A model on female breeding dispersion and the reproductive systems of pinnipeds

Cassini, Marcelo H.

doi:10.1016/s0376-6357(00)00121-2

Cited by 46 publications

(48 citation statements)

References 13 publications

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“…En este sentido, en Isla Guafo en comparación con las colonias de Perú y Uruguay, el efecto ecológico de machos periféricos sobre las agrupaciones reproductivas son despreciables tanto a nivel intraespecífico como interespecífico (observación personal. ), condición que disminuiría la agregación de las hembras en torno a un macho dominante protector (Cassini 2000). A su vez, la topografía de las playas en Isla Guafo y el mayor espacio disponible para el establecimiento de las agrupaciones reproductivas también permitirían entender el menor número de hembras por machos y con ello la identificación de un menor nivel de poliginia entre los Otariidae.…”

Section: Discussionunclassified

Temporada reproductiva del lobo fino austral, Arctocephalus australis (Zimmerman, 1783) en la Isla Guafo, Chiloé, Chile

Pavés¹,

Schlatter

2008

Rev. chil. hist. nat.

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A lo largo del litoral sudamericano se registran ejemplares del lobo fino austral (Arctocephalus australis), especie que al establecerse en una amplia área de distribución, presentaría una marcada sincronización reproductiva y un fuerte efecto latitudinal sobre sus patrones reproductivos. En este trabajo se revisarán los patrones reproductivos de A. australis en Isla Guafo (43º33º S, 74º51' O, Chile), determinando existencia de una sincronización y estabilidad temporal en los partos, cópulas y en la estacionalidad de los territorios durante dos temporadas reproductivas consecutivas. Se determinó la presencia de machos territoriales desde mediados de noviembre a principios de febrero, registrándose el máximo para ambas temporadas, durante la cuarta semana de diciembre. El periodo de sincronización de pariciones, se estimó entre la primera y cuarta semana de diciembre con una duración promedio de 28,5 ± 2,1 días. La fecha media de partos, se estimó el día 15,5 de diciembre. La fecha media de cópulas se registró el día 19 ± 1,4 de diciembre con un periodo de sincronización de 29 ± 4,2 días de duración. Empleando la fecha media de cópulas y partos, se estimó un ciclo reproductivo cercano a 11 meses y 27 días para la especie en Guafo. Solo se determinaron diferencias estadísticamente significativas para la fecha del máximo de partos entre temporadas, no así para las cópulas ni la estacionalidad de los territorios. Fue posible determinar estabilidad en el tamaño poblacional y estructura etaria, no así en el índice de poliginia HPMT. Aunque se determinó una diferencia estadística en la fecha de pariciones, fue posible identificar una marcada estacionalidad y sincronización reproductiva para la especie (cerca de 30 días). Conjuntamente, se determinó que los patrones reproductivos evaluados presentaron una estabilidad temporal en el sector, condición compartida con el resto de Otáridos de ambientes templados. Mediante comparación de los resultados obtenidos, con aquellas presentados para Sudamérica, se evidenciaron diferencias cercanas a 30 días en la fecha de partos, cópulas y establecimiento de los territorios. Esta información debe ser actualizada con urgencia para entender con ayuda de las herramientas filogeográficas la historia ecológica y evolutiva de esta especie en el Neotrópico. Palabras clave:Arctocephalus australis, patrones reproductivos, sincronización reproductiva, poliginia. ABSTRACTThe southern fur seal (Arctocephalus australis) has colonised an ample geographic coverage in South America. The population should present there reproductive synchronization and a strong latitudinal effect on its reproductive activities. This research intends to review those reproductive activities on Guafo island (43º33' S, 74º51' W, Chile) looking after the existence of synchronization and stability during successive breeding seasons, considering birthing, mating and territorial seasonality. During both seasons we observed territorial males from the end of November to beginning of February, counting most of them during the 4...

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Section: Discussionunclassified

Temporada reproductiva del lobo fino austral, Arctocephalus australis (Zimmerman, 1783) en la Isla Guafo, Chiloé, Chile

Pavés¹,

Schlatter

2008

Rev. chil. hist. nat.

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“…A recent model to explain the distribution of pinnipeds (Cassini 2000) predicts that females would form denser aggregations than expected according to the distribution of resources to minimise male harassment through dilution. However, the costs of female competition would reduce the size of breeding groups that maximises breeding success.…”

Section: Discussionmentioning

confidence: 99%

Intra-sexual female agonistic behaviour of the South American sea lion (Otaria flavescens) in two colonies with different breeding substrates

Fernández‐Juricic

Cassini

2007

acta ethol

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Female agonistic behaviour during pregnancy and lactation is common in several pinnipeds and has been associated to pup or territory defence. Previous studies on female agonistic behaviour in pinniped breeding groups have not usually considered the number of females per breeding group, which could influence the degree of aggressiveness. We compared female agonistic behaviour (open-mouth displays and bites) within two colonies with different breeding substrates (homogeneous, Punta Norte; heterogeneous, Pirámide) of South American sea lions using two methods: weighted means and general linear models. We found that both aggressive interaction rates were significantly affected by female density, which accounted for a greater proportion on the variability in bite rates than in open-mouth rates. Controlling for the number of females, we found with both methods that open-mouth rates were higher than bite rates within the Pirámide colony; however, no differences were found within the Punta Norte colony. In Pirámide, open-mouth rates could be used more often as threats to minimise the chances of more severe aggressions. The conclusion is that females vary their use of agonistic interactions in relation to their density in the colony with heterogeneous substrate, which may be related to the presence of limited numbers of tide pools that heightens competition for thermoregulatory resources.

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“…Therefore, even when a female in a group can reduce harassment by satellite males, it can suffer from harassment by the dominant male. Female gregariousness can reduce this harassment by resident males by two mechanisms: (1) the 'dilution effect' (Hamilton 1971) that reduces the probability of female interactions with the resident male as breeding group size increases or (2) because resident males that own large female groups are less harassing (Cassini 1999(Cassini , 2000. Males in large groups can show fewer interactions with females because they need to dedicate time in other activities (e.g.…”

Section: Introductionmentioning

confidence: 99%

Sexual harassment and female gregariousness in the South American sea lion, Otaria flavescens

Cappozzo

Túnez

Cassini

2008

Naturwissenschaften

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Most colonial pinnipeds form extreme clusters of breeding females that cannot be entirely explained by the distribution of sites for reproduction. Avoidance of male harassment has been postulated as an important determinant of reproductive aggregation in this group of mammals. Female gregariousness can reduce harassment by resident males by two mechanisms; directly by the 'dilution effect' or indirectly because resident males that defend large female groups are less harassing. In order to investigate the relationship between male harassment and female gregariousness in relation to the size of breeding groups, we analysed the behaviour of dominant males and their females in a breeding colony of Otaria flavescens. Females in large breeding groups received less harassment by resident males due to dilution effects and because males that defended a large group interacted less frequently with females than males with small groups.

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A model on female breeding dispersion and the reproductive systems of pinnipeds

Cited by 46 publications

References 13 publications

Temporada reproductiva del lobo fino austral, Arctocephalus australis (Zimmerman, 1783) en la Isla Guafo, Chiloé, Chile

Temporada reproductiva del lobo fino austral, Arctocephalus australis (Zimmerman, 1783) en la Isla Guafo, Chiloé, Chile

Intra-sexual female agonistic behaviour of the South American sea lion (Otaria flavescens) in two colonies with different breeding substrates

Sexual harassment and female gregariousness in the South American sea lion, Otaria flavescens

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