Dipodomys nitratoides Merriam 1894
Creators: name: Don E. Wilson
name: Thomas E. Lacher, Jr
name: Russell A. Mittermeier
Publisher: name: Lynx Edicions
Year: 2016
Subjects: Biodiversity
Taxonomy
Animalia
Chordata
Mammalia
Rodentia
Heteromyidae
Dipodomys
Dipodomys nitratoides

description: 63.
San Joaquin Kangaroo Rat
Dipodomys nitratoides
French: Rat-kangourou du San Joaquin / German: San-Joaquin-Kangururatte / Spanish: Rata canguro de San Joaquin
Other common names: San Joaquin Valley Kangaroo Rat; Fresno Kangaroo Rat (exilis), Short-nosed Kangaroo Rat (brevinasus), Tipton Kangaroo Rat (nitratoides)
Taxonomy. Dipodomys nitratoides Merriam, 1894,
Tipton, San Joaquin Valley, Tulare Co., California, USA.
Based on molecular sequence analyses, D. nitratoides is a member of the merriami species group along with D. merriami, which it closely resembles. The two species occupy the San Joaquin Valley and Mojave deserts (respectively) on either side of the Tehachapi Mountains. Three subspecies recognized.
Subspecies and Distribution.
D.n.nitratoidesMerriam,1894—SWUSA(flooroftheSanJoaquinValley,SCCali-fornia).
D.n.brevinasusGrinnell,1920—SWUSA(W&EedgesoftheSanJoaquinValley,Pano-cheValley,CarrizoPlain,andupperCuyamaValley,SCCalifornia).
D. n. exilis Merriam, 1894 — SW USA (a limited distribution on the floor of the N San Joaquin Valley, SC California).
Descriptive notes. Head-body 74-112 mm, tail mean 141 mm (males) and 137 mm (females), ear mean 12 mm, hindfoot mean 35 mm; weight 40-53 g. Male San Joaquin Kangaroo Rats are slightly larger than females. Tail is ¢.142% of head-body length. This is one of the smallest kangaroo rats, with four toes on hindfeet. Upper parts are fulvous or clay colored;tail is bicolored, with dull brownish-black crest and tuft. Chromosomal complement has 2n = 54 and FN = 104. The San Joaquin Valley Kangaroo Rat is generally smaller, with shorter and thinner rostrum, than Merriam’s Kangaroo Rat (D. merniama).
Habitat. Arid, alkali-sink plains, sparsely vegetated with grass and, in places, saltbush (Atriplex, Amaranthaceae) and either Mormon tea (Ephedra, Ephedraceae, in the Panoche Valley) or more xerophylic shrubs (San Joaquin Valley). Populations of San Joaquin Kangaroo Rats historically occurred at elevations of 50-800 m. It is likely that river and marsh systems of the San Joaquin Valley floor formed filter-barriers between the three subspecies. Today, much of the critical alkali-sink habitat has disappeared due to agricultural and petroleum development. Dominant shrubs in this habitat include several amaranth family species such as iodine bush (Allenrolfea occidentalis), common glasswort (Salicornia subterminalis), and shrubby seablite (Suaeda fruticosa). Burrows of San Joaquin Kangaroo Rats are usually located at the base of a low bush and runways often run through grass from burrow to neighboring clumps of vegetation. Burrow openings, even when in use, may show no evidence of activity for long periods of time. Other rodents co-occurring with the San Joaquin Kangaroo Rat include the California Ground Squirrel (Otospermophilus beecheyi), Nelson’s Antelope Squirrel (Ammospermophilus nelsoni), Botta’s Pocket Gopher (Thomomys bottae), the San Joaquin Pocket Mouse (Perognathus inornatus), the Giant Kangaroo Rat (D. ingens), the Southern Grasshopper Mouse (Onychomys torridus), the North American Deermouse (Peromyscus maniculatus), and the Western Harvest Mouse (Reithrodontomys megalotis).
Food and Feeding. Diet of the San Joaquin Kangaroo Rat contains seeds of forbs, grasses, and shrubs, including saltbush (Atriplex, Amaranthaceae). Green vegetation (in the spring) and insects are also eaten.
Breeding. Breeding season of the San Joaquin Kangaroo Rat primarily occurs in December—August, with a peak in April. Averagelittersize is two young (range 1-3).
Activity patterns. Although experiments indicate that San Joaquin Kangaroo Rats are excellent swimmers, they are notably averse to getting wet.
Movements, Home range and Social organization. Male and female San Joaquin Kangaroo Rats defend non-overlapping home ranges of ¢.0-05 ha. Reported densities are 5-20 ind/ha, but populations periodically increase to high levels and decline rapidly due to long-term drought, excessive precipitation, flooding, or other factors. Sometimes these fluctuations lead to local extirpations, and habitat fragmentation has prevented recolonization in many cases.
Status and Conservation. Classified as Vulnerable on The IUCN Red List. Populations of San Joaquin Kangaroo Rats have been fragmented and extirpated by agricultural development, urbanization, invasion of exotic grasses, and rodenticides. The US Fish and Wildlife Service list subspecies exilis and nitratoides as endangered; most occurrences in protected areas are of the unlisted subspecies, brevinasus.
Bibliography. Alexander & Riddle (2005), Best (1991, 1993a, 1999¢), Chesemore & Rhodehamel (1992), Eisenberg (1963, 1993), Hall (1981), Ingles (1954), Johnson & Clifton (1992), Jones (1993), Linzey & NatureServe (Hammerson & Williams) (2008), Patton & Rogers (1993), Williams et al. (1993).
description: Published as part of Don E. Wilson, Thomas E. Lacher, Jr & Russell A. Mittermeier, 2016, Heteromyidae, pp. 170-233 in Handbook of the Mammals of the World – Volume 6 Lagomorphs and Rodents I, Barcelona :Lynx Edicions on page 231, DOI: 10.5281/zenodo.6611160