A Lizard with a Voice and More Monsoon Discoveries

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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. 

I discovered this little gem sheltering under an old piece of plywood. This banded gecko had lost its tail sometime in the past – the new one grew back lavender in color. A plump tail like this one indicates a good state of health, for the tail stores fats and water for the animal to draw upon during lean times, much like the tails of Gila monsters.

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.

This minuscule toadlet was photographed during its first day out of its natal pond, where it had spent the initial ten days of its life as a wriggling tadpole. At this stage of their lives, Couch’s spadefoot toads (Scaphiopus couchii), are tiny and vulnerable, fitting easily atop a mere dime.

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.

A white-lined sphinx moth hovers over a wolfberry bush, deftly inserting its long tongue into the tiny white flowers to feed on nectar. Note the bend in the moth’s tongue, a common trait among many species of sphinx and hawk moths.

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.

Since the first of this year’s summer rains on June 18th, we have received 4.25 inches of precipitation. Here is an image of our bosque taken just before the first rains.

The same area, photographed yesterday. The difference is clear – the greening understory is composed primarily of pigweed (Amaranthus palmeri), a native plant that is of great value to a wide variety of birds and mammals. If the rains continue, this vivd understory will be capable of reaching heights of six to seven feet.

This is what is left of a pigweed plant that grew after last summer’s monsoon rains. Pigweed retains much value to wildlife even after it has died and desiccated to a state like this one. Note that the plant has been recently fed upon, and that the cuts at the tips of each stem are sharply defined, cut cleanly at a steep angle. This is a signature left by the incisor teeth of a black-tailed jackrabbit. Nearly all rodents and lagomorphs (members of the rabbit order) leave such distinctive cut marks when they browse on similar types of vegetation. If deer or javelina had done this, the cuts would be rough with frayed edges and not cut at such steep angles.

Our area, the Middle San Pedro Valley, is served by a single dirt road that frequently endures serious damage after monsoon rain storms. I photographed this large wash near our home shortly after dawn, several hours after the flood had crested. The wet marks along either edge reveal a surging flow of flood waters that had crested at over 150 feet in breadth and four feet in depth. Flows this strong are quite capable of quickly carrying away almost any vehicle, even very large trucks.

An Incredible Explosion of Life

July brought us over six inches of very welcome rain! The summer monsoon – one of five distinct seasons here – has returned to southern Arizona after a two-year near-absence. Purple martins are cruising above the treetops and a family of Mississippi kites has been visiting us for days. We are seeing rattlesnakes on a daily basis. On sultry, warm nights, elf owls have been calling in the wee hours of the morning. Saguaros are fattening as they transport water in their tissues. Native grasses are  sprouting. The land and its life are rejoicing.

The changes on the landscape are incredible, happening with amazing rapidity and soaring fecundity. The mesquite bosque surrounding our home had been without a green understory during the entire past two years. Not any more! One glance out the window reveals a near-jungle of dense greenery standing five feet tall – much of it composed of one dominant plant with the unflattering common name of “pigweed.”

Fresh growth emerges with stunning speed and vigor after nitrogen-rich summer rains soak the land. This image is a week old; the understory plant community has doubled in height since then.

Pigweed is known to botanists as Amaranthus palmeri, and it is certainly not a “weed.” In the conventional sense, most of us consider weeds to be troublesome non-native plants. This one is a native species, and its presence speaks of great benefits to the land and its wildlife.

One of the primary winter forage plants for the deer that inhabit this river valley is pigweed. A good source of winter forage is critically important to wild ungulates. Rabbits, hares, javelina, and many rodents feed on the green plants in summer. Once the seed heads form, they tend to remain through autumn and winter on dead, standing plants. Great numbers of various species of sparrows winter in southern Arizona. The  seeds of pigweed are heavily fed upon by many of these sparrows and other native birds as well. Something that is very obvious, but often overlooked by many people, is the fact that the dense stands of pigweed are shading the ground. I can’t stress enough how important shade is in desert ecosystems! The ground retains much more moisture and soil temperatures are far lower, allowing fungal hyphae and numerous other microflora and microfauna to work in shallower horizons of the soil. This benefits all life.

The summer rains bring many creatures out of hiding. Among these are toads, countless insects, red velvet mites, and the largest millipedes living in the United States…

Giant millipedes spend nearly all of their lives underground, typically emerging only after monsoon rainstorms. This one was about five inches in length; some sources claim this species can reach up to nine inches in length. These fascinating, innocuous arthropods can live for ten years, growing longer as they add more body segments every time they shed.

I had taken several shots of the millipede, working close to the ground, before I noticed this small diamondback curled sixteen inches away. It never made a sound. When left undisturbed, these snakes are rarely aggressive. Their primary method of defense is stillness and excellent camouflage.

When one of these huge beetles comes flying by, it is guaranteed to get your attention. This is a palo verde root borer, measuring in at three inches in length. These beetles are another example of the many species that are brought out from hiding by the rains.

For many of our of native amphibians, monsoon rains furnish their only chance to reproduce successfully.  A strong population of spadefoot toads inhabits this valley, but they remain completely sequestered until strong summer rainstorms bring them up from their deep underground burrows. On July 3rd, the first monsoon storms rolled in –  a succession of two storms with plenty of lightning and life-giving rainfall. That night, the landscape was ringing with the voices of hundreds upon hundreds of spadefoot toads.

Couch’s spadefoot toad is the most abundant amphibian in the Middle San Pedro Valley, but only summer residents witness them.

A pair of Couch’s spadefoots mating. These amphibians must lay their eggs in water. In desert environments, the toads wait for summer storms to create suitable pools of water. Here, the male is grasping the female in a posture known as amplexus – when she lays her masses of eggs, he releases sperm into the water.

Spadefoot tadpoles mature more quickly than almost any other tadpoles on the planet – in as little as nine days. This is a species that has evolved to live in a hot, dry desert environment, where pools of water are not only rare, but tend to be very short-lived. It pays to mature quickly under such demanding conditions.

It is hard to say what to call the amphibians in this brief period of their lives; tadpoles or toadlets? At this stage in their development, the tails shorten very quickly. As newly formed toads appear, they can be seen hopping by the dozens out of their natal pond.

Just two days ago, despite the fact that I am always on the lookout for rattlesnakes, I nearly stepped on this one that was well camouflaged under the ramada. I am glad that we did not have an unfortunate interaction.