Pseudoryzomys

Pseudoryzomys simplex: The Brazilian False Rice Rat

Imagine a small rodent that has been around for centuries, yet so little is known about it. That’s the case with Pseudoryzomys simplex, also known as the Brazilian false rice rat or false oryzomys. This fascinating creature belongs to the family Cricetidae and can be found in the lowland palm savanna and thorn scrub habitats of south-central South America.

Origins and Taxonomy

First described independently in 1888, Pseudoryzomys simplex has a complex taxonomic history. It was initially named as Hesperomys simplex based on subfossil cave specimens from Brazil, and later as Oryzomys wavrini in 1921 after a live specimen from Paraguay. The species was formally confirmed by Voss and Myers in 1991 to be the same as both Winge’s Hesperomys simplex and Thomas’s Oryzomys wavrini.

Physical Characteristics

This medium-sized rodent has a unique appearance. Its fur is gray-brown, its hindfeet are long, and its tail is about as long as the combined length of its head and body. These features make it stand out among other rodents in the Sigmodontinae subfamily.

Relationships with Other Species

The closest living relatives of Pseudoryzomys simplex are the large rats Holochilus and Lundomys, which are semiaquatic. However, despite their aquatic lifestyle, these species share a common ancestor with Pseudoryzomys, highlighting the diverse adaptations within the Cricetidae family.

Taxonomic Classification

Classified under the subfamily Sigmodontinae and family Cricetidae, Pseudoryzomys simplex is part of a larger group that includes hundreds of species found across South America. Its unique features include interdigital webbing between its digits and a reduction in molar crown complexity.

Habitat and Distribution

This rodent can be found from northeastern Argentina, probably south to about 30°S, northward through western Paraguay to eastern Bolivia, and eastward through Brazil. It thrives in open, usually humid tropical and subtropical lowlands, often near water sources.

Behavior and Diet

Pseudoryzomys simplex is both terrestrial and semiaquatic, spending time on the ground as well as in the water. It has been found in pellets of barn owls and great horned owls, suggesting it may be a preferred prey for these predators.

Conservation Status

The IUCN classifies Pseudoryzomys simplex as being of least concern. While not threatened, habitat degradation could potentially endanger some populations. In Argentina, it was assessed as ‘potentially vulnerable,’ highlighting the need for continued monitoring.

Conclusion: The Enigma of Pseudoryzomys Simplex

Despite its widespread distribution and unique characteristics, Pseudoryzomys simplex remains a mystery in many ways. From its complex taxonomic history to the little known about its behavior and diet, this rodent continues to intrigue scientists and wildlife enthusiasts alike. As we continue to study these fascinating creatures, perhaps one day we will uncover more of their secrets.