Data from: Flexibility, variability and constraint in energy management strategies across vertebrate taxa revealed by long-term heart rate measurements

1) Animals are expected to be judicious in the use of the energy they gain
due to the costs and limits associated with its intake. The management of
energy expenditure (EE) exhibited by animals has previously been
considered in terms of three patterns: the constrained, independent and
performance patterns of energy management. These patterns can be
interpreted by regressing daily EE against maintenance EE measured over
extended periods. From the multiple studies on this topic, there is
equivocal evidence about the existence of universal patterns in certain
aspects of energy management. 2) The implicit assumption that animals
exhibit specifically one of three discrete energy management patterns, and
without variation, seems simplistic. We suggest that animals can exhibit
gradations of different energy management patterns and that the exact
pattern will fluctuate as their environmental context changes. 3) To
investigate these ideas, and for possible large-scale patterns in energy
management pattern, we analysed long-term heart rate data – a strong proxy
for EE – across and within individuals in 16 species of birds, mammals,
and fish. 4) Our analyses of 292 individuals representing 46 539
observation-days suggest that vertebrates typically exhibit predominantly
the independent or performance energy patterns at the across-individual
level, and that the pattern does not associate with taxonomic group.
Within individuals, however, animals generally exhibit some degree of
energy constraint. Together, these findings indicate that across diverse
species, some individuals supply more energy to all aspects of their life
than do others, however all individuals must trade-off deployment of their
available energy between competing functions. This demonstrates that
within-individual analyses are essential for interpretation of energy
management patterns. 5) We also found that species do not necessarily
exhibit a fixed energy management pattern but rather temporal variation in
their energy management over the year. Animals’ energy management
exhibited stronger energy constraint during periods of higher EE, which
typically coincided with clear and key life cycle events such as
reproduction, suggesting an adaptive plasticity to respond to fluctuating
energy demands.