Does color polymorphism affect the predation risk on Phalotris lemniscatus (Duméril, Bibron and Duméril, 1854) (Serpentes, Dipsadidae)?

The snake Phalotris lemniscatus is a polymorphic species regarding color, which varies between light shades with a yellow predominance (pale yellow-brown) to darker shades with a red predominance (red-dark). Pale yellow-brown individuals are more frequent in coastal populations while there is a tendency of increasing the frequency of red-dark morphs in inland areas. Considering the variation in substrate color along the species distribution (light/sandy on the coast to reddish and dark/argillaceous in inland areas), we raise the hypothesis that the predation rate of each morph would be lower in sites were its crypsis potential is higher. If correct, this hypothesis would reinforce the idea that the predation risk is one of the factors influencing the spatial structuring in morph frequency distributions in populations of P. lemniscatus. To test this hypothesis, we performed a field experiment using plasticine P. lemniscatus artificial models that represent two morphs: red-dark and pale yellow-brown. The models were distributed in three localities where the following substrate types predominate: light (Coastal Site), intermediary (Lowland Site) and reddish dark (Highland Site). Our predictions were corroborated only at the coastal site, where the less cryptic morph was the most preyed one. We verified that there is a regional variation in the predation risk on different morphs. Thus, the possibility that the selective pressure by predators is a relevant element in the structuring of the frequencies of different morph populations of this species cannot be completely excluded

Evolutionary dynamics shape two passive defensive mechanisms in Neotropical snake radiations

We mapped the distribution of two defensive behaviors (balling and head hiding) of Neotropical snakes to evaluate its distribution in distinct phylogenetic groups. Balling behavior was observed in 58 out of the 167 examined species across seven families. Head hiding was observed in a total of 100 species across nine families. From the high prevalence of balling behavior in basal groups of snakes, such as Anomalepididae, Boidae, Leptotyphlopidae, Tropidophiidae, and Typhlopidae, and the low prevalence among species of recent diversification radiations, such as Elapidae and Viperidae, we suggest that this behavior evolved in basal groups and persisted in some derived taxa. Balling was not observed in association with other defensive strategies, while head hiding can occur in combination with caudal elevation, caudal vibration, and body flattening. Therefore, head hiding, in contrast to balling behavior, presents itself as putatively more flexible, as it should allow for an escalated degree of defensive displays

Daily and seasonal activity patterns of free range South-American rattlesnake (Crotalus durissus)

This study aimed at describing daily and seasonal variation in the activity of a population of South-American rattlesnakes (Crotalus durissus) in a savanna like habitat (Cerrado) in Southeastern Brazil. Seasonal and daily activities of snakes were evaluated by the number of captures of snakes during road surveys, accidental encounters, and relocations by radio-tracking. Our results show that climatic variables such as air temperature and rainfall have little influence on the activity pattern of rattlesnakes. Our findings indicate that rattlesnakes spend most of the day resting and most of the night in ambush posture. The South-American rattlesnake is active throughout the year with a discrete peak in activity of males during the matting season. The possibility of maintaining activity levels even during the coldest and driest season can facilitate the colonization of several habitats in South America. This possibility currently facilitates the colonization of deforested areas by rattlesnakes

Diversity and associations between coastal habitats and anurans in southernmost Brazil

This study aimed to verify the relationship between habitat and the composition of anuran species in dune and restinga habitats in southernmost Brazil. The habitats were sampled between April 2009 and March 2010 using pitfalls with drift fence. We have captured 13,508 individuals of 12 anuran species. Species richness was lower in the dunes and dominance was higher in the resting. Apparently the less complex plant cover, water availability, and wide daily thermal variation in dunes act as an environmental filter for frogs. This hypothesis is reinforced by the fact that the most abundant species (Physalaemus biligonigerus and Odonthoprynus maisuma) bury themselves in the sand, minimizing these environmental stresses. Despite being in the Pampa biome, the studied community was more similar to those of coastal restinga environment of southeast Brazil than with other of the Pampa biome. The number of recorded species is similar to those observed in other open habitats in Brazil, showing the importance of adjacent ones to the shoreline for the maintenance of the diversity of anurans in southernmost Brazil