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Turtles throughout the world are facing an increasing set of dangers to their survival, including human exploitation for food, pet market and shell trade, habitat loss and degradation, and competition with exotic species (Klemens 2000). Because of these numerous stressors, the International Union for the Conservation of Nature reported that reptile, and specifically turtle populations, are in decline (IUCN Red List 2012). Of the 328 recognized turtle species worldwide, 47.6% are identified as threatened, with 27.4% of these listed as Critically Endangered or Endangered (Turtle Taxonomy Working Group 2010).

The Western Pond Turtle (Actineinys marmorata) is distributed along the Pacific coast of North America west of the Cascade Range and Sierra Nevada, from Washington south to Baja California Norte (Stebbins 1985). This species is an aquatic habitat generalist, utilizing a variety of lentic and lotic systems, but generally preferring slow moving, slack water areas (Holland 1994; Jennings and Hayes 1994). Most of the species' activity occurs in the water, but terrestrial environments are used for hibernation, aestivation, and nesting (Reese and Welsh 1997; Rathbun and others 2002). This species is California's only extant aquatic turtle (Stebbins and McGinnis 2012), and the only turtle indigenous to North America that inhabits a Mediterranean climate (Rathbun and others 2002). Due to these climatic factors and the availability of water, the terrestrial habitat use patterns of any given Western Pond Turtle population can vary widely (Zaragoza and others 2015). For example, turtles inhabiting intermittent water-bodies, which dry up in the summer, will spend a majority of the year in the terrestrial environment (Bondi and Marks 2013; Pilliod and others 2013). In contrast, populations occupying perennial water bodies will remain almost exclusively in the aquatic environment and only leave the water to nest (Lovich and Meyer 2002; Bondi and Marks 2013). Despite this remarkable feature of their biology, populations have been declining throughout their range for over a century (Brattstrom 1988; Hays and others 1999). The Western Pond Turtle is currently a candidate species for listing under the Federal Endangered Species Act (USFWS-Species of Concern, status under review), as well as a Species of Special Concern in California (Jennings and Hayes 1994), as a threatened species in Oregon (Gray 1995), and as endangered in Washington (Hays and others 1999).

Factors recorded for Western Pond Turtle declines include the following: (1) habitat degradation in parts of its range (Pilliod and others 2013); (2) altered or eliminated stream habitat due to dam construction (Holland 1994); (3) spread of exotic competitors like the Red-eared Slider (Trachemys scripta elegans) (Spinks and others 2003; Kraus 2009; Global Invasive Species Database 2010); and (4) non-native and overabundant predators such as American Bullfrogs (Lithobates catesbeianus), Largemouth Bass (Micropterus salmoides), Raccoons (Procyon lotor), Striped Skunks (Mephitis mephitis), Black Rats (Rattus rattus), and Coyotes (Canis latrans) (Moyle 1973; Holland 1991a, 1994; Hays and others 1999). Sunfish (Lepomis spp) are known to compete for invertebrate prey (Hays and others 1999), and Common Carp (Cyprinus carpio) alter or eliminate the emergent vegetation used as forage and concealment habitat by juvenile Western Pond Turtles (Holland 1994). Introduced turtles like the Pond Slider (Tmchemys scripta), Snapping Turtle (Chelydra serpentina), and Painted Turtle (Cluysemys picta) are thought to compete for food, basking spots, and nesting areas (Bouskila 1986; Hays and others 1999; Cadi and Joly 2003; Spinks and others 2003), and have twice the reproductive rate over their native counterpart (Patterson 2006). Epidemic disease (Hays and others 1999; Spinks and others 2003) and respiratory infections, implicated through the introduction of the Red-eared Slider (T. s. elegans; Spinks and others 2003) are also contributing to Western Pond Turtle population declines.

Long-lived species offer many challenges when resource professionals are tasked with evaluating population status and enacting conservation and recovery plans (Congdon and others 1993). The varied life history patterns of the Western Pond Turtle (Bury and Germano, 2008; Ernst and Lovich, 2009; Zaragoza and others 2015) make it difficult to generalize about their habitat use patterns. Their plasticity creates questions when defining conservation strategies, as separate populations may require different approaches (Zaragoza and others 2015). Although occurring over a fairly wide range, there is little published information on their life history, population structure, individual growth rates, and reproductive biology in Central California rangelands. Along the central coast of California, Holland (1985) indicated that the Western Pond Turtle mating season commenced in April and May, with egg laying spanning from June through August. Holland (1985) further suggested that hatchlings overwinter in nests and emerge in March and April. Scott and others (2008) reported that the reproduction of the Pacific Pond Turtle (Actinemys marmorata) in 4 coastal creeks in Central California was like that of individuals in lowland southern California and about a month earlier than at higher elevations and latitudes.

With nearly 6.7 billion ha of the planet's surface classified as rangeland (World Resources Institute 1986), the importance of this land-use practice and its benefits remain controversial. Some authors argue that intense grazing negatively affects the survival of herpetofauna by changing the macrohabitat (vegetation structure) or microhabitat (ground temperature) in areas they occupy (Ficheux and others 2014), decreasing prey abundance (Wilgers and others 2006) or increasing the number of injured animals by trampling (Olivier and others 2010). In contrast, research conducted in Central California showed that managed grazed grasslands had lizard population densities on average 2.75 times higher than those of ungrazed grasslands, and lizard abundance decreased with increased vegetation height and thatch density (Riensche 2008). Furthermore, Kazmaier and others (2001) showed no detectable effect on the demography of the Texas Tortoise (Goplicnis berlandieri) at the Chaparral Wildlife Management Area in Texas, where rotational grazing systems and stocking rates were managed to provide moderate rates of disturbance. But apart from the work by Pilliod and others (2013), who examined the terrestrial movement patterns of 9 Western Pond Turtles utilizing 2 seasonal ponds subject to cattle production at the Carrizo Plain Ecological Reserve, in San Luis Obispo County, California, there is limited comparable data available to guide resource management decisions in this region. Pilliod and others (2013) reported that as water levels receded, all turtles moved in different directions away from the ponds, and made use of different habitats to overwinter (ranging from 10-30 wk). Many aspects of turtle reproductive biology in permanent and semipermanent ponds subject to cattle operations in Central California are not well understood. This work was designed to help fill this research gap by studying the habitat use, movement patterns, and nest site selection of a Western Pond Turtle population in a lentic environment subject to livestock grazing.


Study Area

The study location included a freshwater pond situated in a basin and surrounding hillside uplands located at Clayton Ranch in eastern Contra Costa County, California (UTM Zone 10N, 599455.39E, 4195623.55, NAD83). This permanent pond (0.3 ha) contains submergent and emergent vegetation and has an approximate maximum depth of 7.5 [+ or -] 1.0 m. The types of basking structures at this site include 2 small rocky outcrops 1.5-m long x 0.5-m high and wide (grid locations El and G3, Fig. 1), and a tree stump 2-m tall and 1.5 m in diameter on the eastern edge of grid F3 (not shown in Fig. 1 because it is concealed under the male occurrence number displayed in the figure). Annual pond temperatures range from 5 to 25[degrees]C. Cattle production occurs at this site through a private lease, and livestock have access to the pond as a watering source year-round. Animal grazing in park settings come with resource management trade-offs. While these animals may leave a muddy, pocketed shoreline when drinking during damp soil conditions, they also help minimize the spread of undesirable plants and create a mosaic of low to medium-growing vegetation. Currently, there is no public access or recreational activities at the site.

Clayton Ranch is operated by the East Bay Regional Park District, a 2-county special district with more than 45,200 ha in Alameda and Contra Costa counties. This site provides habitat that supports the life history needs of other special status species like the California Red-legged Frog (Kana aurora draytonii) and the California Tiger Salamander (Ambystoma californiense). Annual grasses and forbs dominate the landscape and trees generally comprise <10% of the canopy cover. The dominant annual introduced grass species include wild oats (Avena spp.), brome grasses (Bromus spp.), and annual fescues (Vulpln spp.). Native and normative forbs and native wildflowers make up the herbaceous cover. Blue Oak (Quercus dougtasii), Valley Oak (Q. lobata), and Interior Live Oak (Q. wislizenii) are the dominant tree species.

Turtle Trapping and Handling

Turtles were captured using floating sundeck and solarium turtle traps that were baited with canned sardines each spring, summer, and autumn. We also opportunistically captured by hand any large turtle observed in the pond shallows or on land. Upon capture, all individuals were sexed using morphological characters, measured, aged, marked, and released at the point of capture. Those possessing a slightly concave plastron, short-thick tail, white throats (older individuals), and a cloaca that extended posterior to the edge of the carapace were classified as male (n = 18). Individuals with generally a flat plastron, thin-long tail, yellow-and black-flecked throat, and cloaca anterior to the edge of the plastron were classified as female (n = 20) (Storer 1930; Holland 1994). Standard turtle measurements (weight, carapace length-curved and width, plastron length and width) were obtained using a 1000-g Pesola hand-scale and a 200-mm caliper (Table 1). Per the work of Germano and Rathbun (2008), the difference between adult and juvenile turtles was defined as 120-mm carapace length, the size at which males develop secondary sexual characteristics in their shells and tails.

Freshwater turtles typically exhibit a pattern of rapid growth in the warm season followed by a lag during the cold season, producing annual rings (annuli) on individual scutes and shields that comprise the carapace and plastron (Sexton 1959; Gibbons 1967; Germano and Bury 1998). Therefore, we estimated age by counting the number of annuli (rings) on each specimen's plastron. Young turtles deposit annuli annually; whereas the growth rate of Western Pond Turtles slows at about the 10-y mark, making the annuli deposit difficult to count and less reliable for aging (Bury and Germano 1998). Similar to what Germano and Rathbun (2008) concluded, some turtles can only be classified as older than 15 y because of their worn rings and beveled scute edges; these animals are large and are no longer depositing discernable rings. Therefore, we estimated the age of young turtles ([less than or equal to]10 y) by counting all visible annuli (Ashton and others 2011). For individual identification, turtles were marked by filing a triangular notch in or on more marginal shields (scute notching) using the Holland carapace code system (Holland 1994).


In spring (April-May) 2011, 36 turtles were fitted with ATS R1850 transmitters, each weighing 12 g (ATS Tracking Systems, Isanti, MN), and attached using 5-rrtin waterproof gel epoxy. Two additional female turtles were hand captured as they were leaving the pond in June 2015, and were temporally fitted with transmitters and followed to their oviposition sites several days later, after which their transmitters were removed. To remain within the suggested 3 to 5% body-weight ratio and to avoid alteration of the turtle's behavior, these 38 individuals fitted with transmitters weighed >320 g. To avoid interference during mating (Boarman and others 1998), the transmitter antenna was left free to prevent snagging on vegetation, and the transmitter was glued to the specimen's 3rd pleural scute.

Movement patterns were monitored using an ATS R410 model hand-held receiver (Advance Telemetry Systems, Isanti, MN) with a 3-element antenna. Based on perceived accuracy, triangulated turtle detections for both sexes were mapped as location points on a 15- x 15-m pond grid (Fig. 1). During autumn and winter (September through the end of February 2011-2016), 36 turtles of both sexes (18 males and 18 females) were located in the pond a minimum of once each week to document movement patterns, and to verify hibernation locations and habitat features that were associated with overwintering hibernacula. From early spring (March through early May 2011-2016), we attempted to triangulate the position of all turtles (both sexes) and record their movement patterns within the pond several times a week. From late spring through summer (after the 3rd week of May until mid-August 2011-2016), we attempted to locate turtles almost daily to document migrations to and from the pond, dispersal corridors, and nesting sites. During the evening (May through July), habitat use, movement patterns, and nest-site locations of gravid females were tracked and recorded using a GPS. Several microhabitat characteristics within a 1-[m.sup.2] radius of each nest site were identified. The following components were recorded: (1) distance from pond to ovipositioning sites; (2) proximity to nearest tree; and (3) vegetation measurements, which included percent cover, height, and residual-dry-matter level. Ambient air and pond water temperatures were recorded during each survey period.

Statistical Analyses

We performed a series of statistical analyses (Chi-square tests for equal proportions, and Chi-square likelihood ratios) using JMP Pro 11 (JMP[R]) with significance set at P = 0.05. We used these tests to: (1) determine if male and female turtles were using all grid sections of the pond environment equally; (2) further refine the analysis of male and female turtle habitat use patterns in this aquatic resource; (3) determine if there was any difference in female turtle nest directions (slope and aspect); and (4) further improve analysis of the movement of gravid females from the pond into the surrounding terrestrial landscape.


Of the 38 turtles captured, 33 were tracked through the entire duration of this study. This difference in sample size was due to the death of 1 animal while it was on land, which showed obvious signs of predation by Raccoons (Procyon lotor), the loss of transmitters from 2 females, and the 2 females that were only followed during their movement from the pond to their oviposition sites in June 2015. We most likely lost track of the 2 females with lost transmitters because of battery failure or predation. We believe it is unlikely that these missing animals moved out of the search area on their own power.

A total of 2526 individual turtle pond location points were recorded. Overall, turtles remained in the pond with the following 3 exceptions: (1) to bask ([less than or equal to]1 m from the water's edge); (2) to nest; and (3) to temporarily move into an ephemeral upper pond to forage on 2 occasions in spring while it held water. An overall Chi-square likelihood ratio of 160.092 (P < 0.0001) indicated that both sexes were not distributed in equal proportions within the pond (Fig. 1). The Chi-square likelihood ratios for each sex were 1108.624 (P < 0.0001) for females and 293.2908 (P < 0.0001) for males. Further, of the 35 grids in Figure 1, female turtles were observed at significantly higher proportions in grids A2, B2, C2, D2, F2, and F3 than in the other grids; male turtles were observed at significantly higher proportions in grids B2, C2, E4, F3, F4, and G2.

Female turtles, presumed gravid, were tracked using telemetry and visually to their respective ovipositing sites. Each year this nesting activity peaked during the first 2 wk in June, occurring between 16:00 to 20:30, with all females eventually returning to the pond in the evening. Ranging from the last week in May to the 1st week in July, monitored females moved an average of 24.4 m (s = 17.5 m) from the pond to build their nests primarily on south-facing slopes with good sun exposure (Chi-square likelihood ratio = 33.727, P < 0.0001; Fig 2). Furthermore, gravid females moved at a significantly higher proportion (Chi-square likelihood ratio = 269.6896, P < 0.0001) from pond grids A2, B2 and C2 into the surrounding terrestrial landscape to nest (Fig. 1, Fig. 2). Nest sites (n = 34; Fig. 2) were in dry soil in both ungrazed and seasonally grazed areas. The mean aspect of nest sites was 134[degrees] (s = 31.9[degrees]); the mean residual-dry-matter level at nest sites was 1345 lbs/ac (s = 266 lbs/ac) or 1510 kg/ha (s = 121 kg/ha); the mean annual grass height at nest sites was 33.1 cm (s = 18.5 cm); the mean vegetation cover at nest sites was 85% (s = 5%), and the mean distance of nests to nearest tree was 25.9 m (s = 17.8 m).


Like other freshwater turtle species, some Western Pond Turtle populations remain in the water year-round, with females moving onto land for only short periods to lay eggs (Reese 1996; Holte 1998; Lovich and Meyers 2002; Rathbun and others 2002). This is also true for the turtles we studied at Clayton Ranch. However, the males and females in our study were using different areas of the aquatic environment and were not present in equal proportions in the pond grids (Fig. 1), which was statistically significant. This phenomenon of male and female differential distribution in the pond might be correlated with the movement behaviors and home-range size requirements of each sex. In the Mad River drainage of northern California, Bondi (2009) reported that male Western Pond Turtles made larger average movements than females, and had larger linear aquatic home ranges. Previous research by Bury (1972) at Hayfork Creek, another northern California location, also showed that males have greater home ranges (1.0 ha) compared to those of females (0.3 ha).

Little is known, however, about why the Western Pond Turtle selects different micro-and macrohabitats; even their thermal biology, which is likely an important consideration in overwintering locations, is poorly studied (Pilliod and others 2013). At Clayton Ranch, females were observed at significantly higher proportions in south-facing pond grids A2, B2, C2, D2, F2, and F3 (Fig. 1). The bank on this side of the pond has a 4 to 1 slope (14[degrees]), which is relatively less steep than other areas around the pond. It is plausible that the energetic demands for climbing steeper slopes than 14[degrees] may be one reason for the limited distribution of females in the study pond. The use and importance of basking sites to this species has also been discussed by Bury and Wolfheim (1973), Holland and Goodman (1996), and Reese and Welsh (1998), and likely plays a role in female distribution in a pond. As stated by Cook and Martini-Lamb (2004), conventional wisdom suggests that aerial basking maximizes solar exposure, which is important in thermoregulation. Like these studies, we often observed our turtles basking in full sun on banks, snags, exposed rocks, and floating logs in these south-facing pond grids. Conversley, significantly higher proportions of males were observed in north-facing pond grids E4, F3, F4, and G2, as well as in south-facing grids B2 and C2. The north-facing pond bank is nearly a 2 to 1 slope (26[degrees]), and includes a rock outcrop and a large stump. Gibbons and others (1990) reported that movements within turtle populations are primarily related to feeding, reproduction, basking, and hiding. Furthermore, there is a tendency for male terrapins to have larger home ranges and average movements than females, which can be attributed to mate seeking (Gibbons and others 1990). In conjunction with basking behavior, the growth and maturation of freshwater turtles is influenced by ambient and water temperature (Williamson and others 1989; Brown and others 1994). Therefore, it is possible to conclude that the high presence of males in the 2 south-facing grids B2 and C2, where females were observed in significantly higher proportions than males, may be related to reproduction, whereas their frequency of occurrence in other pond grids (such as E4, F3, F4, and G2) is associated with basking behavior.

The terrestrial movement patterns of overwintering Western Pond Turtles vary throughout its range. For example, turtles along the Trinity River, California, move into the uplands in September and bury themselves into leaf and needle litter to avoid high water flows (Reese and Welsh 1997). Other comparative data looking at Western Pond Turtle responses to the highly seasonal, Mediterranean climatic conditions of California, showed that radio-tagged animals took refuge on land to avoid back-to-back combinations of late-summer drought and winter flooding (Rathbun and others 2002). Conversely, no such terrestrial movement pattern was observed at the Clayton Ranch pond. All of the turtles fixed with transmitters in our study overwintered each year in the same relative location (grids B2 and C2), underwater near the pond inlets. While our findings are limited to a permanent lentic environment, with no comparisons available, others researchers studying lotic systems have reported individuals returning to the same overwintering location each year and generally using only 1 habitat type (Reese 1996; Goodman 1997; Bondi 2009). Reese (1996) summed up the propensity for terrestrial overwintering by Western Pond Turtles living in permanent ponds to be much lower than populations residing in streams and rivers. Basically, turtles residing in riverine systems overwinter in the surrounding upland environments at a much higher rate to avoid being washed down stream during high flows; whereas, those inhabiting permanent ponds do not tend to move out into the terrestrial environment to overwinter.

Typically, most gravid females left the Clayton Ranch pond the last week of May and the first 2 wk of June to construct their nests. These observations are consistent with those of Reese and Welsh (1997), who reported that the peak of terrestrial movement of nesting females occurred in June, typically from 17:00 to sunset. An interesting aspect of our study is that females moving from the pond to ovipositing sites used pond inlet grids A2, B2, and C2 in higher proportions. This behavior may be attributed to them selecting a path with <14[degrees] slope to reduce their energy demands prior to egg laying. Rathbun and others (1992) and Resse and Welsh (1997) noted that gravid females can make multiple trips overland before ovipositing, and it is thought that these females are gaining a thermoregulatory advantage by spending time buried on land during pre-ovipositional development of the embryo. As reported by others, microhabitat-basking sites used by this species is dynamic in space and time and can include aerial basking, burying themselves in warm sand (Rathbun and others 2002), and lying in algal mats that are warmer than the ambient temperature of the air and water (Germano and Rathbun 2008).

While Western Pond Turtle nesting sites can be as far as 400 m from water (Storer 1930; Holland 1991a, 1991b; Rathbun and others 1992), females in our study moved on average 24.4 m (s = 17.5 m) to oviposit on south-facing slopes with mean aspects of 134[degrees] (s = 31.9[degrees]). All nest sites were in dry soil, with good sun exposure in seasonally grazed annual grasslands. There was no evidence of nest-site fidelity, which was possibly a reflection of our sample size. In a study in northern San Luis Obispo County, California, Rathbun and others (2002) reported that most of their radio-tracked gravid females left their creeks during June, traveling on average 28 m to oviposit in sunny, upland habitats with low vegetation structure. They also reported no evidence of strong nest-site fidelity by the turtles they tracked for more than 2 or more consecutive years. Our results are also consistent with Holland and Bury (as cited by Spinks and others 2003), who reported that female Western Pond Turtles seem to prefer sites situated on well-drained clay-silt soils, with slopes <15[degrees], that are dominated by grass and herbaceous vegetation, but lack shrubs and trees.

With increasing urbanization, the Western Pond Turtle faces compounding disturbance effects resulting from humans, pets, road traffic deaths, habitat loss and degradation, introduced species, and pollution (Spinks and others 2003; Rosenberg and others 2009; Bury and others 2012; Germano and others 2012). Some sewage-treatment facilities in the San Joaquin Valley, California, provide habitat for Western Pond Turtles that could provide stock for future reintroductions of this species into more natural, rehabilitated areas nearby should the turtle become extirpated over a portion of its range (Germano 2010). But, as our rural Central California landscapes rapidly give way to subdivisions, and habitats are degraded, the biggest challenge facing the chelonian conservation community may be finding ranchers with hoofed stock willing to participate in a prescribed grazing program.

Our findings provide a potential framework for helping resource practitioners develop conservation strategies for the survival of the Western Pond Turtle in Central California rangelands, as well as an argument for the preservation of open space. By integrating our results with data from the literature about the importance of aquatic and terrestrial habitats for other freshwater pond turtle species (Ficetola and others 2004), several suggestions for habitat management plans emerge. First and foremost, to ensure the persistence of these species, it is important to preserve large natural habitat areas (Ficetola and others 2004). Second, a 250- to 300-m buffer zone encompassing the areas of most terrestrial activity for many freshwater turtles has been suggested (Burke and Gibbons 1995; Semlitsch and Bodie 2003). Ideally, this terrestrial area should include open areas with soft soil and good sun exposure (south-facing slopes) for nesting (Andreas 2000; Ballasina and Lopez-Nunes 2000; Chelazzi and others 2000). Third, as has been shown with the federally threatened Bog Turtle (Glyptemys muhlenbergii), efforts to preserve viable populations of the Western Pond Turtle may depend on low-intensity, pasture-based dairy- and beef-farming activities, such as occur at our study site. These activities can help maintain habitat containing low-growing herbaceous vegetation, which is important for the continued survival of Western Pond Turtle populations, and thus prevent the establishment of tall-growing exotic or invasive vegetation on formerly grazed sites, which could have a negative effect on Western Pond Turtle survival (Tesauro and Ehrenfeld 2007). Last, because there is the potential for some life stage of the Western Pond Turtle to be present in both the aquatic and terrestrial environments during every season of the year, all management approaches across this landscape must regulate human and livestock access during periods of critical life-history stages such as egg laying and hatchling development. One such suggestion would be to implement a management plan like that of Ficheux and others (2014), where the timing and stocking rates of cattle were changed to moderate grazing intensity outside of the active turtle period. Zaragoza and others (2015), who reported on the terrestrial habitat use of Western Pond Turtles inhabiting ephemeral ponds in the Sierra Foothills, suggested limiting grazing activities to the time periods when the turtles are resident in the water (late winter through spring in their study) to ensure that the turtles are not disturbed when using their terrestrial habitat for nesting, aestivation, and overwintering. Future inquiry is needed to understand the long-term population dynamics at our site, as well as at other regional locations, which are subject to year-round livestock operations. Also warranted are investigations into the thermal biology of this species and their responses to drought on Central California rangelands.


Survey efforts and equipment were largely funded by the Regional Parks Foundation, Contra Costa County Fish and Wildlife Commission, and the California Department of Fish and Wildlife. I would also like to express my sincere gratitude to the following individuals that helped make this work possible: P Alvarez, P Barale, T Barazoto, N Beadle, D Bell, K Boettcher, M Clark, N Chu, R Crosby, K Crosby, H Crosby, L DeLa Pena, E DeLa Pena, J Dorcy, D Drueckhammer, A Dwyer, J Geoghegan, S Gidre, T Groff, C High, H High, S High, E Hopkins, R Kaufmann, K Kenworthy, S Lockett, C Newell, M Marrow, B Pinomaki, M Riensche, S Riensche, D Riensche, N Riensche, R Riensche, and B Wainwright.


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Submitted 24 April 2018, accepted 26 March 2019. Corresponding Editor: Robert Hoffman.


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TABLE 1. Meristic attributes fur captured Western Pond Turtles.
"[+ or -]" = standard deviation.

   Category                           Male

Total number                               18
Mean age (y)     [greater than or equal to]15

Mean weight (g)                           628.0 ([+ or -]132)
Mean carapace                             173.0 ([+ or -]18.0)
length (mm)
Mean carapace                             125.5 ([+ or -]10.5)
width (mm)
Mean plastron                             142.0 ([+ or -]12.0)
length (mm)
Mean plastron                              85.0 ([+ or -]7.0)
width (mm)

   Category                          Female

Total number                               20
Mean age (y)     [greater than or equal to]15

Mean weight (g)                           643.0 ([+ or -]112.0)
Mean carapace                             166.0 ([+ or -]11.0)
length (mm)
Mean carapace                             124.0 ([+ or -]8.0)
width (mm)
Mean plastron                             143.0 ([+ or -]7.5)
length (mm)
Mean plastron                              86.5 ([+ or -]5.5)
width (mm)
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Author:Riensche, David L.; Riensche, Sarah K.; Riensche, Rebekah E.; Hoffman, Robert
Publication:Northwestern Naturalist: A Journal of Vertebrate Biology
Geographic Code:1MEX
Date:Sep 6, 2019

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