Bone Biology

   ©Terry R. Thomas/www.nature-track.com

Chimpanzees and other arboreal primates are subject to broken bones, especially when they are younger and learning to climb.

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If you have ever broken a bone, you quickly learn two things: it hurts a lot and, bones are living tissue that takes time to heal, but they do heal. A fractured femur for instance, may take six months to a year to fully heal (although it can be put back into service after eight to twelve weeks).

Because bones are more or less inert, providing the support for muscles and tissues, we tend to ignore the complexity of bones. Bone is not created once and allowed to ossify like a fossil (except antler, which does exactly that). As long as we are living, bone is highly dynamic, constantly remodeling itself through complex interactions between four types of cells specific to bone. These cells are osteoclasts, osteoblasts, osteocytes, and bone lining cells. The functions of these cells are:

“Osteoblast. This type of cell is found along the surface of the bone. Its function is to form new bone tissue, remodel bones while aging, and heal damaged bones.

Osteoclast. This cell is larger than osteoblasts and is found within the bone itself. Its function is to dissolve, reabsorb, and remove unwanted bone tissue.

Osteocyte. This type of cell is within the bone. It helps to maintain bone as living tissue.”

Bone lining cells cover inactive (non-remodeling) bone surfaces, may be involved in sending the activation signals for remodeling and resorption, and are important in the maintenance of bone fluids.

One can easily imagine how complex the interaction between bone building, or remodeling and bone absorption must be. There are many players besides these cells that provide signals or materials for these processes. If the processes get out of sync, we end up with bone disorders such as osteoporosis (more bone is absorbed than is replaced) or osteopetrosis (more bone is built than is absorbed, leading to dense but brittle bones).

In mammals, bone starts out as cartilage in the fetus. This skeleton gradually transforms into bone through a process called endochondral ossification and starts in the middle of the cartilage “bone”,  a process that may take several years after birth to be completed (for instance, human babies have knee caps of cartilage at birth that may take up to six years to ossify). Once the bone is ossified, growth continues from cartilaginous areas near the ends of long bones at areas called epiphyseal plates, a.k.a., growth plates. When these areas finally ossify, growth of the bone stops.

Bone density is one crucial measure of the strength of a bone. A higher density means more mineral content and a more tightly packed structure. Higher density means greater resistance to fracture. Animals that are subject to high physical stresses such as deep-diving, combat, or high-speeds, often have bones that are denser to cope with these demands. The Blainville’s beaked whale may hold the record for the densest bone (the rostrum). The manatee holds the title for having the highest bone density overall, an adaptation that helps them counteract the buoyancy of their blubber and stay submerged in the water. 

While it is true that larger bones can be stronger, bone composition and internal structure all play a role. For instance, the femur of a roe deer, is small, but can support 1.5 tons of downward pressure because of its structure. When all things are considered, many scientists consider the ostrich to have the strongest femur, again because of structural components, in this case called trabeculae, or bony ridges inside the femurs.

As tough as bones are, they are not unbreakable. Animals living in the wild can easily break bones as they traverse wild country. For instance, researchers believe that fully one third of orangutans fall and break a bone at least once in their lives. Twenty per cent of skeletons from wild chimpanzees show at least one healed fracture, and up to 30 per cent of wild gibbon skeletons have at least one healed break. Mostly, these breaks occur when they are young animals, not adults. However, I have seen the skulls of adult bull elk that exhibited cranial plates fractured in combat.

We can improve bone size and density and thus reduce the chances of a fracture with one simple activity: resistance exercise. Workouts that include weight (even body weight) lifting type exercises stimulate bone growth and become increasingly important as we age.

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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.