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!