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.

3 thoughts on “An Incredible Explosion of Life”

  1. Ralph, I really enjoyed this edition of your blog. It never ceases to amaze me to learn about the resilience and complexity of the desert where you live, and the unique aspects of the mosque add to it. The pictures are excellent and really add to the fascination factor, at least for me…

  2. Thank you Ralph! Makes my day every time I see an new post and I always learn something new. We’re reveling here on the ridge top. Cloud watching could replace siesta. Green Glorious Green everywhere I look. Except for the orange Az. poppies, red ripening prickly pear fruit, purple……… I have been hearing a Great Horned Owl in the early a.m. Glad to know the Elf and Pygmy Owls are down your way as I’m not hearing as many as usual. Anxiously awaiting the appearance of this years baby/new Roadrunners. Any chance you might send me a photo copy of the river toad with the tarantula dinner? My granddaughter would be thrilled to pieces!! I can hear her WOW! and the giggle that goes with it!

  3. Excellent blog Ralph! You bring to light so many fascinating aspects of our Sonoran flora & fauna; the diverse life which sustains everything that flourishes when the precious rain comes during our Summer monsoons.

    Gilbert Urias

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