Animal communication and Bioacoustics
A major aim of my research is to understand the causes and consequences of animal behaviour in natural environments at both proximate and ultimate levels, for which I use acoustic communication as the model. The methods employed are both reductionist (using behaviour and physiology) and synthetic (using simulations), with concurrent quantification of the natural abiotic and biotic environment, the latter providing the ecological context and thus the selection pressures under which animals must survive and reproduce. My research projects span the areas of bioacoustics, animal behaviour, community and habitat ecology, and systematics. Theoretical, experimental and observational approaches are used in an integrated manner in most of the projects, which often involve both laboratory and field studies.
A major research focus is on understanding sender and receiver strategies for communication in complex natural acoustic environments, which range in scale and scope from patches of tropical rain forest to small choruses of males of a species producing similar calls. Sender strategies being examined include signal structure, calling time and site selection and signaling behaviour. Receiver strategies include physiological and behavioural mechanisms to enhance signal detection, recognition and localization. Habitat structure and acoustics are also examined to understand signal propagation and degradation and their effects on communication. A detailed understanding of senders, signals, signal distortion and receivers should provide insights both into the functioning of natural communication networks and the evolutionary forces that do or do not drive them. A second research focus is to understand decision-making and orientation behaviour in the context of mate choice in natural environments. I am interested in understanding how the physiological processing that underlies decision-making and the ecological context constrain or enable different strategies of mate sampling and mate choice. A third research focus is systematics and phylogenetics, where I focus on understanding species boundaries, acoustic signal evolution and developing acoustics as a tool for identification and monitoring of species diversity. A fourth focus is on understanding the functions of vocal repertoires, currently examined in Asian elephants and racket-tailed drongos.
Raghuram, H., Deb, R., Nandi, D. & Balakrishnan, R. (in press). Silent katydid females are at higher risk of bat predation than acoustically signalling katydid males Proceedings of the Royal Society B http://dx.doi.org/10.1098/rspb.2014.2319 (online first version)
Schmidt, A. K. D. & Balakrishnan, R. (review, in press). Ecology of acoustic signalling and the problem of masking interference in insects. Journal of Comparative Physiology A,
DOI 10.1007/s00359-014-0955-6 (online first version)
Raghuram, H., Jain, M. & Balakrishnan, R. (2014) Species and acoustic diversity of bats in a palaeotropical wet evergreen forest in Southern India. Current Science 107, 631-641.
Deb, R. & Balakrishnan, R. (2014) The opportunity for sampling: The ecological context of female mate choice. Behavioral Ecology 25, 967-974.
Balakrishnan, R., Bahuleyan, J., Nandi, D. & Jain, M. (2014) Modelling the effects of chorus species composition and caller density on acoustic masking interference in multispecies choruses of crickets and katydids. Ecological Informatics 21, 50-58.
Agnihotri, S., Sundeep, P.V.D.S., Seelamantula, C.S. & Balakrishnan, R. (2014) Quantifying Vocal Mimicry in the Greater Racket-Tailed Drongo: A Comparison of Automated Methods and Human Assessment. PLoS ONE 9(3): e89540.
Jain, M., Diwakar, S., Bahuleyan, J., Deb, R. & Balakrishnan, R. (2014) A rain forest dusk chorus: Cacophony or sounds of silence? Evolutionary Ecology 28, 1-22.
Nandi, D. & Balakrishnan, R. (2013). Call intensity is a repeatable and dominant acoustic feature determining male call attractiveness in a field cricket. Animal Behaviour 86, 1003-1012.
Jaiswara, R., Nandi, D. and Balakrishnan, R. (2013). Examining the effectiveness of discriminant function analysis and cluster analysis in species identification of male field crickets based on their calling songs. PLoS One 8, e75930.
Deb, R., Bhattacharya, M. & Balakrishnan, R. (2012) Females of a tree cricket prefer larger males but not the lower frequency male calls that indicate large body size. Animal Behaviour 84, 137-149.
Mhatre, N., Montealegre-Z, F., Balakrishnan, R. & Robert, D. (2012). Changing resonator geometry to boost sound power decouples size and song frequency in a small insect. Proceedings of the National Academy of Sciences USA 109, E1444-E1452 (author summary:8362-8363).DOI:10.1073/pnas.1200192109
Jain, M. & Balakrishnan, R. (2012). Does acoustic adaptation drive vertical stratification? A test in a tropical cricket assemblage. Behavioral Ecology 23,343-354.
Nair, S., Balakrishnan, R., Chandra Sekhar, S. & Sukumar, R. (2009). Vocalisations of wild Asian elephants: structural classification and social context. Journal of the Acoustical Society of America 126: 2768-2778.
Nityananda, V. & Balakrishnan, R. (2009). Modeling the role of competition and cooperation in the evolution of katydid acoustic synchrony. Behavioral Ecology 20: 484 - 489.
Mhatre N. & Balakrishnan R. (2008) Predicting acoustic orientation in complex real-world environments. Journal of Experimental Biology 211:2779-2785.
Diwakar, S., Jain, M. & Balakrishnan, R. (2007). Psychoacoustic sampling as a reliable, non - invasive method to monitor orthopteran species diversity in tropical forests. Biodiversity and Conservation 16, 4081-4093.
Balakrishnan, R. (2005). Species concepts, species boundaries and species identification: A view from the tropics. Systematic Biology 54: 689-693.