Alex Bager

Seasonality and habitat types affect roadkill of neotropical birds.

Roadkills are amongst the most significant biodiversity impacts, although little is known about the factors which influence the roadkill of neotropical birds. Hence, the objective was to evaluate differences in roadkill richness and rates for neotropical birds according to the seasons of the year and habitat types associated with roads. The data was collected along two federal highways, in southern Brazil. We identified 57 roadkilled species, for a mean roadkill rate of 0.06 ind./km/day (Min.=0.009; Max.=0.47). Our results demonstrate that richness and roadkill rates change according to seasonality and habitat types. Roadkills were concentrated in rice fields and wetlands, intensifying both in richness and rates during the summer and autumn. Nearby areas have similar roadkill rates, independent of habitat types. This probably occurs due to the movement of several species seeking food and shelter. Juvenile dispersion, harvest and grain transportation periods, as well as flight and foraging behaviors over road lanes seem to be related to the increasing roadkill occurrences and richness regarding more abundant species. However, given the elevated number of occasionally roadkilled species (more than 70% with N<5), we believe that highway surface and traffic act as physical barriers which inhibit the movement of many species which either present occasional roadkills or none at all.

NESTING ECOLOGY OF A POPULATION OF TRACHEMYS DORBIGNYI (EMYDIDAE) IN SOUTHERN BRAZIL

Transformation of habitats for agriculture is one of the main causes of reduction in diversity worldwide. We observed reproductively-active female turtles of Trachemys dorbignyi and their nests from 1995 to 2001 in an intensively farmed area in southern Brazil. The area was selected because of the existence of a previous study done 20 yr earlier in the same locality, which allowed us to evaluate the possible effects of human activities on the reproductive ecology of T. dorbignyi. Nesting occurred between October and January, with most activity in November and December (the warmest months). An average of 31% of the females nested in each year, laying up to three clutches at intervals of about 15 days. The females usually constructed nests between 0,700 and 1100 h and deposited 6 to 19 eggs (mean = 12.1) per nest. Clutch size was strongly correlated with carapace length. The eggs were, on average, 39.3 ± 1.73 mm long and 25.8 ± 0.91 mm wide, with a mean mass of 14.9 ± 1.29 g. Multivariate Analysis of Variance showed that egg size differed from year to year. In spite of the intense human activity, the parameters analyzed were nearly unchanged after two decades. However, aspects such as reproductive success, reduction of nesting sites, and the effects of agrotoxins, which could affect the long-term conservation of the species, were not assessed.

Influence of Sampling Effort on the Estimated Richness of Road-Killed Vertebrate Wildlife

Road-killed mammals, birds, and reptiles were collected weekly from highways in southern Brazil in 2002 and 2005. The objective was to assess variation in estimates of road-kill impacts on species richness produced by different sampling efforts, and to provide information to aid in the experimental design of future sampling. Richness observed in weekly samples was compared with sampling for different periods. In each period, the list of road-killed species was evaluated based on estimates the community structure derived from weekly samplings, and by the presence of the ten species most subject to road mortality, and also of threatened species. Weekly samples were sufficient only for reptiles and mammals, considered separately. Richness estimated from the biweekly samples was equal to that found in the weekly samples, and gave satisfactory results for sampling the most abundant and threatened species. The ten most affected species showed constant road-mortality rates, independent of sampling interval, and also maintained their dominance structure. Birds required greater sampling effort. When the composition of road-killed species varies seasonally, it is necessary to take biweekly samples for a minimum of one year. Weekly or more-frequent sampling for periods longer than two years is necessary to provide a reliable estimate of total species richness.

Priority ranking of road sites for mitigating wildlife roadkill

We propose a ranking index to assign priorities to sites for implementation of measures to mitigate wildlife roadkill. We conducted a case study along 34 km of highway BR 392 in Southern Brazil. We compared priority sites established only according to roadkill rates, with those defined by our index. The index used four parameters: the richness of target species, diversity of roadkilled species, roadkill rate of target species, and presence of endangered species. Although it is impossible to protect the entire community of vertebrates affected by roadkill, we defined nine target species, five mammals and four reptiles. For each parameter, we defined coefficients ranging between 0 and 3. There was a significant change in the priorities of sites for implementing mitigation devices, which caused changes in the species that were protected. The definition of priority sites by considering only the roadkill rate protected reptiles especially, to the detriment of all mammal species, including endangered species. Sites with high roadkill rates continued to be among the most important for conservation, but the index diluted the effect of this parameter, changing the ranking. This ranking index can be an effective tool to aid government institutions in decision-making, especially when more elaborate analyses are not feasible for reasons of time, resources, or lack of trained personnel.

Ecologia reprodutiva de Hydromedusa tecifera (Testudines: Chelidae) no sul do Brasil

The few available information on the reproductive behavior of Hydromedusa tectifera (Chelidae) are based on captive individuals. The H. tectifera reproductive biology was verified from 1996 to 2002 by non-systematic surveys in the Estacao Ecologica do Taim, southern Brazil. Forty-six intact and damaged nests of the species were found. Mean clutch size was 11.6 eggs which exhibited a mean size of 36.5 x 23.9 mm and an average weight of 11.5 g. Individual mean eggs volume resulted an average of 10148.31 mm3. Nests had an average depth of 11.1 and 5.8 cm from the surface to the first egg. The eggs volume variation in the same nest was smaller (CV = 4.71%) than among different nests (CV = 12.32%). The eggs width was positively dependent of their length. In the same hatch the number of eggs did not depended of their size or volume. Nesting behavior was observed in November and December. The species showed higher frequency for nesting between 6 and 8 p.m., in areas with certain inclination of the substratum, between 20° and 30° of declivity. Higher nest abundance was verified up to 5 m from the lagoon. The results show that the data obtained for H. tectifera are similar to those previously reported for Australian snake-necked turtles and for species of Chelidae from southern Brazil.

Intentional Snake Road-Kill: A Case Study using Fake Snakes on a Brazilian Road

Records of snakes are common in fauna road-kill monitoring studies in different Brazilian regions. To determine the intentionality of snake road-killing on a Brazilian road, the following hypotheses were tested: (1) more fake snakes are intentionally killed on the road than objects not similar to snakes; (2) the time elapsed until the first intentional fake snake road-kill is less than that for dissimilar objects; (3) the proportion of intentional collisions with fake snakes does not depend on the type of vehicle; (4) objects positioned in the center of the road are more frequently road-killed than those positioned on the roadside; (5) variation in the number of intentional road-kills is linked to variation of vehicular traffic. Fake snakes and PET bottles were placed in different positions on the MG-010 road (Minas Gerais State), and monitored for 96 hours by cameras that recorded the movement of vehicles on the lane. The numbers of intentional snake road-kills and control objects presented no differences, and the time elapsed until the first intentional road-kills was also similar. Cars and trucks are the vehicle categories with highest incidence of collisions. Objects were struck more often when positioned in the center of the road. This study proves that intentional road-killing occurs and that any small object on the road is subject to being struck by a moving vehicle. This behavior by some drivers on Brazilian roads may pose a threat to the conservation of species that venture onto these roads.

Carcass persistence and detectability: reducing the uncertainty surrounding wildlife-vehicle collision surveys

Carcass persistence time and detectability are two main sources of uncertainty on roadkill surveys. In this study, we evaluate the influence of these uncertainties on roadkill surveys and estimates. To estimate carcass persistence time, three observers (including the driver) surveyed 114km by car on a monthly basis for two years, searching for wildlife-vehicle collisions (WVC). Each survey consisted of five consecutive days. To estimate carcass detectability, we randomly selected stretches of 500m to be also surveyed on foot by two other observers (total 292 walked stretches, 146 km walked). We expected that body size of the carcass, road type, presence of scavengers and weather conditions to be the main drivers influencing the carcass persistence times, but their relative importance was unknown. We also expected detectability to be highly dependent on body size. Overall, we recorded low median persistence times (one day) and low detectability (<10%) for all vertebrates. The results indicate that body size and landscape cover (as a surrogate of scavengers’ presence) are the major drivers of carcass persistence. Detectability was lower for animals with body mass less than 100g when compared to carcass with higher body mass. We estimated that our recorded mortality rates underestimated actual values of mortality by 2–10 fold. Although persistence times were similar to previous studies, the detectability rates here described are very different from previous studies. The results suggest that detectability is the main source of bias across WVC studies. Therefore, more than persistence times, studies should carefully account for differing detectability when comparing WVC studies.

Molecular assessment of the phylogeny and biogeography of a recently diversified endemic group of South American canids (Mammalia: Carnivora: Canidae)

Abstract To investigate the evolution and biogeography of an endemic group of South American foxes, we examined mitochondrial DNA control region sequences for 118 individuals belonging to all six extant species of the genus Lycalopex. Phylogenetic and molecular dating analyses supported the inference that this genus has undergone a very recent and rapid radiation, stemming from a common ancestor that lived ca. 1 million years ago. The Brazilian endemic L. vetulus was supported as the most basal species in this genus, whereas the most internal group is comprised by the recently diverged (ca. 350,000 years ago) Andean/Patagonian species L. griseus and L. culpaeus. We discuss the inferred phylogenetic relationships and divergence times in the context of the current geographic distributions of these species, and the likely effects of Pleistocene climatic changes on the biogeography of this group. Furthermore, a remarkable finding was the identification of multiple individuals classified as L. gymnocercus bearing mtDNA haplotypes clearly belonging to L. griseus, sampled in regions where the latter is not known to occur. At a minimum, this result implies the need to clarify the present-day geographic distribution of each of these fox species, while it may also indicate an ongoing hybridization process between them. Future testing of this hypothesis with in-depth analyses of these populations is thus a priority for understanding the history, evolutionary dynamics and present-day composition of this endemic Neotropical genus.

Dietary variation and overlap in D’Orbigny’s slider turtles Trachemys dorbigni (Duméril and Bibron 1835) (Testudines: Emydidae)

Although D’Orbigny’s slider (Trachemys dorbigni) is the most abundant freshwater chelonian species in southern Brazil, little is known about its feeding habits. Our goal was therefore to evaluate this species’ dietary composition and niche variation there. For this, we collected road-killed animals (n = 73) on a federal highway (BR 392) between 2002 and 2003, and analysed their gut contents. We identified 26 different dietary items, and our results indicated that D’Orbigny’s slider is omnivorous in this area. Total food volume, as well as the degree of herbivory and carnivory, were similar between males and females. However dietary composition of plants was different: although both males and females fed on underwater plant matter, only females consumed surface macrophytes. This finding suggested differential microhabitat usage between males and females throughout the swamps.

Fidelity to nesting sites and orientation of Trachemys dorbigni (Duméril & Bibron, 1835) (Testudines: Emydidae) female in southern Brazil

Orientation and fidelity to nesting areas were analyzed in a population of Orbignys slider turtle, Trachemys dorbigni (Duméril & Bibron, 1835), in southern Brazil. Monitoring was carried out over a 5-year period using the mark–recapture technique for females moving overland during the nesting season. The positions of 90 females were analyzed. We also tested the capacity to return to the nesting site after the female was translocated to another point. The overall mean distance between two consecutive captures for females that had not been translocated to the release point was 545.0 m, whereas for females that were translocated the mean distance was 523.8 m. Translocated females showed a high capacity to return to the nesting site, but 2 years were necessary.