Merriam’s pocket mice inhabit several different vegetation and habitat types throughout their range. In central and southern Texas they live in shortgrass or heavily grazed pasture dominated by mesquite (Prosopis glandulosa). In western regions, they inhabit desert scrubland characterized by rocky soil and limited vegetation. Merriam’s pocket mice appear to have no preference for soil type within its geographic range, residing in areas of clay, caliche, and sand. (Best and Skupski, 1994; Chapman and Packard, 1974)
Merriam’s pocket mice are small heteromyid rodents whose weight and length (including body and tail) averages from 7 to 10 grams and 113.9 to 116.4 mm, respectively. Average weight and size varies depending on geographic region. Within Texas, for example, this species is smallest in the south, moderate in size in the west, and the largest in north. Males are slightly larger in size. For example, in Coahuila, Mexico an average difference of 0.9 grams between males and females has been reported. Throughout its range, the pelage of is smooth and silky, and when pressed down may be oily in appearance. The dorsal side of the pelage is ochraceous buff colored with black hairs; the ventral side is solid white. Merriam’s pocket mice are morphologically distinguishable from other pocket mice in the genus (such as Perognathus flavus) by its shorter mastoid breadth, shorter bullar length, slightly smaller hind foot, longer average tail length, and a relatively small post-auricular white spot. No data on metabolic rate was found for . However, Perognathus flavus, the sister species to , has a basal metabolic rate of 2.09 cc O2/g hr.
Recent genetic analyses has confirmed the diagnosis of P. flavus, despite earlier reports indicating and P. flavus are conspecific based on behavioral analyses. Two subspecies of are currently recognized: P. m. gilvus in the northwestern portion of its range and P. m. merriami in the southeastern portion of its range. (Best and Skupski, 1994; Brant and Lee, 2006; Coyner, et al., 2010; Genoways and Brown, 1993; Martin, 1977)as a sister species to
The mating system of Merriam’s pocket mouse is not known. However, it is likely that this species exhibits similar mating systems as what is observed in other species of Perognathus and Chaetodipus. These heteromyid genera are closely related, and both belong to the subfamily Perognathinae. Because of larger home range observations for males than females, such as in C. formosus and P. parvus, and larger mean capture distance in P. longimembris, it is assumed exhibit polygynous or promiscuous mating systems. (Genoways and Brown, 1993)
The breeding season of Merriam’s pocket mouse ranges from April to November, with some individuals producing two litters per season in southern portions of its range. The mass at birth is unknown. However, P. longimembris has a neonate weight of 0.9 grams and although this Perognathus species is larger than , birth mass may be similar. Typical litters usually consist of three to six individuals, and young retain a soft, yellow colored pelage that lacks the black hairs that are present on the dorsal side of adults. The gestation period is unknown for ; P. flavus, its sister species, has a gestation period of 26.0 days. It is therefore likely that has a similar gestation time.
Young males may molt into adult pelage and be sexually mature before reaching the final mass of an adult. Females, however, do not appear to be reproductively viable when they are the same mass as a viable juvenile male. Gestation, birth mass, time to weaning, time to independence, and reproductive ages for both sexes of (Best and Skupski, 1994; Chapman and Packard, 1974; Genoways and Brown, 1993)are not known at this time.
Parental investment is unknown; no data were available for the Merriam’s pocket mouse or other Perognathus species.
Merriam’s pocket mice maintain a system of burrows within their home ranges. Males typically maintain six to seven burrows per individual, while females appear to keep around five, on average. They prefer to dig the burrows at the bases of bunchgrasses or other vegetation to add stability to the entrance of the tunnel. Merriam’s pocket mice often have two types of burrows: a refuge and home burrow. Home burrows are much larger, with enlarged nest chambers and two entrances; refuge burrows have one entrance, are shorter in length, and have smaller chambers. Merriam’s pocket mice are nocturnal and remain in the burrow until sundown. Heteromyid rodents are generally thought to avoid contact with other conspecifics, with most encounters (with the exception of mating) lacking in physical contact. (Best and Skupski, 1994; Chapman and Packard, 1974; Genoways and Brown, 1993)
Merriam’s pocket mice occupy territories between 0.03 and 2.19 ha depending on the sex of the individual, with females typically occupying larger areas, but males tending to travel farther outside of their territories than females. Territory ranges are roughly equal to home ranges, and territories of Merriam’s pocket mice do not overlap each other, a strong indicator of territorial behavior. (Best and Skupski, 1994; Chapman and Packard, 1974)
Little information exists on communication in Merriam's pocket mice, as they normally emit no sound. However, they produce a high-pitched squeak when handled. Other members of Heteromyidae use olfactory communication to exchange information at burrowing and sandbathing sites. Some species, such as Dipodomys spectabilis, have been observed drumming their feet on the ground as a means of communication. No records of this behavior have been recorded in . (Best and Skupski, 1994; Genoways and Brown, 1993)
Prosopis glandulosa), little bluestem (Schizachyrium scoparium), and coastal sandbur (Cenchrus spinifex), among many others. The mouse appears to forage for its food based on seasonal abundance, but will discriminate based on palatability. Merriam's pocket mice do not drink water, obtaining all of the moisture needed from its food sources. (Best and Skupski, 1994; Chapman and Packard, 1974; Schmidly, 2004)typically maintains a diet of seeds, but may consume insects and vegetation. Plant species it has been known to consume include honey mesquite (
Merriam's pocket mice are preyed upon by northern grasshopper mice (Onychomys leucogaster), gray foxes (Urocyon cinereoargenteus), loggerhead shrikes (Lanius ludovicianus), and barn owls (Tyto alba). (Best and Skupski, 1994; Raun, 1960)
Little is known of major effects of Androlaelaps fahrenholzi), fleas (Orchopeas leucopus), ticks (Amblyomma americanum), and lice (Fahrenholzia boleni). Endoparasites obtained from include the coccidian Eimeria reedi.on its environment. Merriam’s pocket mice act as hosts to multiple species of ectoparasites ranging from mites (
Merriam’s pocket mice occur in environments that are sympatric with Baiomys taylori, Chaetodipus hispidus, C. nelsoni, C. penicillatus, Dipodomys merriami, Perognathus flavus, and Sigmodon hispidus. (Best and Skupski, 1994; Chapman and Packard, 1974; Genoways and Brown, 1993)
Merriam’s pocket mice can be kept as pets in suitable enclosures filled with slightly damp sand. They should be fed seeds occasionally. Other than being kept as pets, there are no known positive effects of (Best and Skupski, 1994)on humans.
Merriam’s pocket mice are reservoirs for diseases that have the potential to be transmitted to humans. They carry hantaviruses albeit at low frequencies. (Mantooth, et al., 2001)
Merriam’s pocket mice appear to be stable due to their large range and sizeable population with no major conservation concerns at this time. (Linzey, et al., 2008)
Hunter Folmar (author), Texas A&M University, Jessica Light (editor), Texas A&M University, Tanya Dewey (editor), University of Michigan-Ann Arbor.
living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.
uses sound to communicate
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
either directly causes, or indirectly transmits, a disease to a domestic animal
uses smells or other chemicals to communicate
in deserts low (less than 30 cm per year) and unpredictable rainfall results in landscapes dominated by plants and animals adapted to aridity. Vegetation is typically sparse, though spectacular blooms may occur following rain. Deserts can be cold or warm and daily temperates typically fluctuate. In dune areas vegetation is also sparse and conditions are dry. This is because sand does not hold water well so little is available to plants. In dunes near seas and oceans this is compounded by the influence of salt in the air and soil. Salt limits the ability of plants to take up water through their roots.
animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.
an animal that mainly eats leaves.
an animal that mainly eats seeds
An animal that eats mainly plants or parts of plants.
offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).
having the capacity to move from one place to another.
the area in which the animal is naturally found, the region in which it is endemic.
active during the night
an animal that mainly eats all kinds of things, including plants and animals
the business of buying and selling animals for people to keep in their homes as pets.
the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.
having more than one female as a mate at one time
breeding is confined to a particular season
remains in the same area
reproduction that includes combining the genetic contribution of two individuals, a male and a female
places a food item in a special place to be eaten later. Also called "hoarding"
uses touch to communicate
that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).
Living on the ground.
defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement
A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.
A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.
A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.
uses sight to communicate
reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.
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