Patterns of tail breakage in the ladder snake (Rhinechis scalaris) reflect differential predation pressure according to body size

The adaptive significance of large size at birth in marine snakes

Evolutionary shifts from one habitat type to another can clarify selective forces that affect life-history attributes. Four lineages of snakes (acrochordids and three clades within the Elapidae) have invaded marine habitats, and all have larger offspring than do terrestrial snakes. Predation by fishes on small neonates offers a plausible selective mechanism for that shift, because ascending to breathe at the ocean surface exposes a marine snake to midwater predation whereas juvenile snakes in terrestrial habitats can remain hidden. Consistent with this hypothesis, snake-shaped models moving through a coral-reef habitat in New Caledonia attracted high rates of attack by predatory fishes, and small models (the size of neonatal terrestrial snakes) were attacked more frequently than were large models (the size of neonatal sea snakes). Vulnerability to predatory fishes may have imposed strong selection for increased offspring size in marine snakes.

The frequency of body scarring in Caspian Whip Snakes (Dolichophis caspius Gmelin, 1789) in south-western Hungary

Animals can suffer injuries due to diseases, intraspecific aggression and, most of all, predation events. We present field data to provide numerical information about the injuries found in the largest Caspian Whip Snake (Dolichophiscaspius) population in Hungary, near the northernmost portion of the species’ distribution range.

Ecological significance of dorsal polymorphism in a Batesian mimic snake

Batesian mimicry is the process in which harmless species adopt the appearance of a dangerous, aposematic species. In some prey species, both Batesian mimetic and non-Batesian morphs coexist, presupposing that both morphs have to be evolutionarily advantageous. The viperine snake, Natrix maura, exhibits a zigzag dorsal pattern and antipredatory behavior that mimics European vipers. This snake also has a striped dorsal pattern that coexists with the zigzag pattern. We have examined whether individuals belonging to different geographically structured clades were more likely to exhibit a certain dorsal pattern, and whether the zigzag pattern has a protective function by exposing artificial snakes to predation in natural environments, in addition to comparing antipredatory behavior between zigzag and striped snakes also in natural environments. Our results indicate that the striped pattern was not geographically structured, but habitat-dependent. Aerial predators less frequently attacked zigzag plasticine models than striped or unpatterned models. We detected a shift in antipredator behavior between the 2 morphs, as Batesian mimicking N. maura responded to an approaching potential predator by remaining immobile or fleeing at shorter distances than did striped ones. We conclude that Batesian mimics maintain the cryptic and aposematic value by resembling vipers, whereas in open habitats the non-Batesian mimic has altered its antipredator behavior to maintain its fitness.

A tale of lost tails: pseudoautotomy in the Neotropical snake genus Drymoluber (Serpentes: Colubridae)

Pseudoautotomy (no spontaneous tail breakage without regeneration) occurs in the snakes Drymoluber brazili (Gomes, 1918) and Drymoluber dichrous (Peters, 1863) throughout their geographic range. Examination of 197 specimens of D. dichrous and 60 D. brazili show, respectively, a frequency of tail breakage (FTB) in 26% and 40% of specimens, similar or higher than observed for most species with pseudoautotomy. There is no sexual difference in FTB for D. brazili, and no relationship between tail breakage and snout–vent length (SVL). For D. dicrous, tail breakage is more frequently observed in males when specimens are <710 mm SVL, but for longer specimens, the FTB is higher in females; this strange pattern may not be explained by a single hypothesis. The FTB does not vary significantly between disjunct populations of D. dichrous, suggesting that they are subject to similar predation pressures and escape rates, or minor or no effect of habitat structure on predation risk. The FTB increases with SVL in D. dichrous (but not in D. brazili, probably due to sample size), which is an indication that as the snake grows, the chance of being injured increases and partial tail loss becomes an efficient defense. The multiple tail break hypothesis is not supported for the genus Drymoluber Amaral, 1930, remaining restricted to taxa with specialized pseudoautotomy.