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On colony behaviour of Sea Lions (Otaria flavescens): mother-pup recognition
De Pooter, D. (2007). On colony behaviour of Sea Lions (Otaria flavescens): mother-pup recognition. MSc Thesis. Vrije Universiteit Brussel: Brussel. 114 pp.

Thesis info:
    Vrije Universiteit Brussel; Vakgroep Biologie; Laboratorium voor Ecotoxicologie en Polaire Ecologie (ETOX), more

Available in Author 
    VLIZ: Non-open access 213167
Document type: Dissertation

    Colonies; Maternal behaviour; Otaria flavescens Shaw, 1800 [WoRMS]; PSW, Argentina, Rio Negro; Marine

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  • De Pooter, D., more

    Mothers of colonial breeding South American sea lions (Otaria flavescens) regularly reunite promptly with their pup, after sometimes days of absence, making foraging trips at sea. This performance is astonishing, as during the absence of their mothers, pups may move over considerable distances within a colony with hundreds of other pups. There appears to be little confusion about which pup belongs to a mother and adoption is absent or rare. Using behavioural observations we investigated the means by which female South American sea lions identified their pups in the colony of more than 4000 animals of Punta Bermeja, Rio Negro, Argentina, from January 22 to February 13: 3 weeks during the lactation period. The importance of vocal, visual, olfactory and spatial cues in the reunion process was investigated and it was examined how these behaviours are related to search context and success. Females that returned from sea, probably from foraging trips, were followed throughout their search, which resulted in 73% of the 118 cases in a reunion. The search behaviour of the female proved to be important to achieve reunions. The search success rate was increased when females were larger, maintained a high call rate, a high sniff rate, a high visual rate, a high pups-encountered rate and didn’t sniff allopups. It also proved to be increasingly beneficial to move around in the colony with increasing search duration. Of these behavioural variables a high call rate was shown to be the most important. Mothers call to elude a response of their pup and to attract them. The likelihood of this response is thought to increase with increasing call rate. Successful females with a high call rate have a shortened search duration, but the call rate stays stable during the entire search. A female makes a visual when she makes the, typical nose in the air posture, and appears to turn her head to look in different directions. This posture may serve as a visual signal towards her pup that she is looking for it and may therefore work as an attractant for (allo)pups. Larger, probably older and more experienced females increase their search success rate by increasing their pups-encountered rate thereby also their sniff rate. They seem to have done this by increasing their visual rate, which may be more efficient due to their increased size. But not by increasing their call rate and they were also not more likely to move. A drop in success rate was observed when the number of animals, close to the end point of the search, rose above 30 animals. This increase in density was correlated with a drop in call rate and a slightly increased disturbance rate by females. The decreased success rate of females that sniffed allopups could be explained by an increased search duration and thus an increased number of encountered (allo)pups. The female always sniffed the pup before accepting it.

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