Publication Date:
2022-05-25
Description:
Author Posting. © The Author(s), 2018. This is the author's version of the work. It is posted here under a nonexclusive, irrevocable, paid-up, worldwide license granted to WHOI. It is made available for personal use, not for redistribution. The definitive version was published in Current Biology 28 (2018): 3878-3885.e3, doi:10.1016/j.cub.2018.10.037.
Description:
Toothed whales are apex predators varying in size from 40-kg porpoises to 50-ton sperm whales that all forage by emitting high-amplitude ultrasonic clicks and listening for weak returning echoes [1, 2]. The sensory field of view of these echolocating animals depends on the characteristics of the biosonar signals and the morphology of the sound generator, yet it is poorly understood how these biophysical relationships have shaped evolution of biosonar parameters as toothed whales adapted to different foraging niches. Here we test how biosonar output, frequency, and directivity vary with body size to understand the co-evolution of biosonar signals and sound-generating structures. We show that the radiated power increases twice as steeply with body mass (P ∝ M1.47±0.25) than expected from typical scaling laws of call intensity [3], indicating hyperallometric investment into sound production structures. This is likely driven by a strong selective pressure for long-range biosonar in larger oceanic or deep-diving species to search efficiently for patchy prey. We find that biosonar frequency scales inversely with body size (F∝ M-0.19±0.03), resulting in remarkably stable biosonar beamwidth that is independent of body size. We discuss how frequency scaling in toothed whales cannot be explained by the three main hypotheses for inverse scaling of frequency in animal communication [3-5]. We propose that a narrow acoustic field of view, analogous to the fovea of many visual predators, is the primary evolutionary driver of biosonar frequency in toothed whales, serving as a spatial filter to reduce clutter levels and facilitate long-range prey detection.
Description:
FHJ received support from a Carlsberg Foundation travel grant and an AIAS-COFUND fellowship from Aarhus Institute of Advanced Studies. ML was funded by a PhD stipend from the Faculty of Science and Technology, Aarhus University, and National Research Council grants to PTM. DMW was supported by the Danish National Research Foundation and Carlsberg Foundation grants to PTM. MJ was partly supported by an Aarhus University visiting professorship.
Keywords:
Echolocation
;
Toothed whales
;
Evolution
;
Phylogenetic comparative methods
;
Foraging
;
Ecology
;
Biosonar directivity
;
Field of view
;
Frequency scaling
Repository Name:
Woods Hole Open Access Server
Type:
Preprint
