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Growth and Condition of American Alligators (Alligator mississippiensis) in an Inland Wetland of East Texas
David T. Saalfeld, Kevin K. Webb, Warren C. Conway, Gary E. Calkins, and Jeffrey P. Duguay

Southeastern Naturalist, Volume 7, Number 3 (2008): 541–550

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2008 SOUTHEASTERN NATURALIST 7(3):541–550 Growth and Condition of American Alligators (Alligator mississippiensis) in an Inland Wetland of East Texas David T. Saalfeld1,*, Kevin K. Webb1,2, Warren C. Conway1, Gary E. Calkins3, and Jeffrey P. Duguay1,4 Abstract - Since removal from the endangered species list, Alligator mississippiensis (American Alligator) populations have recovered to allow regulated harvest throughout most of their range. However, harvest/population management is complicated since alligators are long-lived, reach sexual maturity at a minimum size rather than age, and experience differential growth rates depending on geographic location, growing season length, local environmental conditions, habitat, and population density. To date, few data exist on age, sex, growth, and size structure of inland alligator populations. In this study, alligator growth rate and condition were quantified through an intensive mark-recapture study conducted at Angelina-Neches/Dam B Wildlife Management Area. Between May 2003 and October 2004, 279 alligators ranging in size from 29.7 cm to 348.0 cm (total length [TL]) were captured, and 48 subadult alligators were recaptured (<125 cm TL). As recaptured individuals were biased towards smaller individuals, recaptured subadult alligators were divided into two size classes: size class 1 (<50 cm) and size class 2 (50–125 cm). Mean growth rates for size class 1 were 32.4 cm/year and for size class 2 were 27.6 cm/year. For both size classes, mean body condition was 1.8. Overall, subadult alligators within our inland study area exhibited faster growth rates and lower body condition than most other populations studied throughout their range. Introduction Alligator mississippiensis Daudin (American Alligators) were listed as endangered in 1967 under the US Endangered Species Preservation Act; however, populations have recovered sufficiently to allow regulated harvest throughout most of their range (Groombridge 1987). Despite a tremendous volume of research on American Alligators, few long-term data exist on age and sex structure, growth rates, and size throughout their range (see Wilkinson and Rhodes 1997). Additionally, American Alligators are longlived (i.e., up to 80 years), reach sexual maturity at a minimum size rather than age, and experience differential growth rates (Brandt 1991, Dalrymple 1996, Deitz 1979, Hines et al. 1968, Wilkinson and Rhodes 1997). Although current alligator management strategies are suitable on short time scales, the additive or compensatory impacts of harvests upon alligator population age, size, and sex structure on longer time scales remain unknown. As opposed to other game species, where gender- and age-specific harvest regulations are 1Arthur Temple College of Forestry and Agriculture, Stephen F. Austin State University, Nacogdoches, TX 75965. 2Advanced Ecology, Ltd., Center, TX 75633. 3Texas Parks and Wildlife Department, Jasper, TX 75951. 4Division of Biological and Physical Sciences, Delta State University, Cleveland, MS 38751. *Corresponding author – saalfeldd@titan.sfasu.edu. 542 Southeastern Naturalist Vol.7, No. 3 adjusted annually, alligator harvest is less selective due to lack of sexual dimorphism and available hunting techniques. Therefore implementing habitat and/or harvest management strategies is likely more complicated than for other shorter-lived, rapidly growing species. Growth rates and morphological variability (e.g., condition) of American Alligators have been studied in wild populations in South Carolina (Brandt 1991, Wilkinson and Rhodes 1997), Louisiana (Chabreck and Joanen 1979, Elsey et al. 1992), and Florida (Dalrymple 1996, Deitz 1979, Hines et al. 1968, Jacobsen and Kushlan 1989, Temsiripong 1999). In general, alligator growth rates vary according to size class, gender, and geographic location (Brandt 1991, Dalrymple 1996, Deitz 1979, Hines et al. 1968, Wilkinson and Rhodes 1997). Specifically, growth-rate variability, even within similar size classes and genders from different geographic locations, results primarily from differences in resource availability [(Brandt 1991, Roots et at. 1991, Wilkenson and Rohodes 1997), habitat suitability (Brandt 1991, Dalrymple 1996, Deitz 1979, Jacobsen and Kushlan 1989, Rootes et al. 1991),] population density (Brandt 1991), growing season length (Brandt 1991), and salinity (Chabreck 1971, Rootes et al. 1991). Variability in any or all of these factors can impact alligator ecology and management, particularly if management schemes in one region rely upon data generated from areas or populations unrelated and geographically disjunct from populations of interest, where habitat and growth rates may not be similar. For example, in inland Texas, alligator harvest management strategies are based upon assumptions that inland and coastal alligators exist at similar densities and exhibit similar growth rates (Webb 2005). However, inland wetlands are more heterogeneous and less saline than coastal wetlands and are often dominated by bottomland hardwood forested wetlands, river and creek drainages, emergent wetlands, deep and shallow open water, and fl oating vegetation (Webb 2005). As resource availability, alligator densities, growing season length, and salinity generally vary between coastal and inland wetlands (Webb 2005), we hypothesized that growth rates and condition would also differ between these populations. Thus, the objectives of this study were to quantify and compare growth rates and body condition of inland alligators within east Texas to previous studies. Field Site Description This research was conducted within east Texas at the 5113-ha Angelina- Neches/Dam B Wildlife Management Area (Dam B WMA) in Jasper and Tyler counties, located at the confl uence of the Angelina River, Neches River, and B.A. Steinhagen Reservoir. A variety of habitats occur at Dam B WMA, including shallow open lake-emergent marsh, creek channels, river channels, deep open-water, and swamps/sloughs (Webb 2005). Dominant aquatic plants observed at Dam B WMA included Eichhornia crassipes, (Mart.) Solms (Common Water Hyacinth), Salvinia minima, Baker (Common Salvinia), Alternanthera philoxeroides, (Mart.) Griseb. (Alligator Weed), Hydrilla verticellata, (L. f.) Royle (hydrilla), Polygonum spp., L. (Smartweed), 2008 D.T. Saalfeld, K.K. Webb, W.C. Conway, G.E. Calkins, and J.P. Duguay 543 and Nelumbo lutea, Willd. (American Lotus). Dominant woody species included: Taxodium distichum, (L.) Rich. (Bald Cypress), Cephalanthus occidentalis, L. (Buttonbush), Salix nigra, Marshall (Black Willow), Triadica sebifera, (L.) Small (Chinese Tallow), Quercus nigra, L. (Water Oak), Quercus lyrata, Walter (Overcup Oak), Nyssa aquatica, L. (Water Tupelo), and Pinus spp. (pine species) (Godfrey and Wooten 1981). Methods Capture and handling During May–September 2003 and 2004, we captured, marked, and released alligators at Dam B WMA using several capture techniques (i.e., snake tongs, pole snares, hands, and swim in live traps; see Webb 2005 for complete description). Upon capture, alligators were restrained with duct tape, and each individual >50 cm in total length was sexed by cloacal examination (Chabreck 1963, Joanen and McNease 1978). Although Allsteadt and Lang (1995) developed techniques to sex alligators <50 cm, this technique was not used due to logistical constraints (i.e., minimization of handling time, poor lighting conditions due to all captures occurring at night, and small numbers of hatchlings captured). We measured the following morphological features for each individual: total length (TL, cm; ventral tip of snout to tip of tail), snout–vent length (SVL, cm; ventral tip of snout to proximal tip of vent), eye to nare length (cm), total head length (cm; dorsal tip of snout to distal part of head scute), tail girth (cm, circumference of tail directly behind rear legs), and mass (g). All length measurements were taken with a flexible tape measure, and masses were obtained from Pesola® hanging scales (Baar, Switzerland). We uniquely marked all captured alligators by at least two of the following: dorsal tail-scute removal, numbered Monel tags (#681 for alligators ≥152 cm and #1 Monel tags for alligators <152 cm), or passive integrated transponder (PIT) tags. We measured all the aforementioned morphological features for all recaptured alligators. We excluded all individuals recaptured within 12 days of initial capture from subsequent analyses in order to eliminate any measurement error resulting in negative growth. Recapture, growth rate, and body condition estimation We estimated growth rates using TL; SVL was not used since no significant tail loss was documented. As alligator growth rates are not constant (i.e., feeding and growth stops or slows during winter; Chabreck and Joanen 1979; Rootes et al. 1991), annual growth rates were adjusted according to growing season duration as indicated by air and water temperatures. To estimate alligator growing season length for our study sites, we collected average daily air temperature data from Jasper, TX (Webb 2005). Assuming that alligators at Dam B WMA grew after water temperatures rose above 20–23 °C (Brisbin et al. 1982, Coulson and Hernandez 1983), we estimated alligator growth days at Dam B WMA to be from 1 April–31 October, or 214 days (Webb 2005). Therefore, we calculated daily growth rates for each recaptured individual by dividing the change in TL by the number of growth 544 Southeastern Naturalist Vol.7, No. 3 days between captures. Daily growth rates were then extrapolated out to annual growth rates (cm/yr) by multiplying them by growing season length, or 214 days. Additionally, intrinsic growth rate variable (k), maximum attainable length (L∞), and age at maturity (assumed to be 1.83 m; Giles and Childs 1949, McIlhenny 1934, Joanen and McNease 1975, Klause 1984) were estimated through the construction of von Bertalanffy, Logistic, and Gompertz growth curves (Chabreck and Joanen 1979, Elsey et al. 1992, Jacobsen and Kushlan 1989). We fitted each growth curve similar to Fabens’ (1965) modification of a von Bertalanffy growth curve for mark/recapture data without known ages. We estimated values for k and L∞ by iterated least squares methods using nonlinear regression (PROC NLIN; SAS Institute 1999). We used Akaike’s Information Criterion (AIC) to select the best, parsimonious growth curve to fit our data (Akaike 1973). Condition (K; Le Cren 1951), an index of the relative fatness of an animal and also an indicator of its well being/health (Taylor 1979), was estimated from the relationship between length and mass using the equation: K = M * L-b, where M = mass (g), L = total length (cm) and b = slope of the regression of ln (TL) and ln (M). If growth is isometric, b would be approximately equal to 3. Data analysis We used analysis of variance (ANOVA; PROC GLM; SAS Institute 1999) to examine differences in growth rates and body condition among size classes (size class 1 = <50 cm, size class 2 = 50–125 cm, size class 3 = 125.1–160 cm, and size class 4 = >160 cm) and between sexes, where sufficient sample sizes of recaptured individuals were available. For growth rates analysis, only size class 1 and size class 2 were used because only one individual from a larger size class was recaptured. An alpha level of 0.05 was used for this analysis, and least squared means separation was used to examine differences (P < 0.05). Results We captured, measured, marked, and released 279 alligators ranging in size from 29.7 cm to 348.0 cm (TL; Fig. 1) at Dam B WMA from 12 May– 18 August, 2003, and 15 April–9 September, 2004. We captured alligators using tongs (n = 116), hand grabbing (n = 67), walk-in cage traps (n = 57), pole snares (n = 35), and other methods (i.e., dowel sets, n = 4). During this time, we recaptured 49 individuals, 48 of which were sub-adults (<125 cm TL). Only one adult (>183 cm in TL) was recaptured and was excluded from further analyses. Mean growth rate for recaptured alligators <125 cm was 29.39 cm/yr (SE = 2.5), irrespective of size class and sex. Overall growth rates decreased as size increased for alligators <125 cm (y = -0.259x + 42.516, r2 = 0.594; Fig. 2). Growth rates were similar (F1, 46 = 0.83, P = 0.368) between size class 1 (mean = 32.38 cm/yr, SE = 3.0; n = 18) and size class 2 (mean= 27.59 cm/yr; SE = 3.7; n = 30). Additionally, growth rates were similar (F1, 44 = 1.00, P = 0.322) between sexes. Based on AIC, the best growth model for our pooled data was 2008 D.T. Saalfeld, K.K. Webb, W.C. Conway, G.E. Calkins, and J.P. Duguay 545 von Bertalanffy (Table 1), therefore all further analyses used this model. The modified von Bertalanffy growth curve (Fig. 3) fitted to our mark/recapture data provided an estimate of 258.9 cm for L∞ and 0.00606 for k, where we estimated time to maturity for alligators in our study area to be 10 years. Overall mean condition for all size classes and sexes combined was 1.84 (SE = 0.06; Fig. 4). Condition ranged from 1.46 to 2.97, depending upon size class (Table 2), and were similar between sexes (F1, 104 = 0.34, P = 0.710). However, condition for size class 4 individuals was (marginally) higher (F3, 104 = 2.78, P = 0.045) than any other size class, and condition was similar among individuals within size classes 1–3 (P > 0.05). Figure 1. Length frequencies of American Alligators (Alligator mississippiensis) captured, marked, and released at Angelina- Neches/ Dam B Wildlife M a n a g e m e n t Area, TX, May– September, 2003 and 2004. Figure 2. Mean growth rates (cm/year) of recaptured American Alligators (Alligator mississippiensis) by total length (10- cm size classes) caught from Angelina- Neches/ Dam B Wildlife M a n a g e m e n t Area, TX, May– September 2003 and 2004. 546 Southeastern Naturalist Vol.7, No. 3 Discussion Subadult alligators (i.e., individuals <125 cm in TL) grew faster in this study (29.39 cm/yr) than subadults in the Shark Valley region of Florida (13.3 cm/yr in Jacobsen and Kushlan [1989], 13.6 cm/yr in Dalrymple [1996]), north Florida (11.9–21.1 cm/yr in Deitz [1979], 24.0 cm/yr in Temsiripong [1999]), South Carolina (14.6 cm/yr in Bara [1977], 23.5 cm/ yr in Brandt [1991], 18.0–20.2 cm/yr in Wilkinson and Rhodes [1997]), and Louisiana (22.0 cm/yr in Chabreck and Joanen [1979]), but grew at rates similar to alligators north of Shark Slough, FL (31.0 cm/yr in Hines et al. Table 1. Akaike’s Information Criterion (AIC), intrinsic growth rate variable (k), and maximum attainable length (L∞) for each growth curve fitted to American Alligator (Alligator mississippiensis) mark/capture data from Angelina-Neches/Dam B Wildlife Management Area, TX, during May–September 2003 and 2004. Model AIC L∞ k von Bertalanffy 1154 258.9 0.006 Logistic 1363 140.0 0.004 Gompertz 13,844 116.8 -0.084 Figure 3. Length-at-age relationships (± standard error) derived from fitting a von Bertalanffy growth curve to mark/recapture data of American Alligators (Alligator mississippiensis) from Angelina-Neches/Dam B Wildlife Management Area, TX, collected from May–September 2003 and 2004. 2008 D.T. Saalfeld, K.K. Webb, W.C. Conway, G.E. Calkins, and J.P. Duguay 547 [1968]). Additionally, subadult alligators at Dam B WMA grew faster (29.39 cm/yr) than subadults at Mad Island WMA in coastal Texas (14.0–16.0 cm/ yr; M.T. Merendino, Texas Parks and Wildlife, Austin, TX, pers comm.). Although subadult alligators grew faster in this study, overall condition for subadults (mean = 1.79) and all size classes combined (mean = 1.84) were lower than estimated alligator condition for all size classes in Florida (2.5 in Temsiripong [1999], 2.7 in Rice [2004]). Although sample size of recaptured individuals was small for this study, our results corroborate past studies suggesting that geographic variation has Figure 4. Condition factors of American Alligators (Alligator mississippiensis) captured, marked, and released from Angelina-Neches/Dam B Wildlife Management Area, TX, during May–September 2003 and 2004 by total length. Table 2. Means and standard errors for body condition of (K) American Alligators (Alligator mississippiensis) captured, marked, and released from Angelina-Neches/Dam B Wildlife Management Area, TX, during May–September 2003 and 2004 by size class. Size class Size range (cm) Mean K Standard error 1 <50 1.76 0.25 2 50–125 1.82 0.07 3 125.1–160 1.73 0.05 4 >160 2.84 0.68 548 Southeastern Naturalist Vol.7, No. 3 an important infl uence on both growth rates and condition. Some causes of geographic variability have been attributed to resource (food) availability (Brandt 1991, Dalrymple 1996, Deitz 1979, Jacobsen and Kushlan 1989, Rootes et al. 1991), habitat (Brandt 1991, Rootes et al. 1991, Wilkinson and Rhodes 1997), growing season length (Brandt 1991) and population densities (Brandt 1991; M.T. Merendino, pers comm.). Although resource availability was not examined during this study, current studies are examining prey selection and densities to directly estimate their infl uence on growth rates and condition within inland wetlands of east Texas. As suggested from previous studies (Rootes et al. 1991, Webb 2005), substantially different habitat (i.e., shallow open lake-emergent marsh, creek channels, river channels, deep open-water, and swamps/sloughs) combined with lower alligator densities at Dam B as compared to coastal habitats likely contributed to faster growth. Alligator density at Dam B WMA was estimated to be approximately 7.5 ha/alligator (1.52–2.35 alligators/km; K.K. Webb et al., unpubl. data), lower than the 3.2–5.7 ha/alligator reported in coastal Louisiana (McNease and Joanen 1978) and the 2.56–9.02 alligators/km reported in Florida (Wood et al. 1985). Although no studies have specifically tested the infl uence of population densities on growth rates in alligators, others have speculated that growth rates are density dependent (Brandt 1991, Webb 2005). For example, if alligators exist at relatively high densities, and food resources are limiting, competition for food may increase competition among alligators leading to decreased growth rates. Schoener and Schoener (1978) documented density-dependant growth in Anolis lizards, with growth rates being directly correlated with population density in their study. Jacobsen and Kushlan (1989) suggest slower growth could affect an alligator’s age to sexual maturity and increase its susceptibility to predation, disease, and cannibalism. Due to the higher growth rates documented at Dam B WMA, time to sexual maturity (10 years) was shorter than the estimated 13–17 years for South Carolina (Murphy and Fuller 1982) and 13–18 years for the Everglades (Dalrymple 1996, Jacobsen and Kushlan 1989), but similar to the estimated 8–10 years in Louisiana (Joanen and McNease 1975, 1987). Despite this shorter time to sexual maturity in east Texas, if alligators are in poor condition when they reach maturity, they may be unable to reproduce and compete for limited resources (e.g., optimum nesting sites and prey). This consideration could have important management implications in terms of long-term viability of alligator populations, particularly those exposed to regulated hunting pressures. To date, few studies have focused on inland populations of American Alligators, especially in Texas. This study indicates there may be important geographic differences in age at maturity, condition, and growth rates within subadult alligators between inland and coastal populations. Such differences could have dramatic effects on alligator population parameters such as recruitment, survival, and overall population size and age characteristics. Thus, it may be necessary to modify current management strategies between inland and coastal populations as such variability in basic life-history parameters likely requires geographically or regionally specific management guidelines. 2008 D.T. Saalfeld, K.K. Webb, W.C. Conway, G.E. Calkins, and J.P. Duguay 549 Acknowledgments Financial, logistical, and technical support was provided in part by the Texas Parks and Wildlife Department and McIntire-Stennis funds through the Arthur Temple College of Forestry and Agriculture, Stephen F. Austin State University. Special appreciation to the staff of Martin Dies Jr. State Park, R. McFarlane, T. Anderson, and K.J. Lodrigue for additional logistical, financial, and technical support. Thanks to B. Koerth, V. Dowden, D. Cantu, S. Crook, C. Anderson, and A. Webb and all others who assisted with this field work. Thanks to T.P. Wilson and the two anonymous reviewers for their comments and corrections on this manuscript. Literature Cited Akaike, H. 1973. Information theory and an extension of the maximum likelihood principle. Pp. 267–281, In B.N. Petrov and F. Caski (Eds.). Second International Symposium on Information Theory. Akademiai Kiado, Budapest, Hungary. Allsteadt, J., and J.W. Lang. 1995. Sexual dimorphism in the genital morphology of young American Alligators, Alligator mississippiensis. Herpetologica 51:314–325. Bara, M.O. 1977. American Alligator investigations. South Carolina Wildlife and Marine Resources Department, Columbia, SC. 40 pp. Brandt, L.A. 1991. Growth of juvenile alligators in Par Pond, Savannah River Site, South Carolina. Copeia 1991:1123–1129. Brisbin, I.L., Jr., E.A. Standora, and M.J. Vargo. 1982. Body temperatures and behavior of American Alligators during cold winter weather. The American Midland Naturalist 107:209–218. Chabreck, R.H. 1963. Methods of capturing, marking, and sexing alligators. Proceedings of the Southeastern Association of Game and Fish Commissioners 17:47–50. Chabreck, R.H. 1971. The foods and feeding habits of alligators from fresh and saline environments in Louisiana. Proceedings of the Southeastern Association of Game and Fish Commissioners 25:117–123. Chabreck, R.H., and T. Joanen. 1979. Growth rates of American Alligators in Louisiana. Herpetologica 35:51–57. Coulson, R.A., and T. Hernandez. 1983. Alligator metabolism. Studies on chemical reactions in vivo. Comparative Biochemical Physiology B 74:1–182. Dalrymple, G.H. 1996. Growth of American Alligators in the Shark Valley Region of Everglades National Park. Copeia 1996:212–216. Deitz, D.C. 1979. Behavioral ecology of young American Alligators. Ph.D. Dissertation, University of Florida, Gainesville, FL. 152 pp. Elsey, R.M., T. Joanen, L. McNease, and N. Kinler. 1992. Growth rates and body condition factors of Alligator mississippiensis in coastal Louisiana wetlands: A comparison of wild and farm-released juveniles. Comparative Biochemistry and Physiology 103A:667–672. Fabens, A.J. 1965. Properties and fitting of the von Bertalanffy growth curve. Growth 29:265–286. Giles, L.W., and V.L. Childs. 1949. Alligator management of the Sabine National Wildlife Refuge. Journal of Wildlife Management 13:16–28. Godfrey, R.K., and J.W. Wooten. 1981. Aquatic and Wetland Plants of Southeastern United States. University of Georgia Press, Athens, GA. 933 pp. Groombridge, B. 1987. The distribution and status of world crocodilians. Pp. 9–21, In G.J.W. Webb, S.C. Manolis, and P.J. Whitehead (Eds.). Wildlife Management: Crocodiles and Alligators. Surrey Beatty and Sons, NSW, Australia. 550 Southeastern Naturalist Vol.7, No. 3 Hines, T.C., M.J. Fogarty, and L.C. Chappell. 1968. Alligator research in Florida: A progress report. Proceedings of the Southeastern Association of Game and Fish Commissioners 22:166–180. Jacobsen, T., and J.A. Kushlan. 1989. Growth dynamics in the American Alligator (Alligator mississippiensis). The Journal of Zoology 219:309–328. Joanen, T., and L. McNease. 1975. Notes on the reproductive biology and captive propagation of the American Alligator. Proceedings of the Southeastern Association of Game and Fish Commissioners 29:407–414. Joanen, T., and L. McNease. 1978. The cloaca sexing method for immature alligators. Proceedings of the Annual Conference of the Southeastern Association of Fish and Wildlife Agencies 32:179–181. Joanen, T., and L. McNease. 1987. Alligator farming research in Louisiana, USA. Pp. 329–340, In G.J.W. Webb, S.C. Manolis, and P.J. Whitehead (Eds.). Wildlife Management: Crocodiles and Alligators. Surrey Beatty and Sons, NSW, Australia. Klause, S. 1984. Reproductive characteristics of the American Alligator (Alligator mississippiensis) in North Carolina. M.Sc. Thesis. North Carolina State, Raleigh, NC. 85 pp. Le Cren, E.D. 1951. The length-weight relationship and seasonal cycle in gonad weight and condition in Perch (Perca fl uviatilis). The Journal of Animal Ecology 20:201–219. McIlhenny, E.A. 1934. Notes on incubation and growth of alligators. Copeia 1934:80–88. McNease, L., and T. Joanen. 1978. Distribution and relative abundance of the alligator in Louisiana coastal marshes. Proceedings of the Annual Conference of the Southeastern Association of Fish and Wildlife Agencies 32:182–186. Murphy, T.M., and J.C. Fuller. 1982. American Alligator investigations, management recommendations, and current research. South Carolina Wildlife and Marine Resources Department, Columbia, SC. 93 pp. Rice, A.N. 2004. Diet and condition of American Alligator (Alligator mississippiensis) in three central Florida lakes. M.Sc. Thesis. University of Florida, Gainesville, FL. 88 pp. Rootes, W.L., R.H. Chabreck, V.L. Wright, B.W. Brown, and T.J. Hess. 1991. Growth rates of American Alligators in estuarine and palustrine wetlands in Louisiana. Estuaries 14:489–494. SAS Institute. 1999. SAS/STAT software, version 9. SAS Institute, Inc, Cary, NC. Schoener, T.W., and A. Schoener. 1978. Estimating and interpreting body-size growth in some Anolis lizards. Copeia 1978:390–405. Taylor, J.A. 1979. The foods and feeding habits of subadult Crocodylus porosus Schneider in northern Australia. Australian Wildlife Research 6:347–359. Temsiripong, Y. 1999. Growth and survival rates of wild and repatriated hatchling American Alligators (Alligator mississippiensis) in Central Florida lakes. M.Sc. Thesis. University of Florida, Gainesville, FL. 55 pp. Webb, K.K. 2005. Population ecology and habitat use of American Alligators in inland freshwater wetlands of east Texas. M.Sc. Thesis. Stephen F. Austin State University, Nacogdoches, TX. 122 pp. Wilkinson, P.M., and W.E. Rhodes. 1997. Growth rates of American Alligators in coastal South Carolina. Journal of Wildlife Management 61:397–402. Wood, J.M., A.R. Woodward, S.R. Humphrey, and T.C. Hines. 1985. Night counts as an index of American Alligator population trends. Wildlife Society Bulletin 13:262–273.