Merriam's Kangaroo Rat
Encyclopedia
Merriam's Kangaroo Rat, Dipodomys merriami, is a species of rodent
in the family Heteromyidae
. The species name commemorates Clinton Hart Merriam
.
, Baja California
, and northern Mexico
. In San Diego County they are found in the low desert and the washes east of Laguna, Volcan, and Palomar Mountains.
Fur color varies between populations within the species' range, but the back color is generally light brown or tan. The merriami species is smaller than most of the other kangaroo rats in the southwest. Adults average about 14 inches in length. The tail is relatively long with a large tuft of hair at the tip. The tuft is thought to act like fletching
on an arrow, providing drag
to keep the animal stable during locomotion. merriami have four toes on each hind foot in contrast to the pacific kangaroo rat, Dipodomys simulans and the Stephens' kangaroo rat, Dipodomys stephensi (both kangaroo rat species also found in San Diego County), which have five toes.
, pinyon-juniper woodland
, and Joshua tree
habitat throughout the southwestern United States
and Mexico
.
Most Kangaroo rats are exclusively nocturnal. Even so, they tend to avoid being outside their burrows when the moon is full. The greater the amounts of moonlight the less time they spend collecting food, defending their territory, or searching for mates. When the amount of moonlight is great they retreat underground in order to avoid predation. In some areas, above ground activity is limited to two hours or less. During the day, they remain in their cool burrows. They often seal entranceways to their burrows with soil to prevent exposure to heat. When they are active above ground they move about within their territory and attempt to fill their cheek pouches with seeds and plant material. When their cheek pouches are full they retreat to their burrows where they disgorge the seeds they have collected. Some of the food is eaten immediately while the remainder is stored (often building a seed cache of considerable size) in several chambers within the burrow system.
Kangaroo rats lose water mainly by evaporation during gas exchange, and so have developed a behavioural adaptation to prevent this loss. As they spend a lot of time within their burrows to escape the heat of the day, the burrows become much more humid than the air outside (due to evaporative loss). When collecting seeds, they store them in the burrows rather than eating them straight away. This causes the moisture in the air to be absorbed by the seeds, and the kangaroo rat regains the water it has previously lost when it then consumes them.
)
and glossy snakes.
listed the San Bernardino kangaroo rat as endangered in 1998.
Rodent
Rodentia is an order of mammals also known as rodents, characterised by two continuously growing incisors in the upper and lower jaws which must be kept short by gnawing....
in the family Heteromyidae
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...
. The species name commemorates Clinton Hart Merriam
Clinton Hart Merriam
Clinton Hart Merriam was an American zoologist, ornithologist, entomologist and ethnographer.Known as "Hart" to his friends, Dr. Clinton Hart Merriam was born in New York City in 1855. His father, Clinton Levi Merriam, was a U.S. congressman. He studied biology and anatomy at Yale University and...
.
Range
Dipodomys merriami is found in the Upper and Lower Sonoran life zones of the southwestern United StatesSouthwestern United States
The Southwestern United States is a region defined in different ways by different sources. Broad definitions include nearly a quarter of the United States, including Arizona, California, Colorado, Nevada, New Mexico, Oklahoma, Texas and Utah...
, Baja California
Baja California
Baja California officially Estado Libre y Soberano de Baja California is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico. It is both the northernmost and westernmost state of Mexico. Before becoming a state in 1953, the area was known as the North...
, and northern Mexico
Mexico
The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...
. In San Diego County they are found in the low desert and the washes east of Laguna, Volcan, and Palomar Mountains.
Physical description
Merriam's kangaroo rats, like other kangaroo rats and pocket mice, are members of the family Heteromyidae. Each species within this family has fur-lined food storage pouches. The cheek pouch is utilized as a portable cache for food while foraging. Kangaroo rats are named for their extremely long, kangaroo-like hind feet and they are almost completely bipedal. They hop or jump rather than scurry or run. Because of this, most heteromyid rodents also have a relatively long tail that acts to counterbalance the hopping/jumping form of locomotion.Fur color varies between populations within the species' range, but the back color is generally light brown or tan. The merriami species is smaller than most of the other kangaroo rats in the southwest. Adults average about 14 inches in length. The tail is relatively long with a large tuft of hair at the tip. The tuft is thought to act like fletching
Fletching
Fletching is the aerodynamic stabilization of arrows or darts with materials such as feathers, each piece of which is referred to as a fletch. The word is related to the French word flèche, meaning "arrow," via Old French; the ultimate root is Frankish fliukka...
on an arrow, providing drag
Drag (physics)
In fluid dynamics, drag refers to forces which act on a solid object in the direction of the relative fluid flow velocity...
to keep the animal stable during locomotion. merriami have four toes on each hind foot in contrast to the pacific kangaroo rat, Dipodomys simulans and the Stephens' kangaroo rat, Dipodomys stephensi (both kangaroo rat species also found in San Diego County), which have five toes.
Habitat
Merriam's kangaroo rat can be found in desert scrub, alkali scrub, sagebrush steppeSagebrush steppe
The sagebrush steppe is a type of shrub-steppe, which is a dry-xeric environment and plant community found in the Western United States and western Canada...
, pinyon-juniper woodland
Pinyon-juniper woodland
A Pinyon-juniper woodland is a forest type characteristic of many parts the Western United States, often in higher elevations of desert ecoregions.-Locations:...
, and Joshua tree
Joshua tree
Yucca brevifolia is a plant species belonging to the genus Yucca. It is tree-like in habit, which is reflected in its common names: Joshua tree, Yucca palm, Tree yucca, and Palm tree yucca....
habitat throughout the southwestern United States
Southwestern United States
The Southwestern United States is a region defined in different ways by different sources. Broad definitions include nearly a quarter of the United States, including Arizona, California, Colorado, Nevada, New Mexico, Oklahoma, Texas and Utah...
and Mexico
Mexico
The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...
.
Behavior
Merriam's kangaroo rats live individually within a maze of underground burrows. Males and females each establish individual territories. They defend their territories against other male and female merriami, primarily to protect often scarce food resources. It is typical that they locate multiple entrances to their burrow complex at the base of shrubs near the middle of their territory. This allows more opportunities for them to escape from predators.Most Kangaroo rats are exclusively nocturnal. Even so, they tend to avoid being outside their burrows when the moon is full. The greater the amounts of moonlight the less time they spend collecting food, defending their territory, or searching for mates. When the amount of moonlight is great they retreat underground in order to avoid predation. In some areas, above ground activity is limited to two hours or less. During the day, they remain in their cool burrows. They often seal entranceways to their burrows with soil to prevent exposure to heat. When they are active above ground they move about within their territory and attempt to fill their cheek pouches with seeds and plant material. When their cheek pouches are full they retreat to their burrows where they disgorge the seeds they have collected. Some of the food is eaten immediately while the remainder is stored (often building a seed cache of considerable size) in several chambers within the burrow system.
Kangaroo rats lose water mainly by evaporation during gas exchange, and so have developed a behavioural adaptation to prevent this loss. As they spend a lot of time within their burrows to escape the heat of the day, the burrows become much more humid than the air outside (due to evaporative loss). When collecting seeds, they store them in the burrows rather than eating them straight away. This causes the moisture in the air to be absorbed by the seeds, and the kangaroo rat regains the water it has previously lost when it then consumes them.
Reproduction
Merriam's Kangaroo rats produce up to three litters per year, with an average of four pups in each litter. Weaning of young occurs 24–33 days after birth.Diet
The diet of Merriam's Kangaroo rat is almost exclusively plant seeds (they are granivorous). The bulk of their diet consists of the seeds of desert and grassland plants. They rarely drink water. Rather, they obtain water through metabolic processes augmented by the moisture content of their food. (See 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...
)
Predators
Kangaroo rats are a common prey items for many other desert animals. Typical predators of the Merriam's Kangaroo rat include barn owls, great horned owls, coyotes, foxes, badgers, bobcats, and several snake species including sidewindersSidewinders
Sidewinders is a Barbershop quartet that won the 1964 SPEBSQSA international competition....
and glossy snakes.
Conservation status
In general humans have not caused adverse impact to the Merriam's kangaroo rat through most of its range. However, in southern California one subspecies, the San Bernardino Kangaroo Rat, Dipodomys merriami parvus, is at risk due primarily to urban development including construction of dams and alteration of hydrologic regimes throughout its range. Once common on alluvial plains in the washes of San Bernardino and Riverside counties, the United States Fish and Wildlife ServiceUnited States Fish and Wildlife Service
The United States Fish and Wildlife Service is a federal government agency within the United States Department of the Interior dedicated to the management of fish, wildlife, and natural habitats...
listed the San Bernardino kangaroo rat as endangered in 1998.