The mountains, foothills and desert of Southwest Idaho are often dotted with deer, elk and other big game animals during spring. It's strikingly beautiful as the scenery changes from brown to green and animals seem to have an endless buffet.

Despite appearances, spring is not the finish line for surviving winter. In fact, it can be the most critical time for some of those animals.

Deer, elk, and other large herbivores rely on a combination of stored fat and dry forage to get them through winter.

Typically, some animals will die from malnutrition, disease or succumb to predators while they're weak and vulnerable during winter.

One of the most important factors for survival is their condition in the fall.

Deer, elk and others store fat reserves during spring, summer and fall, then burn it to help get them through winter.

According to Steve Nadeau, Idaho Fish and Game's southwest regional wildlife manager, March and April can be the most critical months for weakened animals.

Nadeau said if an animal's fat reserves don't last through winter, it uses up not only fat stored beneath the skin, but also fat within its internal organs and bone marrow.

The animal is essentially consuming itself to survive. Once the starvation process begins, tissue damage occurs and several hormones and chemicals are released into the bloodstream.

When starvation reaches a critical point, it is nearly impossible to reverse.

Enzymes and bacteria have changed in the animal's digestive system, and even though it may be feeding on highly nutritious green grass or other feed, it cannot digest it.

The animal can literally starve to death with a stomach full of food.

Though this annual drama may seem cruel, it is merely part of nature, and it ensures the fittest animals survive and maintain the overall health of the herd.

Provided that healthy cows and does survive the winter and give birth in the spring, the animals lost to winter kill will be replaced.

During a normal winter, a small percentage of the herd will die, and if more animals are born than died, the herd will grow.

But in a harsher winter, a larger portion of the herd may die, and in extreme cases, nearly a whole herd can be wiped out.

It's also important to remember that while spring is a great time to be outdoors, you may encounter herds of animals casually grazing out in the open, and they're not out of danger.

Disturbing them can cause harm, so watching from afar is the best way to enjoy nature's gift.

Mark Krepps is a freelance writer, author and blogger.