The distribution of the Broad-Snouted Caiman (Caiman latirostris) ranges from 5°S to 32°S. Thus, caiman populations are exposed to different climatic conditions, and this latitudinal gradient could affect aspects of their reproduction. In this study we present evidence that there is a positive relationship between clutch size and latitude. A possible effect of smaller clutch size  on populations from low latitudes could be increased nesting frequency, thus improving female fitness.Fil: Simoncini, Melina Soledad. Proyecto Yacaré; Argentina. Provincia de Entre Ríos. Centro de Investigaciones Científicas y Transferencia de Tecnología a la Producción. Universidad Autónoma de Entre Ríos. Centro de Investigaciones Científicas y Transferencia de Tecnología a la Producción. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Centro de Investigaciones Científicas y Transferencia de Tecnología a la Producción; ArgentinaFil: Piña, Carlos Ignacio. Proyecto Yacaré; Argentina. Provincia de Entre Ríos. Centro de Investigaciones Científicas y Transferencia de Tecnología a la Producción. Universidad Autónoma de Entre Ríos. Centro de Investigaciones Científicas y Transferencia de Tecnología a la Producción. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Centro de Investigaciones Científicas y Transferencia de Tecnología a la Producción; ArgentinaFil: Siroski, Pablo Ariel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Proyecto Yacaré; Argentina. Dirección General de Manejo Sustentable de Fauna y Flora; Argentin

Piña, Carlos Ignacio

Simoncini, Melina Soledad

Siroski, Pablo Ariel

English

LAReferencia - Red Federada de Repositorios Institucionales de Publicaciones Científicas Latinoamericanas

North-Western Journal of Zoology                                                                      Vol. 5, No. 1, 2009, pp.191-196 P-ISSN: 1584-9074, E-ISSN: 1843-5629                                                                                                 Article No.: 051201  Clutch size of Caiman latirostris (Crocodylia: Alligatoridae)  varies on a latitudinal gradient  Melina S. SIMONCINI1,2,*, Carlos I. PIÑA1,2   and   Pablo A. SIROSKI1,3   1. Proyecto Yacaré (Gobierno de la Provincia de Santa Fe / MUPCN), A. del Valle 8700, (3000) Santa Fe, Argentina.  2. CIC y TTP – CONICET, Proyecto Yacaré. Fac. Cs. y Tec., UAdER. Dr. Matteri y España, (3105) Diamante,  Entre Ríos. Argentina. E-mail: melinasimoncini22@yahoo.com.ar  3.  Dirección General de Manejo Sustentable de Fauna y Flora (M.A.S.P. y M.A).  Provincia de Santa Fe, (3000) Argentina. E-mail: psiroski@santafe.gov.ar * Corresponding Author: M. Simoncini, E-mail: melinasimoncini22@yahoo.com.ar   Abstract. The distribution of the Broad-Snouted Caiman (Caiman latirostris) ranges from 5°S to 32°S. Thus, caiman populations are exposed to different climatic conditions, and this latitudinal gradient could affect aspects of their reproduction. In this study we present evidence that there is a positive relationship between clutch size and latitude. A possible effect of smaller clutch size on populations from low latitudes could be increased nesting frequency, thus improving female fitness.   Key-words: Broad Snouted Caiman, Latitude, Reproductive frequency,     Crocodilian reproduction, Fitness    Caiman latirostris (Broad-Snouted Caiman) has a broad latitudinal distribution in South America from 5°S to 32°S. This species is found in Argentina, Bolivia, Brazil, Para-guay, and Uruguay (Verdade et al. in press). In Argentina, the northernmost populations of Caiman latirostris are located in Formosa province; on the other hand, the southern-most distribution of the species is Santa Fe province (31ºS; Piña et al. 2004) (Fig. 1). Caiman populations inhabitating this latitudinal range are exposed to different weather conditions (Table 1). From Santa Fe city (31° 35’S, 60° 11’W) to Formosa city (26° 11’S, 58° 10’W) there are 650 Km in a South – North direction. Thus, Broad-Snouted Caiman populations are exposed to differences in winter intensity in this latitudinal gradient. Moreover, it is possible that this decrease in temperatures could be the cause of the southern distribution limit of the species in Argentina (Siroski 2004), reducing the length of the high temperature period for reproduction or somatic growth, as reported by Lance (2003) for American alligators Alligator mississippiensis. Larriera (1991, 1994) and Verdade (1995, 1997) have reported differences in clutch size of C. latirostris, in different geographical areas (Santa Fe province, Argentina; and São Paulo state, Brazil). Clutch sizes from Santa Fe were larger, but the origin of the studied nests was not similar; the ones from Argentina came from wild populations, and the Brazilian ones were collected in captivity. However, variation in clutch size within a latitudinal range in crocodilians was previously described for Alligator  ©NwjZ, Oradea, Romania, 2009                                                                                                                                 North-West J Zool, 5, 2009 www.herp-or.uv.ro/nwjz                                                                                                                                                              Oradea, Romania Simoncini, M.S. et al. 192 mississippiensis (Wilkinson 1983). In the present study, we evaluated the effects of latitude on C. latirostris clutch size from wild populations in Argentina.    Figure 1.  Map with the distribution of Caiman latirostris (grey) and the 17 localities included in the study.  North-West J Zool, 5, 2009 Caiman latirostris clutch size varies with latitude 193  Table 1.  Table of weather caracteristics of  Formosa, Corrientes and Santa Fe province (data was obtained from Servicio Meteorológico Nacional Web page: www.smn.gov.ar).  Province Weather Mean Annual Temperatures Annual Rainfall Formosa Continental subtropical 29.5ºC to 16.6ºC 940mm (concentrated in the winter) Corrientes Warm and wet 25.7ºC to 17.1ºC few colds days 1600mm (rains occurs througout the year) Santa Fe Subtropical 25.6ºC to 14.9ºC high temperatures during summer and periods of frost during winter  1380mm (mostly during summer)    For this study, we used a database on 587 natural nests of C. latirostris collected between December 2004 and February 2005, by the ranching programs “Caimanes de Formosa” (n = 177 nests, from 6 localities of Formosa province), “Yacaré Porá” (n = 153 nests, from 3 localities of Corrientes province) and “Proyecto Yacaré” (n = 257 nests, from 8 localities of Santa Fe province) (Fig. 1). In the database we included all the nests that presented no signs of depredation in order to avoid clutch size underesti-mation. In order to check for a connection between clutch size (number of eggs per clutch) and latitude we used a simple regression model. As independent variable we used latitude (expressed as degree with decimals) of each one of the 17 localities from where we have collected nests. Clutch size was calculated as the average from all the nests harvested in each location. Our alpha value for significance was 0.05. As expected, clutch size in “Teuquito” locality (lower latitude, Formosa province) was 30.0 eggs/nest (SD: 6.7; CI: 16-41), whereas in locality “114” (higher latitude, Santa Fe province) was 37.7 eggs/nest (SD: 4.9; CI: 32-45). We found a positive linear relationship between latitude and clutch size (P = 0.0048; R2= 0.42; b= 0.99; Fig. 2). If we consider the average for each province, we obtained for Santa Fe province 33.1 eggs/nest (SD: 5.9; CI: 16-45), Corrientes province 30.6 eggs/nest (SD: 6.3; CI: 14-44) and Formosa province 29.6 eggs/nest (SD: 6.4; CI: 14-43).  Clutch size from higher latitude localities was larger than for the lower latitude ones (Fig. 2), even considering that mean clutch size from the eight localities within Santa Fe province were smaller than clutch sizes previously reported in other works (37 eggs/nest; Larriera 1991). Consi-dering previous works in the same habitats in Santa Fe province, we have found an historical reduction on C. latirostris clutch size (37 eggs/nest in 1991, n= 12, Larriera 1991; 34,9 eggs/nest in 2001/2, n= 154, Montini et al. 2006; and 33.3 eggs/nest in 2005, n= 257), this could be explained by the reintroduction work done by the ranching program “Proyecto Yacaré”, resulting in the increase of young females in the breeding stock of wild populations in Santa Fe. Larriera et al. (2006) reported the capture of females of nine and ten years old, reintroduced in the wild by Proyecto Yacaré  North-West J Zool, 5, 2009 Simoncini, M.S. et al. 194 (MUPCN/Gobierno de la provincia de Santa Fe), attending nests. There are reports that in some crocodilians, female size is related to clutch size, larger females pro-ducing greater clutch sizes (Thorbjarnarson 1996; Larriera et al. 2004). Therefore we assumed that the differences related to the latitudinal gradient found in this work, could be even larger if we compare a popu-lation where no animals have been reintro-duced. In our study we found a relationship between the variables clutch size and latitude; the model explained 42% of clutch size variation. Previous studies mentioned that population density, female nutritional status, age and size, weather variables like rainfall and toxic contaminant levels could affect clutch size (Woodward et al. 1993; Larriera et al. 2004; Simoncini et al. 2008) in crocodilians. But our results showed a lati-tudinal effect on clutch size of C. latirostris, as reported for Alligator mississippiensis (Wilkinson 1983), the spotted turtle (Clemmys guttata; Litzgus & Mousseau 2006), and birds (Symonds et al. 2006). Population density, adult nutritional status or toxic contaminant levels were not measured in this work, we consider these effects to be randomly distributed because we worked with many sampling areas in the three provinces.      Figure 2. Relationship between clutch size of Caiman latirostris and latitude. Numbers 1 to 3 represent localities within Corrientes province; 4 to 11 localities within Santa Fe province; 12 to 17 localities within Formosa province.    North-West J Zool, 5, 2009 Caiman latirostris clutch size varies with latitude 195  In conclusion, clutch size in C. latirostris increases with latitude. C. latirostris females from lower latitudes, with smaller clutches but similar-sized eggs as higher latitudes females (A. Larriera pers. comm.) could have the same reproductive output by increasing nesting frequency (Litzgus & Brooks 1998). This would be an advantage in females’ fitness and for the surviving cohorts since a higher nesting frequency would increase the chances of laying eggs during good years (Madsen & Shine 1998).    Acknowledgements: We would like to thank other members of Proyecto Yacaré: Amavet, P., Fernández, L., Imhof, A., Iungman, J., Larriera, A., Nuñez, N., Parachú, V., Poletta, G., Principe, G. for their help. This study was supported by Proyecto Yacaré, Yacarés Santafesinos (Gob. de la Pcia. de Santa Fe / MUPCN), PIP 6375 and PICT 2005 N°31679. We thank to other caiman projects and theirs members: Yacaré Porá – Corrientes (Mauro Cardozo) and Caimanes de Formosa – Formosa (César Perez), for their valuable work. We appreciate comments on the previous versions of the MS and English improvement made by Allan Woodward and Mark Merchant and anonymous reviewers. M.S. is a doctoral fellow from CONICET. This is publications number 76 from Proyecto Yacare     References  Lance, V. A. (2003): Alligator physiology and life history: the importance of temperature. Experimental Gerontology 38: 801-805. Larriera, A. (1991): Clutch size and hatching success in Broad-Snouted Caiman, Caiman latirostris (Crocodylia, Alligatoridae), in Santa Fe province, Argentina. Revista de la Asociación de Ciencias Naturales del Litoral 22: 19-23. Larriera, A. (1994): Tamaño de postura y éxito reproductivo de yacarés (Caiman latirostris) en Santa Fe, Argentina. Vida Silvestre Neotropical 3: 118-119. Larriera, A., Piña C. I., Siroski P., Verdade, L. (2004): Allometry of reproduction in wild Broad-Snouted Caimans (Caiman latirostris). Journal of Herpetology 38: 301-304. Larriera, A., Siroski P., Piña C. I., Imhof, A. (2006): Sexual maturity of farm-released Caiman latirostris (Crocodylia: Alligatoridae) in the wild. Herpetological Review 37: 26-28. Litzgus, J. D., Brooks R. J. (1998): Reproduction in a northern population of Clemmys guttata. Journal of Herpetology 32: 252-259. Litzgus, J. D., Mousseau, T. (2006): Geographic variation in reproduction in a fresh water turtle (Clemmys guttata). Herpetologica 62: 132-140. Madsen, T., Shine R. (1998): Quantity or quality? Determinants of maternal reproductive success in tropical pythons (Liasis fuscus). Proceeding of  The Royal Society London Bulletin 265: 1521–1525. Montini, J. P., Piña, C.I., Larriera, A., Siroski, P., Verdade, L.M. (2006): The relationship between nesting habitat and hatching success in Caiman latirostris (Crocodylia, Alligatoridae). Phyllomedusa 5(2): 91-96. Departamento de Ciências Biológicas – ESALQ – USP. Piña, C. I., Larriera, A., Siroski, P. (2004): Cocodrilos en la región Litoral: especies, distribución geográfica, modo de vida. Temas de la Biodiversidad del Litoral argentino INSUGEO, Miscelánea 12: 317-322. Simoncini, M., Piña, C. I., Larriera, A. (in press): Rainfall effect on the reproduction of Caiman latirostris (Crocodylia: Alligatoridae). Crocodiles. Proceedings of the 19th Working Meeting of the Crocodile Specialist (CSG/SSC/IUCN). Santa Cruz de las Sierras, Bolivia. Siroski, P. (2004): Relevamiento de las poblaciones del género Caiman en la provincia de Formosa (segundo informe). Informe anual de la Dirección de Fauna y Parques de la Provincia de Formosa (Ministerio de la Producción), Argentina. pp. 14.  Symonds, M. R. E., Christidis, L., Johnson, C. N. (2006): Latitudinal gradients in abundance, and the causes of rarity in the tropics: a test using Australian honeyeaters (Aves: Meliphagidae). Oecologia 149: 406–417. Thorbjarnarson, J. (1996): Reproductive characteristics of the order crocodylia. Herpetologica 52: 8-24. Verdade, L. M. (1995): Biología reproductiva do jacaré-de-papo-amarelo (Caiman latirostris) em Sao Paulo, Brasil pp. 57-74. In: Larriera, A., Verdade, L. M. (eds.) La Conservación y el Manejo de Caimanes y Cocodrilos en América Latina. Vol.1. Fundación Banco Bica, Santo Tomé, Argentina. Verdade, L. M. (1997): Morphometric Analysis of the Broad-Snouted Caiman (Caiman latirostris): An Assessment of Individual Clutch, Body Size, Sex,  North-West J Zool, 5, 2009 Simoncini, M.S. et al. 196 Age, and Area of Origin. Ph. D. Dissertation, University of Florida, Gainsville, FL, USA. pp.174. Verdade, L. M., A. Larriera, C. I. Piña. (in press): Caiman latirostris. In: Crocodiles. Status Survey and Conservation Action Plan 3rd Edition. Crocodile Specialist Group, IUCN, Gland, Switzerland.  Wilkinson, P. M. (1983): Nesting Ecology of the American Alligator in Coastal South Carolina. South Carolina Wildlife and Marine Resources Department, Study Completion Report. pp.113. Woodward, A. R., Franklin Percival, H., Jennings, M. L., Moore, C. T. (1993): Low clutch viability of American alligators on Lake Apopka. Florida Scientist 56: 52-63.    Submitted: 03 March  2008 /  Accepted: 07 December 2008   Published Online: 02 January  2009   North-West J Zool, 5, 2009 

Clutch size of Caiman latirostris (Crocodylia: Alligatoridae) varies on a latitudinal gradient

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Clutch size of Caiman latirostris (Crocodylia: Alligatoridae) varies on a latitudinal gradient

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