TY  - JOUR
A1  - Sibly, Richard M.
A1  - Grimm, Volker
A1  - Martin, Benjamin T.
A1  - Johnston, Alice S. A.
A1  - Kulakowska, Katarzyna
A1  - Topping, Christopher J.
A1  - Calow, Peter
A1  - Nabe-Nielsen, Jacob
A1  - Thorbek, Pernille
A1  - DeAngelis, Donald L.
T1  - Representing the acquisition and use of energy by individuals in agent-based models of animal populations
JF  - Methods in ecology and evolution : an official journal of the British Ecological Society
N2  - Agent-based models (ABMs) are widely used to predict how populations respond to changing environments. As the availability of food varies in space and time, individuals should have their own energy budgets, but there is no consensus as to how these should be modelled. Here, we use knowledge of physiological ecology to identify major issues confronting the modeller and to make recommendations about how energy budgets for use in ABMs should be constructed. Our proposal is that modelled animals forage as necessary to supply their energy needs for maintenance, growth and reproduction. If there is sufficient energy intake, an animal allocates the energy obtained in the order: maintenance, growth, reproduction, energy storage, until its energy stores reach an optimal level. If there is a shortfall, the priorities for maintenance and growth/reproduction remain the same until reserves fall to a critical threshold below which all are allocated to maintenance. Rates of ingestion and allocation depend on body mass and temperature. We make suggestions for how each of these processes should be modelled mathematically. Mortality rates vary with body mass and temperature according to known relationships, and these can be used to obtain estimates of background mortality rate. If parameter values cannot be obtained directly, then values may provisionally be obtained by parameter borrowing, pattern-oriented modelling, artificial evolution or from allometric equations. The development of ABMs incorporating individual energy budgets is essential for realistic modelling of populations affected by food availability. Such ABMs are already being used to guide conservation planning of nature reserves and shell fisheries, to assess environmental impacts of building proposals including wind farms and highways and to assess the effects on nontarget organisms of chemicals for the control of agricultural pests.
KW  - bioenergetics
KW  - energy budget
KW  - individual-based models
KW  - population dynamics
Y1  - 2013
U6  - https://doi.org/10.1111/2041-210x.12002
SN  - 2041-210X
VL  - 4
IS  - 2
SP  - 151
EP  - 161
PB  - Wiley-Blackwell
CY  - Hoboken
ER  - 
TY  - JOUR
A1  - Martin, Benjamin T.
A1  - Jager, Tjalling
A1  - Nisbet, Roger M.
A1  - Preuss, Thomas G.
A1  - Grimm, Volker
T1  - Predicting population dynamics from the properties of individuals - a cross-level test of dynamic energy budget theory
JF  - The American naturalist : a bi-monthly journal devoted to the advancement and correlation of the biological sciences
N2  - Individual-based models (IBMs) are increasingly used to link the dynamics of individuals to higher levels of biological organization. Still, many IBMs are data hungry, species specific, and time-consuming to develop and analyze. Many of these issues would be resolved by using general theories of individual dynamics as the basis for IBMs. While such theories have frequently been examined at the individual level, few cross-level tests exist that also try to predict population dynamics. Here we performed a cross-level test of dynamic energy budget (DEB) theory by parameterizing an individual-based model using individual-level data of the water flea, Daphnia magna, and comparing the emerging population dynamics to independent data from population experiments. We found that DEB theory successfully predicted population growth rates and peak densities but failed to capture the decline phase. Further assumptions on food-dependent mortality of juveniles were needed to capture the population dynamics after the initial population peak. The resulting model then predicted, without further calibration, characteristic switches between small-and large-amplitude cycles, which have been observed for Daphnia. We conclude that cross-level tests help detect gaps in current individual-level theories and ultimately will lead to theory development and the establishment of a generic basis for individual-based models and ecology.
KW  - population dynamics
KW  - dynamic energy budget theory
KW  - bioenergetics
KW  - individual-based model
Y1  - 2013
U6  - https://doi.org/10.1086/669904
SN  - 0003-0147
VL  - 181
IS  - 4
SP  - 506
EP  - 519
PB  - Univ. of Chicago Press
CY  - Chicago
ER  -