Baiomys taylori (Thomas, 1887)

Scientific Name

This species has the scientific name Baiomys taylori (Thomas, 1887).

Adult Weight

Adult males average approximately 7.5 grams (0.26 oz), while adult females can weigh up to 9.4 grams (0.33 oz).

Average Body Measurements

Across all subspecies, the average adult body length is 64.1 millimetres (2.52 in), and average tail length is 42 millimetres (1.7 in).

Size Geographic Variation

Following Bergmann's rule, populations in the north and at high altitudes are larger than populations in the south and at low altitudes.

Smallest Subspecies Size

B. t. allex, the southernmost subspecies, is the smallest, with an average total body length including the tail of 100 millimetres (3.9 in).

Largest Subspecies Size

The largest subspecies are B. t. analogus and B. t. fuliginatus, which have average total body lengths of 109 millimetres (4.3 in) and 105.5 millimetres (4.15 in), respectively.

Dorsal Fur Coloration

The fur of this species ranges from light brown to reddish brown to almost black.

Ventral Fur Coloration

Their undersides range from white to grayish.

Color Habitat Correlation

Darker individuals generally come from high-humidity, high-altitude habitats, while paler individuals come from low-humidity, low-altitude habitats.

Subspecies Color Variation

B. t. analogus, B. t. fuliginatus, and eastern B. t. taylori are darker; B. t. canutus, B. t. allex, and southern and eastern B. t. taylori are pale; and B. t. ater and B. t. paulus are reddish brown to match the soil of their habitats.

Juvenile Fur Color

Juveniles have distinctly gray fur before they shed into their adult coloration.

Pigmentation Abnormalities

Both albinism and melanism have been recorded in this species.

Litter Size

This pygmy mouse produces litters of 1 to 5 pups, with an average litter size of 3.

Gestation Period

Gestation for pregnant females lasts less than 20 days.

Paternal Care Behavior

Unlike many other rodents, male father pygmy mice care for offspring, grooming and huddling over the young.

Biparental Care

Both males and females provide care for the young.

Breeding Seasonality

This species breeds year-round, but breeding activity is reduced in winter and early spring.

Nest Location

Nests are typically built underneath logs or cacti.

Nest Structure and Material

They are ball-shaped, and constructed from cactus fibers, corn silk, and grasses.

Foster Rearing Study

A 1976 study found that B. t. ater raised by the house mouse Mus musculus had a greater tendency to have positive interactions with their foster species, and reacted more negatively to open spaces.

Learned Behavior Evidence

This indicates that the behavior of this species is influenced to some degree by learned behavior during youth.

Cross-Fostering Reciprocal Result

Mus musculus raised by B. taylori foster parents were not significantly behaviorally impacted.

Primary Diet

These mice are primarily granivorous, feeding mainly on small seeds.

Secondary Food Sources

They also consume green vegetation and insects when these resources are available.

Dry Habitat Diet

In dry habitats, the primary source of food and water is the fruit and stems of Opuntia cacti.

Captive Feeding Observations

In captivity, they have been observed feeding on insects, the terrestrial snail Helicina orbiculata, and the snake species Rena dulcis and Tropidoclonion lineatum, even when vegetative matter is offered.

Population Seasonal Fluctuation

They are more common in fall and winter, and less common during summer.

Wild Lifespan

The average lifespan in the wild is 5 months, but this likely varies across the species' range.

Captive Lifespan

In captivity, they can live up to 3 years, but typically survive only slightly longer than 5 months.

Habitat Preference

This species occupies a wide range of habitats, but prefers grasslands or shrubby deserts.

Opuntia Association

It is most strongly associated with grasslands that contain Opuntia cacti.

Runway Construction

It forms small tunnel-like runways through dense grass cover.

Congeneric Habitat Partitioning

Where the range of this species overlaps with Baiomys brunneus and Baiomys musculus, those two species prefer highland habitats, and B. taylori is more successful at overlapping altitudes.

Intestinal Parasite

Known parasites of the northern pygmy mouse include the intestinal nematode Pterygodermatites baiomydis.

Other Pathogens and Host Status

It also acts as a host for the flea Jellisonia ironsi, the mite Radfordia hamiltoni, and a type of Brucella bacteria; it cannot carry Brucella abortus.