Table 1.

Summary of morphological, physiological, and ecological characteristics that differ between populations of desert tortoises from the Mojave and Sonoran deserts.

Character	Mojave Desert	Sonoran Desert	Reference
Morphology-shell shape
Width of shell at mid-bridge	significantly wider shell		Germano 1993
Length of gular scutes	Significantly longer gular scutes		Germano1993
		Significantly shorter length of projection of anal scutes	Germano 1993
General shape of shell	California: box-like, high-domed; Utah: box-like, low-domed, shorter plastron	Flatter, pear-shaped	Weinstein and Berry 1989
Geographical distribution	North and west of the Colorado River	South and east of the Colorado River
Habitats occupied Topography	Predominantly valleys and alluvial fans	Predominantly slopes and rocky hillsides	U.S. Dept. of the Interior, Fish and Wildlife Service 1994; Van Devender 2002
Vegetation types	Mojave Desert: Saltbush scrub, creosote bush scrub, desert scrub, tree yucca woodland	Sonoran Desert: Arizona upland, thornscrub, desert grassland	U.S. Dept. of the Interior, Fish and Wildlife Service 1994, 2010b; Van Devender 2002
Egg production
Mid-line carapace length (mm MCL) at first reproduction	176 (Germano), 178 (Turner et al. 1987)	220	Turner et al. 1984, 1986, 1987; Germano 1994b; Henen 1994; Averill-Murray 2002, Averill-Murray et al. 2002, Curtin et al. 2009
Oviposition time (range)	April to mid-July	Early June to early August	Turner et al. 1986; Averill-Murray et al. 2002
Number of clutches/yr	0–3	0–1	Turner et al. 1986; Averill-Murray et al. 2002
Number of eggs per year	5–16	1–12, avg. ~5	Turner et al. 1986, 1987; Henen 1994; Karl 1998; Mueller et al. 1998; Wallis et al. 1999
Proportion of females ovipositing/yr	0.67–1.0; typically 1.0	0.36–0.80; typically < 1, based on one study (Averill-Murray)	Turner et al. 1986; Henen 1997; Mueller et al. 1998; Wallis et al. 1999; Averill-Murray 2002