Extensive development has destroyed and fragmented wildlife habitat in the
Lower Florida Keys. The Lower Keys marsh rabbit (LKMR; Sylvilagus palustris
hefneri) and the silver rice rat (SRR; Oryzomys argentatus) are listed by the United
States Fish and Wildlife Service (USFWS) and the Florida Fish and Wildlife
Conservation Commission (FFWCC) as endangered species. Both species depend on
coastal prairies, freshwater marshes, and intertidal salt-marsh zones. The objective of
this study was to meet specific, species-level recovery goals and to add reliable
information that may modify or support current recovery plans. Specifically, I (1)
evaluated the use of LKMR reintroduction to suitable habitat, (2) examined
characteristics of habitat used by LKMR, and (3) surveyed the Lower Florida Keys for
SRRs, documenting current range and examining survey results for the past decade.
I reintroduced 7 rabbits (3 males, 4 females) to suitable habitat on Water Key,
and monitored their survival and release-site fidelity. All reintroduced rabbits survived
and some reproduced, suggesting these translocation techniques are a viable tool for
recovery. On Boca Chica Key, I radio-collared 13 LKMRs and compared vegetation
characteristics between core-use and avoided areas within home ranges. Binary logistic
regression associated rabbit use with high vegetation heights (7âÂÂ8 dm), low canopy coverage (<=10%), high bunchgrass densities (2.5âÂÂ3.8/sq m), and forb presence (>5%),
supporting the hypothesis that LKMRs may be detrimentally impacted by hardwood
encroachment into salt-marsh habitats. For LKMR recovery, I recommend management
to resist hardwood encroachment, together with active predator control.
I surveyed 36 locations on 18 islands for SRRs, capturing rats on 12 islands,
including 2 on which SRRs had not previously been found. Comparisons of my data
with historic data suggest SRRs either have increased in abundance over the past decade
or that previous trapping efforts were not effective. Abundance of SRRs does not appear
to be significantly different from that of populations of rice rats on the mainland. The
USFWS and FFWCC should consider revising the conservation status of the SRR;
however, it still should be regarded as a unique evolutionary unit with a very limited
potential range.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/4260 |
| Date | 30 October 2006 |
| Creators | Perry, Neil Desmond |
| Contributors | Lopez, Roel R. |
| Publisher | Texas A&M University |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | Book, Thesis, Electronic Thesis, text |
| Format | 1272879 bytes, electronic, application/pdf, born digital |
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