Sexual dimorphism in sea lion pups: differential maternal investment, or sex-specific differences in energy allocation?

Ono, Kathryn A.; Boness, Daryl J.

doi:10.1007/s002650050214

Cited by 83 publications

(55 citation statements)

References 46 publications

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“…Maternal investment can be assessed by examining two phases of the reproductive cycle, gestation and lactation. The cost of gestation can be measured by offspring birth weight (Byers and Moodie, 1990;Ono and Boness, 1996). However, for…”

Section: Discussionmentioning

confidence: 99%

Mother traits and offspring sex in two threatened gazelle species in captivity

Moreno

Ibáñez

Barbosa

2011

Journal for Nature Conservation

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Since threatened species are generally incapable of surviving in their natural environments, ex situ conservation programs are required to preserve them from total extinction. Captive breeding provides the tool to rear sustained populations. Knowledge about biology of such species is critical for managing such breeding programmes. In this paper we look at the sex variation in calves surviving to 30 days in captive populations of two endangered polygynous gazelles, Gazella cuvieri and Gazella dama mhorr. We examined which of the following mother traits may affect sex allocation: her age, experience and inbreeding coefficient. Because twins are quite common in Cuvier's gazelle, we also analyze whether offspring sex is mediated by litter size in this gazelle.In both species the overall sex ratio did not differ from unity at the age of 30 days.These results support the suggestion that for a given population to be in equilibrium, a 1:1 calf sex ratio is to be expected, with females in good condition producing sons and females in poor condition producing daughters. We also found that offspring sex is not significantly related to the same mother traits in the two gazelles studied. Cuvier's gazelle findings showed that only maternal inbreeding influenced offspring sex, the less inbred the mother the higher the probability of producing sons. In contrast, none of the maternal traits studied were related to offspring sex in Mohor gazelle. Two non exclusive explanations are given to justify differences observed between these two species; one relate to a probable differential cost of producing either sex; the other refers to the actual homozygosis level in captive populations of each species. For Cuvier's gazelle litter size has no effect on offspring sex when the sex of the littermate is taken into account. This result fit predictions derived from Trivers-Willard model: mother in good conditions (less inbred) produce the sex with higher fitness returns (i.e., male), no matter if born at single or twins brood. Many variables are likely to affect progeny sex ratio. We have presently examined only a few. But our results might be of interest in management decisions and conservation programs such as reintroductions.

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Section: Discussionmentioning

confidence: 99%

Mother traits and offspring sex in two threatened gazelle species in captivity

Moreno

Ibáñez

Barbosa

2011

Journal for Nature Conservation

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“…For example, prenatal exposure to steroids of maternal origin can permanently affect the sensitivity of growth hormone receptors in male and female embryos to subsequent exposure to steroids and in this way influence growth (Gatford et al 1998;Brandstetter et al 2000). In many animals, the limitation imposed by maternal size on SSD at birth (Mascie-Taylor and Boldsen 1988;Smith and Leigh 1998;Guégan et al 2000) and the bias (or the lack thereof) in provisioning of sons and daughters (Teather and Weatherhead 1988;Holden and Mace 1999;Wilkinson and van Aarde 2001) is a powerful selection pressure on the ontogeny of the larger sex, leading to the evolution of an increased rate and duration of growth as well as adaptations that allow greater sensitivity to (and capitalization on) environmental variation during growth (Ono and Boness 1996;Guinet et al 1999). More generally, maternal effects on growth of sexes are maternal adaptations that represent the outcome of the interaction between maternal modifications of offspring growth potential and offspring counter-adaptations to influence these modifications.…”

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confidence: 99%

The Evolution of Sexual Size Dimorphism in the House Finch. V. Maternal Effects

et al. 2003

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Abstract. The phenotype of a mother and the environment that she provides might differentially affect the phenotypes of her sons and daughters, leading to change in sexual size dimorphism. Whereas these maternal effects should evolve to accommodate the adaptations of both the maternal and offspring generations, the mechanisms by which this is accomplished are rarely known. In birds, females adjust the onset of incubation (coincident with the first egg or after all eggs are laid) in response to the environment during breeding, and thus, indirectly, determine the duration of offspring growth. In the two house finch (Carpodacus mexicanus) populations that breed at the extremes of the species' distribution (Montana and Alabama), females experience highly distinct climatic conditions during nesting. We show that in close association with these conditions, females adjusted jointly the onset of incubation and the sequence in which they produced male and female eggs and consequently modified the growth of sons and daughters. The onset of incubation in newly breeding females closely tracked ambient temperature in a pattern consistent with the maintenance of egg viability. Because of the very different climates in Montana and Alabama, females in these populations showed the opposite patterns of seasonal change in incubation onset and the opposite sex bias in egg-laying order. In females with breeding experience, incubation onset and sex bias in laying order were closely linked regardless of the climatic variation. In nests in which incubation began with the onset of egg laying, the first-laid eggs were mostly females in Montana, but mostly males in Alabama. Because in both populations, male, but not female, embryos grew faster when exposed to longer incubation, the sex-bias produced highly divergent sizes of male and female juveniles between the populations. Overall, the compensatory interaction between the onset of incubation and the sex-biased laying order achieved a compromise between maternal and offspring adaptations and contributed to rapid morphological divergence in sexual dimorphism between populations of the house finch breeding at the climatic extremes of the species range.

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“…Gerber et al (2010) mentioned that both male and female behavior influence population viability in the sea lions. Male aggression may separate mother-pup pairs, affecting nursing (Ono & Boness 1996) or may cause direct mortality of pups due to an increasing in the risk of trampling (Gerber et al 2010). On contrary, female aggression has been observed as a protection behavior of their pups (Le Boeuf & Campagna 1994, Campagna 2002, giving protection directly or by securing higher quality resting and breeding areas (Gerber et al 2010).…”

Section: Discussionmentioning

confidence: 99%

Comparison of behavioral patterns of South American sea lions between breeding and non-breeding seasons

Pérez‐Álvarez¹,

Carrasco²,

Sepúlveda

et al. 2013

Rev. biol. mar. oceanogr.

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Resumen.-Se han descrito tácticas reproductivas para machos y hembras en sistemas reproductivos poligínicos, dentro de las cuales, una respuesta conductual sexo-específico sería esperable para maximizar el éxito reproductivo. El presente estudio da cuenta de un seguimiento conductual del lobo marino común Otaria flavescens durante la época reproductiva (ER) y no reproductiva (ENR) en el Santuario de la Naturaleza Lobería Cobquecura, Chile central. Se registraron patrones conductuales de machos, hembras, juveniles y crías entre mayo de 2008 y diciembre de 2009. Los machos presentaron más registros de conductas asociadas a agresión, desplazamiento y reconocimiento durante ER, mientras que la conducta descanso fue mayor durante ENR. Hembras y juveniles presentaron mayores registros de reconocimiento durante ENR mientras que las otras categorías conductuales no presentaron diferencias entre ER y ENR. Las conductas agresivas por parte de los machos así como las relacionadas al cuidado parental por parte de las hembras podrían ser estrategias conductuales desarrolladas por ambos sexos para asegurar la viabilidad poblacional. Este estudio contribuye al conocimiento de los patrones conductuales reproductivos de la especie y forma parte de uno de los seguimientos conductuales reproductivos más continuos desarrollados en la actualidad en el lobo marino común. Dado que el estudio se realiza en un área protegida dentro del marco legal de Santuario de la Naturaleza, los resultados expuestos serán de utilidad para futuras comparaciones con loberas reproductivas afectadas por actividad antrópica. Palabras clave: Sistema reproductivo poligínico, comportamiento reproductivo, otáridos, Otaria flavescens, ChileAbstract.-In a polygynous mating system males and females have different reproductive strategies; so it is expectable that both sexes have evolved different reproductive behavioral responses to maximize their reproductive success. We analyze the behavior of different sex/age classes of Otaria flavescens during breeding (BS) and non-breeding seasons (NBS) at a Nature Sanctuary breeding colony, central Chilean coast. From May 2008 to December 2009 data of males, females, juveniles and pups were recorded. Males performed more aggression, locomotion and recognizing behaviors during the BS, while they mostly rested during the NBS. Females and juveniles performed more recognizing behavior in the NBS, while the other behavior categories did not show differences between the NBS and the BS. As reproductive behavioral strategies, male aggression and maternal care may increase the overall population viability. This study contributed to a better understanding of the reproductive behavior patterns of this species based on what is to our knowledge the most continuous monitoring of a South American sea lion breeding colony. Since the study has been undertaken in a Nature Sanctuary, the results may be used as a baseline to compare with behavioral data from colonies perturbed by human activities.

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Sexual dimorphism in sea lion pups: differential maternal investment, or sex-specific differences in energy allocation?

Cited by 83 publications

References 46 publications

Mother traits and offspring sex in two threatened gazelle species in captivity

Mother traits and offspring sex in two threatened gazelle species in captivity

The Evolution of Sexual Size Dimorphism in the House Finch. V. Maternal Effects

Comparison of behavioral patterns of South American sea lions between breeding and non-breeding seasons

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