Baiomys taylori

Northern Pygmy Mouse
(*Baiomys taylori*)
Northern Pygmy Mouse (Baiomys taylori)
Range
Taxonomic classification
Order:	Rodentia
Suborder:	Supramyomorpha
Infraorder:	Myomorphi
Superfamily:	Muroidea
Family:	Cricetidae
Subfamily:	Neotominae
Tribe:	Baiomyini
Genus:	Baiomys
Binomial details
	Baiomys taylori (O. Thomas, 1887)
Other resources
	Full taxonomic details at MDD

As the common name implies, the Northern Pygmy Mouse (Baiomys taylori) is a small mouse. It can be found in a variety of xeric habitats, but mainly found in dense grassy areas or grasslands.

Description

From Eshelman & Cameron (1987): "Juveniles are uniformly gray above and lighter below (Packard, 1960). The dorsal pelage of adults varies from reddish brown, through gray to almost black above and white to creamy buff or gray below. The tail is covered with short hairs. Color of tail differs among subspecies and may be uniformly gray or bicolored (lighter ventrally)."

From Schmidly & Bradley (2016): "Smallest of the cricetid mice in Texas, with the exception of two harvest mice, Reithrodontomys humulis and R. montanus, both of which differ in having grooved upper incisors and longer tails. Upperparts grizzled grayish in adults, blackish in juveniles; underparts smoke gray; tail about three times as long as hind foot, sparsely haired, and decidedly shorter than head and body. They have a strong, musky odor similar to that of house mice, Mus musculus."

Museum specimens

The holotype for Baiomys taylori (NHMUK:ecatalogue:3597676) is archived in the Natural History Museum in London and images are not currently available. The holotype for Baiomys taylori subspecies subater is shown below.

Holotype: USNM 32616/44539. Baiomys taylori subater. Adult female. Bernard Creek, near Columbia, Brazoria County, Texas. Collected 25 February 1892.
Holotype: USNM 32616/44539. Baiomys taylori subater. Adult female. Bernard Creek, near Columbia, Brazoria County, Texas. Collected 25 February 1892.

External measurements

Length measurements are in millimeters (mm) and weight measurements are in grams (g), unless stated otherwise. If available, the sample size (n=) is provided. If a range is not provided and n= is not given, then the listed measurement represents an average.

Part of range	Reference	Total length	Tail length	Hindfoot length	Ear length	Mass
Arizona (southeastern)	Hoffmeister (1986)	92–113 (n=12)	33–47 (n=12)	13–15 (n=12)	9–13 (n=12)
not reported	Packard (1960)	87–123	34–53	12–15	9–12
Texas	Schmidly & Bradley (2016)	98	38	14.5		7–10 (avg 8)

Skull

From Eshelman & Cameron (1987): "Longitudinal, dorsal outline of the skull not evenly convex (outline anteriorly deflected ventrally from frontoparietal suture); entoglossal process of the basihyal rounded or absent; orbicular apophysis of malleus rounded to ovoid."

Holotype: USNM 32616/44539. Baiomys taylori subater. Adult female. Bernard Creek, near Columbia, Brazoria County, Texas. Collected 25 February 1892. Dorsal view of the skull.
Holotype: USNM 32616/44539. Baiomys taylori subater. Adult female. Bernard Creek, near Columbia, Brazoria County, Texas. Collected 25 February 1892. Ventral view of the skull.
Holotype: USNM 32616/44539. Baiomys taylori subater. Adult female. Bernard Creek, near Columbia, Brazoria County, Texas. Collected 25 February 1892. Lateral view of the skull.
Holotype: USNM 32616/44539. Baiomys taylori subater. Adult female. Bernard Creek, near Columbia, Brazoria County, Texas. Collected 25 February 1892. Dorsal view of the mandible.
Holotype: USNM 32616/44539. Baiomys taylori subater. Adult female. Bernard Creek, near Columbia, Brazoria County, Texas. Collected 25 February 1892. Lateral view of the left mandible.
Holotype: USNM 32616/44539. Baiomys taylori subater. Adult female. Bernard Creek, near Columbia, Brazoria County, Texas. Collected 25 February 1892. Upper molars.

Nest

Lateral view of the nest of a Northern Pygmy Mouse (Baiomys taylori). Image courtesy of the Smithsonian National Museum of Natural History.
Close up of the nest of a Northern Pygmy Mouse (Baiomys taylori). Image courtesy of the Smithsonian National Museum of Natural History.

Calls

The following call was provided by the Pasch Lab at the University of Arizona. For details regarding the anatomy and mechanisms of vocal production in Baiomys taylori, see Riede & Pasch (2020).

Hearing Safety Warning. This recording contains sonic frequencies that may be inaudible but could still be harmful at high volume. Start at a very low volume and increase only if needed.

Similar species

Comparison with Mus musculus

Compared with the House Mouse (Mus musculus), Baiomys taylori is a smaller species and has a shorter tail. Both species lack grooved upper incisors and have a musky odor.

Dorsal view of the the Northern Pygmy Mouse (Baiomys taylori).
Dorsal view of the House Mouse (Mus musculus).

Comparison with Reithrodontomys

The Eastern Harvest Mouse (Reithrodontomys humulis), Plains Harvest Mouse (Reithrodontomys montanus), Fulvous Harvest Mouse (Reithrodontomys fulvescens), and Western Harvest Mouse (Reithrodontomys megalotis) are all sympatric and differ in having grooved upper incisors. The Fulvous Harvest Mouse (Reithrodontomys fulvescens) also has a much longer tail than that of Baiomys taylori.

Western Harvest Mouse (Reithrodontomys megalotis)
Fulvous Harvest Mouse (Reithrodontomys fulvescens)
Eastern Harvest Mouse (Reithrodontomys humulis)
Plains Harvest Mouse (Reithrodontomys montanus)
Dorsal view of the the Northern Pygmy Mouse (Baiomys taylori).
Skull of the Fulvous Harvest Mouse (Reithrodontomys fulvescens) showing the grooved upper incisors, which are found in all members of the genus Reithrodontomys.

References

Armstrong DM, Fitzgerald JP, Meaney CA. 2010. Mammals of Colorado, Second Edition. Denver (CO, USA): University Press of Colorado.

Eshelman BD, Cameron GN. 1987. Baiomys taylori. Mammalian Species (285): 1-7. https://doi.org/10.2307/3503776

Hoffmeister DF. 1986. Mammals of Arizona. Tucson (AZ, USA): University of Arizona Press.

Packard RL. 1960. Speciation and evolution of the pygmy mice, genus Baiomys (Doctoral dissertation, University of Kansas, Zoology).

Riede T, Pasch B. 2020. Pygmy mouse songs reveal anatomical innovations underlying acoustic signal elaboration in rodents. Journal of Experimental Biology (223): jeb223925. https://doi.org/10.1242/jeb.223925

Schmidly DJ, Bradley RD. 2016. The mammals of Texas. Austin (TX, USA): University of Texas Press.

True FW. 1894. On the relationships of Taylor's mouse Sitomys taylori. Proceedings of the U.S. National Museum 16:757-7.