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Life history evolution in turtles
... Information on the allometric scaling of turtles' life histories is mostly available for single species (e.g., Portelinha, Malvasio, Piña, & Bertoluci, 2013;Ryan & Lindeman, 2007), and in the few interspecific studies, small sample sizes and nonphylogenetic analyses were used (e.g., Werner & Griebeler, 2013). In some cases, authors used carapace length of turtles and tortoises instead of body mass (e.g., Elgar & Heaphy, 1989;Iverson, 1992;Wilbur & Morin, 1988) making it difficult to compare allometries derived to other taxa, for example, to birds or mammals, due to differences in body shapes of animals. ...
... However, most of these studies have the same limitations as those on crocodiles. Information on life history traits and body size (usually carapace length) was restricted to a few species (e.g., Congdon & Gibbons, 1985;Elgar & Heaphy, 1989;Iverson, 1992; n = 12-35; but see Wilbur & Morin, 1988;Iverson et al., 1993), only a few of the traits (mostly clutch size, clutch mass, and egg size) studied by the authors were already analyzed by other authors, and most authors did not take into consideration the shared evolutionary history of species in their analyses. Nevertheless, all those previous studies on turtles found a significant, positive relationship between body size and the traits studied herein (Congdon & Gibbons, 1985: egg mass, clutch size, clutch mass; Wilbur & Morin, 1988 inversely with body size (Iverson, 1992;Wilbur & Morin, 1988). ...
... Information on life history traits and body size (usually carapace length) was restricted to a few species (e.g., Congdon & Gibbons, 1985;Elgar & Heaphy, 1989;Iverson, 1992; n = 12-35; but see Wilbur & Morin, 1988;Iverson et al., 1993), only a few of the traits (mostly clutch size, clutch mass, and egg size) studied by the authors were already analyzed by other authors, and most authors did not take into consideration the shared evolutionary history of species in their analyses. Nevertheless, all those previous studies on turtles found a significant, positive relationship between body size and the traits studied herein (Congdon & Gibbons, 1985: egg mass, clutch size, clutch mass; Wilbur & Morin, 1988 inversely with body size (Iverson, 1992;Wilbur & Morin, 1988). ...
Allometric relationships linking species characteristics to body size or mass (scaling) are important in biology. However, studies on the scaling of life history traits in the reptiles (the nonavian Reptilia) are rather scarce, especially for the clades Crocodilia, Testudines, and Rhynchocephalia (single extant species, the tuatara). Previous studies on the scaling of reptilian life history traits indicated that they differ from those seen in the other amniotes (mammals and birds), but so far most comparative studies used small species samples and also not phylogenetically informed analyses. Here, we analyzed the scaling of nine life history traits with adult body mass for crocodiles (n = 22), squamates (n = 294), turtles (n = 52), and reptiles (n = 369). We used for the first time a phylogenetically informed approach for crocodiles, turtles, and the whole group of reptiles. We explored differences in scaling relationships between the reptilian clades Crocodilia, Squamata, and Testudines as well as differences between reptiles, mammals, and birds. Finally, we applied our scaling relationships, in order to gain new insights into the degree of the exceptionality of the tuatara's life history within reptiles. We observed for none of the life history traits studied any difference in their scaling with body mass between squamates, crocodiles, and turtles, except for clutch size and egg weight showing small differences between these groups. Compared to birds and mammals, scaling relationships of reptiles were similar for time‐related traits, but they differed for reproductive traits. The tuatara's life history is more similar to that of a similar‐sized turtle or crocodile than to a squamate.
... Energy budgets in iteroparous organisms are allocated along three main axes: growth, survivorship (including maintenance), and reproduction (Stearns, 1977(Stearns, , 1992Congdon, 1989). When iteroparous organisms attain sexual maturity, a trade-off is made between energy invested in survivorship and that in reproduction based on environmental conditions and selection Studies of turtle life-history evolution have focused on lifestyles -terrestrial, freshwater, and marine (Wilbur and Morin, 1988) -correlations between reproductive output traits (Iverson, 1992), and variation of clutch size and body size with latitude (Moyers-Arévalo, 2012). Indeed, reproductive output has been a common focus of turtle research over the last two decades (Iverson, 1992;Broderick et al., 2003). ...
... The correlation of clutch size/egg width with body size confirms a common trend in the reproductive ecology of turtles (Wilbur and Morin, 1988;Iverson, 1992;Ryan and Lindeman, 2007;Macip-Ríos, 2010). It seems that producing more eggs per clutch is a direct response of larger body size (Congdon and Gibbons, 1985; but see Ryan and Lindeman, 2007). ...
... However, according to our results, egg size (width) did not correlate in any way with clutch size as would be expected by the typical trade-off between size and number of offspring (Smith and Fretwell, 1974;Stearns, 1989). This result is at odds with previous life-history studies in turtles (Wilbur and Morin, 1988) in which lifestyle (terrestrial, marine, and freshwater) was considered the main factor in life-history variation. According to our data, changes in body size could be the primary response to environmental variation across this lineage of turtles. ...
Question: Does environmental unpredictability drive the evolution of reproductive effort? Data incorporated: We used life-history data from 31 kinosternid turtles. We tested relationships using the phylogenies of Iverson et al. (2013) and Spinks et al. (2014). Methods: Phylogenetically uncorrected: We ran correlations between life-history traits and historic climatic variation. We used analysis of covariance (ANCOVA) to compare traits between temperate and tropical taxa. Phylogenetically corrected: We calculated independent contrasts and used the contrasts in correlations of life-history traits with historic climatic variation. To compare life-history traits between temperate and tropical taxa, we ran phylo-genetic ANCOVAs and tested for phylogenetic signal. Conclusions: Reproductive effort decreases with climatic variation. Temperate species evolved smaller clutches with large eggs and high reproductive effort. Tropical species from Mexico evolved larger clutches with medium-sized eggs and low reproductive effort.
... The selection for greater reproductive success and greater fecundity exercised by mature males, resulting in large female sizes is well documented in the literature [45,46,57,58]. Natural selection for greater fecundity supports larger females having greater reproductive capacity; a larger body accommodates larger clutches, larger eggs, or larger annual egg production [58][59][60]. ...
... The selection for greater reproductive success and greater fecundity exercised by mature males, resulting in large female sizes is well documented in the literature [45,46,57,58]. Natural selection for greater fecundity supports larger females having greater reproductive capacity; a larger body accommodates larger clutches, larger eggs, or larger annual egg production [58][59][60]. In several turtle studies, the female body sizes and all three dimensions, length, width, and height were correlated with their fecundity [36,45,59]. ...
Simple Summary
The Mediterranean stripe-necked turtle Mauremys leprosa is known to possess physiological mechanisms allowing it to adapt without particular signs of physiological disorder or stress in habitats with high pollution. Nevertheless, we were uncertain about the costs of this adaptation and its impact on reproduction. The reproductive traits measured in this study suggest the adaptation of M. leprosa to flourish well in highly degraded–polluted areas compared to undisturbed habitats. M. leprosa was so well adapted to the pollution that the exposed population actually increased its reproductive capacity. Females living in the highly degraded–polluted habitat exhibited record body sizes for the species, which allowed them to carry both more and larger eggs. In comparison, the corresponding reproductive traits measured in the intact habitat ranged within the limits reported in previous studies.
Abstract
We measured and compared the reproductive traits of the Mediterranean stripe-necked turtles Mauremys leprosa living in highly degraded–polluted vs. intact natural habitats in Algeria. Data on reproduction were obtained by using X-ray examination of gravid females and examination of nests. The results were opposite to the negative trend confirmed in most freshwater turtles exposed to pollution and suggested the ability of this species to flourish instead in highly degraded–polluted habitats. An optimum development was recorded for several reproductive patterns of the studied freshwater turtle under conditions considered uninhabitable for other vertebrates. Females exhibited record body sizes among conspecifics, which allowed them to carry significantly larger clutches, exceeding by up to 3 eggs the previously largest reported clutch. The mean clutch size (8.79 ± 2.70 eggs) was also higher than findings from previous studies, except for in some other polluted habitats. Furthermore, large females even with large clutches carried large eggs. Egg measurements in the disturbed habitat revealed new records exceeding those previously noted; in egg length (by 3.0 mm), egg width (by 2.8 mm), egg mass (by 1.8 g), and clutch mass (by 18.6 g). In comparison, the usual reproductive performances were observed in the intact natural habitat; female body sizes were significantly smaller and carried fewer eggs of smaller size.
... Natural selection for greater fecundity supports larger females having greater biotic capacity; a larger body accommodates larger clutches, egg sizes, or annual egg production [21,38]. The clutch size and body size of T. graeca females were positively correlated [11]. ...
... These characteristics gives females more volume for the visceral organs involved in the nutrient treatment necessary for vitellogenesis, gestation, and carrying eggs [18]. A strong positive correlation was observed between the fecundity of females and their shell shape [18,38]. Males are not constrained by any parental care but concerned with courting and mating. ...
Simple Summary
Assessing the body size and body shape variations between sexes and geographical populations can help us understand the adaptive responses of organisms in the face of the pressures to which they are subjected. To evaluate the influence of habitat-type conditions, we selected six Algerian populations of Testudo graeca living in different environments. The results of the traditional morphometric analyses showed that body size and shell shape were smaller and flattened, respectively, in males, especially under unfavorable conditions for tortoises; these changes were jointly caused by anthropogenic and natural pressures. We found clear evidence in several tortoise species that differences in growth durations up to the onset of maturity resulted primarily in different sizes at maturity and ultimately in different adult sizes.
Abstract
Using data for the body size and shell shape of Algerian Testudo graeca, we assessed how proximate causes shaped the observed variation in the morphology of adults. All of the studied populations displayed significant sexual size and shape dimorphisms. Relative to body length, females displayed larger, more voluminous and domed shells than males. We found clear evidence that variation in body size at maturity influenced sexual size dimorphism. Body size at maturity depends on the duration of growth from hatching up to the point of reaching sexual maturity. In the studied populations, sexual maturity, estimated by counting growth lines, was always reached earlier in males than in females (a time difference of 1.4–3.0 years). Similar to sexual size dimorphism, geographic variation in adult body sizes was also influenced by variations in the corresponding sizes at maturity. Remarkably, the population with the largest tortoises had the latest mean maturation time: 9.1 for males and 10.5 for females. Thus, the later completion of maturation was a determinant for a larger size in adulthood. The largest tortoises among the studied populations were measured at the Djelfa locality, where the recorded sizes of males and females reached 186 and 230 mm, respectively.
... Longevity and delayed maturity are often expressed to the extreme in chelonians (Wilbur & Morin, 1988). At present day, an ever-increasing set of threats (Klemens, 2000) have made that combination of life-history traits a chelonian Achilles' heel, with almost 70% of all 335 species threatened or recently extinct (almost 46% of which endangered or critically endangered); for many, conservation status has not been assessed (van Dijk et al., 2014). ...
... Both Hermann's tortoises and European pond turtles reach maturity between the ages of eight and 12 (six in Olivier, 2002;Rogner, 2009;Bertolero et al., 2011), yet arrive at a survival plateau earlier -at approximately four-to 5-yearsold ( Fig. 1 and 2). This is likely a consequence of the final hardening of the carapace, which can bring obvious survival benefits prior maturity (Wilbur & Morin, 1988). After maturity, European pond turtles from Camargue experience sex differences in survival (Olivier et al., 2010); nonetheless, our results overrule the possibility of it originating prior maturity. ...
... Reviews of egg biology in the Testudinata have been conducted regularly (Ewert, 1979(Ewert, , 1985Miller & Dinkelacker, 2008;Packard & Packard, 1988;Wilbur & Morin, 1988). While various life-history scenarios have been investigated in the context of testudine reproduction, e.g., egg size (Wilbur & Morin, 1988), there has yet to be sustained investigation of the possible reasons underlying functional differences between eggs with differing shell types. ...
... Reviews of egg biology in the Testudinata have been conducted regularly (Ewert, 1979(Ewert, , 1985Miller & Dinkelacker, 2008;Packard & Packard, 1988;Wilbur & Morin, 1988). While various life-history scenarios have been investigated in the context of testudine reproduction, e.g., egg size (Wilbur & Morin, 1988), there has yet to be sustained investigation of the possible reasons underlying functional differences between eggs with differing shell types. This analysis explores the possible reasons why eggshell variability exists within the Testudinata with an emphasis on comparison of egg and clutch characteristics associated with shell differences. ...
Testudines exhibit considerable variation in the degree of eggshell calcification, which affects eggshell conductance, water physiology of the embryos, and calcium metabolism of embryos. However, the underlying reason for different shell types has not been explored. Phylogenetically controlled analyses examined relationships between egg size, shell mass, and clutch size in ∼200 turtle species from a range of body sizes and assigned by family as laying either rigid‐ or pliable‐shelled eggs. Shell type affected egg breadth relative to pelvic dimensions, egg mass, and relative shell mass but did not affect size, mass, or total shell mass of the clutch. These results suggest that calcium availability may be a function of body size and the type of shell may reflect in part the interplay between clutch size and egg size. It was further concluded that the eggshell probably evolved as a means of physical protection. Differences in shell calcification may not primarily reflect reproductive parameters but rather correlate with the acidity of a species’ nesting environment. Low pH environments may have thicker calcareous layer to counteract the erosion caused by the soil and maintain the integrity of the physical barrier. Limited calcium availability may constrain clutch size. More neutral nesting substrates expose eggshells to less erosion so calcification per egg can be reduced and this allows larger clutch sizes. This pattern is also reflected in thick, calcified crocodilian eggs. Further research is needed to test whether eggshell calcification in the testudines correlates with nest pH in order to verify this relationship.
... Individual growth rates affect adult body size, which in turn influences individual survivorship, reproductive output, and, therefore, lifetime fitness (Stearns 1992). The growth rate of many freshwater turtles is characterized by rapid juvenile growth that declines at maturity and is slow to non-existent as an asymptotic body size is attained in older adults (Andrews 1982; Wilbur and Morin 1988; Shine and Iverson 1995; Congdon et al. 2013). Variation in individual growth rate can result in dramatic differences in age and size at maturity, maximum body size, and survivorship (Berry and Shine 1980; Wilbur and Morin 1988; Shine and Iverson 1995; Lindeman 1999). ...
... The growth rate of many freshwater turtles is characterized by rapid juvenile growth that declines at maturity and is slow to non-existent as an asymptotic body size is attained in older adults (Andrews 1982; Wilbur and Morin 1988; Shine and Iverson 1995; Congdon et al. 2013). Variation in individual growth rate can result in dramatic differences in age and size at maturity, maximum body size, and survivorship (Berry and Shine 1980; Wilbur and Morin 1988; Shine and Iverson 1995; Lindeman 1999). Sources of variability in the growth rate of turtles include environmental factors such as temperature, primary productivity, and latitude (Kennett 1996; Litzgus and Brooks 1998; Germano and Bury 2009; Congdon et al. 2013) and genetic factors such as species, populations, and sex (Berry and Shine 1980; Dunham and Gibbons 1990; Congdon et al. 2003; 2013). ...
We studied the natural somatic growth of Apalone spinifera using mark-recapture in a population inhabiting a small urban stream for 16 y. Growth was rapid and variable in hatchlings and young juveniles, but as body size increased, growth slowed, more rapidly in males than in females. Growth in the largest turtles was slow or immeasurable. Von Bertalanffy growth models indicated that males typically matured in their 4 th or 5 th year and females in their 12 th or 13 th year. The general growth pattern of A. spinifera was similar to that reported for many sexually dimorphic freshwater turtles, including A. mutica, the sister species of A. spinifera. Individual growth rate in turtles has important implications for science-based conservation efforts because of its effect on maturation, reproductive output, survivorship, and population recruitment.
... The size and shape of the body are the most conspicuous and fundamental characteristics in the life history of an organism; these features reflect evolutionary characteristics that intervene in the success of the species, populations, and individuals, as well as being important indicators of the morphological adaptations of a species to its environment [5][6][7][8][9][10][11][12]. In a concrete sense, the physical characteristics of the individuals influence the structure of the population, and intervene and maintain its balance in aspects such as feeding, growth, association, reproduction, and intraspecific interactions, among others. ...
Body size is one of the most important traits in the life history of vertebrates. In this work, we analyzed the morphometric traits of breeding males of the eastern Pacific green sea turtle population known as the black sea turtle on the coast of Michoacan, Mexico. The morphometric analysis indicates that males have the smallest body size compared to other males in other Chelonia populations. The size of male black sea turtles is even smaller (by 15.2 cm in average CCL) in carapace curve length (70.5 cm CCL) than females (85.7 CCL) of the same population. This suggests that males reach maturity at an earlier age than females and would have implications for mating success. The assessment of the operational sex ratio was conducted over a multi-year period (2004, 2009, 2017, and 2023). From a total of 336 h of observation, we identified 653 mating groups containing 1986 males and 669 females. The estimated operational sex ratio (OSR) during the study period was 2.96 males for every female. Among the mating groups, 34.3% consisted of only one male, while 65.7% included two or more males, with the number of males per female ranging from 2 to 17. The analysis revealed that there are interannual and monthly variations in OSR values, with observations showing a range from 2.3:1 (male to female) in 2023 to 4.3:1 (male to female) in 2009. The OSR variations show an evolving trend that can inform future strategies. In September, the ratio was 2.8:1, which changed to 3:1 in October and November, and then reached 3.3:1 in December (male/female). This gradual increase provides a clear opportunity to delve deeper into these dynamics and take proactive measures to address them positively.
... Turtle populations have a high adult longevity and survival with a moderate juvenile contribution (Wilbur and Morin, 1988;Congdon and Gibbons, 1983;Frazer et al., 1990). Nevertheless, these three freshwater The red-eared slider capture frequency is roughly stable in eleven years in our studied lagoons, in spite of removal efforts. ...
RESUMEN El galápago de Florida: una amenaza para los galápagos autóctonos en un humedal continental del noreste ibérico. Analizamos los cambios en la estructura y la dinámica de las poblaciones entre 2004 y 2015 de dos galápagos autóctonos, el galápago leproso (Mauremys leprosa) y el galápago europeo (Emys orbicularis), que conviven con la especie exótica invasora Trachemys scripta elegans en la Reserva Natural Dirigida de Los Sotos y Galachos del Ebro, un humedal continental del noreste ibérico. Se extrajeron 206 galápagos de Florida. Sin embargo, a pesar del esfuerzo de extracción, sus capturas se mantuvieron constantes en el tiempo. El galápa-go de Florida se reproduce en la naturaleza y prevalecen las hembras de gran tamaño, que podrían provenir en parte de cautividad. Las capturas de galá-pago leproso fueron aumentando: su estimación poblacional pasó de 36 a 90 ejemplares, manteniendo una proporción equilibrada de sexos y un predo-minio de ejemplares grandes. La estimación de galápago europeo se mantuvo en el tiempo (28 ejemplares). La proporción de ejemplares pequeños (juveni-les) fue baja (8,8 % y 10,4 % respectivamente) en los galápagos autóctonos y mucho mayor (24,1 %) en el galápago de Florida, probablemente debido a LUCAS MALLADA, 24 (2022) su mayor tasa de reproducción. El seguimiento de las tres especies y la extracción de la especie exótica deben continuar para garantizar la viabili-dad de los galápagos autóctonos y se deben desarrollar campañas de educa-ción ambiental para evitar la liberación de nuevos galápagos exóticos en la naturaleza. PALABRAS CLAVE Trachemys scripta. Emys orbicularis. Mauremys leprosa. Competición. Especies invasivas. Reserva Natural Dirigida de Los Sotos y Galachos del Ebro. Noreste ibérico (España). ABSTRACT We analysed (2004-2015) the changes in population structure and dynamics of two native freshwater turtles-the Mediterranean pond turtle (Mauremys leprosa Schweigger, 1812) and the European pond turtle (Emys orbicularis L., 1758)-and the invasive American red-eared slider Trachemys scripta in the Ebro Sotos and Galachos Managed Natural Reserve, a continental wetland in NE Iberia. Two hundred and six red-eared sliders were removed. In spite of removal efforts, captures still do not decrease in time, reproduction in the wild occurs and large body females, possibly some of them coming possibly coming from captivity, prevail. Captures of Mediterranean pond turtle increases in time, its population estimate increased from 36 to 90, has a balanced adult sex ratio and large animals predominate. Estimation of European pond turtle stays in time (28 specimens). Native freshwater turtles have few small (juveniles) specimens and red-eared slider more than double them, probably due to its higher reproduction rate. The monitoring of the three species and the removal of the red-eared slider must continue to ensure native freshwater pond turtles viability. Environmental education campaigns should be developed to avoid the release of new red-eared sliders in the wild.
... All sea turtle species have adults with large body sizes (65-180 cm), a long period of development ranging from 10 to 35 years and lay large clutches of relatively small (3-7 cm) eggs compared to other aquatic turtles [9,[33][34][35][36][37][38]. Presumably, sea turtles evolved this reproductive pattern in response to high and unpredictable mortality rates during the egg and neonate life stages [9]. ...
Simple Summary
This paper presents important aspects of the life history of the black sea turtle (Chelonia mydas agassizii) population nesting on the beaches of Michoacan, Mexico. Information on morphometric and reproductive traits related to the life history of black sea turtles (body size, clutch size, egg size, fecundity, remigration interval, age at sexual maturity, and growth rate) was studied. An analysis of interannual variations in the life history traits of the species is also carried out, and the results obtained indicate that C. m. agassizii differs from the information reported for other populations of Chelonia mydas mydas distributed pantropically.
Abstract
Sea turtles present strategies that have allowed them to survive and reproduce. They spend most of their lives in the sea, except when they emerge as hatchlings from the nest and when the adult females return to nest. Those moments of their life cycle are vital for their reproductive success, conservation, and knowledge of their biology. This study reports the life history traits exhibited by female black sea turtles from Colola Beach, Mexico using morphometric and reproductive data obtained during 15 sampling seasons (1985–2000, n = 1500). The results indicate that nesting females have a mean body size of 85.7 cm and reach sexual maturity at 24 years old at a minimum size of 68 cm. Females deposit a mean of 69.3 eggs per clutch, and the mean fecundity was 196.4 eggs per female per season. The remigration intervals of 3 and 5 years were the most frequent registered. The life history traits found in the black sea turtle population present the lowest values reported with respect to studies conducted in the Atlantic and Indo-Pacific green turtle populations, which supports the hypothesis that this population is recovering, since morphometric and reproductive data represent young nesting turtles.
... Macroevolutionary patterns in amniote reproduction (Battistella et al., 2019;Murray, Crother & Doody, 2020;Starck, Stewart & Blackburn, 2021) can be investigated based on the diversity of traits in egg and clutch (e.g., Kaplan & Salthe, 1979;Deeming & Birchard, 2007;Jetz, Sekercioglu & Böhning-Gaese, 2008;Deeming & Ruta, 2014). The idea of an "optimal" correlation between egg and clutch size, based on trade-offs associated to K/r strategies, has led to several discussions without a consensus about the distribution or reasons of such correlations (Smith & Fretwell, 1974;Congdon & Gibbons, 1987;Wilbur & Morin, 1988;Elgar & Heaphy, 1989;Godfray, Partridge & Harvey, 1991;Kuchling, 1999;Zhao, Chen & Liao, 2017;Yu & Deng, 2020). Optimal egg/clutch size theory assumes that changes in the egg and clutch are driven by selection, resulting in adjustments for the largest possible production of offspring with the highest fitness, at the lowest cost to their progenitors (Brockelman, 1975;Congdon & Gibbons, 1987;Janzen & Warner, 2009). ...
Optimal egg size theory assumes that changes in the egg and clutch are driven by selection, resulting in adjustments for the largest possible production of offspring with the highest fitness. Evidence supports the idea that large-bodied turtles tend to produce larger clutches with small and round eggs, while smaller species produce small clutches with large and elongated eggs. Our goals were to investigate whether egg and clutch size follow the predictions of egg size theory, if there are convergent reproductive strategies, and identify ecological factors that influence clutch and egg traits across all clades of living turtles. Using phylogenetic methods, we tested the covariance among reproductive traits, if they are convergent among different turtle lineages, and which ecological factors influence these traits. We found that both egg shape and size inversely correlate with clutch size, although with different evolutionary rates, following the predictions of the egg size theory. We also present compelling evidence for convergence among different turtle clades, over at least two reproductive strategies. Furthermore, climatic zone is the only ecological predictor to influence both egg size and fecundity, while diet only influences egg size. We conclude that egg and clutch traits in Testudines evolved independently several times across non-directly related clades that converged to similar reproductive strategies. Egg and clutch characteristics follow the trade-offs predicted by egg size theory and are influenced by ecological factors. Climatic zone and diet play an important role in the distribution of reproductive characteristics among turtles.
... Upon emerging from the nest, hatchling turtles of many species must travel from the nest site to habitat that is suitable for finding food, shelter, and potentially overwintering (e.g., Salmon et al., 1995;Putman et al., 2010). For many aquatic turtle species, the journey from a nest site in open, sunny habitat to aquatic habitat suitable for the juvenile stage exposes hatchlings to predators, desiccation, and potentially lethal temperature extremes (Janzen, 1993;Wilbur and Morin, 1988;Janzen et al., 2000Janzen et al., , 2007. Therefore, as in other species (e.g., Kamel and Mrosovsky, 2004;Streby et al., 2014a), nest-site choice by female turtles likely requires balancing opposing selection pressures on different life stages. ...
Differing selection pressures on stationary nest contents compared to mobile offspring mean that the nest-site characteristics resulting in the highest nest success may not be the same characteristics that result in the highest survival of juveniles from those nests. In such cases, maternal nest-site choice may optimize productivity overall by selecting nest sites that balance opposing pressures on nest success and juvenile survival, rather than maximizing survival of either the egg or the juvenile stage. Determining which macro- and microhabitat characteristics best predict overall productivity is critical for ensuring that land management activities increase overall recruitment into a population of interest, rather than benefiting one life stage at the inadvertent expense of another. We characterized nest-site choice at the macro- and microhabitat scale, and then quantified nest success and juvenile survival to overwintering in two declining turtle species, eastern box turtles and spotted turtles, that co-occur in oak savanna landscapes of northwestern Ohio and southern Michigan. Nest success in box turtles was higher in nests farther from macrohabitat edges, constructed later in the year, and at greater total depths. In contrast, survival of juvenile box turtles to overwintering was greater from nests under less shade cover and at shallower total depths. Spotted turtle nest success and juvenile survival were so high that we were unable to detect relationships between nest-site characteristics and the small amount of variation in survival. Our results demonstrate, at least for eastern box turtles, a tradeoff in nest depth between favoring nest success vs. juvenile survival to overwintering. We suggest that heterogeneity in microhabitat structure within nesting areas is important for allowing female turtles to both exercise flexibility in nest-site choice to match nest-site characteristics to prevailing weather conditions, and to place nests in close proximity to habitat that will subsequently be used by hatchlings for overwintering.
... Due to adult longevity and low recruitment rates, most leopard tortoise populations show a bias towards larger-sized individuals (Hailey and Coulson, 1999;Hailey and Lambert, 2002). This is also because, in chelonians generally, juvenile growth rate is rapid until sexual maturity following which slow but continuous growth occurs in adults (Alexander, 1982;Shine and Iverson, 1995;Wilbur and Morin, 1988). Indeed, leopard tortoise individuals can weigh 1 kg by 7-8 years of age and body mass may double every 2-3 years thereafter (Branch, 2008), with females growing faster than males in most regions (Boycott and Bourquin, 2000). ...
Establishing body mass from skeletal remains of an animal is of importance to researchers in the fields of ecology, palaeontology and archaeozoology. Establishing such standards requires that different body parts follow allometric growth curves, and that one can access a sufficiently large sample of individuals of known size and weight for the target species. Here, we have used data collected from modern living and dead leopard tortoises Stigmochelys pardalis (Bell, 1928Bell, 1928), to reconstruct body size and mass from measurements taken on individual postcranial bones. The results show high correlations in both mass and size for various dimensions taken on most skeletal elements, enabling reconstruction of these parameters from individual skeletal measurements. To highlight the application of such data to fossil fauna, allometric equations derived from regression analyses of the modern animals were applied to a sample of Later Stone Age (ca. 14,000 BP to present) leopard tortoise remains from Wonderwerk Cave located in the central interior of South Africa. Results for this archaeological sample show significant changes in size and body mass over time. These best correlate with shifts in paleoenvironmental conditions rather than with anthropogenic pressures that has commonly been implicated in size reduction or biased sex ratios in tortoise populations.
... In this area, T. graeca are distributed across ~2600 km 2 of semiarid mountains, where annual precipitation ranges between 150 and 570 mm year −1 . This species has slow population dynamics (sensu Wilbur and Morin 1988), steady population growth rates (i.e. λ ~ 1, Rodríguez-Caro et al. 2016), delayed maturation (9-12 years, Graciá et al. 2020) and low offspring production (< 2 hatching per female per year, Jiménez-Franco et al. 2020). ...
Animal populations have developed multiple strategies to deal with environmental change. Among them, the demographic buffering strategy consists in constraining the temporal variation of the vital rate(s) that most affect(s) the overall performance of the population. Tortoises are known to buffer their temporal variation in adult survival, which typically has the highest contribution to the population growth rate λ, at the expense of a high variability on reproductive rates, which contribute far less to λ. To identify the effects of projected increases in droughts in its natural habitat, we use field data collected across 15 locations of Testudo graeca in southeast Spain over a decade. We analyse the effects of environmental variables on reproduction rates. In addition, we couple the demographic and environmental data to parameterise an integral projection model to simulate the effects of different scenarios of drought recurrence on λ under different degrees of intensity in the survival–reproduction tradeoff. We find that droughts negatively affect the probability of laying eggs; however, the overall effects on λ under the current drought recurrence (one/decade) are negligible when survival is constant (independent of the reduction of reproduction by drought events) and when survival increased as a tradeoff with the reduction of reproduction rates, with a threshold to population viability at three or more droughts/decade. Additionally, we show that, although some species may buffer current environmental regimes by carefully orchestrating how their vital rates vary through time, a demographic buffering strategy is insufficient to ensure population viability in extreme regimes. Our findings support the hypothesis that the demographic buffering strategy has a limit of effectiveness when adverse conditions occur frequently. Our methodological approach provides a framework for ecologists to determine how effective the management of environmental drivers can be for demographically buffering populations, and which scenarios may not provide long‐term population persistence.
... How egg size relates to adult body size is subject to numerous extrinsic factors that ultimately modulate variation in growth rates (Arendt, 1997;Dmitriew, 2011). Some species of Geoemydidae disproportionately allocate maternal reproductive energy (yolk) to one or two large eggs that, in turn, yield large hatchlings with enhanced probability of survival (Iverson & Ewert, 1991;Wilbur & Morin, 1988). Offspring survival in miniaturized species of Chelydroidea is perhaps not as dependent on body size because juveniles are highly adept at hiding in shallowwater habitats or can remain within terrestrial shelters until environmental conditions are favorable (Cordero & Swarth, 2010;Ernst & Lovich, 2009). ...
Organismal miniaturization is defined by a reduction in body size relative to a large ancestor. In vertebrate animals, miniaturization is achieved by suppressing the energetics of growth. However, this might interfere with reproductive strategies in egg-laying species with limited energy budgets for embryo growth and differentiation. In general, the extent to which miniaturization coincides with alterations in animal development remains obscure. To address the interplay among body size, life history, and ontogeny, miniaturization in chelydroid turtles was examined. The analyses corroborated that miniaturization in the Chelydroidea clade is underlain by a dampening of the ancestral growth trajectory. There were no associated shifts in the early sequence of developmental transformations, though the relative duration of organogenesis was shortened in miniaturized embryos. The size of eggs, hatchlings, and adults was positively correlated within Chelydroidea. A phylogenetically broader exploration revealed an alternative miniaturization mode wherein exceptionally large hatchlings grow minimally and thus attain diminutive adult sizes. Lastly, it is shown that miniaturized Chelydroidea turtles undergo accelerated ossification coupled with a ~10% reduction in shell bones. As in other vertebrates, the effects of miniaturization were not systemic, possibly owing to opposing functional demands and tissue geometric constraints. This underscores the integrated and hierarchical nature of developmental systems.
... Because nest locations and microclimates affect offspring survival (Wilson 1998;Spencer 2002), sex (Janzen 1994;Roosenburg 1996), size (Brooks et al. 1991;Packard 1999), and performance (Finkler 1999;Kolbe and Janzen 2002), the choices that females make during nest site selection have profound effects on fitness. Successful nests are those that remain undetected and unmolested by predators; do not suffer flooding, erosion, or root encapsulation; and provide appropriate thermal regimes and hydration levels for developing embryos (Wilbur and Morin 1988;Congdon et al. 2000). ...
Northern map turtles (Graptemys geographica) are a species of conservation concern with a limited distribution in Pennsylvania. We examined nest site fidelity of G. geographica along the Juniata River at Mount Union, the largest reported nesting area in the Commonwealth. Nesting habitat included a mitigation area bordering a highway, partitioned by a turtle exclusion fence, and an adjacent pile of coal tailings. A linear grid along the turtle fence allowed us to determine distances between nests of individual females. Our results indicate that female G. geographica at Mount Union exhibit nest site fidelity, as the frequency distribution of distances between nests of individual females was positively skewed, and distances between nests (both within and among seasons) were smaller than distances between randomly selected pairs of nests from different individuals. Females placed different clutches of eggs as close together as 0.30 m. Within-season (first and second clutch) inter-nest distances were significantly smaller than inter-nest distances among years, which increased over time. We also attached radio-transmitters to a sample of adult females following nesting to determine the extent of riverine migrations, as long-distance nesting migrations are associated with fidelity to particular nesting sites. Following nesting, two females remained in the river near the Mount Union nesting habitat and three females moved downstream 4.3–5.6 km, yet all of the turtles returned to their previous nesting areas the following summer. Nest site fidelity can benefit map turtles if the habitat remains stable, results in high nest survivorship, and produces high quality hatchlings, yet the behavior may be detrimental if it exposes turtles to significant risks such as road mortality or environmental contaminants. Our results indicate that maintaining long-term nesting habitat and ensuring suitable river quality at Mount Union may be essential for the conservation of G. geographica in central Pennsylvania.
... Desert tortoises have low egg and juvenile survivorship , 1987a, Karl 1999, Bjurlin & Bissonette 2004, but have high adult survivorship and long lives (Turner et al. 1984, 1987a, Curtin et al. 2009), as do many chelonians (e.g. Wilbur & Morin 1988, Congdon & Gibbons 1990, Kuchling 1999. But adult growth is slow, sexual maturity is reached late (ca. ...
ABSTRACT: We measured survival, growth, and body condition of 8 hatchling cohorts of desert tortoises Gopherus agassizii (living in predator-resistant outdoor pens in the Mojave Desert, California,
USA) over 11 yr to evaluate head-starting methods. At 11 yr of age, 7 times as many of the first cohort had survived than if they had been free-living tortoises. Subsequent improvements in predator control, food and water supplementation, and pen structure increased survival from 7 to 10 times that under wild conditions in younger cohorts. Annual survival averaged 96%. Carapace length (CL) increased 6.95 mm yr−1, similar to that of free-living tortoises. Annual growth rates
varied with calendar year (possibly reflecting food and water supply), age, cohort (year hatched), mother, and in 4 dry years, with crowding. Most of the first cohort grew to a releasable size (CL >100 mm) by their 9th year. Body condition indices remained high, indicating little dehydration despite droughts in 8 of the 11 years, because irrigation offered drinking opportunities. Head-started tortoises developed fully hardened shells (≥98% of adult shell hardness) earlier (10.1 vs. 11.6 yr), but at a larger CL (117 vs. 104 mm) than did free-living tortoises. Selective feeding in head-start pens decreased subsequent germination of favored wildflower species, apparently by reducing the natural seedbank. Consequently, we reseeded and irrigated each autumn to promote subsequent spring food supply. We irrigated in early summer to enable drinking and ensuing consumption of dry, dead plants and Bermuda grass hay, a supplement. These procedures can greatly improve juvenile survivorship, and increase numbers of hard-shelled, midsized juveniles to help augment wild populations.
... It is believed that larger female sea turtles have larger pelvic opening structures compared with those of smaller ones, and this structure constrains egg size and hence offspring size. Since larger females can accumulate more resources and/or bigger eggs, because of their larger pelvic opening, they can therefore produce more eggs (Wilbur & Morin, 1988). Therefore, the relationship between clutch size and frequency of multiple paternity reported by the reviewed studies (Table 2) was statistically analysed. ...
Sea turtles are promiscuous breeders. Since it is very difficult to observe individuals of a marine species while mating and usually impossible to determine the successful mating, molecular studies provide a tool to make an inference about mating system of this species. Recent molecular studies on sea turtle mating systems have demonstrated that polyandry is much more common than polygyny in sea turtles. It is well known that multiple paternity (MP) is evident in all sea turtle populations with polyandrous mating system. Determination of frequency of MP is of great importance for understanding of mating system and population structure of endangered populations and contributes to the conservation efforts. The frequency of MP shows
great inter- and intra-specific variability. But why does this frequency vary greatly within and among species? Why does a female sea turtle mate multiple times within a season? Do the females benefit from MP? To elucidate these questions, here I review the frequency of MP for sea turtles nesting around the world. Based on data for several rookeries throughout the world, there were significant differences in the frequency of MP among species (p < 0.01). The frequency of MP was statistically correlated to neither clutch size (eggs) nor female size (curved carapace length [CCL]) (p > 0.05). However, there was a moderate positive correlation between the frequency of MP and hatching success (defined as the rate of hatchlings emerging successfully from the eggs) (r2 = 0.45, p < 0.05). These findings suggest that MP, contrary to common belief, does not work in favour of larger females and does not result in increased clutch size, but hatching success increases with the increasing frequency of MP. It can be concluded from these evaluations that MP in sea turtle may have at least some benefits: increased genetic diversity and heightened offspring viability and variability.
... In red-eared sliders, sexual maturity is mainly related to body size rather than age (Wilbur and Morin 1988;Gibbons and Greene 1990). In productive habitats, female sliders reached the size of maturity with a plastron length of 160-170 mm at a younger age (4 years old) (Congdon and Gibbons 1983). ...
Invasive alien species pose a serious threat to native biodiversity and the ecosystem structure through predation or competition, and this threat is especially severe in China. Red-eared sliders (Trachemys scripta elegans) were introduced to mainland China to meet demands for food, traditional Chinese medicine, and the pet trade. However, there has been a lack of field surveys to assess the population, behavior and ecological impacts of introduced red-eared sliders in urban aquatic ecosystems in northern China. We conducted such research in 33 urban parks in Beijing from April to November 2016. The alien sliders were recorded on 514 occasions at 19 parks, and 45 individuals were captured from 4 parks to evaluate their diet composition and reproductive status. The observations showed that red-eared sliders accounted for 95% of the recorded turtles in the parks. The male to female ratio was 1.0:3.5, and the ratio of adults to juveniles was 1.0:3.1. According to stomach content analysis, the sliders fed mainly on animals: the dominant prey were Gastropoda, Osteichthyes, Crustacea, Hexapoda, Bivalvia, Reptilia and Aves in descending order. The high frequency (83%) of follicles and oviduct development in adult females suggested a strong reproductive capacity, which was further supported by one case of early female maturity. Bacteriological examinations demonstrated that the carrying rate of Salmonella bacteria was up to 17.6%. This study demonstrated that red-eared sliders have successfully colonized the waters of urban parks in Beijing and potentially threaten native aquatic biodiversity.
... Road mortality biases population sex ratios towards males (Gibbs and Steen, 2005;Dupuis-Desormeaux et al., 2017) and age ratios towards juveniles, as adult females are disproportionately killed during overland nesting movements (Marchand and Litvaitis, 2004). Because turtle life histories are characterized by high adult survival rates, delayed sexual maturity, and low recruitment (Wilbur and Morin, 1988;Congdon and Gibbons, 1990), this demographic trend jeopardizes population persistence (Gibbs and Shriver, 2002). ...
... 36, Fig. 11; Fig. 14). This is likely a consequence of the final hardening of the carapace, which can bring obvious survival benefits prior maturity(Wilbur & Morin 1988). After maturity, ...
Two populations, island and mainland, of promiscuous sexually coercive Hermann tortoises (Testudo hermanni, a species with delayed maturity ~10 years) from the Prespa Region in Macedonia were scrutinized. Prior maturity, tortoises first grow slowly, thereafter gradually increase growth speed, variation in body size and survival probability (mean annual survival rate: 0.30 to 0.70). Potential for indeterminate growth, progressive hardening of the carapace and a survival plateau at the age of five (0.90) promote inter-individual variations in growth trajectories and a wide range of adult asymptotic sizes. Our data question the classical notion of a given size at maturity; instead progressive raise of testosterone levels suggests that maturity is established in growing males ranging from 115 to 140mm in body length. In the Testudo genus females are larger than males; asymptotic estimates of body size show that the studied populations make no exception. Yet, the largest island tortoises are males. With ~100 individuals/ha and an operational sex ratio (OSR ♂/♀) of ~11, male sexual coercion provokes cloacal injuries to females and reduces their body-condition, increasing female mating costs. Male adult survival (0.97) is greater compared to female survival (0.84). Island females do not live long, are discouraged from reproduction and low recruitment further exacerbates OSR-bias, eventually leading to population extinction. Where females suffer and are underrepresented, frustrated males exhibit frequent same-sex sexual behaviours along with extravagant sexual behaviours. The results are discussed in a conservation framework.
... A high SMR could facilitate activity (Taigen, 1983;Bennett, 1980), and thus dispersal distance or speed, which presumably would reduce risks of predation (e.g. Wilbur and Morin, 1988). Indeed, high SMR facilitating an active lifestyle has been considered a driver of the evolution of endothermy (discussed in Bennett, 1980;Taigen, 1983;Gebczynski and Konarzewski, 2009). ...
I estimated standard metabolic rates (SMR) using measurements of oxygen consumption rates of embryos and unfed, resting hatchlings of the diamondback terrapin (Malaclemys terrapin) three times during embryonic development and twice during the early post-hatching period. The highest observed SMRs occurred during mid to late embryonic development and the early post-hatching period when hatchlings were still reliant on yolk reserves provided by the mother. Hatchlings that were reliant on yolk displayed per capita SMR 135 % higher than when measured 25 calendar days later after they became reliant on exogenous resources. The magnitude of the difference in hatchling SMR between yolk-reliant and exogenously feeding stages was much greater than that attributed to costs of digestion (specific dynamic action) observed in another emydid turtle, suggesting that processing of the yolk was not solely responsible for the observed difference. The pre-feeding period of yolk reliance of hatchlings corresponds with the period of dispersal from the nesting site, suggesting that elevated SMR during this period could facilitate dispersal activities. Thus, I hypothesize that the reduction in SMR after the development of feeding behaviors may reflect an energy optimization strategy in which a high metabolic expenditure in support of development and growth of the embryo and dispersal of the hatchling is followed by a substantial reduction in metabolic expenditure coincident with the individual becoming reliant on exogenous resources following yolk depletion.
... Turtles are one of the most vulnerable vertebrate groups in the world, with approximately half of the described species listed as threatened with extinction (Turtle Conservation Coalition 2011). Most species of turtle are long-lived, exhibit delayed sexual maturity, and experience high embryo and juvenile predation rates (Gibbons 1987;Wilbur and Morin 1988;Congdon et al. 1994). Recovery from population-level mortality events is extremely slow, requiring several decades (Brooks et al. 1991;Congdon et al. 1993Congdon et al. , 1994Doak et al. 1994;Heppell et al. 1996;Heppell 1998). ...
Conservation interventions can keep critically endangered species from going extinct and stabilize threatened populations. The species-specific, case-by-case approaches and small sample sizes inherent to applied conservation measures are not well suited to scientific evaluations of outcomes. Debates about whether a method “works” become entrenched in a vote-counting framework. Furthermore, population-level replication is rare but necessary for disentangling the effects of an intervention from other drivers of population change. Turtle headstarting is a conservation tool that has attracted strong opinions but little robust data. Logistical limitations, such as those imposed by the long lives of turtles, have slowed experimental evaluation and constrained the use of replication or experimental controls. Headstarting project goals vary among projects and stakeholders, and success is not always explicitly defined. To facilitate robust evaluations, we provide direction for data collection and reporting to guide the application of conservation interventions in logistically challenging systems. We offer recommendations for standardized data collection that allow their valuable results to contribute to the development of best practices, regardless of the magnitude of the project. An evidence-based and collaborative approach will lead to improved program design and reporting, and will facilitate constructive evaluation of interventions both within and among conservation programs.
... It is known that nesting females continually grow, suggesting that older females are generally larger (Casale et al., 2011). Pelvic opening structure of the species constrains egg size and hence offspring size; larger turtles can therefore produce more eggs, since they can accumulate more resources, and/or bigger eggs, because of their larger pelvic opening (Wilbur and Morin, 1988). There is a positive correlation between egg size and hatchling body size, and larger hatchlings have a higher survival rate (Packard and Packard, 1988). ...
... We assigned unique vital rates to each stage class, and based the survivorship of neonates on field data presented by Bjurlin and Bissonette (2004) and Nagy et al. (2015). Other studies of chelonian species indicate relatively high mortality until maturity (Wilbur and Morin 1988;Brooks et al. 1991;Congdon et al. 1993Congdon et al. , 1994, so we assigned increasing survivorship values to older age classes (Table 1). We also reduced the survivorship of senescent individuals (>80 yr), which still allowed a few tortoises (typically <1% of the simulated population) to attain ages of between 80 and approximately 100 years old, which, in theory, may be possible in the absence of human-caused threats (Berry and Woodman 1984, K. H. Berry, USGS, unpublished data). ...
Agassiz's desert tortoise (Gopherus agassizii) populations are exposed to a variety of anthropogenic threats, which vary in nature, distribution, severity, and frequency. Tortoise management in conservation areas can be compromised when the relative importance of these threats is not well understood. We used HexSim to develop simulation models for desert tortoise populations occupying 2 study areas in the western-central (Superior Cronese in California, USA) and the eastern (Gold Butte-Pakoon in Nevada and Arizona, USA) Mojave Desert, each with a distinct set of site-specific threats. We developed threats models that were parameterized from published information, and conducted independent simulations of threats at varying levels of severity for each study area. Modeled tortoise populations in both study areas were subjected to simulations of threats associated with human presence and subsidized predators. Additional simulated threats in the Superior Cronese model included disease and habitat degradation on land in-holdings, whereas tortoise populations in the Gold Butte-Pakoon model were further exposed to simulations of wildfire, livestock grazing, and feral burros. We used our 2 study area-specific simulation models to rank the threats' relative importance to desert tortoise population viability. Threats more widely distributed in time and space within the modeled conservation areas significantly limited tortoise population growth more than threats that were patchily distributed or temporally dynamic. Our use of a spatially explicit population model allowed us to evaluate and prioritize the effects of threats over site-specific, dynamic, simulated landscapes, which differed from previous modeling efforts for desert tortoises. Our threat prioritization will inform and improve ongoing management efforts attempting to increase desert tortoise population viability by altering anthropogenic disturbance regimes.
... As predicted, the direction of SSD varied more than sexual body shape dimorphism across species. In females, selection for fecundity favors characteristics that enhance the production of large clutches and/or large eggs (Wilbur and Morin 1988;Gibbons and Greene 1990;Iverson 1992b). In chelonians, a reduction of egg size, an increase of maternal body size, or a rounding of the maternal abdomen can convey such an increase in fecundity. ...
In most animal species, it is expected that females should exhibit a greater abdominal volume than males to hold the progeny, when compared with females, males should exhibit more developed attributes that enhance mobility. We tested this hypothesis in the Greek tortoise. In chelonians, a reduction of the openings in the shell improves protection against predation but also constrains the abdominal volume and limits the space available to move the limbs. As expected, our data show that the shell provides a larger abdominal volume relative to tortoise size in females than in males. In males, deep notches in the shell and a reduction of several plastron plates offer more freedom to the limbs and to the tail; these characteristics presumably enhance mating success. Further studies are necessary to assess the applicability of these results in other chelonians, notably freshwater and marine turtles.
... Longevidad, estima de la edad y su relación con el tamaño La edad es uno de los parámetros más dificiles de determinar en quelonios, pues raramente se dispone de seguimientos de individuos desde el momento del nacimiento en la naturaleza. Esto se debe a que casi no hay recapturas de individuos muy pequeños (de entre 0 y 1 años), lo que se explica tanto por su alta tasa de mortalidad, como por su pequeño tamaño, que les hace ser más crípticos que animales de mayor talla (Wilbur y Morin, 1988). Díaz-Paniagua, C., Andreu, A. C., Keller, C. (2015). ...
... Due to the Eastern Box Turtle's life history characteristics in Massachusetts, the population is extremely vulnerable to slight increases in adult and to a lesser degree juvenile mortality rates (Figure 14; Erb 2011). This species is characterized by delayed sexual maturity and high adult survival rates (Wilbur and Morin 1988). Females do not mature until approximately 14 years of age and can live to be more than 100. ...
Conservation Plan for the Eastern Box Turtle
... By focusing our study on terrestrial nesting activity, we show that fences can effectively address the problem of female-biased roadway access, and subsequent mortality, in this semi-aquatic species. Protecting adult females in species with sensitive life history traits can have significant populationwide consequences (Wilbur and Morin 1988), so fences that reduce mortality of adult females represent an efficient use of conservation resources. Our results are encouraging and may be useful in situations dealing with complex habitat usage, as often is found in wetlands systems. ...
Roads can adversely affect animal populations by impacting nesting behavior, causing roadway mortality, and fragmenting habitat. Fences have frequently been implemented to combat road mortality, but at the expense of changing patterns of nesting behavior and increasing population fragmentation. We studied the effectiveness of barrier fences that were installed to reduce road mortality in Diamondback Terrapins (Malaclemys terrapin) seeking nesting habitat along two causeways in coastal southern New Jersey. To determine whether the barriers limited roadway access, we surveyed the ground within five-meters of the fences for evidence of Diamondback Terrapin nest holes in relation to the barrier, indicating whether nesting activity occurred on the marsh side of the fence or on the road side. As a second direct measure of effectiveness, we created a corrugated tubing arena and documented Diamondback Terrapin escape success to examine barrier breaching. Fences were generally effective in restricting Diamondback Terrapin movement: we found far fewer road-side nests (n =39) than marsh-side nests (n = 521), as well as a spatial clustering of road-side nests near the free ends of the fence at one field site. Additionally, the barrier breaching success was positively correlated with gap size between the fence and the ground (P < 0.001), irrespective of body size, indicating that diligent fence maintenance is imperative. Given Diamondback Terrapins’ high probability of road mortality and population sensitivity to female mortality, we conclude that fences are currently essential in their conservation and may warrant greater consideration in the field of turtle conservation, particularly in species with nesting movements that intersect with roads.
... However, in T. marginata, the sister species of T. kleinmanni (Fritz & Bininda-Emonds 2007), males exceed females in size (Bringsøe et al. 2001). The larger female size is probably an adaptation to improve egg production (Congdon & Tinkle 1982, Wilbur & Morin 1988, Gibbons & Greene 1990, Gibbons & Lovich 1990, Forsman & Shine 1995, Loehr et al. 2006. As a consequence, the posterior body region might have enlarged, as supported by the bigger size of anal and femoral scutes in females (see also Geffen & Mendelssohn 1991). ...
We examined 126 wild tortoises to evaluate the shell changes due to sexual dimorphism and ontogenesis by the geometric morphometrics. Adult body shape varies substantially in males and females; adults showed different ontogenetic patterns between sexes: in females the posterior portion of the carapace narrows in the dorsal view, the carapace tends to assume a pyriform shape in the lateral view, and the plastron tends to lengthen of the midline and shows a slight lateral enlargement. Male shape changes towards the posterior portion of the carapace, a bending of the seam between marginal and pleural scutes, allowing the body to assume a hemispherical shape, and ventrally, the plastron narrows strongly, posteriorly. The latter feature was mainly due to the shortening of the anal scutes, probably facilitating copulation by allowing more space to move the long tail. A wider posterior in male angulate tortoises may convey greater stability in male-to-male combat. All the ontogenetic changes suggest a modification of the plastron formula, an important feature for chelonian systematics and taxonomy.
... The first likely correlate (determinant?) of litter size and offspring size is maternal body size; numerous researchers have documented strong allometry in these traits in a wide variety of reptile species (Dunham et al. 1988, Wilbur andMorin 1988). If maternal body size strongly affects reproductive output, then Fig. 2. Relationship between changes in maternal body mass and food intake during vitellogenesis in 30 captive female asp vipers. ...
... Sexual maturity in T. scripta spp. is strictly influenced mainly by body size rather than age (Cagle, 1950;Moll, 1979;Wilbur & Morin, 1988;Gibbons & Greene, 1990), so we inferred the number of potential breeders using only straight plastron length of captured specimens. According to Gibbons (1990), females can be considered mature with a plastron length of 160-190 mm, whereas males reach maturity with a plastron length of 80-130 mm. ...
Trachemys scripta subspecies are massively imported in Europe as a pets, and often released in nature in great number by owners, outside their native range. Now slider turtles are listed as a worldwide major treath for other species and freshwater habitats. In Italy, free-living populations are established in many lakes, rivers and wetlands, and in some areas successful reproduction has been reported. In small urban and periurban parks, human-made or semi-natural wetlands often host slider turtles at high density, with negative impact on freshwater ecosystems. This study was conducted to estimate the consistency of the population hosted into the artificial lakes and ponds of the Parco Nord Milano (Milan Province, Lombardy, Italy). The presence of slider turtles in the park has long been known, but the overall number of individuals, their sex-ratio and their reproductive status were unknown. The turtles were captured with basking traps during multiple capture-recapture sessions, from April to August 2013. The specimens trapped were measured, weighed, sexed and marked with small notch on carapace. The overall number of individuals for each wet zone was estimated with the CMR model for close populations provided by the software Noremark, and the number of potential breeders was estimated by plastron length, according to literature. We marked 156 slider turtles (Trachemys scripta spp.) and, although we did not find clear evidence of successfull reproduction, surprisingly we identified seven individuals with straight carapace lenght (SCL) between 21 and 47 mm.
... Painted turtles demonstrate a polygamous mating system (Wilbur and Morin 1988). Males may sire multiple clutches of eggs (at least in part) with multiple females in a single breeding season and females may lay mixed paternity clutches (Pearce and Avise 2001, Pearce et al. 2002, Uller and Olsson 2008, McGuire et al. 2014). ...
The reproductive strategy of Painted Turtles (Chrysemys picta) has been described as a combination of male courtship and female mate choice. However, in situ field observations from a long-term study of C. picta in Algonquin Provincial Park (Ontario, Canada) suggest that males also demonstrate coercive mating tactics. Males are equipped with prominent tomiodonts, tooth-like cusps of the upper jaw, which seemingly function in restraining mates and result in wounding to the head and neck of females. I propose that the tomiodonts of male C. picta serve as sexual weapons used to coerce females into mating. This thesis has two main objectives: 1) to describe the tomiodont morphology of C. picta, and 2) to test the functional significance of tomiodonts in the mating tactics of male C. picta. In Chapter I, I investigate the overall cranial morphology of C. picta with an emphasis on sexual dimorphism of the tomiodonts. I show that male C. picta have sexually size dimorphic tomiodonts with an optimized arrangement for biting and gripping. In Chapter II, I investigate the soft tissue wounding demographics of a C. picta population as these wounds relate to antagonistic sexual interactions. Using a 24-year dataset on wounding I show that large females experience the highest wounding probability and that elevated rates of wounding occur during the late summer breeding period. In Chapter III, I use behavioural trials during the spring and late summer reproductive seasons to evaluate male reproductive behaviour. I show that small males court females through titillation, whereas larger males employ coercive tactics, such as biting and forced submergence. My findings are contrary to the female choice mating system reported for C. picta and join a growing body of research demonstrating the importance of coercive tactics in the reproduction of male emydid turtles.
... lifespan and growth rate after maturity. As turtles are considered as long-living organisms (Gibbons and Semlitsch 1982;Wilbur and Morin 1988;Shine and Iverson 1995), research on their ecology requires long-term studies. However, there is very little information about the true age of adult turtles, and in many studies only indirect data is available. ...
Data on the straight carapace length (SCL) and plastron length (PL) of eight European pond turtle ( Emys orbicularis ) females were collected in central Poland in 1999 or 2000, and again in 2006 or 2007. All of the individuals were mature each of them was observed during egg laying in 1993 or earlier, and in the following seasons. Differences in lengths between the studied periods have been found for PL, but not for SCL. There was no correlation between final plastron length and the growth rate.
... The survival rate of turtles from egg deposition to hatching and during the first year of life is low (WILBUR & MORIN 1988, IVERSON 1990, HEPPELL 1998. In the northern part of the distribution area climate conditions probably have a strong influence on the mortality rate. ...
... Now it is an intensively studied species (OTA, 1999;HÖDL & RÖSSLER, 2000;FRITZ, 2003), although most reports about the natural history of the turtle are based on short term research. However, turtles are considered as long-living organisms (WILBUR & MORIN, 1988;SHINE & IVERSON, 1995) and as such, for planning protection of the European pond turtle, the value of such studies are limited. SCHNEEWEISS & STEINHAUER (1998) reported that three females of the European pond turtle migrated probably to the same areas as 24 years previously. ...
Nest sites of the European pond turtle Emys orbicularis were marked in the Borowiec Nature Reserve (central Poland) from 1987 to 2002. In this area the turtle could lay eggs once a year. For 13 females, four to 12 nest sites per individual are known from the period studied. Spatial distribution of the sites is presented on maps. Only a small proportion of the female turtles displayed fidelity to a particular nesting sites, whilst others changed their nesting area. Even if there are nesting areas near water bodies, some of the females opt to use other sites. The results of the study suggest that, to gather accurate data about nesting areas used by the turtle, long-term studies are needed. Protection of the used as well as potential nesting areas (on which during short term studies laying was not recorded) could be important for conservation of the turtle.
... Żółwie − zarówno wodne jak i lądowe − są zwierzętami długożyjącymi (Wilbur, Morin 1988). Warunki inkubacji jaj zależą od miejsca złożenia jaj i mają wpływ na przeżywalność (Kolbe, Janzen 2001) oraz na płeć młodych osobników (Janzen, Paukstis 1991). ...
... Additionally, the small size of juveniles allows easy manipulation and ingestion of whole individuals (Janzen et al. 2000;Salmon and Scholl 2014). Along with absence of parental care, these are the two main reasons why predation rate is most pronounced during the first several years of chelonians' lives (Wilbur and Morin 1988;Janzen et al. 2000;Bjurlin and Bissonette 2004). While juvenile chelonians suffer high predation rate from a wide range of predators (e.g. ...
Armoured animals generally exhibit two main antipredator responses: they either flee or stay motionless, withdrawn in their protective armour. The transition between these two threat reactions can be affected by the degree of armour sturdiness. Tortoise shell stiffness gradually increases through ontogeny due to ossification. Additionally, neonates do not benefit from parental protection. Thus juvenile survival could rely strongly on behavioural adaptations. This experimental approach addresses the effects of age (size), morphology, sex and population of origin on the transition between the two strategies. Predator attack was simulated by overturning individuals on their backs. Juveniles displayed bolder threat response comparing to adults. They also spent shorter periods of time withdrawn in shells and inspecting surroundings. Immature tortoises from all localities had high self-righting success, contrary to adults. The deterioration of righting success coincides with age of sexual maturation. Prompt switch from hiding to fleeing strategy in threatened juvenile tortoises implies that natural selection acts strongly on their swiftness and agility. Sexes did not diverge in antipredator displays. Self-righting speed correlated with shell shape in both juveniles and adults. Morphological measurements used in this study affected self-righting speed only in adults. These effects were accompanied with a general negative effect of increase in body size. Further studies should explore how frequency of predator encounters (i.e. experience) shape antipredator behaviour of tortoises. This could have conservation implications, especially for efficient releasing of animals from captive breeding programs.
... However, PEREZ et al. (1979) suggested that females could be capable of developing up to three clutches per year, based on an inspection of ovarian follicles. Laying multiple clutches per year is a common reproductive strategy in chelonian species as it increases the reproductive output of females (WILBUR & MORIN, 1988). In E. orbicularis, females can develop second clutches by fertilizing eggs with stored sperm, and clutches may exhibit multiple paternity (ROQUES et al., 2006). ...
We monitored reproductive females of Emys orbicularis and Mauremys leprosa during the summer of 2001 in Doñana National Park. Radiographs revealed that females of both species may lay at least two clutches from May to July. We recorded incubation temperatures in one nest of each species, and found them to be 24.7ºC in E. orbicularis and 28.7ºC in M. leprosa. Egg incubation lasted 83 days in E. orbicularis, with all the hatch-lings remaining in the nest until we extracted them in October, and 46-53 days in M. leprosa, with three hatchlings emerging one to 12 days after hatching, and three hatchlings remaining in the nest. We detected M. leprosa hatchlings in their first trip to the pond from late August to early October and E. orbicularis hatch-lings from September 18th to September 23rd. © 2014, Asociacion Herpetologica Espanola. All rights reserved.
... Raccoons are now the primary nest predators of most North American turtle populations (Wilbur and Morin 1981) and raccoons can also be important predators of ground nesting birds (Staller et al. 2005, Parsons et al. 2013) and song birds (Thompson 2007, Lumpkin et al. 2012). As hypothesized for fox, coyotes may depredate raccoons, may cause behavioral shifts in raccoons resulting in lower predation on turtle and bird nests, and may depredate turtle and bird nests directly. ...
Currently, Long Island, NY is without a breeding population of northeastern coyote (Canis latras var.), yet recent evidence of dispersing individuals on the island, coupled with the “dogged” momentum of coyote range expansion across North America, suggests a Long Island coyote population is close at hand. We highlighted the fleeting opportunity to takes advantage of this natural experiment by developing a multidisciplinary research framework to investigate the ecological and social impacts of the coyote, pre- and post- range expansion. We reviewed coyote spatial ecology, community ecology, and human dimensions research and identified three components of future investigation: predicting future occupancy, monitoring colonization, testing hypotheses of trophic cascades by leveraging and expanding existing ecological data, and exploring attitudes towards coyotes to better understand and mitigate human-wildlife conflicts. Each proposed component will integrate for a comprehensive investigation to advance theory and applied management of northeastern coyotes.
... Nest-site selection by the adult female turtle may be critical in the survivorship of her offspring (Wilbur and Morin, 1988). For example, nest-site selection may influence the odds that the nest will be depredated or flooded (Kolbe and Janzen, 2002b) and the likelihood that the offspring will reach the water upon hatching (Kolbe and Janzen, 2002a). ...
Understanding why turtles select specific localities to nest over others is important for management and conservation. For some species of freshwater turtle, the same localities are selected year upon year, but it is uncertain whether these localities are selected due to favored environmental conditions, or natal-site homing. The Mary River Turtle (Elusor macrurus) is an endangered freshwater species from Australia, and nesting data gathered between 2004 and 2011 demonstrated that female E. macrurus select to nest in specific localities along the Mary River. Here, we used time-lapse infrared photography and image-identification analysis to assess whether the same individuals returned to the same nesting banks over three consecutive years (nest-site fidelity), and we compared the physical and soil characteristics of nesting areas against other localities along the river where the turtles were not recorded to nest. The photography study illustrated that some females returned to nest at the same locality over consecutive years, whereas others did not; therefore, it is still inconclusive whether E. macrurus exhibits true nest-site fidelity. Preferred nesting areas were all northerly facing and thus exposed to higher levels of solar radiation than nonpreferred areas with similar soil and physical characteristics. Consequently, the preferred nesting areas exhibited significantly greater mean and daily fluctuations in the nest temperature compared with other areas with dummy nests. We suggest that the warmer nest temperature would speed up embryo development; therefore, female E. macrurus select to nest on northerly facing banks in an attempt to reduce the embryo incubation period. A possible reason for this behavior may be to reduce their exposure to nest-raiding predators. The study highlights importance of key nesting areas along the Mary River for the conservation of E. macrurus.
Long‐term ecological studies are critical for providing insight into population dynamics and detecting population declines, particularly for species of conservation concern. However, spatiotemporal variation and logistical challenges make the identification of sudden population declines difficult. We conducted an in‐water capture‐mark‐recapture study of mangrove diamond‐backed terrapins (Malaclemys terrapin rhizophorarum) within Big Sable Creek, in Everglades National Park, Florida. We used an 18‐year dataset (2001 to 2019) incorporating year, sex, hurricane occurrence, and sampling effort to estimate survival using Cormack–Jolly–Seber (CJS) models in Program Mark. Annual survivorship estimates were high from 2001 to 2003 for both sexes (91%–96%) and variable from 2006 to 2014 (77%–92%). Beginning in 2015, survival estimates exhibited a steeper decline (females: 65%, males 75%), and dropped to below 36% by 2018. Because the driver of this apparent population decline is unknown, we created a population projection matrix and used model‐estimated annual survival to simulate annual terrapin population size. We then generated competing scenarios of low survival at various age classes to attempt to reproduce a simulated decline mirroring what we observed from our capture data. A scenario of low adult survival (75%–85%) from 2012 to 2018, possibly in conjunction with no reproduction after 2010, provides estimates of abundance that appear to match simulated annual population size and may indicate that adult emigration/human removal or a drastic drop in recruitment could be responsible for the apparent decline in survival. We explore reasons for this apparent decline and highlight difficulties common to long‐term studies that may influence how declines are interpreted.
Pollution contributes to the degraded state of continental aquatic ecosystems and biodiversity. Some species appear to be tolerant to aquatic pollution, yet little is known about the effects of such pollution on population structure and dynamics. Here, we investigated how wastewater treatment plant (WWTP) effluents of the Cabestany City, in southern France, contribute to the pollution levels of the Fosseille River, and we tested how they could affect population structure and medium-term dynamics of the native freshwater turtle, the Mediterranean Pond Turtle Mauremys leprosa (Schweigger, 1812). Amongst the 68 pesticides surveyed from water samples collected along the river in 2018 and 2021, a total of 16 pesticides were detected, among which eight were found in the upstream section of the river, 15 in the river section located downstream of the WWTP, and 14 in the outfall of the WWTP, exhibiting the contribution of effluents to the river pollution. From 2013 to 2018 and in 2021, capture-mark-recapture protocols were carried out on the freshwater turtle population living in the river. Using robust design and multi-state models, we showed a stable population throughout the study period, with high year-dependent seniority, and a bidirectional transition occurring primarily from the upstream to the downstream river sections of the WWTP. The freshwater turtle population consisted mostly of adults, with a male biased sex ratio detected downstream of the WWTP neither related to sex-dependent survival, recruitment, nor transition, suggesting a male bias in the hatchlings or primary sex ratio. Also, the largest immatures and females were captured downstream of the WWTP, with females having the highest body condition, whereas no such differences were observed in males. This study highlights that population functioning of M. leprosa is driven primarily by effluents induced resources, at least over the medium-term.
The Northwestern Pond Turtle (Actinemys marmorata) ranges from Washington to the southern end of the Central Valley of California. Because of the extensive latitudinal range of the species, it is expected that several life-history traits will vary across the range. Most data on population structure and growth of A. marmorata have been gathered from southern Oregon and California, and reproductive data are sparse north of the southern end of the range. These data are important to a critical understanding of the species' biology and especially for making conservation judgments for a species some consider in need of protection. Thus, we collected key life-history information at the Luckiamute State Natural Area in the mid-Willamette Valley, Oregon. We found that the population structure, adult size, and growth were similar to southern Oregon sites. Clutch size from radiographs was 6.0 1.18 SE (range = 58), smaller than sites at the southern end of the range. The slow growth rate of Luckiamute turtles may be explained by cooler temperature in the Willamette Valley compared to more southerly sites. Still, Luckiamute adults reach a slightly larger size than most turtles in more southerly sites. It just requires many more years to reach sexual maturity and achieve larger sizes in northern areas.
Evolutionary theories predict major differences in life-history trait values of long- and short-lived organisms. Such comparisons have not been possible for chelonians because no short-lived turtle was known until research revealed that chicken turtles (Deirochelys reticularia; DR) have a maximum longevity of 21 yrs. Life-history trait values of DR females are 1) age at maturity of females = 56 yrs; 2) clutches per season = 1.6; 3) annual fecundity = 68 female eggs per female; 4) average juvenile survivorship from age 1 to maturity = 0.60; and 5) low average annual adult survivorship = 0.66. We compared DR with the very long-lived Blanding's turtles (Emydoidea blandingii; EB) in Michigan. Over 14 yrs with no mortality (the minimum age at maturity of EB), the maximum potential fecundity produced by a single female embryo and her mature female offspring was 5 female eggs for EB and 1040 eggs for DR. Comparisons of life table output for approximately stable populations of DR and EB resulted in cohort generation times of 7 and 37 yrs, respectively. The life-history prediction that short-lived organisms should produce smaller offspring was not supported. Average wet mass of eggs is 10 g (8.411.3 g) for DR and 12 g (1014 g) for EB; and average wet mass of hatchlings is 7.3 g (69 g) for DR and 9.3 g (613 g) for EB. Both differences are smaller than expected based on the difference in longevity. Short-lived female DR have an unusual tactic of investing in high fecundity and making substantial body size-specific investment in large eggs, which may reflect why juvenile survivorship had greater influence on population change rates than did adult survivorship. In contrast, adult survivorship had the greatest influence on population change rates of EB. Comparison of cohorts of 1000 female DR and EB hatchlings highlights the differences in life histories of short- and long-lived turtles: all DR would be dead by the time the last female EB had reached maturity at 21 yrs of age.
http://deepblue.lib.umich.edu/bitstream/2027.42/107771/1/hreses.pdf
Recreational activities can be detrimental to biodiversity; for example, off-road vehicle traffic (e.g., ATV riding), which has become increasingly popular in recent decades, can threaten wildlife. Although ATV riding around wetlands may threaten the shallow nests of turtles, there are no data on the effect of ATVs on turtle nests. We studied nest site choice and nest survival in two species of softshell turtles (Apalone mutica and A. spinifera) along a river in Louisiana before (1993–1994) and after (2015–2016) ATV riding became popular at the site to determine whether ATVs were an important source of nest mortality, and whether there was an effect of nest site choice on nest survival. ATVs were the most common source of nest mortality (one-third of nests destroyed); nest mortality was significantly positively related to increased ATV traffic but was not influenced by species or nest site choice. Experiments with surrogate eggs and an ATV revealed that the most vulnerable nests to ATV mortality were those that were shallower, were driven over more slowly, and were turned upon. We recommend restricting the access of riding clubs to the river; enforcement of regulations on isolated riders from adjacent residential areas will be logistically and financially challenging.
Hydrodynamic stability and the ability to turn are two important components of swimming performance in aquatic animals. Stability reduces the energetic costs of swimming, and turning performance facilitates both prey capture and predator avoidance. These components of locomotor performance are typically measured in adults, but juveniles also experience high demands on locomotor performance. To test how stability and turning performance change through ontogeny, we measured the swimming kinematics and performance of hatchling, juvenile and adult pink-bellied sideneck turtles (Emydura subglobosa) as they followed a prey stimulus, and compared these performance metrics in the context of morphometric differences across age classes. We found that in E. subglobosa, adults had the highest stability and lowest turning performance. Younger, smaller turtles are likely to be more susceptible to destabilizing forces and have rounder body shapes than adults, which might enhance turning performance. In contrast , the larger size and more extensive webbing of the limbs of adults might facilitate greater stability. These differences in performance and morphology might reflect common ontogenetic changes in the ecology of aquatic turtles. Hatchlings might benefit from enhanced turning performance to escape predators, whereas the larger size of adults makes them less susceptible to predators that could consume hatchlings whole.
Many reptile and amphibian populations either are pests, are harvested, or are declining towards extinction; however, relatively few are managed. This neglect can be traced to many causes, chief of which is the lack of sympathy that many people have for reptiles and amphibians, especially life-threatening forms such as large or poisonous snakes and large crocodilians. A few reptiles and amphibians are pests, especially some introduced forms such as the brown tree snake (Boiga irregularis) on Guam and the cane toad (Bufo marinus) in many tropical areas. Many reptiles and amphibians are on the U. S. list of endangered and threatened species because of uncontrolled harvest and habitat degradation. International trade in amphibian and reptilian products amounts to hundreds of millions of U. S. dollars annually. Management priorities are often set by nonbiological criteria, such as economic importance and the size and appeal of the animal. Sea turtles and crocodilians receive the most attention. However, priorities set in this manner ignore economically less valuable and less glamorous species that may become endangered by neglect. Common management measures include the protection of species from illegal exploitation, the establishment of harvest quotas, and the captive rearing of endangered species. Management protocols are often hastily implemented without adequate testing for effectiveness. As a group, crocodilians are probably the most effectively managed reptiles. By partially controlling the international market, illegal harvest has been greatly reduced and many formerly threatened populations are recovering. Legal harvest and ranching projects provide the impetus (and often the funds) for high priorities being placed on the research and management of crocodilians. Placing a value on wild crocodilian populations helps conserve wetlands for the benefit of other species of wildlife. Sea turtles are also the recipients of massive management efforts. However, positive results are not easily demonstrated. The huge effort in saving eggs and hatchlings on sea turtle beaches seems to be largely misplaced; long-lived, highly fecund species such as sea turtles are most effectively managed by controlling the mortality of large juveniles and adults. Recently, the reduction of mortality in Kemp’s ridley turtle (Lepidochelys kempi) resulting from the killing of nesting females and drowning in shrimp nets seems to have reversed the plunge towards the extinction of the world’s rarest sea turtle. Management-oriented research on reptiles and amphibians is unevenly distributed among taxa. Crocodilians and sea turtles are the subjects of much research, but reliability of much of it is difficult to judge as it does not undergo the peer-review process of scientific literature. Research is especially needed to identify the critical life stages of sea turtles, in order to better direct management. Because of their ecothermic physiology, the life history and ecology of amphibians and reptiles often differ markedly from those of traditionally managed game species. Amphibians and reptiles can survive long periods without food, have extended periods of inactivity (often including long periods of hibernation), and exhibit strong seasonal changes in habitat utilization. When compared to endotherms, amphibians and reptiles have low rates of parental care and viviparity, high rates of neonate mortality, low frequencies of reproduction, extended age at sexual maturity, and long generation times. These traits suggest that appropriate management of amphibians and reptiles should focus more on protecting subadults and adults than protecting juveniles and neonates. However, most current management practices protect juveniles and neonates, and allow adults to be harvested. Many reptiles and amphibians are difficult to study and require specialized techniques. There is a need for standardized monitoring techniques to allow comparison of different studies and years. Herpetologists could more often choose their organisms and design their studies to better meet the informational needs of wildlife managers. Wildlife management training needs to include reptiles and amphibians, along with birds and mammals, so that managers in the future will consider all taxa in their plans.
Master Thesis in Experimental Biology. University of Barcelona. 2003
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