Class Mammalia
Order Rodentia
Family Heteromyidae
Dipodomys sp.—Kangaroo Rats // Dipodomys small—Small Kangaroo Rat // Dipodomys gidleyi—Gidley's Kangaroo Rat // Dipodomys hibbardi—Hibbard's Kangaroo Rat // Dipodomys merriami—Merriam's Kangaroo Rat // Dipodomys merriami/ordii—Merriam's or Ord's Kangaroo Rat // Dipodomys ordii —Ord's Kangaroo Rat // Dipodomys spectabilis—Banner-tailed Kangaroo Rat
Kangaroo rats received their name because of similarities of locomotion and the morphology that goes with it between these rodents and the marsupials. The hind limbs are massively developed for the size of the animal and the forelimbs diminutive. Other characteristics include huge feet, a very long tail for balance, and an oversized head, thanks to the greatly enlarged bullae.
Kangaroo rats tend to forage in open spaces, using their paws to stuff seeds into the cheek pouches and, with the food safely stored, then retreating to cover. While in the open, they are subject to predation, especially from owls. Owls have feathers adapted for silent flight, but checking their dive upon potential food produces a low frequency sound. This sound apparently is not detected by most rodents. However, laboratory studies indicate that the large bullae of kangaroo rats are specifically adapted to pick up the slight sound made a split second before the rat is in the grip of the owl's talons. In that brief window of time, the rat undertakes a panic jump that may (or may not) save it. Since kangaroo remains tend to be plentiful in owl pellets, it can be assumed that selective pressure for this hearing is strong.
Presence of kangaroo rats in our region is taken to indicate presence of open areas basically free of vegetation (though with bushes or other vegetation nearby for cover).
D. merriami and D. ordii are similar in size (though D. ordii is a bit larger) and may end up identified merely as "Dipodomys" or as "Dipodomys small" (to separate them from D. spectabilis, which is large enough as an adult to be identified by size alone). Identifications to modern species may break down in early sites, since extinct or extralimital species may be present.
Kangaroo rats construct burrows for protection, usually with several openings to the burrow system. As with their relatives, the pocket gophers, they tend to be antisocial except during the breeding season, but two or three species may occur sympatrically.
Dalquest and Stangl (1984b) found that the lower incisor breadth is greater than 1.0 mm in D. spectabilis, 0.8 to 0.95 mm in D. ordii, and less than 0.8 mm in D. merriami. They also found that the alveolar toothrow length would separate the three species, with toothrows of D. spectabilis greater than 5.6 mm, those of D. ordii 4.8-5.5 mm, and those of D. merriami less than 4.75 mm. The incisor breadth is most useful, since the posterior rim of bone adjacent to the alveolus of m3 often is broken away in fossils.
Literature. Dalquest and Stangl 1984b.
Sites.
Identification only to the generic level likely means that the record is based on material that cannot be identified to a lower taxonomic level or that the species has not been recorded in the literature.
Sites.
Latest Blancan: Caballo (Morgan et al. 2011); La Union (Morgan and Lucas 2003).
Mid Wisconsin: Screaming Neotoma Cave (Glennon 1994).
Late Wisconsin: New Water Mountains (Mead et al. 2005).
Mid/Late Wisconsin: Rampart Cave (Lindsay and Tessman 1974).
Late Wisconsin: New Water Mountains (Mead et al. 1983).
Late Wisconsin/Holocene: Conkling Cavern (Harris 1993c).
Literature. Glennon 1994; Harris 1993c; Lindsay and Tessman 1974; Mead et al. 1983; Mead et al. 2005; Morgan and Lucas 2003; Morgan et al. 2011.
As noted above, presumably either D. merriami or D. ordii is represented.
Sites.
Early/Early-Mid Wisconsin: Rm Vanishing Floor; Sabertooth Camel Maze (Harris 1993c).
Literature. Harris 1993c.
Sites.
Late Blancan: 111 Ranch (Morgan and White 2005); Curtis Ranch (Morgan and White 2005).
Literature. Morgan and White 2005.
Dipodomys hibbardi was described by Zakrzewski (1981) as approximately evolutionarily intermediate between Prodipodomys and the living Dipodomys compactus, with shorter dentine tracts than the living form, but higher than in Prodipodomys. He also pointed out that root development was intermediate.
Sites.
Late Blancan: 111 Ranch (Morgan and White 2005); San Simon Fauna (Morgan and White 2005).
Literature. Morgan and White 2005; Zakrzewski 1981.
Merriam's Kangaroo Rat is an arid-land species essentially limited to Lower Sonoran habitats. It tends to prefer firmer soils than Ord's Kangaroo Rat. However, there may be overlap in habitat usage, and at times both of these smaller species may be taken in the same trap line.
Aside from the discriminatory
measurements recorded in the generic account, the auditory bullae tend to be somewhat
differently developed than in D. ordii. This and other subtle differences can be
seen in Fig. 1.
Fig. 1. Comparison of the skulls of D. merriami (left) and D. ordii. Scale is in mm.
Although reported from the Isleta Caves (1993c), it does not seem to be vouchered and is rejected.
Sites.
Mid Wisconsin: Castle Mountains (Mead et al. 2005).
Late Wisconsin: Murray Springs (Mead et al. 2005); Wellton Hills (Mead et al. 2005: cf.); Wolcott Peak (Mead et al. 2005).
Late Wisconsin/Holocene: Fowlkes Cave (Dalquest and Stangl 1984b); Howell's Ridge Cave (Harris 1993c); Pendejo Cave (Harris 2003)
Late Wisconsin/Holocene: Isleta Caves (Harris 1993c), rejected.
Literature. Dalquest and Stangl 1984b; Harris 1993c, 2003; Mead et al. 2005.
The material on which the following records are based are of a nature not allowing discrimination between the two species.
Sites.
Mid Wisconsin: Tank Trap Wash (Van Devender et al. 1987).
Mid/Late Wisconsin/Holocene: Sierra Diablo Cave (UTEP).
Late Wisconsin: Algerita Blossom Cave (Harris 1993c); Balcony Room (UTEP); Dry Cave <13 ka (Harris 1993c); Navar Ranch (Van Devender et al. 1987); Pendejo Cave (Harris 2003); Picacho Peak (Van Devender et al. 1991); Steeruwitz Hills #1(3) (Van Devender and Bradley 1990).
Wisconsin/Holocene: Isleta Cave No. 2 (UTEP).
Literature. Harris 1993c, 2003; Van Devender and Bradley 1990; Van Devender et al. 1987, 1991.
Unlike D. merriami, which has a southern distribution, D. ordii ranges in the West from southern Canada deep into Mexico. It prefers sandy soils, but may occur in various aspects of grassland and shrubby habitats. It only marginally ranges as high as woodland.
Synonyms. Perodipus montanus.
Sites.
Early/Early-Mid Wisconsin: Lost Valley (Harris 1993c).
Mid Wisconsin: Pendejo Cave (Harris 2003).
Late Wisconsin: Blackwater Loc. No. 1 (Morgan and Lucas 2005); Charlies Parlor (Harris 1993c: cf.); Human Corridor (Harris 1993c: cf.); U-Bar Cave (Harris 1993c: cf.).
Late Wisconsin/Holocene: Burnet Cave (Schultz and Howard 1935; Fowlkes Cave (Dalquest and Stangl 1984b); Howell's Ridge Cave (Harris 1993c); Pendejo Cave (Harris 2003); Sheep Camp Shelter (Harris 1993c).
Late Wisconsin/Holocene: Isleta Cave No. 1 (Harris 1993c) Rejected
Literature. Dalquest and Stangl 1984b; Harris 1993c, 2003; Morgan and Lucas 2005; Schultz and Howard 1935.
The Banner-tailed Kangaroo Rat is
enough larger than D. merriami and D. ordii as to usually be identifiable
on size alone. The current northern limits of distribution is near the Four-corners
area of New Mexico.
Fig. 1. Approximate distribution of the taxon in the eastern part of our region. The heavy line shows the approximate limits of the present-day Chihuahuan Desert.
This is primarily a grassland and desert-grassland animal that extends into desert. However, its widespread occurrence in late Wisconsin times suggests a wider ecological niche than is apparent today. It generally builds a large (6 ± ft diameter) mound of dirt with several burrow entrances.
Fig. 2. Dipodomys spectabilis. Fig. 3. Mound of Dipodomys spectabilis. Figs. 2 and 3 after Bailey (1931).
Sites.
Early/Early-Mid Wisconsin: Lost Valley (Harris 1993c).
Mid Wisconsin: Pendejo Cave (Harris 2003); Tank Trap Wash (Van Devender et al. 1987); U-Bar Cave (Harris 1987: cf.).
Mid/Late Wisconsin: Animal Fair (Harris 1993c); Dark Canyon Cave (Tebedge 1988); Navar Ranch (Van Devender et al. 1987).
Mid/Late Wisconsin/Holocene: Sierra Diablo Cave (UTEP).
Late Wisconsin: Algerita Blossom Cave (Harris 1993c); Balcony Room (UTEP); Bison Chamber (Harris 1970a); Dust Cave (Harris and Hearst 2012); Human Corridor (Harris 1993c); Pendejo Cave (Harris 1993c); TT II (Harris 1993c); Pendejo Cave (Harris 2003); U-Bar Cave 13-14 ka (Harris 1989); cf.); U-Bar Cave 14-15 ka (Harris 1989); U-Bar Cave 15-18 ka (Harris 1989; cf.); U-Bar Cave 18-20 ka (Harris 1989: cf.).
Late Wisconsin/Holocene: Beyond Bison Chamber (Harris 1970a); Conkling Cavern (UTEP); Deadman Cave (Mead et al. 1984); Fowlkes Cave (Dalquest and Stangl 1984b); Howell's Ridge Cave (Harris 1993c); Isleta Cave No. 1 (UTEP); Pendejo Cave (Harris 2003).
Holocene:Isleta Cave No. 2 (Harris 1993c), reject as Holocene.
Literature. Bailey 1931; Dalquest and Stangl 1984b; Harris 1970a, 1987, 1989, 1993c, 2003; Harris and Hearst 2012; Mead et al. 1984; Tebedge 1988; Van Devender et al. 1987.
Last Update: 7 Mar 2013