Zilca Campos

Aerial surveys of caiman, marsh deer and pampas deer in the Pantanal Wetland of Brazil

The yacare caiman (Caiman c. yacare) was illegally hunted in the Pantanal during the 1970s and 1980s at levels that may have reached one million skins per year. The possibility that yacare caiman had been over-exploited generated pressure for a monitoring programme for caiman populations. The marsh deer (Blastocerus dichotomus) and pampas deer (Ozotocerus bezoarticus) are listed as endangered in Brazil and need the protection of effective management programmes. Ground surveys are difficult for the extensive and inaccessible Pantanal Wetland, south-western Brazil, but aerial surveys provided information that allowed re-evaluation of conservation priorities. Caiman and marsh deer have larger populations than was believed. Preliminary data indicates that the pampas deer density decreased at a rate of about 30% per year from 1991 to 1993. This indicates the need for detailed ground-level studies for the pampas deer population in the Pantanal. We recommend a long term monitoring program using standardized counting procedures for wildlife populations in the Pantanal.

Monitoring the Distribution, Abundance and Breeding Areas of Caiman crocodilus crocodilus and Melanosuchus niger in the Anavilhanas Archipelago, Central Amazonia, Brazil

Caiman crocodilus crocodilus and Melanosuchus niger occur throughout most of the Anavil- hanas Archipelago, located in the lower Rio Negro, Central Amazonia. The observed densities of these species vary from 0 to 58 per km of shoreline and 0 to 8 per km of shoreline, respectively. Multiple regression analysis indicated that the temperature difference between the water and the air, and water depth affected the observed density of C. crocodilus during spotlight surveys in the Archipelago. Percentage illumination by the moon, cloud cover, frequency of occurrence of grass, and food availability did not significantly affect the observed density of C. crocodilus. Nine hatchling groups of M. niger that hatched in 1992 were found on islands near the north bank of the Rio Negro, and 15 of 20 hatchlings groups of C. crocodilus were found closer to the south bank, indicating a tendency for separation of nesting areas. Discriminant function analysis indicated that water depth and presence of grass were correlated with the occurrence of hatchling groups. Melanosuchus niger hatchling groups occurred in areas with deeper water and more grass than those of C. crocodilus. This study showed that surveying hatchling groups in the Anavilhanas Archipelago is more efficient than surveying for subadults and adults, which, by itself, can give false impressions about the suitability of areas for conservation of breeding populations of these species.

EFFECT OF HABITAT AND SEASONALITY ON THE DENSITIES OF CAIMAN IN SOUTHERN PANTANAL, BRAZIL

Studies of variation in the population densities of animals are of importance for at least two major reasons: (i) understanding the factors responsible for such variation contributes to general theory of population dynamics (Connell & Souza 1983, McArddle et al. 1990, Pimm & Redfearn 1988, Taylor 1961), and (ii) they provide basic data for management decisions relative to population exploitation or conservation (Caughley 1977, Clark 1976, May 1976). The yacare caiman (Caiman crocodilusyacare) was subject to illegal harvesting during the last three decades and was possibly the most exploited crocodilian in the world (Crawshaw 1987). More recently, legal exploitation of natural populations of yacare caimans has been permitted through a ranching system where eggs are collected in the wild and hatchlings are raised in captivity for commercial purposes. Another potential strategy for managing natural populations of caimans in the Pantanal is to establish a sustained yield-harvesting programme of larger caiman, which may be effective in promoting habitat conservation. However, in both cases accurate and precise methods to estimate populations size and/or trends are required to evaluate impacts (Webb & Smith 1987). Spotlight surveys have been widely used to monitor crocodilian populations and are precise and accurate in some habitats (Chabreck 1966, Glastra 1983). In the Pantanal, spotlight surveys have been of limited use because: (i) reaching remote areas by boat is logistically difficult; (ii) the wetlands are heavily vegetated such that crocodiles are difficult to see at night (Campos et al. 1995); and

Survey of broad-snouted caiman Caiman latirostris, marsh deer Blastocerus dichotomus and capybara Hydrochaeris hydrochaeris in the area to be inundated by Porto Primavera Dam, Brazil

We surveyed broad-snouted caiman Caiman latirostris, marsh deer Blastocerus dichotomus and capybara Hydrochaeris hydrochaeris along the Parana River of southeastern Brazil in the area to be flooded by the Porto Primavera Dam. We conducted night-light counts along 124 km of the Parana River and its tributaries. The mean observed density was 0·12 caiman per km surveyed. We counted caiman nests, marsh deer, and capybara groups over 957 km2 of habitat representing 43% of the area to be flooded, by means of aerial survey. The mean estimated density was 0·49 caiman nest/km2, 0·51 deer/km2, and 0·16 capybara groups/km2. Extending these results to the 1280 km2 of floodplains in the area, we estimated 630 caiman nests per year, 650 marsh deer, and 200 groups of capybara to occur in the area. We recommend the creation of a protected area to guarantee the survival of the broad-snouted caiman and marsh deer in this region.

Relationships between rainfall, nesting habitat and fecundity of Caiman crocodilus yacare in the Pantanal, Brazil

Differences in rainfall between years influenced the proportions of different types of nesting habitats of Caiman crocodilus yacare available near water bodies in a region of intermittent rivers (Campo Dora Ranch). In contrast, rainfall had little effect on the proximity of nesting habitat to water bodies in a region of isolated lakes (Nhumirim Ranch). There was a strong positive correlation between female body size and clutch size Snout-vent lengths of females on Campo Dora Ranch were significantly larger than those from Nhumirim Ranch which probably accounts for the larger mean clutch size than in the region of isolated lakes. Hatchling size was correlated with egg size, but there was no relationship between egg size and female size or egg size and clutch size.

Ilheus Virus Isolation in the Pantanal, West-Central Brazil

The wetlands of the Brazilian Pantanal host large concentrations of diverse wildlife species and hematophagous arthropods, conditions that favor the circulation of zoonotic arboviruses. A recent study from the Nhecolândia sub-region of Pantanal reported serological evidence of various flaviviruses, including West Nile virus and Ilheus virus (ILHV). According to the age of seropositive horses, at least three flaviviruses, including ILHV, circulated in the Brazilian Pantanal between 2005 and 2009. To extend this study, we collected 3,234 adult mosquitoes of 16 species during 2009 and 2010 in the same sub-region. Mosquito pool homogenates were assayed for infectious virus on C6/36 and Vero cell monolayers and also tested for flaviviral RNA by a group-specific real-time RT-PCR. One pool containing 50 non-engorged female specimens of Aedes scapularis tested positive for ILHV by culture and for ILHV RNA by real-time RT-PCR, indicating a minimum infection rate of 2.5 per 1000. Full-length genomic sequence exhibited 95% identity to the only full genome sequence available for ILHV. The present data confirm the circulation of ILHV in the Brazilian Pantanal.

Terrestrial Activity of Caiman in the Pantanal, Brazil

Abstract Coordinated terrestrial movement has not previously been reported in crocodilians. However, between 1989 and 1999, 94% of 525 Caiman crocodilus yacare found on land in the Pantanal were in coordinated groups (n = 73) walking head to tail and forming nearly straight lines. Caimans left pools and initiated terrestrial movements spontaneously and in response to disturbance by researchers and hunters. The sex ratio of the groups was biased toward males (0.8 ± 0.24) and was similar to that found in aquatic habitats in the study area. However, two groups consisted only of females. When caimans left pools subjected to disturbances, such as hunting and capture for research, they walked head to tail in lines. Caimans that left pools in response to disturbance buried in mud near pools or in leaf litter in forest.

Maximum size of dwarf caiman, Paleosuchus palpebrosus (Cuvier, 1807), in the Amazon and habitats surrounding the Pantanal, Brazil

The dwarf caiman, Paleosuchus palpebrosus , is considered one of the smallest crocodilians. However, our surveys indicate that the species regularly reaches larger sizes than usually reported in the literature. Most individuals lose tail tips, and we did not encounter any individual with snout-vent length (SVL) > 70 cm that had an intact tail. P. palpebrosus attains SVL > 112.5 cm (equivalent to a total length with intact tail estimated from SVL of 210 cm) in streams around the Pantanal, 106 cm (198 cm) in flooded forest in central Amazonia, and 100 cm (187 cm) in flooded forest and around the Madeira-Guapore River.

Growth rates of black caiman (Melanosuchus niger) and spectacled caiman (Caiman crocodilus) from two different Amazonian flooded habitats

Rates of growth and survival in wild populations are affected by the physical environment, biotic interactions, and density-dependent processes, such as growth and fecundity. However, the relative importance of these factors in long- lived reptiles is poorly understood. We analyzed growth rates of Melanosuchus niger and Caiman crocodilus coexisting in two areas of the Brazilian Amazon with very different environmental characteristics. Growth rates of Caiman crocodilus at the two sites were similar, but M. niger grew more slowly in the area with higher productivity and higher density of caimans. Growth rates of the same species from other sites and of the temperate-zone Alligator mississippiensis indicate large differences among sites, but little evidence that these differences are primarily due to differences in productivity or temperature. Demographic models used to estimate sustained yields from caiman harvests should take into account the likely importance of density-dependent growth.

Parental care in the dwarf caiman, Paleosuchus palpebrosus Cuvier, 1807 (Reptilia: Crocodilia: Alligatoridae)

Post-hatching parental care is common in crocodilians, but the little information available for Cuviers dwarf caiman (Paleosuchus palpebrosus) indicates that they show little post-hatching parental care. During surveys undertaken between 2005 and 2011, we counted and captured groups of hatchlings and observed the presence or absence of attending adults in streams around the Pantanal, along the Guaporé-Madeira River and flooded forest in central Amazonia, Brazil. We found 37 groups of hatchlings, of which 29 were accompanied by adults. We captured 13 of these adults and all were females. The groups of hatchlings remained with adults for up to 21 months. We monitored females and hatchlings in streams around the Pantanal using captures and with radiotelemetry and showed that females and hatchlings frequently remained together in burrows, especially during the dry season.