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Remarkable Movements of an American Crocodile (Crocodylus acutus) in Florida
Michael S. Cherkiss, Frank J. Mazzotti, Lindsey Hord, and Mario Aldecoa

Southeastern Naturalist, Volume 13, Issue 4 (2014): N52–N56

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2014 Southeastern Naturalist Notes Vol. 13, No. 4 N52 M.S. Cherkiss, F.J. Mazzotti, L. Hord, and M. Aldecoa Remarkable Movements of an American Crocodile (Crocodylus acutus) in Florida Michael S. Cherkiss1,*, Frank J. Mazzotti2, Lindsey Hord3, and Mario Aldecoa4 Abstract - Here we present the remarkable movements of an individual Crocodylus acutus (American Crocodile) over a 14-year period. The crocodile was originally marked in Homestead, FL as a young-of-the-year in 1999, and was later recaptured multiple times more than 388 km away along the southwest coast of Florida. After several relocations and numerous sightings, this individual who has become known as Yellow Number 1 was found back within the same canal system in which it was first captured. Although long-distance movements of crocodiles are often reported, there are few, if any, studies to chronicle movements over a crocodile’s lifetime. Crocodylus porosus Schneider (Saltwater Crocodile) have frequently been observed at sea (Campbell et al. 2010), and satellite and GPS telemetry of adult Saltwater Crocodiles showed long-distance movements of more than 400 km along the coast and up tidal rivers of Australia (Campbell et al. 2010, 2013; Read et al. 2007) as well as within non-tidal water-holes (Brien 2008). Crocodiles and Alligator mississippiensis Daudin (American Alligator) also demonstrate a strong homing behavior, returning to the location of capture after being displaced long distances (Murphy and Coker 1984, Read et al. 2007). Crocodylus acutus Cuvier (American Crocodile) is the most widely distributed New World crocodilian. It is found in Florida, Mexico, both Atlantic and Pacific coasts of Central America and northern South America, and on the Caribbean islands of Cuba, Jamaica, and Hispaniola (Thorbjarnarson 1989). It has been suggested that this wide distribution is the result of long-distance dispersal. Recent records of American Crocodiles in the Dry Tortugas, FL (Cherkiss et al. 2006), and the Cayman Islands are suspected to be the result of long-distance movements from the closest breeding populations in Florida, and Cuba or Jamaica, respectively. Movements of >10 km by American Crocodiles have been regularly observed in Florida (Table 1). Kushlan and Mazzotti (1989) described several long-distance movements (20, 100, 150 km) of an American Crocodile after translocation by government wildlife officers. The longest movement of 150 km was from Naples on the southwest coast of Florida, to Flamingo in Everglades National Park. During breeding season, adult female American Crocodiles have traveled up to 35.5 km to nesting habitat (Cherkiss et al. 2007). Florida Fish and Wildlife Conservation Commission (FWC) officials try to reduce human–crocodile conflict by moving problem crocodiles; long-distance movements have often followed translocations (data presented here). FWC officials use numbered, colored tags for marking American Crocodiles so that they can document future observations, movements, and homing behavior without the need to recapture the individual. Fifteen American Crocodiles are documented to have made long-distance movements after transport and release in Florida; there is complete information available for 13 of them 1US Geological Survey, Southeast Ecological Science Center, 3205 College Avenue, Davie, FL, 33314. 2University of Florida, Ft. Lauderdale Research and Education Center, 3205 College Avenue, Davie, FL, 33314. 3Florida Fish and Wildlife Conservation Commission, 8122 US HWY 441 SE, Okeechobee, FL, 34974. 4Florida Power and Light Company, Turkey Point Power Plant, 9760 SW 344th Street, Homestead, FL, 33035. *Corresponding author - Manuscript Editor: Max Nickerson Notes of the Southeastern Naturalist, Issue 13/4, 2014 N53 2014 Southeastern Naturalist Notes Vol. 13, No. 4 M.S. Cherkiss, F.J. Mazzotti, L. Hord, and M. Aldecoa Table 1. Movements of American Crocodiles that were translocated by Florida Fish and Wildlife Conservation Commission (FWC) staff. Information included is from FWC databases or personal communications. Distance under release location was the straight-line distance the American Crocodile was moved by FWC staff. Distance under recapture location was the straight-line distance moved by the American Crocodile. No. = number assigned to individual crocodiles. * = information was not collected or reported and therefore, is not available for these criteria. Sex and size (cm) Recapture location Size at Growth rate No. at capture Capture location Release location (distance km) (distance km) recapture (cm) (cm/day) 1 Female 220 Deering Bay C-111 (44) Deering Bay (44) 232 0.04 1 Female 232 Deering Bay Collier Seminole State Park (137) Deering Bay (137) 245 0.04 2 Male 175 Ocean Reef Aerojet Canal (29) Ocean Reef (29) 208 0.12 3 Male 239 Snowden Canal Aerojet Canal (*) Deering Bay (41) 357 0.05 4 Male 221 Ocean Reef Aerojet Canal (29) Ocean Reef (29) 228 0.05 5 Male 328 Cutler Bay C-111 (41) Deering Bay (44) 345 0.02 6 Male 341 Deering Bay C-111 (44) Deerng Bay (44) 344 0.01 6 Male 344 Deering Bay C-111 (44) Deerng Bay (44) * * 6 Male* Deering Bay C-111 (44) Deerng Bay (44) * * 7 Male 279 Coral Gables C-111 (46) Coral Gables (46) 321 0.07 8 Female 238 Islamorada Islamorada (5) Islamorada (6) 264 0.07 9 Male 255 Gray Oaks, Naples Rookery Bay Preserve (17) Lake Tarpon (253) 330 0.04 9 Male 330 Lake Tarpon C-111 (393) Turkey Point (16) * * 10 Male 312 Ocean Reef C-111 (15) Ocean Reef (15) 304 -0.01 11 Female* Islamorada C-111 (32) Plantation Key (31) 253 * 12 Female 220 Ocean Reef C-111 (15) Palm Beach (142) 258 0.03 13 Male 290 South Miami C-111 (51) South Miami (51) 290 0.00 14 Female 180 Snapper Creek Black Point (19) Snapper Creek (19) 198 0.05 15 Male 122 N Palm Beach * (*) N Palm Beach (*) 135 0.13 2014 Southeastern Naturalist Notes Vol. 13, No. 4 N54 M.S. Cherkiss, F.J. Mazzotti, L. Hord, and M. Aldecoa (Table 1). All 15 crocodiles returned to or within a couple kilometers of their original capture location. Two crocodiles were transported twice or more and returned each time to the site of their original captures, including one movement that covered a straight-line distance of 137 km. Here we describe the movements of a male American Crocodile that was originally marked in 1999 and died in 2014. The male whose movements we describe was originally captured as a young-of-theyear at the Turkey Point Power Plant Site (TP) in Homestead, FL on 20 December 1999; it was 42.9 cm total length (TL). Before release, TP staff inserted an internal PIT tag #116733445A) and gave the American Crocodile a unique tail clip (999) to facilitate later identification. This animal was not seen again until nine years later, in 2008, when an FWC trapper identified an American Crocodile while investigating a complaint of a nuisance American Alligator at the golf course located at Gray Oaks Country Club in Collier County, FL (26°11.330ˈN, 81°45.574ˈW). The FWC does not remove American Crocodiles unless the individual situation requires it, and because the property’s management did not request removal, the American Crocodile was left on site. Two months later, the country club’s point of contact requested that the FWC relocate the animal because residents were concerned for their personal safety. On 10 November 2008, FWC staff captured the adult male American Crocodile, now measuring 254.6 cm TL, and relocated it to the east boundary of Rookery Bay National Estuarine Reserve (26°02.764ˈN, 81°42.509ˈW) (Fig. 1). Based on the tailclip marking-pattern of 999 and internal PIT tag #116733445A, biologists identified the animal as having been marked nine years earlier and nearly 169 km distant at TP. During September 2011, an American Crocodile was reported in lower Tampa Bay, Hillsborough County, FL. The animal was not captured but, based on size and tail markings, it was thought to be the same individual, nearly 208 km from its last known location. The next sighting was on 8 July 2013 when the American Crocodile (330 cm TL) was inadvertently captured by a nuisance-alligator trapper who had set a baited hook for an American Alligator in Lake Tarpon, Pinellas County (28°8.777ˈN, 82°43.533ˈW), 253 km from the last release site. The trapper later released the American Crocodile at the C-111 canal in Dade County (25°15.706ˈN, 80°25.654ˈW) after attaching a cattle-ear tag (yellow #1) to its tail. Just over 6 months later, the animal, now known as Yellow #1, had died and its body was discovered on 16 January 2014 (300 cm TL) in the Interceptor Ditch canal at TP (25°22.907ˈN, 80°22.037ˈW) (Fig. 1). The calculated growth rate for this American Crocodile was 0.06 cm/day from initial capture in 1999 through its capture in 2013. This growth rate is within the range reported for translocated American Crocodiles in Florida (Table 1). However the growth rate for Yellow Number 1 is at the lower end of growth rates reported for American Crocodiles in the wild (Mazzotti et al. 2007), and is most similar to those reported for Everglades National Park. After its many movements, Yellow #1 died and was found within several kilometers of where it was originally marked over 14 years earlier in the TP canal system. The movements of this American Crocodile document the ability of a least some individuals of the species to disperse long distances outside the species’ known contemporary range. In contrast to the American Crocodile movements described by Kushlan and Mazzotti (1989), humans did not aid this animal’s dispersal from the natal area. The travels undertaken by this individual suggest that American Crocodiles, which are strongly associated with mangrove habitats (Kushlan and Mazzotti 1989, Mazzotti 1999) may be able to keep up with the northward range extension that is occurring as a result of climate change (Cavanaugh et al. 2013). N55 2014 Southeastern Naturalist Notes Vol. 13, No. 4 M.S. Cherkiss, F.J. Mazzotti, L. Hord, and M. Aldecoa We do not know how Yellow Number 1, or the female American Crocodile (number 1, Table 1) moved from one coast of Florida to the other. The American Crocodile described by Kushlan and Mazzotti (1989) moved from Naples to Flamingo after translocation, indicating that American Crocodiles can move around the southern tip of the peninsula. Southwest Florida also connects directly to southeast Florida via the Tamiami Canal, and the female could have used this route. How these movements occur could be determined by satellite telemetry as employed in Australia by Read et al. (2007). Humans aided the return of Yellow Number 1 to TP when they relocated the animal to southern Dade County. However, other American Crocodiles have homed to their capture site after translocation by Figure 1. Locations where Yellow Number 1 was observed and locations from where the American Crocodiles presented in Table 1 were relocated to and from in south Florida. 2014 Southeastern Naturalist Notes Vol. 13, No. 4 N56 M.S. Cherkiss, F.J. Mazzotti, L. Hord, and M. Aldecoa humans, including one that made the reverse journey from southwest Florida to southeast Florida (Table 1); Saltwater Crocodiles translocated in Australia behaved similarly (Read et al. 2007). This finding confirms the limited nature of using translocation as a management solution for problem crocodiles. In addition to reporting long-distance movements by American Crocodiles, the data presented here demonstrate the value of long-term monitoring and management programs and provide an example of how they can provide valuable information which cannot be obtained through any other means. Acknowledgments. This report was made possible by the long-term crocodile-monitoring program at the Florida Power and Light Coompany’s Turkey Point Power-Plant site and the Florida Fish and Wildlife Conservation Commission crocodile-response program. Literature Cited Brien, M.L., M.E. Read, H.I. McMallum, and G.C. Grigg. 2008. Home range and movements of radio-tracked Estuarine Crocodiles (Crocodylus porosus) within a non-tidal waterhole. Wildlife Research 35:140–149. Campbell, H.A., M.E. Watts, S. Sullivan, M.A. Read, S. Choukroun, S.R. Irwin, and C.E. Franklin. 2010. Estuarine Crocodiles ride surface currents to facilitate long-distance travel. Journal of Animal Ecology 79:955–964. Campbell, H.A., R.G. Dwyer, T.R. Irwin, and C.E. Franklin. 2013. Home-range utilization and longrange movement of Estuarine Crocodiles during the breeding and nesting season. PLoS ONE 8(5): e62127. doi:10.1371/journal.pone.0062127. Cavanaugh, K.C., J.R. Kellner, A.J. Forde, D.S. Gruner, J.D. Parker, W. Rodriquez, and I.C. Feller. 2013. Poleward expansion of mangroves is a threshold response to decreased frequency of extreme cold events. Proceedings of the National Academy of Sciences of the United States of America 2:723–727. Cherkiss, M.S., O.S. Bass, and F.J. Mazzotti. 2006. Crocodylus acutus geographic distribution. Herpetological Review 37:491. Cherkiss, M.S., M. Parry, and F.J. Mazzotti. 2007. Crocodylus acutus (American Crocodile) migration. Herpetological Review 38:72–73. Kushlan, J.A., and F.J. Mazzotti. 1989. Historic and present distribution of the American Crocodile in Florida. Journal of Herpetology 23:1–7. Mazzotti, F.J. 1999. The ecology of the American Crocodile in Florida Bay. Estuaries 22:552–561. Mazzotti, F.J., L.A. Brandt, P.E. Moler, and M.S. Cherkiss. 2007. American Crocodile (Crocodylus acutus) in Florida: Recommendations for endangered species recovery and ecosystem restoration. Journal of Herpetology 41:121–131. Murphy, T.M., and J.W. Coker. 1984. American Alligator population studies in South Carolina. Study completion report. South Carolina Wildlife and Marine Resources Department, Division of Wildlife and Freshwater Fisheries, Charleston, SC. 116 pp. Read, M.A., G.C. Grigg, S.R. Irwin, D. Shanahan, and C.E. Franklin. 2007. Satellite tracking reveals long-distance coastal travel and homing by translocated Estuarine Crocodiles, Crocodylus porosus. PLoS one 2:e949. Thorbjarnarson, J.B. 1989. Ecology of the American Crocodile, Crocodylus acutus. Pp. 228–258, In Crocodiles: Their Ecology, Management, and Conservation. A special publication of the Crocodile Specialist Group of the Species Survival Commission, 228–258. IUCN–The World Conservation Union, Gland, Switzerland.