Number Of Agonistic Encounters Research Articles

Hummingbird (Aves: Trochilidae) assemblage using resources from the exotic African tuliptree, Spathodea campanulata (Bignoniaceae) in a Neotropical altered environment, southeastern Brazil.

The non-native African tuliptree, Spathodea campanulata (P. Beauv), is widely distributed in altered Neotropical environments, where hummingbirds are important pollinators. We investigated the assemblage of hummingbirds which fed on its nectar and described their behavior, to understand possible influences of the exotic tree on the territorial behavior in an altered environment in southeastern Brazil. Seven species fed on flower resources, mainly Eupetomena macroura (Gmelin, 1788), Amazilia lactea (Lesson, 1832), and Florisuga fusca (Vieillot, 1817). Visiting time was positive correlated with number of flowers accessed, but in most visits, hummingbirds get the nectar by pillage, instead of frontal access. Flower availability varied throughout months; however, we found no evidence of significative correlation between available flowers and number of agonistic encounters. Despite a high number of animal-plant interactions and a strong territorialism of some species observed in African tuliptree foraging site, there may be other plants at local scale influencing the behavioral patterns observed.

Effects of several degrees of chronic social defeat stress on emotional and spatial memory in CD1 mice

In the present study, the effects of several degrees of CSDS (Chronic Social Defeat Stress) on emotional and spatial memory in mice were evaluated in separate experiments. Male CD1 mice were randomly assigned to four experimental groups (n=10–12) for each experiment: NS (non-stressed), S5, S10 and S20 (5, 10 and 20 sessions of CSDS, respectively). The S groups underwent the corresponding number of agonistic encounters (10min each) over a 20-day period. 24h after the last session of CSDS, mice performed the inhibitory avoidance (Experiment 1) or the Morris water maze test (Experiment 2). In both experiments, animals were also evaluated in the elevated plus maze for 5min to obtain complementary measures of locomotor activity and emotionality. The results showed that the highest degree of CSDS had impairing effects on inhibitory avoidance, while there were no significant differences between groups in the water maze. The S20 group exhibited higher anxiety levels in the elevated plus maze. No variations in locomotor activity were observed in any experiment. In conclusion, CSDS has a greater impact on emotional memory than on spatial memory. These negative effects of CSDS on memory do not seem to be secondary to the motor or emotional effects of stress.

Effect of Stocking Density on the Growth, Survival, and Behavior of Postpuerulus Western Rock Lobster, Panulirus cygnus (George) (Decapoda: Palinuridae)

Abstract The effect of four stocking densities (30, 60, 100, and 150 lobsters/m2) on the growth and survival of Panulirus cygnus postpueruli was determined over a 112‐d grow‐out trial. Agonistic behavior at each experimental density was recorded using infrared filming. Survival and growth decreased with increasing density, although this trend was only significant between the lowest (30/m2) and the highest densities (150/m2) (P < 0.05) at the conclusion of the grow‐out trial. Density had no significant effect on apparent feed intake but significantly affected food conversion ratios (FCR) across all four densities, with FCR being best at 30/m2 and worst at 150/m2. The number and frequency of agonistic encounters per tank differed significantly with density, with agonistic encounters being highest at 150/m2 and lowest at 30/m2. Agonistic encounters coincided with the crepuscular foraging pattern of postpueruli. The reduction in survival and growth of postpueruli at the highest density (150/m2) can be attributed to the significant increase in the number of agonistic encounters. This study supports that P. cygnus postpueruli should be stocked at densities less than 100/m2 in order to minimize the negative effect of density on growth and survival.

Behaviour and daily activity of the squirrel Sciurus ingrami in a secondary araucaria forest in southern Brazil

A study on the behaviour of a population of squirrels, the "serelepe" (Sciurus ingrami), was conducted in a secondary araucaria forest in southern Brazil. Forty-three squirrels were marked and observed between 05:00 and 18:00 daily. The largest number of males were trapped during the winter, coinciding with an increase in the number of agonistic encounters and mating chases. Two peaks in occurrence of trapped pregnant females were found, one during the winter and the other in the summer. The population density was 0.89 squirrels/ha and the mean area occupied by males was larger during the winter mating period, decreasing gradually during subsequent seasons. The diurnal activity of S. ingrami exhibited bimodal curves in all seasons, with one peak in the morning and another in the afternoon. During the winter, the morning peak was greater in amplitude than during the other seasons. In the spring and summer, a marked increase in the activity of the squirrels during the hottest hours occurred. The morning peak of activity occurred earlier in the spring and summer and later in the autumn and winter. The daily time spent inrest, displacement, feeding, and maintenance showed seasonal variation similar to that shown by other sciurids.

Behaviour and daily activity of the squirrel <i>Sciurus ingrami</i> in a secondary araucaria forest in southern Brazil

A study on the behaviour of a population of squirrels, the serelepe (Sciurus ingrami), was conducted in a secondary araucaria forest in southern Brazil. Forty-three squirrels were marked and observed between 05:00 and 18:00 daily. The largest number of males were trapped during the winter, coinciding with an increase in the number of agonistic encounters and mating chases. Two peaks in occurrence of trapped pregnant females were found, one during the winter and the other in the summer. The population density was 0.89 squirrels/ha and the mean area occupied by males was larger during the winter mating period, decreasing gradually during subsequent seasons. The diurnal activity of S. ingrami exhibited bimodal curves in all seasons, with one peak in the morning and another in the afternoon. During the winter, the morning peak was greater in amplitude than during the other seasons. In the spring and summer, a marked increase in the activity of the squirrels during the hottest hours occurred. The morning pea...

The Effects of Reduction of Feeding Space on the Behaviour of Captive Starlings Sturnus vulgaris

Eleven captive starlings were given food in troughs. Various parameters of the birds' behaviour were measured when trough length, equivalent to feeding space, was reduced. Restriction of feeding space increased the number of agonistic encounters between feeding birds but did not affect their feeding rates or the total amount of food they took. A dominance hierarchy was established in the flock, in which dominant birds had higher feeding rates and initiated more agonistic encounters than subordinates. All individuals had higher feeding rates when feeding with others than when feeding alone. A stepwise multiple regression analysis showed that the main factors that influenced an individual's feeding rate were the feeding rate of its nearest neighbour and the number of birds feeding at the trough. However, although starlings preferred to feed socially, their behaviour at the feeding trough was highly individualistic, as indicated by the various combinations of factors influencing feeding rates.