Koford's Grass Mouse

Koford's Grass Mouse is a small, ground-dwelling rodent of the family Cricetidae endemic to the high-altitude puna grasslands of the southern Peruvian and northwestern Bolivian Andes. It belongs to the highly diverse genus Akodon, which contains over 40 species across South America. The species was formally described in 1989 and named in honor of the American biologist Carl B. Koford. It is well adapted to the cold, open grassland environments characteristic of Andean altiplano zones.

Southern Peru (Departments of Puno, Cusco, Arequipa) and northwestern Bolivia (Department of La Paz); restricted to the high Andes puna zone.

Known from southern Peru, particularly the Department of Puno around the Lake Titicaca basin and surrounding highlands, extending into Cusco and possibly Arequipa. Its range extends into northwestern Bolivia in the La Paz Department. Distribution is patchy and tied to suitable puna grassland habitats.

Altitude and depth

Typically found between 3,500 and 5,000 meters above sea level, with most records concentrated between 3,800 and 4,500 m in the puna zone of the Andes.

Seasonal movements

No documented large-scale seasonal migrations. Activity patterns may shift subtly between wet and dry seasons in response to food availability and temperature extremes, but the species appears to be a year-round resident of its range. No hibernation has been recorded.

Primarily inhabits puna grassland, a high-altitude tropical grassland and shrubland biome dominated by bunch grasses such as Festuca and Stipa. It is also found in rocky areas, moist grass-sedge meadows (bofedales), and scrubby transition zones near forest edges. This species tolerates cold, semi-arid to moist conditions typical of the Andean plateau.

Adaptations to its environment

Like other high-Andean Akodon, it likely has physiological adaptations for living at altitude including increased blood oxygen-carrying capacity. Its dense, relatively thick fur provides insulation against cold temperatures. Burrowing and use of grass tussocks for cover help it survive harsh Andean winters and avoid predators.

Listed as Least Concern (LC) by the IUCN. The species has a reasonably wide distribution across suitable puna habitat, and no dramatic population decline has been detected. Its occurrence in relatively remote high-altitude terrain affords it some protection from direct human disturbance.

Estimated population

No precise global population estimate exists. Population trend is presumed stable, as there is no evidence of significant decline. Local densities are typical for small Andean rodents and likely fluctuate with seasonal resource availability.

The primary threats include overgrazing by livestock (cattle, sheep, and camelids) which degrades puna grassland habitats, agricultural expansion at high altitudes, and climate change which is altering the distribution and quality of high Andean ecosystems. Mining activities in the Andes also pose localized threats to habitat integrity.

Diseases and parasites

Like other South American rodents, it is likely host to a range of ectoparasites (fleas, mites, ticks) and endoparasites (helminths, protozoa). Some Akodon species serve as reservoir hosts for hantaviruses and other zoonotic pathogens, though specific data for A. kofordi are lacking.

Protected indirectly within several Peruvian and Bolivian protected areas that encompass puna habitat, including the Titicaca National Reserve and various regional reserves. National biodiversity laws in Peru and Bolivia provide broad legal protection to native fauna. No species-specific conservation program exists.

Recommended actions

Continued monitoring of population status and distribution using live-trapping surveys. Improved management of grazing pressure in key puna habitats. Broader assessment of the impacts of climate change on high-Andean small mammal communities. Taxonomic and phylogeographic studies to clarify the species' boundaries and genetic diversity.

Dorsal fur is medium to dark brownish, often with a slightly grizzled appearance due to black-tipped guard hairs. Ventral fur is grayish-white to pale buff. The tail is bicolored, darker above and paler below. Eyes are small and dark; ears are moderate in size and rounded.

Size

Total body length approximately 95–125 mm; tail length approximately 60–85 mm; hindfoot approximately 18–22 mm. A typical small Akodon of moderate size for the genus.

Weight

Estimated body mass approximately 15–30 grams; sexual dimorphism in weight is minimal. No precise sex-specific weight data published.

Distinctive features

Distinguished from closely related species such as Akodon boliviensis and Akodon subfuscus by subtle differences in cranial morphology, particularly in the shape of the interparietal bone and zygomatic arch, as well as by karyotype and molecular characters. External morphology alone is insufficient for definitive identification in the field.

Differences between males and females

Sexual dimorphism is minimal; males and females are similar in size and coloration. As in many Akodon species, males may be very slightly larger on average than females.

Presumed to be largely solitary outside of the breeding season, as is typical for most Akodon species. Individuals likely maintain small home ranges and display some territorial behavior. No evidence of permanent pair bonding or complex social groups.

When it is active

Primarily nocturnal to crepuscular, with peak activity occurring at dusk, dawn, and during the night. This pattern helps avoid diurnal avian predators such as raptors common in Andean grasslands.

Diet

Omnivorous, with a diet consisting primarily of seeds, green plant material, and invertebrates such as insects and earthworms. Like other Akodon, it likely opportunistically exploits available food resources according to season. Arthropods may constitute a higher proportion of the diet during warmer, wetter months.

How it feeds and hunts

Forages on the ground among grass tussocks and under rocks, using its sensitive vibrissae and olfactory senses to locate food items. Invertebrates are likely caught by quick pursuit or gleaning from vegetation and soil surfaces. No specialized hunting techniques are documented.

Communication

Likely communicates via ultrasonic vocalizations used especially during social encounters and reproduction, as documented in related Akodon species. Scent marking with urine and glandular secretions is probable and may play a role in territory advertisement and mate attraction.

Interactions with other species

Likely prey for Andean raptors (Geranoaetus melanoleucus, Buteo species), owls (Tyto alba, Bubo virginianus), and terrestrial predators such as the Andean fox (Lycalopex culpaeus) and Pampas cat (Leopardus colocolo). Potential competition exists with sympatric small rodents such as Phyllotis and other Akodon species.

Role in its ecosystem

Functions as a secondary consumer and seed disperser within the puna ecosystem. As a prey item for numerous predators, it forms an important link in Andean food webs. Its burrowing and foraging activities contribute to soil turnover and plant community dynamics.

Breeding biology is not precisely documented for this species. By analogy with congeners in comparable habitats, reproduction likely peaks during the wet season (October–March). Gestation is estimated at approximately 21–23 days, with litter sizes of 2–6 young, typical for the genus.

Raising the young

Maternal care is primary, as in other Akodon. The female nurses and protects the altricial young in a grass-lined nest within a burrow or dense tussock. Young are weaned at approximately 2–3 weeks of age and reach independence shortly thereafter.

Maturity and lifespan

Sexual maturity is likely reached at approximately 2–3 months of age, consistent with other Akodon. Wild lifespan is estimated at 1–2 years; captive individuals of related species may survive up to 3 years.

Classification

Mammalia > Rodentia > Cricetidae > Akodon > Akodon kofordi

Scientific synonyms

No widely recognized synonyms; originally described as Akodon kofordi by Myers and Patton (1989). Sometimes placed near the Akodon boliviensis species group in older literature.

Recent studies

Molecular phylogenetic studies of the genus Akodon (e.g., Pardiñas et al., Jayat et al.) have helped clarify the position of A. kofordi within the boliviensis species group and confirmed its validity as a distinct species based on genetic data. Distributional surveys in southern Peru continue to refine its known range.

Genome and DNA

Karyotype has not been definitively published for this species. Related members of the Akodon boliviensis group typically have diploid numbers around 2n=40. The genus Akodon is notable for high karyotypic variability, including sex chromosome polymorphisms with XY females occurring in some species.

Compared with similar species

Akodon kofordi is most closely related to Akodon boliviensis (Bolivian Grass Mouse) and Akodon subfuscus (Puno Grass Mouse), with which it is broadly sympatric. It differs from these species primarily in cranial dimensions and molecular markers. All three inhabit similar high-altitude puna habitats and are morphologically very similar.

Koford's Grass Mouse survives at altitudes above 4,000 meters where nighttime temperatures can drop well below freezing, making it one of the hardiest small mammals on Earth. The genus Akodon includes species with XY females — a rare mammalian phenomenon where genetic males develop as females — though this has not been confirmed in A. kofordi specifically. Despite being named after a prominent biologist, this mouse went largely unstudied for decades after its formal description in 1989.

Where and how to see it

Best observed at night using spotlighting or live-trapping methods along grass-sedge meadows and rocky puna grasslands near the Lake Titicaca basin in Puno, Peru. The dry season (April–September) may offer better trapping success as vegetation cover is reduced. The area around the Titicaca National Reserve and Desaguadero corridor is a recommended survey site.

Risks to humans

No notable direct risk to humans. As with all wild rodents in South America, there is a theoretical risk of zoonotic disease transmission (e.g., hantavirus) through contact with urine or droppings; standard precautions are recommended when handling wild-caught specimens.