Wondrous Wildlife
By Vern and Lori Gieger
If It Rattles
(In memory of Ed Lusch, a long-time trusted friend, we would like to dedicate this month’s column to him. We’ll miss you Ed!)

     Many knew Ed for his literary genius, or perhaps for his enthusiasm of fishing. Ed was also passionate about wildlife and the environment; his vast knowledge of wildlife left one in awe. We shared a common passion for reptiles, especially snakes—looking beyond the obvious and seeing the beauty of them, and marveling at their perfection.
     Almost everyone is fascinated by rattlesnakes. This fascination is often a result of fear of them, which is legendary. Usually perceived to be aggressive and deadly, their threat to humans is grossly exaggerated. These animals merit admiration more than fear; rattlesnakes are among the most highly specialized organisms on the planet.
     Rattlesnake venom (in fact toxic saliva) is among the most complex substances known; there is no standard rattlesnake venom—a unique combination of proteins that range from hemotoxins, to anticoagulants to neurotoxins. Their delivery system is equally amazing; their fangs are like movable hypodermic syringes. Rattlesnakes may be among nature’s best examples of efficiency. The use of venom to capture prey conserves considerable energy that would otherwise be needed to capture and subdue an animal.
     Rattlesnake venom functions primarily to aid in the animals feeding which they strike and release. It is not believed to be a defensive mechanism to avoid predation, though it can be very effective in this regard. Approximately 20 percent of defensive strikes are dry; that is, no venom is injected. This has led to the conclusion that rattlesnakes can choose not to envenomate.
     Rattlesnakes are among the few groups with dual visual systems. In addition to their eyes, heat-sensing pits, located behind each nostril allow them to actually see infrared images. They can detect the heat from a candle flame 30 feet away. Heat given off by any animal creates a heat image, therefore enabling them to hunt effectively even in total darkness. It also distinguishes predator from prey, allowing the rattlesnake to determine whether he is at risk. Large, non-prey animals give off larger heat images, signaling the snakes to avoid potential encounters with these animals.
     The best way to distinguish rattlesnakes from other kinds of snakes is by the rattle. Most other characteristics are either too subtle or inconsistent, or require one to get too close to the animal for safety. Even at birth, rattlesnakes have the first segment of a rattle, which is called a prebutton. The prebutton is lost the first time the snake sheds its skin and is replaced by a button. Each subsequent shedding adds another segment to the rattle; rattlesnakes may shed four or more times each year. Only when there is more than one segment can the rattle produce sound. There isn’t anything inside the rattle; the segments merely bump up against each other to produce the sound. The sound produced results from movement of the rattle back and forth, 60 or more times per second!
     Rattlesnakes are more active during warmer weather, spring through early fall. They tend to be more nocturnal during the summer months. When favorable temperatures occur, many rattlesnakes are marginally active even during the winter. You are most likely to see them when the air temperature is between 70° and 90° F regardless of the time of day, be it June or January. Baby rattlesnakes are born live, typically from mid-summer to early autumn. They arrive fully equipped with teeth and toxins!
     Rather than seeking to eradicate these animals, we have more to gain by finding ways for all of us to coexist. Why? Because these animals are the natural predators of a suite of other animals (e.g., mice and rats) that can cause plant damage, carry diseases, and so on. Besides, trying to kill rattlesnakes actually puts us at greater risk than does leaving them alone.
     Knowledge of who these creatures are, that is, what they do to live, where they live and when they are active, will help us coexist without harm to either snakes or humans; 90% of all rattlesnake bites to humans are a result of trying to capture or kill them. Some species are believed to be extinct, many other are threatened. Here in Mexico all snakes are protected by federal laws. The most common rattlesnake in our area is the black-tail rattlesnake. This species is easily identified by its black tail, which extends from the rattle, ending abruptly at the body. This rather large specie is relatively non-aggressive and has the least potent venom of any rattlesnake.