The southern population of the salt-marsh harvest mouse tends to have dark brown fur above and a pinkish cinnamon or tawny belly; moreover, the tail is likewise bicolored.

Predation by domestic cats is an issue due to encroachment of the limited habitat by humans at the perimeter of the San Francisco Bay.

The species co-occurs with the similar western harvest mouse (R. megalotis), which tends to have dorsal fur that is more gray than R. raviventris and with ventral fur that is white to grayish; and the house mouse (Mus musculus), which is gray, has a scaly tail, and incisors without grooves, unlike those of the salt-marsh harvest mouse.In the summer, when salinity of water and vegetation increases, the mice have a notable advantage due to their ability to drink and survive purely on salt water.

[9] Survey data from Suisun Marsh found that the salt-marsh harvest mouse can live up to 18 months and possibly longer.

[11] Furthermore, movement of R. raviventris individuals within their home ranges varies seasonally, with mean distance traveled highest in June and lowest in November.

[12] This organism is known to be found in these specific locales: The mice depend heavily on vegetation cover, particularly pickleweed and tules (Schoenoplectus spp.).

[14][8] In a 2019 study on the food preferences of the salt-marsh harvest mouse, it was concluded that the species has a much more flexible diet than assumed years prior.

They prefer pickleweed only at specific seasonal times, showcased a strong liking for different plants that aren't native to the area, and typical foods enjoyed by waterfowl.

The mouse was mentioned numerous times in Congress by Republicans such as Rep. Mike Pence and Rep. Dan Lungren to highlight the wasteful spending of the bill.