Salt marsh harvest mouse

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Salt-marsh harvest mouse
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Rodentia
Family: Cricetidae
Subfamily: Neotominae
Genus: Reithrodontomys
R. raviventris
Binomial name
Reithrodontomys raviventris
Dixon, 1908
  • R. r. raviventris
  • R. r. halicoetes

The salt-marsh harvest mouse (Reithrodontomys raviventris), also known as the red-bellied harvest mouse, is an endangered rodent endemic to the San Francisco Bay Area salt marshes in California.[4]


The two distinct subspecies are both endangered and listed together on federal and state endangered-species lists. The northern subspecies (R. r. halicoetes) is lighter in color and inhabits the northern marshes of the bay, and the southern subspecies (R. r. raviventris) lives in the East and South Bay marshes. They are both quite similar in appearance to their congener species, the western harvest mouse (R. megalotis), to which they are not closely related. Genetic studies of the northern subspecies have revealed that the salt-marsh harvest mouse is most closely related to the plains harvest mouse (R. montanus),[5] which occurs in the Midwest. The endangered designation of the salt-marsh harvest mouse is due to its limited range, historic decline in population and continuing threat of habitat loss due to development encroachment on the perimeter of the San Francisco Bay.


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. An adult's length is 5–7 centimetres (2.0–2.8 in) and a tail length of 6–10 centimetres (2.4–3.9 in). Its height is between 1.5 and 2.1 centimetres (0.59 and 0.83 in). The weight of a mature mouse is about 10–20 grams (0.35–0.71 oz). The northern subspecies is also dorsally brown or reddish brown, but the venters tend to be white or cream, and rarely with a hint of reddish; tail length is usually about 120% of the body length.[6] The upper incisors are grooved. As a member of the Neotominae subfamily, the dental formula of R. raviventris is × 2 = 16.[7]

This species is nocturnal, with particularly noted activity on moonlit nights. This mouse is particularly resourceful, making use of ground runways of other rodents; moreover, it also exhibits climbing agility. It occupies marsh habitats where pickleweed and marsh plants abound. Its many predators include hawk, snake and owl species, as well as shorebirds and larger mammals. Predation by domestic cats is an issue due to encroachment of the limited habitat by humans at the perimeter of the San Francisco Bay.

Similar species[edit]

Similar species are the plains harvest mouse (Reithrodontomys montanus) and the fulvous harvest mouse (R. fulvescens), which has a longer tail. 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. This adaptation to solely survive on salt water is unknown to many researchers and cannot be investigated due to their endangerment. It is thought that the salt marsh harvest mouse has special kidney function that allows this phenomenon.[citation needed] The northern species can survive purely on salt water, but prefers fresh to salt water. The southern species can survive on either, and does not display a preference.[8] Another way to differentiate these species is based on aggression and docility. Often, the salt-marsh harvest mouse is quite docile and less easily agitated than its sister species, the western harvest mouse.[9]


Survey data from Suisun Marsh found that the salt-marsh harvest mouse can live up to 18 months and possibly longer. Females commonly have two litters per year. The home range and habitat use of this species differ temporally across age and sex. Juveniles exhibit home ranges of 600–700 square metres (6,500–7,500 sq ft), whereas adults exhibit home ranges of 1,300–1,500 square metres (14,000–16,000 sq ft).[10] Males and females also differ in the structural complexity of their occupied habitat during fall and summer (breeding season), but occupy the same habitat during winter and spring. While the cause is still unknown, this seasonal disparity in habitat use may be related to a reduced risk of predation and intraspecific competition in more structurally complex habitats.[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]

Distribution and habitat[edit]

The salt-marsh harvest mouse is an endangered species endemic to the San Francisco Bay. Its salt marsh habitat could be highly impacted by sea-level rise.

This organism is known to be found in these specific locales:


The mice depend heavily on vegetation cover, particularly pickleweed and tules (Schoenoplectus spp.). Pickleweed (Salicornia virginica) is their primary and preferred habitat, as well their main food source, but R. raviventris is found in a variety of marsh habitats, including diked and tidal wetlands.[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.[15]


The salt-marsh harvest mouse has lost much of its habitat to extensive development and clearing of bayside marshland, pollution, boat activity, and commercial salt harvesting. It has been on the endangered lists since the 1970s, and has protected habitat within numerous Bay Area wildlife refuges. Individual political jurisdictions have conducted research and established habitat protection strategies to protect the salt marsh harvest mouse. For example, the city of San Rafael, California, has established a shoreline setback standard to prevent any land development within 50 feet of the shoreline; this measure has been applied to several specific land developments along the San Francisco Bay shoreline.[16] Researchers, such as Katherine Smith of California Department of Fish and Wildlife, are at the forefront of research helping to identify how threats like climate change impact the species, while increasing the understanding of its biology, ecology, and behavior.[17][18] NatureServe considers the species Critically Imperiled.[19]

Reference in 2009 economic stimulus debate[edit]

The preservation of the salt-marsh harvest mouse habitat was a subject of discussion in 2009 economic stimulus package. 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.[20] It was claimed that $30M of the 2009 economic stimulus would be spent on habitat restoration to protect the mouse. The rumor was apparently started by Michael Steel, press secretary for John Boehner.[21][22] This was disputed in a San Francisco Chronicle article by Democratic Rep. Jackie Speier.[23]


  1. ^ Whitaker Jr, J.O.; NatureServe (2018). "Reithrodontomys raviventris". IUCN Red List of Threatened Species. 2018: e.T19401A22385344. doi:10.2305/IUCN.UK.2018-1.RLTS.T19401A22385344.en. Retrieved 12 November 2021.
  2. ^ 35 FR 16047
  3. ^ "Salt-marsh Harvest Mouse". U.S. Fish & Wildlife Service. Retrieved 15 February 2023.
  4. ^ Musser, G. G. and M. D. Carleton. 2005. Superfamily Muroidea. Mammal Species of the World: A Taxonomic and Geographic Reference, D. E. Wilson and D. M. Reeder eds. Baltimore: Johns Hopkins University Press. ISBN 978-0-8018-8221-0.
  5. ^ Presentation by Sarah Brown: Conservation genetics of salt marsh harvest mice (Reithrodontomys raviventris). Presented at College of Science and Math Symposium, California State University, San Luis Obispo. 5/01
  6. ^ Sustaita, Diego; Quickert, Patty Finfrock; Patterson, Laura; Barthman-Thompson, Laureen; Estrella, Sarah (2011). Kuenzi, Amy J. (ed.). "Salt marsh harvest mouse demography and habitat use in the Suisun Marsh, California". The Journal of Wildlife Management. 75 (6): 1498–1507. doi:10.1002/jwmg.187. S2CID 84461021.
  7. ^ Wilson, Don E.; Reeder, DeeAnn M. (2005). Mammal Species of the World: A Taxonomic and Geographic Reference. JHU Press. ISBN 9780801882210.
  8. ^ a b Golovanova, Galina. "The Biogeography of the Salt Marsh Harvest Mouse (Reithrodonomys raviventris)". Geography 316-Biogeography. San Francisco State University. Archived from the original on 16 January 2010.
  9. ^ "About the Salt Marsh Harvest Mouse". Salt Marsh Harvest Mouse. Retrieved 22 October 2022.
  10. ^ Geissel, W.; Shellhammer, H.; Harvey, H. T. (29 November 1988). "The Ecology of the Salt-Marsh Harvest Mouse (Reithrodontomys raviventris) in a Diked Salt Marsh". Journal of Mammalogy. 69 (4): 696–703. doi:10.2307/1381624. ISSN 0022-2372. JSTOR 1381624.
  11. ^ Bias, Michael A.; Morrison, Michael L. (1 June 2006). "Habitat Selection of the Salt Marsh Harvest Mouse and Sympatric Rodent Species". Journal of Wildlife Management. 70 (3): 732–742. doi:10.2193/0022-541X(2006)70[732:HSOTSM]2.0.CO;2. ISSN 0022-541X. S2CID 86233156.
  12. ^ Bias, Michael A.; Morrison, Michael L. (1999). "Movements and Home Range of Salt Marsh Harvest Mice". The Southwestern Naturalist. 44 (3): 348–353. JSTOR 30055230.
  13. ^ "Threatened & Endangered Animal Species of Point Reyes" (PDF). National Park Service. Retrieved 25 September 2016.
  14. ^ Sustaita, Diego; Quickert, Patty Finfrock; Patterson, Laura; Barthman-Thompson, Laureen; Estrella, Sarah (1 August 2011). "Salt marsh harvest mouse demography and habitat use in the Suisun Marsh, California". The Journal of Wildlife Management. 75 (6): 1498–1507. doi:10.1002/jwmg.187. ISSN 1937-2817. S2CID 84461021.
  15. ^ Smith, Katherine R.; Kelt, Douglas A. (November 2019). "Waterfowl management and diet of the salt marsh harvest mouse". The Journal of Wildlife Management. 83 (8): 1687–1699. doi:10.1002/jwmg.21752. ISSN 0022-541X.
  16. ^ Hogan, C. Michael et al. (1989). Spinnaker-on-the-Bay Expanded Initial Study, Earth Metrics Inc., prepared for the city of San Rafael, California
  17. ^ "Researchers seek secrets of Suisun salt marsh harvest mouse". Daily Republic. 24 June 2011. Retrieved 20 April 2017.
  18. ^ "Salt-Water Science up Close". UC Davis. 14 April 2014. Retrieved 20 April 2017.
  19. ^ "Reithrodontomys raviventris.NatureServe Explorer 2.0". Retrieved 27 April 2023.
  20. ^ "Category:Salt Marsh Harvest Mouse". Archived from the original on 20 August 2010.
  21. ^ Paul Rogers; Bay Area News Group (13 February 2009). "Bay Area mouse spurs national debate over stimulus bill". The Mercury News. Retrieved 15 February 2023.
  22. ^ Erbe, Bonnie (13 February 2009). "Republicans Flop On Pelosi Mouse Lie, Haven't Learned Environmental Lesson". CBS News. Retrieved 15 February 2023.
  23. ^ Speier, Jackie (14 February 2009). "The myth of the 'San Francisco mouse'". Retrieved 15 February 2023.

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