William E. Magnusson

RAPELD: a modification of the Gentry method for biodiversity surveys in long-term ecological research sites

Our objectives were to develop a method that would be appropriate for long-term ecological studies, but that would permit rapid surveys to evaluate biotic complementarity and land-use planning in Amazonia. The Amazon basin covers about 7 million km2. Therefore, even a sparse coverage, with one sample site per 10.000 km2, would require about 700 sampling sites. Financial considerations limit the number of sites and investment at each site, but incomplete coverage makes evaluation of biotic complementarity difficult or impossible (Reddy & Davalos 2003). Our next challenge is to install similar systems throughout Amazonia. The cost, based on modification of Al Gentrys original design is moderate (less than US

Effects of Climate and Food Availability on Four Rodent Species in Southeastern Brazil

50.000 per site if it is not necessary to immediately identify all vascular plants in plots) and we can obtain RAP results for most taxa in the short term at much lower cost. However, biological surveys will only be relevant if the local people participate and the surveys serve as much to teach the local communities about the value of their natural resources as they serve to teach the international community about biodiversity. Therefore, we want to see each site run as a long-term ecological research project by local people and institutions. Biological surveys are an important tool in land-use planning, but only the local people can implement those plans.

Topographic and edaphic effects on the distribution of terrestrially reproducing anurans in Central Amazonia : mesoscale spatial patterns

Seasonal reproduction of small mammals in the tropics usually is related to annual cycles of rainfall. We examined effects of weather and food availability on reproduction and population ecology of Nectomys squamipes, Oryzomys intermedius, Akodon cursor and Trinomys iheringi . Each species was studied monthly from February 1993 to January 1995 using mark-recapture methods at Ilha do Cardoso, Sao Paulo State, Brazil. Average capture rate for each month was used as an index of population size, and survival rate was estimated by the Jolly-Seber method. Direct effects of food availability and rainfall were related to female reproductive activity and survival rate. Path analyses were used to describe quantitatively the hypothesized causal relations among the variables. N. squamipes reproduced seasonally, and O. intermedius, T. iheringi , and A. cursor reproduced all year with peaks during the rainy season. Species responded differently to the environmental factors; however, food availability seems to be the main factor determining reproduction. Abundance of rains appears to diminish survival rate of O. intermedius . Survival rate of N. squamipes increases with increases in fruit availability.

Bird diversity in a subtropical South-American City: effects of noise levels, arborisation and human population density.

Many studies suggest that edaphic variables are major determinants of frog distributions. However, leaf-litter depth and soil characteristics are influenced by distance from streams, so the apparent relationship between edaphic characteristics and species distributions could be an artefact of the dependence of species on free water for reproduction. Therefore, we investigated the effect of edaphic variables on the mesoscale distribution of frog species not dependent on free water for reproduction. We evaluated the effects of soil texture, pH, slope, number of trees and leaf-litter volume on the distribution of nine terrestrially reproducing anuran species in the Reserva Ducke, a 100-km 2 terra firme forest preserve in central Amazonia. Diurnal and nocturnal assemblages of anuran species were sampled in 72 plots systematically distributed across the reserve. We sampled the diurnal anuran assemblage by visual encounter in 250 x 1-m plots and the nocturnal assemblage in 250 x 20-m plots using both auditory and visual surveys. The majority of terrestrially breeding anuran species were influenced by topographic and/or edaphic variables, such as slope, soil clay content and pH. However, responses to environmental predictors differed among species. Most species occurred throughout all environmental gradients and relationships with soil characteristics were subtle, indicating that these species occur in the majority of habitats in Reserva Ducke. The results of this study indicate that terrestrially breeding frogs are habitat generalists that show little mesoscale beta diversity associated with habitat variation.

Mortality of Eggs of the Crocodile Crocodylus porosus in Northern Australia

Cities are highly modified environments in which the only areas that resemble natural landscapes are urban parks with low human population density. Attempts are frequently made to maintain high bird diversity in cities for aesthetic or educational reasons. However, it remains unclear whether local site characteristics are important in determining bird assemblage composition or whether simplification of the assemblage is an inevitable consequence of the changes associated with human population density. From May 1998 to December 1999, we undertook bird counts at 521 points in Porto Alegre, Rio Grande do Sul, southern Brazil. Our main goal was to understand the pattern of distribution of the bird species richness and density within the city and determine which variables most affect species assemblages. We recorded 132 species belonging to 43 families that are common in Rio Grande do Sul and obtained quantitative data on 121 species in survey sites. The two most abundant species (House Sparrow, Passer domesticus and Rock dove, Columba livia) were exotics. Analysis based on a reduced subset of 134 points surveyed in spring/early summer suggested that there was a North–south gradient in assemblage structure. Variation in assemblage structure was also affected by the number of trees, urban noise and human population density. However, human population density had a much smaller effect on richness and assemblage structure than variables subject to management, such as tree density and noise levels. These results suggest that complex communities may be maintained in densely populated urban areas of sub-tropical South-America given adequate urban planning.

Factors affecting the use of space by two rodent species in Brazilian Atlantic forest

Most mortality of eggs of Crocodylus porosus in northern Australia is caused by flooding. Floods are of two types, short-term caused by the interaction of rainfall and tidal move- ments, and long-term caused by heavy rain. The duration of inundation necessary to kill eggs in laboratory experiments is longer than that normally experienced during tidal flooding, but less than that experienced during long-term flooding. Nests beside rivers are more likely to be flooded than those in swamps. Predation by varanids and humans causes fewer losses but this is probably because eggs are killed by floods in most years before predators have a chance to take them. The presence of an adult crocodile at the nest appears to deter varanids. Aboriginal hunters apparently are less efficient at finding nests in swamps than nests along rivers.

A Description of Developmental Stages in Crocodylus porosus, for Use in Aging Eggs in the Field*

The main purpose of this study was to determine whether the maximum distance traveled and home range area of Nectomys squamipes and Oryzomys russatus differ between sexes, breeding seasons and species. We also evaluated whether rainfall and food availability influenced the maximum distance traveled. Rats were trapped monthly from February 1993 to January 1995 in an area of Atlantic forest, Brasil. Maximum distance traveled by N. squamipes was not related to mass and was longer during the breeding season for males. There were no differences between seasons in the distances traveled by O. russatus, but larger males traveled further. Food availability and rainfall had no effect on the distance traveled by each species. Home ranges of male N. squamipes were larger than those of females during the breeding season, but home ranges did not differ between the sexes in O. russatus. Differences between the two species in movement may be related to differences in mating systems, which are probably promiscuous in N. squamipes and monogamous in O. russatus.

Limited effects of dominant ants on assemblage species richness in three Amazon forests

Descriptions and measurements of two series of known age embryos of C. porosus are given. Eggs for one series were incubated at temperatures ranging between 27.5 and 29,5C, the other between 30.5 and 31.5D C. Comparison with these series should allow estimation of the approximate time when eggs were laid in the field when the temperature of the nest is known.

Does foraging activity change with ontogeny? An assessment for six sypatric species of post metamorphic litter anurans in central Amazonia

1. Ants are highly interactive organisms and dominant species are considered to be able to control the species richness of other ants via competitive exclusion. However, depending on the scale studied, inter‐specific competition may or may not structure biological assemblages. To date, ant dominance–richness relationships have only been studied in small sample units, where a few dominant colonies could plausibly control most of the sample unit.

An aerial survey of potential nesting areas of the saltwater crocodile, Crocodylus porosus Schneider, on the north coast of Arnhem Land, northern Australia

-We studied the foraging activities of six frog species in their natural habitat, the leaf litter of tropical rain forest in central Amazonia. To describe intraspecific ontogenetic change in general activity during foraging, we used four indices of general activity (movement frequency, velocity when moving, time spent moving, and total distance moved). The association between each of the four indices and the size of frogs varied among species. The indices of foraging activity do not represent independent information. Therefore, we reduced the dimensionality using a single ordination obtained by multidimensional scaling, and investigated its relationship to frog size and type and size of prey. There was a significant relationship between the combined index of foraging activity and frog size in three of the six species. Foraging activity predicted the intraspecific change in the type and size of prey for Eleutherodactylus fenestratus, partially for Adenomera andreae, Epipedobates femoralis, and Dendrophryniscus minutus, and not for Bufo cf. typhonius and Colostethus marchesianus. al of Herpetology, Vol. 34, No. 2, pp. 192-200, 2000 i ht 20 0 Society for the Study of Amphibians and Reptiles oraging Activity Change with Ontogeny? An A essment for patric Species of Postmetamorphic Litter Anurans in There is evidence that the composition of the diet of many amphibians and reptiles depends on how widely the species forages (Huey and Pianka, 1981; Magnusson et al., 1985; Toft, 1985; Wiggins, 1992). For species of leaf-litter frogs, Toft (1981) suggested that the mechanisms that determine the differences in size and type of prey are related to foraging mode. In general, 192 This content downloaded from 207.46.13.113 on Thu, 06 Oct 2016 04:02:39 UTC All use subject to http://about.jstor.org/terms ONTOGENY OF FORAGING ACTIVITY IN SIX LITTER FROGS species that forage actively eat small prey that occur in aggregations, that are slow-moving, that are often chitinous, and often have chemical defenses (e.g., ants, termites, mites). Species that are sit-and-wait foragers eat prey of large size that are normally solitary, such as orthopterans, beetles and spiders (see Striissmann et al., 1984; Toft, 1985; Pough and Taigen, 1990). Toft used frog morphology to infer foraging mode. Changes in sizes and types of prey with growth in size of frogs are expected for morphological reasons and because of changes in the spectrum of prey types that can be swallowed. However, changes in types and sizes of prey of the species of the community of diurnal litter frogs of central Amazonia are not due to a simple passive effect of selection for larger prey with growth of frogs (Lima, 1998). There is a significant relationship between electivity for prey type and frog size in six of the seven species studied, independent of electivity for prey size (Lima and Moreira, 1993; Lima, 1998). Optimal foraging theory is based on the assumption that predators adjust their foraging behavior as the relative availability of prey types shift, such that they always maximize the energy attained during the time spent foraging (Schoener, 1971). However, Pough et al. (1989) questioned whether predators should respond to shifts in the abundance of different sorts of prey by changing their foraging habits in that manner. Pough et al. (1989) suggested that physiological specializations that underlie behavior may limit the ability of a species to adjust its foraging behavior as the abundance of prey changes. Lima and Moreira (1993) suggested that, for one species of central-Amazonian leaflitter frog, Colostethus stepheni, there exists a species-specific level of foraging activity that does not change with frog size, even though the prey available for juveniles are different from those available to adults. Here we report the results of our investigation into whether foraging activity changes with growth for postmetamorphic individuals of six species of diurnal leaf-litter anurans in a central Amazonian assemblage. We compare these results to data on Colostethus stepheni (Lima and Moreira, 1993). We also examine whether the shifts in the sizes and types of prey that occur with the growth of frogs are associated with changes in foraging activity. MATERIALS AND METHODS Study Area and Species.-The study was conducted in a 10,000 ha tropical rainforest reserve, Reserva Florestal Adolfo Ducke (Reserva Ducke), located 25 km northeast of Manaus, Amazonas, Brasil (03?08S; 60?04W). The study was done at two sites separated by 4 km. The first, described by Lima and Moreira (1993), lies along six trails (+7 km) in an undisturbed part of Reserva Ducke. The second, described by Lima (1998), in an area of about 2 km by 200 m wide along the margins of a stream and about 2 km by 10 m on a plateau. The community of diurnal leaf-litter frogs of Reserva Ducke is composed of seven species: Adenomera andreae and Eleutherodactylus fenestratus (Leptodactylidae); Colostethus marchesianus, Colostethus stepheni, and Epipedobates femoralis (Dendrobatidae); Bufo cf: typhonius and Dendrophryniscus minutus (Bufonidae). The juveniles of all species metamorphose at close to 6.5 mm snout-urostyle length (SUL), except for Ep. femoralis and El. fenestratus which metamorphose at more than 8.0 mm SUL. Measures of Foraging Activity.-Foraging activity has generally been indexed by five measures of activity: total time in movement, number of movements, total distance moved, velocity while moving, and frequency of prey capture a tempts. To describe the general activity while raging, we used the first four of these indices. We did not use the frequency of prey capture att mpts because recently-metamorphosed litter anur ns are very small and it was not possible to confidently register all prey-capture events. Observations of the foraging mode of the frogs were made in both study sites between February 1991 and April 1992, and from March to June 1995. Individuals were followed for periods of 30 min in different hours throughout the day so that the entire activity period was covered (Fig. 1). The frogs were watched from distances of 1-5 m using binoculars when necessary. For each minute of observation we noted the number of movements, the total distance moved, and the duration of each movement. A movement was recorded only if it resulted in displacement of the entire body approximately 5 mm. Those observations were used to create f ur indices of activity of foraging: I movement frequency/30 min, II velocity when moving in 30 min (cm/sec), II time spent moving/30 min, and IV total distance moved in 30 min. Th time in movement was recorded with digital chronometers accurate to 0.01 sec. Velocity was estimated as the total distance moved divided by the time spent moving during 30 min. At the end of the observation period, the animals were captured and killed for diet analyses. Statistical Analyses.-Statistical analyses were done with the SYSTAT (Wilkinson, 1990) and PATN (Belbin, 1992) computer programs. The original data for each individual had high variance, were not multivariate normal, and could not be transformed to conform to the assumptions of the analyses. Therefore, to test whether variation of type and size of prey are associated 193 This content downloaded from 207.46.13.113 on Thu, 06 Oct 2016 04:02:39 UTC All use subject to http://about.jstor.org/terms A. P. LIMA AND W. E. MAGNUSSON