Conservation requirements of a threatened migratory species: the importance of habitat and energetics ti humpback whales

Janelle Braithwaite

    Research output: ThesisDoctoral Thesis

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    Habitat protection is a principle strategy for threatened species conservation management. The effectiveness of this strategy relies on the correct identification of habitats important for species recovery. The challenge here is to evaluate the importance of habitats in relation to their influence on population persistence, such as their role in promoting survival and reproduction. Conservation physiology is an emerging research field that seeks, in part, to quantify the physiological condition of an animal in relation to the habitat it encounters. In doing so, the contribution of habitats to population demography can be assessed, as survival and reproductive success rely to a large degree on the physical condition of an animal. In this thesis, I took a conservation physiology approach to assessing the conservation requirements of humpback whales (Megaptera novaeangliae). These animals engage in annual long-distance migration to breed, supported entirely on stored energy reserves. As they are largely unable to top-up energy stores during the journey, budgeting energy use will be a critical component to the successful completion of migration and reproduction before stores are exhausted. I found that coastal habitats used for resting during the migration journey were associated with conserving energy use and promoting calf growth, driving both the social spacing of resting whale pods, and habitat selection to calmer environmental conditions in resting areas. The quality of foraging habitat was also found to be an important determinant of the initial energy stores of whales commencing their migration. Specifically, annual fluctuations in humpback whale body condition, estimated from whaling records, were linked to sea ice conditoons and prey abundances in the Southern Ocean foraging region of these whales with reductions in sea ice leading to worsening condition of humpback whales. Finally, a bioenergetics model of humpback whale energetics revealed that the optimal migration strategy of whales to minimise energy use reflects average migration velocity and time allocated for resting. Cumulative disturbance to both the activity level of humpback whales and the length of resting time can therefore have adverse effects to energy use and reproductive success. Establishing the energetic link between migrating whales and their habitat use enabled me to evaluate the importance of habitat in relation to populaƟon persistence, and assess the potential impact of disturbance scenarios to demographic outcomes.
    Original languageEnglish
    Publication statusUnpublished - Nov 2014


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