Merriam’s Kangaroo Rat, Dipodomys simulans

Merriam’s Kangaroo Rat, Dipodomys simulans. Photograph taken in the greater Bahía de los Ángeles, Baja Calfornia, November 2019. Photograph courtesy of George Flicker, Bahía de los Ángeles, Baja California Identification courtesy of Mary & George Flicker, Bahía de los Ángeles.

Merriam’s Kangaroo Rat, Dipodomys merriami, is a member of the Heteromyidae family of Pocket Mice, Kangaroo Mice, and Kangaroo Rats. The Heteromyidae family consists of fifty-nine members placed in six genera. The Dipodomys genus consists of twenty-three species.  Merriam’s Kangaroo Rat is known in Mexico as Las Ratas Canguro de Merriam and Rata Congaro Merriam.

Merriam’s Kangaroo Rats are sandy brown in color with white underbellies. They are small in size, being 10 cm (3.9 inches) in snout-to-vent length and 23 cm (9.1 inches) in total length.  They have large heads with big black eyes and small ears. They are named after their extremely long, Kangaroo-like hind feet. Unlike other species of Kangaroo Rats, they have four toes on each hind foot instead of five. They hop or jump, rather than scurrying or running, and are almost completely bipedal. They have a long tail with a large tuft of dark hair at the tip. This tuft acts like fletching on an arrow and provides drag to keep them stable during locomotion. Like other Kangaroo Rats and Pocket Mice, they have fur-lined food storage pouches in their cheeks. These pouches are used as a portable cache for food while foraging.  

Merriam’s Kangaroo Rats are solitary and primarily nocturnal, remaining in their burrows during the day. Their burrows consist of a maze of underground tunnels, often constructed near the base of a shrub or bush. Typically, Merriam’s Kangaroo Rats will create several entrances to their burrow complex near the middle of their territory, allowing more opportunities to escape from predators. Burrow entrances are often sealed with soil to prevent exposure to heat. Only one adult occupies each burrow, and both males and females each establish individual territories. They defend their territories against one another, primarily to protect food resources. While Mirriam’s Kangaroo Rats are nocturnal, they will avoid leaving their burrows when the moon is full. The greater amounts of moonlight, the more likely they are to be spotted by a predator. When the amount of moonlight becomes too bright, they will retreat underground. When they are active above ground, they forage within their territories and attempt to fill their cheek pouches with seeds and plant material. Once their pouches are full, they return to their burrows where they disgorge the food they have collected. Some food is consumed immediately, while the remainder is stored in several chambers within their burrow system. Little is known about the mating system and reproductive habits of Merriam’s Kangaroo Rats. Their breeding season occurs from January through August, and gestation lasts for 28 to 32 days. Females produce up to three litters per year, with an average of four young per litter. The young are altricial, being born blind and without hair. They are weaned 24 to 33 days after birth and reach sexual maturity between 60 to 84 days. Merriam’s Kangaroo Rats have life spans of up to five years in the wild.

Merriam’s Kangaroo Rats are granivores and their diet is almost exclusively plant seeds. They feed primarily on the seeds of Creosote Bush, Grama Grass, Mesquite, Ocotillo, and Purslane. Their diet varies seasonally with the availability of local plants and they consume more green vegetation in mid-summer. Occasionally, they will supplement their diet with some insects. They rarely drink water, rather, they obtain water through metabolic processes augmented by the moisture content of their food. Merriam’s Kangaroo Rat is a common prey item for many desert animals including Barn and Great Horned Owls, Badgers, Bobcats, Coyotes, Foxes, and several snake species. In their defense, Merriam’s Kangaroo rats have excellent hearing and can even detect the sound of an owl approaching. Their large hind legs also enable them to jump up to 2.75 m (9 feet) in order to escape predators. Additionally, they are known to kick sand in the face of a predator. 

Merriam’s Kangaroo Rat may be confused with the other twenty-two species of Kangaroo Rats found in the Dipodomys genus but the Merriam’s Kangaroo Rat is the only species that has a dark tuft of fur on its tail.

From a conservation perspective, Merriam’s Kangaroo Rat is considered to be of Least Concern due to their wide distribution and presumed large population size. No major threats have been identified for this species. Habitat loss due to rapid expansion of coastal metropolitan areas in California threatens two subspecies,  Dipodomys merriami collinus and Dipodomys merriami parvus.