Energetic limits : defining the bounds and trade-offs of successful energy management in a capital breeder
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Judicious management of energy can be invaluable for animal survival and reproductive success. Capital breeding mammals typically transfer energy to their young at extremely high rates while undergoing prolonged fasting, making lactation a tremendously energy demanding period. Effective management of the competing demands of the mother's energy needs and those of her offspring is presumably fundamental to maximizing lifetime reproductive success.How does the mother maximize her chances of successfully rearing her pup, by ensuring that both her pup and herself have sufficient energy during this ‘energetic fast’? While energy management models were first discussed in the 1990s, application of this analytical technique is still very much in its infancy. Recent work suggests that a broad range of species exhibits ‘energy compensation’; during periods when they expend more energy on activity, their bodies partially compensate by reducing background (basal) metabolic rate as an adaptation to limit overall energy expenditure. However, the value of energy management models in understanding animal ecology is presently unclear.We investigate whether energy management models provide insights into the breeding strategy of phocid seals. Not only do we expect lactating seals to display energy compensation because of their breeding strategy of high energy transfer while fasting, but we anticipate that mothers exhibiting a lack of energy compensation are less likely to rear offspring successfully.On the Isle of May in Scotland, we collected heart rate data as a proxy for energy expenditure in 52 known individual grey seal (Halichoerus grypus) mothers, repeatedly across 3 years of breeding. We provide evidence that grey seal mothers typically exhibit energy compensation during lactation by downregulating their background metabolic rate to limit daily energy expenditure during periods when other energy costs are relatively high. However, individuals that fail to energy compensate during the lactation period are more likely to end lactation earlier than expected. Our study is the first to demonstrate the importance of energy compensation to an animal's reproductive expenditure. Moreover, our multi‐seasonal data indicate that environmental stressors may reduce the capacity of some individuals to follow the energy compensation strategy.
Schuert , C , Halsey , L , Pomeroy , P & Twiss , S 2020 , ' Energetic limits : defining the bounds and trade-offs of successful energy management in a capital breeder ' , Journal of Animal Ecology , vol. Early View . https://doi.org/10.1111/1365-2656.13312
Journal of Animal Ecology
Copright © 2020 The Authors. Journal of Animal Ecology published by John Wiley & Sons Ltd on behalf of British Ecological Society. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
DescriptionFunding for this research was provided by the Durham Doctoral Studentship (awarded to C.R.S.) and supported by core funding to the Sea Mammal Research Unit at the University of St. Andrews from the Natural Environment Research Council (NE/RO15007/1 and NE/M01357X/1).
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