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Ecology of the Redbelly Snake (Storeria occipitomaculata) Using Mesic Habitats in South Carolina
Abstract
The population ecology of the redbelly snake Storeria occipitomaculata from three mesic habitats in South Carolina was studied between 1978-1982. Discrete pulses in seasonal activity were related to the drying cycle of the habitats. Snakes presumably followed their main food resource (slugs) along a soil moisture gradient. Young-of-the-year were first found in July or August and averaged 61 mm snout-vent length (SVL). Testes of males and ovarian follicles of females began to enlarge during their 2nd year at SVLs of 118 mm (males) and 126 mm (females). First reproduction in both sexes presumably occurred at 2 years of age. Mature females contained an average of nine enlarged ovarian follicles. The number of follicles increased with SVL. Males and females were not significantly different in SVL, but females were heavier and males had longer tails. Sex ratio of the sample was 1:1. The authors marked 61 individuals of the 249 that were captured during the study and recaptured four. The low recapture rate suggests that population sizes were large or turnover was rapid. A comparison between life history traits of Storeria occipitomaculata in South Carolina and Michigan showed that body size in South Carolina was smaller at birth and at maturity, but that litter size was slightly larger, than in Michigan. Age at maturity, age at first reproduction and frequency of reproduction were the same in South Carolina and Michigan.
... Our study adds to a growing number of ecological studies of Red-bellied Snakes across this species' broad geographic range (Blanchard 1937, Brodie and Ducey 1989, Cairns et al. 2018, King 2022, Meshaka and Klippel 2011, Semlitsch and Moran 1984, Virgin and King 2019, Willson and Dorcas 2004. Despite ranking third among our 4 local species in terms of total captures, Red-bellied Snakes were nonetheless common, with 93 captures in our study; it has also been described as common in New York (Gibbs et al. 2007) and Pennsylvania (Hulse et al. 2001). ...
... This species was encountered regularly throughout the summer, and gravid females were particularly common under rocks in open areas leading up to parturition in July and early August. The abundance and seasonal activity of this species in our study area contrasts with observations from southern portions of this species' range, where Red-bellied Snakes are noted as being uncommon or rare (Werler and Dixon 2000) and most frequently encountered in the spring and fall (Ernst and Ernst 2003, Semlitsch and Moran 1984, Willson and Dorcas 2004. Likewise, although this species is generally described as being associated with forested or mesic habitats in the southern US (Johnson 2000, Semlitsch and Moran 1984, Willson and Dorcas 2004 and in New York (Gibbs et al. 2007), our captures of this species were highest in the old field and yard, indicating a preference for grassy, open-canopy habitats; only 1 Red-bellied Snake was ever captured along the road through dense spruce-fir forest. ...
... The abundance and seasonal activity of this species in our study area contrasts with observations from southern portions of this species' range, where Red-bellied Snakes are noted as being uncommon or rare (Werler and Dixon 2000) and most frequently encountered in the spring and fall (Ernst and Ernst 2003, Semlitsch and Moran 1984, Willson and Dorcas 2004. Likewise, although this species is generally described as being associated with forested or mesic habitats in the southern US (Johnson 2000, Semlitsch and Moran 1984, Willson and Dorcas 2004 and in New York (Gibbs et al. 2007), our captures of this species were highest in the old field and yard, indicating a preference for grassy, open-canopy habitats; only 1 Red-bellied Snake was ever captured along the road through dense spruce-fir forest. Semlitsch and Moran (1984) attributed use of mesic habitats by Red-bellied Snakes to availability of their primary prey, slugs. ...
... Red-bellied Snake (Storeria occipitomaculata) occupies most of eastern North America and is widely distributed in Canada, reaching the northwestern edge of its range in eastern Saskatchewan (Ernst and Ernst 2003). Across its range there have been a number of studies of this species (e.g., Blanchard 1937;Lang 1969;Semlitsch and Moran 1984;Willson and Dorcas 2004;Brown and Phillips 2012) but there has been little research at its northern range limit, with the exception of two natural history observations (Criddle 1937;Gregory 1977). Storeria occipitomaculata is a small-bodied, cryptic snake that comes in several ground-shaded dorsal colour morphs and has a bright, reddish-orange ventral surface. ...
... They are viviparous, likely with some limited placental provisioning (Blackburn et al. 2009). This species, like other members of the genus Storeria, feeds primarily on molluscs (Trapido 1944;Brown 1979;Semlitsch and Moran 1984;Pisani and Busby 2011) although not exclusively (Ernst and Ernst 2003). With few species of slugs and snails native to the northwestern edge of its range, local diet remains unknown. ...
... This species is considered uncommon to rare throughout much of its range (Ernst and Ernst 2003) but it can be abundant in suitable habitat (Lang 1971). Little is known about population densities for this species, although most studies have recorded low recapture rates (Blanchard 1937;Gregory 1977;Semlitsch and Moran 1984). Typically, S. occipitomaculata inhabit thick grassy, herbaceous, and shrubby vegetation, and also can be found in wetlands, riparian areas, and along forest edges and in old field and prairie habitats (Wright and Wright 1957;Cook 1984;Pisani and Busby 2011) as well as drier grasslands habitats (Lang 1969;Brown and Phil -lips 2012). ...
Northern regions limit ectotherms to relatively short periods of feeding and breeding interrupted by long periods of inactivity. This may force cool-climate ectotherms into different ecological or demographic trade-offs than their southern conspecifics. Our aim is to examine demography, morphology, reproduction, habitat use, and hibernation by populations of Red-bellied Snake (Storeria occipitomaculata) near their northern range limit. This research was conducted in southwestern Manitoba and data on summer activity were collected from April to September 2007–2009 using coverboard and pedestrian surveys. Hibernation sites were monitored over three winters (2007–2008, 2008–2009, and 2009–2010), and thermal profiles of Formica ant mounds were collected in 2008–2009 and 2009–2010. Females reached sexual maturity at a smaller size than most other populations that have been reported but appear to have similar clutch sizes to the rest of the range. The majority of adult females captured at our summer sites were gravid (96%) suggesting annual reproduction, and activity patterns suggest fall breeding. Near its northern range maxima, this species appears to use relatively warm habitat, have rapid reproduction, and co-opt ant mounds to survive in a difficult climatic environment. Much remains unknown and future studies should further examine the variation in size at maturity and the relationship between body size and clutch size. In addition, little is known about diet, benefits of fall mating, use of open prairie habitats, and late-season migration by S. occipitomaculata.
... The worm snake (Carphophis amoenus), ringneck snake (D. punctatus), brown snake (Storeria dekayi), redbellied snake (S. occipitomaculata), and smooth earth snake (Virginia valeriae) all have extensive ranges in the eastern United States and in many areas can be quite common. Nevertheless, detailed studies of the ecology of these species are few (but see Brodie and Ducey 1989;Clark 1970;Fitch 1975Fitch , 1999Russell and Hanlin 1999;Semlitsch and Moran 1984) and none have been conducted in the Piedmont region of the Southeastern United States. ...
... Initially, large C. amoenus and D. punctatus were marked by pit-tagging (Russel and Hanlin 1999), however we discontinued this process after several months out of concern that we were causing undo injury to snakes. As we had no recaptures of marked snakes and other studies on these species have reported low recapture rates (Russel andHanlin 1999, Semlitsch andMoran 1984), we decided that impacts of pseudoreplication on our results were minimal. ...
... We set the size of sexual maturity at 170 mm SVL for both sexes of C. amoenus (Palmer andBraswell 1995, Russel andHanlin 1999), 180 mm SVL for male and 218 mm SVL for female D. punctatus (Mitchell 1994), 150 mm SVL for male and 175 mm SVL for female S. dekayi (Mitchell 1994), 118 mm SVL for male and 126 mm SVL for female S. occipitomaculata (Semlitsch and Moran 1984), and 125 mm for male and 185 mm SVL for female V. valeriae (Blem and Blem 1985). Morphological comparisons were made using single-factor ANOVA (JMP; Sall and Lehman 1996). ...
In many areas, small fossorial snakes are among the most abundant vertebrates present; yet, the ecology of these species remains poorly understood. Between 1999 and 2002 we collected 210 small fossorial snakes representing five species in a small area of northern Mecklenburg and southern Iredell Counties, North Carolina. The eastern worm snake (Carphophis amoenus; n = 116) was the most frequently captured species in this region, with fewer numbers of ringneck snakes (Diadophis punctatus; n = 44), brown snakes (Storeria dekayi; n = 24), redbellied snakes (S. occipitomaculata; n = 20), and smooth earth snakes (Virginia valeriae; n = 6). The three most abundant species exhibited significant sexual dimorphism, with females being larger and having shorter relative tail lengths than males. Carphophis amoenus were more abundant in dry upland forest than D. punctatus, which were most prevalent in moist, lowland forest. Snake activity was weakly correlated with environmental conditions. A peak in activity of male C. amoenus, D. punctatus, and S. occipitomaculata during September suggests fall breeding seasons for these species.
... The worm snake (Carphophis amoenus), ringneck snake (D. punctatus), brown snake (Storeria dekayi), redbellied snake (S. occipitomaculata), and smooth earth snake (Virginia valeriae) all have extensive ranges in the eastern United States and in many areas can be quite common. Nevertheless, detailed studies of the ecology of these species are few (but see Brodie and Ducey 1989;Clark 1970;Fitch 1975Fitch , 1999Russell and Hanlin 1999;Semlitsch and Moran 1984) and none have been conducted in the Piedmont region of the Southeastern United States. ...
... Initially, large C. amoenus and D. punctatus were marked by pit-tagging (Russel and Hanlin 1999), however we discontinued this process after several months out of concern that we were causing undo injury to snakes. As we had no recaptures of marked snakes and other studies on these species have reported low recapture rates (Russel andHanlin 1999, Semlitsch andMoran 1984), we decided that impacts of pseudoreplication on our results were minimal. ...
... We set the size of sexual maturity at 170 mm SVL for both sexes of C. amoenus (Palmer andBraswell 1995, Russel andHanlin 1999), 180 mm SVL for male and 218 mm SVL for female D. punctatus (Mitchell 1994), 150 mm SVL for male and 175 mm SVL for female S. dekayi (Mitchell 1994), 118 mm SVL for male and 126 mm SVL for female S. occipitomaculata (Semlitsch and Moran 1984), and 125 mm for male and 185 mm SVL for female V. valeriae (Blem and Blem 1985). Morphological comparisons were made using single-factor ANOVA (JMP; Sall and Lehman 1996). ...
In many areas, small fossorial snakes are among the most abundant vertebrates present; yet, the ecology of these species remains poorly understood. Between 1999 and 2002 we collected 210 small fossorial snakes representing five species in a small area of northern Mecklenburg and southern Iredell Counties, North Carolina. The eastern worm snake (Carphophis amoenus; n = 116) was the most frequently captured species in this region, with fewer numbers of ringneck snakes (Diadophis punctatus; n = 44), brown snakes (Storeria dekayi; n = 24), redbellied snakes (S. occipitomaculata; n = 20), and smooth earth snakes (Vir-ginia valeriae; n = 6). The three most abundant species exhibited significant sexual dimorphism, with females being larger and having shorter relative tail lengths than males. Carphophis amoenus were more abundant in dry upland forest than D. punctatus, which were most prevalent in moist, lowland forest. Snake activity was weakly correlated with environmental conditions. A peak in activity of male C. amoenus, D. punctatus, and S. occipitomaculata during September suggests fall breeding seasons for these species.
... The use of a drift fence with pitfall traps is a common sampling technique for studies of individual species or herpetofaunal communities (e.g., Dole, 1971;Gibbons and Bennett, 1974;Gibbons and Semlitsch, 1982;Semlitsch and Moran, 1984;Semlitsch and Pechmann, 1985;Gibbons, 1990). The fences may be constructed of many types of materials, including metal, plastic, or tarpaper, and can be arranged to completely enclose a specific area or sample habitats in a variety of non-continuous configurations (Campbell and Christman, 1982;Gibbons and Semlitsch, 1982;Jones, 1986). ...
... The use of a drift fence with pitfall traps is a common sampling technique for studies of individual species or herpetofaunal communities (e.g., Dole, 1971;Gibbons and Bennett, 1974;Gibbons and Semlitsch, 1982;Semlitsch and Moran, 1984;Semlitsch and Pechmann, 1985;Gibbons, 1990). The fences may be constructed of many types of materials, including metal, plastic, or tarpaper, and can be arranged to completely enclose a specific area or sample habitats in a variety of non-continuous configurations (Campbell and Christman, 1982;Gibbons and Semlitsch, 1982;Jones, 1986). ...
... However, several authors have noted that some species may not be amenable to accurate census using this technique, particularly large snakes, large turtles, or treefrogs (Gibbons and Bennett, 1974;Gibbons and Semlitsch, 1982;Jones, 1986). Few investigators in amphibian studies address the importance of trespass, i.e., climbing over or under the fence (Semlitsch, 1985;Semlitsch and Pechmann, 1985). For example, Pechmann and Semlitsch (1986) stated that they had no reason to suspect diel variation in trespass rates, whereas Pechmann et al. (1989) stated that trespass rates probably did not vary among sites and years. ...
Five years of field observations suggest that amphibians inhabiting a sandhills community are able to circumvent a drift fence-pitfall trap enclosure as they move toward and away from an ephemeral pond. Trespass rates varied depending on species and showed no tendency to increase or decrease as the study progressed. Laboratory trials confirmed that frogs easily crossed the fence by walking up the side or hopping over it. Frogs crossed the fence readily regardless of sex or whether the frog was an adult or juvenile. Although striped newts did not climb over the fence in the laboratory, they may use tunnels to go under fences under field conditions. Other species may burrow directly under the fence. A priori assumptions about a species' ability to climb a fence, or that trespass rates do not vary temporally or among sites, are unwarranted and may lead to misinterpretations of the results from studies using drift fences and pitfall traps.
... data). Semlitsch and Moran (1984) scale-clipped Storeria occipitomaculata as small as 0.4 g. PIT tags have been used to mark 2.0 g (Russell and Hanlin 1999) to 2.5 g (Keck 1994) snakes without detrimental effects. ...
... and recapture probability (c ± SE) as 0.02 ± 0.01 (95% CI = 0.01-0.03). Although these capture rates are low, they are not atypical when compared to mark-recapture studies of other snake species (e.g., Semlitsch and Moran 1984;Bauwens and Claus 2018). The estimate of abundance (N ± SE) was 27 ± 2 (95% CI = 26-39), which is reasonably precise and suggests that longer-term studies using this method would likely be capable of yielding robust estimates of survival and other vital rates. ...
... Significant body-size variation among populations has been observed for numerous snake species (e.g., Semlitsch and Moran 1984;Schwaner 1985;Plummer 1987;King 1989;Gregory andLarsen 1993, 1996;Madsen and Shine 1993;Tuttle and Gregory 2012), but explanations vary. For example, body size often increases with size and/or availability of prey (Schwaner 1985;Shine 1987;Madsen and Shine 1993;Boback 2003;Filippakopoulou et al. 2014). ...
... However, offspring size of T. elegans varies relatively little among our study sites (Farr and Gregory 1991). Geographic differences in the relationship between litter size and maternal size also have been observed in Red-bellied Snake (Storeria occipitomaculata; Semlitsch and Moran 1984;Brodie and Ducey 1989). In all of these studies, geographic variation in body size accounts for only a small fraction of the variation in litter size. ...
Life-history traits of organisms are influenced by both genetic and environmental factors. We used counts of offspring in captive-born litters to determine how geographic location, year-to-year variation, and body size of mother affected litter size of Western Gartersnake (Thamnophis elegans) in four widely separated populations in British Columbia. Litter size varied significantly among populations, but that variation was largely explained by differences in maternal body size among populations; that is, larger females had larger litters. With maternal size treated as a covariate, there was no further significant effect of location or of different years within sites on litter size. The overall regression, pooled over sites and years, between litter size and size of mother accounted for 55% of the total variation in litter size. Nonetheless, the significant variation in body size among locations calls for explanation and the consequent differences in litter size could be important demographically. Presumably, the large amount of unexplained residual variation reflects other differences, beyond body size, between individual mothers. Such differences among individuals might be determined by genetics or by environmental effects such as foraging success, but our data cannot address this question.
... Blanchard (1937) indicated that the low recapture rate might be due to the "wandering propensities" of the snake as well as unrestricted habitat and "hiding places." Semlitsch and Moran (1984) marked a total of 61 specimens at three locations in South Carolina with recapture percentages of 3% (1 of 34), 9% (1of 11), and 13% (2 of 16). Semlitsch and Moran (1984) interpreted their data as indicating large population size or rapid turnover. ...
... Semlitsch and Moran (1984) marked a total of 61 specimens at three locations in South Carolina with recapture percentages of 3% (1 of 34), 9% (1of 11), and 13% (2 of 16). Semlitsch and Moran (1984) interpreted their data as indicating large population size or rapid turnover. Gregory (1977) marked 22 in Manitoba, Canada but none was recaptured. ...
The examination of 387 preserved red-bellied snakes, Storeria occipitomaculata, from 18 museums and collections, literature records, and unpublished records revealed distributional records throughout much of Illinois, in contrast to earlier studies which found a more limited distribution. Seventy-one records of habitat types from museum records, field notes, and literature indicated that the species occupies woodlands but is not primarily forest adapted. It also inhabits prairie and prairielike habitats in Illinois. The common occurrence of this species in this type of habitat has not heretofore been reported elsewhere in the range of the snake. Our findings do not support an older zoogeographic theory that assumed the snake was nonadapted for prairie and thus excluded from the Prairie Peninsula. We propose that the species was able to occupy the area near the ice rim of the Wisconsin Episode glaciation, and followed the glaciation as it retreated because of the snake’s cold tolerance, ability to inhabit northern prairies and coniferous forests, vivipary which allows thermoregulation by gravid females, and the relatively temperate climate along the glacial rim. Within recent times, it seems likely that the snake was extirpated throughout much of the former prairie by destructive changes associated with agriculture.
... Despite the large sample size, the regularity of the sampling, and the narrowness of some of the study areas, a small number of recaptures were obtained compared to other long-term studies on other snake species (Hasegawa and Mori, 2008;Stevenson et al., 2009;Bayrakci and Ayaz, 2022). Further investigations are needed to confirm this observed pattern, which may be due to a large population size, high mortality, secretive behaviour, and rapid turnover (Semlitsch and Moran, 1984;Baron et al., 2010;Govindarajulu et al., 2011). ...
Here are the first data on the growth of the Javelin sand boa, Eryx jaculus, based on a capture-marking-recapture program
... Though several publications indicate that Storeria occipitomaculata occurrence is associated with woodland and woodland edge habitat (Ford et al. 1991;Pisani and Busby 2011;Fogell 2010) some papers from the northern and western Great Plains on the periphery of the species' range suggest it principally uses mesic herbaceous habitats such as wet meadows (Cahoe and Troelstrup 2004;Brown and Phillips 2013;Cairns et al. 2018). Broadly speaking, the literature clearly links S. occipitomaculata occurrence to the presence of wetland features regardless of habitat structure (woody vs. herbaceous), which may be related to their dependence on wetland associated gastropods as a primary food source (Semlitsch and Moran 1984;Brown and Phillips 2013;Dieter and Ronningen 2017). Ultimately, it is possible that the perceived association between woodland and S. occipitomaculata occurrence is relatively spurious as trees (e.g., Plains Cottonwood -Populus deltoides ssp. ...
The Red-bellied Snake (Storeria occipitomaculata) can be found throughout much of eastern North America, though two notable disjunct populations exist in the Black Hills of southwestern South Dakota and the Central Platte River Valley in southcentral Nebraska, west of the species’ core range. While literature continues to be added on the Red-bellied Snake and its natural history, it remains largely understudied in Nebraska. Throughout much of this species’ range, it is considered associated with woodland and wetland habitat features. On 28 September 2021, we detected one Red-bellied Snake near a treeless playa wetland in the Rainwater Basins ecoregion of southcentral Nebraska. Using a Grubbs Test to determine significant outliers, we found that this record was further from the Platte River than other previous accounts of this species in the state. This observation suggests this species may be found in other portions of the Rainwater Basins and considerably further from the Platte River than previously believed. Our observation along with other recent work indicates that Red-bellied Snakes may persist in herbaceous habitats lacking established woodland that include sufficient wetland features to support their primary food sources, including gastropods and other soft-bodied invertebrates. Due to the fragmentation of suitable habitats in the Rainwater Basins, coupled with the low dispersal of Red-bellied Snakes, populations persisting in the region are likely to be isolated.
<https://journals.ku.edu/reptilesandamphibians/article/view/18216>
... Passive sampling included drift fence, pitfall, and double-ended funnels established within a 10m X 10m quadrat at three sub-sites located 100m apart in the form of a triangle, that is, each site had three of these passive trapping arrays. Four drift fences each of length 7.6m (Cassani et al., 2015) and height 91cm were installed in an "X" shape (Enge, 1997;Ryan, Philippi, Leiden, Dorcas, & Wigley, 2002;Semlitsch & Moran, 1984) with 4 pitfall traps (made from 20L of bucket, Greenberg, Neary, & Harris, 1994) buried at each corner of the "X" and one at the centre of the trapping unit, making a total of 5 pitfall traps for each passive sampling unit. We established 8 double-ended funnels at each trap station, one on either side of each drift fence. ...
Agricultural intensification and the associated factors, including land transformation, are among the major global threats affecting biodiversity especially herpetofauna. However, little information is available about how different factors shape herpeto-fauna species assemblages in agricultural landscape at different spatial scales from patch (125-250m) to the landscape (500-1000m). We assessed the diversity of amphibians and reptiles in areas under low and high degrees of agricultural intensi-fication and explored different factors regulating diversity at different spatial scales using four sampling methods. Diversity and abundance of amphibians varied significantly between the two zones, but not for reptiles. Agricultural intensification index (AII), calculated based on agrochemical use and area under agriculture at 250m scale, seemed to affect amphibians both at patch as well as at 500m and 1000m landscape scales. The AII influenced reptilian diversity only at patch and 500m scales. Vicinity of natural forest had a stronger influence on reptilian abundance. Seminatural vegetation impacted herpetofauna diversities at larger spatial scales. The extent of water bodies influenced the reptilian abundance at 250m patch scale and amphibian abundance both at 250m and 1000m scale. Fallow lands affected only reptilian diversity at all spatial scales. Plantation affected amphibian at all scales but reptiles only at the landscape scale. Habitat heterogeneity regulated only amphibian diversity. These results highlight the fact that different patch and landscape-scale factors regulate the diversity of reptiles and amphibians differentially. Such scale-specific information will crucially inform future conservation action for the herpetofauna in the agricultural landscape. K E Y W O R D S agricultural intensification, amphibian, habitat heterogeneity, land-use elements, multiple spatial scale, reptiles
... Sexual dimorphism in SVL of our sample was similar to that of most locations, whereby male:female mean SVL was generally less than 0.90 (Meshaka, 2010). Exceptionally, M:F SVL ratio in populations in Michigan (Blanchard, 1937) and South Carolina (Semlitsch and Moran, 1984) scored 0.96. The length of its activity season in West Virginia was long, in keeping with shorter seasons among northern populations (Meshaka and Klippel, 2011). ...
Museum specimens of five species of fossorial snakes collected in West Virginia during 1930–2000 were examined to determine monthly incidence of capture, adult body sizes, reproductive cycle, and clutch characteristics. Captures occurred over the shortest time in the year in the Eastern Earthsnake (Virginia valeriae valeriae) and Northern Red-bellied Snake (Storeria occipitomaculata occipitomaculata) and were longest in the Northern Brownsnake (S. dekayi dekayi). Male gonadal cycle conformed to the temperate pattern, whereas that of females tended towards a tropical pattern. Incidence of females nearing oviposition or parturition was highest during June–July for all species, and length of their reproductive seasons were generally in keeping with those of northerly populations of the respective species. Mean clutch sizes were largest in the Northern Brownsnake (mean = 20.5) and smallest in the single oviparous snake, the Eastern Wormsnake (mean = 2.8). Adult body sizes were similar to respective populations elsewhere within their ranges. The Mountain Earth Snake (V. pulchra) was the least represented species in this study. A meaningful degree of predictability existed in the life history traits examined in our study as they related to geographic trends of this Allegheny snake assemblage.
... Other authors such as Kiesow (2006), Collins et al. (2010), LeClere (2013), and Moriarty and Hall (2014) have suggested spring and/or fall copulation for S. occipitomaculata, but none provide details on copulation from the region. Temperature has been shown to trigger activity in S. occipitomaculata (Semlitsch and Moran 1984) and likely influences emergence from winter dormancy and reproductive behaviors like many other North American snakes (Duvall et al. 1982, Gregory 1982. Further, the ability for female S. occipitomaculata to store sperm (Trapido 1940) makes determining the exact reproductive timing for this species difficult, which highlights the importance of direct observations. ...
Published in The Prairie Naturalist.
... Studies of aquatic snakes have emphasized the importance of investigating onto- genetic variation in habitat use before making generalizations (Lacy 1995, Savitzky andBurghardt 2000). Habitat use of aquatic juvenile snakes often is difficult to observe, however, because of capture biases (Rodda et al. 2007, Semlitsch and Moran 1984, Todd et al. 2007, Willson et al. 2008) and the size constraints of radio transmitters (Pattishall and Cundall 2008, Roth and Greene 2006, Tiebout and Cary 1987. Recently, researchers have examined juvenile pitviper ecology using advancements in transmitter technology (Cobb et al. 2005, Jellen andKowalski 2007), yet this type of work still is constrained by basic logistics of snake and transmitter size. ...
Understanding intraspecific variation in habitat use is important for the management of any species. In many studies of reptiles, habitat use by juveniles is poorly understood when compared to their adult conspecifics because of capture biases and logistical constraints. We compared habitat use between sexes and age classes of Common
Watersnakes (Nerodia sipedon) at a reservoir in central Illinois. Juvenile N. sipedon occurred more frequently in habitat with high canopy cover, whereas adult N. sipedon, especially reproductive females, were found exclusively in habitat with no canopy cover. Adult males used both locations equally. We emphasize the need to investigate ontogenetic variation in habitat use to better understand how reptiles utilize diverse anthropogenically altered landscapes.
... in the southeastern United States, six species of small snakes had the highest relative abundance in areas of intermediate canopy cover and intermediate litter depth relative to areas of high canopy cover with deep litter, or clearcuts with no canopy cover and very little litter (todd and andrews 2008). one of these species, the Northern redbelly Snake (Storeria occiptomaculata), is found in similar habitats to those used by the Northwestern Gartersnake and also eats slugs and earthworms (Gilhen 1984;Semlitsch and moran 1984), although, unlike Northwestern Gartersnakes, Northern redbelly Snakes are active both day and night, rather than just diurnally (P.t.G., unpublished data). also, grasssnakes in agricultural areas in Switzerland were found at sites with lower proportions of organic litter (Wisler et al. 2008). ...
Understanding habitat requirements of species is fundamental for their conservation and urban parks can provide key habitat for species in otherwise disturbed settings. Northwestern Gartersnakes (Thamnophis ordinoides) are common in parks in Saanich, British Columbia, but their specific habitat requirements are poorly understood. Based on previous studies and thermoregulatory needs of snakes, we predicted that edges, particularly field margins, would be heavily used by active snakes. We therefore used surveys that focused on edges to find snakes and measured edge-habitat use by comparing habitat variables at locations where snakes were found to the same variables at nearby random locations. Habitat variables included composition and structure of vegetation, substrate temperature, aspect, and slope. Overall, litter depth, canopy cover, a lack of bare ground and woody vegetation were the most important habitat variables for determining where snakes were found. our results provide a preliminary assessment to improve our understanding of habitat use for this species. The abundance of snakes found while surveying edges supports our initial assumption that edges are important habitat features but more work is required using multiple survey methods to further test this hypothesis.
... Although ecological data are available for two populations of C. schneiderii (Jayne et al., 1988; Karns et al., 2002), there exist gaps in our knowledge on population structure (e.g., size structure). Life history traits tend to vary between populations of snakes (Voris & Jayne, 1979; Semlitsch & Moran, 1984; Seigel, 1992; Manjarrez, 1998; Blouin-Demers et al., 2002; Karns et al., 2005), and comparative studies of C. schneiderii populations in its range can provide a better understanding on how the species adapts to different environments (Parker & Plummer, 1987). ...
Ecological traits of a relatively sheltered population of the dog-faced water snake, Cerberus schneiderii, were determined or estimated using mark-recapture data. Monthly surveys were conducted at the man-made brackish ponds at Sungei Buloh Wetland Reserve, Singapore throughout the year 2006. Estimates of population density (102 snakes ha –1), snake biomass (4.1 kg ha –1) and relative abundance (5.4 snakes man-hour –1) provided evidence of a large population. Sex ratio was almost 1:1. Snakes from a wide range (145–720 mm SVL) of body size were present. Even though neonates were rarely encountered, 88.7% of adult females have reached the size of sexual maturity (SVL = 336 mm SVL). There was no seasonal variation in the population's size structure, suggesting that recruitment occurred throughout the year. Most of the snakes were sedentary and more than 90% of them remained in the same pond that they were captured for the fi rst time. During low tides, snakes had a tendency of congregating at the relatively deep waters close to the sluice gates and in the network of tidal streams and pools in the man-made ponds. The population exhibited sexual dimorphism, in terms of males having relatively longer tails and females possessing relatively wider heads.
... Geographic variation in snake reproductive traits does exist (Fitch,985), but seasonal and annual variation in reproductive raits within and between populations of a species are less well documented. Some species, such as Storeria occipitomaculata, show little latitudinal population variation in emale reproductive traits between Michigan and South Carolina (Semlitsch and Moran, 1984), whereas Fitch 1985) found that 60% of 25 snake species in the United States showed a northward increase in clutch/litter size. ...
... Of the 52 snake species found in the southeastern United States, perhaps the most abundant but least studied are small, fossorial " litter snakes, " including the genera Carphophis, Diadophis, Rhadinaea, Storeria , Tantilla, and Virginia (Willson and Dorcas 2004). Because litter snakes are unsuitable for radio-telemetry and because their secretive habits lead to few recaptures (Semlitsch and Moran 1984;, in press; Willson and Dorcas 2004 ), the ecology and population biology of some species remains unknown, particularly in the Southeast. Virginia striatula (Linnaeus) (Rough Earth Snake) and Virginia valeriae Baird and Girard (Smooth Earth Snake), are diminutive, natricine snakes which, despite their extensive geographic ranges in the Southeast, are infrequently encountered. ...
Relatively little is known about the ecology and population biology of Virginia striatula (Rough Earth Snake) and Virginia valeriae (Smooth Earth Snake), especially in the southeastern portion of their geographic ranges. We studied popula-tions of the two species on the Savannah River Site (SRS) in Aiken, SC from 1971 to 2007. We found sexual size dimorphism in both species, in which females were longer and heavier than males, but had relatively shorter tails. Overall, Rough Earth Snakes were longer and heavier than Smooth Earth Snakes, but maximum sizes of both species were smaller on the SRS than at other localities from which data are reported. Additionally, all gravid female Smooth Earth Snakes that we captured on the SRS were smaller than their reported size at sexual maturity from other parts of their range. Seasonal activity of Smooth Earth Snakes peaked in May and October, but both Smooth Earth Snakes and Rough Earth Snakes were frequently captured during all warm months. Distinct age classes in the two species were not readily ap-parent other than several neonates that we captured. We strongly encourage future studies to determine growth rates, longevity, and minimum size at sexual maturity of earth snakes in the Southeast.
... Two patterns of yolk deposition have been described in temperate zone squamates (Aldridge, 1979;Yokoyama and Yoshida, 1994): type I, in which vitellogenesis is initiated and completed wholly after spring emergence prior to ovulation as occurs in some snakes (Aldridge, 1979;Whittier et al., 1987;Yokoyama and Yoshida, 1994); and type II vitellogenesis, which begins in late summer or autumn following parturition and is completed the following spring (Aldridge, 1979;Yokoyama and Yoshida, 1994). The latter pattern has been described in several lizards (Flemming, 1993c;Van Wyk, 1994; Cree and G 1 Ovulation usually occurs in spring (Xavier, 1982;Semlitsch and Moran, 1984;Taylor, 1985;Naulleau and Fleury, 1990;Shine et al., 1996a), presumably to allow gestation to begin as early as possible once thermal conditions become favourable in a potentially limited active season. Females are usually pregnant during the warmer part of the active season, as the length of gestation is largely determined by temperature (Beuchat, 1986;Shine and Harlow, 1993;Mathies and Andrews, 1995;Castilla and Swallow, 1996). ...
... The exclusion of these terrestrial areas from protection under wetland statutes would most likely reduce recruitment of juveniles into the breeding adult population, reduce adult survival, and therefore reduce the potential of the population to persist (Semlitsch et al. 1996 ). The widespread use of adjacent terrestrial habitats by other amphibians and semiaquatic species for various parts of their life cycle further underscores their importance (Dole 1965aDole , 1965b Gill 1978; Bennett et al. 1980; Semlitsch & Moran 1980; Semlitsch et al. 1988; Berven & Grudzien 1990; Buhlmann et al. 1993; Burke & Gibbons 1995; Reese 1996) and suggests that these are critical habitats in need of protection. Although there is variation in the size of terrestrial habitats used by salamander species, presumably related to life-history requirements, geographic variation in climate and habitat, or even among particular ponds because of topography, vegetation, and wetland size, a buffer zone cannot realistically be determined for each wetland and species. ...
Many semi‐aquatic organisms, such as salamanders, depend on both aquatic and terrestrial habitats to complete their life cycle and maintain viable populations. But current U.S. federal and state regulations protect only the wetland itself or arbitrarily defined portions of terrestrial habitat, if any. Part of the reason terrestrial habitats adjacent to wetlands are not protected is the lack of a clear understanding of the distances from shorelines that are biologically relevant to wetland fauna. Such information is critical for delineation of terrestrial “buffer zones” for wetlands, and thus for the conservation of semi‐aquatic organisms. I summarized data from the literature on terrestrial habitat use by one group of pond‐breeding salamanders, especially distances individuals traveled away from ponds. The results provide a basis for setting terrestrial buffer zones determined from actual habitat use by adult and juvenile salamanders. The mean distance salamanders were found from the edge of aquatic habitats was 125.3 m for adults of six species and 69.6 m for juveniles of two of these species. Assuming that the mean distance encompasses 50% of the population, a buffer zone encompassing 95% of the population would extend 164.3 m (534 ft) from a wetland’s edge into the terrestrial habitat. Data from other amphibians suggest that this buffer zone is applicable to a range of species, but caution should be taken for taxa suspected to be more vagile. Wetland managers and policymakers must recognize the special needs of semi‐aquatic organisms during their entire life cycle, not just during the breeding season. To maintain viable populations and communities of salamanders, attention must be directed to the terrestrial areas peripheral to all wetlands. Data on habitat use from salamanders and other semi‐aquatic species make it increasingly apparent that maintaining the connection between wetlands and terrestrial habitats will be necessary to preserve the remaining biodiversity of our vanishing wetlands.
Delineación Biológica de Zonas Terrestres de Amortiguamiento para Salamandras con Reproducción en Charcas
Muchos organismos semi‐acuáticos, como son las salamandras, dependen tanto de hábitats acuáticos como terrestres para completar su ciclo de vida y mantener poblaciones viables. Sin embargo, las actuales regulaciones federales y estatales en los Estados Unidos protegen unicamente a los humedales o a porciones de hábitat terrestres (de ser posible). Parte de las razones por las cuales los hábitates terrestres adyacentes a humedales no son protegidos se debe a la carencia de un claro entendimiento de las distancias biológicamente relevantes partiendo de los bordes y que son utilizados por la fuana del humedal. Esta información es crítica para delinear zonas terrestres de “amortiguamiento” para humedales, y en consecuencia para la conservación de organismos semi‐acuáticos. Resumo datos de la literatura sobre el uso de hábitat terrestre por un grupo de salamandras con reproducción en charcas, especialmente de distancias individuales viajadas hacia afuera de las charcas. Los resultados proveen las bases para establecer zonas terrestres de amortiguamiento determinadas a partir del uso actual del hábitat por salamandras adultas y juveniles. La distancia media a partir del borde de los hábitats acuáticos en la cual las salamandras fueron encontradas fue de 125.3 m para adultos de seis especies y de 69.6 m para juveniles de dos de estas especies. Asumiendo que la distancia media abarca un 50% de la población, una zona de amortiguamiento que abarque 95% de la población podría extenderse hasta los 164.3 m (534 pies) partiendo del borde del humedal hacia el hábitat terrestre. Datos de ostros anfibios sugieren que esta zona de amortiguamiento es aplicable para un rango de especies, pero se deben tomar precauciones para taxes de los que se sospecha se desplazan mas. Manejadores de humedales y estructuradores de políticas deben reconocer las necesidades especiales de organismos semi‐acuáticos a lo largo de su ciclo de vida completo, no solo durante la temporada de reproducción. Se debe dirijir especial atención a las áreas terrestres periféricas a todos los humedales para mantener poblaciones viables y comunidades de salamandras. Datos de uso del hábitat por salamandras y otras especies semi‐acuáticas hacen mas aparente la necesidad de mantener la conección entre humedales y hábitats terrestres para conservar la biodiversidad que aún queda en nuestros humedales en desaparición.
... Earthworms seem to be the principal dietary item for all five species, and they all probably eat other invertebrates, but more complete diet studies are needed (Ernst and Ernst 2003). Population densities of these small snakes in longleaf pine savannas seem to be relatively sparse in the brown snake (Clark 1949;Ford et al. 1991;Dalrymple et al. 1991) and red-bellied snake (Semlitsch and Moran 1984;Ford et al. 1991); not especially dense in the smooth earth snake (Ernst and Ernst 2003); locally abundant in both the southeastern crowned snake (Neill 1951a;Brode and Allison 1958;Semlitsch et al. 1981) and Florida crowned snake (Campbell and Christman 1982;Mushinsky 1984); and unstudied and poorly known in the rough earth snake (Ernst and Ernst 2003). ...
In the southeastern U.S. Coastal Plain, all landscapes can be conceptually divided into aquatic, wetland, and upland habitats.
Aquatic and wetland habitats account for a substantial percentage of the Coastal Plain, especially near the coast and in Louisiana
and Florida, but overall from southeastern Virginia to east Texas, uplands constitute the largest proportion of the terrain.
It has been estimated that, upon the arrival of Europeans and Africans in North America, upland ecosystems dominated by a
single tree species, longleaf pine (Pinus palustris), accounted for about 60% of the Coastal Plain landscape (Ware et al. 1993). In other words, longleaf pine ecosystems were
the principal ecosystems in a belt of land stretching about 2000 miles along the southeastern margin of the North American
continent. Most of the range of longleaf pine was in the Coastal Plain, a gently undulating, lowelevation (0–200 m), sedimentary
landform with soils developed from sandy clays (clayhills and some flatwoods) or pure sand (sandhills and flatwoods), sometimes
underlain by limestone (Brown et al. 1990; Martin and Boyce 1993). Longleaf pine ecosystems and their vertebrate faunas are
the focus of this chapter.
... brown [Storeria dekayi] and redbelly [S. occipitomaculata]) are typically <1.5 ha (Freedman and Catling, 1979;Semlitsch and Moran, 1984), so we considered patches <1.5 ha to be small. Those between 1.5 and 10 ha made up the intermediatesize class. ...
We studied occupancy, species richness, abundance, and size distributions of snakes on habitat patches that ranged from 0.2 to 120 ha within a landscape undergoing substantial land-use changes. Additionally, we examined the role of intraguild predation in structuring snake communities by equipping five racers (Coluber constrictor, the largest snake in our study area) with transmitters, and then compared the abundance of smaller snakes within areas of intensive (75% isopleth home range) and limited activity (outside of 75% isopleth) by racers. As expected, small patches (<1.5 ha) often were vacant or occupied by only one species (garter snakes, Thamnophis sirtalis). Species richness was greatest on large patches, and snakes also tended to be more abundant on large patches. Counter to our expectations, the proportion of large-bodied individuals on small patches was greater. The distribution of small-bodied snakes on one large patch may have been affected by racers because the proportion of small snakes was less in areas intensively used by racers. Additionally, the abundance of the most generalist species in our study (garter snakes) was less in areas of intensive use by racers. In the northeastern United States, populations from a variety of taxonomic groups (including insects, migratory songbirds, mammals, and snakes) are rapidly declining in response to the loss of early-successional habitats. Our study lends support to current initiatives that recommend restoration and maintenance of parcels of early-successional habitats to sustain regional biological diversity.
With its temperate climate and variety of habitats, Michigan supports a diverse array of animals and plants, including fifty-four species of amphibians and reptiles. The dispersal and biology of the Michigan herpetofauna-amphibians and reptiles-is even more unique because Michigan consists of two peninsulas that project into large freshwater seas and also because it was completely covered by a massive ice sheet a relatively short time ago. In The Amphibians and Reptiles of Michigan: A Quaternary and Recent Faunal Adventure, author J. Alan Holman explores the state's amphibians and reptiles in detail and with many helpful illustrations, making this the only volume of its kind available. Holman uniquely bridges the gap between neo- and paleoherpetology and shows that Michigan's modern herpetofaunas reflect Pleistocene (ice age) and Holocene (warm period after the ice age) events, as the entire modern population was forced to re-invade the state after the last withdrawal of ice. In Part 1, Holman discusses Michigan as an amphibian and reptile habitat, including a geological, climatic, and vegetational history. Part 2 presents recent species accounts, covering all fifty-four species of amphibians and reptiles, along with their general distribution, Michigan distribution (with range maps), geographic variation, habitat and habits, reproduction and growth, diet, predation and defense, interaction with humans, behavioral characteristics, population health, and general remarks. In Part 3, Holman examines the Michigan herpetofauna in Quaternary and recent historical times and the species accounts include Pleistocene, Holocene, and archaeological records. Color photographs of major herpetological habitats in Michigan are provided and color photographs of all modern species are included. Black-and-white illustrations depict both modern and ancient speicies. Herpetologists, paleontologists, zoologists, ecologists, and general biologists, as well as anyone who loves salamanders, frogs, turtles, and snakes will appreciate the comprehensive research presented in The Amphibians and Reptiles of Michigan.
ACKNOWLEDGMENTS Iwould like to thank my advisor, Dr. John Litvaitis, for his help, encouragement, patience, and trips to Young’s Restaurant. Many thanks also to my thesis committee, Dr. Kim Babbitt, Dr. Chris Neefus, and Dr. Jim Taylor, for their advice. Thanks to the ,following people and entities for help in and ,contributions to various aspects of my research: Toby Currier and Brian Gilbert (field assistance), Dr. John Means and assistants (transmitter implantation), NH Fish and Game Department, UNH Center for International Studies (conference funding), UNH Department of Natural Resources (conference funding), UNH Department of Natural Resources Office Staff, UNH
In 1837 a young Charles Darwin took his notebook, wrote “I think”, and then sketched a rudimentary, stick-like tree. Each branch of Darwin’s tree of life told a story of survival and adaptation – adaptation of animals and plants not just to the environment but also to life with other living things. However, more than 150 years since Darwin published his singular idea of natural selection, the science of ecology has yet to account for how contrasting evolutionary outcomes affect the ability of organisms to coexist in communities and to regulate ecosystem functioning.
In this book Philip Grime and Simon Pierce explain how evidence from across the world is revealing that, beneath the wealth of apparently limitless and bewildering variation in detailed structure and functioning, the essential biology of all organisms is subject to the same set of basic interacting constraints on life-history and physiology. The inescapable resulting predicament during the evolution of every species is that, according to habitat, each must adopt a predictable compromise with regard to how they use the resources at their disposal in order to survive. The compromise involves the investment of resources in either the effort to acquire more resources, the tolerance of factors that reduce metabolic performance, or reproduction. This three-way trade-off is the irreducible core of the universal adaptive strategy theory which Grime and Pierce use to investigate how two environmental filters selecting, respectively, for convergence and divergence in organism function determine the identity of organisms in communities, and ultimately how different evolutionary strategies affect the functioning of ecosystems. This book reflects an historic phase in which evolutionary processes are finally moving centre stage in the effort to unify ecological theory, and animal, plant and microbial ecology have begun to find a common theoretical framework.
Using field observations and laboratory experiments we examined the role of temperature in microhabitat selection by an eastern Ontario population of northern water snakes (Nerodia sipedon). From 1349 random transects through a marsh we found that basking activity peaked at 09:00 and then declined steadily until 14:00 before increasing again. Our ability to detect snakes depended upon the microhabitat they occupied, and to the time of day when the snakes were encountered in water. In the field, temperatures of basking snakes averaged (±SE) 26.3 ± 0.7 °C (n = 36), while captive snakes in a thermal gradient showed a narrower selectivity, averaging 27.7 ± 0.4 °C (n = 21). The temperatures of basking snakes never exceeded 33 °C, even though a model snake placed in the sun reached 48 °C, suggesting that the snakes were thermoregulating to prevent overheating. In both the field and enclosures, water snakes basked more frequently as the temperature of the air increased relative to the water. Experimental manipulation of water temperature relative to air temperature revealed that temperature influenced microhabitat selection independently of circadian patterns. Finally, when in water, snakes tended to frequent habitats where leopard frogs (Rana pipiens), a common prey species, were most abundant, suggesting that prey distribution may also be an important component of water snake habitat selection.
Little is known about many aspects of the ecology of the Desert Nightsnake (Hypsiglena chlorophaea). I studied the ecology of H. chlorophaea from 121 specimens collected May to October 2004 and 2005 in central Washington State. In this region, males ranged in size from 184–382 mm SVL (283.7 ± 5.8 mm, N = 49), whereas females were 158–532 mm SVL (335.5 ± 69.4 mm, N = 58). Body mass of males was 2.6–22.1 g (10.2 ± 5.04 mm) and females 2.3–53.9 g (15.1 ± 9.49 mm). In Washington, H. chlorophaea feeds on a wide variety of prey such as scincid and anguid lizards, thamnophiine snakes, anurans, and the eggs of other squamate reptiles. In addition, I report the first mammalian prey item taken by H. chlorophaea. The reproductive ecology differs little from other parts of the range of H. chlorophaea. Males (N = 22) with enlarged testes were found from mid-May through late August. Females (N = 17) with enlarged follicles and ova were found from May through June, with recent hatchlings collected during mid-August. Based upon these data, in Washington, H. chlorophaea has a more varied diet compared to southern populations but shows a similar preference for lizards. With regard to reproductive patterns, Washington populations of H. chlorophaea differ very little from other populations.
Male snakes typically have longer tails relative to body length than females, but the extent of this dimorphism varies among species. Three hypotheses have been suggested to explain tail dimorphism. The Morphological Constraint Hypothesis proposes that males have relatively longer tails to accommodate hemipenes and retractor muscles. The Female Reproductive Output Hypothesis proposes that females have relatively shorter tails as a secondary result of natural selection for increased reproductive capacity. The Male Mating Ability Hypothesis proposes that sexual selection favours relatively longer tails in males during courtship. These hypotheses make different predictions about the relationships among tail length, body size, male reproductive morphology, female reproductive output, mode of reproduction, and male mating behaviour among and within taxa. Predictions were tested using published data for 56 genera in the family Colubridae and original data for the water snake, Nerodia sipedon. Tail length dimorphism was more male-biased in tam having relatively short tails (r=–0.52, P < 0.001), hemipenes and retractor muscles occupied a greater proportion of the tail in taxa having relatively short tails (r=– 0.71, P < 0.00l and r=– 0.66, P = 0.001, respectively), and tail length dimorphism was more male-biased in taxa in which body size dimorphism was more female-biased (r=– 0.60, P < 0.001). These results support both the Morphological Constraint Hypotheses and the Female Reproductive Output Hypothesis. However, tests of other predictions, including those regarding patterns within N. sipedon, failed to support any of the three hypotheses. Comparisons among taxa suggest several species in which further tests of these hypotheses would be especially appropriate.
This study examines Chinese immigrant parents' perceptions of filial piety. The concept of filial piety is introduced and we discuss the impacts of modernization and immigration experience on the challenges faced by contemporary Chinese immigrants as they reconcile traditional values with the demands of sociohistorical change and child rearing in the United States. Factor analysis of a commonly applied scale demonstrates multiple aspects of filial piety and reflects modifications from traditional views. Interview results point to aspects of filial piety not fully represented in the quantitative scale and expose specific challenges in child rearing related to filial values. These findings suggest the evolution of expectations and strategies related to a cultural adaptation of filial piety. One key demand is for strategies consistent with parental values while maintaining respect for children's unique point of view. The conclusions focus on the development of approaches to understanding the evolving conceptualization and meaning of filial piety for contemporary immigrant Chinese.
Snake populations in the North American tallgrass prairie appear to be declining, yet data unavailability impedes the development of enhanced ecological understanding of snake species-habitat relationships and also hinders snake conservation efforts. This study addresses both issues for the snakes of Illinois in two steps. In a two-year mark-recapture study at twenty-two sites within six northern Illinois prairie preserves, I investigated snake species-habitat relationships using habitat variables at three scales: microhabitat (< 100 m), landscape (1 - 10 km), and regional (> 10 km). A total of 120 snakes representing seven species was captured using drift fence arrays associated with funnel traps and sheet metal cover. The low numbers and diversity of snakes captured, when compared to historic evidence, indicate that Illinois snake populations have declined. At the microhabitat scale, non-metric multidimensional scaling and Mantel tests revealed a relationship between snake species composition and elevation. At the landscape-scale, snake species composition varied along an agricultural-urban cover gradient. Classification and regression trees and maximum entropy models (Maxent) were used to identify the scales at which snake species-habitat relationships were strongest. Six of seven regression trees for individual snakes species contained habitat variables at the landscape scale. Important landscape characteristics included patch size, isolation, and land cover, metrics that strongly covary with habitat loss. Microhabitat features only appeared in the regression trees of two species and in three Maxent models. This study indicates that habitat loss has shaped the current distribution of snake species in Illinois's remnant prairies and that snake conservation efforts should emphasize the landscape-scale. Finally, I developed a risk ranking system based on natural and life history characteristics to assess the conservation status of Illinois's 38 snake species. Cluster analysis identified eight groups of snakes, similar in terms of risk factors, with high risk species sharing characteristics such as large body size, long life span, limited habitat breadth, and a high anthropogenic threat ranking. Here, I emphasize the need for basic demographic studies on snakes and suggest that ranking systems be used with population data (when available) and expert opinion to identify snake species of conservation concern in other regions. Dissertation
Snakes of both sexes display remarkable flexibility and diversity in their reproductive tactics. Many features of reproduction in female snakes (such as reproductive mode and frequency, seasonality and multiple mating) allow flexible maternal control. For example, females can manipulate not only the genotypes of their offspring (through mate choice or enhanced sperm competition) but also the phenotypes of their offspring (through allocation 'decisions', behavioural and physiological thermoregulation, and nest-site selection). Reliance on stored energy ('capital') to fuel breeding results in low frequencies of female reproduction and, in extreme cases, semelparity. A sophisticated vomeronasal system not only allows male snakes to locate reproductive females by following scent trails, but also facilitates pheromonally mediated mate choice by males. Male-male rivalry takes diverse forms, including female mimicry and mate guarding; combat bouts impose strong selection for large body size in males of some species. Intraspecific (geographical) variation and phenotypic plasticity in a wide array of reproductive traits (offspring size and number; reproductive frequency; incidence of multiple mating; male tactics such as mate guarding and combat; mate choice criteria) provide exceptional opportunities for future studies.
This paper reviews published literature on snakes to test the hypothesis that large male size, relative to female size, evolves because of the advantage it confers in male combat. Analysis of the data reveals a high correlation between the occurrence of male combat, and sexual dimorphism in which the male is the larger sex. This correlation holds (i) within the total sample of snake species (n=224), (ii) within the family Colubridae (n=134), and (iii) in a comparison between the eight families of snakes for which data are available. These results strongly support the hypothesis that large male size is an adaptation to intrasexual competition. The analysis also shows that females are larger than males in about 66% of snake species, that male combat is known in only about 15% of species, and that both sexual size dimorphism and the incidence of male combat tend to be distributed along taxonomic lines.
A method of measuring terrestrial activity in aquatic turtles is presented. The importance of this activity is indicated in considering some aspects of the population ecology of the species involved. Based on captures in terrestrial pitfall traps, up to 30% of the turtles inhabiting a Carolina bay in South Carolina traveled onto land during an eight-month period of study. This suggests that terrestrial activity may be very important in the population dynamics of aquatic turtles. The trapping method revealed a directional trend in emigrating individuals and a random movement by immigrants. Individuals of at least four species moved back and forth between contiguous aquatic areas. Terrestrial activity could not be correlated consistently with any single environmental factor. Initial activity in spring and cessation in autumn are presumably influenced by temperature. Rainfall apparently provoked terrestrial movement in autumn but not during other parts of the year.
The activity of the slugLimax maximus was studied in relation to weather. Three hundred-and-fifty-eight hourly observations of activity and weather were made on 21 nights from May until October, 1976. Factors causally important to molluscan activity were included in a step-down correlation-regression analysis of daily and seasonal behavior. The analysis was also performed using weather data from the previous hourly observation. Models using lag-weather did not explain as much variability as did concurrent weather.
The regression models explained about 73% to 87% of the observed variation in activity. The most important factors included in the regression models were time of day (circadian rhythm), light intensity, changes in light intensity and surface temperature. Shelter temperature, temperature gradients, length of the night, and time of sunset were also included in some models. Age and hydration were shown to be key factors in other experiments.
A model incorporating weather thresholds estimated from field data explained 83.06% of the variability in the activity ofL. maximus over the season. The values predicted from the model did not differ significantly from those actually observed in the field (Kolmogorov-Smirnov test, p>0.50).