Sonoran Desert

Stingrays in the desert

You probably don’t think of stingrays when visiting the desert. However, several species of stingrays inhabit the Gulf of California which is part of the Sonoran Desert. Last October, the Arizona Sonora Desert Museum opened a new exhibit featuring cownose stingrays. At the Museum, the stingers have been clipped. The exhibit allows the sting rays to touch you (rather than you touching the rays). They feel like wet velvet. The skin of a ray is covered by tooth-like structures (called dermal denticles) instead of scales like fish.

Rays are bottom feeders. “Besides gills, rays have an extra adaptation to help them breathe while resting on the bottom of the ocean. These special openings, which are near their eyes, are called spiracles. Instead of sucking sandy water in through their gills, they can pull clear water in through their spiracles. They then push the water out through their gill slits.” (ASDM)

Stingrays (skates and ratfishes) are close relatives of sharks and evolved from sharks about 200 million years ago during the Jurassic Period. Like sharks, rays have a cartilaginous skeleton rather than hard bones. In rays, the front fins have expanded around the head to form a pectoral disk that act like wings. Most rays are marine animals, but some have evolved to tolerate brackish and fresh water.

Differences between bony fish and rays (info from Arizona Sonora Desert Museum):

Bony fish have a bony skeleton, overlapping ganoid, cycloid or ctenoid scales, a gill opening covered by a bony plate called an operculum, flexible pectoral fins, a swim bladder and internal fertilization. The operculum allows fish to actively pump water over their gills. Having flexible pectoral fins made up of fin rays allow bony fish to be more maneuverable, navigate tight spaces, and the ability to turn around. A swim bladder is a gas filled organ that helps control the buoyancy of a bony fish.

Sharks and rays a cartilaginous skeleton, tooth-like scales called dermal denticles or placoid scales, five to seven pairs of gill slits, no swim bladder, very large liver, fixed pectoral fins, spiral valve intestine, specialized electroreceptors called the ampullae of Lorenzini, and internal fertilization. Since cartilaginous fish lack a swim bladder for buoyancy, they have a significantly enlarged liver filled with oil called squalene that helps them float.

The following photos and information, from the Arizona Desert Museum, shows the rays which inhabit the Gulf of California. Visit the museum and be touched by a ray.

 

The Cactus Mouse – another creature of the night

cactus-mouse-nps

The Cactus mouse (Peromyscus eremicus) is one of eight species in the genus Peromyscus that inhabit Arizona. All are similar-looking grayish-brown, with white bellies and feet, and large ears. They are about 3.5 inches long. The cactus mouse has a sparsely furred tail with a slight tuft at the tip. “Females weigh slightly more than males and are significantly larger in body length, ear length, length of mandible and bullar width of skull. Cactus mice can be identified by having naked soles on their hind feet, and almost naked tails which are usually the same length or longer than the animals body length.” (Source)

The Cactus mouse ranges from southern California and Nevada, through southern Arizona and New Mexico, west Texas into northern Mexico. They are common in washes and rocky hillsides, in sandy deserts and desert foothills. Depending on location, they may breed throughout the year. A female may produce 3 to 4 litters per year, each with 4 to 5 young.

cactus-mouse-range

Cactus mice are nocturnal feeders. They eat seeds, fruit, and succulent plant material. Their diet includes mesquite beans and leaves, and insects. During the day they remain in burrows in clumps of cacti, in the ground, or among rocks. Their nests are usually a ball of grasses or twigs.

According to the Arizona-Sonora Desert Museum:

“The cactus mouse often climbs around in vegetation and brush, searching for seeds and fruits to eat. It may nest in wood piles or rock piles, or use the abandoned burrows of other animals. Although this mouse needs less water than many others and is desert-adapted, it may estivate or go into a torpor in the summer when resources for food and moisture are not available.”

“These little rodents are at the bottom of the vertebrate food chain, preyed upon by everything from coyotes and snakes to hawks and bobcats. In response, they breed prolifically, with some species, like the cotton rats, able to produce eight to ten litters a year. Populations still fluctuate with drought and predation, but the mice and rats are able to respond to good conditions by rapidly rebuilding their numbers.”

“All rodents, including the mice and rats, are gnawers. Their teeth are ever-growing and must be kept trimmed down by constant gnawing. A layer of hard orange enamel covers the front surface of the teeth. The rest of the tooth is softer and wears down quicker than the enamel as the rodent gnaws, thus creating a chisel-like shape to the front teeth that is unique to the rodent family.”

Other desert rodents:

Creatures of the night – Pocket Mice

Ferocious Grasshopper mouse

Kangaroo rat

Pack Rats are Desert Archaeologists

 

 

 

 

 

 

 

Eurasian Collared-Doves

eurasian-collared-dove-6

Have you seen this bird? Collared doves have been showing up in my backyard for the past few years. They flock with other doves and I rarely seen more than one collared dove at a time.

The Eurasian Collared-Dove (Streptopelia decaocto) is about 12 inches long and has a wingspan of about 14 inches which makes it larger than a Mourning dove and about the same size as a White-winged dove.

According to the Cornell Lab of Ornithology:

“Eurasian Collared-Doves made their way to North America via the Bahamas, where several birds escaped from a pet shop during a mid-1970s burglary; the shop owner then released the rest of the flock of approximately 50 doves. Others were set free on the island of Guadeloupe when a volcano threatened eruption. From these two sites the birds likely spread to Florida, and now occur over most of North America.”

Eurasian Collared-Doves eat mainly seeds and cereal grains. They will occasionally eat berries, plant greens, and bugs. Their principal habitat appears to be urban and suburban areas, especially where people put out bird feeders. They may also occur on farms.

“Mainly ground foragers, they peck at grain and seeds scattered beneath backyard feeders and on feeding platforms, or spilled at farmyards. Flocks of 10 to several hundred doves may gather at prime spots. Although they can feed peacefully in mixed flocks, Eurasian Collared-Doves will also chase off other birds, including Mourning Doves, cardinals, and Blue Jays.” (Cornell)

Nesting (source, Cornell):

“The male dove brings the female twigs, grasses, roots and other nesting materials, which he sometimes pushes directly under her. Over 1 to 3 days she builds a simple platform nest, which may include feathers, wool, string and wire. A pair often uses the same nest for multiple broods during the year, and may renovate old nests.

“Males show females potential nest sites in trees and on buildings, giving a low- pitched, slow koo-KOO-kook call at each site (listen here). Nests are usually built 10 or more feet above the ground. In warmer regions, Eurasian Collared-Doves can nest year-round, which may help explain their success as colonizers.”

“Eurasian Collared-Doves are one of very few species that can drink “head down,” submerging their bills and sucking water as though drinking through a straw. Most birds must scoop water and tip the head back to let it run down into the throat.” (Cornell)

Eurasian Collared-Doves may be mistaken for Ringed Turtle Doves which are slightly smaller and lighter in color. According to the Sibley Guide to Birds, the Ringed Turtle Dove is a domestic variety, not a naturally occurring species, and it fares poorly in the wild.

See also:

Mourning Doves

White-winged Doves

Black-necked Stilt

black-necked-stiltThe Black-necked Stilt (Himantopus mexicanus) is a fun bird to watch as it noisily feeds along shorelines. (Listen to sounds). This Stilt occurs in the southern and western U.S. Its range includes the Great Basin, Sonoran and Chihuahuan deserts near bodies of water. The Sonoran Desert, south to the tip of Baja, California Mexico, is within its year-round range. You can see some at the Arizona-Sonora Desert Museum where I took the photograph.

black-necked-stilt-rangeThe Black-necked Stilt stands about 18 inches high and has a wingspan of 28 inches. It has a black head, neck and back over a white body. Its bill is long and black. One of its most striking features is its very long, red/orange legs. “ They have the second-longest legs in proportion to their bodies of any bird, exceeded only by flamingos.” “Five species of rather similar-looking stilts are recognized in the genus Himantopus.” (Source)

Stilts forage, often in groups, in shallow water or along shorelines for insects and other prey. Cornell Lab of Ornithology adds: “Black-necked Stilts wade in shallow waters to capture their meals of aquatic invertebrates and fish. They often consume such fare as crawfish, brine flies, brine shrimp, beetles, water boatmen, and tadpoles. They peck, snatch, and plunge their heads into the water in pursuit of their food, and will herd fish into shallow waters to trap them there.”

According to ASDM: “These are ground-nesting birds, whose eggs are well camouflaged and whose downy chicks can run about and find their own food shortly after hatching. Adults defend eggs or chicks with a repertoire of distraction displays. These birds are good runners and strong flyers.”

According to Cornell: “Male and female Black-necked Stilts trade off the job of constructing the nest. While one mate observes, the other scrapes into the dirt with breast and feet to form a depression about 2 inches deep. As they dig, they throw small bits of lining over their back into the nest. Most lining is added to the nest during incubation, and consists of whatever material is closest to the nest, including grasses, shells, mud chips, pebbles, and bones.” “ During breeding and during winter, they are strongly territorial birds, and are particularly aggressive to chicks that are not their own. When not breeding, Black-necked Stilts roost and forage in closely packed groups, often staying within a foot of each other. Black-necked Stilts are semicolonial when nesting, and they participate en masse in anti-predator displays. The displays include one in which nonincubating birds fly up to mob predators, and one in which all birds encircle a predator, hop up and down, and flap their wings.”

A more general note on shorebirds from ASDM:

Shorebirds in general do most of their foraging along the water’s edge, probing in soft mud or picking at the surface in search of tiny invertebrates. They belong to several related families. The largest shorebird group is the sandpiper family (Scolopacidae); nearly two dozen species of sandpipers migrate through the Sonoran Desert, but for the most part their presence with us is fleeting, a few days’ stopover as they travel between breeding grounds on Arctic tundra and wintering grounds on southern coasts. More relevant here are two long-legged waders and one plover that are with us for much of the year.

The avocets and stilts make up a small family, with only a few species worldwide. All are slim birds with long necks, thin bills, very long legs, and striking patterns. All forage in shallow water, feeding on small invertebrates. North America has one avocet and one stilt. Both have ranges which extend into the Sonoran Desert, where they seem to have benefited from human activity; most of their modern nesting sites are around the edges of artificial ponds.

Matilija poppy (fried egg plant)

The Matilija poppy (aka the fried egg plant), Romneya coulteri, is native to southern California and northern Mexico. The shrub, itself, can get up to 8 feet tall, and the flowers are upto 8 inches in diameter.

They are called “fried eggs plants” because the flower has an intense yellow center in a field of crinkled white petals. The plant is also known as a “fire follower” because it frequently establishes itself in recently burned areas. The California Native Plant Society claims that seeds will not germinate “unless they have experienced the flash heat of wild fire.”

Matilija poppy

The plant is a perennial that prefers sunny locations and good soil, but will grow in clay, and in dry, rocky soil. The flower has an apricot-like scent. Individual flowers last several days, then form seed pods that resemble a bird cage.

The foliage consists on blueish-gray to green, deeply lobed leaves that have a leathery texture. The base of the stems often become woody with age. The plant acts as a semi-shrub, spreading by rhizomes year by year until large clumps are formed.

The flowers bloom from late Spring through late Summer. You can see some at the Arizona-Sonora Desert Museum. (See more photos here.)

Planting the Matilija poppy in a garden is apparently hit or miss. According the an article in the Los Angeles Times: “If a Matilija poppy doesn’t like where it’s planted, it will promptly wither and die. If it does like the location, then after a modest first season, the Matilija can proceed to colonize a garden. Success can be uneven.” According to another California source, Growing Native, “This plant has idiosyncratic and unpredictable needs. It will sulk and die in what you would think would be a perfect place, and thrive gloriously in an apparently unsuitable one.”

A tincture or tea made from this plant has been used externally for skin inflamation due to allergies or sunburn. This concoction is also reputed to have antimicrobial properties. (Source).

Sphinx Moths

Sphinx moth adult

Sphinx moth caterpillar

Sphinx moths (also called hawk moths and hummingbird moths) belong to a large family, Sphingidae, with about 1450 species. These are large moths with wingspans up to six inches.

Most common in the Tucson area is the White-lined sphinx moth (Hyles lineata) which has a wingspan of up to 5 inches and a body length of up to 3.5 inches. Its range extends from Central America, throughout the U.S. and into southern Canada. These moths are often mistaken for hummingbirds at first glance because they are about the same size and behave much like hummingbirds. They are fast flyers and can hover at a flower to sip nectar with their very long tongues; and they can fly side-to-side, and backwards. These moths are mainly nocturnal but may be about during daylight hours. The first generation adults appear in mid-May, with subsequent generations appearing throughout the summer. See good close-up photos of the adult moth and caterpillar here.

Life cycle:

Adults females lay eggs generally on the underside of leaves upon which they feed. The eggs hatch into the larval stage – caterpillars. The sphinx moth caterpillar, which can be up to 5 inches long, is generally bright green with dark spots, but it can also be almost completely black or striped yellow and brownish. It has a large (harmless) hook on its back end similar to a tomato “hookworm.” According to DesertUSA, the name “sphinx moth” derives from the behavior of the caterpillar. “When alarmed, these larvae rear up their heads in a threatening sphinx-like posture and may emit a thick, green substance from their mouths.”

To complete pupation, the caterpillars dig burrows. Pupation can last from two weeks to several months depending on species and conditions. The adults moths dig themselves out from underground and may mate soon thereafter. According to DesertUSA, “In the Sonoran and Chihuahuan deserts, there may be two broods, one in the spring and another in summer. In the colder Great Basin desert, only one brood is produced.” In some species, if pupation begins in the Fall, it will last all winter with adults emerging in the Spring.

The moths feed exclusively on nectar and seek out flowers which have large supplies. This includes the evening primrose (see my ADI primrose article and a photo of the long tongue of a sphinx moth.) Some species can be harmful to crops.

According to a study at the University of Arizona, the Tohono O’odham would harvest the caterpillars, dry and braid them and use them as food. The study says that the caterpillars are not poisonous, but warns that eating too many will result in an upset stomach. (It doesn’t say how many are too many.)

Mexican Cardon Cactus – the world’s largest cactus

Mexican cardon 3

The icon of the Sonoran Desert in Arizona is the large Saguaro cactus (Carnegiea gigantea). But there is a larger cactus in the southern part of the Sonoran Desert: the Mexican Cardon (Pachycereus pringlei), which is native to Sonora and Baja California. The Saguaro commonly reaches 40 feet high and may get larger; the Cardon commonly reaches 60 feet high and more.

The Cardon is not as frost tolerant as the Saguaro. That is why it does not grow naturally in Arizona. The photo above shows a Saguaro on the right and a Cardon on the left. This photo was taken at the Arizona-Sonora Desert Museum and you can see that the Cardon shows frost damage. See more photos from Google images.

According to ASDM:
“The Cardón resembles the Saguaro in growth form but it is much more massive. It develops a very thick trunk and the branches are closer to the ground and often more numerous than those of a typical Saguaro. In sheltered locations plants may exceed 60 feet tall. Young stems are armed with stout spines; mature stems are nearly spineless and have bluish epidermis between the rows of closely-spaced felty areoles on the external ribs. The flowers are similar to those of a Saguaro, but with more and narrower tepals. The ovoid fruits are densely covered with felty areoles; on different plants they range from spineless to very long-spiny. The juicy pulp of ripe fruits ranges from white to red and contains large, hard seeds—very different from the tiny seeds of the Saguaro.”

The ribs of the Cardon are generally fewer and more widely-spaced compared to a Saguaro.

Saguaro flowers occur mainly at the top of the trunk and arms. Cardon flowers may extend down the sides of the stems. Flowers of both cacti are large, white, and pollinated mainly by bats. The flowers of both cacti open at night and stay open for about 18 hours. The Saguaro has the edge in pollination because its flowers produce a second batch of nectar in the morning for birds and insects. As a result, about 70% of Saguaro flowers set fruit versus only 30% for the Cardon flowers.

Cardon flowers

Cardon fruit 2

Cardon fruit was an important food for the Seri people in Sonora, who call the cactus xaasj.

The flesh of this cactus contains alkaloids, and may have been used as a psychoactive plant in Mexico according to Wikipedia which also notes: “A symbiotic relationship with bacterial and fungal colonies on its roots allows P. pringlei to grow on bare rock even where no soil is available at all, as the bacteria can fix nitrogen from the air and break down the rock to produce nutrients. The cactus even packages symbiotic bacteria in with its seeds.”

Saguaros have a life span of about 200 years, whereas Cardons can live 300 years (Source).

There is another cactus called “Cardon.” This one lives mainly in Argentina and is frost tolerant as is the Saguaro.

The Argentinian cardon (Trichocereus pasacana) is “A robust, Saguaro-like, South American columnar cactus, this differs from its North American counterpart in its denser, more bristly spination and less [sic] branched stems. These are stout, to 1′ in diameter, to 30′ or more tall, branching and candelabriform only in age. Like the Saguaro (Carnegiea gigantea) in the Sonoran Desert, T. pasacana is a dominant component of the vegetation in many habitats in northern Argentina and southern Bolivia, where it can form nearly homogeneous stands.” (Source)

A specimen of the Argentinian Cardon may be seen at the Arizona-Sonoran Desert Museum near the art gallery.

See also: Saguaro Cactus Icon of the Sonoran Desert and

Life on a dead saguaro

Photo credit: Cardon fruit from Deborah Small’s Ethnobotany Blog

Lilac Crowned Parrots

LC 1

Lilac crowned parrots (Amazona finschi), also known as Lilac crowned amazons and Finsch’s amazon, are endemic to the Pacific coast of Mexico where they inhabit deciduous and semi-deciduous forests. There are also (probably feral) populations in southern California and in south Florida.

Lilac crowned parrots are relatively small, reaching about 12 inches in body length. Audubon describes them as “Lime green overall, lighter on breast and abdomen. Distinct band of deep red-maroon across the forehead between the eyes. Lilac-blue across the top of the head, over the nape and sides of the neck. Legs and feet are blue-gray. The end of the tail is noticeably longer than similar species, but squared off, not as pointed as similar species. May be confused in mixed flocks, with the similar Red-Crowned Parrot, Amazona viridigenalis.” Males and females have the same plumage.

They eat mainly fresh fruit, vegetables, and some seeds and nuts.

Lilac crowned parrots are cavity nesters and generally find suitable sites in the forest along the Pacific coast between elevations 1000 to 6000 feet. The female normally lays 2-4 eggs which are incubated for 26 days. Chicks generally fledge about 60 days after hatching. Life-span in the wild is about 30 years and they can live up to 60 years in captivity.

These birds are quite social and can occur in flocks of several hundred individuals. The large flock size helps deter predatory falcons and hawks. The parrots are also very noisy and have many vocalizations. In captivity they mimic humans, cats, and many other things. One at the Arizona-Sonora Desert Museum can do a very loud fire engine.
See video of a captive parrot vocalizing: https://youtu.be/opajOjrkmiY 1:29 min.

According to some veterinarians:

“The lilac-crowned Amazon is a sweet and compelling character, often fearless to a fault, like many of the Amazons, but is full of personality and is a loyal companion when socialized properly.” But, “At sexual maturity, this species can get cranky and nippy, even unpredictable and sometimes vicious or protective of its territory, just like many of the other Amazons. This is typical behavior and shouldn’t last long, though it can be insulting and daunting for sensitive owners. For this reason, the Lilac-crowned is a good choice for the seasoned bird-keeper rather than the novice.”
The photo above is of “LC” a female parrot at the Arizona-Sonora Desert Museum. She is quite social with visitors and flirts with human males. She adopted a coquettish pose for me.

Elf Owls

Elf owl 3The Elf owl (Micrathene whitneyi) is our smallest owl. Its body size is about the same as a sparrow (5 to 6 inches), but its wingspan is larger (13 to 16 inches).

These owls occur in southern Arizona, the boot-heel of New Mexico, the Big Bend area of Texas, and nearly all of Mexico including the southern tip of Baja. In the winter, Elf owls in the U.S. generally migrate to Mexico.

“The classic image of an Elf Owl looking out of a hole in a Saguaro cactus may be overemphasized. They are abundant in the Saguaro deserts but also are abundant into the mountains reaching elevations of up to about 6000 ft. They can be found in dense mesquite, dry oak woodlands, wooded canyons, sycamores, and probably any other tree within its elevation range. They may be seen in dense scrub and in woodpecker holes in cottonwoods or telephone poles. Classically they are in high desert, foothills, and low in the mountains, and often in dryer habitats.” Source

Elf owls eat spiders, scorpions, beetles, moths, grasshoppers, crickets and other insects. They generally hunt at dawn and dusk. They can catch prey in mid-air or pluck them off tree branches.

Elf owl 2Elf owl 4

Elf owls often nest in abandoned woodpecker holes in saguaro cactus and in natural cavities in upland trees such as sycamores, pines, and walnuts. “Males attract females to potential nest sites by calling from a cavity, then flying out while singing as she approaches. On moonlit nights calling occurs continuously all night. The female selects the nest cavity and begins to roost in it prior to laying eggs to prevent occupation by other hole-nesting birds.” Source “Breeding season in North America is normally May and June (March through August in Mexico). 1 – 5 eggs may be laid but 3 are most common. The incubation period is 21 – 24 days. The young can capture food as soon as they can fly (27-28 days of age) and fledge shortly thereafter (28 – 33 days of age).” Source

The call consists of a variety of soft yelping notes, often running together into a high-pitched chatter. You can hear some sound recordings here.

According to the Arizona-Sonora Desert Museum:

“Elf Owls, like other owls have excellent night vision. They can’t see in complete darkness, but they can see quite well in low-light. They also have excellent hearing. They can catch their prey in complete darkness, by pinpointing it using their ears rather than eyes. Elf owls have “silent flight” which means they don’t make any noise as they approach their prey. The sound of their wing beat is muffled by softened feathers on the leading edges of their wings.” Source

Elf owls are preyed upon by other owls, snakes, coyotes, bobcats and ringtails. Their life span in the wild is 3-6 years. Starlings, which are an introduced bird from Europe, pose a threat to Elf Owls. They take over nest cavities already in use by the Elf Owls, or by other birds according to ASDM. ASDM also notes that in dangerous situations, Elf owls will play dead until all danger has passed.

See many photos here.

The American Beaver in Arizona

Beaver 1Beaver 2

The American beaver (Castor canadensis) is the largest rodent in North America with adults reaching a weight of up to 70 pounds with an average of 40 pounds. (The porcupine is the second largest rodent, see my  article: Porcupines.) The American beaver ranges throughout the U.S. and Canada. It has also been introduced to parts of South America. A different beaver species (Castor fiber) occurs in Eurasia.

Beavers are semi-aquatic mammals that are most active at night. They are excellent swimmers and can stay submerged up to 15 minutes. They have webbed hind feet and a broad, flat tail which propel them through water.

Beavers build “lodges” and dams in lakes and rivers using sticks, stones, grass, and mud. Their structures often have a great (and beneficial) effect on the local ecology.

Beavers eat the leaves, twigs, and inner bark of many tree species. Fermentation by special intestinal microorganisms allows beavers to digest 30 percent of the cellulose they ingest. (source)

Beavers are prized for their fur which consists of long, coarse outer hairs and short, fine inner hairs. The fur has a range of colors but usually is dark brown. Scent glands near the genitals secrete an oily substance known as castoreum, which the beaver uses to waterproof its fur. Beaver meat tastes similar to beef, but care must be taken in preparation to avoid getting the castoreum on the meat. The characteristics of the fur led to extensive hunting and in some place, extirpation of the beaver. For more extensive general information see this Wikipedia article.

Beavers in Arizona:

According to the Arizona Game & Fish, beavers were at one time found nearly everywhere in Arizona that had permanent water. With settlement, and the desiccation of the state’s streams, beaver populations declined. This habitat loss, and in some cases, heavy trapping pressure, caused beavers to disappear from such former strongholds as the San Pedro and Santa Cruz rivers. Reintroduction programs and natural colonizations have since enabled the beaver to recover much of its former distribution, if not numbers, and these animals can now be found along several permanent streams, some of the larger river stretches, certain shallow lakes, and even a few dirt-lined canals.

The Winter, 2014, issue of Sonorensis pubished by the Arizona-Sonora Desert Museum has a good article on Arizona beavers (pages 18-23).

The article entitled “Aquatic Architects at Work: the Return of Beaver to the San Pedro River National Conservation Area” begins: “In 1826, trapper James Ohio Pattie dubbed the lower San Pedro River “Beaver River.” He and his party had been trapping beaver along the Gila River and its tributaries, but found that northern stretch of the San Pedro “very remarkable for the number of its beaver…At this place we collected 200 skins.”

The article claims: Beavers influence community diversity and ecosystem structure through tree felling and dam building. Beaver herbivory tends to result in large woody material in the floodplain, which enhances the amount of water that may be captured and stored. Water impounded behind beaver dams increases the area of riparian habitat, and, through groundwater recharge, leads to elevated water tables.

The United States Geological Survey, in cooperation with the University of Arizona recently published a paper which evaluated ecological benefits of restoring beavers to the San Pedro (read full study).

The paper’s abstract says:

We measured bird abundance and richness along the upper San Pedro River in 2005 and 2006 to investigate how beavers (Castor canadensis) may act as ecosystem engineers after reintroduction to a desert riparian area in the Southwestern United States. In areas where beavers colonized, we found higher bird abundance and richness of bird groups, such as all breeding birds, insectivorous birds, and riparian specialists, and higher relative abundance of many individual species—including several avian species of conservation concern.

After accounting for environmental factors, such as presence or persistence of surface water, and extent of Frémont cottonwood (Populus fremontii) and Goodding’s willow (Salix gooddingii), the relative influence of beaver activity was not as strong as these other environmental factors. However, there was still evidence of an association between beaver activity and bird abundance and richness, as models that included beaver-related variables better explained variation in bird abundance and richness for 71 percent of species groups and 46 percent of individual species for which we built models. Although the effect sizes associated with the beaver influence on the bird community were smaller than similar studies conducted in other regions of North America, the biological significance of beaver activity in the upper San Pedro River riparian area will likely become even stronger with increasing time.

AZ Game & Fish studied the suitability of re-establishing beavers in Cienega Creek. The 2008 study concluded that certain reaches were suitable.

You can see beavers at the Arizona-Sonora Desert Museum. ASDM has a story about a “beaver breakout” from the Museum. “One night, the beavers left their pond, waddled through the bighorn enclosure and escaped into the desert. The next morning Museum people followed their tracks, which headed west and before long stopped near a set of coyote tracks. Swirling beavertail prints in the sand showed how the beavers had made an about-face and headed back to the safety of their pond. They never attempted another escape.” source

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