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Soaptree yucca (Yucca elata) is one of the crown jewels of the Chihuahuan Desert Ecoregion – a tall, stately, easily recognized species that is common in the Middle San Pedro Valley. Its distinctive plume of beautiful white flowers can be seen by the naked eye at distances upwards of a mile away. Soaptree plants can live for more than three decades and attain heights exceeding 15 feet. This is one of the few tall flowering plants in North American deserts that does not strike up a relationship with high-altitude pollinators like birds, bats, hawk moths, or bees. Soaptrees, like many other yuccas native to the West, are pollinated exclusively by only a few genera of specialized, small moths: particularly by insects known as yucca moths, (Tegeticula yuccasela or T. maculata).
The striking white plumes of soaptree yucca flower heads can be seen in great numbers this year, a special early-summer sight that part-time (winter) residents of southern Arizona may never experience.
The most common height of local soaptrees varies between 7-10 feet, but ancient grandmother plants like these can top 15 feet or more in stature.
Large, gorgeous plumes of very soft-textured, delicate, bell-shaped flowers adorn blooming soaptree yuccas.
The close relationship that this yucca has with its pollinating moths has been going on for millennia. The moths are white in color and rather small, with wingspans around an inch in width. After mating, yucca moths fly to the flowers, where they gather pollen. The pollen is carefully packed into specialized depressions on the surface of the flower ovaries. Without this stimulus, the yuccas cannot produce seeds. In return, the moths’ larvae feed on yucca seeds in the developing seed capsules.
A closer look at the flowers, whose futures depend upon an inconspicuous but crucially important moth.
This yucca is among the few desert plants that can thrive in a sand dune environment, but they do very well in other habitats as well, such as the lower elevation uplands in this valley. Unlike other yuccas, Yucca elata forms vertical rhizomes that plunge downward to depths of five feet, then grow out laterally to sprout new plants. Plant rhizomes usually grow horizontally, but this yucca’s departure from that rule enables the plants to do well in hot, dry environs.
Yuccas have a myriad of ethnobotanical aspects, for they were put to many uses by most, if not all native tribes living within the range of these pants. Yucca roots are rich in saponins, which were extracted to make effective soaps and shampoos. Many parts of the pants were consumed as food, including the flower buds, fresh flowers (eaten raw or cooked), and the flower stalks. Tough fibers from the long, linear leaves were cleverly utilized to make twine, rope, footwear, and textiles.
It has been a banner year not only for our local soaptree yuccas, but also for catclaw acacia, Acacia gregii. This specimen hosts a galaxy of highly fragrant yellow flowers whose enchanting scent forms a delightful olfactory signature characterizing the last week of May in the Middle San Pedro Valley.
full bloom alongside the catclaw plants are white-thorn acacias, Acacia constricta. The spherical, bright orange flowers exude a sweet fragrance that compliments their neighbors’ perfumes.
May is such a beautiful month in the Middle San Pedro Valley! Our mesquite bosque bursts into new life, sprouting a light-filtering canopy of spring-green leaves. Birds are singing from the trees, building nests, and rearing their young. Lizards are a near-constant sight and snakes have been leaving their telltale trackways in the dust. Late in the month, something special happens as catclaw acacias suddenly explode with constellations of pale yellow blossoms, perfuming the valley with their luscious, signature scent. The heat of summer begins to blanket the land in newfound warmth, gearing up toward the frying-pan month of June.
This has been a banner year for catclaw acacia, Acacia gregii. The bushes (at times, these plants grow into small trees) have literally colored parts of the valley floor with an unusually dense show of blossoms. This is one of the desert’s special plants that begs to be appreciated in an olfactory way…push your nose up against any fresh flower, and one whiff of its sweet, heady perfume will weld the current zeitgeist of this wonderful region into your permanent memory. A dense stand of palo verde (Cercidium spp.) in full bloom colors an entire ridge with literally millions of flowers, all set beneath tall saguaros that are also in bloom. Palo verde and saguaro are two flagship plants of the Sonoran Desert Ecoregion, here reaching its southernmost boundary in the valley along this very ridge. The spot that I stood on to gather this image marks the northernmost extension of the Chihuahuan Desert Ecoregion. Two great ecoregions merge here, enhancing the rich biotic diversity that is so much an intrinsic part of the San Pedro River Drainage.
Most of the early wildflowers are gone by this month, but some wait for their bloom times, like this display of cow pen daisies, Verbesina encelioides.
A closer look at the vivid yellow flowers of cow pen daisies. The yellow “petals” are actually sepals – subtending the many dozens of tiny individual flowers that crowd the centers of these composite blooms.
I am happy to report that our resident Chihuahuan ravens have successfully fledged a trio of youngsters this year. This comes in welcome contrast to last year’s double brood failure; their initial brood was decimated by hungry coyotes on the first night that they spent out of the nest, and the second brood (rare in ravens) was lost to raptors.
Mavis skillfully positions a bulky chicken egg in her beak and readies herself for takeoff. The youngsters must be fed very frequently. Ravens are experts at finding the eggs of other birds. Mike and Mavis never hesitate when we leave an egg on the ground for them.
Loud cries emanating from the raven nest less than 120 feet from my desk window have been a daily part of this month’s panoply of happenings in the natural world. Young ravens have zero shyness when it comes to screaming at their parents for more food, more food, more food! Five days ago, they left the nest to begin exploring the outside world. We see and hear them many times a day as they roam with their parents and learn the complex magic of raven flight mastery. Few North American birds attain a higher level of flight skills than ravens do.
The three youngsters at rest in the mesquite trees only days after fledging. This is a vulnerable and crucial time for the young wolf birds. They must sharpen their flight skills quickly, for predators lurk above and below. It is also the one time in their lives when learning is greatly accelerated as they stay with their parents for weeks, who guard and teach their brood with steadfast devotion.
Raucous cries and characteristic fluttering wings are a part of every feeding, as Mavis approaches one of her ever-hungry youngsters with a crop full of food.
This has been a sad year for migrant birds, with fewer numbers and fewer species than usual, but there are still plenty of feathered creatures bringing life and – at times – utterly dazzling colors to our world. This male broad-billed hummingbird could not possibly have been dubbed with a duller nor less imaginative name.Among the resident bird species that are still doing well are lesser goldfinches, which crowd our seed bags daily, enriching our surroundings with cheerful choruses of bird song.
During every summer, wet mud or other moist places on the ground attract large congregations of gorgeous, diminutive butterflies.
“Blues” as they are collectively called, belong the the lepidopteran subfamily Polyommatinae. Approximately twenty species occur in Arizona. The moniker “blue” comes to light any time these insects open their wings, revealing brilliant blue coloring on their upper wing surfaces. The species pictured is known as the marine blue, Leptotes marina.
Only male “blues” congregate at puddles or on moist soil and animal scats. The males may require certain minerals, amino acids, and/or salts that the females do not. Local native host plants (for their larvae) include saltbush, catclaw acacia and velvet mesquite. Each species has its own hibernation strategy, with some overwintering as either eggs or larvae, as opposed to the far more common lepidopteran chrysalis. Other species have close associations with ant colonies – such as larvae pupating inside ant colonies, or larvae being tended and protected by ants as they feed on their host plants.
Warm morning light dapples the coat of this mature mule deer doe as she slakes her thirst at our “bird pond.”
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.
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.
This track appeared in soft sand, made by an adult cougar that had walked by the night prior. The cat was a female – mingled with its tracks were the tracks of a single cub that had become large enough to be thinking about going out on its own before long. Mountain lions are primarily crepuscular and nocturnal hunters. They are incredibly adept at hiding quietly – even in scant cover. They utilize large home ranges. The combination of these factors adds up to a furred ghost that very few people ever get to glimpse in the wild.
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…
From a distance, these large, vertical rock outcroppings looked enticing, but the entrance to the canyon was not yet visible.
As our viewpoints changed, the entrance to the slot was revealed. Just inside the canyon’s mouth was this western white-throated woodrat palace. The rodent’s nest (it was currently occupied) can be seen at the bottom of the rock wall. Woodrats literally evolved to prefer steep rock faces as integral parts of their habitat. They are highly adept climbers. Note the whitish stains on the rock wall a few feet above the nest, and the cavity in the rock face farther above with similar stains issuing from its base. The cavity is a frequently used hiding place for the rats, who mark their nocturnal trailways with frequent squirts of pungent urine. Everyone knows about stalactites and stalagmites, but did you know that they can be made from urine? This is a closeup view of the white-stained area a few feet above the rat nest depicted in the photo above.
Centuries of frequent use by woodrats depositing countless dribbbles of pee has caused actual stalactites to form. These are smaller than the stalactites often seen in caves (formed from water-borne mineral precipitates) but they are stalactites nonetheless. A series of funnel-shaped walls towers above the person seated at the end of this short but fascinating canyon.
The view from inside looking straight up at a cerulean slice of sky. The person aiming her camera gives a sense of scale to an otherworldly realm. Multiple funnel-like chimneys form the back of the canyon, where sediment-laden water has carved repetitive shapes in the sandstone, inching its way back through time. These cone-shaped circular funnels are narrow at the top, then widen progressively as they descend to the bottom. This has me mystified. Natural water funnels the world over form with wide mouths at their tops that narrow as the funnel goes down. The shapes in this photograph depict inverted funnels. Even when I try to understand this via methods that include something like the Coriolis effect, they do not make full sense to me. There are numerous singular rock funnels like these in this region, but few places feature multiple funnel shapes like this canyon does. Our hike revealed another rare part of this wild landscape: a saguaro with multiple cristate heads. It will be interesting to watch this cactus as its deformed meristems grow larger in coming years.
The Middle San Pedro Valley sprawls across nearly one million acres of undeveloped, unfragmented land in southeastern Arizona. Its slopes and woodlands, bajadas and ridges have been rimed with frost every dawn under the abbreviated touch of winter’s Sun. Days are short. The land stands hushed and still with its seasonal absence of many birds, reptiles, and other forms of life. Nonetheless, there are many good reasons to get outside and walk the land. January and February have brought a few surprises, particularly in the way of unexpected sightings of locally uncommon birds.
In late January, five purple finches began frequenting our bird feeders, thinking they were well concealed within mobs of house finches and lesser goldfinches. My wife’s sharp eyes picked them out of the crowd. In 20+ years of avian record keeping in this valley, that was the first time we had ever seen purple finches. Another species that has been sighted sparingly here during the winter months is the American robin. For reasons that remain a mystery to me, we have been inundated with robins this winter. They bring me many fond memories of their near-constant presence during past summers when I lived in the northern states.
Speaking of thrushes, another bird that I had never seen in the valley before has arrived to grace the nearby riverbottom woodlands this winter – a Townsend’s solitaire. A friend and neighbor, Tom Talbott, first sighted one about a week ago in the forests along the river not far from our home. Tom is a highly skilled birder and a masterful wildlife photographer. A few days later, walking the same reaches of the river, a friend and I also saw a solitaire. News has been spreading of numerous sightings of this species in areas just a few dozen miles to the north.
A Townsend’s solitaire perches quietly in branches overhanging the channel of the San Pedro River. These elegant thrushes are common residents of timberline forests high in the mountains of western Montana, where I would meet them again and again as I led groups of hikers during the summer months. Their songs are unique and unforgettably angelic, like no other bird I have known. Photo courtesy of Tom Talbott.
Not far from the solitaire, we found this great horned owl snoozing within the branches of a Fremont cottonwood. These owls are remarkably capable predators whose list of possible food items exceeds that of any other North American owl. Among the creatures that great horned owls have been known to prey upon include insects, amphibians, various reptiles, mice, rabbits, domestic cats, small dogs, ducks, skunks, and even porcupines.
Mid-January brought us over an inch of rain in the valley floor during one winter storm. Rainfall amounts were much higher in the nearby Galiuro Mountains, resulting in a strong winter flow for Hot Springs Wash. Such flows during the winter months are rare.
The rain enabled millions of dormant London rocket (Sisymbrium irio) seeds to sprout, providing a new source of food for wildlife while greening the floor of this mesquite bosque with the glowing color of new life.
Large numbers of these small white puffballs erupted from the ground under mesquite trees after the rain. Fungi are becoming known as some of the most important organisms on the planet. The mycorrhizal filaments of many species of fungi form mutually beneficial associations with tree roots, for example. No forest on Earth can exist without such subsurface fungal alliances.
A hooded skunk wandered under my ramada one night, leaving its signature behind in the form of these tracks made in fine, dusty soil. Note the track pattern as the animal was walking at normal speed.
A closer look at the skunk’s footprints. Even though skunks are plantigrade mammals, the heels on their back feet often do not register in their tracks, as seen here. (The hind foot is to the left, front foot to the right.)
I discovered this torpid spiny lizard spending the winter brumating underneath a plastic tub that had been set outdoors on the ground. The lizard was found at ground level, not dug in below the frost line. Temperatures here routinely dip into the teens every winter. I was taught that reptiles must spend winters below the frost line, because otherwise they would freeze and die. I have also seen a pair of diamondback rattlesnakes spending the winter under a board in an open barn. Apparently, what I was taught cannot be correct – it seems clear that these reptiles can endure a fairly substantial amount of freezing.
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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.
Just south of the Arizona/Mexico border, coatis are known as chulos (there are several other Mexican names for them); in the US, most people refer to them as coatis or coatimundis. Taxonomically, they are known as Nasua narica. Among a number of their unique features, coatis are one of the world’s very few social omnivores. (Can you think of any others? Offhand, all I can come up with are humans and meerkats.)
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?
Fresh coati tracks in fine dust under my ramada reveal toes positioned tightly together with consistent thickness along the length of each toe.These raccoon tracks, particularly those made by the front feet, (at left), show diagnostic shaping and separation of the toes. The toes are proximally narrow in comparison to their distal ends, where they widen into bulbous tips with relatively short claws. Once this distinctive toe shape is recognized, misidentifications between well-defined raccoon and coati tracks can be eliminated.When a band of coatis forages, they commonly pause in certain areas where they make numerous shallow digs for food such as beetle grubs. The band that visited here just days ago left this characteristic array of holes behind. (Note the 6-inch ruler included in the photograph for scale.) Skunks are common locally, and they also dig for a living, but not in this fashion.On a hot summer day years ago, I photographed this chulo sign along the banks of the San Pedro River. The coatis had been digging into the sandy riverbank, leaving some spectacularly long claw marks in addition to the excavated holes.
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!
A mule deer buck moving at high speed left a set of tracks near our home last week, beautifully defined in rain-moistened soil. This deer had easily leapt over two fencelines in less than several dozen yards and had clearly been moving very quickly. I laid a measuring tape on the ground along the deer’s trackway – it revealed a single stott that measured 19 feet, three inches in length. No problem for an adult mule deer.
Here are the four feet of the buck at one of the points where he landed. The deer did not stop here – these tracks were part of a series of energetic stotts. Note that the front feet are positioned ahead of the hind feet, (relative to the direction of travel). If the deer had been a galloping whitetail, this order would be reversed, (rear tracks to the front and front tracks to the rear). Note the spread clouts of the hooves. Deer (and many other mammals, including barefoot humans) autonomically spread their hooves like this in order to prevent slippage as they gallop or stott.
The desert is ever so quiet lately; bereft of nearly all bird song and the scurry of lizards, the hushed glide of snakes, and the plod of tortoises, autumn stills the land. Despite the fact that it is now early December, the cottonwood stands along the river are just now coming into full color, normal timing that can seem so late, given the other species of cottonwoods that I grew up with in more northerly climes. Life sometimes demands a closer look, especially during its seasonal ebbs. Here is a gallery of some of the little things that still manage to crawl or fly about in these cooler times…
Jerusalem crickets are large, chunky insects that spend most of their time concealed under objects or under ground. One of their diverse genera, Ammopelmatus, (unique to the western US and Mexico), is currently known to contain well over 20 species. Among their common names in Mexico is Niño de la Tierra, or “Child of the Earth.” The heavy, spiked legs visible in this image are adapted for digging. The huge head houses powerful musculature that enables a very strong bite. Jerusalem crickets drum their abdomens on the ground to attract mates. They leave distinctive tracks on dusty roadways that show drag marks left by their heavy abdomens. And yes, the “I look like a big, striped, stinging insect” is a great example of aposematic coloring.
As the summer floods draw to a close, moist banks of mud remain for many weeks – even months – along certain reaches of the San Pedro River. Here, a statement in brilliant color comes to life as a group of thirsty Southern Dogface Butterflies, Colias cesonia, drinks from lingering monsoonal rainfall trapped within flood-deposited clay sediments. The name “dogface” originates from patterns seen on the inside of the wings, uncommonly noticed since this species rarely perches with its wings open. Several species of carpenter bees inhabit the San Pedro River Drainage. Despite a detailed search, I could not find a match to identify this species with its pair of striking red head spots. Carpenter bees are big, impressive insects that chew their way into wood, constructing tunnels where they raise their young. I have watched them boring into live mesquite trees, an astounding feat, for mesquite is an incredibly tough, dense hardwood. Their tunnels can approach lengths of twelve inches. A fleeting touch of bright orange reveals a Leafwing Butterfly, Anaea spp., whose host plants are limited to crotons. I know of very few lepidopterans native to the desert southwest that can rival this species for such sheer, saturated, brilliant orange-red coloration. When at rest, with wings folded, this insect virtually disappears into the foliage, living up to its name. Like most people, I have seen countless spiders in my lifetime, but very few have been colored like this one, known as a Green Lynx Spider, Peucetia viridans. Measuring between 5/8 – 3/4 of an inch in body length, this species is capable of taking down prey as large and formidable as carpenter bees. Like all their kin, lynx spiders manufacture silk, but do not make webs; their silk is used to anchor them when jumping, and to attach egg sacks to vegetation. They also have a defensive trick that few other spiders possess – the ability to squirt poisonous liquid at an attacker up to a foot away. Late in the year, as foliage often yellows, this spider is able to change its color from predominantly green to pale shades of yellow. Photo by Kathleen Waldt.
A Plea For Help
Naturalists, like all professionals, require tools in order to do their work. I can say without hesitation that my most important tool has always been a pair of binoculars. Naturalists are literally disabled without them. My trusty pair of Zeiss binoculars have finally reached the end of their lifespan, after 33 years of near-daily use. I am seeking help in replacing them, for professional-quality optics are never inexpensive. If you would like to consider this sincere plea for assistance, please click on this link:
Darkness settles over the land. Many miles from the lights and sounds of towns and cities, Arizona’s Middle San Pedro Valley sprawls wild and still. At twilight, only a faint poorwill and a pair of great horned owls can be heard. The coyote telegraph erupts and then fades as it travels from ridge to distant ridge. In contrast to the rich variety of summer sounds, an autumnal hush blankets the countryside.
At day’s end, dusk gently ebbs into darkness as a brilliant October moon emerges from the far shores of the eastern horizon. Here, in our mesquite bosque, the peace and comfort of the night suddenly give rise to a thousand voices raised in the jubilance of courtship. These are sweet, almost melodic sounds – October’s distinctive nocturnal biophony. Tree crickets are singing from the ancient trees, thousands of them spread across the valley floor, their songs a vivid proclamation of thriving life within an otherwise quiet forest.
This species of tree cricket sings from the tall mesquites in our bosque. Its ecology is intimately connected to velvet mesquite trees. These are small insects with a big voice.
I have come to love the sounds of these delicate, gossamer-winged insects. Long after summer’s insect frenzy, when most species have faded from the scene, tree crickets come to life in the coolness of October nights. The males raise their transparent wings, then call to the females by stridulating – in other words, they rub certain parts of their bodies together to produce a surprising volume of sound. Females are drawn to these love songs. The males go one step farther by offering their mates a special reward. After mating, metanotal glands located on the dorsal side of the male’s abdomen secrete a substance that the female feeds on.
Eight species of tree crickets inhabit southeastern Arizona, where they produce two generations each year. The ones singing in local October bosques belong to the genus Oecanthus. Each species has its own unique song. However, even among the same species, sound can vary quite a bit depending upon air temperature. The frequency (or pitch) of the crickets’ songs increases as temperatures rise and slows as temperatures fall.
A bizarre butterfly landed on my screen door last week – an American snout butterfly, Libytheana carinenta. Last year, large numbers of these butterflies erupted all over the valley in late summer. Snout butterflies use their strange shape to blend in with their surroundings. When perched on a plant stem, their elongated “snout” breaks up the outline of their bodies, resembling a broken twig or a thorn. The range of snout butterflies extends all the way to South America. They are known for migrating across landscapes in huge aggregations.
A study in camouflage, the American snout butterfly sports wings that blend well with tree bark and a unique body shape that helps to conceal the insect when at rest.
This summer’s plentiful monsoon rains have continued well into October. Since the monsoon began on June 18, our rain gauge has recorded an amazing 13.46 inches of life-giving rainfall.
One of the local washes experienced some large summer floods. I took a walk down this wash with a friend a few weeks ago, to have a look at the powerful changes wrought upon the land by the big floods. What we saw was in stark contrast to the wash I had known from walks during the past several years.
During recent times, this broad wash had been covered by a wall-to-wall effusion of burro bush (Hymenoclea) standing six or more feet tall with a galaxy of roots anchoring the bushes to the ground. The flood had erased most of that growth, leaving behind a clear streambed lined with heaps of debris – tree trunks, plant material, rocks, and more. The floor of the big wash had been totally rearranged, its topography and course markedly changed during a couple of events that lasted only days.
In places where floodwaters form swirling, circular eddies, holes are dug into the wash floor like this one. These depressions can be very large and quite deep. They often hold pools of surface water that can last for months after flooding, a valuable offering to birds, mammals, and other wild creatures in this desert ecosystem.
Powerful floods like these transport thousands of tons of boulders, rocks, gravel, sand, clay, and a wide variety of organic materials – whole trees, cacti, and other plants. Downstream, entire soil profiles are altered and built as sediments settle from the turbid waters. Cutbanks collapse, dropping great layers of soil into the roiling floodwaters, releasing seeds that have lain dormant from ancient times into the present-day ecosystem. Old genetics from times long gone may invigorate plant populations and enhance the genetic variability – and hence, the viability – of modern plant communities.
Most people would simply label this collapse of a stream-side cutbank as “erosion.” That is an accurate use of the word, but I see much more going on here.
Debris piles left along the stream banks can be very large, consisting primarily of tangled, broken bushes, parts of trees, and other plant matter. They provide shelter and denning sites for small mammals, reptiles, amphibians, and other creatures. Floods are not all bad – they are simply a natural, intrinsic agent of change, some of it beneficial, some not. People often label floods as “bad,” but that viewpoint roots in anthropocentric thinking, a myopic way to view our world.
The ecology of many native species of plants and animals actually depends upon flood events. The beautiful stands of cottonwoods that line the San Pedro River could not exist were it not for floods creating the specific conditions that their seeds require for germination. The riparian forests that accompany the river depend upon having their roots tap into subsurface aquifers. The aquifers get recharged when floods happen.
As floodwaters recede, the bed of the San Pedro River leaves records of local wildlife in the drying mud. Here, the patterning of fine surface cracks results from a place where the river water subsided very gradually with little or no turbulence, resulting in the deposition of extremely fine clay particles. As these clay deposits dry, they crack in characteristic patterns.
October typically brings us the last ophidian visitors of the year, most of them not to be seen until next spring. A beautiful gopher snake was here last week, and as I write this, a diamondback is curled up a short ways from my entry door.
An October gopher snake, crawling along the wall of one of our buildings. This one was a male, measuring right around 63 inches in length. Always welcome here, as are all snakes.The year’s last generation of pipevine swallowtail butterflies occurs in October. I found this gorgeous caterpillar recently – it is either in the fourth or fifth (last) instar of its development, after which it will climb a plant stem and metamorphose into a chrysalis suspended by a single loop of silk as it waits out the winter season. The leaves visible in this image are pipevine leaves, (Aristolochia), the only plant that these caterpillars feed upon.
October is THE month for seeing pinacate beetles (Eleodes spp.) – they are literally everywhere at this time of year, easily noticed because of their large size, slow movements, and diurnal habits. When they feel threatened, pinacate beetles stop moving and assume this head-stand posture. If the threat escalates, (for example, when a bird tries to grab the beetle), the beetles fire a noxious, very disagreeable fluid from the tip of their erected abdomen. Chemical defenses are very common among many insect species.
Just a few days ago, I noticed this small tuft of feathers laying on the ground. Immediately, I began searching the area for more, because such a find usually indicates that a bird was recently preyed upon somewhere nearby.
I soon found many feathers like this, their shafts intact. Intact shafts indicate feathers that were pulled out, not bitten and yanked out as mammals do. So this was the work of a predatory bird, likely a Cooper’s hawk that I have been seeing frequently of late. This was a special find, for these feathers could have come from only one species, a gilded flicker. Gilded flickers are relatively rare in local bosque habitats.
There has been a sudden and tremendous eruption of small beetles in the local mesquite bosque. A dense, tall understory of pigweed, (Amaranthus palmeri) covers the floor of the woodland, an exuberant growth enabled by recent monsoon rainfall. When I walked into these plants this morning, curtains of tiny beetles took flight from the pigweed at my every step, thousands upon thousands rising upward like a reverse blizzard.
The leaves of the pigweed plants had become dotted with countless small holes during the last two days. This morning, the plants revealed that an orgy of feeding had taken place during the night. Literally all of their leaves had been reduced to a ghostly remnant of reticulated veins with no leaf tissue left in between. Every plant, everywhere I looked – consumed overnight.
Acres and acres of bosque understory were fed upon by an almost inconceivable number of small insects. The plants looked almost shredded.
A pigweed leaf after the night’s heavy feeding spree.
Naturally, I had to know what these beetles were. They were diminutive, measuring around 4-5mm in length. Up close, the beetles were beautiful, sporting brightly colored, broad white bands running lengthwise across their shiny black elytra. After some research, I learned that they were known as “pigweed flea beetles,” Disonycha glabrata. Their ecology entails a close relationship with specific host plants – they will feed only on plants in the genus Amaranth. I have witnessed dense growths of pigweed during most of my summers here; I had noticed these beetles in prior years, but never in such spectacular abundance. Why had their population so suddenly rocketed this year? I can only guess. Perhaps this year’s rains were perfectly timed at just the right intervals and in perfect amounts to encourage such an event? Maybe it has something to do with their predators…or some other mechanism?
A pigweed flea beetle, Disonycha glabrata.
When insects erupt in large numbers, people are often quick to react with alarm and negative attitudes. Yes, they shredded an entire forest understory – but was that a bad thing? Or simply natural change? It is not our place to pass judgement on what happens in the natural world. Both the beetles and their host plants are native constituents of this ecosystem. So, I do not necessarily think that what has happened is somehow wrong or alarming, but it is interesting.
I found another creature wandering in the pigweed last week – a young adult Sonoran Desert Tortoise! We see these reptiles rarely here in the bosque; they are more partial to nearby upland desert habitat types. This one’s carapace was between 9 – 10 inches long, and like most of its kind, it was cautious, slow-moving, and appeared unfazed by my presence.
The Sonoran Desert Tortoise that I discovered resting peacefully under the trees. This reptile and its close relatives have recently undergone taxonomic revision – to scientists, it is currently known as Gopherus morafkai.
The tortoise’s powerful front legs are clad in rows of thick, hard scales that assist in digging and may help the turtle resist serious injury from predators. When threatened, the tortoise tucks its head in and then covers its front with these remarkably well-armored legs.
A few days ago, I went out on a walk with a naturalist-friend. He shared a special area with me, a mature mesquite bosque with a remarkably rich, lush understory. I was deeply touched by the feel and presence of this almost subtropical woodland. The image below provides some insight into the kind of verdant growth that this “desert” valley is capable of hosting.
A jungle-like wall of vining plants drapes over young trees and shrubs in one of the most lush, beautiful velvet mesquite bosques I have ever seen. Just beyond the reach of this image was a barbed-wire fenceline. On the far side of the fence, cattle grazed – the ground under that part of the forest had been virtually wiped clean, transformed into a deeply impoverished world with respect to native plants and wildlife. Mesquite bosques as rich and fecund as this one have become very rare – cattle are commonplace. How is this right?
The lightning bolt slammed into the ground with thousands of times the force and speed of a sledgehammer blow on an anvil. It struck so close to me that I heard no thunder, only the unmistakably loud, monstrously powerful “snap” that is characteristic of a bolt that hits far too near to its observer. I had been sitting on my bed reading when it happened; I knew instantly what had occurred, for this was not the first time that lightning had struck so close to me that no thunder could be heard. Many years as a guide in the wilderness mountains of Montana had brought me into near-contact with lightning along high ridges at timber line more than a few times. It is one of nature’s most lethal forces when it strikes living creatures, but the other side of lightning is that it is one of the world’s most quintessentially important life-giving phenomena. For the full story, see pages 204-205 in my book, The Life of the San Pedro River. The next morning, I found the place where the bolt had impacted. A tape measure revealed that the lightning had struck 53 feet away. The electromagnetic pulse from that bolt fried our telephone system and our computer router.
The storms of this year’s monsoon season in southern Arizona have been wonderful – thus far, our rain gauge has registered 9.56 inches of rain since mid-June, resulting in a grand resurgence of life all across this hot and formerly dry landscape.
On the morning of August 20, a serious storm pounded the ground with so much rain that the area around our buildings became an unbroken sheet of water. I could hear toads starting to call from our overflowing bird pond. Before long, dozens of spadefoot toads came out of their underground lairs to join in the party, all of them hopping and swimming through the flooded landscape in beelines toward the pond. This was a critical time for the amphibians, for in a normal year, they get only one or two brief chances to breed. It was also a rare sight, for I have never seen such activity in the daytime…but this was a doozy of a storm.
Mavis – the female half of the raven pair that we share habitat with – takes shelter from the storm under the roof of our shed.
As the rain subsided, I stepped outside. I heard the familiar roar of one of our local washes that had become engorged with flood water. A short walk of a quarter mile took me to a place where I could look down from the edge of a vertical cutbank at the flowing wash…
The view from the cutbank after 2.6 inches of rain from a single storm swelled Hot Springs Wash with roiling floodwaters. Only a single channel is visible in this image. The waters braided across the broad wash floor in an ever-changing – and growing – number of channels. Powerful floods are characteristic of desert washes with large drainage areas (this wash drains an area of about 100 square miles) and steep slopes in their headwater areas.
Next, I walked over to see what was going on in the little pond – there were eight pairs of Couch’s spadefoot toads in amplexus! A couple days later, after thousands of toad eggs hatched, our pond was teeming with wriggling throngs of tiny tadpoles.
Couch’s spadefoot toads mating in our pond. Each female usually lays hundreds of tiny eggs during such couplings, as the male releases sperm into the water.After the mating frenzy, myriad spadefoot eggs clung to every blade of grass afloat in the water.
Later in the day, Kathleen and I walked down the road to have a look at where the big wash crosses the road. The sound of the flood grew loud as we approached a point where we could see the flow, over 300 feet in width. The dirt road – the only road that serves the entire valley – had become impassable once again. In the midst of the turbulent flow, where the waters ran deepest, trees were being tossed around like toys, ripped from their root-bound moorings as they sped downslope toward the San Pedro River. Hundreds of tons of sediment, gravel, and rocks were being transported toward the floor of the valley in a rip-roaring tumult of rain water.
A view of the flood as it obliterated the roadway where it crosses the usually dry bed of Hot Springs Wash. During the twenty summers that I have seen this wash respond to rainfall events, only twice have I witnessed it running larger than this.
As we were watching the floodwaters, I climbed to a higher vantage point, where I discovered this beautiful Sonoran gopher snake. The snake allowed me to gently approach within a foot or so. This was a fine specimen, over 5 1/2 feet in length.
A few hours later, the sun had melted down into the nether regions of the western horizon. My wife and I walked outside around 11:00pm to listen to the night sounds. After turning off our flashlights, we witnessed something that is seldom seen here – fireflies!! Few of Earth’s creatures are capable of instilling such an immediate and compelling sense of awe and wonder as fireflies are. They were emitting distinctive, paired flashes of remarkably bright green light – in so doing, they identified themselves down to the species level. We were seeing southwestern synchronous fireflies, Photinus knulli.
A couple of days after the big storm, I walked down to the San Pedro River. Many areas within the river’s drainage had received substantial rains, bringing the river to life. Here, el Río is surging along with a flow roughly 180 feet in breadth and over six feet in depth.
Downstream, a group of turkey vultures was roosting in a pair of dead cottonwood trees. Dead trees are an essential and important component of all forested areas on Earth. All too often, humans fail to recognize this aspect of our planet’s ecology. Our culture – embedded in the ecologically dangerous Abrahamic concept of land use – (the land is here to produce our milk and honey, for human use) – tends to see dead trees as “going to waste.” “Salvage logging” of our national forests after wildfires is an exemplification this anthropocentric view of our living world.
The rainy season brings twilight flights of thousands of buprestid beetles just above the canopy of our local mesquite bosques. Here, a very rare sight unfolds as a female Polycesta aruentis everts her ovipositor to lay her delicate eggs deep within the sheltering crack of a mesquite stump, where they will be out of reach of the sun’s touch. Her larvae will hatch to bore their way through the wood, leaving tunnels in their wake that greatly facilitate the entry of fungi and other agents of decomposition. Thus, insects like this play a critically important role in forest ecology.
A half-grown (about four inches in length) Sonoran desert toad enjoys our bird pond after a rain. These amphibians grow to prodigious sizes. If I am not mistaken, they are the heaviest toads native to North America.
Living in remote parts of the desert southwest demands some important learned behaviors. Only fools step outside without looking first. This diamondback had just finished crawling across my entry steps when I took this photo. Snakes of all kinds are always welcome on our property – but continuous caution when one ventures outdoors is an imperative part of living here.
