História natural de Philodryas patagoniensis (sepentes: colubridae) no litoral do Rio Grande do Sul, Brasil

• Ano de defesa: 2007
• Autor(a) principal: Pontes, Glaucia M. F.
• Orientador(a): Lema, Thales de
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Pontifícia Universidade Católica do Rio Grande do Sul; Porto Alegre
• Palavras-chave em Português: ZOOLOGIA; SERPENTES - RIO GRANDE DO SUL; COLUBRÍDEOS; HERPETOLOGIA; COBRAS - HÁBITOS E CONDUTA
• Link de acesso: http://hdl.handle.net/10923/5327

The present study was carried out in the coastal plain of Rio Grande do Sul with the objective of describe the natural history of the snake Philodryas patagoniensis in this region. The methodology applied was the analysis of digestive tract and reproductive system of specimens in collections collected in the region, and the use of marc-recapture technique in specimens in a 333ha sand dunes area in Balneário Pinhal municipality. Information on diet was obtained from the analysis of 89 specimens kept in collections, and 507 encounters in the study area. From 51 snakes with gut contents, 66 prey items from seven taxonomic categories (fish, anurans, lizards, amphisbaenians, snakes, birds, and rodents), were recorded, indicating the generalist habits of this species. Anurans, present in 56% of the tracts, were the most preyed categories. An ontogenetic shift in the diet was observed, either quantitative (number of items preyed and relative importance) and qualitative (categories consumed). For the study of reproductive aspects and sexual dimorphism were examined the gonads of 88 specimens (52, 36 ) held in collections, besides information on 393 live specimens collected in the study area. Females are born with larger snout-vent length (SVL) than males, and also reach a larger maximum SVL, but males have relatively longer tails. Females reach sexual maturity after the second year of life, while some males can reach it in the first year. Reproduction is seasonal, with vitellogenesis occurring from August to February, clutches from November to February, and births from January to March. The number of eggs per clutch ranged from seven to 21, while the number of vitellogenic follicles ranged from five to 17. The number of eggs and vitellogenic follicles was not related to the SVL of females. The relative clutch mass ranged from 0,217 to 0,403. The pattern of seasonal and daily activity was studied based on 479 encounters recorded in the studied area. Active specimens were found along all months, however the encounter rates of juveniles were higher in autumn and spring, and the encounter rates of adults were higher on spring and summer. The pattern of seasonal activity was similar to males and females, and the capture rates were not correlated with mean monthly temperature or precipitation. The activity was exclusively diurnal, with specimens found active between 6:40 and 18:15. The daily activity varied along the year, being concentrated in the warmer periods in autumn and in winter and displaced to the beginning of the morning and ending at noon in sunny days in spring and summer; in the cloudy days in spring and summer, activity occurred from the beginning of the morning until the middle of noon. Active specimens were found in soil temperatures ranging from 20,0oC to 39,5oC, but with the largest amount of captures between 25oC and 33oC.