Social evolution has led to a stunning diversity of complex social behavior, in particular in vertebrate taxa. Thorough documentation of social interactions is crucial to study the causes and consequences of sociality in gregarious animals. Wireless digital transceivers represent a promising tool to revolutionize data collection for the study of social interactions in terms of the degree of automation, data quantity, and quality. Unfortunately, devices for automated proximity sensing via direct communication among animal‐borne sensors are usually heavy and do not allow for the investigation of small animal species, which represent the majority of avian and mammalian taxa. We present a lightweight animal‐borne sensor node that is built from commercially available components and uses a sophisticated scheme for energy‐efficient communication, with high sampling rates at relatively low power consumption. We demonstrate the basic functionality of the sensor node under laboratory conditions and its applicability for the study of social interactions among free‐ranging animals. The first field tests were performed on two species of bats in temperate and tropical ecosystems. At <2 g, this sensor node is light enough to observe a broad spectrum of taxa including small vertebrates. Given our specifications, the system was especially sensitive to changes in distance within the short range (up to a distance of 4 m between tags). High spatial resolution at short distances enables the evaluation of interactions among individuals at a fine scale and the investigation of close contacts. This technology opens new avenues of research, allowing detailed investigation of events associated with social contact, such as mating behavior, pathogen transmission, social learning, and resource sharing. Social behavior that is not easily observed becomes observable, for example, in animals living in burrows or in nocturnal animals. A switch from traditional methods to the application of digital transceiver chips in proximity sensing offers numerous advantages in addition to an enormous increase in data quality and quantity. For future applications, the platform allows for the integration of additional sensors that may collect physiological or environmental data. Such information complements social network studies and may allow for a deeper understanding of animal ecology and social behavior.
Female bats of temperate zones often communally rear their young, which creates ideal conditions for naive juveniles to find or learn about resources via informed adults. However, studying social information transfer in elusive and small-bodied animals in the wild is difficult with traditional tracking techniques. We used a novel ‘next-generation’ proximity sensor system (BATS) to investigate if and how juvenile bats use social information in acquiring access to two crucial resources: suitable roosts and food patches. By tracking juvenile–adult associations during roost switching and foraging, we found evidence for mother-to-offspring information transfer while switching roosts but not during foraging. Spatial and temporal patterns of encounters suggested that mothers guided juveniles between the juvenile and the target roost. This roost-switching behaviour provides evidence for maternal guidance in bats, a form of maternal care that has long been assumed, but never documented. We did not find evidence that mothers guide the offspring to foraging sites. Foraging bats reported brief infrequent meetings with other tagged bats that were best explained by local enhancement. Our study illustrates how this recent advance in automated biologging provides researchers with new insights into longstanding questions in behavioural biology.
Optimization of NALM parameters for phase-preserving amplitude regeneration of a multilevel star8-QAM signal was performed in numerical simulations. A Q-factor improvement of 5 dB for each amplitude level was shown. Possibilities of performance improvement using a power-dependent nonlinear phase shift and a nonlinear amplifier gain were investigated. A Q-factor improvement up to 11 dB for each level was obtained. INTRODUCTIONWith increasing demand for higher transmission capacity and bit rates, multilevel modulation formats have come into the focus of research on optical communications. Compared to common amplitude or phase modulation formats, the combination of phase and amplitude modulation with multilevel encoding, also known as quadrature amplitude modulation (QAM), can significantly increase the channel bit rate for a given symbol rate and thus enables a higher spectral efficiency and, accordingly, transmission capacity in WDM systems. While square-QAM formats with equal distance between constellation points require complex coherent receivers with ultra high speed electronic components, formats like the so-called star8-QAM ( Fig. 1) with two amplitude and four phase states promise simpler receiver architectures [1]. A disadvantage of all QAM formats is their high sensitivity to amplitude and phase noise. In particular amplitude noise does not only diminish the distance of different amplitude levels in the constellation diagram, but is also converted into nonlinear phase noise in the transmission fiber due to the Gordon-Mollenauer effect. This effect can be regarded as one of the major limiting factors for QAM transmission. A possible solution for alleviating this limitation would be the application of phase-preserving multilevel amplitude regenerators. Phase-preserving one-level amplitude regeneration has been already demonstrated for differential quadrature phase-shift keying using a nonlinear amplifying loop mirror (NALM) [2]. The power transfer characteristic of a NALM shows a periodic behaviour which makes this type of devices also a promising candidate for phase-preserving multilevel amplitude regeneration.In this paper we investigate in numerical simulations the fundamental applicability of a NALM for phasepreserving multilevel amplitude regeneration. The limits in amplitude equalization using an optimization of NALM parameters are discussed and possible modifications for multi-level operation are considered.
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