fitness costs to reproduction have often been highlighted (Descamps, Boutin, McAdam, Berteaux, & Gaillard, ; Flatt, ; Koivula, Koskela, Mappes, & Oksanen, ; Lehto Hurlimann, Stier, Scholly, Criscuolo, & Bize, ; Linden & Møller, ; Nager, Monaghan, & Houston, ; Nur, ; Penn & Smith, ), the mechanisms responsible for such costs remain poorly understood, despite an increasing effort to integrate physiological approaches in understanding this compromise (Rubach et al, ; Zera & Harshman, ).…”