Monday, June 29, 2015

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.

Sunday, May 3, 2015


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.

Saturday, February 7, 2015

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:

Tuesday, December 2, 2014

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.

Saturday, October 11, 2014

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.

Thursday, August 14, 2014

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!

Thursday, August 7, 2014

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?