Sex allocation in a polygynous mammal with large litters: the wild boar

Fernández-Llario, Pedro; Carranza, Juan; Mateos-Quesada, Patricio

doi:10.1006/anbe.1999.1234

Cited by 58 publications

(51 citation statements)

References 37 publications

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“…The walling behaviour in adult males during the rutting period may have a sexual function (Ferna´ndez-Llario 2005); the dry mud, mainly clay acts as a protection shield during the fights over the females. Male-male competition for accessing reproduction seems to begin early in life since pregnant females tend to invest more in males than in females foetuses, and also since across litters the heaviest piglet is a male in the large majority of cases (Ferna´ndez-Llario et al 1999;Santos 2002). These results support the Trivers and Willard (1973) model's first prediction, showing that pregnant females in polygynous species tend to invest more in the sex with the higher biotic potential.…”

Section: Introductionmentioning

confidence: 99%

Paternity assessment in free-ranging wild boar (Sus scrofa) – Are littermates full-sibs?

Delgado

Fernández-Llario²,

Azevedo³

et al. 2008

Mammalian Biology

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Multiple paternity within litters occurs in various groups of mammals exhibiting different mating systems. Using seven genetic markers (i.e., microsatellites), we investigated the paternity of littermates in free-ranging wild boar (Sus scrofa) in a Mediterranean habitat. Using the software CERVUS 2.0 we estimated the probability of detecting multiple paternity across all loci (D), the probability of paternity (W) and a statistic D that allows the assignment of paternity to the most likely male with strict and relaxed levels of confidence. Multiple paternity was inferred for one of the nine analysed litters at the 80% confidence level. This suggests that a single male may control the access to receptive adult females and it shows that multiple paternity is not very common in the studied free-ranging wild boar population. Despite the possible occurrence of sperm competition and/or female cryptic choice, mate guarding seems to play a significant role in sexual selection. To better understand the wild boar's mating strategies further studies analysing the reproductive success of both sexes and under different environmental conditions should be conducted.

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Section: Introductionmentioning

confidence: 99%

Paternity assessment in free-ranging wild boar (Sus scrofa) – Are littermates full-sibs?

Delgado

Fernández-Llario²,

Azevedo³

et al. 2008

Mammalian Biology

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“…Most important, the model incorporates the assumption that sibling competition and interactions between intrabrood positions can modify the predictability of conditions for individual offspring, mainly reducing it for low-ranking sibs, but at the same time increasing it for high-ranking sibs. This can explain (1) the presence of runts of any sex, more likely when interactions between siblings/positions are possible, and (2) higher concordance between expected and observed sex at first positions (e.g., Fernández-Llario et al, 1999;Velando et al, 2002). As a consequence, parents should be selected not only to adjust the sex of offspring related to positions, but also to influence the predictability of the resource share at positions, and give up (i.e., weaker selection for sex adjustment) when there is unpredictability and/or low survival expectancies.…”

Section: Environmental Predictability and Offspring Sexmentioning

confidence: 99%

“…In contrast, an increasing number of studies in birds (Ankney, 1982;Badyaev et al, 2002;Bednarz and Hayden, 1991;Bortolotti, 1986;Clutton-Brock, 1986;Ryder, 1983;Velando et al, 2002) and mammals (Gosling et al, 1984;Fernández-Llario et al, 1999;Vanderbergh and Hugget, 1994) have noted that offspring sex is not independent of positions within the brood, and it appears to be associated with the hatching/birth/weight rank in ways that might correlate with some environmental feature at the level of individual offspring.…”

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confidence: 97%

Sex allocation within broods: the intrabrood sharing-out hypothesis

Carranza

2004

Behavioral Ecology

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Selection is expected to cause parents to adjust the sex of their offspring when the environment is predictable during development, and it is expected to affect each sex differently. When several offspring compete for limited resources, the environmental conditions acting on the brood are not a good predictor of the conditions affecting individual offspring. There is evidence for some species that, regardless of any bias in brood sex ratio, the sex of individual offspring within a brood may be related to its position in the hatching/birth/weight rank, in ways that might correlate with the expected share of available resources. Here I propose that parents may be selected to adjust offspring sex within the brood, provided that some depreciable environmental quality is unequally distributed among siblings in a predictable manner. I call this the ''intrabrood sharing-out'' hypothesis and present a graphical model to derive predictions about the relationship between offspring sex and positions within the brood. The model considers that sibling competition not only produces differences in the mean share of resources among siblings, but it also increases the predictability of the share obtained by high-ranking sibs and decreases the predictability of the share for low-ranking ones. Consequently, parents should be selected to deal with such a distribution by promoting the conditions to make it more predictable and then adaptively adjust the sex of particular siblings, especially in high-ranking positions within the brood, rather than to modify the sex ratio of the brood as a whole.

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“…The current study used sows from parity 0 to 6 whose litter sex ratios were numerically, but not significantly, biased toward males, whereas the previous research study used only nulliparous sows whose litter sex ratios were numerically biased toward females. The sex ratios seen in the Jarvis et al study (2006) are atypical as most swine research indicates a small numerical bias toward males (Fernández-Llario et al, 1999;Górecki, 2003;Servanty et al, 2007;Razmaite and Kerziene, 2009;Baxter et al, 2012). The differing results may be attributable to sow parity as greater maternal age has been associated with an increase in the proportion of male offspring in both birds (Blank and Nolan, 1983) and mammals (Côté and Festa-Bianchet, 2001).…”

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confidence: 89%

Growth and reproductive development of male piglets are more vulnerable to midgestation maternal stress than that of female piglets12

Mack

Lay

Eicher

et al. 2014

Journal of Animal Science

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In many mammalian species, prenatal stress masculinizes female and feminizes male offspring impairing their reproductive capacity. Regrouping gestating sows is a common, stressful production practice, but its impact on the developing pigs of the sow is not fully known. This study examined the effects of regrouping gestating sows and the administration of exogenous glucocorticoids on the growth and external reproductive morphology of pigs. At 37.2 ± 0.26 d of gestation, 6 cohorts of 18 sows (N = 108) were placed in 1 of 3 treatments: socially stable (Stable), hydrocortisone acetate (HCA), or mixed (Mixed). The HCA sows were administered 70 mg HCA, a synthetic glucocorticoid, twice daily during the 21 d experimental period. Each Mixed sow was penned with 2 companion sows (Companion) and regrouped on d 7 and 14 with 2 different Companion sows in a new pen. Stable and HCA sows were penned in treatment groups of 3 sows. Sow social rank was assessed weekly during feeding. After the 21 d experimental period, all sows were housed in gestation stalls for the duration of pregnancy. During the 21 d, Companion sows gained more weight than HCA and Mixed sows (P < 0.05) with Stable sows intermediate. High ranked sows gained more weight than middle and low ranked sows (P < 0.05). Mixed sows had greater head lesion scores than Stable and HCA sows (P < 0.05) with Companion sows intermediate. Head lesions increased with lower social rank (P < 0.001). Sow treatment did not affect farrowing rate, litter size, or sex ratio (P > 0.10). Social rank also had no effect on farrowing rate (P > 0.10), but affected total litter size (P = 0.03). High ranked sows bore and weaned more live females than low ranked sows (P < 0.05), in part due to differential preweaning mortality among female pigs (P = 0.01). Only male pigs were affected by sow treatment. Preweaning mortality was higher among male pigs from HCA than from Mixed sows (P = 0.04) with other treatments intermediate. Despite no weight differences in the preweaning period, at 160 d of age males from HCA sows weighed more than males from Stable sows (P = 0.01) with other treatments intermediate. Males born to Companion sows had longer relative anogenital distances, a marker of fetal testosterone exposure, than males from Mixed sows (P = 0.03) with other treatments intermediate. The prenatal environment affected the pigs in a sex-specific manner altering the growth and reproductive morphology of the males more than that of the females. RightsWorks produced by employees of the U.S. Government as part of their official duties are not copyrighted within the U.S. The content of this document is not copyrighted. middle and low ranked sows (P < 0.05). Mixed sows had greater head lesion scores than Stable and HCA sows (P < 0.05) with Companion sows intermediate. Head lesions increased with lower social rank (P < 0.001). Sow treatment did not affect farrowing rate, litter size, or sex ratio (P > 0.10). Social rank also had no effect on farrowing rate (P > 0.10), but affected total litte...

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Sex allocation in a polygynous mammal with large litters: the wild boar

Cited by 58 publications

References 37 publications

Paternity assessment in free-ranging wild boar (Sus scrofa) – Are littermates full-sibs?

Paternity assessment in free-ranging wild boar (Sus scrofa) – Are littermates full-sibs?

Sex allocation within broods: the intrabrood sharing-out hypothesis

Growth and reproductive development of male piglets are more vulnerable to midgestation maternal stress than that of female piglets12

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