Saguaro National Park

Saguaro National Park

The Saguaro National Park, whose WDPA code is: 374162 is a United States National Park located in Arizona, with a land area of ​​370 km².
This park was established in 1994 and is managed by the National Park Service.
Saguaro National Park is located in southern Arizona and is divided into two sections, one about 20 miles east and the other about 15 miles west of Tucson. Both sections are easily accessible by car and have a visitor reception center.
Saguaro National Park is part of the Sonoran Desert and is named after saguaro, a giant cactus native to this region, although other cactus species are also present.
The area was originally designated as a National Monument on March 1, 1933, and was transformed into a National Park on October 14, 1994 by President Bill Clinton.

Geography –
The Saguaro National Park, as mentioned, is divided into two sections.
The West Section: Tucson Mountains District and the East Section: Rincon Mountains District.
The Tucson Mountains District is located west of the city of Tucson. The Red Hills visitor center (2700 North Kinney Road, Tucson, Arizona 85743) is open from 9am to 5pm every day except December 25th, here you can find brochures, books and maps of the park. Following the road that enters the park from the visitor center for about 2.5 km, you reach the Bayada loop drive, a steep dirt road that makes a loop of almost 10 km through a dense saguaro forest. In this section of the park there are some very simple and short-lasting paths, such as the cactus garden trail at the visitor center, the desert discovery nature trail just under 1 km long, the valley view overlook trail of about 1.5 km which allows panoramic views of the desert, mountains and saguaro forest.
The Rincon Mountains District is located east of the city of Tucson and was the original National Monument. The peculiarity of this park is that it starts from the Sonoran Desert and gradually becomes part of the coniferous forest of the Rincon Mountains. The highest peak in this area is Mica Mountain which reaches an altitude of 2641m. Although this section has fewer saguaro cacti than the western area, they are on average larger in size due to the more frequent and abundant rainfall due to the proximity of Rincon mountain.

Geology –
The Saguaro National Park has a very ancient geological origin. The oldest rocks are metamorphic in nature, dark gray in color known as Pinal schist, representing the original crust of southern Arizona. These rocks were formed about 1.7 billion years ago during the Precambrian due to the collision between plates that altered the pre-existing sedimentary volcanic rocks into schists and other metamorphic rocks. There are also some grants formed 1.4 billion years ago and which make up the crest of the Tarque Verde.
Subsequently, about 600 million years ago, at the beginning of the Paleozoic, crustal movements related to the collision between the Pacific plate and the North American plate began, this led to a succession of periods of deposition of sedimentary rocks, mainly limestone, sandstone and shale and erosion periods. Specimens of these rocks can be seen inside the park, in the Sus picnic area and near the Lime Kiln waterfalls.
During the first part of the Mesozoic, about 150 million years ago, the continuous rise of the region led to a strong erosion of the rocks that gradually reached the surface. The sediments were dragged up to an inland sea and today form the Red Hills near the homonymous visitor center. The red color is due to hematite, an iron oxide that forms in shallow oxygen-rich waters such as the sea that covered this region. Evidence of the existence of this sea comes from petrified fossil wood, shells and dinosaur bones found in the area.
Between the end of the Mesozoic and the beginning of the Cenozoic, about 30 million years ago, the continuous subduction of the Pacific plate under the North American plate led to a strong volcanic activity involving the present Tucson area, as a consequence of this. there were strong emissions of rhyolite, lava and pyroclastic flows. The consequent emptying of the subsoil led to the formation of a huge caldera which gradually filled up with rhyolite, ashes and rocks formed during the collapse of the volcano. This rock complex is known as Tucson Mountain Chaos and is the main rock formation in the Tucson Mountains. In the same period the surrounding areas were subjected to introsions of pink granite and quartz veins that contain many minerals, including copper, silver and gold, the presence of these minerals allowed the development of Arizona in the late nineteenth century. One of these intrusions is visible along the Hugh Norris trail, at the height of Amole Peak.
Finally between 10 and 20 million years ago the continuous movement of the tectonic plates led to the formation of a fault in the Tucson area, the movements along this fault led to the formation of a depression that was filled with sediments from the Tucson Mountains and the Catalina mountains, this process is continuing to this day.

Climate –
The Saguaro National Park is located in a region characterized by an arid climate of type BWh according to the Köppen-Geiger classification.
In this area, in the winter period, the temperature can go from around 19 ° C during peak hours to 5 ° C at night, summer is extremely hot with maximum temperatures that can exceed 41 ° C while in the evening the temperature drops to about 22 ° C.
The area is characterized by a very arid climate with average annual rainfall of just over 300 mm, the most abundant rainfall occurs in the months of July and August, while it is extremely scarce between April and June. In winter, rainfall is concentrated in the months from December to February and occurs in the form of light but prolonged rains, snowfalls are also possible at higher altitudes, the summer rainy season is instead from July to September and is characterized by intense rainfall. and violent typical of the North American monsoon, accompanied by lightning and sudden floods followed.

Flora –
The Saguaro National Park, due to its climatic peculiarities, hosts, for the most part, plants that have adapted to living in the desert, so in the driest periods they reduce their activity to preserve the accumulated water. There are over 1162 plant species in the Rincon Mountains district, ranging from cacti and ocotillo in the desert area to yellow pine (Pinus ponderosa) and pseudotsuga in the mountainous area. The Tucson Muntains district contains 512 species of plants.
Within the park there are 10 species of plants in danger of extinction, 78 species of plants not native to the region have spread within the Rincon Mountains district, while 47 species of plants not native to the area have spread to the interior of the Tucson Mountains district. There are 25 species of cacti in the park, including the saguaro (Carnegiea gigantea), various species belonging to the genus Mammillaria, Ferocactus wislizeni, Opuntia versicolor, Echinocereus fendleri var. fasciculatus, the Opuntia engelmannii, the teddy bear cholla (Cylindropuntia bigelovii), the Cylindropuntia fulgida.
Also within the park there are many species not native to the region, the most dangerous for the life of the saguari is the Pennisetum ciliare, a perennial plant native to Africa able to compete for the same resources that the saguaros eat and which creates a turf that does not allow the growth of other species and which facilitates the spread of fires. Every 10 years there is a census of saguaros in the park, the last one was from October 2009 to October 2010, the results have not been completely analyzed even if it is evident that the number of specimens is constantly increasing in both districts. since 1990.

Fauna –
As with plants, the animals of the Saguaro National Park also include specimens that have adapted to living in arid and hot climates.
In fact, despite being a desert area, there are some amphibians in the park, especially toads that come out of underground burrows in summer when the monsoon rains fill the streams that cross the park with water and form pools. The list of amphibians present in the park includes: Hyla arenicolor, a small tree frog with very variable colors that allow it to blend in well with the environment in which it lives; it is possible to find it along the riverbeds between rock boulders to which it is able to cling thanks to the suckers present in the legs, the only defense from predators is given by mimicry and remaining totally still when the predator is near. The Scaphiopus couchii lives most of the year in underground burrows in a lethargic state, during the summer rains it comes out of the burrows to feed mainly on termites, if the rains are long enough, the search for a mating partner begins.
Another amphibian is the Bufo cognatus, easily recognizable by the symmetrical spots on the back, the call of the male is very noisy and can last up to a minute. The Rana yavapaiensis lives only in areas where there are permanent pools of water, it reproduces all year round and tadpoles take about a year to become adults, the fact that they live where water is present all year round endangers the presence of this species inside the park as long periods of drought dry up almost all the pools. Spea multiplicata is also active during the summer rainy period when it is in danger it emits a secretion with a strong peanut-like odor from the skin that causes tearing and nasal discharge. The small Bufo punctatus is easily recognizable by the large glands present behind the eyes and by the red bumps scattered on the back, it is the only species of toad present in the Sonoran desert that lays its eggs individually. Incilius alvarius is one of the largest toads in North America, the skin is an olive-green color and has large glands behind the eyes that emit defense toxins if in danger, these toxins are so powerful that they get paralyzed and in some cases to killing a dog.
Inside the Saguaro National Park there is obviously no shortage of reptiles, some of which are among the most characteristic of North America, such as the Gopherus agassizii, a turtle that is able to live up to 100 years and which is difficult to see in what remains hidden in the den during the hottest hours. The Gila monster (Heloderma suspectum) is one of the two venomous saurians existing in the world, the venom is secreted by the glands of the jaw and penetrates the victim through the bite, its venom is not however deadly for humans. The solar Phrynosoma is the largest horned lizard in the United States and is easily recognizable by the four horns behind its head, it is easy to see it near anthills as it feeds mainly on ants.
There are 5 species of rattlesnakes: Crotalus atrox, the most common in North America, Crotalus tigris, Crotalus molossus, Crotalus scutulatus and Crotalus cerastes. Another species of venomous snake present in the park is the Micruroides euryxanthus. There are also numerous species of non-venomous snakes including: Thamnophis cyrtopsis, Lampropeltis getula, Diadophis punctatus, Tantilla hobartsmithi, Trimorphodon biscutatus and Leptotyphlops humilis.
The birdlife is also interesting; Within the Saguaro National Park, there are species of birds that are difficult to see elsewhere, such as the vermilion flycatcher (Pyrocephalus rubinus) and the whiskered scops owl (Megascops trichopsis). In the desert area it is possible to see the greater mimì (Geococcyx californianus), perhaps one of the most famous birds of the southwestern United States; it is rare to see it fly as to hunt it exploits its fast run that allows it to capture lizards and rodents, the long tail acts as a rudder during the run. The Gila woodpecker (Melanerpes uropygialis) nests in the outer bark of the saguaro, in this way it is able to defend itself from both predators and the high temperatures of the desert. The abandoned nests are occupied by other birds, such as the kestrel (Falco tinnunculus), the purple swallow (Progne subis) and the elf owl (Micrathene whitneyi); the latter is the smallest owl in the world, it feeds on insects, especially beetles and moths, and migrates to Mexico towards the end of October to return to the Sonoran desert in March. The Gambel’s colander (Callipepla gambelii) is easily recognizable by a black tuft on the head, it does not like the heat so it is active in the morning and in the evening, during the periods of drought it obtains water from the fruits of the cacti.
Anna’s hummingbird (Calypte anna) is the only year-round hummingbird found in the Sonoran Desert region. The cactus wren (Campylorhynchus brunneicapillus) is the symbolic bird of the state of Arizona, the male and the female build the first nest together and while the female is hatching the eggs, the male builds a second nest that will be used first as a refuge for adults and therefore for the new brood. The curved beak mime (Toxostoma curvirostre) in addition to being recognizable by its curved beak, has very showy yellow eyes, uses its beak to dig in the sand to hunt for insects and seeds.
The common Harris buzzard (Parabuteo unicinctus) lives and hunts in groups, the groups are formed by a couple that reproduces and by some adults who only take care of feeding the young of the couple and defending the nest. The white dove (Zenaida asiatica) plays a fundamental role for the saguaro, in fact it favors pollination by moving from flower to flower and once the fruits of the cacti ripen it helps the spread of seeds as it feeds on the fruits but is not able to digest the seeds.
Going up to higher altitudes it is possible to meet the common goshawk (Accipiter gentilis), the yellow-eyed junco (Junco phaeonotus) and the Mexican jay (Aphelocona ultramarina). The male of the black fainopepla (Phainopepla nitens) is distinguished by its glossy black color, crest and red eyes, while the female is gray with red eyes. It feeds mainly on mistletoe and contributes to its diffusion by dispersing its seeds through the manure.
Despite the climatic characteristics of the park, there are numerous mammals in this area.
These include bobcat (Lynx rufus) which is widespread in the park; this mainly feeds on rabbits and quail, in some cases it goes as far as the borders of the city of Tucson. The puma (Puma concolor) is the strongest predator present in the park and is widespread in both sections, the jaws of this animal are so strong that they can break the turtles’ carapace to eat them. The American black bear (Ursus americanus) is present only at the highest altitudes in the Rincon Mountains district, it normally lives inside the forest but when in the driest years it also descends to lower altitudes in search of food and water. The common nasua (Nasua narica) is a diurnal animal able to feed on both insects and snakes, as well as seeds and berries. The raccoon (Procyon lotor) prefers areas where there is water all year round, it easily moves towards the city in search of food.
The North American bass (Bassariscus astutus) is the mammal symbol of the state of Arizona, although it is widespread within the park it is very difficult to see it as it is shy, as a den it prefers caves, cracks in the rocks or hollow trunks. The coyote (Canis latrans) is widespread in both sections of the park and feeds on both cactus fruit and animals. The American pygmy fox (Vulpes macrotis) is present only in the Tucson Mountains district, its habitat around the park is constantly decreasing and this is compromising the presence of this species within the park. The gray fox (Urocyon cinereoargenteus) is the only species of the canine family capable of climbing trees, both for hunting and for defending itself from predators. Collared pècari (Pecari tajacu) are widespread in the park, they live in groups ranging from 4 to 20 individuals led by an adult female, their diet consists of roots, seeds, cactus fruits and occasionally carrion. The Mephitidae family is represented in the park by the common skunk (Mephitis mephitis), the western spotted skunk (Spilogale gracilis) and the hooded skunk (Mephitis macroura). The silver badger (Taxidea taxus) is very rare in the park, the number of specimens is constantly decreasing due to the disappearance of its habitat in the areas surrounding the protected area.
Albert’s squirrel (Sciurus alberti), introduced in the Santa Catalina Mountains area near the Saguaro park in 1941, has become the most widespread species within the park having surpassed the Arizona gray squirrel (Sciurus arizonensis), a species native to this area. Both species live in wooded areas of the Rincon Mountains. Very easy to spot is the Ammospermophilus harrisii, recognizable by the white stripes on the sides of the body, they are active even during the hottest hours of the day. The Topermophilus variegatus is a ground squirrel that prefers high mountain rocky areas, it is easily observed inside the park. Equally easy to spot, but in the desert area of ​​the park, is the Xerospermophilus tereticaudus. Finally, the Neotamias dorsalis can be seen both in the mountainous areas of the park and at the lower altitudes, but limited to the areas close to the waterways.
The desert hare (Lepus alleni) is not very common in the park and it is possible to spot it mainly in the vicinity of large sandy and dry waterways. The Californian hare (Lepus californicus) prefers the desert area and is active during the cooler hours of the day. The desert cottontail (Sylvilagus audubonii) is very common within the park due to its high reproduction rate, its abundance also makes it a favorite prey of many species of rattlesnakes and other predators such as hawks and lynxes.
Within the Saguaro National Park, we also find numerous species of bats, of which only two feed on nectar and are Choeronycteris mexicana and Leptonycteris curasoae.
Most are insectivores such as Eptesicus fuscus, Macrotus californicus (a species that does not migrate and hibernates during the winter), Myotis californicus, Myotis velifer, Myotis thysanodes (a species that migrates in winter even if today the migration route is unknown), the Lasiurus cinereus, the Myotis volans), the Brazilian molosser (Tatarida brasiliensi), the most widespread species in the southwest of the United States, the desert bat (Antrozous pallidus), the Nyctinomops femorosaccus, the Lasionycteris noctivagans, Myotis auriculus, Townsend’s bat (Corynorhinus townsendii), Parastrellus hesperus (weighs about 3 grams and is the smallest bat in the United States of America), Lasiurus blossevillii, Myotis ciliolabrus, Myotis yumanensis.

Guido Bissanti




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