Patterns in life history phenomena may be demonstrated by examining wide ranges of body weight. Positive relationships exist between adult body size and the clutch size of poikilotherms, litter weight, neonate weight life span, maturation time and, for homeotherms at least, brood or gestation time. The complex of these factors reduces r
max in larger animals or, in more physiological terms, r
max is set by individual growth rate. Comparison of neonatal production with ingestion and assimilation suggests that larger mammals put proportionately less effort into reproduction. Declining parental investment and longer development times would result if neonatal weight is scaled allometrically to adult weight and neonatal growth rate to neonatal weight. Body size relations represent general ecological theries and therefore hold considerable promise in the development of predictive ecology.

Relationships between body size and some life history parameters.

SUMMARY

1. Eggs of Crocodilia and Chelonia, like those of birds, have a pair of egg membranes separating a thick layer of albumen from the calcareous shell. In contrast, eggs of oviparous Lepidosauria have only a single shell membrane, upon which relatively small amounts of calcium carbonate are deposited; and the volume of albumen in eggs is extraordinarily small at the time of oviposition.



2. With the possible exception of certain geckos and some chelonians, eggs of oviparous reptiles seem always to absorb water from the substrate during the course of normal incubation. In so far as the rate of water absorption exceeds the rate of water loss by transpiration from exposed surfaces, the eggs swell during incubation. The term ‘cleidoic’ cannot be used to describe eggs of this type.



3. Embryos of lizards and snakes influence the water potential of extra-embryonic fluids contained within their eggs, thereby maintaining or increasing the gradient in water potential that drives water absorption.



4. Embryos of Crocodilia and Chelonia obtain a substantial portion of the calcium used in ossification of skeletal elements from the inner surfaces of the eggshell. In contrast, embryonic lizards and snakes draw upon extensive reserves of calcium present in the yolk, and obtain little (if any) calcium from the eggshell.



5. All reptilian embryos seem to produce substantial quantities of urea as a detoxification product of protein catabolism. Contrary to expectation, uricotelism may not be common among reptilian embryos, even in those few instances where development takes place within a hard, calcareous egg.



6. In eggs of Crocodilia and Chelonia, respiratory gases seem to pass by diffusion through pores in the calcareous eggshell and through spaces between the fibres of the pair of egg membranes. No pores have been observed in the shell of lepidosaurian eggs, and so gases presumably diffuse between the fibres of the single (multilayered) shell membrane.



7. Metabolism of reptilian embryos is temperature-dependent, as is true for most ectothermic organisms. For each species, there appears to be a particular temperature at which embryonic development proceeds optimally, and departures from this optimum elicit increases in developmental anomalies and/or embryonic mortality.



8. Viviparity has evolved on numerous occasions among species of the Squamata, but seemingly never among Crocodilia or Chelonia. Since the evolution of viviparity entails a progressive reduction in the eggshell, only those organisms whose embryos do not depend upon the eggshell as a source of calcium may have the evolutionary potential to become viviparous.



9. Evolutionary transitions from oviparity to viviparity could have been driven by selection related to (i) thermal benefits to embryos consequent upon retention of eggs within the body of a parent capable of behavioural thermoregulation; (ii) protection of the eggs from nest predators and/or soil microbes; and (iii) more effective exploitation of a seasonal food resource by early emerging young.

The physiological ecology of reptilian eggs and embryos. and the evolution of viviparity within the class reptilia

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I i i i i i i i i

Several investigators have dealt in a theoretical way with the evolution of reproductive rates and attendant life history phenomena (Cole, 1954; Lack, 1954, 1966, 1968; Murphy, 1968; Svardson, 1949; Williams, 1966a, 1966b). Tinkle (1969a) has applied evolutionary principles in an attempt to construct a general theory of the evolution of single-broodedness and iteroparity, of viviparity, and of clutch size and clutch number in lizards. Most of the data presented by him were qualitative. In this paper we pose a series of questions concerning reproductive strategies which have evolved among one group of vertebrates (the lizards), and provide quantitative data to answer them. We further present comparable data from birds, the vertebrate group most thoroughly studied in this respect. Finally, we suggest the weaknesses in studies of reptilian reproduction in the hope of stimulating future workers to collect data that are essential to answer these specific questions.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1558-5646.1970.tb01740.x

Evolutionary strategies in lizard reproduction.

Since their first use in the mid-1980s, passive integrated transponder devices (PIT tags) have allowed innovative investigations into numerous biological traits of animals. The tiny, coded markers injected into individual animals allow assessment of growth rates, movement patterns, and survivorship for many species in a manner more reliable than traditional approaches of externally marking animals for identification. PIT tags have also been used to confirm the identity of zoo animals, pets, and protected species that have been illegally removed from the wild. New approaches with PIT tags herald advances in physiology and conservation biology, as well as greater understanding of social interactions among individuals in a population. Despite their current limitations, including high purchase cost, low detection distance, and potential tag loss in some circumstances, PIT tags offer many opportunities to unravel animal mysteries that heretofore could not be addressed effectively.

https://bioone.org/journals/BioScience/volume-54/issue-5/0006-3568(2004)054[0447:PTSTAI]2.0.CO;2/PIT-Tagging-Simple-Technology-at-Its-Best/10.1641/0006-3568(2004)054[0447:PTSTAI]2.0.CO;2.pdf

PIT Tagging: Simple Technology at Its Best

A System of Marking Turtles for Future Identification

The naturalist's fragmentary knowledge of the habits and life history of turtles has been only feebly augmented since the days of Agassiz. The modern herpetologist has no thorough knowledge of the ecology of any one species and little or no information is available on the bionomics of many others. In 1939 a long term program designed to collect data on the turtles of Illinois was initiated at Carbondale, in the southern part of the state, and data have been accumulated on many phases of the life histories of the more abundant species. In an attempt to obtain data on growth, longevity, attainment of sexual maturity, migration, home ranges, and associated problems, approximately 3000 turtles have been marked and released, and about 500 of these have been recovered at least once. Several hundred stomachs and gonads have been preserved for the study of food and for the analysis of the sex cycle. The present report, concerning growth in the slider turtle Pseudernys scripta elegans Wied, represents the first segment of a long term program on the bionomics of this form. The primary purposes of this paper are: (a) to present and evaluate techniques for studying absolute growth in turtles and (b) to summarize our knowledge of the growth of the turtle named in southern Illinois.

The Growth of the Slider Turtle, Pseudemys Scripta Elegans

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

Observations on the Life Cycles of Painted Turtles (Genus Chrysemys)

Home range, homing behavior, and migration in turtles

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.

Fred R. Cagle

Papers

A System of Marking Turtles for Future Identification

The Growth of the Slider Turtle, Pseudemys Scripta Elegans

Observations on the Life Cycles of Painted Turtles (Genus Chrysemys)

Home range, homing behavior, and migration in turtles

Turtle Populations in Louisiana