L3 - Animal Energetics 3

Question 1

What effect does body mass have on BMR of an animal?

Answer 1

Increased BMR causes a decrease in BMR per g of animal

Question 2

What is FMR used to estimate?

Answer 2

• the energy requirements of different activities
• the actual food consumption (what resources it needs over time)
• estimate food requirements of a population - including how competition may effect it, and how it would be used for conservation in the future

Question 3

What 4 methods in the wild would you use to measure metabolism?

Answer 3

Time Energy Budget
Doubly labelled water
HR
Accelerometery

Question 4

Briefly describe the method of time energy budget

Answer 4

1. continuously record behaviour and duration total of each
2. give each behaviour an energy value
3. work out energy expenditure

Question 5

Give 3 cons for time energy budget

Answer 5

1. Difficult to perform accurately due to environmental factors, pregnancy/rutting, other factors that effect the MR of an animals
2. MRs of each behaviour need to be known
3. labour Intensive

Question 6

What is a benefit of using time energy budget

Answer 6

Technically easy

Question 7

Describe how doubly labelled water works

Answer 7

Metabolism can be calculated from O2-in/CO2-out.

DLW (‘tagged’) water is traceable hydrogen (deuterium), and traceable oxygen (18O).

Question 8

In DLW, what

Answer 8

The 18O leaves the body in two ways:

1. exhaled CO2, and
2. water loss in (mostly) urine, sweat, & breath.

BUT: the deuterium leaves only in the second way (water loss).

From deuterium loss, we know how much of the tagged water left the body as water. And, since the concentration of 18O in the body’s water is measured after the labelling dose is given, we also know how much of the tagged oxygen left the body in the water.

(A simpler view is that the ratio of deuterium to 18O in body water is fixed, so total loss-rate of deuterium from the body multiplied by this ratio, immediately gives the loss rate of 18O in water.)

Measurement of 18O dilution with time gives the total loss of this isotope by all routes (by water and respiration).

Since the ratio of 18O to total water oxygen in the body is measured, we can convert 18O loss in respiration to total oxygen lost from the body’s water pool via conversion to carbon dioxide. How much oxygen left the body as CO2 is the same as the CO2 produced by metabolism, since the body only produces CO2 by this route.

The CO2 loss tells us the energy produced, if we know or can estimate the respiratory quotient (ratio of CO2 produced to oxygen used).

Question 9

Give 1 pro to using DLW

Answer 9

It is the only one that can be used on very small animals, even as small as bumble bees

Question 10

Give 4 cons to using DLW

Answer 10

1. If fuel calculation is done wrong there can be a big error
2. Not feasible over a short period of time
3. Reduced precision on very active animals
4. Only estimates the mean energy expenditure over the period of time

Question 11

What assumptions are made to use DLW?

Answer 11

• that body water and CO2 fluxes stays the same - body water remains constant
• Isotopes stay in the body water and aren’t absorbed into tissues
• Isotopes can only be lost via H20 and CO2
• CO2 and H20 labelled or unlabelled doesn’t enter the animal via respiratory or skin surfaces
• The isotopes are lost in exactly the same way as their counter parts (the specific activity is the same) (H2O18 is heavier than H2O)