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Journal ArticleDOI

Turtle Populations in Louisiana

01 Mar 1950-American Midland Naturalist-Vol. 43, Iss: 2, pp 383
TL;DR: Analysis of the significance of aquatic turtle populations in fresh water requires information on the abundance and habitat preferences of each species, and trap results are the best basis for determining relative abundance.
Abstract: The role of turtle populations in fresh water biology has been generally ignored although these animals may, in some areas, be the dominant vertebrates. Available information is inadequate to define precisely the relation of any turtle population to that of another animal. Analysis of the significance of aquatic turtle populations in fresh water requires information on the abundance and habitat preferences of each species. Trapping provides the best basis for estimating this information. Traps are unsatisfactory in that they are selective for certain size groups of each species and catches vary with the type of bait, method of set, water temperature, and water depth. Too, the first individual to enter a trap may determine the nature of the total catch. Thus a large Chelydra or Macrochelys in a trap will often prevent others from entering, and a female will attract males during the periods of sexual activity. Such factors must be considered when utilizing trap returns in population studies. Hand collecting tends to produce an abundance of Pseudemys, Chrysemys, and Graptemys but few A myda, Macrochelys, or Chelydra. Regardless of these factors in trapping, which cannot be evaluated at present, trap results are the best basis for determining relative abundance. Turtle traps were operated in 14 water bodies in Louisiana during the summer of 1947 (Fig. 1). The traps were made of 1" square mesh netting suspended on three 36" diameter steel hoops. An adjustable net throat was attached at one end and a draw string outlet at the other. Bamboo poles were used to spread the three hoops and to hold the traps in place. Bait (fresh gar, bowfin, catfish) was suspended in a can just in front of the open throat.
Citations
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Journal ArticleDOI
01 Jan 1965-Ecology
TL;DR: The effect of light intensity and incidence angle, water and air temperatures, wind, and cloud cover upon rates of heat gain in turtles were investigated, and all were found to have importance.
Abstract: A combined field and laboratory study was conducted to assess the biological implications of the basking habit in turtles. The effect of light intensity and incidence angle, water and air temperatures, wind, and cloud cover upon rates of heat gain in turtles were investigated, and all were found to have importance. Biological factors of importance are behavior, shape, weight, and rarely, color; sex and species were not important except as they affect the other factors. A series of motivation studies was conducted to identify the environmental factors initiating and directing basking. The taxonomic incidence of the basking habit in turtles is discussed. Basking serves primarily as a method of thermal control, with secondary benefits in drying of the skin and shell. See full-text article at JSTOR

192 citations

Journal ArticleDOI
01 Jan 1975-Ecology
TL;DR: A mark—recapture study of a population of painted turtles, Chrysemys picta, started by O. J. Sexton between 1953 and 1957 and continued between 1968 and 1973, interpreted as an adaptation to a highly uncertain probability of nest success and an effective predator defense in the adult stage.
Abstract: A mark—recapture study of a population of painted turtles, Chrysemys picta, started by O. J. Sexton between 1953 and 1957 was continued between 1968 and 1973. Life tables are constructed and a demographic history of the population is suggested. Males mature during their 4th yr and first breed at age five. Females mature at age seven and lay two clutches of about 6 to 7 eggs each year. Mortality is about 92% between laying and the arrival of the hatchlings at the pond. Juvenile and adult mortality is at a constant exponential rate of about 0.15 for males and 0.18 for females each year. Raccoons, Procyon lotor, are an important predator during spring migrations. There is no indication of senescence; females over 30 yr old are still reproductive. Between 1954 and 1972 the population's size has been reduced from an estimated 981 to about 186 animals. This has been accompanied by a decrease in mean generation time from 12.35 to 10.70 yr. Survivorship from laying to arrival at the pond has more than doubled, but adult survivorship has decreased. These changes are attributed to an increased predation rate resulting from a reduction in the number of safe basking sites. A hypothetical population was simulated by recurrent use of a population projection matrix, derived from the 1954 life table, to demonstrate the stability characteristics of this long—lived, iteroparous species. The evolution of this life history is interpreted as an adaptation to a highly uncertain probability of nest success and an effective predator defense in the adult stage.

166 citations

Journal ArticleDOI
TL;DR: This study indicates that even within a species, trapping method introduces considerable bias in the estimation of sex ratio and size-class distribution of painted turtles, as estiimated by different authors.
Abstract: A natural population of painted turtles [Chrysemys picta (Schneider)] was studied in University Bay of Lake Mendota, Dane County, Wisconsin, from September 1960 to October 1962. Five methods were used to capture turtles for marking, measurement, and release. Each of the methods yielded a different size-class distribution and a sex ratio which, in four out of five cases, was significantly different from that of the total population estimate. Baited hoop nets yielded predominantly males and relatively few juveniles; basking traps tended to yield higher percentages of females than did nets, and large turtles were an important component of the sample. Hand capture resulted in a sample heavily weighted by juveniles and a 1: 1 sex ratio for adults. The influence of trapping method in the estimation of population structure in turtles must not be overlooked. This study indicates that even within a species, trapping method introduces considerable bias in the estimation of sex ratio and size-class distribution. INTRODUCTION The structure of turtle populations, as estiimated by different authors (Cagle, 1942, 1944, 1954; Pearse, 1923; Sexton, 1959), has varied considerably even within the same species. Although this variation may be due to inherent differences in the populations studied, or to various ecological factors affecting each population with different intensities, it is more probable that the disparity lies in the sampling method used by the investigators. Cagle and Chaney (1950) suggested that sampling methods are biased by the behavioral patterns of the size classes and sexes that make up the population, but we are unaware of any study that has compared the variation in estimation of population and its strutcture brought about by use of different sampling methods. A natural population of Chrysemys picta (Schneider) was studied in University Bay of Lake Mendota, Dane County, Wisconsin, from September 1960 to October 1962. The central painted turtle, Chrysemys picta marginata (Agassiz) and the western painted turtle, Chrysemys picta belli (Gray) intergrade in this region (Pope, 1949). Five methods were used to capture a maximum number of turtles for marking, measurement, and release. Variant results obtained from use of these methods were sufficiently striking to, warrant a comparison of the methods. Acknowledgments.-This study was done with the aid of two NSF Summer Fellowships for Teaching Assistants. Additional financial assistance for field equipment and limited field assistance was provided by a grant to Dr. W. G. Reeder from the Wisconsin Alumni Research Foundation through the University of Wisconsin Graduate School. Appreciation for encouragement and constructive criticism is given to Dr. W. G. Reeder, Dr. J. M. Legler, and Dr.

136 citations

Journal ArticleDOI
TL;DR: Chrysemys picta dorsalis (Agassiz) is one of the most common species of chrysemyms and is found in the Gulf Coast plain from extreme southern Illinois south to the Gulf as discussed by the authors.
Abstract: The members of the Genus Chrysemys provide excellent material for the study of the comparative life histories of turtles. The four subspecies occupy an area that includes the greater part of continental United States and Canada north to 510 N. Latitude. The limits of distribution of the three northern forms are well defined but the eastern and western limits of the range of Chrysemys picta dorsalis (Agassiz) are not known. The differences in area of the ranges of the four forms is striking. Chrysemys picta belli (Gray) occurs from Washington and Oregon on the West southeastward to northern Mexico and northeastward to Missouri and Illinois and to 510 N. Latitude. Chrysemys picta marginata (Agassiz) occurs from the southern part of Ontario southwest through Michigan, eastern Illinois to northern Tennessee and northeastward to Pennsylvania, thence north through New York and extreme western Quebec to 510 N. Latitude. Chrysemys picta picta (Schneider) occurs from Quebec, Nova Scotia and New Brunswick southward through Maine, Vermont and New Hampshire along the Atlantic Coast to Florida. Chrysemys picta dorsalis (Agassiz) occupies the Gulf Coast plain from extreme southern Illinois south to the Gulf. The westward and eastward limits of its range are poorly defined, but the form apparently does not occur in eastern Kentucky, Tennessee or Alabama or western Missouri, Arkansas or eastern Texas. A population in southern Alabama and western Florida may represent a fifth subspecies. Intermediates between each form occur at the junctures of the ranges. Individuals intermediate between Chrysemys picta belli and Chrysemys picta marginata are found in a zone about 200 miles in width extending from southern Illinois north to Ontario. The valley of the Hudson River and the areas of Massachusetts, Rhode Island, Connecticut, Delaware, eastern Pennsylvania and Maryland support a population intermediate between C. picta marginata and C. picta picta. A population that reflects the characters of C. picta bell, C. picta marginata and C. picta dorsalis occurs in extreme southern Illinois. A program of research was undertaken in 1937 aimed at exploring possible ecological differences between populations occurring in northern Michigan, southern Illinois and Tennessee. The studies have since been extended to the Gulf Coast. The bulk of our knowledge of these turtles is contained in short notes, brief discussions in regional reports and the work of experimental biologists. There have been no intensive studies of the bionomics of any one group. Acknowledgement.-I am indebted to many present and former students for their enthusiastic participation in field work. Particularly valuable have been the contributions of Mr. Philip Smith, Mr. Lendell Cockrum, Mr. A. H. Chaney and Mr. Leslie Ellis. A series of turtles essential to the evaluation of growth determinations was loaned by Dr. Norman Hartweg of the Museum of Zoology, University of Michigan. Habitat.-These turtles generally occupy static waters such as lake borders, ponds, and quiet creeks. They are but rarely found in streams with current

78 citations

References
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Journal ArticleDOI
08 Oct 1942-Copeia

38 citations