Digestion

The four-chambered digestive stomach in a cow is huge and digestion is slow.

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My stomach rumbled as I sat at my desk and given that my wife had recently been ill, I was glad that a toilet was close by, just in case. As it turned out, I dodged the microbial bullet, but it put me to thinking about digestion and all that it entails (not entrails).

All animals have a digestive system, although there are many different kinds. Often referred to as the gastro-intestinal or G.I. tract, the function is to process foods into simple nutrients that can be absorbed by the body. This is true in all animals.

For a typical vertebrate animal, the system consists of a mouth where food is roughly broken down and saliva begins the digestion process. Food passes to a stomach via an esophagus. In the stomach, acids, enzymes, and microbes go to work on the lumps of food. The food is then passed to the small intestine where further breakdown occurs. So far, this process has been linear—mouth-esophagus-stomach-small intestine. But at this point, the liver and the pancreas, two solid organs that don’t directly handle the food, come into play providing enzymes for digestion in the small intestine. As the food works through the small intestine, the nutrients are absorbed into the bloodstream through epithelial cells in the intestinal walls. What is left is passed onto the large intestine where more water is removed and the waste is compacted into, you guessed it, s---, I mean feces. It is stored there until it is excreted through the rectum and anus.

For some invertebrate species, the process is even simpler. Flatworms, corals, jelly fish and sea anemones do not have a pass-through system. Instead, they have a gastrovascular cavity with only one opening. Food and waste use the same opening and the cavity does all the digesting.

There are many differences from the general vertebrate model above. For instance, birds do not have teeth to break down their food. Many species instead rely on a muscular gizzard where hard foods such as seeds can be crushed and processed with the help of small stones, called grit, that the birds intentionally ingest.

Members of the Bovidae (cattle, sheep, goats, antelopes) and the Cervidae (deer, elk, moose, caribou) families add to the system. Their diet consists of 100 percent plant material that is full of cellulose with tough cell walls. In order to process this food, these families have developed four-chambered stomachs and a process called rumination. Digestion for them is a slow process that includes lots of microbial action and fermentation. They regurgitate food from the first two stomachs and chew it again in a process called cud chewing. Someone who is taking their time thinking about something is said to be ruminating about the subject, a direct reference to the process of digestion in the four-chambered stomach.

Sharks are another interesting group. Just about anything may find itself in a shark’s belly including tires, video cameras and even a full suit of armor, clearly inedible stuff. The acid in shark stomachs is strong enough to dissolve metal and their liver, the producer of digestive enzymes, may be as much as one third of their bodyweight. In addition, some sharks have the ability to turn their stomach inside out, dispelling indigestible items and getting a good rinse before they re-swallow it.

It seems that there just isn’t much about our bodies that we can or should take for granted. Living creatures are still the most complex organisms—Artificial intelligence and robots be danged.

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Help Idaho Wildlife

When we traveled across the state in October 2017, most of the vehicles we saw using the wildlife management areas did not have wildlife plates. Buying wildlife plates is a great way for non-hunters and hunters alike to support wildlife-based recreation like birding.

C'mon folks, let's help Idaho's wildlife by proudly buying and displaying a wildlife license plate on each of our vehicles! 

See below for information on Idaho plates. Most states have wildlife plates so if you live outside Idaho, check with your state's wildlife department or vehicle licensing division for availability of state wildlife plates where you live. 

And tell them that you heard about it from Nature-track.com!

Wildlife License Plates

Great news! as of 2024, there are three NEW designs for license plates. They still are bluebird, cutthroat trout and elk, but they are beautiful.

Idaho Wildlife license plates provide essential funding that benefits the great diversity of native plants and wildlife that are not hunted, fished or trapped—over 10,000 species or 98% of Idaho’s species diversity. Game species that share the same habitats (such as elk, deer, antelope, sage-grouse, salmon, trout) also benefit from these specialty plates.

No state tax dollars are provided for wildlife diversity, conservation education and recreation programs. Neither are any revenues from the sale of hunting or fishing licenses spent on nongame species. Instead, these species depend on direct donations, federal grants, fundraising initiatives—and the Idaho Wildlife license plates.

Both my vehicles have Bluebird Plates. I prefer the bluebird because the nongame program gets 70 percent of the money from bluebird plates, but only 60 percent of the money from elk and trout plates - 10 percent of the money from elk plates supports wildlife disease monitoring and testing programs (to benefit the livestock industry) and 10 percent from cutthroat plates supports non-motorized boat access.

Incidentally, in 2014, the Idaho Legislature denied the Department of Fish and Game the ability to add new plates or even to change the name of the elk and cutthroat plates (very specific) to wildlife and fish plates, a move that would have allowed for changing images occasionally and generating more revenue. It would seem that they believe that we Idahoans don't want a well funded wildlife program.

I think it is time we let the Legislature know that Idahoan support wildlife funding and that we would like to see these generic plates come to fruition.