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Humpback Madagascar

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Maria-Alejandra Faria
added 3 research items
La population de baleine à bosse de l'ouest de l'océan Indien a été appelée stock C par la Commission Baleinière Internationale (CBI, http://iwc.int/). Pendant la période de reproduction, son aire de distribution se dessine de la côte est de l'Afrique à l'archipel des Mascareignes (Report of the Scientific Committee of the IWC, 1998). Ce stock se divise en 3 sous-régions (Best et al., 1998) : C1 (côte est de l'Afrique du Sud au Mozambique), C2 (canal du Mozambique jusqu'à l'archipel des Comores), C3 (eaux côtières de Madagascar). A ces trois sous-régions, a été proposée une 4 ème qui comprend l'île de la Réunion et l'île Maurice (IWC, 2008a). La dynamique, les échanges et le chevauchement entre ces sous-stocks sont complexes et mal compris (Cerchio et al., 2008; Fleming and Jackson, 2011). La proximité géographique et les échanges observés entre ces différentes régions remettent en cause aujourd'hui la délimitation de ces sous-stocks (Rosenbaum et al., 2009,; Ersts et al., 2011,). Nous avons initié un projet pluridisciplinaire dont l'objectif est de mieux renseigner la répartition géographique des baleines à bosse autour de Madagascar ainsi que leurs habitats. Ce projet, intitulé projet BaoBaB, est basé sur des observations visuelles (photo-identification) et acoustiques (déploiement d'un réseau d'hydrophones dans le canal Ste Marie, Madagascar) et des suivis par balise Argos (12 balises ont été posées en juillet-aout sur des individus évoluant sur la côte nord-est de Madagascar). Toutes ces données sont complétées par des campagnes de prélèvements de biopsies afin de permettre des analyses de génétique.
Skin lesions occur frequently among many cetacean populations across the globe. Causes and consequences in the long term and skin conditions prevalence have been poorly studied in mysticete whales among the Indian Ocean region (Banks et al, 2011). Methods to examine cetacean's skin lesions have relied on photo-identification, stranding, and by-catch data. The current preliminary study used photo-id data from three humpback whales (Megaptera novaeangliae) seasons in Ste Marie, Madagascar from 2009 to 2011, as well few Photo IDs recovered from 2005 and 2008 were analyzed adding up to 1 290 photos reviewed. Skin lesion prevalence and type occurring on the population sampled were estimated. The present study found 58 individuals (clinical cases) with one or more occurrences (57 cases on humpback whales and 1 case on Tursiops aduncus); detected lesions were subsequently classified into 11 different categories for skin conditions and 4 body possible conditions according to descriptions in Castro et al, 2008 modified by this study. There were 29 occurrences of skin conditions and 26 incidents of body anomalies in our sample. Conditions could be found on all parts of the body and some individuals had multiple conditions. Eleven clinical cases had more than one occurrence of anomaly. The prevalence of lesions was highest among humpback whales occurring in 2011 (1.2%) and lowest in the ones occurring in 2010 (0.6%). This study demonstrated that photo-id data offer a non-invasive, cost-effective approach to study disease in wild cetacean populations. Further, while many skin diseases are not considered fatal, lesions detected on free-ranging animals may serve as indicators of other health concerns or environmental threats. We hope this study contributes to better knowledge and understanding of certain diseases and abnormalities in cetaceans and their environment in the Western Indian Ocean Region.
Humpback whales (Megaptera novaeangliae) feed at high latitudes and migrate to low latitudes to breed. During the austral winter, humpback whales from the C-stock population migrate from their feeding ground in Antarctica to breeding grounds in the Indian Ocean (Rosenbaum et al., 1997). The C3 subpopulation was estimated to be 2,532 indi-viduals in 1994 (Reilly et al., 2008), and between 4,936 and 8,169 in 2009 (Reilly et al., 2008). Humpback whales conceive during the wintering months or en route and have a gestation period of 11 to 12 mo (Craig et al., 2003). The coastal waters of Sainte Marie, an island off the northeast coast of Madagascar, are a well-known calving and breed-ing ground for this humpback whale subpopulation (Cartwright & Sullivan, 2009). We report a sighting of a humpback whale birth in the southern waters of Ste Marie Island that took place on 30August 2010. Observations and documented records of ceta-ceans’ births are scarce; so far, births of six ceta-cean species have been reported in the wild: the killer whale (Orcinus orca) (Jacobsen, 1981; Stacy & Baird, 1997), sperm whale (Physeter macro-cephalus)(Weilgart & Whitehead, 1986), beluga (Delphinapterus leucas) (Beland et al., 1990), false killer whale (Pseudorca crassidens) (Notarbartolo diSciara et al., 1997), right whale (Eubalaena glaci-alis) (Zani et al., 2008), and gray whale (Eschrichtius robustus) (Balcomb, 1974; Leatherwood & Beach, 1975; Mills & Mills, 1979). However, no observa-tions of humpback whale births have been docu-mented and very little is known about newborns and the behaviours associated with birth, despite the fact that this species is widely studied. This is the first account of a humpback whale birth observation and the paper will deal with two main aspects: (1) the behaviour of the escorts and the mother before, during, and after the birth; and (2) the morphology and behaviour of the newborn.The birth event was observed from a small whale-watching vessel (8 m long) within a 2km radius off the southwest coast of Ste Marie Island where the water depth ranged between 20 to 50 m (Figure 1). The behaviour of the group comprising the mother and the newborn was recorded adopting focal follow sampling techniques, noting the GPS locations and time of encounters (Altmann, 1974). The humpback whales encountered during the birthing event were arbitrarily assigned the follow-ing lettering for ease of description: the nuclear animal (female whale) was named NA; the primary escort whale, PE; the secondary escort whale, SE; and the other escorts (challengers C) were assigned letters in alphabetical order commencing with D according to their relative place in the group. The mother was defined by her proximity to the calf. A calf is defined as an individual having 1⁄3 to 1⁄2 of the total length of its mother (Tyack & Whitehead, 1983; Spitz et al., 2002).