Sunday, October 13, 2013


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. 

Wednesday, August 7, 2013

Toad Season

Couch's Spadefoot                                                Photo by Rick Halliburton
If you're looking for unique entertainment on a hot summer night, consider planning an evening out to listen to the local toad choir. WIthin 24 hours of a major rain event, desert toads will emerge from their underground dens and hop for up to a mile in search of a pool of water to breed in. The best seats in the  house will be near one of these warm pools during the first few nights after the storm. If you miss the post monsoon concert, tadpoles and toadlets will provide daytime entertainment for at least a week or two. 

A chorus of toads may include up to five species in our area, each adding their own rhythm and pitch to the performance. All of the choristers are male, ardently singing to attract mates. Couch's spadefoots bleat like lambs. Red-spotted toads trill. The Sonoran Desert toad adds a loud intermittent "Squawk!" and Great Plain's toads will chime in with a persistent jackhammer backbeat. If Woodhouse's toads are about, they'll croon a loud "Waaaaaah!"

Of these, Couch's spadefoots are the most common in the suburbs of Phoenix during monsoon season. Spadefoots, named for the tiny digging tools on the bottoms of their hind feet, are cued to emerge not by moisture, but by staccato drumbeats of hard rain and vibrations of thunder. The opportunity to mate is the primary motivation for toads to wake up from nearly a year of dormancy buried in the earth up to three feet below the surface. Eating comes second. 

At this end of the Valley, Skunk Creek, New River, and Cave Creek are excellent venues for toad concerts. "Creek" and "river" are deceptive names for these usually dry washes that may only flow for a few days a year. But an inch of rain anywhere upstream in the watershed can transform a wash to a raging torrent in a matter of hours. When the floods settle down, the pools left behind become toad nurseries. 

Spadefoots are famous for being one of the most rapidly developing amphibians in the world. One lady Couch's spadefoot can produce over 3,000 eggs that will hatch within a day of being fertilized. Then the race is on for tadpoles to develop into toadlets before the pond evaporates. If they don't get eaten, they can hop out of the pond within eight days. After surviving that challenge, a toadlet must then navigate the world of terrestrial predators, which includes lizards, snakes, raccoons, birds, other toads, and even spiders. Of thousands of eggs, perhaps one percent will live the two years it takes to become a breeding adult. These lucky survivors may live up to ten or more years in the wild. 

Many amphibian species around the world are suffering severe population losses due to a suite of factors, including habitat destruction, fungi and water pollution. "Toads that are adapted to temporary ponds in the Sonoran desert seem oblivious to these threats," notes herpetologist Brian Sullivan, a professor at ASU. He's been studying populations along Skunk Creek and Cave Creek for over three decades and sees no sign of decline. "There is, however, plenty of variation between years, as is expected in a climate like ours," he explains. "Successful breeding happens about one in five years, which is about how often the monsoon pools will last long enough for tadpoles to develop into toadlets."

Even with the abuses of road construction, flood control dams and off-road vehicle recreation, some of the washes in suburban areas remain excellent habitat for toads.  "There is always something fascinating going on in suburban desert washes," Say Randy Babb, herpetologist at the Arizona Game and Fish Department. For Babb, toad season is a favorite time of year. "I highly recommend that folks turn of the TV, abandon your computer, and get out to witness one of nature's coolest miracles," exclaims Babb.

Tickets are free!

If you’d like to identify toad songs you hear at your next toad concert, log onto the Reptiles and Amphibians of Arizona website to hear recordings:
Arizona Game & Fish Department also has some excellent videos of local toads at their website:

Warning: Handling any toad may cause an allergic or toxic reaction in most people as well as dogs who try to eat them. Neurotoxins are secreted from a toad’s parotoid glands, a pair of lumps behind their eyes. However, you do not have to worry about getting warts from handling toads. 

Friday, June 21, 2013

Bean Trees

For one-stop shopping in the Sonoran Desert, a mesquite tree is your best bet to find everything you might need, whether it be food, fuel, building supplies, medicine, rope, and yes, even diapers. These trees were so valued by traditional cultures in the southwest deserts that families claimed certain mesquite groves, or bosques, as well as especially productive individual trees, as their territory. One mature tree may produce between 40 to 100 pounds of bean pods in a good season, the basis of a healthy diet for many tribes. The pods were stored through the winter and ground into flour when needed to make cakes, porridge and sweet drinks throughout the year. For thousands of years, desert people have gathered mesquite wood for building shelters and making fires, sap for dyes, roots for fiber and leaves for medicinal tea. The diapers were made by pounding sheets of the fibrous bark into a soft cloth that would absorb any “leaks.”

The human relationship with mesquite is not quite so benevolent everywhere it grows, however. Many ranchers consider it to be a pest, since it will thrive wherever cattle roam, replacing valuable grasslands. The irony is that cattle feast on mesquite pods, and then deposit the beans in cow pies, a perfect environment for the seeds to germinate and grow.  Thus, more cattle on the range is better for mesquites. Paleontologists have deduced that cattle may be replacing the role of other large mammals that once roamed the southwest, such as camels, giant sloths and mastodons. After the Pleistocene extinctions about 10,000 years ago, mesquite bosques contracted to waterways and washes, where year round moisture and seasonal flooding ensured their success. But without passage through the guts of large mammals that travel long distances between waterways, the seeds were no longer distributed onto uplands.
Even though a healthy bosque provides shade and fodder for cattle, an aggressive campaign to eradicate mesquite in favor of grasslands ensued through the 1900’s. Combined with habitat destruction for agricultural, industrial and urban development, plus harvesting of trees for firewood and lumber, wild mesquite bosques are now considered somewhat rare.
Fortunately, the versatile bean tree has become a popular landscaping species over the past few decades, and is now grown and planted widely through the arboriculture trade. Velvet mesquite (Prosopis juliflora) is the most common in the Phoenix area, shading many parking lots and suburban tracts with their graceful, contorted stems. The return of mesquite to urban areas is also a boon to wildlife. Rabbits, coyotes, quails, javelina and deer also feed on the bean pods. Dozens of bird species nest and forage for insects in mesquite limbs. Mesquite leaf letter enriches soils with nitrogen, which, combined with shade, makes them excellent “nurse trees” for many kinds of plants. Plus, over sixty species of insects have been documented as visitors to mesquite flowers, gathering the abundant pollen and nectar to propagate their own offspring. In the spring, when long tassels of flowers dangle from the branches, a bean tree literally hums with life.  
According to the locavore food movement, which promotes the use of regionally adapted and native foods, mesquite could be the key to a more abundant and nutritive future for desert dwellers. If you are lucky to have a mesquite in your yard, you can rake up the pods to use as an alternative to mesquite wood for grilling and grind them into flour to use in baking. Here's how:

Prepare bean pods: Collect and rinse pods with clean water and dry in the sun. You can accelerate drying by putting them in the oven at the lowest temperature (~150F) for 2-4 hours. The more crispy the pods, the easier it is to grind them into flour.

Make the flour: If you want to be very traditional, get out the mano and metate or a mortar and pestel! However, you can also grind the bean pods in a blender. Just  put about 15 pods in at a time for about 30 seconds. Sift with a fine sieve and store the flour in the freezer until ready to use. Make sure you are sifting out the hard, bitter seeds.

Bake: The traditional cake or cookie was a simple mixture of flour and water, made into round flat patties and dried in the sun. To use mesquite in baking, just replace ¼ of the amount of flour called for in your recipe with finely ground mesquite meal.

Steep Tea: A sweet tea can be made by soaking some of the flour in water and then straining off the pulp….perfect to serve with cookies!

To learn more about the history and ethnobotany of mesquite, look for these books:

Gathering the Desert by Gary Paul Nabhan

Medicinal Plants of the American Southwest by Charles W. Kane

And check out this website: Desert Harvesters ( in Tucson hosts mesquite pod milling events every year, as well as being a resource for numerous workshops and publications on native plant foods.

Monday, April 15, 2013


If you were to choose sounds that best represent the “Wild West,” the howl of a coyote would certainly be in the top 10, if not number one on the list. Whether it’s the song of a lone coyote or the frenzied yipping of a small pack, their voice elicits strong emotions from anyone who hears them. Indeed, coyotes are some of the most admired, hated, respected, feared, romanticized and misunderstood wild animals in North America.
            Unlike wolves, their larger canine cousins, coyotes have a remarkable ability to adapt to human activity. Equally at home in urban areas, agricultural regions and remote wilderness, coyotes are similar to people in many ways. Both clever opportunists and formidable predators, they are omnivorous and will eat almost anything that is made available to them. Like indigenous people of the Sonoran desert, their favorite foods include mesquite beans, cactus fruit, cottontails and quails. Unfortunately, some coyotes in rural areas have, like humans, developed a taste for lamb, beef and venison as well, and are thus perceived as serious competitors for food.
            Although there are no official population estimates, urban wildlife specialist Darren Julian of the Arizona Game and Fish Department (AZGFD) says that there are more coyotes per square mile in suburban areas of Phoenix than in the surrounding desert regions. “They are especially common near golf courses and lake communities, or in neighborhoods where there are greenbelts. These areas support a lot more prey animals, such as cottontails, doves, and small rodents,” says Julian. “There is no true drought experience in the suburbs, so there is plentiful food year round for all kinds of urban predators, which includes owls, bobcats and foxes, as well as coyotes.”
            The abundance of prey near irrigated lands, whether agricultural or suburban, makes these ideal places for coyotes to raise families. April and May is prime time for coyote pups, so both parents are hunting for three or four, rather than just themselves.  At about six months of age, pups will be out hunting on their own.
Photo by Ruth Anne Kocour
Coyotes are usually seen trotting through the neighborhood alone, but occasionally travel in family groups of up to five or six, especially in the fall when pups are still being schooled in the art of hunting. Fall and winter, from September through January, is also when they are most vocal, since there are more rowdy “teenager” coyotes, and individuals are often calling to keep track of each other.  Things are a little quieter when they are denning with young pups in spring and early summer.
            Many people fear coyotes, but the coyote has much more to fear in humans. AZGFD records show that between 30,000 and 40,000 coyotes are killed by hunters each year in Arizona alone, primarily for recreational purposes.  This is a sharp contrast with the reverse statistics, with only 2 fatal and fewer than 200 documented non-fatal attacks by coyotes towards humans in the entire United States and Canada over the past 30 years. Although coyotes do occasionally prey on small pets and livestock, those numbers are in the low hundreds each year for Arizona.
            The best way to avoid unwanted interactions with any wild animal is to not provide them with food. This means that pet food and small pets should not be left unattended outdoors, and birdseed or other food sources that attract prey species should not be made available near your home.
            Otherwise, consider yourself lucky if you see a coyote on the trail or in the neighborhood. They are part of a healthy ecosystem, helping to keep rodent populations in check and providing the bonus of a little night music.  If you can’t hear them at night out your window, you can listen to them howling on-line here: Wild Coyote Sounds 

Learn more about urban coyotes at these websites:

Friday, February 8, 2013

Forecasting Spring Wildflowers

When it comes to spring wildflowers in the Sonoran desert, timing is everything.  There is a common misconception that if we get plenty of rain in the spring, wildflowers will abound. But truly eye-popping displays of desert annuals require a steady dose of winter rains beginning in November and lasting through February in order to germinate and grow a healthy crop of seedlings that will eventually flower. Lots of other factors come into play, but the records show that a cumulative rainfall of over four inches through the winter, preferably not in one giant storm, is the most reliable predictor for the abundance of spring wildflowers. This was the case for our most recent banner years, 2001 (7.07”), 2005 (7.72”) and 2008 (4.35”), when entire hillsides glowed orange with poppies, blue with lupines and valleys blazed hot pink with purple owl clover.
A decent monsoon the previous summer will help, but is less important than a consistent series of winter rains that keep the soil moist. In fact, the same banner years listed above actually had below average  (< 2”) monsoon rains the previous summer. Cooler temperatures also help keep the evaporation levels low and tender seedlings from frying in the hot sun. Even if you want wildflowers in your yard, you need to scatter the seed no later than early November and then water them weekly for the next three months if you want to see some action.  
So what’s the forecast for this year’s desert wildflowers? I'd say mild to moderately stunning. Records from the National Oceanic and Atmospheric Administration (NOAA) show that while the 2012 monsoon season was slightly above the 100+ year average of 2.71 inches, we’ve had a relatively dry winter. The gentle rains in early December and late January only generated a cumulative rainfall of about 2.30 inches for the Phoenix region.  More rain in February and March can help, but it’s usually too little, too late. However, we should always be grateful for any amount of rain in the desert!
            The good news is that there are always wildflowers somewhere; you just have to know where to look and plug into the wildflower watch networks to learn where the weekly hot spots are.  Because rainfall varies a lot across the region, certain hills may be lusher than others, even compared to somewhere only a few miles away. Even a scant quarter inch of rain can make a big difference. In a dry year, north-facing hillsides are good places to scope out, since moisture will hang around a little longer on the shady sides of the hills. Even the north sides of large boulders and the shade of large trees will often be havens for annual wildflowers.
            Although annuals may be sparse this year, many shrubs, perennials and cacti will bloom profusely, since they don’t have to start from seed. This is a great year for desert hyacinth (Dichelostemma capitatum), a delicate perennial plant that harbors a bulb deep below the soil surface. Thousands of slender succulent stems pierced the stony soils in desert hills throughout the region by early February, and will show off lavender blooms by early March. Bright orange globe mallows are another abundant hearty perennial commonly seen along roadsides throughout the desert.  Flowering shrubs like brittlebush, wolfberry and ratany will always find energy to bloom, even if there is next to no rainfall. 
            In the Happy Valley region, you’re likely to find some brilliant patches of wildflowers in the Sonoran Preserve, east of Highway 17, just north of Jomax. Cave Creek Recreation Area north of Carefree Highway at 32nd Street and the Pipeline Trail at Lake Pleasant are also historically floriferous.  Wherever you go, be sure to appreciate the miracle of each and every blossom.