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St. Andrew Beach Mouse

Peromyscus polionotus peninsularis

Listing Status

  • Federal Status: Endangered
  • FL Status: Federally-designated Endangered
  • FNAI Ranks: G5T1/S1 (Globally: Demonstrably Secure, Sub sp. Critically Imperiled/State: Critically Imperiled)
  • IUCN Status: Not ranked


The St. Andrew beach mouse is a subspecies of the small old-field mouse that can reach a length of 5.5 inches (14 centimeters).  This species of beach mouse has a yellowish-brown colored dorsal (back) side which can run from the eyes down to the thighs, or end suddenly before it reaches the thighs.  They have a two inch long tail that is usually white, but it can have a light colored stripe on the dorsal side (Florida Natural Areas Inventory 2001).


The diet of the St. Andrew beach mouse primarily consists invertebrates and seeds from dune plants. 

Very little information is available about the life history of the St. Andrew beach mouse, so information about the beach mouse species (Peromyscus polionotus) is generally accepted as the same.  Breeding peaks during the winter months, but can occur year around if there is adequate food available.  Beach mice are monogamous and will mate with only one partner at a time.  The total gestation period for a beach mouse is 23 days, with the female giving birth to an average of four pups per litter.  Females are also capable of breeding 24-hours after giving birth (Bird et al. 2009).  Pups are weaned 18 days after they are born (NatureServe 2011).  Sexual maturity is reached around 30 days of age (Foust 2002).


St. Andrew beach mouse map

The St. Andrew beach mouse inhabits sand dunes from the St. Joseph Peninsula in Gulf County, to near the former entrance of St. Andrew Bay in Bay County, Florida.


St. Andrew beach mouse

The main threat facing the St. Andrew beach mouse is continued coastal development along beaches.  Development along beaches can cause destruction or degradation to sand dunes limiting areas of habitat for the beach mouse, and increasing fragmentation, leading to isolation of populations.  Increased traffic on sand dunes is also a threat for the beach mouse, as the increased traffic damages vegetation on dunes that the beach mice depend on for food and shelter.  Hurricanes also pose a risk to the beach mouse as they can cause damage and destruction to their sand dune habitat with the accompanying intense winds and storm surge.  Other threats include increased predation from feral and free-ranging cats, foxes, raccoons, and coyotes.

Conservation and Management

The St. Andrew beach mouse is protected as an Endangered species by the Federal Endangered Species Act and as a Federally-designated Endangered species by Florida’s Endangered and Threatened Species Rule.

Federal Recovery Plan

Learn more about how you can live with and conserve beach mice.


Bird, B. L., Branch, L. C., & Hostetler, M. E. (n.d.). Beach Mice. Retrieved June 2, 2011, from IFAS Extension:

Florida Natural Areas Inventory.  2001.  Field guide to the rare animals of Florida.

Foust, D. 2002. "Peromyscus polionotus" (On-line), Animal Diversity Web. Accessed August10, 2011

NatureServe. 2011. NatureServe Explorer: An online encyclopedia of life [web application]. Version 7.1. NatureServe, Arlington, Virginia. Available (Accessed: August 10, 2011 ).