Thursday, October 23, 2008

Desert bighorn sheep

Around Tucson in Arizona, desert bighorn sheep (Ovis canadensis) can be seen in the rugged Santa Catalina Mountains or, easier accessible, at the Arizona-Sonora Desert Museum, where the above picture was taken (also see terragalleria). As a panel explains, desert bighorn live in rough and rocky, low desert mountains. The precipitous mountain ridges provide refuge from coyotes and pumas. Rocky drainages contain rare water catchments in this arid environment. The gradual lower slopes and dry washes furnish the sheep with a sparse forage of jojoba, palo verde and mesquite.

More on desert bighorn sheep at Wikipedia, in Wildlife Water Water Developments and Desert Bighorn Sheep in the Southwesetern United States, and in The Southwestern Naturalist: Barrel Cacti Consumption by Desert Bighorn Sheep by Greg D. Warrick and Paul R. Krausman, 34(4):483-486, December 1989.

Pusch Ridge Wilderness

The Pusch Ridge Wilderness north of Tuscon in Arizona was established in 1978. Various trails such as the Pima Canyon Trail offer access to this rugged and steep area of the western Santa Catalina Mountains. One of the last remaining populations of desert bighorn sheep (Ovis canadensis) occurs in this area, but the numbers are dwindling. The Wilderness, as a trailhead panel explains, also hosts a diversity of vegetation communities from Sonoran desert at 3,000 feet elevation to semi-desert grasslands, oak woodlands, chaparral, ponderosa pine forests, and mixed-conifer forests at 9,000 feet. Precipitation varies from less than 12 inches at the base of the mountain to nearly 30 inches at the summit. Nearly half of the precipitation falls during the summer monsoon season. In winter, snow is common at higher elevations.

Tuesday, October 21, 2008

Touch the rattlesnake's rattle

Touch the rattlesnake's rattle—not the rattle of a snake you encounter on your hiking trail, but the enlarged model shown here as it is displayed in the Arizona-Sonora Desert Museum. The cross-section clearly demonstrates the segments of the rattle. Rattlesnakes add a new segment every time they shed their skin. As a panel next to the model explains, the rattle [of a real rattlesnake] is hollow, dry and feels something like heavy parchment. It is made of keratin, a fibrous protein that, in other animals, makes feathers, hair, horns, and nails. Segments loosely interlock; when vibrated their clashing creates the sound. The vibration increases with air temperature. At any temperature, you should be alarmed if you hear the rattling from somewhere next to your trail.

Monday, October 20, 2008

Arizona-Sonora Desert Museum

The Arizona-Sonora Desert Museum is a nature park, located west of Tuscon. The park includes various short trails, gardens, exhibits and sculptures such as this coyote sculpture. While you tour the loop trails, you may want to side-step into the earth science limestone cave with mineral displays, the underwater beaver and otter viewing tunnel in the riparian corridor, or the walk-in aviary. To study succulents and other plants, visit the cactus garden, the agave garden, the pollination gardens, and the desert grassland area. The park offers a rare opportunity to explore underground life of snakes, prairie dogs, owls, scorpions and tarantulas, safely tucked behind glass. Other wildlife in the park includes white-tailed deer, bighorn sheep, a mountain lion, Mexican wolves and real coyotes not far from where the coyote sculpture is.

Sunday, October 19, 2008

Zebra agave

The zebra agave (Agave zebra) is a highly sun-tolerant plant. In full sunshine, the name-giving cross-banding of the green-silvery agave is easily recognized. Zebra agaves make nice potted or landscape specimens. The shown specimen is found in the Arizona-Sonora Desert Museum, which features an agave garden, just off the main loop trail between the cactus garden and the desert grassland, and a digital library that includes zebra agaves.

Does a saguaro have a brain?

This one at the Arizona-Sonora Desert Museum looks like it does. The prickly brain, however, is just a result of distorted growth. This “monstrose growth” is caused by damage to the meristem, the plant tissue of undifferentiated cells where division into differentiated plant cells occurs. A panel in the Desert Museum explains this odd Carnegiea gigantea shape as follows:
This unusual young saguaro is just beginning to form a crest, which may eventually grow to more than six feet wide. A crest can develop when the growing point or meristem (which produces new stems and spines or leaves), elongates into a line. In time the growing line may become greatly convoluted, like a brain. This phenomenon has been observed in nearly all plant species; its cause is generally not known.
For example, a giant cardon cactus (Pachycereus pringlei) has been found with monstrose growth.

Small, tall and branched saguaros

Even giants start small. A small saguaro cactus starts with healthy growth while surrounded by nursing shrubs that protect the saguaro from browsing animals. Growing tall, up to about 40 feet, a giant saguaro may reach an age of 200 years. Nobody will mistake it for a barrel cactus anymore. It takes about a quarter of a saguaro's life-span to get productive and also to develop ascending branches, as seen in the image taken in Pima Canyon near Tucson, Arizona.

Saturday, October 18, 2008


Carnegiea is a monotypic genus containing as its single species Carnegiea gigantea, commonly known as giant saguaro or saguaro cactus, which was originally named Cereus giganteus by botanist George Engelmann in the mid-19th century. Saguaros are found in the southwestern part of the United States (predominantly in Arizona and a limited number in California's Whipple Mountains) and in northwestern Mexico. If you don't live near a desert trail that takes you into cactopia, you may want to approach the prickly columns by saguaro surfing. (Ouch!)
Here are some links: Infos and references for your study tour and for your visual tour, I suggest the saguaro site of the School of Biological Sciences at the University of Edinburgh (no, the pictures were not taken in Scotland) and the George & Audrey Lange page.

Friday, October 17, 2008

Giant saguaros in Pima Canyon near Tuscon

Who hasn't seen saguaro cacti in a Hollywood Western? If you think you have, you probably haven't seen real ones. Like so many things in Hollywood movies, the saguaros typically are fake. An easily accessible place to get close to living saguaros of all shapes and sizes is the Pima Canyon Trail. The trailhead is located in the northern part of Tuscon, Arizona, at the eastern end of Magee Road. The trail leads deep into the Pusch Ridge Wilderness, but it takes only modest climbing and less than a mile to pass various saguaros and other cacti.

Tuesday, October 14, 2008

Between the saguaros with Maynard Dixon

Saguaros are fascinating plants and so are the landscapes in which these and other cacti dominate. Saguaros throw their shadows during sunrise or sunset. Seen from a different perspective, they appear dwarfed within the endless desert and towering rocks of the Southwest. Nobody has captured those impressions as colorful as the American artist Lafayette Maynard Dixon (1875-1946). Over 100 of his works are displayed in Arizona at the Tuscon Museum of Art. The exhibition with the title A Place of Refuge: Maynard Dixon's Arizona runs from Oct. 11 to Feb. 15, 2009.
Dixon's drawings and paintings document nature as well as people and their ways of live in the arid Southwest. The desert landscapes were an artistic and personal refuge for Dixon and today's visitors will feel and appreciate the landscape therapy. Dixon's art connects us with the past. Not just the recent past. The landscapes invoke the past on a geological scale. And they inspire us to enter and explore their dimensions—with or without an easel.

Walking unsuspiciously with a poodle

If your hike or leisurely stroll goes through a neighborhood that you don't know, are you afraid to pass through or do you bother whether the neighborhood could be afraid of you? I hope not.
Nature always welcomes us, neighborhoods occasionally don't; at least not until we adjust our “locomotional behavior” by, for example, coming along with a poodle. Lucius Beebe tells us an illustrating story from a time when security cameras were still unknown, but neighborhood watch was installed nevertheless:

As is true in Beverly Hills, a closely parallel enclave of privilege, there are no sidewalks in Hillsborough [in San Mateo county south of San Francisco]. A car, preferably Rolls-Royce or Bentley, is the only thinkable means of locomotion and pedestrians, unless walking dogs, are automatically suspect, and usually questioned by the police. Lord Kinross, the literary peer of Punch, was only a few years ago a house guest who, in all innocence, undertook a brisk after-dinner constitutional on Hayne Road. Before he had gone a block, he was apprehended and questioned by the occupants of a squad car. Thereafter, when inclined to exercise, he borrowed a standard poodle from his host and was immune to suspicion.

Lucius Beebe: The Big Spenders, Pocket Books, a division of Simon & Schuster, Inc., 630 Fifth Avenue, New York, N.Y. 10020, 1967; page 73.