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Metabolism calculators
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metabolism = a Mb
(where a is the mass coefficient, M is mass, and b is the mass exponent)
This example shows an estimate of the resting metabolic rate (RMR) of
a 37.3 g bird, in units of ml O2/min.
The equation was derived from a paper published by Andrew Mckechnie and
Blair Wolf (Click here for a list of the references from which allometric equations were obtained.).
Note that the mass coefficient ('a' value)
and mass exponent are shown and can be edited, and that mass can be in either grams or kilograms. Also, it is possible
to make corrections for the effect of body temperature by making the appropriate
adjustments to the value of Tb and
Q10 (in this example, the 'base' Tb,
from which the equation was derived, is equal to the current Tb
so no temperature correction occurs). After changing values in the
edit fields, click the 'Compute' button to display the new results.
The 'Store' button 'remembers' the computed metabolism for later use (for example in other calculators). The 'Save' button, if present, lets you save the current mass coefficient and mass exponent values for future use, accessed as 'Custom coefficent and exponent' option in the Taxon popup. The 'Save' button is accessible only if the units are set to ml O2/min. NOTE: you will have to click the 'Save Current Preferences' button in the Preferences window if you want to have your custom values available the next time you run the program.
This window calculates the washout rates of theoretical perfectly-mixed chambers as a function of volume and flow rate. The computed value is the time for X% of intial gas volume to be replaced -- akin to the 'half-life' concept for radioactive decay and related phenomena. back to top
To support these calculations -- which are largely based on the small pressure fluctuations induced by the warming and wetting of tidal air -- you need to provide a number of variables. Several of these are self-explanatory (at least if you know something about respiratory physiology). Abbreviations for some of the more obscure ones are:
You can use the 'waveform analysis' routines in the ANALYSIS menu to obtain breathing frequeny, calibration volts, and sample volts from recorded breathing records.
In this fairly typical example, the animal (a mouse) breathed about 6.3
times per second (not unusual for a small mammal in cold conditions) and
had a tidal volume of 0.256 ml and a minute volume of about 97 ml/min. The
oxygen extraction was about 25.7%.
For each point in the data file, the necessary metabolic rate is computed according to the following rules: When Te < LCT in the inactive part of the daily cycle, if the animal can use torpor (selected in the 'options' window), one of two calculations are performed:
-- if Te is at or above 1 °C less than a minimal (defended) Tb, the metabolic rate is reduced from BMR in proportion to how close Te is to minimum Tb.
Flowcharts (decision trees) for calculations of environmental temperature and thermoregulatory costs are at the end of this page.
Program output includes:
These thermal calculations are performed in one of two ways:
Multiple individuals (species) in a spreadsheet
The program always saves a column containing the mean thermoregulatory cost in watts. Other thermoregulatory data columns to be placed in the spreadsheet are selected from the window at right:
Times are computed using the ‘Sunrise equation’; this example shows an annual day length cycle for a tropical latitude (~ 14 ° south).
This flowchart shows how Te, time, and physiological parameters are used to compute thermoregulatory energy costs:
Although there are a lot of data to enter,
the program makes it as easy as possible. Most values are remembered
between successive uses of the calculator, so you only have to change a
few edit fields (like VO2, frequency, and
sample volts). You can tab (or hit return) to move between successive
edit fields.
Important cautions:
Thermoregulatory costs are calculated using the following thermal parameters: body temperature (Tb), lower critical temperature (LCT), thermal conductance (Cth; watts/°C), and basal metabolic rate (BMR; ml O2/min or watts; selected in the 'options' window) in a set of edit fields. The program also asks for a channel containing time of day in hours (0-24) and two channels containing environmental temperatures (Te), one for shade and one for sun. Note: If shade temperature is missing, the program can substitute sun temperature (if available), but only at night. If sun temperature is missing, the program can substitute shade temperature (if available). Select these settings in the Data Rejection Rules component of the Thermoregulatory Cost Options menu.
Note that if you have only one temperature measurement, or if a day-active species never has access to sunlight (e.g., stays in deep shade), you can select the shade temperature as the sun temperature (in other words, use the shade temperature measurement twice.
-- if Te is lower than 1°C below the minimum Tb, metabolic rate is computed as: (minimum Tb - Te) * Cth
-- NOTE: the torpor algorithms do not include the energy cost of warmup.
NOTE: For nightime data, if a value for shade temperature is missing, the program will attempt to use the sun temperature value instead. This substitution does not occur for daytime data.
Optionally, the computed costs for each entry in the main data file can be saved in a new channel (if the file has < 40 channels).
For both methods, the 'options' button opens a window where you can select a number of alternate ways of handling data and calculations, including:
For each spreadsheet entry, the program runs through the Te channels from the main data file. The combined results can be saved, along with the raw data from the 'source' .csv file, in a user-selected spreadsheet file.
This flowchart shows how environmental temperature (Te) is selected:
Note that if you elect to NOT allow torpor use, that restriction will apply globally to all entries in a .csv file. If you DO allow torpor use, each entry in a .csv file will indicate whether or not torpor is applicable to that entry.
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