St Andrew beach mouse: Peromyscus polionotus peninsularis

Taxonomic Classification

Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Rodentia
Family: Muridae
Genus/Species: Peromyscus polionotus
Subspecies: Peromyscus polionotus peninsularis
Common Name: St. Andrew beach mouse

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

Physical Description

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).

Life History

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).

Habitat and Distribution

St Andrew Beach Mouse Distribution 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.


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 External Website.

Federal Recovery Plan External Website

Other Informative Links

Animal Diversity Web External Website
Florida Natural Areas Inventory External Website
FWC Beach Mouse Facts  Adobe PDF
University of Florida External Website
U.S. Fish & Wildlife Service Recovery Plan External Website



Printable version of this page Adobe PDF


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

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

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

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

Image Credit Photo courtesy of USFWS

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