Common Names in English:
Southern Grasshopper Mouse
The southern grasshopper mouse rangewide is found in low arid
and semi-scrub vegetation (Frank and Heske 1992; McCarty 1975) and
ramona known from the MSHCP planning area is found in grasslands
and sparse coastal sage scrub habitats. They nest
in burrows, and
while they may dig their own burrows in sandy or other friable
they often use burrows dug by other rodents such as pocket
) and kangaroo rats
(Dipodomys spp.) (Baily and Sperry
1929; Stapp 1997). Specific habitat
requirements of the southern
grasshopper mouse generally are unknown, but Stapp (1997) found that
grasshopper mice use open areas and microhabitats
dominated by gopher
mounds and burrows. Stapp suggests that grasshopper mice selected
these microhabitats because of greater prey
using burrows for refuge), greater mobility in open areas, and dust
Two of the three precision level 1 data points for the grasshopper mouse in the MSHCP planning area are located in non-native grassland habitat between Lake Skinner and Diamond Valley Lake, and the other is located in Riversidean sage scrub in the same area. Likewise, in the San Felipe Valley of northern San Diego County, the grasshopper mouse was trapped in non-native grassland/ruderal habitat (P. Behrends, pers. obs. 1992). Ten of the other less precise data points for the MSHCP data base occur in natural habitat areas mapped as chaparral (3 points), Riversidean sage scrub (2 points) and non-native grassland (5 points).
Typically found at an altitude of 0 to 964 meters (0 to 3,163 feet).
communities (Hafner et al. 1998). (Ref.
List of Habitats : 4.5 Grassland - Subtropical/Tropical Dry
Studies of diet
agree that the majority of the southern grasshopper’s
diet consists of arthropods
(the phylum Arthropoda includes crustaceans,
insects, centipedes, millipedes, and arachnids) (Baily and Sperry
1929; Horner et al.
1965; McCarty 1975; Stapp 1997). For example,
Stapp (1997) found that 85% of the mouse’s diet was comprised of
remains were found in only 7% of fecal samples
The species account prepared by McCarty (1975) reported that the
grasshopper mouse’s diet is composed almost entirely of arthropods,
with beetles, scorpions, and grasshoppers as the primary
also little pocket
mice (Perognathus longimembris) and harvest
(Reithrodontomys megalotis), two very small rodent species of 7-10
g body weight
. Baily and Sperry (1929) reported a somewhat broader
diet: insects; rodents, including kangaroo rats
pocket mice (Chaetodipus spp.
and Perognathus spp.), deer mice and
white-footed mice (Peromyscus spp,); and seeds and herbaceous materials
The grasshopper mouse is an active
, and most of its prey
(Horner et al. 1965). Prey are stalked
rushed and seized and typically killed with a bite
in the head
As described above, Stapp (1997) examined habitat selection in relation to prey availability and suggested that grasshopper mice select microhabitats with gopher mounds and other rodent burrows that appear to attract insect prey. According to the species account prepared by McCarty (1975), prey items may be consumed in the burrow and other foods may be cached for later consumption .
The timing of breeding probably varies geographically and in relation
to environmental conditions
, but the peak breeding season
through July (McCarty 1975). Frank and Heske (1992) documented breeding
from early spring
to late autumn in southeastern Arizona. McCarty
(1975) reported litter sizes
of 1-6 pups
, with a mean litter size
of 2.6 and Baily and Sperry (1929) reported litter sizes of 3-5 pups.
is 27-30 days and the typical interval between litters
is 27-35 days. Grasshopper mice exhibit
up to 12 litters in a year (McCarty 1975). Grasshopper mice
are sexually mature
at an early age and females born in April can
produce two or three litters their first year. Females born late
in the year may have as many as six litters the following breeding
. Ovulation is physiologically possible by 42 days of age,
with females’ first litters appearing at 4-5 months of age. Males
begin producing sperm
by 40 days of age. Fecundity
(the measure of
reproductive output) declines rapidly after the first year, and females
are seldom reproductive after their second year (McCarty 1975). Their
appears to be polygynous
(males mating with more than
one female ) or promiscuous (both males and females having several
mates), and there is no apparent sexual dimorphism in the species
(Frank and Heske 1992). Interestingly, there appears to be both some
male-female pairing in the breeding season, and both sexes care for
offspring (McCarty 1975; McCarty and Southwick 1977), a behavioral
usually associated with monogamous species. (It is possible
to have both polygynous or promiscuous mating and male-female pairing
care. For example, recent studies have shown that
many supposedly monogamous bird species exhibit extrapair matings
and broods and litters [in mammals] may have multiple
Dispersal : There is very little information about dispersal in grasshopper mice. Stapp (1997) reported that most juveniles had disappeared from the study site by autumn, but no distinction was made between mortality and dispersal.
Daily Activity: Grasshopper mice primarily are nocturnal
Sperry 1929; Frank and Heske 1992; McCarty 1975) and peak nocturnal
activity is between 2000 and 2400 hours (8-12 p.m.
) (Frank and Heske
1992). Grasshopper mice appear to be active
on the surface all year
and there is no evidence of hibernation (McCarty 1975).
Survival: Year-to-year survival appears to be low in the grasshopper mouse and juvenile mortality and/or dispersal appears to be very high. Thus, overall population turnover in the species appears to be very rapid For example, Stapp (1997) found 100% population turnover both years in a two-year study. In addition, most juveniles appearing after mid-spring had died or dispersed by autumn. McCarty (1975) concluded that while adults may live at least three years in captivity, they probably live less than 12 months in the field . This apparent high level of mortality and population turnover is consistent with their relatively precocious sexual maturity, rapid decline in fecundity , and polygynous or promiscuous mating system .
Socio-Spatial Behavior: Frank and Heske (1992) used radiotelemetry to investigate the space use patterns of the southern grasshopper mouse in the Chihuahuan Desert of southeastern Arizona. They found that the average home ranges of breeding males were about twice as large as female home ranges (3.7 hectares [ha] versus 1.7 ha); non-breeding males had smaller home ranges than breeding males (2.6 ha versus 3.7 ha); and no difference between the home ranges of non-breeding and breeding females. During the breeding season , there was extensive home range overlap between males and between males and females, but little overlap in the home ranges of females. McCarty (1975) suggests that territories are advertised by the grasshopper mouse’s characteristic high-pitched vocalization. During the non-breeding season , grasshopper mouse socio-spatial behavior is markedly different from the breeding season. Female territoriality breaks down in the non-breeding season and Frank and Heske (1992) observed sharing of burrows by individuals of both sexes. They suggest that males compete among themselves for females during the breeding season and that the observed spatial variation reflects their sex-specific reproductive strategy. During the breeding season, spacing patterns probably reflect male-male competition . During the non-breeding season, sharing of burrows may provide thermoregulatory advantages and/or may serve social functions. Frank and Heske (1992) provide an anecdotal report that burrow sharing was prominent during a cold front on their study site in the Chihuahuan Desert. Population densities of the southern grasshopper mouse are relatively low for a rodent species. McCarty (1975) reported a density of 1.8 mice/ha in a Mojave Desert creosote scrub community and others also have reported low population densities (e.g. , Baily and Sperry 1929; Frank and Heske 1992). Such low population densities are consistent with the species’ carnivorous habits and the distribution and availability of prey items.
- Chatton, 1925
- C. Linnaeus, 1758
- (Hatschek, 1888) Cavalier-Smith, 1983
- Grobben, 1908
- (Haeckel, 1874) Cavalier-Smith, 1998
- Grobben, 1908
- Bateson, 1885
- Cuvier, 1812
- Jawed Vertebrates
- Zittel, 1879
- Jawed Vertebrates
- C. Linnaeus, 1758
- (Rowe, 1988) M.C. McKenna & S.K. Bell, 1997
- Huxley, 1880
- McKenna, 1975
- McKenna, 1975
- McKenna, 1975
- (McKenna, 1975) M.C. McKenna & S.K. Bell, 1997
- (Parker & Haswell, 1897) M.C. McKenna & S.K. Bell, 1997
- (Owen, 1837) M.C. McKenna & S.K. Bell, 1997
- Szalay & McKenna, 1971
- (C. Linnaeus, 1758)
- (Szalay & McKenna, 1971) McKenna, 1975
- (Weber, 1904) M.C. McKenna & S.K. Bell, 1997
- Bowdich, 1821
- Brandt, 1855
- Infraorder: Myodonta () - (Schaub, in Grassé & Dekeyser, 1955) M.C. McKenna & S.K. Bell, 1997
- Suborder: Myomorpha () - Brandt, 1855
- Order: Rodentia () - Bowdich, 1821 - Rodents
- Mirorder: Simplicidentata () - (Weber, 1904) M.C. McKenna & S.K. Bell, 1997
- Grandorder: Anagalida () - (Szalay & McKenna, 1971) McKenna, 1975
- Superorder: Glires () - (C. Linnaeus, 1758)
- Magnorder: Boreoeutheria () - Szalay & McKenna, 1971
- Cohort: Placentalia () - (Owen, 1837) M.C. McKenna & S.K. Bell, 1997
- Supercohort: Theria () - (Parker & Haswell, 1897) M.C. McKenna & S.K. Bell, 1997
- Infralegion: Tribosphenida () - (McKenna, 1975) M.C. McKenna & S.K. Bell, 1997
- Sublegion: Zatheria () - McKenna, 1975
- Legion: Cladotheria () - McKenna, 1975
- Superlegion: Trechnotheria () - McKenna, 1975
- Infraclass: Eutheria () - Huxley, 1880
- Subclass: Boreosphenida () - (Rowe, 1988) M.C. McKenna & S.K. Bell, 1997
- Class: Mammalia () - C. Linnaeus, 1758
- Superclass: Gnathostomata () - Zittel, 1879 - Jawed Vertebrates
- Infraphylum: Gnathostomata () - auct. - Jawed Vertebrates
- Subphylum: Vertebrata () - Cuvier, 1812 - Vertebrates
- Phylum: Chordata () - Bateson, 1885 - Chordates
- Superphylum: Deuterostomia () - Grobben, 1908
- Infrakingdom: Chordonia () - (Haeckel, 1874) Cavalier-Smith, 1998
- Branch: Deuterostomia () - Grobben, 1908
- Subkingdom: Bilateria () - (Hatschek, 1888) Cavalier-Smith, 1983
- Kingdom: Animalia () - C. Linnaeus, 1758 - Animals
Genetics: Relatively little genetic information of value to conservation planning in the MSHCP study area is available for the southern grasshopper mouse. It has a diploid chromosome number of 48, and according to Hsu and Bernischke (1968; cited in McCarty 1975), the species exhibits considerable subspecific variation in basic chromosomal morphology. Riddle and Honeycutt (1990) investigated restriction-endonuclease-site variation of mitochondrial DNA (mtDNA) to study geographic and phylogenetic variation in the genus Onychomys. They found little mtDNA variation in O. torridus within the hot desert Mojavean-Sonoran-Sinaloan regions, but no samples were taken from the southern California coastal region. Whether the coastal region represents a distinct area of genetic endemism separate from the hot desert regions is unknown.
Members of the genus Onychomys
ZipcodeZoo has pages for 8 species and subspecies in this genus:
O. arenicola (Chihuahuan Grasshopper Mouse) · O. arenicola arenicola (Chihuahuan Grasshopper Mouse) · O. leucogaster (Grasshopper Mouse) · O. leucogaster durranti (Durrant's Northern Grasshopper Mouse) · O. torridus (Southern Grasshopper Mouse) · O. torridus ramona (Southern Grasshopper Mouse) · O. torridus torridus (Southern Grasshopper Mouse) · O. torridus tularensis (Tulare Grasshopper Mouse)
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- A distributional list of the mammals of California, by Joseph Grinnell. San Francisco, The Academy, 1913. url p. 302.
- An account of the birds and mammals of the San Jacinto area of southern California with remarks upon the behavior of geographic races on the margins of their habitats by J. Grinnell and H.S. Swarth. Berkeley, University of California Press, 1913. url p. 329.
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- California mammals / by Frank Stephens; illustrated by W. J. Fenn from studies in the field. San Diego, Calif.: West Coast Pub. Co., 1906. url p. 101.
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- Field book of North American mammals; descriptions of every mammal known north of the Rio Grande, together with brief accounts of habits, geographical ranges, etc., by H. E. Anthony. .. with 32 coloured plates and 175 photographs, pen-and-ink sketches and maps. New York, G. P. Putnam's Sons, 1928. url p. 340.
- Mammals of the Mexican boundary of the United States: a descriptive catalogue of the species of mammals occurring in that region; with a general summary of the natural history, and a list of trees / Washington: Govt. Print. Off., 1907. url , .
- Naturalist's guide to the Americas, prepared by the Committee on the Preservation of Natural Conditions of the Ecological Society of America, with assistance from numerous organizations and individuals, assembled and edited by chairman, Baltimore, Williams & Wilkins, 1926. url p. 584, p. 584, p. 588, p. 588.
- Proceedings - California Academy of Sciences, 4th series. San Francisco, California Academy of Sciences. url p. 302.
- Proceedings of the Biological Society of Washington. Washington, Biological Society of Washington url p. 124.
- Proceedings of the California Academy of Sciences, 4th series. San Francisco, California Academy of Sciences. url p. 302, p. 50.
- Proceedings of the United States National Museum. Washington: Smithsonian Institution Press, [etc.] url p. 468, p. 469, p. 489.
- Transactions of the San Diego Society of Natural History. 13 1964 [San Diego]: The Society, 1905-1989. url p. 131, p. 46, p. 46.
- University of California publications in zoology. Berkeley: University Press, 1906- url p. 317, p. 319, p. 329.
- Brands, S.J. (comp.) 1989-present. The Taxonomicon. Universal Taxonomic Services, Zwaag, The Netherlands. Accessed January 10, 2012.
- Global Biodiversity Information Facility. Accessed October 27, 2006. http://www.gbif.org Mediated distribution data from 3 providers.
- Hafner, D.J. 1996. In IUCN 2008. 2008 IUCN Red List of Threatened Species. IUCNRedList.org. Downloaded July 18, 2008.
- Hafner, D.J. 1996. Onychomys torridus ssp. ramona. In: IUCN 2006. 2006 IUCN Red List of Threatened Species. <www.iucnredlist.org>. Downloaded on 20 October 2006.
- Integrated Hardwood Range Management Program, Understanding the Plants and Animals of Western Riverside County MSHCP University of California, Berkeley and Center for Conservation Biology, University of California, Riverside.
- Biodiversity Heritage Library NamebankID: 7164003
- Integrated Taxonomic Information System (ITIS) Taxonomic Serial Number (TSN): 180301
- IUCN ID: 15342
- Natural Heritage Network Species Identifier: AMAFF06022
- Zipcode Zoo Species Identifier: 153555