I have always looked forward to the month of April in southeastern Arizona, for it brings a great diversity and large numbers of migrant birds to the land – or does it? The first time that I birded the San Pedro River was in April of 1977. In a word, that was a stunning experience. The numbers of birds were incredible, as were the variety of species. Today, the story could hardly be more different.
Migrant songbirds (and other migratory species) have been steadily declining ever since Europeans began to populate the North American continent. The rate of decline was slow at first, but it has increased continually through the centuries. During the past several decades, declines in bird populations have become so severe that some birds have become extinct, while others are persisting by the thinnest of threads.
Here in the Middle San Pedro Valley, I have been participating in avian surveys and have been keeping detailed records of local bird life for 21 years. The data is disheartening, but this year has been the worst thus far. Numerous species that have appeared on schedule at our property every past April are simply not appearing. Many others are here in very low numbers. Sadly, close to 100% of these declines are attributable to mankind. Overpopulation, urban expansion, climate change, pesticides and herbicides, tremendous habitat losses, loose house cats, and more add up to a world that is becoming quieter and quieter every spring.
What is spring without bird song?
Other happenings in the natural world have been occurring as well, ones that are not disheartening. Lizards and snakes have awakened from their winter brumation to add their grace, color, and life to the land. A few days ago, a Sonoran gopher snake appeared a few feet from my doorway, followed by the year’s first diamondback rattlesnake and the emergence of Clark’s spiny lizards. Our resident ravens, Mike and Mavis, have successfully hatched yet another brood and are very busy keeping their youngsters well fed. A nice abundance of wildflowers is coloring the upland slopes.
The gopher snake mentioned above. We always welcome these harmless and beautiful reptiles. They play an effective role in controlling rodent populations.
This was a slender male, close to 3 1/2 feet in length. Sonoran gopher snakes can attain lengths approaching eight feet, making them one of the nation’s longest native ophidians.A closer look reveals the large, curved, robust rostral scale at the forward tip of the snake’s head. This kind of scalation evolved to shield and protect the heads of gopher snakes as they push their way through soil and pursue rodents deep into their burrows.
Every year in this valley seems to bring its own explosion of certain insects. Earlier this month, incredible numbers of crane flies could be seen. I recall walks where every step flushed 20 or more from the surface of the ground. Crane flies belong to the family Tipulidae, with over 15,000 species worldwide. They are a successful and adaptable group of insects, for their presence in the fossil record dates back over 70,000,000 million years.
A pair of crane flies, busy assuring that their kind has a future. These innocuous insects are sometimes called “mosquito hawks,” for the mistaken belief that they prey on mosquitoes. On a recent walk in the valley with a friend, we paused to admire this rare cristate saguaro, made even rarer by its unusual paired, symmetrical shape.
Incredibly, on the very same day, another friend was roaming the valley when he discovered this huge, cristate specimen. Photo by Gilbert Urias. April brings the return of turkey vultures. Here, one has landed to scrutinize one of our bird watering dishes. Among several unique aspects of these vultures is the fact that they have no syrinx – the organ that allows birds to vocalize. Turkey vultures can hiss by expelling air rapidly, but they cannot call to one another nor utter any sort of song.A close look at the vulture’s head reveals a large perforation in the bird’s beak. When viewed at just the right angle, one can see that the large hole goes all the way through the beak to the other side. Turkey vultures locate the majority of their food via a keen sense of smell, an unusual trait among most other birds. The perforated beak likely helps these birds to smell with great facility, channeling airflow into their nasal scent receptors. (The quality of this enlarged image is poor due to limits that my blog hosting service places on image resolution.)
Shallow watering dishes can do wonders for attracting bird life and many other desert animals as well.
A wonderful and always reassuring sight! The riparian forest that is so deeply important to the valley’s wildlife glows with a verdant spring canopy of cottonwood and willow leaves. The color contrast between the riverside forest and the surrounding uplands is strong in April. The forest – a true hallmark of this valley – is completely dependent upon the San Pedro River and its subterranean aquifers.
I have seen more rattlesnakes around our home this summer than ever before. During the past six weeks, not a single day has passed when I have not seen at least one western diamondback here – on several days, I have seen as many as four. I don’t mind their presence. This would be a very dull world if it were danger – free, cleansed of any creatures that might harm us. The snakes have a right to be here – this land is not just habitat for me and my family, but habitat that we share with many other living things.
Yesterday morning brought a surprise that lay snoozing a few feet from my doorway. It was yet another rattlesnake, but the instant I saw this one, I knew it was not a western diamondback, but a Mojave rattlesnake.
Most of the time, when I spot a poisonous serpent close to our home, I simply leave it alone. Given this snake’s proximity to an area that gets frequent daily foot travel, and the extreme toxicity of its venom, I decided to relocate it. I picked the rattlesnake up with a pair of snake tongs, lowered it into an empty trash can, and hauled it to a new home downriver. During the entire procedure, the snake shook its tail only once, and briefly at that.
I knew immediately when I saw this snake under the ramada that it was a Mojave. The greenish-yellowish tinge to its skin stands out in contrast to the local western diamondbacks, whose coloration tends to be more silvery gray. Note also the sawtoothed edging to the snake’s dorsal blotches. Our diamondbacks rarely show such edges on their “diamonds,” or dorsal blotches.
How toxic is this snake’s venom? Some sources say the venom of Mojave rattlesnakes is ten times more potent than that of other rattlesnakes. (There is one notable exception here – tiger rattlesnakes, which also occur in the Middle San Pedro Valley, are nearly as potent as Mojaves.) Other sources label this species as one of the most toxic snakes in the entire hemisphere. That is saying a lot, especially considering some of the elapid snakes that live in Central and South America. As if that were not enough, research has demonstrated that the Mojave rattlesnakes that inhabit Cochise County produce a unique venom that is even more potent than that of other Mojave rattlesnakes in other parts of their range. Rattlesnake venoms are complex organic cocktails consisting of many ingredients including proteins, polypeptides, metal ions, fats, enzymes, and more. Most rattlesnake species have hemotoxic venoms – venoms that destroy red blood cells, interfere with clotting, and damage tissue. The principal components of Mojave venom are neurotoxic – they act on the central nervous system. A bite from one of these snakes can cause severe paralysis and even cardiac arrest.
So yes, I decided to move the snake away from our home.
This Mojave rattlesnake was captured and relocated by a warm-hearted friend a few years ago; he brought the snake to here to show it to me before releasing it back into the wild. This snake was on his doorstep as well, better relocated than shot or clubbed to death.
Much like sharks or grizzly bears, rattlesnakes are widely misunderstood and unjustly feared by the public. These fears are rooted in ignorance and a cultural bias regarding the world of nature and our place in it. Here in Arizona, where rattlesnakes are common and widespread, more than half of all bites are provoked. (Yes, Darwin was right!) Most of the remaining bites could be easily avoided by a combination of unflagging awareness, protective footwear, and snake gaiters. Awareness means keeping one’s eyes fixed carefully on the ground when moving around outdoors, and always using flashlights after dark. If you look carefully where you are going, you are much less likely to step too close to a snake. When I hike locally during the warm months, I always wear a pair of leather boots and snake gaiters. Simple precautions can really pay off.
Identification of Mojave rattlesnakes is not always a simple task; occasionally, these snakes hybridize with western diamondbacks. They also come in many differing shades of color. The most certain identifying characteristic are the two large scales atop the snake’s head that lie in-between its supraocular scales – (the very large scales that cover
the upper portion of the snake’s eyes). Western diamondbacks usually have six or seven much smaller scales between their supraoculars.
If a person does get bitten, it is imperative to get medical help as soon as possible. Time is utterly crucial when it comes to treating snakebite victims. In this rural landscape, that means a helicopter flight to a hospital in Tucson. The average cost of treating a bite victim has risen to over $75,000 per incident. With that in mind, I think that a small investment in a pair of snake gaiters (most cost less than $100 per pair) and some good boots is a very wise move.
Tail markings are also useful in identification. Mojave rattlesnakes usually show narrower, less distinct black banding on their tails than diamondback rattlesnakes.In contrast, most western diamondbacks have considerably wider, distinct black bands on their tails.
In closing this post, I must say that I do not recommend relocating reptiles. For rattlesnakes, relocation beats getting killed, but is stressful to them, and can result in an inability to survive. Rattlesnakes occupy definitive home ranges, areas that they come to know and navigate through successfully. One of the most critical aspects of their lives has to do with knowing where a suitable site is for hibernation. (The correct term in use these days is “brumation,” not “hibernation.” I used the old term because many more people are familiar with it.) If a snake cannot find its way to such a site, it is not likely to survive the winter. Relocated snakes have been documented to have problems with this, especially if they are moved late in autumn.
