Judith L. Greene

The Global Decline of Reptiles, Déjà Vu Amphibians

A s a group [reptiles] are nei t h er ‘good ’n or ‘b ad ,’ but ia re intere s ting and unu su a l , a l t h o u gh of m i n or i m port a n ce . If t h ey should all disappe a r, it wo u l d not make mu ch differen ce one way or the other ”( Zim and Smith 1953, p. 9 ) . Fortu n a tely, this op i n i on from the Golden Gu i de Series does not persist tod ay; most people have com e to recogn i ze the va lue of both reptiles and amph i bians as an i n tegral part of n a tu ral eco s ys tems and as heralds of envi ron m ental qu a l i ty (Gibbons and Stangel 1999). In recent ye a rs , as overa ll envi ron m ental aw a reness among the p u blic has incre a s ed , con cerns have come to inclu de intere s t in the eco l ogical state of reptile and amph i bian spec i e s t h em s elves and of t h eir habi t a t s . In c re a s ed aw a reness may s tem from bet ter edu c a ti on abo ut threats to bi od ivers i ty in gen era l , and to reptiles and amph i bians in parti c u l a r, a n d po s s i bly even from an innate attracti on to these taxa ( Kell ert and Wi l s on 1993). From the perspective of many nonscientists, the two vertebrate classes comprising reptiles and amphibians, collectively referred to as the herpetofauna, are interchangeable. For example,the Boy Scout merit badge pamphlet for herpetology was called simply Reptile Study from 1926 to 1993 (Conant 1972, Gibbons 1993), and major zoos (e.g., National Zoo in Washington, DC; Zoo Atlanta; and San Diego Zoo) use only the name “reptile” to refer to the facility that houses both amphibians and reptiles. Thus, public attitudes about the need for conservation of reptiles are probably linked to concern about amphibian declines and deformities (Alford and Richards 1999, Johnson et al. 1999, Sessions et al. 1999), which have been the subject of numerous, well-documented scientific studies. Because amphibians are distributed worldwide, but herpetologists who document amphibian declines are not, it is difficult to accurately assess what portion of amphibian populations are experiencing significant declines or have already disappeared. Furthermore, the means of determining a species’ conservation status is a rigorous and time-intensive process, and therefore counts of “officially” recognized endangered and threatened species are likely to grossly underestimate the actual number of imperiled s pecies (Ta ble 1). The worl dwi de amph i bian decl i n e probl em , as it has come to be known, has garnered significant attention not only among scientists but also in the popular media and in political circles.

Variation in Age and Size at Maturity of the Slider Turtle (Pseudemys scripta)

The adaptive strategy of the slider turtle, Pseudemys scripta, in terms of age and size at sexual maturity is discussed. Populations from a natural aquatic habitat and from a cooling reservoir on the US DOE Savannah River Plant are compared. (HCR)

Drought-Related Responses of Aquatic Turtle Populations

A major drought in South Carolina provided opportunity to observe certain repro- ductive and emigration responses of freshwater turtle populations that have been studied for 15 years. Five species responded differentially to the drying of a major aquatic habitat. Pseudemys scripta and P. floridana emigrated in greater numbers, and fewer females laid eggs than in any previous year. Sternotherus odoratus and Deirochelys reticularia did not reproduce at the level of previous years but did not abandon the aquatic habitat. Reproduction and emigration of Kinoster- non subrubrum were not appreciably different from other years. The differing responses of the species are discussed in terms of the ecological and evolutionary differences between them.

Variation in Reproductive Characteristics of Aquatic Turtles

little effect on the correlation between body size and clutch size. A linear model of the relationship between body size (plastron length) and clutch size explained 67% of the variation for Pseudemys floridana, 56% for P. scripta and 25% for Sternotherus odoratus. A linear model was not useful in describing the pattern in the other two species (r2 = .05, Kinosternon subrubrum and .08, Deirochelys reticularia). However, within each of the five species, maximum clutch sizes of the smallest individuals are never as large as the maximum clutch sizes of the largest individuals. Clutch sizes within a species did not vary significantly among years or populations if the effect of body size was removed. Clutch size varied among months in all species, with a trend of decreasing clutch size during the egg-laying season apparent for P. scripta, P. floridana and K. subrubrum. Individuals of four species were recorded laying more than one clutch within a single egg laying season. The proportion of adult females known to have multiple clutches within a year varied for each species. Monthly timing of egg laying was not consistent for an individual female from year to year. No relationship could be identified between clutch frequency and body size in K. subrubrum or P. scripta, the only species for which adequate samples were available for such an analysis.

Growth, Survivorship and Longevity of Painted Turtles Chrysemys picta in a Southwestern Michigan Marsh

-This paper reports results of a mark-recapture study of painted turtles inhabiting a marsh in Kalamazoo County, Michigan, first begun in 1964-1966 and continued intermittently from 1980-1989. The relationship between plastron length (PL) and age (t) was described by von Bertalanffy growth equations for males PL = 111.8(1 0.792e-0?184t) and females PL = 152.2(1 0.852e-01281). Annual survivorship of males and females (26 yr old) was estimated as 0.64-0.83 and 0.29-0.50, respectively. Annual survivorship of juveniles (<6 yr old) was 0.21-0.51. Based on estimated minimum ages of individuals first captured as adults in the 1960s and recaptured in the 1980s, the four oldest males were 31 and the oldest female was 34 yr old. The oldest known-age male and female were 21 yr and 15 yr old, respectively. A comparison of data from the 1960s with that gathered in the 1980s revealed that the growth rates of juveniles and the density of turtles in the marsh have increased, while survival rates have apparently decreased. We speculate that the enhanced growth rates and population density are the result of warmer and drier weather during the 1980s.

Prolonged nesting forays by common mud turtles (Kinosternon subrubrum)

-Previous research conducted at Ellenton Bay on the Savannah River Site near Aiken, S.C., indicated that gravid mud turtles (Kinosternon subrubrum) leaving the bay to nest remain in the terrestrial habitat for several days. We determined the time required to complete a nesting foray for 68 mud turtles. Nesting forays ranged from 2-29 d (x = 8.7 d, SD = ?5.9 d). To determine why the turtles require so much time to nest, 25 mud turtles were equipped with radio transmitters and followed through the nesting cycle. Gravid mud turtles buried themselves after exiting the bay and most (86%) remained buried until a rainstorm occurred. The turtles nested during rainstorms. All turtles buried themselves after nesting. Most of the buried turtles (67%) then waited for another rainstorm before returning to the bay. The length of time between rains was the main factor influencing the amount of time the turtles required to complete the nesting cycle.

Invasion of New Aquatic Habitats by Male Freshwater Turtles

Long-term field research often reveals how organisms respond to stochastic environmental events such as droughts (Gibbons et al., 1983) or changes in population structure or species composition over time (Tinkle, 1979; Parker, 1984; Pechmann et al., 1991). Studies on aquatic turtle populations have been conducted for more than 25 years on the US Department of Energys Savannah River Site (SRS) near Aiken in the Upper Coastal Plain of west central South Carolina (Gibbons et al., 1982; Gibbons, 1990a; Frazer et al., 1991). One conclusion from these studies is that adult males residing in small, isolated wetlands are more likely than females to move overland and to move greater distances (Morreale et al., 1984). Factors reported to stimulate overland movements by freshwater turtles include travel to and from hibernacula (Bennett, 1972; Gibbons, 1986), pond drying/filling (Cagle, 1944; Sexton, 1959; Gibbons et al., 1983), nesting activity of females (Ernst et al., 1994), and mate-searching by males (Parker, 1984; Gibbons, 1986). Although male and female conspecifics probably exhibit similar terrestrial activity in some situations, differences in reproductive strategies should produce distinct terrestrial activity patterns. Previous studies have suggested that females sometimes travel long distances on land to nest but that males may also travel long distances overland seeking aquatic habitats containing females to inseminate (Morreale et al., 1984; Gibbons, 1986; Brown and Brooks, 1993). If these predictions are correct, males should be more likely than females to encounter new aquatic habitats, including those without conspecific populations. Therefore, colonizing or invading nonresident species should have malebiased sex ratios relative to established resident

Ecology of Chicken Turtles (Deirochelys reticularia) in a Seasonal Wetland Ecosystem: Exploiting Resource and Refuge Environments

Abstract Chicken turtles (Deirochelys reticularia) were studied at Dry Bay, a Carolina bay wetland in South Carolina, USA, between 1994 and 2005. A total of 461 individual turtles was marked from 1993–1998. Minimum ages at maturity for males and females were 2 and 5 yr, respectively. All females reproduced each year, and 60% of reproductive females produced two clutches per season. Clutch size averaged 9.8 eggs, and both clutch and egg size increased with body size. Hatchlings averaged 29.2 mm PL, and body sizes were similar among years. Yearling survivorship varied from 7.0–43.0% (mean = 20.4%) among years. The highest survivorship of a hatchling cohort to age 5 was 0.21. Survivorships of juveniles and adults while in terrestrial refugia were higher than survivorships while in aquatic habitats. No adult females survived a 2-yr drought (2001–2003), and the bay was repopulated by mature males and juvenile females (most from the 1998 hatchling cohort) that had survived the extended drought in terrestrial refugia. Three of those juvenile females matured and produced eggs in 2004. The traits of early maturity, high susceptibility to predation, and shortened longevity characteristic of chicken turtles are consistent with predictions for species that live in seasonally fluctuating and highly unpredictable aquatic habitats.

Selected Aspects of the Ecology of the Chicken Turtle, Deirochelys reticularia (Latreille) (Reptilia, Testudines, Emydidae)

Mark-release-recapture data were collected over a 9-year period on a population of the chicken turtle (Deirochelys reticularia) in South Carolina. The capture of more than 350 individuals provided data on growth rates, reproduction, size structure, and terrestrial activity. Juveniles grew more rapidly than adults, as expected, and adult growth rate appeared to diminish at larger sizes. Some individuals did not grow for periods of 1 to 2 years. Females with eggs were captured in early spring each year as soon as temperatures were consistently warm. None of the few captured during the summer had oviducal eggs; however, nine females with eggs left the aquatic area in early fall. The population size structure of adult females in 1967-70 was not appreciably different from that in 1975-76. The only consistent pattern in terrestrial activity between years was that females emerged for egg-laying in spring and fall and hatchlings entered the water in the spring. Inconsistencies between the present terrestrial activity data and those of a previous study are attributed to habitat features which vary annually. * * * presentation of field data taken over a period of several years. The initial account of the ecology and population dynamics of this species (Gibbons, 1969) was based on approximately 100 field-caught individuals whereas this supplemental material considers more than 350. The re-examination of certain aspects has, as may be expected, refined the quantitative results and led, in some instances, to different interpretations than those originally reported.

Altered spring phenology of North American freshwater turtles and the importance of representative populations

Abstract Globally, populations of diverse taxa have altered phenology in response to climate change. However, most research has focused on a single population of a given taxon, which may be unrepresentative for comparative analyses, and few long‐term studies of phenology in ectothermic amniotes have been published. We test for climate‐altered phenology using long‐term studies (10–36 years) of nesting behavior in 14 populations representing six genera of freshwater turtles (Chelydra, Chrysemys, Kinosternon, Malaclemys, Sternotherus, and Trachemys). Nesting season initiation occurs earlier in more recent years, with 11 of the populations advancing phenology. The onset of nesting for nearly all populations correlated well with temperatures during the month preceding nesting. Still, certain populations of some species have not advanced phenology as might be expected from global patterns of climate change. This collection of findings suggests a proximate link between local climate and reproduction that is potentially caused by variation in spring emergence from hibernation, ability to process food, and thermoregulatory opportunities prior to nesting. However, even though all species had populations with at least some evidence of phenological advancement, geographic variation in phenology within and among turtle species underscores the critical importance of representative data for accurate comprehensive assessments of the biotic impacts of climate change.