Abstract: Abstract  Social foraging is suggested to increase foraging efficiency, as individuals might benefit from public information acquired by monitoring the foraging activities of other group members. We conducted a series experiments with captive common marmosets (Callithrix jacchus) to investigate to what extent marmosets utilize social information about food location when foraging simultaneously with conspecifics. Subjects were confronted with dominant and subordinate demonstrators in three experiments which differed in the amount of information about food location available to the demonstrators. In all three experiments, the focal subjects` performance in the social condition was not enhanced in comparison to a non-social control condition. Because we could rule out kleptoparasitism and aggressive displacements as explanations, we argue that the subjects tendency for scramble competition by avoiding others and dispersing over the foraging area seems to inhibit or mask the acquisition of social information about the location of rewarded patches.

Abstract: Data from an outbreak (August to October, 2002) of West Nile virus (WNV) encephalomyelitis in a population of horses located in northern Indiana was scanned for clusters in time and space. One significant (p = 0.04) cluster of case premises was detected, occurring between September 4 and 10 in the south-west part of the study area (85.70 degrees N, 45.50 degrees W). It included 10 case premises (3.67 case premises expected) within a radius of 2264 m. Image data were acquired by the Advanced Very High Resolution Radiometer (AVHRR) sensor onboard a National Oceanic and Atmospheric Administration polar-orbiting satellite. The Normalized Difference Vegetation Index (NDVI) was calculated from visible and near-infrared data of daily observations, which were composited to produce a weekly-1km(2) resolution raster image product. During the epidemic, a significant (p < 0.01) decrease (0.025 per week) in estimated NDVI was observed at all case and control premise sites. The median estimated NDVI (0.659) for case premises within the cluster identified was significantly (p < 0.01) greater than the median estimated NDVI for other case (0.571) and control (0.596) premises during the same period. The difference in median estimated NDVI for case premises within this cluster, compared to cases not included in this cluster, was greatest (5.3% and 5.1%, respectively) at 1 and 5 weeks preceding occurrence of the cluster. The NDVI may be useful for identifying foci of WNV transmission.

Abstract: Communication and social behaviour are inextricably linked, with communication mediating important social behaviours such as resource defence and mate attraction. However, the social environment in which communication occurs is often ignored in discussions of communication behaviour. We argue that networks of several individuals are the common social environment for communication behaviour. The consequences for receivers and signallers of communicating in a network environment are the main subjects of this review. Eavesdropping is a receiving behaviour that is only possible in the environment of a network and therefore we concentrate on this behaviour. The main effect of communication networks on signallers is to create competition with other signallers for receiver attention. We discuss the consequences of such competition. To conclude, we explore the role of signals and signalling interactions as sources of information that animals exploit to direct their behaviour.

Abstract: REASONS FOR PERFORMING STUDY: Field based studies of changes in fitness are difficult to conduct in galloping Thoroughbreds. Measurements of heart rate (HR) and real time velocity with a global positioning system (GPS) could provide a method for routine field studies of fitness. OBJECTIVE: To investigate measurements of fitness in the field without using multiple, standardised steps of increasing velocity in the exercise test. METHODS: Twelve healthy 3- to 5-year-old Thoroughbreds were used in the study of reliability, and twelve 2-year-old Thoroughbreds in the investigation of the effect of training. Five second averages of velocity and HR were recorded during a typical fast exercise training session, using a GPS and Polar HR monitor. A standardised exercise test protocol was not used. Regression analyses using trot and gallop data were used to calculate velocities at HR of 200 beats/min (V200), and at maximal HR (VHRmax). Data were collected on consecutive 'fast' day training sessions to assess the reliability of measurements. The effect of training was investigated with fitness tests in weeks 2 and 6 of 'fast' training. Absolute and relative differences were calculated to evaluate reliability, and paired t tests were used to detect an effect of training. RESULTS: VHRmax, V200 and HRmax were reliable measurements of fitness, with mean differences of 2% or less. Reliability of VHRmax was not dependent on VHRmax. VHRmax and V200 both increased significantly with training (P<0.01), but there was no effect of training on HRmax. There were no significant changes in the slope or intercept of the regression equations after training. CONCLUSIONS: Velocity and HR measurements during field gallop exercise provided reliable measures of fitness which enabled a measurement of the response to training. POTENTIAL RELEVANCE: This approach offers a simple, noninvasive method for monitoring adaptations to training in the field.