Hello Rk; There are two distinct questions here.

1. Small vs large mammal heat loss. Small objects have larger surface/mass ratios than do larger objects. Rates of heat loss are proportional to surface area while heat capacity is proportional to mass. Thus small, warm objects cool faster than large objects do.

2. Biomass contains low-entropy molecules. Whatever carnivores eat contain many of those low-entropy molecules. That energy is what maintains the metabolism of the carnivore.

Best regards, Jim Des Lauriers

Dr James Des Lauriers thank you for your contribution to the discussion

A small body has a relatively large surface area compared to its overall size. Because heat is lost from the surface of the body, small mammals lose a greater proportion of their body heat than large mammals. The relationship between an organism's body size and its metabolic rate. He explains that smaller animals have a larger surface to volume ratio compared to larger animals. This means they lose heat at a much quicker rate. Since animals exchange heat with their environment across their body surfaces, small animals will tend to lose heat to a cooler environment faster than large animals. Body size is a factor because the greater the surface area of the body relative to its mass, the more rapid will be its cooling. If you're relatively petite, not only does a low BMI heighten your response to cold, but so does your overall surface area. Smaller people lose heat more quickly. Larger mammals also have less body surface area for a unit of body mass, and therefore have slower heat loss per kilogram of body mass, in cool environments, than do smaller mammals. The good news is we already have a pretty good idea why large animals often live longer than small ones. It has to do with the fact that tiny animals are more likely to be gobbled up by predators. These animals tend to have babies early and age quickly. Therefore, when the herbivore is eaten by a carnivore, it passes only a small amount of total energy (that it has received) to the carnivore. Of the energy transferred from the herbivore to the carnivore, some energy will be “wasted” or “used up” by the carnivore.The initial energy source is found in the plant. The plant uses initial energy from the sun to convert into chemical energy via photosynthesis. The herbivores eat the plants, ingesting some of the energy from the plant of the energy. The herbivore then becomes prey their energy is transferred to the predator.At the base of the pyramid are the producers, who use photosynthesis or chemosynthesis to make their own food. Herbivores or primary consumers make up the second level. Secondary and tertiary consumers, omnivores and carnivores, follow in the subsequent sections of the pyramid. For each trophic level, only about 10 percent of energy passes from one level to the next. This is called the 10 percent rule. Because of this rule, herbivores only absorb around 10 percent of the energy stored by the plants they eat.

An animal as small as a shrew exhibits massive heat loss through thermal radiation due to its surface area to volume ratio. Max Kleiber in ‘The Fire of Life’ (1961) calculated if a mouse consumed food at the same metabolic requirements of an ox, 20 cm of fur is required to maintain a consistent body temperature.

The surface area (S) of an organism is in proportion to the square of its linear dimensions (l). Thus we have:

SA ∞ l2

On the other hand, volume (V) increases in proportion to a cubic function of its linear dimension:

V ∞ l3

This relationship holds true for any object or organism as it changes size. If we assume an organism as a perfect sphere, and increase its size 10 fold, we increase its surface area 102 (100 times) but its volume increases 103, or 1000 times. Now, lets take a cuboidal cell with a length of 1 unit. The SA of that cube is 6 units2, or 6x1x1 units. However, the V is 1x1x1 or I unit cubed, l3=1x1x1. Thus the SA: volume ratio is 6:1.

However, metabolism is a bit different. It doesn't follow simple Euclidean geometry, as the above is a 0.67 slope. . ‘Kleiber’s Law’ as suggested by Kleiber in ‘Body Size and Metabolism’ suggest a hovering slope of about 0.75. That's not strictly true, but a good rough mean. Mammals a little lower. Thus, a bigger animal, smaller metabolism. Google 'Tusko the Elephant' for a sad demonstration of when scientists really blew it.

An organism brings in chemical energy, in this case, plants or animals. This chemical energy, in the form of molecular bonds, often takes the form of, for example, ATP, further translating to electrical, mechanical or structural. During a transition from one form of energy to another such as chemical to electrical, there is a certain component that is ultimately not completely efficient and some energy is lost through entropy, or the loss of the ability for that energy to do work. In other words, heat production.

p.s. yes, I cut and pasted that...but I wrote it :-)

Hi Curt; Well, you cut and pasted from well-informed sources. :-)

Best regards; Jim Des Lauriers

textbook and website forthcoming :-)

Dr Curt Anderson thank you for your contribution to the discussion

Larger mammals also have less body surface area for a unit of body mass, and therefore have slower heat loss per kilogram of body mass, in cool environments, than do smaller mammals. Body size is a factor because the greater the surface area of the body relative to its mass, the more rapid will be its cooling. Since animals exchange heat with their environment across their body surfaces, small animals will tend to lose heat to a cooler environment faster than large animals. Structural mass involves maintenance costs, reserve mass does not. Hence, small adults of one species respire more per unit of weight than large adults of another species because a larger fraction of their body mass consists of structure rather than reserve. The good news is we already have a pretty good idea why large animals often live longer than small ones. It has to do with the fact that tiny animals are more likely to be gobbled up by predators. These animals tend to have babies early and age quickly. Generally, the smaller the animal, the faster its heart beats. Several studies of human populations around the world indicate that there is a relationship between low birth weight and high blood pressure in adult life. Giraffes' blood pressure is about twice as high as most other animals. The reason small animals often have higher metabolic rates than larger animals are that smaller animals have a higher ratio of surface area to volume. This means that small animals lose body heat faster than larger animals. A small body has a relatively large surface area compared to its overall size. Because heat is lost from the surface of the body, small mammals lose a greater proportion of their body heat than large mammals. Energy is lost with each trophic level, so it takes more of the sun's energy to ultimately produce a pound of meat to feed a carnivore than it does to produce a pound of plants to feed an herbivore. 10% of energy is passed from one trophic level to the next. The next consumer on the food chain that eats the herbivore will only store about 10% of the total energy from the herbivore in its own body. This means the carnivore will store only about 1% of the total energy that was originally in the plant. The reason for this is that only around 10 per cent of the energy is passed on to the next trophic level. The rest of the energy passes out of the food chain in a number of ways: it is released as heat energy during respiration. The average efficiency of energy transfer from herbivores to carnivores is 10%. The initial energy source is found in the plant. The plant uses initial energy from the sun to convert into chemical energy via photosynthesis. The herbivores eat the plants, ingesting some of the energy from the plant of the energy. The herbivore then becomes prey their energy is transferred to the predator.Therefore, when the herbivore is eaten by a carnivore, it passes only a small amount of total energy to the carnivore. Of the energy transferred from the herbivore to the carnivore, some energy will be “wasted” or “used up” by the carnivore.

Surface area- would have been a good question for Conclave