Dark Kangaroo Mouse
Photo Copyright Aaron Ambos
Microdipodops megacephalus
NatureServe conservation status
Global (G-rank): G4
State (S-rank): S2
Utah Wildlife Action Plan status
- SGCN
External links
Species range
The species occurs primarily in the Great Basin ecoregion of the western United States. Its main distribution lies in Nevada and Utah, but it also occurs in small areas of California, Idaho, and Oregon (Auger and Black 2006, Hafner and Upham 2011). Within Utah, populations are restricted to Tooele, Juab, Millard, Beaver, and Iron counties.
Habitat
Little has been written regarding the habitat of this species in Utah. Reported elations range from 4,400 ft to 5,400 ft (Durrant 1952). O'Farrell and Blaustein (1974), writing of this species throughout its range, stated: "The habitat of M. megacephalus lies exclusively in the Upper Sonoran Life-zone . . .. The species is restricted to fine, gravelly soils . . .. However, near the margins of its range, it may occur in sand dunes."
Ecology
Dark kangaroo mice are nocturnal rodents that feed on small seeds and insects, carrying food in fur-lined cheek pouches and caching seeds within their burrow system (O'Farrell and Blaustein 1974). The dark kangaroo mouse inhabits stabilized dunes consisting of sparse vegetation. However, the presence of grasses, such as indian ricegrass and sand dropseed, is an integral habitat requirement for the species (HAFB, 2024). Interestingly, dark kangaroo mice acquire their water from their food and do not require a free water source.
In Utah, dark kangaroo mice often burrow amid the winding, stable interspaces of low dunes (<10 ft tall) where more coarse sand and gravel settle (HAFB, 2024). Most localities are along dune peripheries, in salt desert shrub, at the margins of historical Lake Bonneville.
Threats or limiting factors
Potential threats to the species include OHV motorized recreation, inappropriate fire frequency and intensity, and invasive wildlife. Activities such as off-trail OHV use have direct effects on the sensitive habitats of this species. Most dune areas in Utah see high recreational use, putting the settled interspaces between dunes and fragile vegetative communities at risk. Invasive plants, specifically cheatgrass, and the resulting changes in vegetative cover and fire cycle are an even greater threat to the dark kangaroo mouse. Utah studies have found that as cheatgrass increases, small mammal diversity decreases, with dark kangaroo mice among the first to disappear (Haug 2010, Freeman et al. 2014, Phillips 2018). Hafner et al (1998) also described changes in natural vegetative community structure and composition that favor other rodent populations over this species. Additional threats may include utility-scale solar energy potential and quarrying.
Taxonomy
Hall (1981) noted the similarity of the race MICRODIPODOPS MEGACEPHALUS LEUCOTIS, in several morphological characters, to a related species MICRODIPODOPS PALLIDUS but added that two other morphological characters as well as the "geographic nearness of leucotis to M. m. megacephalus [endemic to Nevada] influence me to let leucotis remain a subspecies of M. megacephalus." Hall (1981), however, further commented: "Possibly leucotis should be elevated to the rank of species." Hafner and Hafner (1983) have pointed out that "Hall's suggestion (1981:560) that M. megacephalus leucotis may warrant specific status is not supported by chromosomal or protein evidence ...." (Perhaps it was this belief of Hall's [1981], i.e., that LEUCOTIS is so taxonomically distinct and unique, that led him to map its distribution [his map 340] as disjunct from that of the rest of its species.)
It should be noted that Hall and Johnson (1938) incorrectly reported MICRODIPODOPS PALLIDUS from Millard County and claimed that this represented "an extension of the known range of [the race] albiventer [of the species MICRODIPODOPS PALLIDUS] of about 60 miles to the northward." These specimens were actually MICRODIPODOPS MEGACEPHALUS PAULULUS, and MICRODIPODOPS PALLIDUS does not, so far as is known, occur in Utah nor is that species even predicted to occur in Utah. This misidentification is indicated in the synonymy for MICRODIPODPS MEGACEPHALUS PAULULUS provided by Durrant (1952); however, Hall (1981) concealed the misidentification by conveniently omitting reference to Hall and Johnson (1938) from his synonymy (Hall 1981) for M. M. PAULULUS. Interestingly, Hall was the senior author of the descriptions of both MICRODIPODOPS MEGACEPHALUS PAULULUS and MICRODIPODOPS PALLIDUS ALBIVENTER, even though his report with Johnson (1938) reveals that he could not always identify these taxa he had named.