Sunday, May 15, 2016

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.

Friday, February 26, 2016

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).

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.

Saturday, January 2, 2016

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