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A New Record for the Maximum Length of the American Alligator
Arnold M. Brunell, Thomas R. Rainwater, Michael Sievering, and Steven G. Platt

Southeastern Naturalist, Volume 14, Issue 3 (2015): N38–N43

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2015 Southeastern Naturalist Notes Vol. 14, No. 3 N38 A.M. Brunell, T.R. Rainwater, M. Sievering, and S.G. Platt A New Record for the Maximum Length of the American Alligator Arnold M. Brunell1,*, Thomas R. Rainwater2, Michael Sievering3, and Steven G. Platt4 Abstract. An unusually large Alligator mississippiensis (American Alligator) was harvested in Alabama in 2014. We report on the animal’s length and mass, and document the techniques used to obtain those measurements. We compare our measurements to other extreme lengths and weights reported for the species. We show that the size of the American Alligator is consistent with known allometric relationships of head length, total length, snout–vent length, tail girth, and weight. The specimen’s straight-line total length of 450.0 cm (14 ft 9.25 in) makes it the longest officially measured American Alligator for Alabama and arguably the longest credible record for the species. We recommend using standardized techniques, particularly the straight-line total-length measurement, for documenting record-length or near-record-length American Alligators. The maximum length attained by crocodilians is a subject of varying opinions in both professional and lay circles. Maximum body size is also relevant from evolutionary and ecological perspectives, and upper asymptotic size is important when describing growth patterns (Platt et al. 2009, Woodward et al. 1995). Accounts of the longest crocodilians have often been based on reports lacking substantiating physical evidence. For instance, Greer (1974) used allometric relationships between Crocodylus porosus Schneider (Saltwater Crocodile) skull length and total body length to show that some claims of unusually long specimens had been exaggerated by more than 3 m. In the case of Alligator mississippiensis Daudin (American Alligator, hereafter Alligator), sources such as Conant and Collins (1998) have stated that the species has attained a total length (TL) of 584 cm (19 ft 2 in), as reported by McIlhenny (1935). Although the general public is likely to accept McIlhenny’s claim as fact, scientists familiar with crocodilian biology have questioned the validity of such a claim because there is no physical evidence (e.g., skull or skin) or corroborating documentation to support it (Platt et al., in press; Woodward et al. 1995). Based on estimated TLs from the largest known existing skulls and on knowledge of Alligator growth and aging patterns, Woodward et al. (1995) argued that an Alligator 584 cm in length was highly unlikely, and the probability of an animal exceeding 457 cm (15 ft) was extremely low. Similarly, other studies have estimated the mean asymptotic size for Alligators to be 379 cm in South Carolina (Wilkinson and Rhodes 1997) and 420 cm in Louisiana (Chabreck and Joanen 1979). Until recently, these contentions were supported by the fact that the longest verified (i.e., measured using credible, standardized methods with the existing physical evidence) Alligator was a 435.5-cm (14 ft 3.5 in) animal harvested in 2010 in Florida (Brunell et al. 2013). On 16 August 2014, an Alligator that exceeded previous verified TL records was harvested from the Alabama River in Wilcox County, AL, during the state’s public Alligator harvest (Fig. 1). The animal was transported to a taxidermist to be prepared as a wholebody mount at the hunter’s request. Prior to processing, biologists from the Alabama Department of Conservation and Natural Resources, Montgomery, AL (ADCNR), used 1Florida Fish and Wildlife Conservation Commission, 601 West Woodward Avenue, Eustis, FL 32726. 2Baruch Institute of Coastal Ecology and Forest Science, Clemson University, PO Box 596, Georgetown, SC 29440. 3Alabama Department of Conservation and Natural Resources, PO Box 305, Northport, AL 35476. 4Wildlife Conservation Society–Myanmar Program, Aye Yeik Mon 1st Street, Yadanamon Housing Avenue, Yangon, Myanmar. *Corresponding author - Manuscript Editor: David Steen Notes of the Southeastern Naturalist, Issue 14/3, 2015 N39 2015 Southeastern Naturalist Notes Vol. 14, No. 3 A.M. Brunell, T.R. Rainwater, M. Sievering, and S.G. Platt methods described in Brunell et al. (2013) to measure the animal’s TL, head length (HL), snout–vent length (SVL), and tail girth (TG). The straight-line TL of the Alligator was 450.0 cm (14 ft 9.25 in), which was 14.5 cm (5.75 in) longer than the previous verified record TL for the species (Brunell et al. 2013). Straight-line TL is measured by placing marks on a flat, level surface at the tip of the snout and tail tip and measuring the distance between them after the Alligator has been removed. In addition to the straight-line method, ADCNR biologists measured TL by extending a metal tape over the ventral surface of the Alligator while it was placed on its dorsum. This over-the-belly method resulted in a measurement of 458.5 cm (15 ft 0.5 in). The Alligator had an SVL of 239.0 cm, a TG of 122.0 cm, and an HL of 61.0 cm. The weight (WT) of the specimen was 458 kg (1011.5 lb), making it the heaviest Alligator recorded for Alabama. Although it is not uncommon for larger, older crocodilians to be missing the end of the tail from previous injuries (Webb and Messel 1978), the tail of this Alligator appeared intact. The previous record TL for an Alligator in Alabama was 432.0 cm (14 ft 2 in) over the back, from 2 Alligators of identical TL harvested from the Alabama River during statewide public hunts in 2011 (Wilcox County) and 2012 (Dallas County) (Brunell et al. 2013). The taxidermist who skinned the Alligator reported finding the front and rear halves of an adult Odocoileus virginianus Zimmermann (White-tailed Deer) carcass in the stomach, which added >45.4 kg (>100 lb) to the Alligator’s WT (Ken Owens, Ken’s Wildlife Images Taxidermy, Autaugaville, AL, pers. comm.). Based on the condition of the White-tailed Deer, the taxidermist speculated that it had been consumed 2–3 days before the Alligator was harvested. The taxidermist also reported finding 2 Sciurus carolinensis Gmelin (Gray Squirrel), skeletal remains of a Castor canadensis Kuhl (Beaver) or small Myocastor coypus Molina (Nutria), the mandible of a second White-tailed Deer, some rocks, and vegetation in the stomach of the Alligator. Figure 1. Alabama’s record American Alligator, harvested by Mandy Stokes on 16 August 2014 from the Alabama River in Wilcox County. The Alligator’s TL was 450.0 cm (14 ft 9.25 in), measured as the straight-line distance from the tip of the snout to the tip of the tail by Alabama Department of Conservation and Natural Resources biologists. The Alligator weighed 458 kg (1011.5 lb), the heaviest Alligator recorded for Alabama. Shown in the picture are the people involved in the harvest of the Alligator (from left to right): John Stokes, Mandy Stokes, Savannah Jenkins, Kevin Jenkins, and Parker Jenkins. This picture was provided by Mandy Stokes, and permission was obtained to publish each of their images and names. 2015 Southeastern Naturalist Notes Vol. 14, No. 3 N40 A.M. Brunell, T.R. Rainwater, M. Sievering, and S.G. Platt The straight-line TL measurement recorded by ADCNR biologists is based on a standard used by crocodilian biologists, which lends credibility to the record and allows comparisons with other crocodilians that have been measured using the same method (Brunell et al. 2013). The TL measurement taken over the belly, which is also an acceptable method, was 8.5 cm (3.25 in) greater than the straight-line method. This difference is to be expected because the metal tape follows body contours, adding length to the measurement. Body contours are also likely to increase variation of repeated measurements taken over the belly relative to the straight-line method. Another method used for measuring TL in crocodilians is to measure dorsally from snout tip to tail tip; this is especially useful in measuring larger live individuals, which are prone to respiratory distress if placed in a belly-up position (e.g., Britton et al. 2012). As with the over-the-belly method, a greater TL measurement is expected when using this method compared with the straight-line method. For example, the TL measurement taken dorsally from an exceptionally large Saltwater Crocodile captured in the Philippines in 2011 was 7.5 cm (3.0 in) greater than the straight-line measurement (Britton et al. 2012). This represented a 1% increase over the straight-line TL of 609.5 cm. Although a dorsal measurement was not taken for the Alabama Alligator, we speculate that it would have resulted in a 1–2% greater TL measurement than the straight-line method. The official TL of the Alabama Alligator initially reported by Safari Club International (SCI) was 480.0 cm (15 ft 9.0 in). The discrepancy between this SCI measurement and the one we report is likely the result of the different measurement techniques used and the condition of the animal at the time of measurement. We report the straight-line TL (as described above) measured while the animal was still intact. The official method used by SCI for measuring crocodilian body length is dorsally from snout tip to tail tip (see SCI official measuring form for body length of crocodilians [Method 16-C]; http://www.scifirstforhunters. org/recordbook/forms). However, representatives from SCI measured the Alligator after it had been decapitated and skinned. They combined the length of the head (81.2 cm [32.0 in]) with the length of the hide (398.8 cm [157.0 in]) to obtain their TL measurement (Randall Bush, SCI, McCalla, AL, pers. comm.). Woodward et al. (1987) showed that TL of large Alligators is ~6% less than the hide length. Because the SCI measurement is essentially the hide length, we subtracted 6% from the SCI measurement of 480.0 cm to obtain an estimated carcass TL of 451.2 cm—only 1.2 cm greater than our straight-line measurement of 450.0 cm. Since the initial reports of SCI’s official measurement, the organization modified their measurement to 459.7 cm (15 ft 1.0 in), based on applying their protocol to the full-body mounted specimen (R. Bush, SCI, McCalla, AL, pers. comm.). Although we do not recommend basing official measurements on processed animals, their modified measurement was much closer to the over-the-belly measurement taken by ADCNR. Predictive models relating different body dimensions to each other (Webb and Smith 1987) allow estimation of body size from skulls and other remains (Hall and Portier 1994, Platt et al. 2006, Thorbjarnarson and McIntosh 1987, Webb and Messel 1978, Woodward et al. 1995), calibrated photographs (Choquenot and Webb 1987, Stewart 1988), and tracks (Hutton 1987, Platt et al. 1990, Singh and Bustard 1977, Swanepoel et al. 2000, Thorbjarnarson and Hernandez 1993, Wilkinson and Rice 2000). We stress that the ability of these models to precisely estimate the TL of record Alligators may be limited because of the variation in allometric relationships and the unknown nature of these relationships outside of the size ranges used to develop the models. Nevertheless, we believe the models are informative enough to allow the scientific community to assess and potentially debunk claims of questionable credibility (Platt et al., in press), as well as validate the measurements of the Alabama Alligator that we present in this paper. Woodward et al. (1995) provided a model N41 2015 Southeastern Naturalist Notes Vol. 14, No. 3 A.M. Brunell, T.R. Rainwater, M. Sievering, and S.G. Platt for estimating TL from HL for Alligators. Applying the Alabama Alligator’s reported HL of 61.0 cm to this model results in an estimated TL of 433.0 cm. Although this value is 17.0 cm shorter than the measured TL, the actual measurement of 450.0 cm falls within the 95% confidence interval (CIs) for the estimate (CI = 405.0–463.0 cm). Total length can also be estimated from SVL using a model derived from Alligators taken during experimental harvests in Florida (Woodward et al. 1992). Applying the Alabama Alligator’s SVL of 239.0 cm to the Florida model results in an estimated TL of 452.5 cm. This estimate is only 2.5 cm greater than the measured TL and, therefore, is consistent with known allometric relationships defined for the species. Similarly, the reported weight of the Alabama Alligator can be compared with estimates derived from a model used in Florida to estimate WT from TL and TG (Woodward et al. 1992). The estimated WT based on a TG of 122.0 cm and TL of 450.0 cm is 432.0 kg, which is 26.5 kg (58.5 lbs) less than the reported WT. The difference in actual versus estimated WT can be explained in part by the contents of the Alligator’s stomach upon capture. The heaviest Alligator previously recorded in Alabama was a 432.0-cm Alligator harvested in 2011 that weighed 380.1 kg (838 lbs; Ray Metzler, Alabama Division of Wildlife and Freshwater Fisheries, Montgomery, AL, pers. comm.). The heaviest verified wild Alligator remains a 423.0-cm, 473.0-kg (1043-lb) specimen taken from Orange Lake, FL, in 1989 (Brunell et al. 2013). The inventory of food items found in the Alabama record Alligator’s stomach was conducted by the processor and was not a thorough inventory conducted by biologists; however, some of the reported items appear to be unique. To our knowledge, this is the first report of Gray Squirrel consumption by an Alligator, but this finding is not unexpected given that Alligators are considered highly opportunistic foragers. The Alligator may have encountered Gray Squirrels that had fallen into the water. The finding of Whitetailed Deer as a food item is not unprecedented, but to our knowledge, the consumption of an entire adult (albeit in 2 halves) has not been documented elsewhere. Epstein et al. (1983) reported that Alligators preyed upon radio-collared fawns but that none had been wholly consumed. Other studies have noted White-tailed Deer hair or skeletal remains in the stomachs or feces of Alligators (McNease and Joanen 1977, Shoop and Ruckdeschel 1990). Shoop and Ruckdeschel (1990) found parts of White-tailed Deer carcasses in Alligator holes but indicated consumption of the carcasses had occurred over an extended period. The paucity of records of whole or half White-tailed Deer carcasses among Alligator stomach contents likely reflect the improbability of Alligators attaining sizes capable of ingesting prey of this size. Dubansky (2012) presented functional-anatomical evidence that Alligators cannot swallow large prey items relative to their head size because of constraints in the neck and throat region. Despite persistent efforts to view a video taken by the processor’s employee that could supposedly verify the size and condition of the ingested deer, no visual evidence was produced. Although it is conceivable that the majority of an adult White-tailed Deer was in the stomach, we have been unable to confirm the report that the animal was swallowed in 2 halves. Documentation of the Alabama Alligator’s length and weight by ADCNR biologists lends credibility to this size record. Although there have been claims of larger Alligators (Platt et al., in press), the lack of associated physical evidence and rigorous measurement protocols make it difficult to substantiate their validity. Woodward et al. (1995) discussed a 64-cm HL skull (3 cm longer than the Alabama skull) at the Museum of Comparative Zoology (MCZ; Harvard University, Cambridge, MA) that was described by Barbour (1933) and is the longest known skull from an Alligator. Based on secondhand information reported 2015 Southeastern Naturalist Notes Vol. 14, No. 3 N42 A.M. Brunell, T.R. Rainwater, M. Sievering, and S.G. Platt by Cory (1896), the skull was from a Florida Alligator that was ~488 cm (16 ft) long. The estimated TL based on HL, however, was 453.6 cm (14 ft 10 in), slightly longer than the straight-line TL of the Alabama Alligator but much shorter than the TL reported by Cory (1896). Although the skull at the MCZ provides compelling and rare physical evidence of an unusually large Alligator, the lack of details regarding the methods used to obtain the TL measurement make it difficult to discern whether it was indeed longer than the Alabama Alligator we describe here. In conclusion, the Alabama Alligator is an impressive specimen of unusual size that appears to have attained a TL near the upper limit for the species based on growth rates and existing physical evidence (Wilkinson and Rhodes 1997, Woodward et al. 1995). We do not know whether this individual had reached its maximum size, but it seemed to have been in good health and capable of taking large prey (e.g., White-tailed Deer). To our knowledge, this is the largest American Alligator yet documented by professional biologists using standardized methods that can be validated with physical evidence. We recommend that professional biologists record the straight-line TL measurement, SVL, HL, TG, and WT (as described in Brunell et al. 2013) for record- or near-record-size crocodilian specimens. These data are essential to validate a record using known allometric relationships, thereby minimizing uncertainties resulting from inadequate or nonstandardized methodologies. 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