I am happy to report that the Middle San Pedro Valley has finally received some summer rain! This has been a very dry summer – during July and August, we have received only .63 inches of rain. Most of that has occurred during the past four days. The summer “monsoon” season is what literally defines this ecosystem – enabling much of the rich assemblage of plant and animal species that makes this part of Arizona such a remarkable place.
Despite the extended drought, the velvet mesquite trees in the local bosque have put on a tremendous spurt of foliar growth this year. Additionally, the trees have flowered three times since spring. As I write this, the ground under the trees is plastered with a heavy crop of “beans,” the nutrition-packed seed pods that are one of the cornerstone food sources for our wildlife. How can this happen during such a bone-dry, hot spring and summer? The answer is rooted in last year’s very wet monsoon season. Mesquites have a remarkable ability to move rainwater down their roots, where they store it at depth for later use. That’s right; these trees can move water in both directions in their root systems! The big bean crop owes its genesis to last year’s stored rain water.
This has been one of the driest and hottest summers I can recall here in the Middle San Pedro River Valley. During “normal” summers, monsoon rains arrive between the middle and the end of June and continue through August and much of September. The two previous monsoon seasons brought us a welcome abundance of rain, but this year has remained very, very dry. Daytime highs for the past six weeks have averaged around 106°F., with more than a few days reaching 110° or higher. This year’s highest temperature registered at a crispy 115°F. on July 17.
Last week, two friends and I embarked on a short hike up a roadless drainage in an effort to scout the area for a group hike that I will be leading in a few days. We were also hoping to explore an amazing slot canyon that one of my friends had discovered more than a quarter century ago.
I refuse to publicly divulge the location of the canyon for several reasons. First, there is the matter of deep respect for the many living things that call the canyon and the surrounding area home – a rich community of undisturbed native plants, insects, snakes, birds, mammals, etc. Secondly, when wild places are publicized, more and more people inevitably go there. Trails get carved into fragile desert soil. Litter appears…candy wrappers, used toilet paper, beer cans, broken bottles and spent shell casings from those who carry weapons. Initials get carved into once pristine stone walls and the garish rudeness of graffiti mars the sanctity of the place. Sensitive wildlife species leave or disappear altogether. All I will disclose is that this area is somewhere within the 4,720 square-mile San Pedro River Drainage in southeastern Arizona.
Our walk led up a wash (desert speak for a streambed that remains dry during most of the year) under cloud-flecked skies on a warm spring morning. Less than a mile in, we came across the signature tracks of what has become the region’s apex predator (next to humans). Just two centuries ago, that role would have taken a back seat to the indigenous people, jaguars, wolves, and grizzlies that thrived here prior to the arrival of large numbers of Euro-Americans.
March is a month that spurs changes in southern Arizona’s avian world. As we walked, turkey vultures soared overhead, recent arrivals from their wintering grounds. Mockingbirds and cactus wrens were singing with newfound spring zeal. Two other recently arrived migratory species made themselves known- one by voice, a gray hawk – and another by sight, a large, lone, black-colored bird flying over a distant ridgetop. Its silhouette formed a distinctive, familiar shape. The combination of broad wings and a wide, short tail nearly touching the trailing edges of the wing feathers strongly suggested a common black hawk. As the raptor curved its flight path, banking its body, the tail suddenly flashed a broad white band, cinching the identification. The hawk had just appeared here from migration; had we been in the same area only days sooner, it was likely that we would never had seen it.
Not long after the black hawk, we changed direction, exiting the wash to ascend a gentle slope leading toward my friend’s slot canyon. Two of us followed as he led the way to the base of some sandstone cliffs…
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First, a note of sincere, heartfelt thanks to everyone who so generously contributed to my appeal for a new pair of binoculars! The appeal was a great success – I am elated to say that the new binoculars are in my hands, and they are absolutely stunning. I cannot adequately express my gratitude for the gift of such an exceptionally important tool that will enable me to continue doing what I do as a naturalist. I’m beaming as I write this. 🙂
White-nosed coatis are one of the most charismatic and fascinating native mammals of SE Arizona. Bands of them are fairly common in the Middle San Pedro Valley where my family and I reside, but I have rarely documented their presence on our property. Only days ago, my wife saw a lone individual close by our home. Two days later, a band of coatis crossed our little acreage unseen, but they left abundant and unmistakable signs of their presence.
Some two decades ago, when I first began to roam the wildlands of this valley, I was not sure how to separate the tracks of coatis from those made by one of their cousins, the raccoon. I had heard that they were difficult to distinguish, but that soon proved to be incorrect. This exemplified one of many things that a naturalist must learn by direct experience out in the field, for the great majority of tracking books fall far short of being accurate, reliable sources of information.
So, how does one recognize the differences between the tracks of these two animals – tracks that, ostensibly, can look a lot alike?
Another pair of native mammals that can leave similar signs of their presence are mule and whitetail deer. One of several ways to distinguish their signs comes into play when these animals are moving at high speeds. Whitetail deer gallop when they run fast, but mule deer tend to stott when they are in a hurry. Stotting refers to an upward leaping motion where all four feet leave the ground at the same time and land at roughly the same time – a type of movement that most people would describe as a hop. And what a hop it can be!
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A few evenings ago, an uncommon view from my desk window engendered delight and a deep feeling of gratitude. The scene encompassed a wild mesquite bosque, standing tall and green in summer’s refulgence…a gentle, drizzling rain was floating its way to the ground, suffusing the air among the stout trees with the magic of a fine mist, colored soft in fading light. The land was coming alive, replete with the promise of sprouting plants, emerging fungi, and the rising scent of moist duff. A water-borne resurgence of desert life was in the making.
During the past few weeks, more rain has fallen, resulting in a cavalcade of change, a water-borne eruption of desert life. Flowers are blooming and creatures are stirring, many of which cannot be seen at other times of year. Giant millipedes are crossing roadways and threading their way through the woodlands, tarantulas are out of their burrows roaming the landscape, harvester ants are forming great clouds of alates bent on their one-day-per-year mating spree. Sonorous calls of amphibian passion are ringing through the night after every substantial rain. “Monsoon” as locals know it, is the one season that defines these lands and the ecology of southeastern Arizona more than any other. Arizona without its monsoon would be akin to Alaska without a winter.
One of many creatures that are revealed during this season is a small, nocturnal lizard with semi-translucent skin like gauzy velvet, big eyes with vertical pupils and movable eyelids, and the very rare ability (among lizards) to vocalize. Once encountered, the western banded gecko is not soon forgotten. More than once, I have heard the word “cute” applied to this beguiling little creature that rarely grows to more than four or five inches in length and remains hidden during daylight hours.
When predators chase after lizards, the first part of the lizard’s body that they make contact with is often the tail. In evolutionary response to this, many lizards have developed special abscission layers in their tails. Once contacted, the tail breaks off, leaving predators detracted by a wiggling morsel while the main course absconds to safety. Banded geckos have tails that break off with a very, very light touch; hence, I recommend against handling them.
When threatened or disturbed, banded geckos often curl their tails over their backs. Such posturing mimics the scorpions that they share habitat with, potentially scaring off some would-be predators. Banded geckos can also utter an audible squeak when frightened, making them one of the few lizards in the world capable of vocalizing.
During late July, the mass of tadpoles in our bird pond (see the previous blog post) transformed into toadlets in a matter of only ten days. The tiny young amphibians are now hopping their way into the surrounding woodland, disbursing at night when temperatures are cool.
On a warm early morning in mid-July, I took a walk and discovered an abundance of white-lined sphinx moths (Hyles lineata) almost everywhere I went. Most sphinx moths do their flying at night, but these moths were out in direct sunlight. They were specifically targeting wolfberry (Lycium spp.) bushes. The wolfberry was in flower, and the moths were hungry for nectar. With unerring accuracy augmented by rapid, graceful flight, they were moving from flower to flower, hovering at each one to insert their long tongues for sips of nectar.
White-lined sphinx moths have a very wide distribution that includes most of the United States. In some areas, their tongues are considerably shorter. Here, as they coevolved with certain types of nectar-rich flowers bearing long corolla tubes, their tongues adapted over time.
This year’s monsoon got off to an early start in mid-June, but thus far, we have received just 2.98 inches of rainfall. Many storms have passed by, missing us by only a few miles. Hope for more rain is justified, however, because the summer monsoon season still has a couple of months to go. Summer rain always brings a wonderful blooming of life to this arid landscape, most of which cannot be witnessed at any other times of year. Here is a brief gallery of some of those recent gifts…
Early summer in the Middle San Pedro Valley has brought us some uncommon sights. One of our nation’s most dazzling – and sneaky – songbirds is the varied bunting. No larger than a small sparrow, varied buntings often appear black unless they are viewed at just the right angle in favorable light. They occur in small numbers here; we typically see only one or two of them in our bosque every summer. They are sneaky because we never know when they will appear, which is infrequently at best. A beautiful male will drop from the mesquites to grab a quick drink of water from our bird pond, then quickly disappear into the depths of the woodland, not to be seen again for days or even weeks.
Last week, a rare find presented itself in the form of a fresh Gila monster trackway etched into the fine dust along the side of our shop building. The only other animals that can leave similar trackways here are turtles, but a close look at this trackway leaves no doubt as to its maker.
The month of May brought the expected blooming of saguaros, but this year the huge cacti did something very strange. Instead of crowning the tips of their trunks and arms with halos of blossoms, they grew flowers both on the tops and down the sides of their heavy arms. I had never seen this phenomenon until this year. Locals are saying that this is a response to the severe drought we are experiencing in the desert southwest. I want to know why the plants are behaving like this.