Low on the food chain

Allow me to begin by asking what you think the four organisms below have in common? Diplodocus is in the upper left with the Whale Shark (Rhincodon) to its right. The Blue Whale (Balaenoptera) is on the bottom left and Brachiosaurus is adjacent.

If you thought that these four are some of the largest organisms that have ever existed here on planet Earth you would be right. Another commonality is that these largest-among-the-large are herbivores, or omnivores in the case of the two ocean-goers. The intention of this post is to marvel at these facts and to discuss how it is that such behemoths have always been found to make their living low on the food chain when logic may have suggested otherwise.

To begin to unravel this ecological puzzle one must recognize that the energy which drives all living things ultimately comes from the sun and that the only organisms capable of harnessing this radiant energy are green plants. In ecological terms we call the activities leading to the production of photosynthetic sugars, primary production and the plants that produce them primary producers. Those that make a living by consuming primary producers are called primary consumers (or herbivores), and those that consume primary consumers are secondary consumers, and so on. What’s fascinating about these trophic relationships is that the one-way movement of energy up the trophic pyramid is just 10% efficient. So, the internal combustion engine may be 20% efficient, a rocket engine 70%, an electric motor 85%, and a propane furnace may be more than 95% efficient and I’m telling you that nature, which has had several billion years to work it all out, is only 10% efficient? Right. But why? Because it costs to be an organism. There are costs associated with respiration and egestion and costs of tissues, organs, and structures that don’t transfer to the next trophic level (things like fur, bones, and claws which cannot be assimilated). So the total amount of energy available as primary production declines predictably at each transfer. If, for example, there are 100,000 calories in primary production in a certain patch of ocean, one can expect 10,000 calories in the bodies of primary consumers, which will support 1000 calories in the bodies of secondary consumers, which will ultimately support 100 calories in the bodies of tertiary consumers or top carnivores. The bottom line to our ecological puzzle is that very, very large bodies require very large amounts of energy and these energies are more easily obtained LOW on the trophic pyramid among primary producers and primary consumers. If an organism the size of a Blue Whale were to make the evolutionary shift to strict carnivory it would quickly discover that meeting the energy demands of such a large body wasn’t possible as a top carnivore; dropping to the bottom of the food chain, as it were, allows the omnivorous Blue Whale to more effectively and efficiently feed in what is essentially a continual food stream. [Living Lower on the Food Chain has other ecological implications as well, for human populations especially. But this is a topic for a future post.]

So why do I include the images below? I do so because I wanted to point out that I don’t believe Fay Wray really had to worry that King Kong was intent on consuming her. He wouldn’t have wanted to or even had the necessary dentition. At his monstrous size he was most probably a vegetarian. If Wray was going to worry about anything she should have been worrying about Kong dropping her from such a height. These trophic relations also explain why, in any particular landscape, plants will be most common, herbivores less so, things that eat the herbivores even less so, and big fierce animals will certainly be most uncommon.

9 thoughts on “Low on the food chain

  1. You did a good job of explaining the tendency toward vegetarianism in very large animals, which go right to the source for their nutrition. Maybe it’s my personality, but for as long as I can recall I’ve been wary of trends. I sure saw enough of them over the decades that I taught (mostly math), and even before that I remember being skeptical of the “modern math” that was foisted off on students beginning in around 1960.

  2. I did not have any meat today so I can read this with a clean conscience 🙂 I have seen estimates that the human consumption of meat results in an ecological footprint a factor five times larger than that of the vegan life-style.

    • Absolutely .. and, if I get time, that might be a topic of a future post. Somehow I think that convincing folks to give up their steaks, sausages, and hamburgers will be a tough sell … what do you think? D

      • I am not living vegan or vegetarian myself and am probably less so than the average person. It doesn’t work to patronize people. I don’t like it when green politicians (with whom I would generally agree) try to control and regulate details of our lifestyles. For example, one recent idea: Every “public” canteen (universities etc.) should have one vegetarian-only day per week (as per decree). I believe the main ethical problem is as follows: Why should we – humans living on this planet in 2013 – be more responsible and wiser and more forward-looking than all the generations that came before us? Honestly, although climate protection is imperative it is still very hard to explain to people (particularly in this economic situation) why they should 1) repair what others have done the last 200 years and, 2) consider future generations.

        Sustainable living should become a lifestyle choice associated with something positive (not with regulations) – but I have no idea how this can be achieved.

        • You said it all in your last statement … ‘ Sustainable living should become a lifestyle choice associated with something positive.’ And, I believe that we, as humans, are slowly coming around to the fact that sustainable living is something that makes sense … for individuals, for communities, for countries, and continents, and for the biosphere that we all share. But, perhaps this is an observation of someone living in the developed world and one which totally ignores the realities and difficulties of sustainability in developing economies? Sustainable living is a luxury of the developed world. Perhaps it can only really be achieved when we have a more even global economic playing-field … until then developed countries must carry the burden? A complex topic to be sure. D

      • I have to admit that my first thought, upon reading this was to note, “Pretty sure Dave didn’t take those photos himself!” I enjoyed this, along with the gentle humour, as always.

        About ten years ago I decided to cut way back on my carnivorous habits, but for a different reason. I just noticed that meat was dominating my eating habits and decided that was silly from just about every viewpoint imaginable: ecology, cost, health and, yes, enjoyment.

        • Sometime one of us should compose a post about lifestyle habits and choices and its title should be, “All things in moderation, including moderation.” Fads of all sorts frustrate the heck out of me. If folks would simply be reasonable about the choices they make and the things they do I think we’d all be lots better off. It’s really OK to eat meat … really it is … just not for breakfast, lunch, and dinner. Vegetarianism is really OK too … as long as one does it wisely and is sure to take in a sufficiency of proteins. Moderation and variety … wise choices and thoughtfulness … can all go a very long way toward good health and well being. Now, having said that there are of course genetic predispositions which we cannot ignore. But those, my friend, are a topic for another day. D

          • Indeed! A couple of years ago the whole diet thing came to a head when I noticed two trends that are just plain stupid. The first was that all-meat diet that was supposed to be healthy and the second was the insistence that bread was bad for you. The hype was surrounded by loads of ‘research’ and was presented very straight-faced. All the while, in my little corner, I was thinking, “We’re not tigers, we’re bears. We are omnivores and the best we can do is roll with it.” All the while my thoughts kept coming back to pictures of cigarette ads from the 40’s and 50’s … the ones that portrayed white-coated male doctors insisting that this brand or that filter was actually healthy. Yeah, right. And the same for those diets. Oatmeal or toast contributes to a great breakfast. That, and a nice cup of tea 🙂 And who in their right mind can really say that a sandwich is actually bad for you? Oh my! But then again a crowd of people constitutes a very gullible, malleable thing. Ask any corrupt politician, fire-and-brimstone preacher, or Wall-Street CEO.

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