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Ontogenetic variation in the diet of the southern copperhead, Agkistrodon contortrix, in northeastern Texas
Abstract
The stomach contents of a series of 96 specimens of Agkistrodon contortrix from two adjoining counties in northeastern Texas were examined. Arthropods comprized the majority of prey items (53%) but lizards, snakes and a few rodents were also consumed by southern copperheads. Neonate and small copperheads (less than 35 cm SVL) were found to contain more squamata, whereas midsize (35 to 45 cm SVL) and adult snakes (greater than 45 cm SVL) were found to contain primarily cicadas and lepidopteran larva. Only adult specimens were found to contain rodents as prey items. The small gape of neonate and young copperheads appears to restrict them from consuming cicadas and rodents. Large copperheads did continue to consume the small snakes and lizards that constituted the primary prey of small copperheads.
... Copperheads are geographically widespread generalists that utilize a variety of resources along both their dietary and habitat niche axes (Fitch, 1960;Gloyd and Conant, 1990;Ford et al., 1991;Lagesse and Ford, 1996;Schalk et al., 2018). At our study sites, forest management practices shifted the prey base as crickets, anurans, lizards, and spiders were more abundant at the SFAEF, whereas grasshoppers and small rodents were more abundant at SBSCA (Adams et al., 2022). ...
... At our study sites, forest management practices shifted the prey base as crickets, anurans, lizards, and spiders were more abundant at the SFAEF, whereas grasshoppers and small rodents were more abundant at SBSCA (Adams et al., 2022). Although the differences in prey quality (Weidler and Lutterschmidt, 2021;Willson and Hopkins, 2011) from these sites are unknown, all of the aforementioned taxa are preyed upon by copperheads (Fitch, 1960;Gloyd and Conant, 1990;Lagesse and Ford, 1996;Schalk et al., 2018). As a result, shifts in the prey base seem an unlikely mechanism driving the shifts in captures across these two sites. ...
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.
... A. contortrix (Fitch 1960a(Fitch , 1999Lagesse and Ford 1996) indicate the importance of small, generally insect, prey to mid-sized copperheads. However, both Fitch (1999, table 7) and Lagesse and Ford (1996) found a higher percentage of squamates and anurans in the prey of neonates than in mid-size or adult snakes; the Fitch data relate to the population for which we here discuss caudal luring, and we hypothesize that both these prey types MAY respond to caudal luring in natural circumstances. ...
... A. contortrix (Fitch 1960a(Fitch , 1999Lagesse and Ford 1996) indicate the importance of small, generally insect, prey to mid-sized copperheads. However, both Fitch (1999, table 7) and Lagesse and Ford (1996) found a higher percentage of squamates and anurans in the prey of neonates than in mid-size or adult snakes; the Fitch data relate to the population for which we here discuss caudal luring, and we hypothesize that both these prey types MAY respond to caudal luring in natural circumstances. Our hypothesis Table 1 for untransformed data. is not de novo, and is similar to that of Eskew, et al. (2009) regarding juvenile cottonmouths that selectively prey upon salamanders. ...
... The erroneous assumption of semiaquatic habits on other cantils was also refuted by Burchfield (1982), Gloyd and Conant (1990), and Solórzano et al. (1999) for A. taylori, A. bilineatus, and A. howardgloydi, respectively. We also found no substantial evidence that A. russeolus feeds on invertebrates, contrary to its congeners A. contortrix and A. piscivorus (reviewed in Gloyd and Conant 1990;Lagesse and Ford 1996). However, the absence of invertebrates seems to be consistent in the diet of other cantil species. ...
Detailed studies on the natural history of snakes are essential for ecological hypothesis-driven research and effective conservation. Herein, we studied the diet composition and morphology of Yucatecan Cantils (Agkistrodon russeolus Gloyd 1972 [Serpentes: Viperidae]), an understudied viperid species endemic to the Yucatán Peninsula. We collected data from live free-ranging snakes; freshly road-killed snakes and snakes deliberately killed by local villagers; and museum specimens and literature sources. We compared their age classes, sexes, and color morphs. Data came from snakes from Yucatán, Quintana Roo, and Campeche in Mexico, and two records were from northern Belize, comprising most of the species' distribution range. Examination of 76 individuals resulted in 77 prey items from 68 snakes. Results indicated that A. russeolus is a generalist-opportunistic predator that feeds on a wide variety of vertebrates, but primarily on lizards and small mammals and less frequently on birds, snakes, and anurans. Geographic patterns in the diet and morphology of A. russeolus were evident: snakes from the coastal region were smaller in body size and less heavy bodied and with a heavily lizard-based diet, whereas snakes from both dry and moist forest regions were larger and heavier and their diet was primarily mammal based. We did not detect differences in diet composition among age classes because lizards and mammals were eaten at all stages of life, but an “ontogenetic telescope” was evident; that is, the importance of mammals increases with snake body size and the spectrum of prey types consumed also broadens. Males had longer tails than females, and females were light colored more often than males, but other morphological characteristics were similar between the sexes. The sexes and color morphs did not differ in diet composition. We did not detect dietary composition variations between seasons, and our data indicate that this species can feed year-round opportunistically. Because of increasing environmental pressures within its range, studies are urgently needed to elucidate other critical aspects of the ecology of this viperid species.
... Also, a pool of 9 neonate individuals from A. bilineatus (born in captivity) was analyzed using the same RP-HPLC method used for the pooled venoms and it proved to be almost identical to the adult pool (Fig. 3). Intraspecific variation has been also analyzed using the venom of A. contortrix by (Lagesse and Ford, 1996) and found the venom of this species to have only small variations across its distribution. ...
In the present work, venoms from five species of the genus Agkistrodon were evaluated in terms of their enzymatic (Phospholipase A2 and caseinolytic) and biological (edema forming, hemorrhagic, procoagulant and lethal) effects. Horses were used to produce monovalent hyperimmune sera against each of three venoms (A. bilineatus, A. contortrix and A. piscivorus) and their neutralizing potency, expressed as Median Effective Dose (ED50), was determined against the venoms of all five species. In terms of PLA2 and caseinolytic activities, all venoms are extremely homogeneous. PLA2 activity is high, while caseinolytic activity is low when in contrast with that of the rattlesnake Crotalus simus. On the other hand, biological activities showed marked interspecific differences, particularly between the species from Mexico and those from the United States. Mexican species displayed higher edema-forming, hemorrhagic and lethal effects than US species, while none of the species studied presented procoagulant activity. All three monovalent hyperimmune sera showed good neutralizing potency against the analyzed venoms. Nonetheless, we observed relevant immunochemical differences among the venoms using ELISA and Western Blot assays. We conclude that the venoms of A. piscivorus (USA) and A. bilineatus would be ideal to use as immunogens for the production of a polyvalent antivenom with good neutralizing potency against the venoms of all the species of the genus. Keywords: Agkistrodon venoms, Antivenom neutralization, Edema, Hemorrhage, Immunochemistry
... We cannot exclude the possibility that some of the invertebrates may have been incidental prey originally consumed by the lizard prey of A. contortrix and the other snakes in this study. However, previous studies of Texas populations of A. contortrix have found that insects, especially cicadas, comprise a large proportion of the diet (Tennant 1984;Lagesse and Ford, 1996). Similarly, we observed that invertebrates were the most frequent prey consumed by A. contortrix from the WCGP (although due to their small size they may still represent a small proportion of prey biomass). ...
... In contrast, mammals were only present in 18.2% of our samples. Second, while cicadas have frequently been reported in the diet of A. contortrix (Savage, 1967), Lagesse and Ford (1996) reported that only adult A. contortrix (SVL > 350 mm) consumed cicadas. In our study, however, a cicada was found in the gut of a juvenile (SVL = 300 mm). ...
Abstract. Diet samples were collected from seven snake species at a site in southeastern Oklahoma. New diet records were identified for five of the species (10 new records total). Southern copperheads (Agkistrodon contortrix contortrix) were generalists, consuming insects, mammals, lizards, and snakes. Western cottonmouths (Agkistrodon piscivorus leucostoma) also exhibited generalist tendencies, consuming fish, anurans, snakes, and a salamander. Broad-banded watersnakes (Nerodia fasciata confluens) consumed only anurans, and diamond-backed watersnakes (Nerodia rhombifer) ate only fish and anurans. An observation of feeding behaviour at a drying pool is also presented.
Snakes evince the ability to detect substrate-borne mechanical waves (through a variety of substrates) and surface mechanical waves; exactly how these specialized vertebrates accomplish this remains largely unknown. Behavioral and neurophysiological studies in snakes have struggled to differentiate the modalities, mechanisms, and central pathways for the airborne and ground-borne detection of mechanical waves. The snake cochlea is the best-known component of this sensory system; previous studies have shown that the snake cochlea has a rather consistent frequency response range, some intriguing differences in sensitivity, and a mechanical coupling to the middle ear ossicle. How pressure waves reach the middle ear ossicle/cochlea is not clear; whether or not there are pathways (perhaps utilizing the lung) to the cochlea that bypass the ossicle, and the relative role of the snake’s vestibular system in the detection of mechanical waves (if any), remain a mystery. The pathway by which neural signals transduced in the cochlea reach higher brain centers has not been determined in snakes. Perhaps most intriguing, we do not know how pressure stimuli encoded at the cochlea are integrated with stimuli encoded elsewhere on the snake’s body.
Most viperids are ambush predators that primarily use venom to subdue prey, employing a strike-release-trail hunting strategy whereby snakes follow the unique scent of envenomated prey to locate carcasses they have bitten and released. In addition to killing prey, rattlesnakes (like most carnivores) will also opportunistically scavenge carrion. This scavenging strategy likely includes the occasional consumption of carcasses killed by other snakes (i.e., kleptoparasitism). In areas with high densities of other pitvipers, utilizing the unique scent of animals envenomated by other snakes might be a viable alternative foraging strategy. We evaluated this possibility experimentally using a series of captive behavioural
trials on prairie rattlesnakes (Crotalus viridis) to determine whether conspecific or heterospecific (C. scutulatus, C. ornatus) envenomation cues might increase the likelihood of kleptoparasitism. Rattlesnakes did not prefer envenomated prey over nonenvenomated prey, nor did they prefer venom cues of one species over another. Although they did frequently scavenge carcasses, in the absence of striking, snakes generally located carcasses using random searching movements instead of scent trails. Additionally, the amount of time rattlesnakes spent investigating carcass trails did not differ significantly among
treatments, suggesting that striking, and the resultant formation of a chemical search image of prey, is more crucial to trailing behaviour than venom cues. Moreover, a high degree of behavioural variation among individuals was observed, suggesting that scavenging and kleptoparasitism in rattlesnakes is more complex than previously realized, and making generalizations about these behaviours is challenging.
Introduction, The scientific literature on foraging biology in lizards has tended to ignore intraspecific variation. Thus, the species is treated as the unit of analysis, under the implicit assumption that variation within a single species (and, to an even greater degree, within a single population) is trivial relative to variation among species. Many authors therefore talk of broad phylogenetic patterns in foraging mode, with all taxa within major lineages placed within the same major category (e.g. active or ambush). Such generalizations may have substantial value in pursuing broad issues, but at the population level they are simply wrong for many types of organism. Groups of related species certainly share many distinctive features of foraging biology, and there is a genuine validity to statements about lineage-wide patterns. None the less, a detailed analysis of almost any single population (let alone one species) is likely to reveal diversity in trophic biology. For example, juveniles may feed in different ways, in different places and on different kinds and sizes of prey than do adults within the same population. Similarly, males and females may differ in prey utilization. For several reasons, snakes offer more dramatic examples of such intraspecific niche divergence than do lizards. In this chapter, we review published evidence for size and sex effects on foraging biology in snakes, consider underlying biological factors that generate such diversity, and attempt to explain why snakes and lizards – two very closely related groups of organisms – differ so dramatically in the occurrence of intraspecific niche partitioning. é Cambridge University Press 2007.
We conducted two laboratory experiments in order to examine the predatory behavior of neonatal water snakes, Nerodia rhombifer. The first experiment determined habitat use and predatory behavior in three litters of prey- and habitat-naive neonates in small, naturalistic enclosures. The second experiment tested one litter of snakes at three ages from birth to one year in the same enclosures in order to determine ontogenetic changes in habitat use and predatory behavior. The neonates were highly aquatic, foraging only while in water. While negatively buoyant, they focused their activity at the surface of the water. Neonatal snakes were very successful at attacking live fish, capturing most by the head or repositioning them rapidly to a head-first position. The open-mouthed (OM) foraging behavior typical of adults was only rudimentarily developed. Ontogenetic changes in habitat use included a shift to less dense cover and increased use of open water. Ontogenetic changes in behavior included increased underwater activity and decreased surface activity, a higher rate of attacking, and shorter handling times, although snakes captured fewer fish by the head. OM foraging behavior developed, but was still abbreviated as compared to adults at the end of the year. Field studies corroborate the results of these studies.
The diet of the Concho water snake Nerodia harteri paucimaculata was investigated from 1987 to 1990 by palpation of stomach contents. Prey remains representing 304 prey items were recovered from 192 individual snakes. Concho water snakes were almost completely piscivorous, feeding on 19 species of fish from nine families with minnows (Cyprinidae) dominating numerically. Cricket frogs (Acris crepitans) represented the only non-piscine prey. Diet diversity increased ontogenetically according to snake body size. Observations of foraging snakes suggest an ontogenetic change in foraging sites concurrent with a change in diet composition. Prey size was positively correlated with snake body size although some snakes occasionally ingested numerous small prey, possibly due to opportunistic feeding on small prey aggregations. Snakes occasionally attempted to handle prey too large to be ingested. Feeding occurred from mid-March to early November. Gravid females fed throughout the spring into mid-July and resumed feeding after parturition. Neonate and juvenile riverine snakes ingested prey in proportion to apparent availability while adults consumed a disproportionate amount of larger prey species. Lacustrine snakes primarily consumed prey associated with benthic or shallow water habitats. However, few individuals of open water and top water species were ingested, suggesting that prey habitat preference strongly influences catchability in lake systems.