Alexandro Marques Tozetti

A Technique For External Radio-Transmitter Attachment And The Use Of Thread-Bobbins For Studying Snake Movements

Abstract Radio-tracking is a widely used method in studies of snake movement and habitat use. However, radio-tracking has some inconveniences, such as the invasiveness of surgical transmitter implantation and the high costs of receivers and transmitters. Here we describe a technique for external radio-transmitter attachment in snakes and the use of thread-bobbins (quilt-cocoons or spool-and-line device) as an alternative for tracking snakes. Both methods allow the animals to resume their natural behavior just after handling and to be monitored until the detachment of the device, usually upon shedding. These characteristics seemed to be particularly useful when the survey must be done within short periods of time with a high number of snakes. The use of thread-bobbins greatly facilitates the gathering of data on movement, habitat use, effective distance moved, and substrate use of snakes in the wild.

Habitat use by the South‐American rattlesnake (Crotalus durissus) in south‐eastern Brazil

Habitat use affects food intake, reproductive fitness and body temperature control in reptiles. Habitat use depends on both the characteristics of the animal and the environmental heterogeneity. In this study we investigated habitat use in a population of the South‐American rattlesnake, Crotalus durissus, in a cerrado (the Brazilian savanna) remnant, in south‐eastern Brazil. In general, snakes appeared to be thermal generalists. However, they showed substrate temperature preferences in the rainy season, when they selected colder substrates during the day and warmer substrates at night. Individuals were predominantly active on the surface and more frequently found under bushes. Furthermore, in general, the principal component analysis results indicate that rattlesnakes are generalists regarding the microhabitat variables examined in this study. These habitat characteristics, associated with a low thermal selectivity, indicate that rattlesnakes are able to colonize deforested areas where shade occurrence and vegetation cover are similar to those in the cerrado.

The Influences of Habitat on Body Temperature Control in a Southern Population of Liolaemus occipitalis (Boulenger, 1885) in Brazil

Abstract. This study aimed to estimate the degree of body temperature control of the sand dune lizard Liolaemus occipitalis in the subtemperate climate region of southern Brazil. The data suggest more accurate thermoregulation in males than females. Sand substrate appears to be more important than air in serving as a heat source for the lizards. The high conductivity of sand might minimize the effects of the relatively low average air temperatures in southern Brazil. Nevertheless, the mean body temperature of L. occipitalis from southern Brazil was lower than that recorded in northern populations of L. occipitalis and other Liolaemus species in southern latitudes of South America. This suggests that maintenance of body temperature might be the limiting factor for the expansion of the southern limit of the species distribution.

Daily Movement and Microhabitat Use by the Blacksmith Treefrog Hypsiboas faber (Anura: Hylidae) during the Breeding Season in a Subtemperate Forest of Southern Brazil

Abstract. We studied the patterns of daily movement and habitat use of 20 males and five females of the blacksmith treefrog, Hypsiboas faber, during the breeding season in a subtemperate forest of southern Brazil. Treefrogs were tracked with externally attached thread bobbins. There were no differences between sexes in the mean straight line distance moved (HSD) or in the effective distance moved (HDM), which ranged from 0.06–3.1 m/h and 0.4–9.8 m/h, respectively). Males showed higher site fidelity and less habitat overlap than females. Despite being an arboreal species, most of the tracked individuals used the herbaceous stratum on the ground as microhabitat, which indicates a particular microhabitat use during breeding activities. Estimates of the distance moved obtained from released thread lines revealed that animals moved distances five times greater than the distances calculated by drawing a straight line between consecutive points. Therefore, our findings suggest that the sedentary behavior attributed to some tropical and subtropical anuran species in tropical and subtropical anuran species forests might not be accurate.

The Influence of Habitat Configuration on Anuran Species Composition in Subtemperate Wetlands of Southernmost Brazil

Abstract. Wetlands of southern Brazil exhibit unique habitat attributes, such as climate pattern and vegetation cover, that can function as an environmental filter for the establishment of species of Neotropical anurans and influence the composition of anuran assemblages. We examined the role of habitat heterogeneity in the composition and relative abundance of anuran species in subtemperate wetlands of southernmost Brazil. We carried out standardized sampling between May 2009 and April 2011 to examine anuran assemblages in marshes associated with grasslands and coastal dunes, as well as habitat heterogeneity. Habitat heterogeneity and anuran species richness were higher in grasslands. Abundance and species dominance, on the other hand, were higher in dunes. This might be due to more restrictive abiotic filters in dunes, such as the low heterogeneity of vegetation cover and lower availability of water bodies. The most common species in grasslands, Leptodactylus cf. latrans, Elachistocleis bicolor, and Pseudis minuta, exhibited a stronger association with habitats with larger and deeper water bodies and with the presence of floating vegetation. The most abundant species found in dunes, Rhinellla arenarum, Odontophrynus maisuma, and Physalaemus biligonigerus, had a stronger association with low vegetation. In addition to habitat associations, the ability to bury themselves might be a behavioral adaptation to dunes that favor species such as O. maisuma and P. biligonigerus, even under extreme microclimatic conditions. Our findings support the importance of the configuration of vegetation cover as well the heterogeneity of water bodies for the establishment of anuran species in subtemperate marshes of southern Brazil.

Calling Site Selection by the South American Tree-Frog Hypsiboas pulchellus (Anura, Hylidae) in Subtropical Wetlands

Abstract. The selection of appropriate calling sites is a key aspect in the reproductive strategy of nearly all anurans. We evaluated if males of the South American tree frog (Hypsiboas pulchellus) select calling sites in undisturbed subtropical wetlands based on specific habitat cues. The study was designed to represent a snapshot of the male calling activity under low densities of intra- and interspecific competitors and little variation of climatic conditions. We characterized calling sites by measuring the vegetation attributes and flood levels of calling sites occupied by 59 males and comparing them to available microhabitats. We found that males exhibit some degree of selectivity for calling sites, often selecting microhabitats with greater density of vegetation < 50 cm tall. Calling site selection was not affected by water depth or area flooded. Most individuals vocalized in sites near the ground (≤ 25 cm), a pattern that is the contrary to that expected to maximize sound propagation. We suggest that, due to the open habitat of the studied area, the choice of calling sites is more related to the need for shelter from predation and avoidance of desiccation and heat loss than to bioacoustic performance.