Mammals -- Florida


ABSTRACT This summarizes a study conducted on the Archie Carr (ACNWR) and Pelican Island (PINWR) National Wildlife Refuges located on the barrier island complex of southern Brevard and northern Indian River counties, Florida. Major objectives of this study were designed to 1) survey the mammals of the ACNWR and PINWR, 2) perform a small mammal population demographic study in coastal scrub and maritime hammock habitats, and 3) document a population monitoring project of Peromyscus po/ionotus niveiventris in northern Indian River County at Treasure Shores Park, within ACNWR Segment 4. A total of7,279 trap nights was compiled during the survey portion of this research: 5,136 on ACNWR and 2,514 on PINWR yielding a combined total of 1,152 captures of 10 species of nonvo lant mammals. Seventeen species of mammals were documented through live trapping, observations, and recorded as road kills. Three species represent additions to the list of mammals once found in the study area, having not been documented in the historical literature. Two are exotic or introduced mammals (Dasypus novemcinctus and Rattus rattus) and one is the native carnivore Lontra canadensis. Seven species of rodents were recorded historically, only five were documented during this study. Two native rodents, Neofiber al/eni and Oryzomys palustris, were not captured while another native species, P. polionotus niveiventris, has dra1natically declined. Capture success ,vas highest on ACN\VR in xeric ha1runock habitat (28.3%) and lovvest in dune habitat (5.9%). On PINWR~ capture success \Vas highest in marititne hanunock habitat ( 14. 7%) and lo\vest in salt marsh/i1npoundment habitat (2.2%). Peromyscus gossypinus was the most abundant mammal, accounting for 55% (481/875) of all captures on ACNWR and 78.7% (218/277) of all captures on PINWR. The second most abundant matnmal was Sigmodon hispidus, accounting for 39.8% (348/875) of all captures on ACNWR and 7.6% (21/277) of all captures on PINWR. Species richness was highest on ACNWR and PINWR in maritime hammock habitat and lowest in salt marsh/impound1nent habitat on both refuges. Five species of native rodents were captured while one species of exotic or non-native rodent was documented through live trapping. Native rodents were distributed in all habitats (eight)~ vvhereas the non-native R. rattus was captured in three of these habitats. Six small 1na1nmals were captured 322 titnes after compiling 5,631 trap nights on three trap grids in two habitats of ACNWR and PINWR. Two s1nall ma1nmals, P. gossypinus and S. hispidus, were the 1nost frequently encountered species. The number of individual P. gossypinus and S. hispidus captured per 100 trap nights and densities varied on the three grids. Density estimates of P. gossypinus ranged from 4.4 to 20.9 individuals/ha in coastal scrub and from 22 to 50 individuals/ha in maritime hammock. Densities of S. hispidus ranged from 0.9 to 15.1/ha on two grids in coastal scrub. Survival rates of P. gossypinus and S. hispidus did not differ significantly among seasons. Weight of adult male P. gossypinus fluctuated seasonally in both coastal scrub and 1naritime hammock habitat. Lowest weights were observed in coastal scrub during spring 1998 while heaviest weights were observed during summer 1998. Adult male P. gossypinus in maritime hammock were heaviest during winter 1999 and lowest during summer 1998. Adult body weights of male S. hispidus varied significantly among seasons. Sex ratios of P. gossypinus were dominated by males on all three grids while sex ratios of S. hispidus in coastal scrub habitat were close to unity. Seasonal reproductive activity of P. gossypinus in coastal scrub habitat was highest during fall 1998 and winter 1999 while reproduction was confined to the fall and winter months in maritime hammock. Greatest seasonal reproductive activity of S. hispidus was exhibited during summer and fall 1998. The age structure of both P. gossypinus and S. hispidus on all three grids was largely dominated by adults. In a total trapping effort of 5,505 trap nights conducted from November 1996 to January 1999 at Treasure Shores Park, 54 captures of28 individual P. polionotus niveiventris were recorded. The number of new individuals captured ranged from a low of two to a high of 13. Recaptures outnumbered new individuals during summer 1997 and winter 1998 however, by spring 1998, recaptures composed 100% ofthe overall captures. Estimates of population size using the Lincoln-Petersen estimator ranged from a low of two to a high of 18 individuals. After three trapping sessions resulted in no captures, further trapping efforts were suspended and it became evident that the Treasure Shores Park population of P. polionotus niveiventris has experienced a tremendous decline. Three individuals were then discovered in oldfield habitat west of SRAlA, opposite the Treasure Shores Park study site. The primary threat to this subspecies' existence in the northern Indian River County portion of ACNWR is habitat loss resulting fro1n the destruction of the pri1nar) dunes b) coastal erosion caused by the jett~ at Sebastian Inlet.

Graduation Date



Ehrhart, Llewellyn M.


Master of Science (M.S.)


College of Arts and Sciences






205 p.




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Masters Thesis (Open Access)




Arts and Sciences -- Dissertations, Academic; Dissertations, Academic -- Arts and Sciences

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