Reproductive Strategies of Adult Female Weddell Seals (Leptonychotes weddellii) and Their Implications for Pup Survival
Life history strategies reflect variation in the allocation of an individual's resources (i.e., time, effort and energy expenditure) to competing life functions such as growth, survival and reproduction. For mammals, producing milk is one of the most energetically expensive activities for femal...
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| Format: | Thesis |
| Language: | unknown |
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2007
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| Online Access: | https://doi.org/10.25959/23211662.v1 https://figshare.com/articles/thesis/Reproductive_Strategies_of_Adult_Female_Weddell_Seals_Leptonychotes_weddellii_and_Their_Implications_for_Pup_Survival/23211662 |
| Summary: | Life history strategies reflect variation in the allocation of an individual's resources (i.e., time, effort and energy expenditure) to competing life functions such as growth, survival and reproduction. For mammals, producing milk is one of the most energetically expensive activities for females, so factors determining its delivery to offspring essentially define the reproductive strategy a species evolves. The efficiency with which energy is transferred via milk also determines the reproductive investment trade-off that exists between survival and future reproduction. The key objective of this study was to examine physiological aspects of lactation in Weddell seals (Leptonychotes weddellii), to gain a better understanding of reproductive strategies of an upper trophic level predator that must cope with unpredictable food availability in an extreme and highly variable environment. Female body mass (and absolute body fat) at parturition differed between the two years of study and this difference appeared to drive the length of the lactation period, maternal energy expenditure, pup mass gain and weaning mass. Effects were more marked in smaller individuals that did not increase energy expenditure to reconcile this disparity. Milk composition was independent of maternal post-partum mass (MPPM) and condition, but did change over lactation. Protein tripled from post-partum (PP) to end-lactation (EL) while lipid and energy increased to mid-lactation (ML) then slightly decreased. This pattern of changes may be related to the relatively long lactation period demonstrated by this species and the energetic and physiological needs of the mother and pup. There was evidence through both milk energy output and fatty acid transfer that feeding occurred in some individuals later in lactation. A major source of energy during lactation is provided through the mobilisation of blubber fatty acids (FA). I investigated the extent to which FA were mobilised to support both maternal metabolic requirements and milk production, and how ... |
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