Snake Size Research Articles

Consumption of an Adult Mouse by a Free-Ranging Neonate Prairie Rattlesnake

Due to the small size and cryptic nature of young snakes, field data concerning this life history stage are extremely sparse. Since diet can be inferred from stomach contents, data regarding this aspect of the biology of neonate snakes is most abundant. Still, no published data are available concerning the diet of neonate prairie rattlesnakes (Crotalus viridis viridis). Mackessy (1988) reported that southern Pacific rattlesnakes (C. v. helleri) <300 mm in snout-vent length consume lizards exclusively, with a gradual dietary shift to mammals as snout-vent length increases. Similarly, Klauber (1972) suggested that young rattlesnakes feed on lizards predominantly, although no specific data were presented. Such ontogenetic shifts in diet are a consistent phenomenon in the foraging ecology of snakes (Mushinsky, 1987). Mackessy (1988) stated that such a dietary shift in C. v. helleri probably does not result from changing prey preference but from the inability of neonate rattlesnakes to swallow most adult

Feeding Ecology of the Rattlesnake, Crotalus viridis oreganus, in Northern Idaho

Feeding Ecology of the Rattlesnake, Crotalus viridis oreganus, in Northern Idaho

Discrimination of Snakes by Two Populations of Black-Tailed Prairie Dogs

Black-tailed prairie dogs (Cynomys ludovicianus) are large, diurnal, colonial rodents whose basic socialunit is the coterie (Hoogland, 1981; King, 1955), normally containing one adult male, several adult females,yearling males and females, and young of the year (pups). Prairie dogs commonly are confronted with bothvenomous rattlesnakes (Crotalus sp.) and nonvenomous bullsnakes (Pituophis melanoleucus sayi); theyactively harass these snakes (Halpin, 1983; Loughry, 1987a; Owings and Loughry, 1985; Owings and Owings,1979). Other ground squirrels also harass snakes and behave differently toward different species and sizesof snakes (Coss and Owings, 1985). In this paper I ask whether prairie dogs make such distinctions amongsnakes. I also examine whether population history influences snake discrimination by comparing the behaviorof a snake-experienced and a snake-naive population.Prairie dogs were studied at Lower Rankin Ridge in Wind Cave National Park, South Dakota, wheresnakes are rare and Muleshoe National Wildlife Refuge, Muleshoe, Texas, where snakes are common (Lough-ry, 1988). All prairie dogs were dye-marked and ear-tagged. Pups were marked before mixing of litters, somaternity of pups was certain. Paternity of pups was inferred on the basis of observations of breedingbehavior or by tenure of a male within a coterie during the breeding season (Foltz and Hoogland, 1981;Loughry, 1987a, 1988).Large and small rattlesnakes and bullsnakes were tethered (Hennessy et aI., 1981) within a coterie nearan active burrow. In coteries that produced pups, this burrow contained pups. Although the same snakes

Population size and survivorship of the common garter snake, Thamnophis sirtalis, near the northern limit of its distribution

The common garter snake, Thamnophis sirtalis. has frequently been studied, but never in the far north where climatic influences on distribution and abundance might be expected to be severe. We examined the structure and dynamics of a communal den population at the northern limit of the species' range. Snakes were sampled at the hibernaculum from spring 1983 to spring 1987. Males were more easily caught than females, and few inferences could be made about the latter. Population estimates, though possessing wide standard errors, seemed to indicate that the denning population of 500–600 snakes, mostly adults, was stable. Annual survivorship of large males (≥400 mm SVL) was high (0.68–0.98) and was not correlated with body size. Thirty‐four snakes that were first marked in 1983 were recaptured in the spring of 1987, indicating that they had survived at least six years, assuming they were a minimum of two years old when first marked. Recruitment to the denning population consisted of an influx of ‘new’ individuals (450–550 mm SVL) each autumn. It is not known where these snakes spend the first few years of their existence. The relative Stability of numbers and high overwinter survivorship observed over the course of this study contrast sharply with the only previous study of T. sirtalis in cold climates.

Seasonal and Ontogenetic Variation in the Diet of the Mexican Garter Snake, Thamnophis eques, in Lake Tecocomulco, Hidalgo

Stomach contents of Thamnophis eques at Lake Tecocomulco, Mexico, were recorded, and prey populations sampled. Results indicate significant differences in diet between large (>44.0 cm SVL) and small (<44.0 cm SVL) snakes. Large snakes fed mainly on aquatic vertebrates (fishes, frogs, and salamander larvae) and leeches, small snakes on earthworms and leeches. Lack of a correlation between snake size and size of prey (leech or earthworm) indicates that the ontogenetic change in diet is not just a result of predator growth progressively diminishing the availability and/or ability to handle small prey. There was also seasonal variation in prey which was associated with fluctuations in prey availability. Birth season seems associated with annelid abundance. Differences in local distribution of large and small snakes were found and may reflect differences in foraging patterns. Possible effects of allopatry on the diet of this population are discussed.

The Diet of the Hispaniolan Snake Antillophis parvifrons (Colubridae)

Snakes of the xenodontine colubrid genus Antillophis occur on Cuba, several of its satellite islands (A. andreae), and on Hispaniola and many of its satellite islands (A. parvifrons); in addition, a single specimen of A. parvifrons has been taken on Little Inagua Island in the Bahamas (Schwartz and Thomas, 1975). Both species of Antillophis are geographically and ecologically widespread and have differentiated into a number of subspecies (six in A. andreae and nine in A. parvifrons). Antillophis parvifrons is the most widespread (rivaled only by the arboreal Uromacer catesbyi) and abundant species of colubrid on Hispaniola. It is one of the smallest Hispaniolan colubrids: mean snout-vent length (SVL) in our sample was 366 ? 6 mm (range 153-557), and it is similar to some North American garter snakes (Thamnophis) in general habitus. Antillophis parvifrons is an active forager that is diurnal and ground-dwelling. It is ubiquitous in habitat, ranging from lush tropical forest to xeric scrub. It has been taken at altitudes from sea level to 1708 m (Schwartz, 1980). The most recent taxonomic review is that by Thomas and Schwartz (1965); Maglio (1970) discussed skull morphology, zoogeography and origin. Photographs of juvenile and adult A. parvifrons appear in Sajdak and Henderson (1982); a photograph of an adult A. andreae appears in Schwartz and Henderson (1985). Despite its wide distribution and relative abundance on Hispaniola, little is known about the natural history of A. parvifrons. Franz and Gicca (1982) provided information on diet and reproduction for a collection of snakes from Ile de la Gonave, Haiti; and Sajdak and Henderson (1982) added a note on clutch size, description of hatchlings and defensive behavior for animals from Isla Saona, Dominican Republic. In this paper, we present information on the diet of A. parvifrons based on examination of 649 specimens, and discuss diet in terms of foraging mode, prey size, relative prey abundance, and geography. Five hundred and sixty specimens of Antillophis parvifrons from three collections were necropsied at the Milwaukee Public Museum, and we have incorporated the results of the necropsy of 89 specimens by Franz and Gicca (1982). Specimens from collections at the American Museum of Natural History (AMNH), the Museum of Comparative Zoology at Harvard University (MCZ), and the Milwaukee Public Museum (MPM) were examined; the Franz and Gicca material is stored at the Florida State Museum at the University of Florida (FSM). Details of methods used for necropsies and determination of prey volumes appear elsewhere (Henderson 1982, 1984a). The Antillophis were collected throughout the year at many localities throughout Hispaniola (including satellite islands) over a span of about 70 years. We compared snake size (SVL), prey size and diet composition for five localities/regions. Localities in Haiti were: 1) Dept. Sud: St. Croix; (N = 14 specimens/ 8 prey items) 2) Dept. L'Ouest: Tiote (11/8) and 3) Savane Zombi; (12/12) 4) Ile de la Gonave (several sites) (22/6); 5) we lumped specimens from several localities in the Barahona Peninsula of the Dominican

Aspects of the Life History and Ecology of the Desert Night Snake, Hypsiglena torquata deserticola: Colubridae, in Southwestern Idaho

Aspects of the Life History and Ecology of the Desert Night Snake, Hypsiglena torquata deserticola: Colubridae, in Southwestern Idaho

Effect of body size and temperature on skin resistance to water loss in a desert snake

1. 1. Respiratory ( E r) and cutaneous evaporation ( E c) O 2 consumption, cloacal and skin temperatures, were measured in the snake Spalerosophis diadema (12–708 g body mass) at three air temperatures (25, 30, 35°C). 2. 2. Area-specific E c increased with temperature (0.365 mg cm −2 h −1 at 35°C vs 0.220 at 25°C); it accounted for 72% of the total evaporation and was independent of body size. 3. 3. The skin resistance to water loss was independent of the snake's size; its reduction at 35°C (164.2 vs 196.0 s cm −1 at 25°C) contributed significantly to the increase in E c. The boundary layer resistance increased with body size. Its magnitude, however, was less than 4% of the skin resistance.

Swimming in Constricting (Elaphe g. guttata) and Nonconstricting (Nerodia fasciata pictiventris) Colubrid Snakes

The axial skeleton, musculature and the waveform during swimming were examined for Nerodia f. pictiventris, a nonconstricting colubrid, and Elaphe g. guttata, a constricting colubrid. Both species possess qualitatively similar configurations of the segments of three major epaxial muscles (M. semispinalisspinalis, M. longissimus dorsi and M. iliocostalis). Segmental lengths of these three muscles of Elaphe are slightly less than or equal to those of Nerodia, whereas Elaphe has 50% more total vertebrae than Nerodia. Between the two species examined, no differences were found in waveform or maximum swimming velocity, whereas there were slight differences in the relation between relative swimming velocity and the frequency of wave propagation. For both species the amplitude and wavelength of the lateral undulations increased from anterior to posterior. Within each species, relative amplitude and relative wavelength tended to decrease slightly as swimming speed or snake size increased. For Nerodia the maximum absolute swimming velocity scaled with total snake length to the 0.6 power. For all snakes stability in the transverse plane increased with increased swimming speed. Snakes and anguilliform fish exhibited similar burst swimming velocities and a similar relationship between frequency of undulation and relative forward velocity.

Morphology, growth, food habits and population characteristics of the Smooth snake Coronella austriaca in southern Britain

A three year ecological study was made of the Smooth snake in the New Forest, Hampshire. The aim was to provide quantitative information on particular aspects of the Smooth snake's life‐history characteristics. On three study sites, snakes were captured by hand and individually marked. On capture, each snake was identified, sexed, measured, weighed and examined for the presence of food in its stomach and hind gut. In general, mature Smooth snakes showed sexual dimorphism in morphology and growth rates. This was thought to reflect the influence of body size on female reproduction. It was found that Smooth snakes preyed on both small mammals and lizards, suggesting that this species is an opportunist predator. Diet did not vary between study sites. The population sizes were estimated by direct enumeration and densities of one and two snakes per hectare were found. The sex ratios in each study site population were even, and the age structures suggested that both sexes exhibited similar mortality. Consideration was also given to the estimation of the total population size of Smooth snakes in Britain.SummaryThe morphology, growth, food habits and population characteristics of the Smooth snake Coronella austriaca Laurenti were studied in southern England. On capture, each snake was identified, sexed, measured, weighed and examined for the presence of food in its stomach and hind gut.In total, measurements of 22 sexually immature and 92 sexually mature snakes were collected. There was little evidence for sexual dimorphism among immature snakes, though males had relatively longer tails than females. Among mature snakes, females had longer snout‐vent lengths and shorter tails than males. The body weights of breeding females were heavier than those for both non‐breeding females and males. Regardless of age or sex, body weight was positively correlated with snout‐vent length. An analysis of 68 growth measurements revealed that, in common with other species of snake, immature specimens had higher growth rates than mature specimens. Growth within one year did not differ appreciably between males and females. Conversely, growth over more than one year was greatest for female snakes. These differences in morphology and growth were ascribed to the influence that body size has on reproductive success. Large females (i) produce large offspring, and (ii) may have an increased chance of courtship and mating. During non‐breeding years it is suggested that females offset the cost of reproduction through an allocation of energy reserves to bodily growth. Thus individuals may “choose” to grow rather than to breed in particular years. Hence, females in the resting phase of their reproductive cycles may exhibit high growth rates.The Smooth snakes preyed on lizards and small mammals. Nestling prey (young rodents and young shrews taken from underground nests) were the most important dietary items. It was suggested that the Smooth snake is less specialized in its choice of prey than has been previously reported. It was considered to be an opportunist predator, selecting prey according to its availability.Population size was estimated by direct enumeration, and densities of about one and two snakes per hectare were considered representative for this species in Britain. Attention was drawn to the influence that site factors and snake behaviour may have on these calculations. Few immature snakes were captured. It was unclear whether this reflected a higher mortality among these specimens, or whether it was more difficult to find them. The even sex ratio and stable age structure for males and females suggested that mortality was not dependent on the sex of the snakes. Adequate data are lacking for a more comprehensive examination of mortality to be made.An alternative method to the anecdotal estimation of the total population size of Smooth snakes in Britain has been suggested.I wish to record my thanks to Dr I. F. Spellerberg for the advice and support he gave throughout the course of this study. I would also like to thank the Forestry Commission and the Nature Conservancy Council for their permission to undertake this work. Financial support was provided by a University of Southampton Post‐graduate Scholarship. Miss E. C. Meredith and two anonymous referees provided useful comments on parts of this manuscript.

The diets of Hispaniolan colubrid snakes : I. Introduction and prey genera.

Approximately 1590 Hispaniolan colubrid snakes representing six genera and eight species were examined for prey remains (Alsophis cantherigerus, Antillophis parvifrons, Darlingtonia haetiana, Hypsirhynchus ferox, Ialtris dorsalis, Uromacer catesbyi, U. frenatus, and U. oxyrhynchus). The snakes were collected at many localities over a span of 80 years.Of 426 prey items, 77.9% were lizards (of which 69.6% were anoles), 19% frogs, 2.6% birds and mammals, and 0.5% other snakes. Darlingtonia was the only snake that did not exploit lizards; it fed exclusively on Eleutherodactylus frogs, including egg clutches. Disregarding Darlingtonia, there is no size class of Hispaniolan colubrids between 20-90 cm SVL that does not prey primarily on Anolis. Certain prey genera are added to, or deleted from, diets depending on snake size, but the data suggest that snake SVL alone does little to dictate what prey genera (or groups) are eaten. Shannon-Wiener values (H') indicate that Darlingtonia has the narrowest trophic niche, while Alsophis and Ialtris have the widest. Values of H' are not correlated with snake SVL, but highly significant (P<0.001) correlations exist between H' and mid-body circumference, head width, and snout width, and these characters may be indicators of trophic generalists and specialists. Anolis lizards are the most ubiquitous and conspicuous vertebrates on Hispaniola, and it is not surprising that they are widely exploited as a food source. Although as some snake species grow larger, anoles play a decreasingly important role in their diets, there is no evidence to suggest that they are ever abandoned as a food source by any Hispaniolan colubrid of any size.Secretive lizards of low vagility are eaten almost exclusively by wide ranging foragers (Alsophis, Antillophis); very active prey (Ameiva) is taken by sit-and-wait strategists (Hysirhynchus, U. frenatus). Those snakes which exploit the most prey groups are active foragers. Uromacer catesbyi exhibits both foraging modes, and predictably, eats diurnally active (anoles) and diurnally quiescent (hylid frogs) prey with almost equal frequency.Within Maglio's cantherigerus species assemblage, in which an Alsophis cantherigerus-like snake was ancestral to the other species, and in which longsnouted Uromacer are the most morphologically derived, there is an obvious trend toward trophic specialization on Hispaniola. The West Indies have provided an ideal natural laboratory for the investigation of many aspects of vertebrate ecology, and an arena in which to test theories of island biogeography. The most extensively studied West Indian vertebrates have been the lizards of the iguanid genus Anolis. Conversely, the ecology of West Indian snakes has been largely ignored. This is surprising in light of the fact that much has been written about Anolis predation, but little has been written about predators of Anolis; snakes may be important, frequent consumers of anoles.Hispaniola is physiographically and ecologically the most diverse of the Greater Antilles and, concomitantly, it has the most diverse snake fauna, including six colubrid genera containing 11 described species. It has rich frog and lizard faunas, but only two endemic mammals. Study of the diets of Hispaniola's colubrid snakes was undertaken to gain initial insights into the ecology of the snakes and to determine 1) what the snakes eat; 2) what relationships exist between snake diet and snake size as well as head and body proportions; 3) what relationships exist between snake foraging mode and prey type and size; 4) if anoles, as the most ubiquitous and conspicuous vertebrates on Hispaniola, comprise an important source of food; 5) if significant geographical differences in diet exist, expecially on satellite islands; 6) if "north island" and "south island" (sensu Williams 1961) Anolis ecomorphs are preyed upon by the same snake species in similar proportions; 7) if snakes are selective or opportunistic predators.This paper, the first in a series that will address all of the above topics, will briefly describe methods, snake species and prey genera. Prey genera are analyzed in terms of what snake taxa prey upon them, what size classes of snakes prey upon them, and prey genera diversity versus snake size and proportions.

Feeding Mechanisms, Body Size, and the Ecology and Evolution of Snakes

popular view of the Age of Reptiles as a Mesozoic phenomenon that closed with the extinction of dinosaurs does not consider the remarkable evolutionary success of one group of living reptiles, the snakes. This suborder of the Squamata is first known from Cretaceous fossils of extinct groups and boa-like forms (Hoffstetter, 1962). Ancestors of modern snakes, the Caenophidia, appeared in the Paleocene and their radiation in the second half of the Cenozoic has been so rapid and extensive that the Neogene could appropriately be known as The Age of (Stanley, 1979). What is it about snakes that has made them so successful? elongate, legless serpentine body form is a distinctive characteristic of snakes and it influences all areas of their biology. Snakes differ markedly from their closest relatives, the lizards, in body size. Most lizards are small animals weighing less than 20 g as adults and feed on insects. Nearly 80% of living lizard species fit that description and morphological adaptations that appear to be related to insectivorism as a dietary specialty have characterized lizards from their initial appearance in the fossil record (Carroll, 1977: Pough, 1980). In contrast, nearly 75% of snake species have adult body masses greater than 20 g. Because most small mammals also have body masses of 20 g or more, the disparity of body sizes of snakes and lizards places these two suborders of squamate reptiles in quite different relationships with mammals. Lizards appear to avoid competition

Ecology of a Snake Community in Northeastern Brazil

Abstract Nineteen species of snakes representing four families were simultaneously studied in a caatinga habitat of northeastern Brazil. Of these, 10 are terrestrial, 3 are terrestrial-aquatic, 1 is arboreal-terrestrial, 4 are arboreal, and 1 is terrestrial-fossorial. Four species are nocturnal, 5 species are nocturnal and diurnal, and 10 are strictly diurnal. Diets include mammals, birds, bird eggs, lizards, snakes, frogs, toads, and reptile eggs, with some snake species being food specialists and others being food generalists. Surprisingly, none of the species of snakes at the study site feed on invertebrates. A diversity of reproductive tactics is evident among the species in this snake community. There are oviparous and viviparous species, and clutch/brood size may be large or small depending upon the species. Both clutch/brood size and neonate (or egg) size were correlated with body size of female snakes. A principal components analysis (PCA) of morphological data revealed that two axes, one representing variation in body size and one representing variation in tail length and head size, explained 95% ofthe variation in the data. Portions of the morphological results corresponded well with ecological data. However, in some instances the morphological results were discordant with ecological results. Certain patterns, for example appear to have a phylogenetic basis. It is concluded that morphological analyses of snake communities cannot be adequately interpreted in the absence of ecological data.

On the origin of biological similarity

The principles of biological similarity have not been adequately defined. Previous studies have not been fully successful, mainly because the search for such principles centered around the idea that a few of them would apply to all animals, just as Newton's principles of mechanical similarity apply to all inanimate objects. However, this is not possible, so that the search has led up a number of blind alleys, ending with a failure to provide a fundamental and unified explanation—as contrasted with empirical justification—for the scaling of basal metabolic rate of many kinds of animals (e.g. mammals, birds, fish, certain small metazoa) according to a 3 4 - power of body mass, M, rather than as M 2 3 (“surface law”) or M 1·0; moreover, none of the previous theories can account for the fact that other kinds of animals (e.g. insects, snakes, hibernating mammals) do not obey the M 3 4 - rule . Two basic characteristics of all animals are that in the water they are on “the verge of floating” and that movement is interwoven with the nature of animal life itself. These observations lead to the principle of constancy of body density ( ρ ⋍ 1) and to the principle of similarity in some defined sense of the muscular apparatus—the universal generator of movement—across species, but only within classes of animals that have evolved similar methods of locomotion. Because muscle tissues are subject to elastic (“spring-type”) contraction forces, a general elastic similarity principle holds for muscle diameter, d, vs. a linear body dimension, L, i.e., d 2 ∝ L 3 (Galileo-Rashevsky principle; this principle is valid also for the dimensions of the trunk of animals without exoskeleton subject to a gravitational load, e.g. for land mammals but not for sea mammals). A final principle which, combined with the above, leads to the M 3 4 - rule for muscle-power generation, is that time is scaled as the linear dimension, T ∝ L (in contrast to Newton's second principle of mechanical similarity for physical objects, T ∝ L 1 2 ). This principle was introduced in the past either as an arbitrary assumption (Lambert & Teissier) or based on the empirical finding of constancy of muscle shortening velocity ( ∝ L T across mammalian species (Hill-McMahon). However, this principle cannot be valid for the classes of animals which do not obey the M 3 4 - rule . This principle is derived here from the more fundamental principle of constancy, across similar species, of mechanical stress (force over cross-section) endured by contracting muscles. In species such as snakes, however, in which locomotion is generated in a different way, friction forces assume an important role and scaling of time as with mechanical similarity, T ∝ L 1 2 , is obtained by assuming a similar velocity of the animals along their axis as size increases; using this scaling, the deviation of snakes from the M 3 4 - rule is explained. Interestingly, though, such scaling may have limited the maximal body size of snakes. A yet different principle seems to be operating in insects, leading to the scaling: T ∝ L − 1 3 and a faster than body mass increase of basal metabolic rate. Finally, neither heat loss nor surface-related transport appear to be limiting and setting factors for metabolic rate—indeed “surface arguments” are entirely unbased. Only in some situations where the M 3 4 - rule is not obeyed because of heat loss considerations (e.g. dogs adapted to the tropics or to the arctic cold) is a surface argument relevant.

Size and Proportion Relationship Between the Beaked Sea Snake and Its Prey

Size and Proportion Relationship Between the Beaked Sea Snake and Its Prey

The Meaning of the Sound of Rattling By Rattlesnakes To California Ground Squirrels

California ground squirrels (Spermophilus beecheyi) approach, harass and even attack one of their important predators, the rattlesnake (Crotalus viridis). In some of these encounters, rattlesnakes respond with defensive behavior, including rattling. Although the rattle functions primarily as an aposematic signal, we hypothesized that the squirrels extract from the sound the following additional information which indicates the risk associated with interacting with the snake. 1. Rattling indicates that the snake is in a defensive motivational state, which appears to be associated with both a low probability of envenomation and a high probability of retreat by the snake. 2. The intensity and spectral composition of the rattling sound indicates the size of the snake, and risk to the squirrel is positively correlated with snake size. The purpose of these two experiments was to test these hypotheses by exaemining the influence of the rattling sound on the snake-directed behavior of California ground squirrels. In the first experiment we video taped the responses of squirrels to a rattlesnake when it could rattle normally, and to the same snake when its rattle was silenced. In the second experiment, we compared the reactions of squirrels to recordings of the rattling sounds of a large and a small rattlesnake. We found the following. 1. The rattling sound potentiated both contact-promoting and contact-reducing snake-directed behavior by the squirrels. Although the onset of a rattle episode startled the squirrel, the rattle's overall effect was to intensify harassment by the squirrel. Squirrels sand kicked more and at a higher rate and harassed the snake longer when the snake could rattle than when the rattles were silenced. 2. The nature of the rattle's potentiating effect on snake-directed behavior by the squirrel depended on the size related information in the rattling sound. Squirrels turned and ran away from a recording of a large rattlesnake, but approached and investigated a recording of a small rattlesnake. These results suggest both that the squirrels' snake-directed behavior is sensitive to risk and that squirrels extract information from the snake's rattling sounds about the potential costs and benefits of interacting with a rattlesnake.