In his search for things to do around Tucson, John learned of the Saguaro National Park. In case you didn’t know (and I assume many of you don’t, because I didn’t), saguaro is the giant cactus that is symbolic of Arizona, usually depicted with two opposite and only slightly asymmetric arms. Saguaro is pronounced Sa-WAH-ro; it is an Americanized pronunciation of the Spanishified word for cactus of the native population, the Tohono O’odham. With so many transformations through different languages, the pronunciation has some room for interpretation (at least that’s what I tell myself; I am happy if I can remember how to spell the word, forget about pronouncing it well!)
The park has two districts, one west of Tucson and one east of Tucson. After spending a day doing errands in Tucson, we headed over to Saguaro West, Tucson Mountain District. We planned on backpacking in the the east side Rincon Mountain District after exploring the west, though we ended up backpacking in different mountains instead.
Our first stop in the park was the Visitor Center, and they had so many excellent programs that we stayed there most of the first and second days we visited the park, attending three programs each day! This park has the busiest schedule of lectures and guided walks of any of the parks we have been to thus far. My theory is that this is because they are so close to Tucson that they have a large pool of volunteer labor to lead programs and to work the front desk to free up rangers to lead programs.
The first day we joined a walk with a volunteer naturalist who described the Saguaro lifecycle and introduced us to other plants of the Sonoran Desert. Most of the plants are similar to those that we’ve been seeing for the past month traveling in the Chihuahuan Desert, but much larger. The Sonoran Desert is pretty wet as far as deserts go, receiving about 10 inches annual rainfall over two rainy seasons. In addition to the summer monsoon season that the Chihuahuan Desert has, the Sonoran also has a winter rainy season (or at least it used to; the southwest has been experiencing draught conditions for a majority of the last 14 years, especially in the last three, and climate change scientists expect the southwest to continue to experience drier weather going forward.) The additional annual rainy season leads to bigger cacti, larger creosote bushes, and more vegetation in general. Desert plants are an exception to the “Everything is bigger in Texas” rule! 🙂
Saguaros are large and can live long lives, but their start is small and precarious. Saguaro seeds are smaller than a pinhead, and each mature cactus produces tens of thousands annually, as many as 40 million in its lifetime. Conditions for a seed to germinate, grow, and survive into a large cactus must be absolutely perfect. Only one or maybe two of those 40 million seeds will grow into a mature cactus. Germinating under an established plant helps a new saguaro; the nursery plant shades the baby cactus from harsh sun, protects it from freezes and hides it from hungry creatures. It is a slow growing baby, and after 10 years a saguaro may only be the size of a human thumb! The growth rate increases after this stage and they continue growing throughout their life, up to 200 years old. The oldest Saguaros can stand over 50 feet tall and weigh upwards of 16,000 pounds! All from a little tiny seed eaten by a bird and “deposited” under a bush.
Once the saguaros reach about 8 feet tall (at least 30 years old), they start producing flowers and seeds. While this is obviously the reproduction of the plants, I couldn’t help myself from thinking of the arms as ’children’. There is a long history of humanizing the cactus forms…in the film shown in the visitors center we learned that the O’odham people considered them to be honored relatives, with a mythology that the cacti originated as a young girl who sank into the earth. In silhouette, the forms appear as a crowd of people. While the typical caricature of the cactus is the familiar two-armed version (most human-like in form), in actuality the cacti can have no arms or many arms. This is what made me think of children…some cacti are 20+ feet tall, standing proud with no arms, while others are ringed with six or more, a large family indeed. Some sprout arms as early at 30 years old, but the average age to grow the first arm is 70. A couple times we even saw cacti whose arms had arms, like grandchildren.
Saguaros are not trees, but they do have a woody internal skeleton to provide structure and support. The interior of the plant is filled out with a spongy flesh that stores water. The pleated shape of the exterior allows the cactus to expand and contract as the water supply waxes and wanes. If a saguaro needs additional water storage capacity, it grows an additional pleat. To mitigate the effect of the harsh desert sunlight, saguaros grow a thick clump of thorns at the top, which shade the tip as leaves normally provide shade (cactus thorns are modified leaves for these desert-adapted plants). The gila woodpecker drill nests into the saguaro, which protects itself from dehydration by forming a sort of scab on the wound and creating a hard shell called a ‘saguaro boot’. The gila woodpecker makes a new nest each year, leaving the old nest for other birds to take over.
Saguaros are protected in Arizona and it is illegal to remove them without proper permits. When the cacti are in the way of development, builders can apply for a permit to move them. Unless the plant is small, this is destined to fail because their root structure is as big in radius as they are tall. Saguaro are valuable and cactus swindling is rampant. Criminals will rip out a large saguaro and sell it to a home owner for thousands, even tens of thousands of dollars. The stolen cactus will stand green for a few years from the stored water within, though it was killed from damaged roots at the moment of removal. Saguaro poaching is such a problem at the park that the cacti near the road have been microchipped with the same technology that is implanted in pets and the local nurseries have scanners to avoid purchasing stolen plants.
Moving on in the plant tour away from the saguaros, we came to an ocotillo bush with LEAVES! Ever since we arrived at Big Bend and I learned about this interesting plant that sprouts leaves after every rain and drops them shortly after, I had wondered what it looked like with leaves, but did not think I would see one so soon. The ocotillos here had leaves from a rain in early December, and were getting ready to drop them again. Some of the plants had leaves turning red in preparation to fall, but others had not only green leaves, but also lovely red flowers! I was very excited to see this, and interested to later discover that the word ocotillo is derived from a Spanish word for torch, which makes sense after seeing the bright red flowers at the end of each stalk!
In addition to seeing the leaves on an ocotillo, I learned that I was pronouncing the name wrong. It is oak-a-tio, not awk-a-tio. Also I was pronouncing cholla way wrong, forgetting even that the double-l makes a y-sound, not an l-sound. Cholla rhymes with the name of my good friend Zoya, so now I can speak of this prickly plant in a way that others understand! The cholla around Tucson have a reputation as being “jumping cholla”. The common misunderstanding is that the segments actually jump from plant passerby because if a person or animal just barely brushes against the end of the spines, the segment will fall off the plant and stick to clothes, fur or skin to come along for a ride. Once brushed off back onto the ground, the segment can root and grow a new plant. This reproductive strategy compensates to the undesirability of the fruit, which sits uneaten on the cactus, left alone by birds and rodents which help spread the seed of so many other plants.
Every program leader we spoke to over the two days who talked about plants at all mentioned the role of barrel cacti in John Wayne movies. I am no western aficionado, but apparently it was common in these movies for the hero to be saved from dehydration by cutting into a barrel cactus with a machete and to drink the water within. This is emphatically both impossible and dangerous. Impossible because the cactus has a strong woody center and would not be easily hacked open with a machete, and the contents are a spongy flesh, not a pool of stored water. Dangerous because the water contains a toxic concentration of oxalic acid, which would cause at best an extended bout of diarrhea, and possibly even kidney failure. So don’t learn wilderness survival from movies (or “reality” television for that matter…John lately has been watching “Man Vs. Wild”, and has been regaling me with the dangerously ridiculous antics of the star “survivalist”). On the other hand, the cactus is sometimes called the “compass cactus” for good reason, and if really lost you can use these to navigate. Intense sun stunts the growth on the southwestern side, so they tend to lean southwest (if you need to use this navigation method, make sure that several point in the same direction). The leaning effect is so pronounced that a major cause of mortality for these cacti is that they lean into the sun until they uproot themselves! The barrel cactus fruit are a last-resort meal for the local creatures and can sit undisturbed for a year, until the rodents get so desperate that they finally have to resort to eating them.
The last plant program we attended was a tour of the Sonoran “neighborhood”, where the ranger makes analogies of each plant with a character in a standard neighborhood. For instance, the creosote is the pharmacy, having many traditional medicinal uses, and the prickly pear is the grocery, providing food for many creatures, from rodents to javelinas and even humans. Jojoba she called the “Bill Gates” bush, it isn’t showy, but its uses are transformative. Jojoba oil is the only plant oil that can replace whale oil for uses in precision machinery, a discovery that reduced the demand for whale oil. It’s leaves provide a compound used in autoimmune drugs including to treat HIV, and of course the oil is popular in beauty products such as shampoo and moisturizers. With such valuable uses, many ranchers are switching to jojoba cultivation, probably a more appropriate use of the desert land than trying to grow more water-dependent plants and animals.
In addition to learning all the above about the local flora, we also attended programs on the fauna. We learned about the poisonous creatures around, rattle snakes and gila monsters. Gila monsters are the only venomous lizard in the US. They are slow moving and thus not a large threat to humans, but if they latch on they don’t let go. Even if killed, their jaws are difficult to open.
A retired academic mammalogist and snowbird leads a weekly tour “Thirsty Mammals”, showing evidence of mammals and explaining their survival strategies. The group on this tour was the biggest he’d had in several years of offering this program at around 30 attendees, and we were also the luckiest. At the beginning he warned us that we would not actually see any mammals, he never had on one of these tours, but we saw a group of several deer and a squirrel! He showed us many varieties of scat, which persist well in the dry desert, a pack rat midden entrance, and pocket mouse burrows. While we like to think that pocket mouse is so-named because they are so cute you want to put it in your pocket, the name actually refers to food-storage pockets in their cheeks, similar to chipmunks. These creatures are numerous, and the guide estimated that millions live within the park.
The final program we attended was an informative lecture about mountain lions. We learned that females are not super territorial, and when a young female leaves her mother she will establish a territory nearby, possibly even overlapping with her mother’s. Males, however, are ultra-territorial. When they set out to establish their own territory, they have to travel far to find a territory not already claimed by another male. If they linger too long in a male’s territory, a fight to the death ensues. Territory fights are the number one killer of mountain lions in the wild, and the young one is most likely to loose due to lack of experience. A male’s territory will overlap with the territory of 2-4 females; by claiming the territory the male not only claims the prey within, but also the mates. He will not stop his search for territory if he does not find females. All mountain lions east of the Rockies were exterminated by the mid-20th century; recent sightings have been determined to be males that wander east looking for territory and do not stop because they do not find females. Many males are also killed in search of territory as they are trapped by hostile ranchers or hit by cars. Mountain lions are not a huge threat to humans; more people drown in their bathtubs than are killed by mountain lions. An out of control deer population, a direct result of exterminating top predators in the ecosystem, are a much bigger threat to people, as over 100 people per year die from vehicle-deer crashes, compared to less than one per year mountain lion fatality.
Now that we have a good base knowledge of the ecosystem, it is time for us to hunt for the quintessential two-armed cactus. More on the search coming soon.