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[Photo: Jeff Servoss, US Fish and Wildlife Service]
Gila Monster Heloderma suspectum
Description:The Gila monster is a large lizard of the Helodermatidae, or "warty skin" family. The Gila monster's body is stout and grows to approximately 14 inches (35 cm) long. The lizard has a large head with beady eyes and hard, rounded wart-like scales that run the length of its back. It has a long, forked, pink tongue and the snout and sides of its face are black. The tail of the Gila monster is short and fat with three to five colored bands. It has five toes on each leg with long claws used for digging. The body color of the Gila monster is bright (orange, peach, yellow or pink) with either black bands or a black, reticulated (net-like) pattern. These differential markings represent two sub-species of the Gila monster; in the northern portion of its range, the Gila monster is banded, and in the southern part of its range, Gilas are reticulated or mottled.
Life History:The Gila monster can live up to 25 years in captivity. Females are sexually mature at approximately 9.6 inches (24 cm) in length and lay one clutch every other year. The Gila monster mates in spring and summer, laying 2-12 eggs in July or August. Gila monster eggs incubate for a period of ten months, overwintering underground, with eggs hatching in April to June of the following spring. The Gila monster is a carnivore that feeds on young rodents, rabbits, birds, and lizards and the eggs of birds, lizards, snakes and tortoises. Because the Gila monster can store fat in its tail, it only needs to consume three to five meals a year to survive. Gila monsters are diurnal during the spring and fall, nocturnal in the summer, and hibernate from November through February. The Gila monster spends most of its time underground and may only spend 2 percent of its time on the surface every year. The Gila monster is venomous and can inject venom through the teeth in its lower jaw, although rarely does so when feeding on prey. The venom is thought to be for defense rather than prey capture.
Habitat:The Gila monster lives in desert grassland, desert scrub, thorn scrub, and pine-oak or pinyon-juniper woodlands, commonly in mountain foothills. The Gila monster lives at elevations of sea level to over 5,000 feet (~1,500 m). The winter hibernaculum consists of a rocky crevice facing south (warmer). Their year-round shelters may consist of a cooler, soil burrow or nest.
Distribution:Heloderma suspectum
is found in the southwestern US and northwest Mexico. The bulk of the Gila monster's range (specifically the reticulated southern subspecies) is concentrated across western and southern Arizona, down through Sonora, Mexico. The northern banded subspecies is found in northwest Arizona, southeast California, southern Nevada, southwestern Utah, and southwestern New Mexico.
Status:The major threats to Gila monster populations are due to over-collection for the pet trade and habitat loss from urbanization and agriculture. The population size is believed to be at several thousand, but is declining. The Gila monster is a protected species in Arizona. The IUCN Red List considers the Gila monster a "near threatened" species. Although venomous, Gila monster bites associated with humans are non-lethal and very rare.
Western Sierra Madre Piedmont Level 3 & 4 Ecoregions Map [Figure: Houston Advanced Research Center using USEPA data]
The Western Sierra Madre Piedmont ecoregion covers a large portion of southeast Arizona, a small parcel in southwest New Mexico, and extends south into the Sonorran area of Mexico. This ecoregion is also known as the Madrean Archipelago or "Sky Islands" because of the 20 or more isolated mountain ranges in the region. These islands are concentrated areas of biodiversity, representing an ecological link between the Rocky Mountains to the north and the Sierra Madre Occidental Range to the south. The Western Sierra Madre Piedmont is comprised of three major subregions that can be delineated based on the vegetation zones represented at increasing altitudes: Apachian Valleys and Low Hills (below 5,000 feet), Lower Madrean Woodlands (above 5,000 feet) and Madrean Pine-Oak and Mixed Conifer Forests (above 7,000 feet).
Climate & Topography
The landscape is characterized by basins and ranges with high relief (up to 5,000 feet). Elevation varies from 2,600 feet (800 m) to 9,800 feet (3,000 m) over the region. The climate is dry and subtropical. Annual precipitation averages 17 inches (42 cm) per year, with a range from 10-38 inches (26-95 cm). Most precipitation occurs in the form of monsoonal thunderstorms from July to September. Due to the dry climate, many streams (known as washes) are intermittent and ephemeral, with a few perennial streams (e.g. San Pedro, Upper Gila and Santa Cruz Rivers) playas, and springs present. Average annual temperatures range from 50-64 degrees F (10-18 deg C) and the growing season lasts 170-280 days. In the mountain ranges, the bedrock is comprised of volcanic and sedimentary rock, but in the basins thick sediments form the underlying geology. The soils are typical of those found in both arid and forested upland regions with aridic (very dry) and ustic (dry with seasonal wetness) moisture regimes.
Vegetation & Wildlife
At lower altitudes, the semi-desert grassland and shrub-steppe communities dominate the landscape. Typical species are black grama, tobosa, sideoats grama, blue grama, vine mesquite, curly mesquite, yucca, cacti and agave. In the lower elevation mountainous regions, Madrean woodlands featuring silverleaf, Arizona white oak, pinyon and mesquite species are present. Riparian areas feature cottonwood, sycamore and willow. These wooded areas are interspersed with savannas and grassy meadows. At higher elevations, ponderosa pine and pine-oak forests predominate. Even higher, in the sub-alpine zone, Douglas-fir, ponderosa pine, Apache pine, southwestern white pine, gambel oak, alligator juniper and Chihuahuan pine can be found. Tree-of-heaven is a common invasive species in this ecoregion. This ecoregion is rich in biodiversity because of the convergence of two major North American mountain ranges that produces niche habitat for a wide range of tropical species. There are 458 bird species (including many migratory species) and over 240 species of butterflies present in this ecoregion. Additionally, mule deer, cougar, jaguar, coyote, bobcat, antelope jackrabbit, Mexican fox squirrel, Cooper's hawk, red-tailed hawk, raven, turkey vulture, flycatcher, western diamondback rattlesnake, Gila monster, and western whiptail lizards are found here.
Land Use & Environmental Impacts
The major land uses in this ecoregion are cattle ranching, tourism, mining and recreation. Major human impacts include overgrazing of cattle, groundwater depletion, alteration of fire regimes, loss of habitat due to urban development and border activities, and off-road vehicle recreation. Additionally, non-native species are becoming an increasing problem in these isolated biotic communities, with over 60 non-native species identified in this ecoregion so far.
Invasive Species Spotlight: Tree-of-heaven
[Photo: Chuck Bargeron, University of Georgia, Bugwood.org]
Tree-of-heaven Ailanthus altissima
Description:Tree-of-heaven is a large deciduous tree in the tropical family Simaroubaceae. Tree-of-heaven can grow up to 80 feet (25 m) tall with a diameter of 6 feet (1.8 m). The branches are smooth and light gray; twigs are smooth, light gray to chestnut in color, and are arranged in an opposite orientation. Tree-of-heaven has large compound leaves, from 1-4 feet (0.3-1.2 m) in length, and are comprised of 10-40 leaflets. The leaflets are each 2-7 inches (5-18 cm) long, lanceolate, dark green with light green veins above, and grow on light green to reddish-green stalks. The flowers of the tree-of-heaven appear as terminal clusters, from 20 inches long, comprised of yellowish-green flowers, each with five petals and five sepals. The tree-of-heaven produces clusters of wing-shaped fruit, each 1 inch (2.5 cm) long and containing a single green fruit.
Life History:The tree-of-heaven is dioecious (has separate sexes), reaching sexual maturity at two to three years of age. It also reproduces asexually, via vegetative sprouting. The tree-of-heaven flowers from April to June and produces seed-bearing fruit from July to February; it spreads by wind and water dispersed seeds and prolific vegetative sprouting. The tree-of-heaven grows quickly, with seedlings growing 3-6 feet in the first year and sprouts growing 10-14 feet in their first year. The tree-of-heaven releases allelopathic chemicals in the soil, which inhibit the growth of other plant life.
Habitat:Tree-of-heaven inhabits open areas with disturbed soils such as agricultural fields, roadsides, fencerows, woodland edges, forest openings, rocky areas, and urban habitats such as alleys, parking lots and streets. The tree-of-heaven is tolerant to pollution. It does not grow in very wet or heavily shaded areas.
Distribution:Ailanthus altissima
is native to eastern China, but was introduced into the US (Philadelphia, PA) as an ornamental tree by European settlers in 1784 and was also heavily imported by Chinese immigrants in California throughout the 1800s. In the United States, tree-of-heaven is currently distributed in 42 states and reported invasive in 30 states.
Status:Tree-of-heaven is an aggressive, fast-growing non-native plant. It is a prolific seeder and sprouter (grows 10-14 feet in the first year) and can quickly produce dense patches which crowd out native species. Additionally, it produces allelopathic chemicals, making the soil uninhabitable by other plant species. Few wildlife species use the tree for food or shelter. Common control methods for tree-of-heaven include foliar herbicide spraying for large patches and mechanical cutting with chemical stump treatment for smaller infestations. Hand pulling is an effective control method for seedlings.
A melanistic jaguar [Photo: Ron Singer, US Fish and Wildlife Service]
Jaguar Panthera onca
Description:The jaguar is the third largest cat in the world (behind the lion and tiger) and a member of the cat family, Felidae. The male body length is 6.4 feet (1.9 m) long with an additional tail length of 21 inches (53 cm), and females are 5.2 feet (1.6 m) long with a 17 inch (43cm) tail. The height at the shoulder of the male is 28 inches (71 cm) and jaguars weigh from 150-300 pounds (68-136 kg). The jaguar body is robust and muscular with short, bulky limbs. The jaguar has a large head with small, rounded ears. The upper parts of the body are cinnamon colored with numerous black spots, often with lighter colored centers. The inner surfaces of the legs are white and heavily spotted with black spots. The tail of the jaguar is short relative to its body size and has irregular black bands. Melanistic jaguars, those that have excessive pigment, comprise 6 percent of the jaguar population and appear either as completely black or charcoal with faint markings; these are polymorphisms and do not represent a separate species.
Life History:The jaguar lives to be approximately 11 years old. Female jaguars become sexually mature at three years of age and males are mature by age four. The jaguar breeds year round throughout most of its range, but only breeds in the spring in the extreme northern and southern portions of its range. Females give birth every two years, gestation length is 93-110 days and litters consist of 1-4 cubs (most often 2). Kittens weigh about 2 pounds (~1 kg), are covered with fur, and heavily spotted at birth. Jaguars exhibit cooperative parenting for the first year of the cub's life. Jaguar cubs remain with the mother for two years, but begin to find their own food after the first year. The jaguar feeds on peccaries, capybaras, deer, pacas, armadillos, caimans, turtles and a variety of birds and fish. The jaguar's range can consists of up to 15 square miles (38 sq km) for females and up to 30 square miles (76 sq km) for males. Jaguars mark their territory via scent marking and will roar at other jaguars to announce themselves.
Habitat:In the US, jaguar habitat consists of Sonoran desert scrub, evergreen woodland, semi-desert grassland and subalpine conifer forest. Jaguars are found at elevations from 30-6,500 feet (10-2,000 m), and in Mexico and south America, are more often associated with swampy savanna or tropical rain forests. The jaguar prefers warm climates and is almost always associated with water. Jaguar dens are often found in caves or dense thickets.
Distribution:Panthera onca
is distributed from southeastern Arizona and southwestern New Mexico south to northern parts of Argentina. The jaguar was once distributed in California, Texas, and Louisiana as well, but has not been spotted in these states for an extensive period (late 1800s). There are no known breeding populations of jaguars remaining in the US, as the jaguars in the US are part of a breeding population from northern Mexico.
Status:The jaguar is a federally listed endangered species (originally listed in 1972, extended in 1996). The USFWS has deemed that a critical habitat designation is prudent and critical habitat should be proposed sometime in 2011. The major threats to the jaguar are from illegal takings (shootings) and habitat loss. The Arizona-New Mexico Jaguar Conservation Team (JAGCT) is currently promoting interstate and international cooperation for education and enforcement efforts dealing with jaguar shootings, and conservation of jaguar habitat, especially habitat corridors in the US and in border areas.
