The ability of a species to defend itself against a predator is directly correlated with its survivorship. Thus, prey/predator interaction mechanisms are important elements of the natural history of species. In this study, we examined the defensive repertoire of the South-American hognose snake (Xenodon dorbignyi) through simulations of predator attacks in the field. Nine defensive displays were observed. The most frequently observed displays were erratic movements, body flattening, head triangulation and tail display. No differences were detected in the defensive strategies shown by males and females, regardless of their reproductive state. Our findings suggest that X. dorbignyi has the ability to evaluate the level of threat imposed by the aggressor, with cryptic behavior, body flattening and locomotor escape as the primary defensive strategies, with other displays used as secondary responses to a predator attack. Our results support the hypothesis that X. dorbignyi is a mimic of both Micrurus and Bothrops.

Reproduction of Pseudis minuta (Anura, Hylidae) in southern Brazil. This study was based on individuals of Pseudis minuta captured or observed in the municipality of Candiota, Campanha region of the state of Rio Grande do Sul, southern Brazil. Sampling occurred along ten non-consecutive months in 2000, 2001 and 2002. The reproductive phases were characterized based on the gonadal development stage of 39 males and 50 females, and on the observation, in nature, of the seasonal distribution of calling males, occurrence of amplectant pairs, and presence of larvae, juveniles and adults. Calls were recorded from August to April, amplectant pairs from October to February (except January), tadpoles from October to March (except February), and juveniles in all the sampled months (except January). Reproductive activity was not observed in late fall and early winter, even though females with post-vitellogenic oocytes and males with spermatozoa in the seminiferous tubules were recorded in all the seasons. Mature females were statistically larger and heavier than mature males. The smallest female with post-vitellogenic oocytes had 32.0 mm of snout-vent length, and the smallest male with spermatozoa in its seminiferous tubules had 20.6 mm. The number of post-vitellogenic oocytes was directly proportional to the mass and to the snout-vent length of females, and the length of testis was directly proportional to the snout-vent length and to the mass of males.

The seasonal and daily activity patterns of Liophis poecilogyrus and the variation in these patterns due to sexual differences and reproductive maturity were investigated based on 174 captures of snakes on the North Coast of Rio Grande do Sul, Brazil. The seasonal activity pattern was unimodal with a higher frequency of active snakes during the hot months. The daily activity pattern was bimodal along most of the year (except during the colder months) with higher frequency of active snakes in early morning and late afternoon. During the colder months, most of the active snakes were found in the hottest periods of the day. There was no signi cant difference regarding activity of the total males and females, mature males and females, immature males and females and mature and immature snakes. The temperature seems to be the most important factor in determining the seasonal and daily activity patterns of this population.Zusammenfassung. Die jahres-und tageszeitlichen Aktivitätsmuster von Liophis poecilogyrus sowie geschlechtsund altersspezi sche Unterschiede in dieser Aktivitätsrhythmik wurden an der Nordküste von Rio Grande do Sul, Brasilien, an Hand von 174 Schlangenfängen untersucht. Das jahreszeitliche Aktivitätsmuster war eingipfelig mit einer höheren Anzahl aktiver Schlangen während der heißen Monate. Die tageszeitliche Aktivität war (außer in den kälteren Monaten) im größten Teil des Jahres zweigipfelig mit einer höheren Anzahl aktiver Schlangen am frühen Morgen und am späten Nachmittag. In der kälteren Jahreszeit waren die meisten Schlangen in den heißesten Tagesstunden aktiv. Keine signi kanten Unterschiede ergaben sich bei Betrachtung der Aktivitäten aller männlichen und weiblichen Tiere, geschlechtsreifer Männchen und Weibchen, nicht geschlechtsreifer Männchen und Weibchen sowie geschlechtsreifer und nicht geschlechtsreifer Tiere. Die Temperatur scheint der wichtigste determinierende Faktor für die jahres-und tageszeitlichen Aktivitätsmuster dieser Population zu sein.

This study aimed to describe the reproductive biology of populations of Thamnodynastes hypoconia in subtemperate wetlands based on macroscopic analyses of their gonads. We analyzed 101 specimens from the southernmost regions of Brazil. The males had a greater snout-vent length, but the females reached sexual maturity with a greater body size. The reproductive cycle of the females was seasonal, with secondary vitellogenesis occurring between the winter and spring (May-October). Based on macroscopic analysis of gonads, data suggests that males have a continuous reproductive cycle. Parturition occurs between the late summer and early fall (January-April). The clutch size ranged between 4 and 16 embryos and showed no relationship with the female's body size. The recorded reproductive frequency of T. hypoconia is low (38 %) compared to other phylogenetically related species. Conversely, the studied populations appear to have a high reproductive success because it is an abundant species in the study site.

We present the first record of Leptophis ahaetulla for the State of Rio Grande do Sul, Brazil. Between November and December 2014, and February 2015, three specimens were found, respectively: one male dead on a highway at the Parque Estadual do Espinilho, a conservation unit located at the municipality of Barra do Quaraí; and two females collected in an anthropic landscape of Salso farm at the municipality of Uruguaiana, Rio Grande do Sul, Brazil. Meristic data and coloration enables the identification of these specimens as Leptophis ahaetulla marginatus.