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New Record of Everglades Mink in Everglades National Park from the Stomach of an American Alligator
Adam E. Rosenblatt, James C. Nifong, Michael R. Heithaus, Mark W. Parry, and
Frank J. Mazzotti

Southeastern Naturalist, Volume 13, Issue 3 (2014): N22–N25

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2014 Southeastern Naturalist Notes Vol. 13, No. 3 N22 A.E. Rosenblatt, J.C. Nifong, M.R. Heithaus, M.W. Parry, and F.J. Mazzotti New Record of Everglades Mink in Everglades National Park from the Stomach of an American Alligator Adam E. Rosenblatt1,5,*, James C. Nifong2, Michael R. Heithaus1, Mark W. Parry3, and Frank J. Mazzotti4 Abstract - Species management and conservation strategies require accurate information about species distributions and behaviors. Neovison vison evergladensis (Everglades Mink) is listed in Florida as threatened, yet its current population status and distribution are unknown. We report the first incontrovertible evidence of the occurrence of Everglades Mink in Everglades National Park (ENP) in 15 years. Specifically, we found Everglades Mink hair in the stomach contents of a 254-cm (total length) adult male Alligator mississippiensis (American Alligator) captured in 2011 in the southwestern corner of ENP. Our finding confirms that Everglades Mink still inhabit the park, but we present a hypothesis suggesting that very few may be left there; potential causes of the decline include alterations to ENP hydrology and a recent increase in the number of large predators in ENP. Effective management and conservation of an animal species requires an accurate understanding of its distribution. However, distributions of some animals are difficult to determine through controlled study or surveys because of low population numbers and/or cryptic behaviors. Analyzing the stomach contents of predators is a technique that can be used to confirm the presence of particularly elusive species in a given area. Neovison vison evergladensis Hamilton (Everglades Mink), listed as threatened by the Florida Fish and Wildlife Conservation Commission (FWC) since 1973 (Gruver and Murphy 2013, Smith et al. 2013), is a subspecies of Neovison vison Schreber (American Mink) whose distribution and abundance in southern Florida has historically been difficult to quantify. The subspecies was first observed in Big Cypress National Preserve (BCP) in 1948 (Hamilton 1948). The archives of Everglades National Park (ENP), southeast of BCP, contain reports of sightings of Everglades Mink by fishermen and recreational users of the southern and central Everglades from as early as 1949, and multiple researchers reported sightings and roadkills along the northern border of ENP through 1979 (Layne 1974, Schwartz 1952, Smith 1980). In addition, Layne (1974) sighted Everglades Mink on Cape Sable on the southwestern coast of ENP. More recent studies of this animal have focused on populations in BCP (Humphrey and Zinn 1982) and Fakahatchee Strand Preserve State Park, west of BCP (Cunningham et al. 2009, Foster et al. 2007), an area where Everglades Mink are not uncommon (Smith et al. 2013). The history of Everglades Mink sightings in ENP, especially along the northern boundary of the park, would seem to suggest a relatively stable population in the southern Everglades. However, Everglades Mink have seemingly almost completely disappeared from ENP over the past two decades. The last reported Everglades Mink sightings included in the ENP archives occurred in 1992 and 1995, and the remains of two animals reported to be Everglades Mink were found inside the stomachs of Alligator mississippiensis Daudin (American Alligator) captured in ENP in 1996, but it is unclear how the specimen identifications were 1Department of Biological Sciences, Florida International University, Miami, FL 33174. 2University of Florida, Department of Biology, Gainesville, FL 32611. 3Everglades National Park, Homestead, FL 33034. 4Fort Lauderdale Research and Education Center, University of Florida, Davie, FL 33314. 5Current address - School of Forestry and Environmental Studies, Yale University, New Haven, CT 06520. *Corresponding author - Manuscript Editor: David Steen Notes of the Southeastern Naturalist, Issue 13/3, 2014 N23 2014 Southeastern Naturalist Notes Vol. 13, No. 3 A.E. Rosenblatt, J.C. Nifong, M.R. Heithaus, M.W. Parry, and F.J. Mazzotti verified (Barr 1997). Since then, an extensive small-mammal survey conducted in ENP between 2007 and 2009 reported no Everglades Mink sightings, despite 8610 camera-trap nights and the deployment of baited and mink-scent-marked floating camera-trap rafts in potential Everglades Mink habitats (Pifer et al. 2011). The exact cause of this apparent decline in the Everglades Mink population within ENP is unknown, but altered hydrology has been suggested as a major contributing factor (Smith 1980). Here we report the first record of Everglades Mink occurrence in ENP since 1996. Specifically, we found evidence of Everglades Mink during a study of American Alligator feeding habits conducted in the Shark River Estuary on the southwestern coast of ENP during 2009–2011. We captured an American Alligator (tag number: FWC 52505; 254- cm total length [TL] adult male) on 17 March 2011 in Rookery Branch (exact location: 25°26'35''N, 80°54'4''W) that contained 616 g of hair (wet mass) in its stomach contents along with pieces of Callinectes sapidus Rathbun (Blue Crab) and an unidentifiable fish. We sent a sample of the hair to the Florida Museum of Natural History (FLMNH; Gainesville, FL) where the hair’s shape, color, banding pattern, and length were assessed and compared to characters listed in an unpublished FLMNH key developed for Florida mammals. After using the key to determine the hair specimen was likely from an Everglades Mink, we microscopically compared our hair sample to hair from an Everglades Mink specimen in the museum’s collection (FLMNH accession number: UF 18800). We also compared the hair sample to hair from a specimen of another mustelid species that cooccurs with Everglades mink, Lontra canadensis Schreber (North American River Otter; FLMNH collection). On the basis of the above criteria, we unequivocally identified the hair sample as coming from an Everglades Mink. Mammal hair can remain in an American Alligator’s stomach for at least 10 days (Barr 1997), and American Alligators in the Shark River Estuary exhibit average movement rates as high as 3.2 km/day (Rosenblatt et al. 2013), therefore the Everglades Mink was likely eaten somewhere within a 32-km radius of the American Alligator’s capture location. We collected stomach contents from 53 other alligators during our independent study, but only two contained mammal hair (neither of which we identified as Everglades Mink). However, American Mink are commonly recovered from stomach contents in other coastal American Alligator populations. For example, a study performed on Sapelo Island, GA, found that American Mink were present in 10.7% of adult American Alligator (TL > 183 cm; n = 28) and 2.9% of sub-adult American Alligator (TL = 100–183 cm; n = 34) stomach contents (J.C. Nifong, unpubl. data). Our research provides evidence that Everglades Mink continue to inhabit ENP, and therefore ENP should still be considered part of the modern range of Everglades Mink. We hypothesize that the lack of recent live Everglades Mink sightings has largely been caused by continued human-driven alterations to Everglades hydrology, as others have suggested (Pifer et al. 2011, Smith 1980). Historically, the Everglades high water–low water hydrological cycle has been linked to southern Florida’s natural wet season–dry season rainfall dynamics, but since the early 1900s, anthropogenic changes to the Everglades have gradually decoupled Everglades water levels from rainfall dynamics (Light and Dineen 1994). This decoupling has seriously impacted many animal and plant populations that have evolved life-history characteristics tied to the natural hydrological patterns (e.g., Kushlan and Jacobsen 1990). In the case of Everglades Mink, it has been suggested that artificially high water levels during normally dry periods may result in den flooding and selection of suboptimal habitats as den sites, resulting in reduced reproduction (Smith 1980). Additionally, the dramatic population increases of some predators within ENP, including Canis latrans Say (Coyote) and the invasive Python molurus bivittatus Kuhl (Burmese 2014 Southeastern Naturalist Notes Vol. 13, No. 3 N24 A.E. Rosenblatt, J.C. Nifong, M.R. Heithaus, M.W. Parry, and F.J. Mazzotti Python) may also be contributing to the decline of Everglades Mink in ENP. Coyotes were first documented in ENP in 1993 (Pifer et al. 2011) and are now commonly sighted throughout ENP (M.W. Parry, pers. observ.). Though there have been no studies of Coyote dietary habits in ENP, they are known to eat mustelids in other parts of the southeastern US (Etheredge 2013). Burmese Pythons were first sighted infrequently within ENP during the 1980s, but beginning in about 2000 their numbers increased rapidly (Dorcas et al. 2012). Burmese Pythons have been implicated as the major cause of declines in the abundance of small mammal species within ENP (Dorcas et al. 2012). It is conceivable that Everglades Mink have been directly impacted by Burmese Python predation, resulting in reduced abundance and distribution of the mustelids within ENP, though initial studies of Burmese Python stomach contents have not yielded any evidence of Everglades Mink consumption (Snow et al. 2007). Another possibility is that heavy Burmese Python predation on an important prey species of Everglades Mink, i.e., Sylvilagus palustris Bachman (Marsh Rabbit; Snow et al. 2007; A. Sovie, University of Florida, Gainesville, FL, unpubl. data), has had negative indirect effects on Everglades Mink. The FWC species action plan for Everglades Mink recognizes the Burmese Python as a potential serious threat to Everglades Mink in ENP and lists other potential threats including altered hydrology, mercury contamination, habitat destruction, and disease (Smith et al. 2013). Given the apparently small number of Everglades Mink remaining in ENP and the impediments to their continued existence in the park, effective management and conservation of the species may be extremely difficult. In its species action plan for the Everglades Mink, the FWC recommended a number of conservation actions to stabilize the species’ population (Smith et al. 2013). Unfortunately, almost all the actions are dependent on learning more about the life history of Everglades Mink and their preferred habitats within southern Florida. Given the failure of recent extensive search efforts to locate any Everglades Mink in ENP (Pifer et al. 2011), the likelihood of learning more about their habits and behavioral patterns in the near future is low. However, our data from American Alligator stomach contents show that Everglades Mink still inhabit ENP, though possibly only in remote interior habitats. Continuing to study the dietary patterns of the Everglades Mink’s traditional predators like American Alligators as well as introduced predators, like Burmese Pythons, may be a promising avenue of future research on the cryptic Everglades Mink population. Acknowledgments. We thank the staff of ENP for their assistance in carrying out our research, all the volunteers who helped us gather American Alligator stomach content samples, the Florida Museum of Natural History for their assistance in identifying hair samples, and Adia Sovie for sharing pre-publication results of her Marsh Rabbit research. Our research was carried out under permits from ENP (EVER-2009-SCI-0024) and Florida International University’s (FIU) Institutional Animal Care and Use Committee (09-013). This material is based upon work supported by the National Science Foundation through the Florida Coastal Everglades Long-Term Ecological Research program under Grant No. DBI-0620409. Additional funding was provided by FIU. Literature Cited Barr, B. 1997. Food habits of the American Alligator, Alligator mississippiensis, in the southern Everglades. Ph.D. Dissertation. University of Miami, Miami, FL. 259 pp. Cunningham, M., D.B. Shindle, A.B. Allison, S.P. Terrell, D.G. Mead, and M. Owen. 2009. Canine distemper epizootic in Everglades Mink. Journal of Wildlife Diseases 45:1150–1157. Dorcas, M., J.D. Willson, R.N. Reed, R.W. Snow, M.R. Rochford, M.A. Miller, W.E. Meshaka, Jr., P.T. Andreadis, F.J. Mazzotti, C.M. Romagosa, and K.M. Hart. 2012. Severe mammal declines coincide with proliferation of invasive Burmese Pythons in Everglades National Park. Proceedings of the National Academy of Sciences 109:2418–2422. N25 2014 Southeastern Naturalist Notes Vol. 13, No. 3 A.E. Rosenblatt, J.C. Nifong, M.R. Heithaus, M.W. Parry, and F.J. Mazzotti Etheredge, C. 2013. Ecology and impacts of Coyotes (Canis latrans) in the southeastern United States. Ph.D. Dissertation. Clemson University, Clemson, SC. 107 pp. Foster, G., M.W. Cunningham, J.M. Kinsella, and M. Owen. 2007. Parasitic helminths of free-ranging Mink (Neovison vison) from southern Florida. The Journal of Parisitology 93:945–946. Gruver, B., and C. Murphy. 2013. Florida’s endangered and threatened species. Technical report. Florida Fish and Wildlife Conservation Commission, Tallahassee, FL. 11 pp. Hamilton, W. 1948. A new mink from the Florida Everglades. Proceedings of the Biological Society of Washington 61:139–140. Humphrey, S., and T.L. Zinn. 1982. 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