Thamnophis Proximus Research Articles

Kiricephalus coarctatus (Pentastomida: Porocephalidae) from Orange-Striped Ribbonsnake, Thamnophis proximus proximus (Serpentes: Colubridae), from Arkansas, U.S.A., with a Summary of Ophidian Hosts of the Western Hemisphere

Two adult orange-striped ribbonsnakes, Thamnophis proximus proximus, were collected from northern Arkansas and examined for helminths. A single snake harbored 4 specimens of the pentastomid, Kiricephalus coarctatus. We document a new host as well as a new distributional record for the parasite. This is only the second time a species of pentastomid has been reported from the state in any host. A summary of ophidian hosts of K. coarctatus from the Western Hemisphere is included.

Spatiotemporal Patterns of Snake Captures and Activity in Upland Pine Forests

Patterns of species' occurrences across space and time are fundamental components to understanding their ecology, as this variation often reflects responses to local environmental gradients. We built species-specific models to understand the spatial and temporal factors predicting captures and activity of five snake species in upland pine forests: copperhead (Agkistrodon contortrix), racer (Coluber constrictor), coachwhip (Masticophis flagellum), western ratsnake (Pantherophis obsoletus), and western ribbonsnake (Thamnophis proximus). From mid-May to mid-July across 3 y (2018, 2019, 2020), we monitored boxtraps in two upland pine forests experiencing different management regimes: (1) subjected to frequent thinning and prescribed burning, and (2) subjected to infrequent thinning and prescribed burning. Significantly more copperheads and western ribbonsnakes were captured at the infrequently thinned and burned forest, whereas significantly more racers were captured at forest subjected to frequent thinning and burning. As the summer progressed, captures decreased each subsequent month for both racers and western ratsnakes, with the fewest captures in July. Western ratsnakes were the only species to exhibit a response to the weather in that activity decreased with increasing rainfall. No variables were significant predictors of coachwhip captures. The variation in captures across space may be attributed to the physiological tolerances of each species based on their habitat preferences or differences in prey availability at each forest. Interactions between the physiological tolerances, foraging behaviors, or their reproductive phenology may be underlying the temporal variation in activity patterns.

Abnormal coloration of a Western Ribbonsnake, Thamnophis proximus (Say 1823), from Sutton County, Texas, USA

Abnormal coloration of a Western Ribbonsnake, Thamnophis proximus (Say 1823), from Sutton County, Texas, USA

Ontogenetic prey size selection in snakes: predator size and functional limitations to handling minimum prey sizes

As body size increases, some predators eliminate small prey from their diet exhibiting an ontogenetic shift toward larger prey. In contrast, some predators show a telescoping pattern of prey size in which both large and small prey are consumed with increasing predator size. To explore a functional explanation for the two feeding patterns, I examined feeding effort as both handling time and number of upper jaw movements during ingestion of fish of consistent size. I used a range of body sizes from two snake species that exhibit ontogenetic shifts in prey size (Nerodia fasciata and N. rhombifer) and a species that exhibits telescoping prey size with increased body size (Thamnophis proximus). For the two Nerodia species, individuals with small or large heads exhibited greater difficulty in feeding effort compared to snakes of intermediate size. However, for T. proximus measures of feeding effort were negatively correlated with head length and snout–vent length (SVL). These data indicate that ontogenetic shifters of prey size develop trophic morphology large enough that feeding effort increases for disproportionately small prey. I also compared changes in body size among the two diet strategies for active foraging snake species using data gleaned from the literature to determine if increased change in body size and thereby feeding morphology is observable in snakes regardless of prey type or foraging habitat. Of the 30 species sampled from literature, snakes that exhibit ontogenetic shifts in prey size have a greater magnitude of change in SVL than species that have telescoping prey size patterns. Based upon the results of the two data sets above, I conclude that ontogenetic shifts away from small prey occur in snakes due, in part, to growth of body size and feeding structures beyond what is efficient for handling small prey.

NOCTURNAL ARBOREALITY IN SNAKES IN THE SWAMPLANDS OF THE ATCHAFALAYA BASIN OF SOUTH-CENTRAL LOUISIANA AND BIG THICKET NATIONAL PRESERVE OF SOUTHEAST TEXAS

The southeastern United States is home to a diverse assemblage of snakes, but only one species, the Rough Greensnake (Opheodrys aestivus), is considered specialized for a predominantly arboreal lifestyle. Other species, such as Ratsnakes (genus Pantherophis) and Ribbonsnakes/Gartersnakes (genus Thamnophis), are widely known to climb into vegetation and trees. Some explanations given for snake climbing behavior are foraging, thermoregulation, predator avoidance, and response to flood. Reports of arboreality in snake species typically not associated with life in the trees (such as terrestrial, aquatic, and even fossorial species) usually come from single observations, with no knowledge of prevalence of the behavior. Here, we report on arboreality of snake species detected during 8 years of night surveys in the Atchafalaya Basin of south-central Louisiana and 5+ years of night surveys in Big Thicket National Preserve in southeast Texas. We recorded a total of 1,088 detections of 19 snake species between the two study areas, with 348 detections above ground level (32%). The Rough Greensnake and Western Ribbonsnake (Thamnophis proximus) accounted for nearly 75% of total arboreal detections among the two study areas. However, with one exception, all snake species detected more than once between both study areas had at least one arboreal detection. These observations demonstrate that snakes with widely varying natural histories may be found in the trees at night, and for some species, this behavior may be more common than previously believed.

The influence of thermal biology on road mortality risk in snakes

Road mortality is a significant threat to terrestrial vertebrates in many areas, and the novel thermal environment of black-topped roads may represent ecological traps for some species and demographic groups. We investigated the relationship between ambient temperature and on-road detection in a snake assemblage in southeastern Louisiana by comparing observations of live snakes on a black-topped road, across measurements of air temperature and road temperature on survey days. Analyses indicated on-road detection of snakes was significantly influenced by ambient temperature conditions for five snake species. Additionally, road temperatures, and the difference between air and road temperatures, were strong drivers of on-road snake detections. Permutation analysis methods revealed that significant temperature related group (species or sex) structure exists in occurrences of snakes on the roadway, and that road temperature was the strongest driver of species differences. We also compared how air and road temperatures affected occurrence on the road between sexes in the colubrid snakes Nerodia fasciata, Nerodia cyclopion, Thamnophis proximus, and Pantherophis obsoletus. Males and females of the viviparous species N. fasciata, N. cyclopion, and T. proximus diverged significantly in temperature preferences, with females found under warmer conditions, while males and females of the oviparous species P. obsoletus did not. Road temperature was also the strongest driver of differences between sexes. Our results indicate that black-topped roads are an ecological trap that is heavily influenced by sex, reproductive condition, and species specific thermoregulatory requirements, particularly for viviparous species.

Feeding in natricines: relationships among feeding morphology, behavior, performance and preferred prey type

AbstractThe diversity of feeding mechanisms among predators reflects phenotypic modifications that may improve feeding performance on a preferred prey type. I compared trophic morphology, feeding performance (time and upper‐jaw walks) and behavior (initial bite and ingestion directions) among three species of natricine snakes that were fed fish and frogs over a broad range of relative prey sizes. Feeding behavior was influenced by prey type but did not differ among the snake species. Both bite and ingestion directions influenced the number of upper‐jaw movements (lateral excursions and protractions) required to consume fish, but only initial bite position significantly affected the number of upper‐jaw movements required to ingest frogs. Within snake species, feeding performance did not differ between fish and frogs for Nerodia fasciata and Nerodia rhombifer; however, Thamnophis proximus consumed fish with fewer upper‐jaw movements. Feeding time differed significantly among snake species when fed both fish and frogs. Trophic morphology did not significantly affect ingestion costs for fish but did influence ingestion when fed frogs. In general, differences in trophic morphology among the three species are not correlated to handling and ingestion performance.

Secondary Sex Ratios in Six Snake Species

Sex ratios at birth or hatching in snake populations are often assumed to be 1∶1 in agreement with Fisherian theory. We evaluated secondary sex ratios (SSRs) in two viperids (Sistrurus catenatus and S. miliarius) and four natricine colubrids (Nerodia rhombifer, Thamnophis proximus, T. radix, and T. sirtalis). We captured 274 gravid females that produced 2443 living offspring. Population-level SSRs in our focal species did not differ significantly from 1∶1. In addition, variation in individual litter SSRs conformed to expectations generated by the binomial distribution with an even sex ratio. Each species showed individual variation in SSRs; however, the majority of variation in litter SSRs was not explained by variation in the maternal or litter characteristics we examined. The three exceptions were a very strong negative association between mean offspring mass and litter SSR in T. radix (r2 = 0.96), a strong positive association between mean offspring mass and litter sex ratio in T. proximus (r2 = 0.40), and a strong positive association between maternal condition and litter SSR in T. proximus (r2 = 0.40). Whether or not these relationships have functional or adaptive significance warrants further study. The majority of our results were unsurprising and not statistically significant. We suggest, however, that the presentation and publication of both non-significant and significant results is exactly what is needed to give an accurate view of SSRs at both the population level and the maternal level in snakes.

Feeding performance in the Western Ribbon Snake (Thamnophis proximus): ontogeny and the effects of prey type and size

It has been suggested that juveniles have exaggerated morphologies or improved performance to compensate for the disadvantages of being small. As gape-limited predators, juvenile snakes are at a particular disadvantage in terms of prey availability, capture, and ingestion. Prey preference often changes with snake size yet previous studies generally compare only one prey type or relative prey size among age classes. Using Western Ribbon Snakes ( Thamnophis proximus (Say in James, 1823)), I investigated the ontogeny of head dimensions and feeding performance on frogs and fish using a range of relative prey sizes. Comparison among snake sizes indicated that smaller individuals had larger relative head sizes than larger conspecifics; however, larger individuals had larger heads. Initial bite position differed between juveniles and adults fed fish but not frogs. Both frogs and fish were generally consumed headfirst by adults and juveniles. Head length did not influence feeding performance in terms of time or pterygoid protractions for snakes fed either fish or frogs. In general, this study suggests that allometry of trophic morphology does not improve feeding performance.

Ontogenetic and sexual differences in diet in an actively foraging snake,Thamnophis proximus

Actively foraging species of snakes often consume large numbers of small prey, which creates a high meal to snake mass ratio. Because they may also rely on speed to avoid predation, this might negatively influence survival. We examined the diet of 313 western ribbon snakes ( Thamnophis proximus Say in James, 1823), a very attenuated species, in a floodplain in northeastern Texas. Of the 142 individuals with food, adult males ate 9 prey types, followed by females with 8, and juveniles only 6. The ontogenetic increase in prey diversity was predicted. However, female ribbon snakes are larger than males and their fewer prey types may reflect a strategy where smaller prey are dropped from the diet. Seasonal activity of prey and snake class was generally correlated. Overall individual prey sizes were comparably small. However, over 50% of the snakes contained multiple prey and total meal masses were similar to the maximum prey sizes of ambush foragers. Adults stopped feeding at proportionally lower meal mass to predator mass ratios than juveniles. The benefits of rapid growth for juveniles may outweigh predation risks associated with high prey consumption, but for adults of this species, consuming lighter meals may be the most stable strategy.

Prey Items of the Western Ribbon Snake, Thamnophis proximus

Western ribbon snakes (Thamnophis proximus) were collected at the Old Sabine Bottom Wildlife Management Area, Smith Co., Texas. Distended individuals were palpated to recover recently ingested prey, which resulted in discovery of five new prey items. This report also provides updated nomenclature of previously reported prey items. After comparing previously reported localities of prey items with current range descriptions and taxonomy, it was concluded that two anurans should be removed as documented prey items of T. proximus.

The Species-Abundance Distribution of Snakes in a Bottomland Hardwood Forest of the Southern United States

Species-abundance distributions often form a log series curve with a few common species and a large proportion of rare species. Niche apportionment and random processes such as dispersal and local extinction are reflected in the structuring of abundance ranks among species within a community. Bottomland hardwood forests of the southern United States have high biotic production because of flood pulses that bring in nutrients. The assemblage of snakes in these environments is diverse both in terms of diet and morphology. In this habitat, the high levels of some resources should be involved in the abundance ranks of the most common species, but other factors (e.g., body size) may be important in the abundance ranks of the less common species. We examined the abundances of snakes in a 2300-ha bottomland deciduous forest in northeastern Texas. Fourteen total species were recorded, but only in one year were all species collected. Three semiaquatic species, Thamnophis proximus, Nerodia erythrogaster, and Agkistrodon piscivorus were the most common. These three species eat fish and amphibians that are concentrated in ephemeral pools, but their foraging methods differ. Several other species had intermediate abundances and a wide variety of diets. Smaller and heavier species did not have lower abundances, and we suggest that, although poor dispersal ability may be involved in the rarity of some species, there are likely several factors involved. We hypothesize that both niche characteristics and random processes are involved in producing the stair-step appearance of the abundance ranks of these snakes.

Effects of flood suppression on natricine snake diet and prey overlap

Organisms may become adapted to disturbances when these disturbances occur periodically and at intermediate intensity. To investigate the effects of flood suppression, this study compared diet and competition of semi-aquatic snakes during flood (2000–2001) and no flood (2003–2005) years. Three natricine species, Nerodia erythrogaster (Forster in Bossu, 1771), Nerodia fasciata (L., 1766), and Thamnophis proximus (Say in James, 1823), were palpated for prey items in an east Texas floodplain under both conditions. Prey items were classified as crayfish, salamanders, anurans, or fish. Simpson’s diversity index of prey, frequency of consumed prey type, and prey importance values were compared between flood and no flood years. Pianka’s index of niche overlap was used to compare changes in diet overlap between species in the years with floods and those without. In the absence of floods, the number of prey types consumed by N. erythrogaster and T. proximus decreased. The frequency of prey types consumed during flood years was significantly different from the period of flood suppression for all three species. The order of prey importance also changed in the absence of floods for all three snake species. Without floods, diet overlap decreased between N. erythrogaster and the other two species; however, overlap between N. fasciata and T. proximus doubled.

Snake aggregation pheromones: Source and chemosensory mediation in western ribbon snakes (Thamnophis proximus).

Aggregation with conspecifics is a robust phenomenon among snakes that is mediated by chemical cues, although the source of such cues is unknown. Adult western ribbon snakes (Thamnophis proximus) discriminated between skin lipid extracts from conspecifics and those from a sympatric heterospecific snake, the corn snake (Elaphe guttata). Additionally, ribbon snakes were attracted to conspecific skin lipid-marked shelters when paired with control-marked shelters, but no preference was exhibited when shelters marked with E. guttata skin lipids were paired with control-marked shelters. Furthermore, prevention of chemical access to the vomeronasal organs of T. proximus eliminated the ability to respond to conspecific skin lipids. These results indicate that epidermal lipids are the source of chemical cues mediating attraction to shelters marked by conspecifics and that such signals are detected by the vomeronasal system.

Snake aggregation pheromones: Source and chemosensory mediation in western ribbon snakes (Thamnophis proximus).

Snake aggregation pheromones: Source and chemosensory mediation in western ribbon snakes (Thamnophis proximus).

The Eimeria (Apicomplexa: Eimeriidae) of Serpentes, with descriptions of three new species from colubrid snakes

Three new species of Coccidia (Apicomplexa: Eimeriidae) are described from snakes collected in Texas, U.S.A. Oocysts of Eimeria papillosum sp.nov. were found in Salvadora grahamiae lineata and are cylindrical, 32.0 × 18.0 (28.8–35.2 × 16.0–20.4) μm, with an outer wall studded by numerous papules. A micropyle and oocyst residuum are absent but a polar granule is present. Sporocysts are ellipsoid, possess a sporocyst residuum, and lack a Stieda body. Oocysts of Eimeria serpenticola sp.nov. were found in Thamnophis proximus rubrilineatus and are ellipsoid, 20.3 × 17.5 (18.4–22.4 × 15.8–19.8) μm, with a smooth, thin wall. A micropyle and oocyst residuum are absent but a polar granule is present. Sporocysts are elongate and possess a sporocyst residuum and Stieda body. Oocysts of Eimeria striatula sp.nov. were recovered from Virginia striatula and are spherical, 12.5 (11.2–15.2) μm, with a thin wall. A micropyle and oocyst residuum are absent but a polar granule is present. Sporocysts are elongate and possess a Stieda body and few granules within the sporocyst. A table is provided listing the more than 50 named species of eimerians reported to infect members of the suborder Serpentes.

Seasonality of Pheromone Trailing Behavior in Two Species of Garter Snake, Thamnophis (Colubridae)

Males of two species of garter snake (Thamnophis) were tested monthly, April- October, for their ability to follow trails laid by conspecific females in a 183 by 122 cm arena. Thamnophis sirtalis trailed best in April, May, and June; did not trail in late July; and showed intermediate trailing ability in August, September, and October. This variation in trailing activity reflects seasonal changes in the reproductive activity of this species. Thamnophis proximus males trailed females equally well throughout the entire season. As this species' reproductive habits are less known, it still is possible that the pheromone trail is involved primarily in reproduction.

New County Records of Amphibians and Reptiles in Kansas

New County Records of Amphibians and Reptiles in Kansas

Speciation with Little Genic and Morphological Differentiation in the Ribbon Snakes Thamnophis proximus and T. sauritus (Colubridae)

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The Rough Earth Snake (Virginia striatula): Ecology of a Texas Population

A 35 month mark-recapture study of an earth snake population was conducted in Brazos County, Texas. Monthly trapping success was positively correlated with cumulative rainfall for that month plus the two preceding months. Earth snakes fed entirely on earthworms. Home range area measured via implantation of radioactive tantalum tags was positively correlated with rainfall during the month prior to trailing. Estimates of mean home range size (up to 100 m2 for adult females) obtained with tantalum tags resembled other estimates based on markrecapture data. At an age of about one year, minimum mature snout-vent length of females was 197 mm. Females probably first gave birth at age two years. Minimum mature snout-vent length of males was 140 mm (age 7-9 months); males may mate during their first spring. Estimates of population density ranged from 348 snakes/ ha in 1969 to 229 snakes/ha in 1971. There was a correspondence between population size and total rainfall during the preceding November-February. Reproduction resulted in estimated annual population increases of 2.6, 3.3, and 2.0 times (19691971). An earlier population study of Virginia striatula (Clark 1964) was based entirely on preserved specimens captured in Bryan-College Station, Brazos County, Texas. Those aspects of this species' ecology best studied by mark-recapture procedures remain poorly known. Our data on trapping success, food habits, growth, maturity, movements, and populations expand earlier findings. Results for V. striatula are compared with findings for the western ribbon snake (Thamnophis proximus) which were obtained concurrently on the same area (Clark 1974). STUDY AREA. The study area (a rectangular plot 89.6 X 189.6 m; 1.70 ha) located at the Texas A&M University Research Annex 6 km WSW of Bryan, Brazos County, east-central Texas had been a one-block portion of the housing area of a 1 Present address: Patuxent Wildlife Research Center, Laurel, Maryland 20810. 2 Present address: School of Forestry Stephen F. Austin State University, Nacogdoches, Texas 75961