Offspring sex varies with maternal investment ability: empirical demonstration based on cross-fostering

Robert, Kylie A.; Schwanz, Lisa E.; Mills, Harriet

doi:10.1098/rsbl.2009.0774

Cited by 30 publications

(44 citation statements)

References 13 publications

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“…[17 -19]). Recently, however, Robert et al [20] carried out an experimental study on tammar wallabies (Macropus eugenii derbianus) which shows that the capacity of maternal investment is a significant predictor of offspring sex. The only previous study we are aware of, which compared maternal energy expenditure when raising sons and daughters in an experimental setting, was performed on a sexually dimorphic bird: the brown songlark (Cinclorhamphus cruralis).…”

Section: Introductionmentioning

confidence: 99%

A trade-off between current and future sex allocation revealed by maternal energy budget in a small mammal

et al. 2011

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Sex-allocation theories generally assume differential fitness costs of raising sons and daughters. Yet, experimental confirmation of such costs is scarce and potential mechanisms are rarely addressed. While the most universal measure of physiological costs is energy expenditure, only one study has related the maternal energy budget to experimentally controlled offspring sex. Here, we experimentally test this in the bank vole (Myodes glareolus) by simultaneously manipulating the litter's size and sex ratio immediately after birth. Two weeks after manipulation, when mothers were at the peak of lactation and were pregnant with concurrent litters, we assessed their energy budget. We found that maternal food consumption and daily energy expenditure increased with the size of the litters being lactated. Importantly, the effects of offspring sex on energy budget depended on the characteristics of the simultaneously gestating litters. Specifically, the mothers nursing all-male litters and concurrently pregnant with male-biased litters had the highest energy expenditure. These had consequences for the next generation, as size of female offspring from the concurrent pregnancy of these mothers was compromised. Our study attests a higher cost of sons, consequently leading to a lower investment in them, and reveals the significance of offspring sex in moulding the trade-off between current and future maternal investment.

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Section: Introductionmentioning

confidence: 99%

A trade-off between current and future sex allocation revealed by maternal energy budget in a small mammal

et al. 2011

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“…With the accumulation of at least three generations of pedigree data, one could also incorporate the animal model (Wilson et al 2009). Because marsupials give birth to altricial young and many macropod species readily accept pouch young from other females (Merchant and Sharman 1966;Robert et al 2010), they are ideal for testing the relative importance of maternal effects during early development. …”

Section: Discussionmentioning

confidence: 99%

Kinship and sociability in eastern grey kangaroos

King¹

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School of Biological Sciencesii Frontispiece: A family group of eastern grey kangaroos at the Wilsons Promontory National Park in February, 2010, consisting of (left to right) adult female #6 (carrying a 3-month-old pouch young daughter that became #223), adopted young-at-foot daughter #116 (still suckling at approximately 15 months) and sub-adult daughter #7 of approximately 26 months. Photo by Wendy J. King.iii Abstract Animal grouping patterns are generally shaped by ecological constraints such as resource distribution or predation risk. Population density often increases competition, so that life-history consequences of association patterns should be particularly evident at increased densities. This thesis seeks to quantify how kinship affects association patterns in a species with unstable social bonds at high density. I also aimed to measure individual variation in sociability and evaluate its fitness consequences. Eastern grey kangaroos (Macropus giganteus) are gregarious herbivores, with a fission-fusion social system. I thus investigated how kinship and sex-age class affected behavioural and spatial associations in a high-density population of kangaroos at Wilsons Promontory National Park, Victoria.In Chapter 2, I examined relationships between individuals of different sex-age classes using halfweight indices (HWIs, which measure pairwise association strengths) and lagged association rates, and calculated six individual-based network measures. I found little social structure in the population. Mean HWIs were similar within and between different sex-age combinations (mean HWIs = 0.01 to 0.02). Individuals of all sex-age classes had preferred and avoided associates overall. Adult females showed a weak relationship (r = 0.05) between relatedness and HWIs, but this effect disappeared when controlling for geographic distance or spatial overlap between dyads.Lagged association rates decreased exponentially for adult males with adult females accompanied by young-at-foot in the breeding season. Most other lagged association rates decreased slightly in a linear fashion and few were constant. Although females without young-at-foot appeared to be more social than females with young-at foot, all associations among individual non-juvenile kangaroos were weak (mean HWI = 0.01). Sample size had strong positive effects on mean HWI and all six network measures (r = 0.40 to 0.66), which is more likely to occur in large populations where association strengths are generally low and individuals have many weak associations.I then combined observational data with genetic information to investigate sex-biased dispersal in Chapter 3. I found weak fine-scale genetic structure among adult females but none among adult males. Mean relatedness among adults was low (r = -0.01 to -0.03). Immature males moved away from their mothers at a younger age than did immature females. Although median distances of detected dispersals were 2-2.5 km for both sexes, only 6% of sub-adult females dispersed compared to 34% of sub-adult males. Adult fe...

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“…Most of their daughters will breed successfully even if they are small because there is reduced or no competition for mates in female mammals and size is less important for reproductive success than it is for males. Daughters are expected to be cheaper to produce because they have slower growth rates compared to males (see below) and they are usually smaller , Lee & Moss 1986, Redondo et al 1992, Robert et al 2010.…”

Section: Adaptive Hypotheses To Explain Biased Sex Allocationmentioning

confidence: 99%

“…Understanding the vast variety of birth sex ratios in mammals has been difficult due to their complex life histories and even more complex social interactions (Robert et al 2010, Robert & Schwanz 2011. Furthermore, the TWH and the LRCH are not mutually exclusive and both could be operating in natural population of animals (Robert & Schwanz 2011).…”

Section: Experimental Manipulations Of Sex Ratiosmentioning

confidence: 99%

“…Mothers produced more milk for female litters and defended them more intensively. Robert et al (2010) also performed a cross-fostering experiment in tammar wallabies (Macropus eugenii) to test if offspring sex is correlated with maternal investment. The weight of surviving offspring was not influenced by the sex of the offspring originally produced by the mother or the sex of the foster offspring.…”

Section: Experimental Manipulations Of Sex Ratiosmentioning

confidence: 99%

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Sex allocation, terminal investment and the effects of environmental constraints on maternal investment in subtropical antechinus

Faundes¹

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School of Biological Sciences iiCover photo: Female subtropical antechinus named Olive, born in 2012, hand-reared by Daniela Parra-Faundes and released back to the wild on mid-January 2013. This picture was taken three weeks after she was released. Photo: Daniela Parra-Faundes iii AbstractThis thesis addresses questions on sex allocation, life history strategies and costs of reproduction using experimental manipulations of litter sex ratios and field data on ecology and behaviour of the subtropical antechinus (Antechinus subtropicus).In chapter 2, I investigate two major adaptive hypotheses to explain sex ratio bias at birth: the Trivers-Willard Hypothesis (TWH) and the Local Resource Competition Hypothesis (LRCH). I show that sons are more costly to produce than daughters because they have fast growth rates and there are greater survival costs to mothers when they wean more sons. Mothers that naturally produced male-biased litters were slightly heavier than mothers that gave birth to female-biased litters. These results are consistent with the TWH, which states that mothers with more resources to invest benefit by producing high quality competitive sons that will reproduce. However, after increasing the natural bias of litter sex ratios, mothers were able to increase investment to meet demands of rearing more sons than they had naturally produced, without compromising offspring growth.These results are inconsistent with a key prediction of the TWH, that females give birth to the number of sons that they can afford to raise. Also inconsistent with the TWH, malebiased litters grew more quickly after the sex ratio manipulation and, were more likely to survive to weaning. The LRCH predicts that mothers in poor condition should reduce competition from the sex that competes the most, by allocating more to sons than to daughters, as females often remain in their natal home range after weaning. In support of the LRCH, large litter size was associated with slower growth rate in daughters, but not sons. These results differ from previous cross fostering manipulations to test sex allocation in mammals, which have unequivocally supported the TWH.In chapter 3 I examine changes in reproductive performance and survival with age in females. Senescence and terminal investment are two major models to understand effects of age on reproduction. Reproductive investment and success declines with age if senescence occurs, and investment in young increases near the end of life if terminal investment occurs, improving offspring performance at a cost to mothers. I show that older subtropical antechinuses females are not reproductively senescent. On the contrary, females had a greater investment ability and an overall improvement in reproductive performance with age. Older mothers increased investment in their second litters, and were able to produce high quality, large, fast growing offspring that were also more likely iv to survive that the offspring from younger females. However, this greater maternal reduced their own survival. These...

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Offspring sex varies with maternal investment ability: empirical demonstration based on cross-fostering

Cited by 30 publications

References 13 publications

A trade-off between current and future sex allocation revealed by maternal energy budget in a small mammal

A trade-off between current and future sex allocation revealed by maternal energy budget in a small mammal

Kinship and sociability in eastern grey kangaroos

Sex allocation, terminal investment and the effects of environmental constraints on maternal investment in subtropical antechinus

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