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- Mother knows best: occurrence and associations of resighted humpback whales suggest maternally derived fidelity to a southern hemisphere coastal feeding groundPublication . Barendse, Jaco; Best, Peter B.; Carvalho, Inês; Pomilla, CristinaSite fidelity is common among migratory cetaceans, including humpback whales (Megaptera novaeangliae). In the Northern Hemisphere it has been found that fidelity to humpback whale feeding grounds is transferred maternally but this has never been shown for the species in the Southern Hemisphere. We examined this in a unique feeding area off west South Africa using resighting data of 68 individually identified humpback whales by means of photographic (tail flukes and dorsal fins) and/or molecular methods (microsatellite genotyping) over an 18 year span. We found short-term association patterns and recurrent visits typical of other feeding grounds. Males and females had different seasonality of attendance. Significant female-dominated presence corresponded to timing of an expected influx of females on their southward migration from the breeding ground: firstly non-nursing (possibly pregnant) females in mid-spring, and mothers and calves in mid-to late summer. The potential benefit of this mid-latitude feeding area for females is illustrated by a record of a cow with known age of at least 23 years that produced calves in three consecutive years, each of which survived to at least six months of age: the first record of successful post-partum ovulation for this species in the Southern Hemisphere. We recorded association of a weaned calf with its mother, and a recurring association between a non-lactating female and male over more than two years. Moreover, three animals first identified as calves returned to the same area in subsequent years, sometimes on the same day as their mothers. This, together with numerous Parent-Offspring relations detected genetically among and between resighted and non-resighted whales is strongly suggestive of maternally derived site fidelity at a small spatial scale by a small sub-population of humpback whales.
- Population structure of humpback whales (Megaptera novaeangliae) in west coast of AfricaPublication . Carvalho, Inês; Rosenbaum, Howard; Cancela, LeonorA baleia corcunda (Megaptera novaeangliae) é uma das espécies mais conhecidas e mais facilmente identificáveis das grandes baleias. Tal como os outros misticetos, as baleias corcunda têm um ciclo de vida marcadamente sazonal, passando o Inverno em águas costeiras quentes nos trópicos, onde acasalam e têm as crias, migrando depois para zonas frias de grande produtividade onde se alimentam. No hemisfério sul ocorrem várias populações de baleias corcunda. O presente trabalho contribui para um maior conhecimento da biologia e estrutura populacional das baleias corcunda que ocorrem na costa oeste africana (stock B - Comissão Baleeira Internacional) desde o Golfo da Guiné (região B1) até à Africa do Sul (região B2). Foi utilizada uma abordagem metodológica multidisciplinar, tendo por base estudos a nível local e regional, focando sobretudo aspectos ligados aos padrões temporais e espaciais desta população. Com base num extenso conjunto de dados de ADN mitocondrial e microssatélites, verificou-se a existência de uma estruturação tanto a nível temporal como espacial entre as duas regiões. Surgiram igualmente vi diferenças ao nível da fidelidade ao local e no sex ratio. Mais, os animais que estão presentes durante os meses de Verão na costa oeste da África do Sul são os que mais contribuem para esta diferenciação. Em conjunto, estas evidências sugerem que uma parte das baleias que se alimenta na África do Sul pertence a uma área de reprodução desconhecida. A importância da temperatura da superfície do mar na distribuição destes animais nesta área foi demonstrada a nível local e regional. Este estudo descreveu ainda, pela primeira vez, as características das baleias corcundas na ilha de São Tomé e descobriu que esta região é utilizada sobretudo por pares mães-cria, como zona de nascimento ou descanso, facto que sugere que esta pode ser uma zona importante do ponto de vista da conservação nesta região.
- The waters of São Tomé: a calving ground for West African humpback whales?Publication . Carvalho, Inês; Brito, C.; dos Santos, M. E.; Rosenbaum, H. C.In the Southern Hemisphere, humpback whales Megaptera novaeangliae feed in Antarctic waters during the austral summer and migrate to their breeding grounds in subtropical and tropical waters during the winter. Historical whaling records suggest that the Archipelago of Sao Tome and Principe, located in the Gulf of Guinea, serves as a possible breeding ground. In order to investigate the temporal occurrence and group composition of humpback whales around Sao Tome Island, annual surveys were conducted during the breeding season between 2002 and 2006. A total of 186 boat-based surveys took place during this period. Data collected during each sighting included geographical positions, group size, group composition and behavioural classifications. Of the 66 groups encountered, mother/calf pairs made up a large proportion (65.15%), followed by solitary individuals (15.15%). Mother/calf pairs were seen in the region into November and resightings of identified animals indicate periods of occupancy that extended over three weeks. Few behaviours typically associated with mating activity were observed. Given the high percentage of mother/calf pairs, sometimes with very young calves, and the low frequency of mating activity, the waters of Sao Tome may primarily serve as a calving and nursing or resting area for humpback whales.