Subfamily Gerbillinae
gerbils, jirds, and relatives

Gerbillinae, otherwise known as the gerbils, jirds, and relatives, is a large Old World murid subfamily. This subfamily is one of the most well-defined in Muroidea. Its members have much in common; most being diurnal, saltatorial desert rodents. There are 103 gerbilline species in 16 genera. (Musser and Carleton, 2005)

Gerbillines are Old World rodents. They are distributed throughout Africa and the Middle East, through central Asia including much of India, to eastern Mongolia. (Carleton and Musser, 1984)

Most gerbillines live in dry, open habitats with sparse vegetation, including deserts, sandy plains, mountain slopes, steppes, grasslands, and savannahs. Some species also inhabit moist woodlands, agricultural fields, and mountain valleys. (Carleton and Musser, 1984; Nowak, 1999)

The subfamily Gerbillinae has been shuffled back and forth between the families Muridae (Alston 1876, Thomas 1896, Ellerman 1941, Carleton and Musser 1984, Musser and Carleton 1993) and Cricetidae (Miller and Gidley 1918, Simpson 1945) over the years, and has even been elevated to family status in some cases (Tullberg 1899, Chaline et al. 1977). Phylogenetic analyses based on the LCAT and vWF genes (Michaux et al. 2001) and nuclear IRBP sequences (Jansa and Weksler 2004) have shown that the genera consituting Gerbillinae form a monophyletic group sister to Deomyinae, hence, the placement of Gerbillinae in the family Muridae. Steppan et al. (2004) have corroborated this result with a phylogeny based on the GHR, BRCA1, RAG1, and c-myc genes, and they have estimated that deomyines and gerbillines diverged between 16.4 and 20 million years ago.

Because gerbillines form a well-defined group, there has been little argument over which species belong in the subfamily, and the number of genera has remain fairly consistent over the years (Carleton and Musser 1984, Musser and Carleton 1993). (Alston, 1876; Carleton and Musser, 1984; Chaline, Mein, and Petter, 1977; Ellerman, 1941; Jansa and Weksler, 2004; Michaux, Reyes, and Catzeflis, 2001; Miller and Gidley, 1918; Musser and Carleton, 1993; Simpson, 1945; Steppan, Adkins, and Anderson, 2004; Thomas, 1896; Tullberg, 1899)

Gerbillines are small to medium-sized rodents. They range in length from 50 to 200 mm, with tails measuring 56 to 245 mm. They weigh between 10 and 227 grams. Gerbillines vary in the amount to which they are sexually dimorphic; even within a species males may be heavier than females in one population and the sexes may be the same size in another population (Sinai et al. 2003). Most gerbillines have well-furred, long tails and are modified for saltatorial locomotion, with long, narrow hind feet. Some species are cursorial. Gerbillines are generally slender animals with long claws. They may have long or short ears. Their pelage is long, thick, and soft or short and harsh. Some have tufted tips on their tails. Fur color varies widely, and may be reddish, mouse gray, yellowish, clay-colored, olive, dark brown, orangish, sandy buff, or pinkish cinnamon on the dorsal surface. The underparts are generally paler shades of gray, cream, or white. Some species have whitish spots on their heads, especially behind the ears.

The gerbilline dental formula is 1/1, 0/0, 0/0, 3/3 = 16, except for the genus Desmodilliscus, which only has two lower molars on each side. The layers of enamel on the incisors are very thin compared to other muroid rodents. The molars are rooted, with lophate, planar, or prismatic enamel patterns. The coronoid process is very small or absent. Gerbillines have 12 thoracic vertebrae and seven lumbar vertebrae. Females have three or four pairs of mammae. The stomach consists of just a single chamber. There are no supraorbital or mandibular branches of the stapedial artery, and instead, the infraorbital artery supplies blood to the orbits. Gerbillines have diploid chromosome numbers between 18 and 74. (Carleton and Musser, 1984; Nowak, 1999; Sinai et al., 2003)

Most gerbillines do not live longer than three or four months in the wild. In captivity, some gerbillines have been known to live as long as eight years. (Nowak, 1999)

Gerbillines are terrestrial and most are saltatorial. Some species are capable of remarkable leaps of up to 3.5 meters. Other species locomote cursorially on all fours. Those that live in rocky habitats are often good climbers. For the most part, gerbillines are diurnal rodents, but some species are nocturnal, crepuscular, or active both day and night. Gerbillines build burrows, which may be simple structures with just one entrance and nest chamber, or elaborate networks of tunnels with multiple entrances and chambers for nesting, food storage, and excrement. Gerbillines take dust baths to keep their silky coats in good condition.

Some gerbilline species are solitary, aggressive, and territorial, with each individual inhabiting its own burrow. Other species are highly gregarious and form large colonies, with many individuals inhabiting tunnel networks tens of meters long and two or three meters deep. Still others live in small family groups, and each family group defends its own territory. There is much socializing among some gerbillines while they are in the nest. The pups groom one another, chase each other, and play-fight when they are between 18 and 35 days old.

Gerbillines are mainly sedentary, though the young may go through a nomadic period until they are able to establish permanent home ranges, and some species migrate in times of drought. Gerbillines do not hibernate or aestivate, but in some areas they experience long bouts of torpor in the winter and remain in their burrows living off of stored food for months at a time. (Carleton and Musser, 1984; Dempster and Perrin, 1989; Hubbard, 1972; Nowak, 1999)

Gerbillines have large eyes and good vision. They also use auditory, chemical, and tactile cues in perceiving their environment.

Gerbils have a range of vocalizations that they use to communicate with one another. Young gerbils squeak when their mother enters the nest, grunt when they are resting together or climbing on one another, and they also make a clicking noise. Adult gerbils squeak and sometimes produce a high-pitched rattle. They also are known to drum their hind feet on the ground. Gerbillines communicate with one another through chemical means, as well, using pheromones to signal reproductive and social status. Male gerbillines communicate territory ownership by scent-marking with their large ventral sebaceous glands. (Carleton and Musser, 1984; Dempster and Perrin, 1989; Nowak, 1999)

Gerbillines are primarily herbivorous or omnivorous, consuming nuts, seeds, roots, bulbs, fruits, grasses, insects, bird eggs and nestlings, and even others of their own species. Gerbillines store large quantities of plant food in their burrows--sometimes as much as 60 kg. (Nowak, 1999)

Gerbillines are preyed upon by various snakes, owls, and small mammalian carnivores. To discourage predators from entering their burrows, some gerbillines keep the entrances blocked with sand. Others incorporate bolt holes into their burrow systems, into which they can make a hasty retreat if caught out in the open. In addition, gerbillines usually have neutral-colored fur, which no doubt helps them blend in to their sandy or rocky background. (Carleton and Musser, 1984; Nowak, 1999)

Gerbillines are primary and secondary consumers, and they are food for a number of higher-level consumers. They are also pollinators of certain plants (Johnson et al. 2001), and probably have a role in seed dispersal. Gerbillines are parasitized by several flea species, such as Xenopsylla debilis, Xenopsylla humilis, and Xenopsylla difficilis. (Hubbard, 1972; Johnson, Pauw, and Midgley, 2001)

Some gerbillines are considered pest animals in their native ranges, because they destroy crops, damage embankments and irrigation systems with their digging, and spread bubonic plague. There is also concern that captive gerbils may escape and establish feral populations, which could outcompete native rodents. (Nowak, 1999)

Gerbillines, especially Meriones unguiculatus, are clean, easy to take care of, and breed readily in captivity. For these reasons, they are used in many laboratories for medical, physiological, and psychological research. They are also popular pets. Other gerbilline species are trapped for their skins. (Nowak, 1999)

Currently, 35 gerbilline species are on the IUCN's Red List of Threatened Species. This includes one critically endangered species (Cheng's jirds, Meriones chengi), four endangered species (Arabian jirds, Meriones arimalius, Dahl's jirds, Meriones dahli, Buxton's jirds, Meriones sacramenti, and Zarudny's jirds, Meriones zarudnyi), two vulnerable species (western gerbils, Gerbillus hesperinus, and Allenby's gerbils, Gerbillus andersoni allenbyi), one near threatened species (Hoogstral's gerbils, Gerbillus hoogstraali), one lower risk species (large Aden gerbils, Gerbillus poecilops), and 26 species that lack data. Research efforts are needed to establish the status of those species for which little is known. (IUCN, 2004)