San Bernardino kangaroo rat
Encyclopedia
The San Bernardino Kangaroo Rat,Dipodomys merriami parvus, is a species of rodent in the family Heteromyidae
. It is one of 19 recognized subspecies of Merriam's Kangaroo Rat (Dipodomys merriami) that are spread throughout the arid regions of the southwestern United States and Mexico. Like D. merriami, the San Bernardino Kangaroo Rat has the diagnostic trait of having four toes on its hind legs. Additionally, because of its geographic isolation, it has become the most highly differentiated subspecies of D. merriami.
species: large hind feet for jumping, long tail for balance while jumping, cheek pouches for foraging, and so on. Its body is about 95 millimeters (mm) (3.7 inches (in))long, with a total length of 230-235mm (9-9.3 in). Its body color is weakly yellow with a heavy overwash of dusky brown. The tail stripes are medium to dark brown, with dark brown tail hairs and foot pads. Its flanks and cheeks are dusky.
D. m. parvus is substantially darker and smaller than the other two D. merriami subspecies that live in Southern California (Dipodomys merriami merriami and Dipodomys merriami collinus). This marked adaptation
to its habitat has lead Lidicker to say that "it seems likely to have achieved nearly species rank." (Lidicker 1960)
, soil texture is a primary factor in determining species distributions. (Brown and Harney, 1993)
The range of D. m. parvus is isolated from members of D. m. merriami at the northernmost extent of their range by 8-13 kilometers (km) (5–8 miles (mi)) of unsuitable habitat, indicating possible past intergradation
of the two subspecies.
San Bernardino Kangaroo Rats inhabit places with sandy loam
substrates, characteristic of alluvial fans and flood plains, where they are able to dig small, simple burrows. Plantlife in such areas is typically dominated by chaparral
and sage scrub. These alluvial scrub habitats can be classified as pioneer, intermediate, and mature, in order of decreased frequency of flooding and increased density of plants. Of these subsections of this particular habitat, D. m. parvus is most populous in intermediate alluvial scrub.
D. m. parvus is found unequally distributed between seven isolated locations. The four smallest remnant populations reside near City Creek, Etiwanda
, Reche Canyon, and South Bloomington
. The largest populations with the most area of suitable habitat are located near the Santa Ana River
, Lytle
and Cajon Creek, and the San Jacinto River
.
The historical range of D. m. parvus encompassed roughly 128,000 hectares (ha) (320,000 acres (ac)); by the 1930s the its range had been reduced to roughly 11,200 ha (28,000 ac). As of 1998, its range is approximated at only 1,299 ha (3,247 ac).
, degradation, and fragmentation
by sand
and gravel mining
, flood control
projects, urban development, vandalism, and inadequate regulatory mechanisms."
While sand and gravel mining and urban development have direct impact upon the habitat, flood control projects such as dams
, levees, and berms indirectly change the habitat by preventing flooding. Curtailed flooding in these habitats will cause succession of the preferred 'intermediate' alluvial scrub habitat to 'mature' habitat, as removal and deposition of sand that would normally come with flooding has ceased. Furthermore, in areas with sufficient soil moisture, shrub densities will exceed the sparse to moderate densities where this subspecies lives. (Hanes et al. 1989, McKernan 1997)
Areas that are affected include the Santa Ana River
, Lytle
and Cajon Creek, and the San Jacinto River
.
Urban development, in addition to directly destroying habitat, brings with it domesticated cats
, a documented predator of the San Bernardino Kangaroo Rat. The likelihood of predation increases as the interface between natural and urban habitats is increased.
1) Lead agencies made choices detrimental to D. m. parvus under California Environmental Quality Act and National Environmental Policy Act
,
2) California Environmental Quality Act rulings are subject to overriding social or economic decisions,
3) California's Natural Community Conservation Planning program, which is responsible for conserving alluvial scrub, is a voluntary program which San Bernardino and Riverside counties had not joined,
4) The Surface Mining Control and Reclamation Act of 1977
requires that the parts of the D. m. parvus range used for mining undergo land rehabilitation
; however, this will not likely have a beneficial effect on the species due to the changed topology and
hydrology,
5) The Bureau of Land Management
set aside three areas along the Santa Ana River for preservation of federally listed species such as D. m. parvus, the Santa Ana River Woolly Star (Eriastrum densifolium
ssp. sanctorum), the Slender-Horned Spineflower, and the California Gnatcatcher. However, these areas are also allotted for potential water conservation
projects such as percolation basins
, and the areas allotted for the federally listed species seldom overlap with the range of D. m. parvus.
6) Finally, the Clean Water Act
does not provide for conservation of threatened animals, and while projects executed under that act require a permit from the U.S. Army Corps of Engineers, that agency has "allowed projects to proceed without their overview" within their jurisdiction.
, the isolated ranges and small populations of D. m. parvus makes increased mortality rates more likely. Reduction in habitat size and species isolation leads to population loss "greater than expected from habitat loss alone," and this trend is well documented for rodents and other vertebrates. (Soule´ et al. 1992, Andren 1994, Bolger et al. 1997)
Isolated populations, being restricted to relatively small local areas, are more subject to extirpation
from natural or manmade events, such as floods or drought
. Due to their small population, they may also lose genetic variability
and experience
inbreeding depression
. Isolation of groups is increased by the construction of railroad tracks, roads, and flood control channels.
Extirpation
from flooding is becoming more likely as urban development pushes the remaining populations to the active flood plain. Due to the engineering of these allotted flood areas, the frequency and severity of flooding makes them uninhabitable. Likewise, in the areas where flooding has been diverted, the canopy density of the brush has increased beyond suitable levels for D. m. parvus.
Heteromyidae
The family of rodents that include kangaroo rats, kangaroo mice and rock pocket mice is the Heteromyidae family. Most heteromyids live in complex burrows within the deserts and grasslands of western North America, though species within the Heteromys and Liomys genera are also found in forests and...
. It is one of 19 recognized subspecies of Merriam's Kangaroo Rat (Dipodomys merriami) that are spread throughout the arid regions of the southwestern United States and Mexico. Like D. merriami, the San Bernardino Kangaroo Rat has the diagnostic trait of having four toes on its hind legs. Additionally, because of its geographic isolation, it has become the most highly differentiated subspecies of D. merriami.
Physical description
The San Bernardino Kangaroo Rat follows the same body plan as Dipodomys merriami and other kangaroo ratKangaroo rat
Kangaroo rats, genus Dipodomys, are small rodents native to North America. The common name derives from their bipedal form: as they hop in a manner similar to the much larger kangaroo, although they are not related...
species: large hind feet for jumping, long tail for balance while jumping, cheek pouches for foraging, and so on. Its body is about 95 millimeters (mm) (3.7 inches (in))long, with a total length of 230-235mm (9-9.3 in). Its body color is weakly yellow with a heavy overwash of dusky brown. The tail stripes are medium to dark brown, with dark brown tail hairs and foot pads. Its flanks and cheeks are dusky.
D. m. parvus is substantially darker and smaller than the other two D. merriami subspecies that live in Southern California (Dipodomys merriami merriami and Dipodomys merriami collinus). This marked adaptation
Adaptation
An adaptation in biology is a trait with a current functional role in the life history of an organism that is maintained and evolved by means of natural selection. An adaptation refers to both the current state of being adapted and to the dynamic evolutionary process that leads to the adaptation....
to its habitat has lead Lidicker to say that "it seems likely to have achieved nearly species rank." (Lidicker 1960)
Habitat
In most heteromyidsHeteromyidae
The family of rodents that include kangaroo rats, kangaroo mice and rock pocket mice is the Heteromyidae family. Most heteromyids live in complex burrows within the deserts and grasslands of western North America, though species within the Heteromys and Liomys genera are also found in forests and...
, soil texture is a primary factor in determining species distributions. (Brown and Harney, 1993)
The range of D. m. parvus is isolated from members of D. m. merriami at the northernmost extent of their range by 8-13 kilometers (km) (5–8 miles (mi)) of unsuitable habitat, indicating possible past intergradation
Intergradation
In zoology, intergradation is the way in which two distinct subspecies are connected via areas where populations are found that have the characteristics of both...
of the two subspecies.
San Bernardino Kangaroo Rats inhabit places with sandy loam
Loam
Loam is soil composed of sand, silt, and clay in relatively even concentration . Loam soils generally contain more nutrients and humus than sandy soils, have better infiltration and drainage than silty soils, and are easier to till than clay soils...
substrates, characteristic of alluvial fans and flood plains, where they are able to dig small, simple burrows. Plantlife in such areas is typically dominated by chaparral
Chaparral
Chaparral is a shrubland or heathland plant community found primarily in the U.S. state of California and in the northern portion of the Baja California peninsula, Mexico...
and sage scrub. These alluvial scrub habitats can be classified as pioneer, intermediate, and mature, in order of decreased frequency of flooding and increased density of plants. Of these subsections of this particular habitat, D. m. parvus is most populous in intermediate alluvial scrub.
D. m. parvus is found unequally distributed between seven isolated locations. The four smallest remnant populations reside near City Creek, Etiwanda
Etiwanda, Rancho Cucamonga, California
Etiwanda is the easternmost of three formerly unincorporated communities that became part of Rancho Cucamonga, California, United States in 1977.-History:...
, Reche Canyon, and South Bloomington
Bloomington, California
Bloomington is an unincorporated census-designated place in San Bernardino County, California, United States. The population was 23,851 at the 2010 census, up from 19,318 at the 2000 census....
. The largest populations with the most area of suitable habitat are located near the Santa Ana River
Santa Ana River
The Santa Ana River is the largest river of Southern California in the United States. Its drainage basin spans four counties. It rises in the San Bernardino Mountains and flows past the cities of San Bernardino and Riverside, before cutting through the northern tip of the Santa Ana Mountains and...
, Lytle
Lytle Creek
Lytle Creek, California, is an approximately stream in southwestern San Bernardino County near the city of San Bernardino. It is a tributary of the Santa Ana River. The river flows through the eastern San Gabriel Mountains and has three forks, the North, Middle and South forks...
and Cajon Creek, and the San Jacinto River
San Jacinto River (California)
The San Jacinto River is a river in Riverside County, California. The river's headwaters are in San Bernardino National Forest, but the lower portion of the watershed is urban and agricultural land....
.
The historical range of D. m. parvus encompassed roughly 128,000 hectares (ha) (320,000 acres (ac)); by the 1930s the its range had been reduced to roughly 11,200 ha (28,000 ac). As of 1998, its range is approximated at only 1,299 ha (3,247 ac).
Man-made threats
According to the Fish and Wildlife Service (FWS), D. m. parvus is threatened by "habitat destructionHabitat destruction
Habitat destruction is the process in which natural habitat is rendered functionally unable to support the species present. In this process, the organisms that previously used the site are displaced or destroyed, reducing biodiversity. Habitat destruction by human activity mainly for the purpose of...
, degradation, and fragmentation
Habitat fragmentation
Habitat fragmentation as the name implies, describes the emergence of discontinuities in an organism's preferred environment , causing population fragmentation...
by sand
Sand mining
Sand mining is a practice that is becoming an environmental issue as the demand for sand increases in industry and construction. Sand is mined from beaches and inland dunes and dredged from ocean beds and river beds. It is often used in manufacturing as an abrasive, for example, and it is used to...
and gravel mining
Gravel pit
Gravel pit is the term for an open cast working for extraction of gravel. Gravel pits often lie in river valleys where the water table is high, so they may fill naturally with water to form ponds or lakes. Old, abandoned gravel pits are normally used either as nature reserves, or as amenity areas...
, flood control
Flood control
In communications, flood control is a feature of many communication protocols designed to prevent overwhelming of a destination receiver. Such controls can be implemented either in software or in hardware, and will often request that the message be resent after the receiver has finished...
projects, urban development, vandalism, and inadequate regulatory mechanisms."
While sand and gravel mining and urban development have direct impact upon the habitat, flood control projects such as dams
DAMS
Driot-Arnoux Motorsport is a racing team from France, involved in many areas of motorsports. DAMS was founded in 1988 by Jean-Paul Driot and former Formula One driver René Arnoux. It is headquartered near Le Mans, only 2 km from the Bugatti Circuit.- History :The year after its foundation,...
, levees, and berms indirectly change the habitat by preventing flooding. Curtailed flooding in these habitats will cause succession of the preferred 'intermediate' alluvial scrub habitat to 'mature' habitat, as removal and deposition of sand that would normally come with flooding has ceased. Furthermore, in areas with sufficient soil moisture, shrub densities will exceed the sparse to moderate densities where this subspecies lives. (Hanes et al. 1989, McKernan 1997)
Areas that are affected include the Santa Ana River
Santa Ana River
The Santa Ana River is the largest river of Southern California in the United States. Its drainage basin spans four counties. It rises in the San Bernardino Mountains and flows past the cities of San Bernardino and Riverside, before cutting through the northern tip of the Santa Ana Mountains and...
, Lytle
Lytle Creek
Lytle Creek, California, is an approximately stream in southwestern San Bernardino County near the city of San Bernardino. It is a tributary of the Santa Ana River. The river flows through the eastern San Gabriel Mountains and has three forks, the North, Middle and South forks...
and Cajon Creek, and the San Jacinto River
San Jacinto River (California)
The San Jacinto River is a river in Riverside County, California. The river's headwaters are in San Bernardino National Forest, but the lower portion of the watershed is urban and agricultural land....
.
Urban development, in addition to directly destroying habitat, brings with it domesticated cats
Cat
The cat , also known as the domestic cat or housecat to distinguish it from other felids and felines, is a small, usually furry, domesticated, carnivorous mammal that is valued by humans for its companionship and for its ability to hunt vermin and household pests...
, a documented predator of the San Bernardino Kangaroo Rat. The likelihood of predation increases as the interface between natural and urban habitats is increased.
Failed government regulation
The FWS notes several points of inadequate regulation at the time of publication (1998):1) Lead agencies made choices detrimental to D. m. parvus under California Environmental Quality Act and National Environmental Policy Act
Nepa
Nepa is a village development committee in Dailekh District in the Bheri Zone of western-central Nepal. At the time of the 1991 Nepal census it had a population of 3621 people living in 739 individual households.-External links:*...
,
2) California Environmental Quality Act rulings are subject to overriding social or economic decisions,
3) California's Natural Community Conservation Planning program, which is responsible for conserving alluvial scrub, is a voluntary program which San Bernardino and Riverside counties had not joined,
4) The Surface Mining Control and Reclamation Act of 1977
Surface Mining Control and Reclamation Act of 1977
The Surface Mining Control and Reclamation Act of 1977 is the primary federal law that regulates the environmental effects of coal mining in the United States....
requires that the parts of the D. m. parvus range used for mining undergo land rehabilitation
Land rehabilitation
Land rehabilitation is the process of returning the land in a given area to some degree of its former state, after some process has resulted in its damage...
; however, this will not likely have a beneficial effect on the species due to the changed topology and
hydrology,
5) The Bureau of Land Management
Bureau of Land Management
The Bureau of Land Management is an agency within the United States Department of the Interior which administers America's public lands, totaling approximately , or one-eighth of the landmass of the country. The BLM also manages of subsurface mineral estate underlying federal, state and private...
set aside three areas along the Santa Ana River for preservation of federally listed species such as D. m. parvus, the Santa Ana River Woolly Star (Eriastrum densifolium
Eriastrum densifolium
Eriastrum densifolium is a species of flowering plant in the phlox family known by the common name giant woollystar. This wildflower is native to California and Baja California where it grows in open areas such as sand dunes and dry washes. It grows on an erect stem with slightly hairy to densely...
ssp. sanctorum), the Slender-Horned Spineflower, and the California Gnatcatcher. However, these areas are also allotted for potential water conservation
Water conservation
Water conservation refers to reducing the usage of water and recycling of waste water for different purposes such as cleaning, manufacturing, and agricultural irrigation.- Water conservation :Water conservation can be defined as:...
projects such as percolation basins
Infiltration basin
An infiltration basin , is a type of best management practice that is used to manage stormwater runoff, prevent flooding and downstream erosion, and improve water quality in an adjacent river, stream, lake or bay...
, and the areas allotted for the federally listed species seldom overlap with the range of D. m. parvus.
6) Finally, the Clean Water Act
Clean Water Act
The Clean Water Act is the primary federal law in the United States governing water pollution. Commonly abbreviated as the CWA, the act established the goals of eliminating releases of high amounts of toxic substances into water, eliminating additional water pollution by 1985, and ensuring that...
does not provide for conservation of threatened animals, and while projects executed under that act require a permit from the U.S. Army Corps of Engineers, that agency has "allowed projects to proceed without their overview" within their jurisdiction.
Other threats
In addition to predationPredation
In ecology, predation describes a biological interaction where a predator feeds on its prey . Predators may or may not kill their prey prior to feeding on them, but the act of predation always results in the death of its prey and the eventual absorption of the prey's tissue through consumption...
, the isolated ranges and small populations of D. m. parvus makes increased mortality rates more likely. Reduction in habitat size and species isolation leads to population loss "greater than expected from habitat loss alone," and this trend is well documented for rodents and other vertebrates. (Soule´ et al. 1992, Andren 1994, Bolger et al. 1997)
Isolated populations, being restricted to relatively small local areas, are more subject to extirpation
Local extinction
Local extinction, also known as extirpation, is the condition of a species which ceases to exist in the chosen geographic area of study, though it still exists elsewhere...
from natural or manmade events, such as floods or drought
Drought
A drought is an extended period of months or years when a region notes a deficiency in its water supply. Generally, this occurs when a region receives consistently below average precipitation. It can have a substantial impact on the ecosystem and agriculture of the affected region...
. Due to their small population, they may also lose genetic variability
Genetic variability
Genetic variability is a measure of the tendency of individual genotypes in a population to vary from one another. Variability is different from genetic diversity, which is the amount of variation seen in a particular population. The variability of a trait describes how much that trait tends to...
and experience
inbreeding depression
Inbreeding depression
Inbreeding depression is the reduced fitness in a given population as a result of breeding of related individuals. It is often the result of a population bottleneck...
. Isolation of groups is increased by the construction of railroad tracks, roads, and flood control channels.
Extirpation
Local extinction
Local extinction, also known as extirpation, is the condition of a species which ceases to exist in the chosen geographic area of study, though it still exists elsewhere...
from flooding is becoming more likely as urban development pushes the remaining populations to the active flood plain. Due to the engineering of these allotted flood areas, the frequency and severity of flooding makes them uninhabitable. Likewise, in the areas where flooding has been diverted, the canopy density of the brush has increased beyond suitable levels for D. m. parvus.