Giant Saguaros: From Tiny Seeds to Towering Titans

When we think of saguaros, we usually marvel at the big ones, the 20 and 40-foot tall gains that have lived for over a century, enormous cacti that make the Sonoran Desert such a unique landscape. But  a saguaro begins, as do all living things, very small. A single saguaro seed is not much bigger than the size of the period at the end of this sentence, glossy and black. Each tiny seed contains all of the information necessary to grow into a forty-foot tall towering titan, if it is fortunate to land in the right place and not get eaten.  

I often search for the smallest saguaro I can find while hiking the desert preserves in and around Phoenix, especially the pea-sized seedlings that have a pair of succulent leaves topped by a soft tuft of spines and two threadlike rootlets that cling to the soil. Birds, mice and squirrels harvest most of these tender morsels before they reach a month old, so the chances are slim to find one at this early stage. The statistics are astonishing but grim:

*An average healthy, mature saguaro can produce more than 150 fruits in one season.
*Each fruit may contain more than 200 seeds.
*Thus, one saguaro can produce over 300,000 seeds each year.
*Over a century of reproductive life, a single large saguaro may bear more than 30 million seeds.
*Out of all those seeds, only one out of a thousand will end up in conditions where there is enough moisture to enable it to sprout.
*Ultimately, only one out of several million seeds will become a full-grown cactus in the wild due to predation of fruit, seeds and you cacti by many different creatures, including humans. Freezing, drought, and flash floods also take their toll on young cacti.
         In the shelter of a "nurse tree" or shrub, usually a Palo Verde or Mesquite, a young saguaros chances are much higher. Shade an moisture will prevent it from getting dehydrated during those tender years. Dispersal by birds that eat saguaro fruit is the most effective for seeds to land in suitable germination and establishment sites, as they deposit them in droppings while perched on tree limbs. Saguaros generally out-live their nurse plants, but they do not parasitize them in any way.
         There is no simple formula by which to estimate the age of a saguaro because they do not have growth rings like woody trees. Aging a saguaro by height depends on location, especially the amount of rainfall they receive. Data from measurements taken of saguaros at three locations in the wild show that at 100 years, height can vary from between 15 and 30 feet. A 1 to 3 inch tall wild saguaro is about 10 years old. At about 25 years, a wild saguaro will be 2 to 3 feet tall. Two hundred years is a long life for these giant cacti.




















Late April to early June is the season for saguaro blossoms. the official state flower of Arizona. Each flower blooms for only one night, opening after dusk and remaining open until early afternoon the next day. A new set of flowers blooms for up to six weeks every night, attracting numerous pollen and nectar feeders, including long-nosed bats by night, doves and many species of insects during the day. Most of these creatures also serve as pollinators for the saguaro.

Wild saguaros begin producing flowers and fruit at about 50 years, but this ranges from 30-75 years, depending on available moisture. Flowering age corresponds to between 6 and 8 feet tall. Saguaros begin producing "arms" after 50-70 years, which also increases flower production, since flower buds emerge at the top of each arm.
         A mature saguaro with many arms can weigh up to 9 tons: a hydrated stem weighs about 80 pounds per foot, so a 30-foot tall single-stemmed saguaro may weigh about 2400 pounds. The tallest recorded specimen once lived near Cave Creek, AZ, reported at 78 feet tall before it died in 1986. The current record for the tallest living saguaro is a dwarf in comparison at only 45.3 feet tall and a circumference of ten feet.
         No matter what their size, any saguaro you encounter is a miracle of desert survival.

Coming to Terms with Termites

If we could make a window into the subterranean environment, we would see a world as intricate and alive as what we know above ground. This is the domain of one of our most common household pests, the Desert Subterranean Termite. In the wild, all termites play an important role helping to break down dead plant material and dung, insuring that nutrients are recycled back into the soil. Their tunnels help to circulate air and water in the soils, which is necessary for healthy plant growth. They are also an abundant source of food for lizards, birds and larger insects. In some African and Indonesian cultures, termites are a common snack for people too, usually served roasted and lightly salted. Yum!

More than 2600 species of termites are known around the world; less than 10% of those cause damage to buildings. In the U.S. we have forty-five species; eighteen are found in Arizona, but only four of those species commonly become pests when they feed on man-made structures. Of these, the Desert Subterranean Termite (Heterotermes aureus) is the most pervasive native termite of the Mojave and Sonoran Deserts in California, Arizona and Mexico.

Like ants and honeybees, termites are colonial, with several functional roles or "castes." Each colony begins with a queen and king, who are responsible for mating and producing eggs. Although a newly mated pair needs to care for their first set of offspring on their own, eventually they produce thousands of workers whose duties include feeding and grooming the royal couple, as well as eggs, larvae and each other. The tiny quarter-inch long workers cooperate to build extensive tunnel and gallery systems that reach as far as three meters below the surface and may house up to 300,000 termites. About 10% of a colony develops into sterile soldiers equipped with fierce jaws that can crush other insects, especially ants, that may invade a colony.

During evenings in late summer months, you may notice winged termites, also known as "alates," swarming outside, or if you are unlucky, inside your home. These termites, unlike workers and soldiers, are able to mate and reproduce. If a male and female find each other and a suitable place to burrow into the soil, they will start a new colony. Thousands of alates will swarm from a mature colony each year, but only a few escape the fate of death by predation or other natural causes.

Termites are dependent on specialized bacteria, fungi and protozoans in their gut that are able to digest wood. By sharing food with the rest of the colony, workers also transfer gut organisms to new larvae and each other. This behavior is one way that toxins used for termite control get distributed. Any termite that encounters the toxin will return to the colony, where mutual feeding and grooming will cause the poison to spread throughout the population. It normally takes just a few days for an entire colony to be infected with the toxin and die.

Either you've had them in your home, or you will, but if you can suspend your horror and disgust at the idea of tiny bugs munching away inside your walls, the world of termites is actually quite fascinating. Despite their potentially destructive impact to our homes, termites are critical to the health of our desert ecosystem. You can do your part to reduce the introduction of toxins
necessary to destroy them by creating termite resistant physical and chemical barriers to your house. This way, termites will carry on in their important ecological role in the desert around, but not inside, your home. Some ways you can minimize the likelihood of termites entering your house include:

*Make sure there is no yummy termite food next to your house, which includes any kind of wood, whether it is firewood, crates, building materials or furniture.
*Keep areas next to the house dry and free of irrigation. Termites prefer to forage in moist soils.
*Be sure that floor joints and cracks are sealed and treated with termite repellant before you install wood flooring.
*Do regular inspections around your foundation and interior walls to catch any termite activity before it creates serious damage. Call a certified professional to chemically treat any problems.

For more detailed information on local termite ecology and control, check out the Arizona Cooperative Extension document: Arizona Termites of Economic Importance (2005).

Note
If you are buying or selling a house in Arizona, it is customary for the seller to be responsible for any termite protection that is deemed necessary before closing on a real estate contract. Usually this involves an inspection and a treatment that includes a minimum one-year warranty if any active termites are found.

Heron Heaven

Great Egret

On any day of the year, if you visit one of the many suburban ponds or waterways scattered throughout the Phoenix suburbs, you will almost surely see one of our most elegant resident birds, a heron called the Great Egret. They are easy to recognize, standing at three feet tall with long dark legs, a slender yellow beak and pure white feathers. If you look more closely, you are also likely to spot several other species of herons: Great Blue Herons, Green Herons and Black-crowned Night Herons are better camouflaged, but share the same habitat. Another white heron, the petite Snowy Egret, about two feet tall with a dark beak and yellow feet, is also fairly common.

Great Blue Heron

If it weren't for Boston tea parties, however, we might not be able to witness the majesty of herons in our suburbs today. A little more than a century after the raucous dockside tax rebellion that ignited the American Revolution in 1773, two Boston socialites, Harriet Hemenway and Minna Hall, started another revolution in 1896 by hosting a series of more civilized gatherings to advocate bird conservation. Brought together over tea and biscuits, more than 900 women organized to ban the massacre of birds for their feathers.

During the late 1800's, the breeding plumage of adult Great Egrets was especially coveted by hat fashionistas. (Egret is derived from the French word aigrette, which means "silver heron." An aigrette is also the term for a decorative head ornament made with feathers.) These birds, and many other species, were nearly driven to extinction by hunters who provided feathers for the millinery industry. Efforts pioneered by the ladies of Boston eventually led to national and international laws that made plume hunting illegal. Egret populations have since made a dramatic recovery. This is one reason why the Great Egret was chosen as the symbol for the National Audubon Society, one of the oldest wildlife conservation groups in the country.

Long before we began building ponds and canals, herons have hunted along the Salt, Gila and Agua Fria rivers that once flowed freely through the Central Valley. Some of the birds are year-round residents; others winter here and return to breeding areas further north during the summer. Along wilder sections of the Gila River south of Goodyear (SW Phoenix), you can see large colonies of herons nesting and roosting in cottonwood and mesquite forests.

Anywhere there are fish, even if it's a small goldfish pond in your backyard, herons are able to detect their favorite food and may soar in for a snack. The Arizona Game and Fish Department, municipal Parks and Recreation Departments and local homeowner's associations assist with enhancing heron habitat by stocking ponds and reservoirs with fish. Although their primary intent is to provide angling opportunities for urban residents, herons and other wildlife benefit from fish stocking. Other ponds are stocked and managed specifically for wildlife, including a peaceful retreat in Glendale's Thunderbird Park at 59th Avenue and Melinda Lane, where special viewing blinds have been constructed for anyone who likes to sit and watch wildlife. If you are as patient and still as a heron, you may witness one catching its dinner.

Herons gather at a pond in north Glendale

Beyond Bermuda

A neatly trimmed lawn is perhaps the most iconic emblem of the American suburban lifestyle. Many people regard a cool patch of green as an essential ingredient of a civilized landscape, a symbol of serenity and order. Whether your favorite turf is in the form of a ball field, playground or a merely decorative feature of your own front yard, lawns are living communities of plants and animals, as well as recreational havens and design elements.

Bermuda Grass

The most common species join local lawns and playing fields is Bermuda Grass (Cynodon dactylon), a tough turf that was imported from southern Africa centuries ago to enhance grazing pastures. In the U.S., the grass is named after islands in the mid-Atlantic ocean that are presumed to have been a stepping stone to their introduction to North America. It is also abundant in southern India where it is called arugampul or doob and has been used for thousands of years as a medicinal herb to aid in healing everything from rashes to diabetes.

Also known as couch grass, devil grass, wire grass and dogtooth grass, this heat-loving plant is both celebrated and loathed for being hearty enough to survive the scorching hot and arid climate of Phoenix. In the same aisles of garden supply centers that sell 50# bags of Bermuda grass seed, there are also multiple chemical treatments available to attempt killing it. Fortunately, or unfortunately, depending on which side you are on, Bermuda grass is extremely persistent, partly due to the facts that roots can drill down more than two meters into the earth and that small fragments of grass can propagate into full plants within weeks. However, Bermuda grass is not tolerant of cold, hence an annual ritual of thatching and over-seeding with ryegrass is practiced every fall by those who wish to toil away at watering, weeding and mowing all year round for the pleasures that green grass provides. While the leave so Bermuda will wither and turn brown through colder months, the roots remain very much alive but dormant, ready to spring forth when soil temperatures rise again.

Kidney Weed

Even in perfectly manicured lawns, there is always more growing between the blades than the favored type of grass. Dozens of plant species thrive on the moisture and fertilizer that lawn cultivation provides. Among them are dandelions, spurge, chickweed, pigweed, lawn parsley and mallow. Most people call the interlopers "weeds." On a professional playing field, such varied textures may cause interference in the game, but if your main aim is aesthetics, you may want to consider nurturing a plush carpet of kidney weed (Dichondra repens) or cheerful heart-shaped leaves and bright yellow flowers of wood sorrel (Oxalis corniculata). And everyone loves searching for good luck in a patch of clover!

Wood Sorrel

Lawns also attract wildlife, both predators and prey. Cottontails feast on the grass; owls, coyotes and bobcats feast on cottontails. The larvae or caterpillars of furry orange butterflies called "fiery skippers" chew on the leaves, attracting all kinds of birds that forage for juicy grubs. Even more birds relish the times of year when people scatter fresh grass seed to primp up a sparse lawn. Numerous other species of uninvited grasses also make their homes in Bermuda turf. If left un-mown, a lawn can rapidly become a thigh high meadow full of wildflowers and insects. In Africa, Bermuda grass is part of the vast savannah that supports herds of rhinos an impala. Of course, this is not what we strive for in suburbia, which is why I've chosen to trade in my patch of Bermuda for artificial turf!

Flame Skimmer 

Bugs bigger than birds might sound scary, but most folks agree that dragonflies are more mesmerizing than fearsome. One of our local dragonflies, the Giant Darner, is the largest dragonfly in North America, with a five inch wingspan, and an equally long body. That's just a tad larger than the wingspan of some of our common hummingbirds! Although they are carnivorous, there's no need to worry: dragonflies don't sting or bite humans, but feast on bugs that do annoy us, like mosquitoes and gnats.

Since these fascinating insects are in the taxonomic order Odonata, the sport of dragonfly watching is called "oding." If you are beginner in the sport, you may just want to learn the difference between two major groups, or suborders, the damselflies (Zygoptera) and the dragonflies (Anisoptera), which can be distinguished at a glance. Dragonflies hold their wings horizontally at rest; the more slender damselflies fold their wings over their back when perched.

Powdered Dancer

Dragonflies and damselflies were not granted official common names until 1996. Before that, they were known mostly by their Latin family or species name; at least two dozen families and more than 5,500 species are currently recognized world-wide. A dozen or so species are commonly seen around suburban Phoenix, and more than a hundred are known throughout Arizona.

None of them can walk, but all are exceptional fliers, able to cruise at about 10 mph on average, and put o 30 mph, beating their wings at thirty times per second. They can move in any direction as well as hover, inspiring aeronautical engineers to study them in detail for clues to better mechanical design.

However, it is the monstrous looking aquatic larval stage that earned the group the common name "dragon" and the Latin name, Odonata, which means "toothed," for an over sized spiny jaw that extends like an arm to grab prey. Dragonfly larvae, also known as nymphs, live in freshwater ponds and streams where they hunt other insects, tadpoles and small fish. You can easily spot a damselfly nymph by the three feathery looking gills at the tip of their abdomen or "tail" and by the way they wiggle their body as they swim through water. The gills of dragonfly nymphs, in contrast, are inside their body. They move in quick bursts by squirting water out the end of their abdomen like miniature underwater jet boats.

Exuvia or husk of larva 

When a larva is ready to transform into an adult, it crawls out of the water, cracks open its skin right down the middle of its back, and slowly crawls out to begin a few weeks or months of life on the wing. In most species, males and females look very different, and like birds, the males are usually more brightly colored than the females. Male dragonflies are also territorial, and will chase off other males that intrude on their favorite stretch of stream or shoreline, but welcome females. Once he does find a mate, he latches onto her neck with special claws at the tip of his abdomen. The pair mate in flight, making a "heart" or "wheel" shape with their long abdomens. He will continue to guard her so that she can't mate with other males.

To complete the life cycle, a female will lay between 500-2000 eggs. If you see a dragonfly dipping the tip of its abdomen on the water while in flight, it is a female laying her eggs, one by one. Damselflies lay their eggs in the stems of plants where the hatched larvae can easily crawl into the water. Nymphs live under water between one and five years before emerging in their full glory as winged dragons and damsels. Hot summer days are the best time to spot dragonflies cruising desert washes and urban ponds where they patrol for meals and mates, so now is the time to get out your binoculars and do some doing!

Learn more about local dragonflies at a website created by ASU professor Pierre Deviche and dedicated to Arizona dragonflies.

Sotol

Sotol (Dasylirion wheeleri) has become a staple of suburban landscapes in southwest desert communities because of its beautiful form, drought tolerance and easy maintenance. Archaeological records show that the plant has been popular with people for more than 10,000 years. To Ancient Puebloans, though, the plants were not merely ornamental. They collected and used the leaves for fiber to make mats and baskets. Young tender stalks and roots were roasted for food. Dried sotol stalks were used as fire ploughs, a method of fire making in which a dry stalk is rubbed in a wooden trough until the friction makes a hot cinder. Sweet pulp from the sotol "heart" was used to make a fermented drink much like mescal or tequila is made from agave. This drink is still popular in some parts of Mexico.

Perhaps the most stunning feature of sotol is the huge flowering stalk that emerges each May from the center of a mature plant. After a couple weeks of daily measurable growth, the sotol in our neighbor's yard finally bloomed last year. The sixteen-foot tall stalk rose from the giant rosette of sawtooth-edged leaves, luring swarms of honeybees and tiny colletid bees that came to gather pollen. I've been amazed by the rapid growth of flowering stalks for over a decade, but did not realize until recently that sotols are dioecious, meaning that there are botanical equivalents of male and female plants.

Male plants bear long curly bunches of pollen-producing flowers, which sort of look like Cheetos, but without the orange dye. The sheer magnitude of the stalk and all of that pollen is truly astonishing. Likewise, females bear thousands of seed-producing flowers. Although the bees harvest prodigious amounts of pollen, they do not visit the female flowers because there is no nectar to attract them. The females must depend on wind to deliver pollen for fertilization. From a distance, you can tell the two types of stalks from one another simply by noticing the presence or absence of insect activity: male stalks are swarming with bees; female stalks may have a bird perched on top, but no bees.

Despite the fact that there are thousands of sotols growing in the Phoenix suburbs, you are unlikely to find one in nearby desert preserves. The natural habitat for sotol is much higher than our fair city, in scrublands and grasslands over 4,000 feet in elevation. They are most common in the Chihuahuan Desert, which extends from southeastern Arizona through New Mexico to Texas and Northern Mexico.

If you grow sotol in your yard, you can save yourself or your landscaper from hassling with the spiny leaves by letting it grow naturally rather than "pineapple-izing" the base. Although this practice may have been a way for ancient people to harvest leaves for fiber, there is no need to remove them otherwise. Better to sit back and enjoy a shot of sotol, or just admire these hearty and majestic plants in you desert landscape.

What a Lizard Wants

A pair of Side-blotched Lizards  photo by Rick Halliburton 

When a lizard goes searching for real estate, their dream home has many of the same features we may have on our list: Beautiful landscaping, a sunny spot to relax in when it's cool, a shady spot to hang out when it gets hot, a neighborhood that is safe from predators and easy access to good food. They're not going to list granite countertops, but a large granite boulder to bask on would make a lot of lizards very happy.

Recent surveys in the Phoenix urban area by reptile biologists at Arizona State University have shown that, indeed, all fourteen native species of lizards in the area seem to prefer the same areas occupied by prime real estate. In an article called "Rich Lizards," PhD student Jeff Ackley and colleagues report that the diversity of lizards in the urban area is highest in more affluent neighborhoods. They call it the "luxury effect." Characteristics that tend to increase value for real estate also make for better quality lizard habitat. This includes: closeness to desert preserves, greater diversity of plants, more natural open space and less asphalt. Affluent neighborhoods also tend to have larger yards with more native plants and fewer lawns. A side benefit of all these features is that air temperatures are slightly cooler, especially during summer nights. This is because there is more shade during the day and a reduced "urban heat island" effect at night.

Regal Horned Lizard   photo by Kathy Darrow

However, each species of lizard has particular wants and needs that may limit where they can thrive, just as we humans all have various things that keep us most comfortable. What a Regal Horned Lizard needs most, for instance, is ants, and around here, a certain species of seed harvester ant: Pogonomyrmex rugosus. These ants prefer open flat areas where there are plenty of native seeds to harvest, so very few populations of Regal Horned Lizards have survived in the urban area. Flat ground is the first to go when development is planned.

Only two of the ten Phoenix desert preserves that have been surveyed have more of what Horned Lizards want: Deem Hills and Cave Buttes have enough flat ground to support healthy harvester ant populations. You will most easily find these reddish ants by looking for their nest holes, which are usually near the center of a 3-6 foot wide gravelly circle. After summer rains is the best time to watch harvester ants at work gathering seeds from afar, which they tore in special chambers below ground. Horned Lizards will seek out an active colony and snatch them up with their short, fat, sticky tongues. One of the ways biologist can tell if there are horned lizards around is by finding their fecal pellets (aka poop) nearby, which are masses of ant parts a couple of inches long.

Desert Iguana  photo by Brian Sullivan

What do other kind of lizards want?
*Desert Iguanas want creosote bushes to feed on and lots of space to run.
*Chuckwallas gotta have crevices to climb into, just the right size, so they can take a deep breath and wedge themselves in. Plus, they are picky eaters: palo verde, globe mallow and showy goldeneye are some of their favorite foods.
*Tiger Whiptails like rodent burrows to dodge into for shade and protection from predators.
*Ornate Tree Lizards want trees to climb, but vertical walls will do, and thus, they are the most abundant type of lizard in the urban area.

Ornate Tree Lizard photo by Kathy Darrow

What all lizards really want, though, is to be left in the wild with room to roam, places to hide and where it's easy to find their favorite foods. you can add a little luxury to an urban lizard's life, and maybe even boost your own real estate value, by planting native trees and shrubs in your yard, plus a large boulder or two for basking.

To learn more about local lizards, check out the website for "A Field Guide to Reptiles & Amphibians of Arizona" by Thomas Brennan and Andrew Holycross: www.reptilesofaz.org

African Influence

 

Urban ecosystems are cosmopolitan, blending plants and animals, as well as people, from all over the world. In Central Arizona, there is a distinct African influence, especially in the wildly diverse succulent plants that are supremely adapted to hot, arid climates similar to the Sonoran Desert. In addition to fleshy leaves and stems, most succulent plants have thick waxy skin and specialized metabolism, traits that increase their ability to conserve water. Here is a small sample of the most common African succulents that you are likely to encounter in you daily life in the Phoenix suburbs.

Aloe (Aloe vera) has become an element of almost every American household because of its use in cosmetics, skin treatments, herbal medicine and food products, as well as for landscaping and for ornamental houseplants. There are over 500 species of Aloe, ranging from small rosettes to giant trees, all native to Africa and the Middle East. Many species have become naturalized in arid regions around the world wherever there are human settlements. (Agaves, which are native to arid lands in the Western hemisphere resemble aloes in form, so are sometimes called "American Aloe," but are not closely related.) The thick leaves of Aloe vera are filled with slimy gel that is extracted and marketed for everything from laxatives to sunburn treatments. The Bible references aloe as part of the embalming mixture used to wrap the body of Jesus Christ (John 19:39).

Moroccan Mound (Euphorbia resinifera) is one of hundreds of Euphorbias that have been imported from Africa for landscaping. Euphorbia is one of the most diverse plant genera in the world, with nearly 2000 species, including poinsettias and leafy spurge. Many African species of Euphorbia have spines as well as succulent stems, making them resemble cacti, which are indigenous to the Western hemisphere; this is a classic example of convergent evolution. If you look closely at the tiny flowers of Euphorbias like Moroccan Mound, you will see that they are completely different from showy cactus flowers. Most Euphorbias also have thick white sap, or latex; cacti do not. The sap of Moroccan Mound is called resiniferatoxin, and is renowned for being rated at 16 billion Scoville heat units, which is one thousand times hotter than pure capsicum, the spicy ingredient of chili peppers.  Handle with care!

Pencil Tree (Euphorbia tirucalli), also known as Firesticks because of the flaming red stem tips, is super easy to grow and can flourish into a large tree with little to no irrigation. Like most other members of the Euphorbia family, it oozes milky sap when a branch is broken or cut. (Natural rubber is made from the latex of another member of this plant family that is native to Brazil, Hevea brasiliensis.) Some have dubbed this plant a "miracle tree," claiming that the sap can be used to treat a broad suite of ailments ranging from warts to scorpion stings. However, beware! Many people suffer painful skin rashes and eye irritation when exposed to the sap or even just vapors from the plant. There are also reports that Nomadic hunters in Africa have used the toxic sap to poison their arrows for small game and to kill fish.

Elephant Food, Pencil tree and a columnar Euphorbia
grow together in a giant pot in front of a local grocery store

Elephant Bush (Portulacaria afra) was imported from South Africa, where wild populations of this evergreen succulent shrub are an important food source for elephants, as well as other wildlife, including tortoises. In Africa, they call it "spekboom." The cut stems of Elephant Bush easily regenerate into new plants, a characteristic that may have evolved as a symbiotic relationship with elephants, since they scatter plant fragments as they feed. There is some speculation by scientists that growing Elephant Bush on a large scale may be useful to store carbon dioxide in order to reduce atmospheric levels of the gas that contributes to global climate change. This would dovetail nicely with objectives to improve wildlife habitat in Africa.

To learn more about succulent species from all over the world, including cacti, visit your local chapter of the Cactus and Succulent Society, which holds monthly meetings at the Desert Botanical Garden in Phoenix.

Skunk Creek: Heart of Northwest Phoenix, AZ

If you want to truly understand the Sonoran Desert, you need to walk the dry creeks and washes before and after a flash flood. In northwest Phoenix, Skunk Creek is the heart of the landscape, collecting water from sixty-five square miles of mesas, hills and bajadas.

A thin dotted-and-dashed blue line on the map, Skunk Creek is a seasonal stream that stretches about thirty miles from its headwaters on New River Mesa northeast of Anthem, to its confluence with New River just south of Bell Road and west of Highway 101. The creek bed runs roughly parallel with and between two other large washes, New River and Cave Creek, cutting a diagonal swath through dense suburbs. In the wilder sections, Skunk Creek is a quiet, sandy wash more than 360 days a year, where a person can walk up the middle following tracks of coyotes, black-tailed jackrabbits, lizards and roadrunners. And yes, there are skunks too, at least four kinds, that have historically roamed the corridor.

For thousands of years, Skunk Creek served as a travel corridor not only for wildlife, but also for ancient people migrating between the high country north of Phoenix and the Gila River in the south Central Valley. Today, we can still find signs of small settlements along the way, where people farmed maize, cotton and squash. Fragments of clay pots and stone tools are scattered around foundations of pit houses. Hundreds of people marked their passing by pecking petroglyphs in black basalt rocks at Hedgepeth Hills, just west of I-17 at Deer Valley Road.

Much of Skunk Creek is still as wild and free as it was just half a century ago when the north valley began to be developed. You can still walk the wash from its headwaters all the way to Carefree Highway. From there it begins to be tunneled under roads and channelized in order to control flooding that would normally spread for miles beyond the natural stream channel. In the heart of North Phoenix there is a paved recreation path, dubbed "Skunk Creek Linear Park," that winds above the wash for about four miles between 51st Avenue & Utopia down to 73rd Avenue & Greenway. The path connects with a network of city trails that follow other washes and canals. But when the big rains come and the creek starts flowing, you better find some high ground.

U.S. Geological Survey water gauge records show that on August 1st, 1964, Skunk Creek spiked to 11,500 cfs (cubic feet per second). This record high was trumped a couple of months ago on August 19th, when monsoon storms dumped nearly four inches of rain in the headwaters, causing Skunk Creek to surge over 13,000 cfs and jump its banks to flow down the I-17. That's about the same flow going through the Grand Canyon most days of the year. Imagine a small house (~1300 square feet) full of water flowing by every second. That's a LOT of water!

There was plenty of news coverage of that event and rescues that ensued when morning commuters encountered the deluge. But the real news is the life that thrives when the water recedes. Toads emerge and lay eggs. Seeds that may have been waiting for decades to be scoured and soaked, germinate. Shrubs and trees grow lush crops of new leaves. Flowers bloom. Insects hatch. Birds and rodents feast, and so do coyotes and bobcats. Life that has evolved here is well adapted to these torrential events, resilient to what may seem tragic to humans. A flash flood is lifeblood for the desert.

Know Your Watershed
Skunk Creek is a tributary within the Middle Gila Watershed, just east of New River. About three miles downstream from the confluence with New River in Glendale, water from Skunk Creek mingles with Agua Fria, which runs for a few more miles before it joins the Gila River. This area is known as Tres Rios (Three Rivers), because Agua Fria and Rio Salado combine to become the Gila River. About 200 miles southeast of Tres Rios, a little east of Yuma, all of the water from these drainages joins the mighty Colorado, which on a rare day, might reach the Sea of Cortez and the Pacific Ocean, another sixty miles south.

Happy Valley Trails

One of the criteria at the top of our list when we were searching for a house in Phoenix twelve years ago was that we would be able to hike and ride our mountain bikes in the desert without having to drive more than ten miles to the nearest trailhead. Better yet, we'd be thrilled to have trails within walking distance from our front door. We found the perfect place, confirmed after a walk in the rain into Deem Hills Recreation Area from our prospective home just north of Happy Valley Road. Perhaps we became intoxicated by the sweet smell of creosote in the air, or captivated by the rainbow arching over the saguaro-studded ridgeline. A contract was signed the next day and we've been hiking and biking out our front door nearly every day since!

Miraculously, the number of trail miles to hike and bike near our neighborhood has multiplied over the past decade. The City of Phoenix expanded the formal trail system in Deem Hills from a few miles to over eight in 2010. A year later, fourteen miles were carved into the hills of the newly designated Sonoran Preserve just east of I-17, well within our ten-mile circle. Less than a year ago, twenty more trail miles were created, along with expansive parking and restroom facilities at Apache Wash, just south of Carefree Highway. To the south and west, Glendale's Thunderbird Conservation Park and Peoria's WestWing trail system double again our options.

These city parks and preserves are just a sampling of the network of desert trails that have earned the Phoenix Metropolitan area a spot in the top ten of the world's most Biophilic Cities, a program that recognizes urban areas that have intentionally incorporated ways for people to interact with natural landscapes into daily life. Grand designs for a 242-mile Maricopa Trail that will link all nine Maricopa County regional parks and a 336-mile CAP Recreation Trail planned to extend the entire length of the Central Arizona Project canal (CAP) are also underway, which would make the Central Valley of Arizona one of the most bike-able, walk-able and equestrian friendly suburban areas in North America.

Come see…and walk, or ride...for yourself!

The Many Superpowers of Lesser Nighthawks

A sure sign of summer in Phoenix suburbs is the return of Lesser Nighthawks that migrate north from Central and Sough America to breed and feed in the Sonoran Desert, while at the same time, many people flee to escape the heat. Between late April and October, moonlit nights and early mornings are excellent times to catch a glimpse of these ghost-like birds, as they silently dance through the air catching insects. In dim evening light, flashes of white on the tips and tails of dark silhouettes may be all you'll see, but near a lighted ball field or street light, you can get a better look at the long, pointed wings and striped plumage that make them resemble a small falcon. Nighthawks are not hawks at all, though, and lack the fierce talons and sharp beak that are primary hunting tools for birds of prey. Instead, their erratic float-and-flutter flight pattern, wide mouth, tiny beak and tiny feet are some of their most notable features.

Their dawn and dusk, or crepuscular, feeding habits and gaping mouth earned them and others in their family of birds the common name, "nightjar." Somehow they were also dubbed "goatsuckers" because they were once believed to steal milk from nannies, but there is no hard evidence for this bit of folklore. The wide mouth has also led many naturalists to speculate that nighthawks are capable of picking up their own eggs and moving them away from would-be predators, or into shade during especially hot days, but again, well-documented observations are lacking.

However, it is true that nighthawks are masters of camouflage at every life stage. As adults, striped and mottled brown and gray feathers enable them to blend perfectly with rough-barked tree branches or a
pebbly desert floor. Unless you just happen to disturb one by walking near a nest or roosting sight, it is extremely rare to see a lesser nighthawk during the day, even if you are ardently searching for one.

A female nighthawk has the additional superpower of being able to tolerate surface temperatures over 110 F as she shelters her pair of eggs or newborn chicks with the shade of her own body. The mottled eggs are laid on open ground with not other nesting material to insulate them. After eighteen days of incubation, the downy calico chick hatch and are ready to fly within a couple of weeks.

One strategy that nighthawks use for keeping cool during our scalding summers is called "gulag fluttering," which is basically a kind of panting, or evaporative cooling. The extra wide mouth, in this case, acts like a miniature swamp cooler, helping to lower body temperature. Lots of birds do this, but nightjars can also vibrate their throats to enhance the cooling effect.

Acrobatic flight, deep camouflage and extreme heat tolerance are just a few of the nighthawk's superpowers.

What are yours?

Javelinas in the Hood

The signs are everywhere if you know what to look for: seedy piles of scat; hoof prints in the dust; large bites taken out of cactus pads; shallow depressions in the shade of mesquite trees and the occasional tuft of coarse dark gray hair. If you have a good nose, you might smell their peculiar musky scent. Collared peccaries, better known as javelinas, are frequent visitors to many suburban neighborhoods in Arizona. However, unless you are nocturnal like they are, actually seeing one is quite rare.

Stetson Hills resident, Jennifer Moore, was once woken at 2:00 am by the sound of snorting and huffing outside her open window. When she looked out to see what was going on, there was a herd of eight javelinas trotting single file down the sidewalk. Another neighbor regularly sees them very early in the morning outside their view fence as the animals make their way to daytime shelters under nearby palo verde trees. A more recent report came from a neighbor who witnessed a pack of coyotes gorging on the carcass of a large javelina boar along one of the neighborhood trails.

Suburban habitats around Phoenix provide a smorgasbord of some of the javelina's favorite foods, including jojoba nuts, acorns, cactus fruit and pads, mesquite pods, agave, plus flowers, fruit and bulbs. Like their distant cousins, wild boars and pigs, javelinas are opportunists, so will happily eat your garden tomatoes, squash, birdseed or a bowl of dog food. By night they may be munching in  your yard, but during the day they will retreat up washes into the desert where they can rest unseen until the sun goes down. The Deem Hills are home to at least one small herd of javelinas that considers the neighborhood of Stetson Hills to be part of their territory.

They are named for their small spear-like, or javelin-shaped, tusks that grow from the upper jaw of both sows and boars. Also recognized by their peculiar flattened heads and long "collar" of bristly white hair, javelinas are reputed to have very poor eyesight, but keen senses of smell and hearing. They are common throughout the Sonoran and Chihuahuan deserts, all of Mexico and Central America and down into Argentina where they also inhabit tropical rain forests. In fact, paleontological research suggests that javelinas evolved in rain forests and have gradually extended their range to North American deserts. Archaeological evidence indicates that they did not inhabit northern and central Arizona until the late 1600's. Severe winter weather limits their range further north.

Javelinas are one of the few large wild mammals that breed year round, so it is not unusual to see pairs of tiny, red-haired piglets scampering to keep up with the rest of the family. About the size of a cottontail rabbit, the one-pound piglets are ready to run within a few days of being born. Although the mortality rate for javelinas is over 50% within the first year, those who make it beyond their youth may wander the desert for up to a decade. Humans, coyotes, bobcats and mountain lions are their main predators. Although javelinas are generally gentle animals, they do have a reputation for being aggressive defenders of their young. In any encounter with wildlife, it is best to not get between a mama and her babies!

As with most wildlife, javelinas are more threatened by humans than the other way around. To avoid any chance of unwanted aggression between you, your pets and a frightened javelina, refrain from artificially feeding or watering them, and keep pet food indoors.

Blackbirds: Pastry Surprise or Avian Pirates?

"Four and twenty blackbirds baked in a pie" is one of the more memorable lines in nursery rhymes passed on from eighteenth century England. There are many interpretations of this verse, but the two most cited are that there were actually recipes for live birds to serve as surprises at royal banquets; or that the entire poem is a secret code advertising for crewmen to contract with Blackbeard's ship.

In Europe, where this poem originated, one of the most common "blackbirds" is the starling, which was imported to North America in the 1890's as one of the menagerie of over sixty bird species mentioned in Shakespeare's writings. (The bard's play, Twelfth Night, is the oldest known source for the line "Sing a song o' six pence.") On many spring mornings, you might see starlings grazing local lawns and parks along with flocks of several types of North American blackbirds, which include cowbirds, grackles, Brewer's blackbirds, as well as the more colorful yellow-headed and red-winged blackbirds. This is especially true in winter months, when many birds congregate in mixed flocks while feeding.

Female grackles                                                        photo by Rick Halliburton

In the official blackbird family, Icteridae, males and females are often mistaken for completely different species because they look so different. Females' feathers are designed for camouflage, dressed in drab brown rather than black. Showy males are up to 60% larger than females and wear sleek black feathers with sheens of blue, green and purple. Blackbirds tend to thrive in the company of humans in both agricultural and urban settings, often in noisy flocks of hundreds, thousands or even millions. Because of this, they are often considered to be "pests," but there is also much to appreciate about blackbirds.

Male grackles in courtship displays                      photo by Rick Halliburton

The most elegant of this group are the male Great-tailed Grackles, with long fan-shaped tails, iridescent feathers and bright gold eyes. During their breeding season, the males perform ardent courtship displays featuring neck stretching, wing vibrations and tail fanning, accompanied by loud screeching and cackling. Some of this is competitive, so you'll sometimes see several males displaying at once as they vie for their rank in the local mating hierarchy. Both males and females are promiscuous, meaning that they all have multiple partners, although there tends to be more available females than males in most colonies. In this species, the ladies take care of nest-building and chick-rearing on their own. Thus, in some Hispanic cultures, a lazy husband who doesn't work is called a Zanate, one common name for a male grackle.

However, it is not completely derogatory to be called a Zanate, for they are also known as great vocalists. According to a Mexican legend, the grackle's diverse repertoire of whistles, chattering and squawks is said to represent songs expressing the Seven Passions of Life: love, hate, fear, courage, joy, sadness and anger.

Although the meaning of the nursery rhyme is ambiguous, one thing is for sure: if you take the time to watch a flock of blackbirds in their amazing synchronized flights, listen to their songs, or watch their elaborate courtship displays, you are sure to feel one of life's passions: joy!

From Down Under: Wattles, Kurrajongs & Gum Trees

Eucalyptus at a Phoenix golf course

One of the curious things about Phoenix is that there are more species of plants in the urban area than there are in the immediately surrounding Sonoran Desert. This is because we have imported hundreds of plants from other parts of the world. One of the highest-ranking countries for floral immigrants is Australia, with over eighty species of trees and shrubs that are cultivated and sold in garden centers all over the southwest. Since the interior of Australia is a desert very similar to central and southern Arizona, the plants adapt quickly to our equally hot, arid and sunny climate. A walk around the block of suburban neighborhoods around Phoenix is bound to take you past many Aussie ex-pats, especially wattles, gum trees and kurrajongs.

What wattles are to Aussies are known as acacias in North America. They all belong to the pea, or legume, family, but Australian acacias lack the spines or thorns that serve as self-defense from browsing mammals in North American ones. In place of thorns, the leaves of wattles contain alkaloids that are toxic to most animals. Over nine hundred of the world's thirteen hundred Acacia species are native to Australia. The most popular ones used for landscaping around Phoenix are the slender-leaved Willow Acacia (A. salicina) and Shoestring Acacia (A. stenophylla), both of which fill the air with sweet perfume from the puffball-like flowers every fall.

Kurrajong is the Australian aboriginal name for the bottle tree, a stout tree named for the shape of its trunk. The hard brown seedpods look like little canoes and the speckled maroon and white flowers resemble tiny jester caps. Indigenous people still use the bark of the tree to make fishing line, which is what "kurrajong" means in a now extinct language once spoken near Sydney.

Perhaps best known of the Australian flora are gum trees, or Eucalyptus, famed home of the kookaburra, a type of giant kingfisher. Just fifty miles west to Phoenix near Tonopah, Australian Outback boasts that it is "the worlds most extensive Eucalyptus browse plantation," providing North American zoos with leaves for captive koalas, which feed almost exclusively on Eucalyptus. There are seven hundred species in the world, and all but fifteen are native only to Australia. Here in Phoenix, around forty species are available through the garden trade. gum trees are revered for their beauty, shade and as fast-growing trees that provide wind breaks and screening in agricultural and industrial areas. That is why rows of eucalyptus are commonly planted along our roads and freeways and other not-so-scenic parts of the city, which is just about everywhere! Gum trees also make excellent pulpwood; the soft fibers are especially useful for making tissue paper. You probably have rolls or boxes of eucalyptus-based papers in your bathroom! In your medicine cabinet too, you may have throat lozenges, toothpaste or other cosmetics that contain eucalyptus oil.

Although it would be difficult to support a population of koalas in Phoenix gum trees, many native birds and insects have adapted to using them for food and shelter. most notably, monarch butterflies will roost and feed on Eucalypts during their annual migration. This is especially prevalent along the coast of California, where hundreds of thousands of monarchs roost during the winter months. In the annals of evolutionary biology, rapid adaptive responses to recently introduced species are a unique crucible for speciation. On the other hand, some people view any non-native species as a pest that interferes with the natural order of things, so many eucalypt forests are targeted for destruction, especially since they are also fire and windfall prone trees.

However, a special Red Gum (E. camaldulensis), affectionately known as "Mr. Big," is well-guarded and cared for not far from Phoenix at the Boyce Thompson Arboretum in Superior. The giant is reputed to be the National Champion of its kind, running neck and neck with a specimen in California at over one hundred forty feet tall and over six feet in diameter. Equally notable is Mr. Big's stats as the State Champion of all trees for height in Arizona, topping the runner-up Ponderosa pine in height by over thirteen feet!

Metamorphosis

If you had lived among the Hohokam people in this area hundreds of years ago, you would have looked forward to a bountiful harvest of hornworms at the end of monsoon season. The edible hornworms are the caterpillars, or larvae, of white-lined sphinx moths (Hyles lineata), and are named for a short spine protruding from their rear ends. This year, thousands of these fat, green caterpillars were seen along desert trails and city streets wherever there was an abundance of their favorite food, a sprawling annual plant called spiderling (Boerhavia spp.).  On the autumn equinox, there were so many trying to cross the road at Happy Valley and 33rd Drive that some sections of asphalt turned a lovely shade of chartreuse. If you were lucky enough to see them up close, you might have admired the colorful pattern of black and green stripes, accented by red spots along their sides, one of nature's most colorful works of art deco.

Still today, some indigenous people of southwest deserts gather and dry bushels of hornworms for food. In southern California, the Cahuilla people call them "piyatum." O'odham people of southern Arizona named the host plant "makkum jeej," which means "mother of the caterpillar." If you are going to try this local delicacy, it's important to pinch the head off and shake the guts out before you skewer them on a stick to roast over hot coals, according to one 19th century ethnographer who learned piyatum foraging skills from the Cahuilla. 

Lizards and birds also feast on hornworms, dead or alive, head, guts and all.

These finger-sized caterpillars are just one stage in the life cycle of an even more fascinating and beautiful moth. After they have eaten their fill, hornworms burrow into the soil and change into a brown, pod-like pupa. This resting stage varies from two weeks to six months, depending on the time of year and latitude where they live. During this time, the caterpillar transforms into a moth, a mysterious process still not fully understood by scientists. 

Longer days of spring induce moths to emerge from the pupae after spending the winter months underground. Pupae are able to perceive light and therefore, the number of hours of sunlight in a day. Here in central Arizona, there may be several cycles of metamorphosis between March and September, with moths emerging within two weeks of pupating. Additional environmental cues, including soil temperature and moisture, ensure that pupae remain underground so that the moth's emergence will coincide with flowers to feed on and the right kind of plants to lay eggs on so that caterpillars will have plenty to eat. This is a well-orchestrated miracle!

Since moths are mostly crepuscular (a fancy term for being active during shadowy hours of dawn and dusk) or nocturnal, they favor white flowers, which are more visible in low light. They are also strongly attracted by certain floral scents. Their super long tongues allow them to slurp up nectar from deep-throated flowers like evening primrose, jimson weed, columbines and night-blooming cacti. In the process, their furry bodies are dusted with pollen, which gets transferred to other flowers as they go about foraging, making them important pollinators for some species. 

As adaptable opportunists, white-lined sphinx moths often fly in broad daylight and will feed on any color of flower that has sufficient nectar. Their adroit hovering skills and rapid wingbeats make it easy to confuse a sphinx moth for a hummingbird at first glance, but the brown and white stripes on their wings and flash of orange on the underwings are unlike any hummingbird. During a moth's two to three weeklong life, their primary mission is to mate. Females may lay hundreds of eggs that hatch within a week or so to begin the cycle again.

This is all really interesting, but after consulting with several entomologists and texts, I'm still left wondering: "Why do caterpillars try to cross the road?" Is it just to get to the other side? And is it true, as some naturalists claim, that they tend to crawl north? It turns out, no one really knows. The caterpillars are probably looking for more food, or soft soil to burrow into. But wouldn't the vast corridors of hot asphalt deter them from what is almost always a suicidal journey? Fortunately, although we may notice them mostly on roads, there is still plenty of desert land for hornworms to inhabit without having to navigate through heavy traffic.