Population surveys of Nile crocodiles (Crocodylus niloticus) in the Murchison Falls National Park, Victoria Nile, Uganda

1. A 12-month-long survey (April 2013 to March 2014) for Nile crocodiles (Crocodylus niloticus) was conducted along a section of the Victoria Nile/Ramsar site of Murchison Falls National Park, in order to update the historic information on crocodile populations in the area, locating nesting areas, determining seasonality patterns and habitat use, and assess the current abundance and the population size trends since the 1960s. The methods employed included visual encounter surveys, transect counts and opportunistic methods, by using boats.2. In general, there were diurnal and seasonal fluctuations in the number of crocodile sightings. The crocodile sightings peaked between the months of June and August, with the highest mean number of sightings encountered on any single day being 67 (in July 2013), and the second peak was between January and March with  the highest mean of 118 recorded in January 2014. The second peak also coincided with the crocodile breeding  season. This clearly shows that the distribution of the sub-population sampled followed a climatic regime.3. Crocodiles were observed most frequently in water (37%). Grassy banks, islands, river mouths and sandy banks constituted about 47% of the habitats utilised by the crocodile population. Although basking was the most frequent type of activity performed by crocodiles (50%) over the entire survey period, their key activities varied significantly from month to month. Nesting was very visible during the last quarter of the year and the first quarter of the New Year.4. There was a clear decline of the abundance of crocodiles in this population between 1960s and nowadays. This declining trend was obvious also taking into account the various survey methodologies employed over the decades

Quantifying whether different demographic models produce incongruent results on population dynamics of two long-term studied rodent species

1. Population density (ind/ha) of long-term (>15 years) series of CMR populations, using distinct demographic models designed for both open and closed populations, were analysed for two sympatric species of rodents (Myodes glareolus and Apodemus flavicollis) from a mountain area in central Italy, in order to test the relative performance of various employed demographic models. In particular, the hypothesis that enumeration models systematically underestimate the population size of a given population was tested.2. Overall, we compared the performance of 7 distinct demographic models, including both closed and open models, for each study species. Although the two species revealed remarkable intrinsic differences in demography traits (for instance, a lower propensity for being recaptured in Apodemus flavicollis), the Robust Design appeared to be the best fitting model, showing that it is the most suitable model for long-term studies.3. Among the various analysed demographic models, Jolly-Seber returned the lower estimates of population density for both species. Thus, this demographic model could not be suggested for being applied for long-term studies of small mammal populations because it tends to remarkably underestimate the effective population size. Nonetheless, yearly estimates of population density by Jolly-Seber correlated positively with yearly estimates of population density by closed population models, thus showing that interannual trends in population dynamics  were uncovered by both types of demographic models, although with different values in terms of true population size

Better in the dark: two Mediterranean amphibians synchronize reproduction with moonlit nights

In Amphibians, both positive and negative correlations between activity and full moon phase have been observed. In this study, we present data for two anuran species (<i>Hyla intermedia</i> and <i>Rana dalmatina</i>) studied in a hilly Mediterranean area of central Italy. We analysed, in a two-year survey, the relationships between the number of egg clutches laid each night and the moon phases by means of circular statistics. Moreover, the studied species exhibited clear oviposition site selection behaviour influenced, at least in <i>H. intermedia</i>, by moon phases. We observed the occurrence of an avoidance effect by amphibians for oviposition and specific egg-laying behaviour during moon phases around the full moon. This apparent lunar phobia was evident in both species when yearly data were pooled. On the other hand, while this pattern continued to be also evident in <i>H. intermedia</i> when single years were considered, in <i>R. dalmatina</i> it stood just in one year of study. Nonetheless, during cloudy nights, when moonlight arriving on the ground was low, the frogs' behaviour was similar to that observed in new moon phases. We interpreted the observed pattern as an anti-predatory strategy. Overall, comparisons between our own study and previous research suggest that there was insufficient evidence to establish any unequivocal patterns and that further research in this regard is needed

First assessment of age and sex structures of elephants by using dung size analysis in a West African savannah

1. An age and sex structure study of the West African savannah elephant (Loxodonta africana africana) population&nbsp;of the Nazinga Game ranch (Burkina Faso) was carried out using direct sightings of individuals near water&nbsp;points, where they group during hot periods of the day, and droppings circumference measurements of dung&nbsp;pile along line transects, during the dry seasons of 2007 and 2008. The age structure, from direct observation&nbsp;data, was estimated by classifying the individuals into 9 age-class-categories based on body size and eruption&nbsp;(length) of tusks.2. The frequency distribution of number of individuals into the age-class-categories showed high similarity&nbsp;with the distribution of circumference measurements of dung-piles that the individuals were seen depositing.&nbsp;Fifty dung-piles measured soon after they were deposited (Class A) and after they dried (to class C) showed&nbsp;a significant difference between the circumference measurements in relation to the time elapsed between the&nbsp;measurements.3. The frequency distribution of dung circumference classes of the observed elephants was similar to that of the&nbsp;dung-piles measured along the transects in 2008. Therefore, dung-piles measurements were used to estimate&nbsp;the Nazinga Game Ranch savanna elephant population’s age and sex structures at the end of dry seasons of&nbsp;2007 and 2008. We advocated that the Nazinga elephant population consisted mainly of sub-adults.4. The sex ratio was estimated to be in favour of females (1/2). The age-class-specific sex ratio was uneven&nbsp;for calves and young individuals, while being in favour of females with adults. Individuals of less than 1 year&nbsp;represented 6% of the population during the study period

Habitat use and food habitats of a gecko population in a west African suburban area

1.The spatial and trophic ecology of Afrotropical gecko populations are poorly known. Here, we report ecological observations on Brook’s House Gecko (Hemidactylus angulatus), a widespread gekkonid species, in the Rivers State University of Science and Technology campus, Port Harcourt, Nigeria.2. A total of 488 gecko individuals were recorded during the present study, in two surveyed habitat types: (i) plantationm trees (PTH) and (ii) buildings (BDH). In PTH, they were observed in 13 out of 15 species of trees present in the study area, with their (log) frequency of sightings being positively correlated to the (log) frequency of surveyed trees per species.3. The geckos used substantially the non-native ornamental trees of the PTH habitat. Pinus ponderosa and Elaeis guineensis were significantly preferred by geckos over all the other tree species.4. Geckos also used frequently the buildings (BDH habitat) at the university campus. There was no correlation&nbsp;between (log) area of each building and (log) number of observed lizards.5. We collected faeces from 51 gecko individuals in dry season and 66 in wet season. There were no significant&nbsp;dietary differences between seasons, with Diptera and adult Lepidoptera dominating in the diet.6. Dietary habits of geckos differed significantly between habitat types, with Araneae and Lepidoptera (larvae)&nbsp;being eaten much more frequently in BDH, and in Coleoptera and Isopoda that were eaten much more frequently in PTH The diversity dietary metrics (Shannon and Dominance indices) were very similar either between seasons or between habitats.7. Our independent set of analyses (diet diversity metrics; contingency tables on taxonomic dietary composition&nbsp;and rank-abundance diagrams) showed that lizards exhibited a same feeding strategy in both wet and dry seasons as well as in the two habitat types, although the diet composition differed significantly between habitats.8. A “mixed” foraging strategy was apparently used by Hemidactylus angulatus at the study area, as also observed in other gekkonid species from elsewhere

Cuantificación del daño potencial de Dichroplus elongatus y Orphulella punctata (Orthoptera: acrididae) en sorgo y alfalfa

p.199-206Dichroplus elongatus y Orphulella punctada son dos de las especies de tucuras más abundantes de la provincia de Santa Fe. El objetivo del trabajo fue la cuantificación de la ingesta de alfalfa y sorgo por estas dos especies. Para ello se colocaron en jaulas separadas, individuos adultos de ambos sexos e inmaduros, en condiciones semicrontroladas. Las evaluaciones de ingesta se realizaron mediante el pesaje del material verde, antes y a las 24 horas de ser sometidos a los tratamientos con tucuras. Se estimaron los promedios del alimento consumido y se aplicó el test no paramétrico de Wilcoxon. En ambas especies las hembras consumieron mayor cantidad de alimento. Dichroplus elongatus, en todos sus estadíos, tuvo mayor ingesta de alfalfa, mientras que O. punctata consumió más sorgo, Las pérdidas por la ingesta de una generación de 10 D. elongatus por metro cuadrado, se estimaron en 1.002 Kg/ha de alfalfa y 330 Kg/ha de sorgo. La estimación para O. punctata, en las mismas condiciones, fue de 684 Kg/ha de alfalfa y 500 Kg/ha de sorgo

Predictors of orbital convergence in primates: A test of the snake detection hypothesis of primate evolution

Traditional explanations for the evolution of high orbital convergence and stereoscopic vision in primates have focused on how stereopsis might have aided early primates in foraging or locomoting in an arboreal environment. It has recently been suggested that predation risk by constricting snakes was the selective force that favored the evolution of orbital convergence in early primates, and that later exposure to venomous snakes favored further degrees of convergence in anthropoid primates. Our study tests this snake detection hypothesis (SDH) by examining whether orbital convergence among extant primates is indeed associated with the shared evolutionary history with snakes or the risk that snakes pose for a given species. We predicted that orbital convergence would be higher in species that: 1) have a longer history of sympatry with venomous snakes, 2) are likely to encounter snakes more frequently, 3) are less able to detect or deter snakes due to group size effects, and 4) are more likely to be preyed upon by snakes. Results based on phylogenetically independent contrasts do not support the SDH. Orbital convergence shows no relationship to the shared history with venomous snakes, likelihood of encountering snakes, or group size. Moreover, those species less likely to be targeted as prey by snakes show significantly higher values of orbital convergence. Although an improved ability to detect camouflaged snakes, along with other cryptic stimuli, is likely a consequence of increased orbital convergence, this was unlikely to have been the primary selective force favoring the evolution of stereoscopic vision in primates

The ecological distribution of monitor lizards (Reptilia, Varanidaej in Nigeria

The ecological distribulion of three varanid lizards (Varanus exanthematicus, K niloticus niloticus, and V. niloticus ornatusj in Nigeria is studied in the present paper, from both literature records and long-term field ecological research. V. exanthematicus is present only in central and northern Nigeria, where it seerns to be widespread and locally cornrnon in the Guinea savanna vegetation zone, but rnay be found in several spots in the Sudan savanna and even in the Sahel savanna. V. n. ornatus is confined to the extreme south of the country, ¡.e. in the coastal mangrove and deltaic swamp rainforest habita%, and also in the moist lowland rainforest. The distribution of V. n. niloticus remains controversial. It is widespread in the Sudan savanna and in the Guinea savanna, but appears only rarely in the derived savanna and rnoist lowland forest vegetation zones. Despite a few old literature records, it seerns to be absent frorn the rainforest blocks of southern Nigeria. Annual precipitation regimes seem to condition greatly the general distribution patterns of the Nigerian varanids, which are quite generalist in terms of habitat preferences within each rnajor climatic-vegetation zone. Key words: Varanidae, Distribution, Ecology, Nigeria.The ecological distribulion of three varanid lizards (Varanus exanthematicus, K niloticus niloticus, and V. niloticus ornatusj in Nigeria is studied in the present paper, from both literature records and long-term field ecological research. V. exanthematicus is present only in central and northern Nigeria, where it seerns to be widespread and locally cornrnon in the Guinea savanna vegetation zone, but rnay be found in several spots in the Sudan savanna and even in the Sahel savanna. V. n. ornatus is confined to the extreme south of the country, ¡.e. in the coastal mangrove and deltaic swamp rainforest habita%, and also in the moist lowland rainforest. The distribution of V. n. niloticus remains controversial. It is widespread in the Sudan savanna and in the Guinea savanna, but appears only rarely in the derived savanna and rnoist lowland forest vegetation zones. Despite a few old literature records, it seerns to be absent frorn the rainforest blocks of southern Nigeria. Annual precipitation regimes seem to condition greatly the general distribution patterns of the Nigerian varanids, which are quite generalist in terms of habitat preferences within each rnajor climatic-vegetation zone. Key words: Varanidae, Distribution, Ecology, Nigeria.The ecological distribulion of three varanid lizards (Varanus exanthematicus, K niloticus niloticus, and V. niloticus ornatusj in Nigeria is studied in the present paper, from both literature records and long-term field ecological research. V. exanthematicus is present only in central and northern Nigeria, where it seerns to be widespread and locally cornrnon in the Guinea savanna vegetation zone, but rnay be found in several spots in the Sudan savanna and even in the Sahel savanna. V. n. ornatus is confined to the extreme south of the country, ¡.e. in the coastal mangrove and deltaic swamp rainforest habita%, and also in the moist lowland rainforest. The distribution of V. n. niloticus remains controversial. It is widespread in the Sudan savanna and in the Guinea savanna, but appears only rarely in the derived savanna and rnoist lowland forest vegetation zones. Despite a few old literature records, it seerns to be absent frorn the rainforest blocks of southern Nigeria. Annual precipitation regimes seem to condition greatly the general distribution patterns of the Nigerian varanids, which are quite generalist in terms of habitat preferences within each rnajor climatic-vegetation zone. Key words: Varanidae, Distribution, Ecology, Nigeria