This is a great thread, as many of paralleled nature before it have been. It seems likely that many will miss (and are missing) the greater implications of it on behalf of the same misconceptions that have plagued the givers of captive diet adaptations for many years.



Nutritional needs are complicated, but break down most simply into mandatory amounts of glycogen and glucose (sugars) used for metabolism and other activities plus minerals and vitamins that support other systemic functions. The most interesting thing about this in relation to animal behavior is how they go about achieving the precursors (food) for those molecules.



Most on this forum seem to be in agreement that monitors are opportunists when it comes to diet. The genesis of this thread is with regards to that, but, downplaying any absolute necessity for varied diet. Monitors across the genus (or genera) seem universal in eating almost any animal they come across that might fit down the hatch. The group has adapted in accordance with being able to swing this. The first monitors were dietary opportunists, or they were not. Then as years progressed, they stayed dietary opportunists or they changed to become dietary opportunists. Either way, their systems are presently honed to achieve their nutritional requirements from many different organisms. Although there are many different monitor ecomorphs, they all still eat whatever is available to them (at least insofar as captives show). Remember, dietary opportunists are just dietary generalists that are very good at what they do whether they’re specialized in other ways or not.



The confusion for most seems to be coming from the angle, this variety is where the required nutrition comes from. Variety does not equal the nutrition monitors or most other successful dietary opportunists need, it only equals the various channels through which those nutritional needs can be met, i.e., whole prey (or mostly-whole prey). To feed many different kinds of (correct) channels will do nothing more for the animal’s metabolism than to feed one successful channel, because the molecular building blocks for energy units and fat reserves “taste” the same whether they come from this prey or that. As it also seems accepted that most similar, properly-nourished whole prey items can secure necessary vitamin/mineral complexes for most large carnivorous lizards (as they do for snakes), there should be little concern for variety on behalf of this.



Where the inclining for all of these other captive diet analogies originate, I scratch my head. Most tortoise species are not dietary opportunists. Most are specialized feeders on a relatively few certain plant species within their respective native ranges that most closely fit the bill for proper water/mineral balance, although the species of plants can change accordingly throughout the various seasons (at least in the well-studied arid-environ Gopherus, Psammobates, and Geochelone(Chelonoidea) chilensis complex). More than one plant species have to be utilized because, unlike with whole-animal foods, a single whole-plant food doesn’t normally contain all vitamins and minerals (or appropriate amounts) necessary for proper metabolism. Captive specimens of all tortoise species are supported on pseudo-diets such as kale, mustard greens, red-leaf lettuce and/or Mazuri chow. That is nothing other than a simple lab mouse diet analogy. Similar nutritional pathways are being met by “whole,” yet rather unnatural, fodder. The crocodile analogy was a direct point as to sturdy, dietarily opportunistic reptiles needing only baseline nutrition sources to forward great success. This example does not exactly encourage one to believe cosmopolitan diets are needed by opportunists for proper nutrition.



It seems that some of us don’t want to consider that these animals are successful because of the resourcefulness a cosmopolitan diet allows for, rather than the cosmopolitan diet being what gives the animals nutritional (and thus overall) success. Failure to understand this is likely stemmed from a poor ability to use common sense when it comes to weighing for application the usefulness of natural history data. Hopefully, this reasoning might make the thread more accessible to some. Thanks.

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