Diet of Crotalus lepidus klauberi (Banded Rock Rattlesnake)

We describe the diet of Crotalus lepidus klauberi (Banded Rock Rattlesnake) using samples collected in the field and from museum specimens, as well as several records from unpublished reports. Most records (approximately 91%) were from the northern Sierra Madrean Archipelago. Diet consisted of 55.4% lizards, 28.3% scolopendromorph centipedes, 13.8% mammals, 1.9% birds, and 0.6% snakes. Sceloporus spp. comprised 92.4% of lizards. Extrapolation suggests that Sceloporus jarrovii represents 82.3% of lizard records. Diet was independent of geographic distribution (mountain range), sex, source of sample (stomach vs. intestine/feces), and age class. However, predator snout–vent length differed significantly among prey types; snakes that ate birds were longest, followed in turn by those that ate mammals, lizards, and centipedes. Collection date also differed significantly among prey classes; the mean date for centipede records was later than the mean date for squamate, bird, or mammal records. We found n...

The Tzabcan rattlesnake (Crotalus tzabcan) is endemic to the Yucatan Peninsula and is part of the C. durissus complex. Although relatively widespread, it is rather an uncommon species; therefore, little is known about its natural history. Herein, we describe the diet of C. tzabcan on the basis of data from field encounters, museum specimens, and published data. Dietary samples were collected from Campeche, Quintana Roo, and Yucatan, Mexico, and literature records from Belize, representing most of the species' distribution range. Examination of 50 individuals resulted in 28 prey items obtained from 27 snakes. The diet of C. tzabcan consisted exclusively of mammals, including the orders Rodentia (86% of the prey items) and Soricomorpha (7%), and no ontogenetic shift in prey type was detected. However, an ontogenetic telescope is evident, where adults consume larger prey than juveniles but continue feeding on small prey. No sexual dimorphism in snout–vent length and total length was detected in C. tzabcan. No sexual differences in prey mass were found when controlling for snake body length, nor when comparing between sexes in adults and juveniles. The presence of prey was not related to snake collection date, suggesting year-round feeding. There was no difference in prey class and size among snakes from Yucatan dry forest and moist forest. These results suggest a homogenous diet among sexes, seasons, and populations. This is the first detailed study on the diet and feeding ecology of C. tzabcan, and it adds five new prey species: Cryptotys mayensis, Heteromys desmarestianus, H. gaumeri, Oryzomys couesi, and Rattus rattus, as well as two previously reported ones: Mus musculus and Sigmodon toltecus. These findings contrast with anecdotal reports of C. tzabcan consuming reptiles and birds and show many similarities with the related species C. durissus. Additional studies on the natural history of C. tzabcan and related species would help to better understand how the feeding ecology of Neotropical rattlesnakes differs from those species of temperate zones.

The Tehuantepec Isthmus rattlesnake (Crotalus ehecatl) is a poorly known species endemic to Mexico. We describe its diet, morphological variation, life history traits and activity patterns based on data from field encounters, museum specimens, and published data. Its diet consists almost exclusively of mammals, with no detected ontogenetic shift or sexual differences in prey type, and with feeding happening mainly in the rainy season. As the first detailed study on the feeding ecology of C. ehecatl, it adds six new prey species and suggests a homogeneous diet among age classes and sexes, but not among seasons. Crotalus ehecatl does not present sexual dimorphism in snout-vent length, head length or total length, but males have significantly longer tails than females, possess fewer ventral scales, more subcaudal and anterior intersupraocular scales. Crotalus ehecatl showed a unimodal activity pattern with peak activity in the summer, with crepuscular and nocturnal activity during the warmer months, and diurnal activity during the cooler months. The timing of C. ehecatl reproductive events, is similar to other rattlesnakes from temperate and tropical zones. Additional studies on this and related species would help to understand how the ecology of Neotropical rattlesnakes differs from rattlesnakes of more temperate zones.

We identified stomach contents of 80 Plethodon albagula (Western Slimy Salamander) from two mountain ranges in Arkansas (Ozark and Ouachita) to examine if regional differences in diet occur. Museum specimens from 1985 to 2005 were used from locations throughout each mountain range. Although a wide variety of prey were found in stomachs, Hymenoptera: Formicidae and Coleoptera: Carabidae were found to be the most important food items in the diet of P. albagula. Ants and beetles constituted 85% abundance of their total diet (79.6% Ozark and 90.1% Ouachita) and 52.2% of their total biomass (42.6% Ozark and 64.1% Ouachita). Seventy-eight and 87% of individuals examined from the Ozark and Ouachita Mountains, respectively, consumed ants (65% total, 83% for animals with food items in their stomachs), whereas 55% in the Ozarks and 58% in the Ouachitas consumed at least one family of beetle. Occurrence and biomass of prey items that did not include ants and beetles showed P. albagula to be a euryphagic predator, with 9.7% of diet being comprised of other prey types (27.3% biomass). Furthermore, importance values indicate ants were the most important prey item for P. albagula in both the Ozark and Ouachita samples, with carabid beetles (Ozark) and all beetles (Ouachita) being second most important. Jaccard Index indicated Ozark and Ouachita specimens shared 80% similarity in diet. Our data suggest P. albagula in Arkansas have high dependence upon ants and beetles, yet appears to be an opportunistic and euryphagic predator.

Two age classes (0+ to 3+ and 4+ to 7+) of bay gobies (Lepidogobius lepidus Girard) differed in the sizes of whole prey (except polychaetes) recovered from the digestive tract. Although older fish consumed greater amounts of larger prey they did not capture larger individuals of a given prey type for seven of nine prey classes. The remaining two, harpacticoid copepods and ostracods contribute minimally to ontogenetic differences. The switch to larger prey appears to either decrease exposure to predation through a reduction in foraging time or increase energy intake. This is facilitated through older fishes greater size and/or superiority in intraspecific competition. These differences can probably be viewed as adaptations to selective pressures imposed by fluctuating food resources on predation levels in bays and estuaries.

Stability and global dynamic of a stage-structured predator–prey model with group defense mechanism of the prey

Australian elapid snakes possess potent procoagulant venoms, capable of inducing severe venom-induced consumption coagulopathy (VICC) in snakebite victims through rapid activation of the coagulation cascade by converting the FVII and prothrombin zymogens into their active forms. These venoms fall into two mechanistic categories: FXa-only venoms, which hijack host factor Va, and FXa:FVa venoms, containing a complete venom-derived prothrombinase complex. While previous studies have largely focused on human plasma, the ecological and evolutionary drivers behind prey-selective venom efficacy remain understudied. Here, thromboelastography was employed to comparatively evaluate venom coagulotoxicity across prey classes (amphibian, avian, rodent) and human plasma, using a taxonomically diverse selection of Australian snakes. The amphibian-specialist species Pseudechis porphyriacus (Red-Bellied Black Snake) exhibited significantly slower effects on rodent plasma, suggesting evolutionary refinement towards ectothermic prey. In contrast, venoms from dietary generalists retained broad efficacy across all prey types. Intriguingly, notable divergence was observed within Pseudonaja textilis (Eastern Brown Snake): Queensland populations of this species, and all other Pseudonaja (brown snake) species, formed rapid but weak clots in prey and human plasma. However, the South Australian populations of P. textilis produced strong, stable clots across prey plasmas and in human plasma. This is a trait shared with Oxyuranus species (taipans) and therefore represents an evolutionary reversion towards the prothrombinase phenotype present in the Oxyuranus and Pseudonaja last common ancestor. Clinically, this distinction has implications for the pathophysiology of human envenomation, potentially influencing clinical progression, including variations in clinical coagulopathy tests, and antivenom effectiveness. Thus, this study provides critical insight into the ecological selection pressures shaping venom function, highlights intraspecific venom variation linked to geographic and phylogenetic divergence, and underscores the importance of prey-focused research for both evolutionary toxinology and improved clinical management of snakebite.

We describe the diet of the thornscrub hook-nosed snake (Gyalopion quadrangulare) using prey remains removed from the alimentary tracts of museum specimens. Diet consisted of small arthropods, including 9 (31%) insects, 9 (31%) spiders, 8 (28%) scorpions, and 3 (10%) that could not be identified further. Insects included 7 orthopterans (both crickets and grasshoppers) and 2 that we could not identify further. We identified half of the scorpions as Diplocentrus spitzeri. Prey class frequencies are dependent on geographic distribution, but independent of sample source (stomach vs. intestine/feces). Snakes that ate different prey classes did not differ significantly in snout-vent length.

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.

Long-term ecological studies are usually both time-consuming and costly, particularly when conducted on species with low detectability, such as vipers. An alternative, non-expensive method for obtaining detailed information about numerous important ecological traits, e.g. size at maturity, reproductive output, diet composition and amount of body reserves, are dissections of museum specimens. We dissected 237 museum specimens (125 males and 112 females of all age classes) of the nose-horned vipers Vipera ammodytes from the central and western regions of the Balkan Peninsula. Their reproductive and digestive systems were examined, and fat stores estimated. Relative testes volumes were significantly higher in adults than in subadults. Also, we found seasonal variation of testes volumes in adult males. Females became mature at around 43.8 cm snout-to-vent length (SVL); 38.1 % of adult females were pregnant (i.e. had developed eggs/embryos, suggesting bi- or even triennial reproduction frequency). The average number of developed eggs/embryos was 9.1 (range 5–17). As expected, there was a positive correlation between maternal body size (SVL) and the number of embryos. The nose-horned vipers fed predominately on lizards (64.7 %) and mammals (31.9 %); only a few remains of different prey were found (birds, snakes and centipedes). Analyses of inter-sexual differences showed that males more frequently consumed lizards than mammals, while in females both types of prey were equally present. A subtle ontogenetic change in diet was recorded, with a shift from lizards towards mammals. Adult individuals had more fat reserves than subadults, but there were no inter-sexual differences, and gravid females had similar amounts of fat reserves as non-gravid individuals. The data about reproductive output and dietary specialisation demonstrate the vulnerability of the species, generally regarded as “quite common” and non-threatened. This study might help in the establishment of future conservation studies, and management of the impacts of anthropogenic factors on populations of V. ammodytes in the central and western Balkans.

1. Climate change has been occurring at unprecedented rates and its impacts on biological populations is beginning to be well documented in the literature. For many species, however, long‐term records are not available, and trends have not been documented. 2. Using museum specimens from southern USA, we show that the stream‐dwelling beetle Gyretes sinuatus has shown an 8% increase in body size and change in body shape (fineness ratio) from 1928 to 1988. Any directional morphological change observed over time could be an indicator of a microevolutionary response. 3. During these 60 years, there have also been changes in temperature, precipitation, and location of collection sites. Unlike the global trend, mean annual temperature in the region has decreased, and furthermore, total annual precipitation has increased. By investigating how these various ecological and geographical variables may affect body size and shape, we can examine which pressures may promote larger and/or thinner beetles. 4. Results indicate that mean annual temperature was the most predictive variable for the change in size and shape. We suggest there is an adaptive role for temperature on body size and shape of stream dwelling organisms. 5. We found that museum specimens can be invaluable resources of information when collection date and location information is available. We promote the use of such specimens for future studies of the morphological response to climate change.

Contribution of different functional groups to the diet of major predatory fishes at a seagrass meadow in northeastern Japan

Summary A long‐term (13‐year) data set, based on > 4000 kills, was used to test whether a sympatric group of large predators adheres to the theoretical predictions that (1) mean prey body size and (2) prey diversity increase as functions of predator body size. All kills observed by safari guides are documented routinely in Mala Mala Private Game Reserve, South Africa. We analysed these records for lion (Panthera leo, Linnaeus), leopard (Panthera pardus, Linnaeus), cheetah (Acinonyx jubatus, Schreber) and African wild dog (Lycaon pictus, Temminck). Males and females of the sexually dimorphic felid species were treated as functionally distinct predator types. Prey types were classified by species, sex and age class. Prey profiles were compared among predator types in terms of richness and evenness to consider how both the range of prey types used and the dominance of particular prey types within each range may be influenced by predator size. No significant size‐dependent relationships were found, so factors separate from or additional to body size must explain variation in prey diversity across sympatric predators. A statistically strong relationship was found between mean prey mass and predator mass (r2 = 0·86, P= 0·002), although pairwise comparisons showed that most predators killed similar prey despite wide differences in predator size. Also, minimum prey mass was independent of predator mass while maximum prey mass was strongly dependent on predator mass (r2 = 0·71, P= 0·017). The ecological significance is that larger predators do not specialize on larger prey, but exploit a wider range of prey sizes.

Both learning and heritability affect foraging behaviour of red-backed salamanders, Plethodon cinereus

The Javelin Sand Boa, Eryx jaculus, is reported to be a predator of mammals, lizards and their eggs, and occasionally of birds and invertebrates, but data on its diet are scarce and fragmentary. Here we describe some aspects of the feeding behavior of E. jaculus on the Mediterranean island of Sicily. A total of 132 individual snakes were examined. Prey remains were found in 43% of them, both in their feces (82.5%) and gut contents (17.5%). The number of snakes observed and their feeding rate decreased in August, probably as a result of the relatively higher temperatures. Feeding rate increases were observed in adult females in September, perhaps to enhance body reserves before hibernation. The overall prey spectrum is dominated by small mammals, with a frequency of occurrence of 71.4%, but also consisted of lizard eggs (30.2%) and lizards (7.9%). Lizards seem to be occasional prey, and our frequent detection of ingested autotomized tails suggests E. jaculus has low efficiency as a saurian predator. We observed a relationship between prey type and snout–vent length of the snakes. Lizard eggs are most frequently eaten by smaller snakes, which could be linked to gape size ontogenetic variation. We found differences in the prey spectrum between sexes and age classes. Our results indicate that juveniles, adult males, and females seem to adopt different foraging strategies. Females probably adopt ambush predation on small mammals, while juveniles are active foragers of lizard eggs. Adult males appear to be slightly more versatile predators, consuming both types of prey, probably because of their high mobility rates during the mating period.