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Journal of Comparative Physiology A (2018) 204:377–389
https://doi.org/10.1007/s00359-018-1246-4
ORIGINAL PAPER
Modulation rate transfer functions from four species of stranded
odontocete (Stenella longirostris, Feresa attenuata, Globicephala melas,
and Mesoplodon densirostris)
Adam B. Smith
1,2
· Aude F. Pacini
1,2
· Paul E. Nachtigall
1,2
Received: 25 July 2017 / Revised: 2 January 2018 / Accepted: 8 January 2018 / Published online: 19 January 2018
© Springer-Verlag GmbH Germany, part of Springer Nature 2018
Abstract
Odontocete marine mammals explore the environment by rapidly producing echolocation signals and receiving the corre-
sponding echoes, which likewise return at very rapid rates. Thus, it is important that the auditory system has a high temporal
resolution to effectively process and extract relevant information from click echoes. This study used auditory evoked potential
methods to investigate auditory temporal resolution of individuals from four different odontocete species, including a spin-
ner dolphin (Stenella longirostris), pygmy killer whale (Feresa attenuata), long-finned pilot whale (Globicephala melas),
and Blainville’s beaked whale (Mesoplodon densirostris). Each individual had previously stranded and was undergoing
rehabilitation. Auditory Brainstem Responses (ABRs) were elicited via acoustic stimuli consisting of a train of broadband
tone pulses presented at rates between 300 and 2000 Hz. Similar to other studied species, modulation rate transfer functions
(MRTFs) of the studied individuals followed the shape of a low-pass filter, with the ability to process acoustic stimuli at
presentation rates up to and exceeding 1250 Hz. Auditory integration times estimated from the bandwidths of the MRTFs
ranged between 250 and 333 µs. The results support the hypothesis that high temporal resolution is conserved throughout
the diverse range of odontocete species.
Keywords Dolphin · Toothed whale hearing · Auditory evoked potentials · Modulation rate transfer function · Auditory
temporal resolution
Abbreviations
ABR Auditory brainstem response
EFR Envelope following response
ERB Equivalent rectangular bandwidth
ERD Equivalent rectangular duration
FFT Fast Fourier transform
MRTF Modulation rate transfer function
RFR Rate following response
SAM Sinusoidally amplitude modulated
Introduction
Odontocetes (toothed whales and dolphins) possess highly
developed echolocation systems, which require both the
effective production of echolocation clicks and also the
reception of click echoes. Echolocation clicks are short-
duration acoustic signals that are produced at variable rates
depending on the distance between the dolphin and an echo-
location target (e.g., Au 1993; Au and Benoit-Bird 2003).
Inter-click intervals can be as low as 1.5–3 ms, correspond-
ing to click rates in some species as high as 300 to above
400 clicks per second (e.g., Lammers et al. 2004; Madsen
et al. 2004; Verfuß et al. 2009), which are often associated
with the final moments of prey capture. Echoes during such
click trains can likewise return to the animal at similarly
high rates. Temporal and spectral characteristics of target
echoes contain important information about the target that
are processed by the odontocete auditory system (Bullock
et al. 1968; Au et al. 1988; Au 1993). Thus, it is important
that the auditory system has a high temporal resolution to
* Adam B. Smith
adambsmi@hawaii.edu
1
Department of Biology, University of Hawai‘i at Mānoa,
2538 McCarthy Mall, Edmondson Hall Room 216,
Honolulu, HI 96822, USA
2
Hawai‘i Institute of Marine Biology, 46-007 Lilipuna Road,
Kāne‘ohe, HI 96744, USA
@Phil_Robichaud
@deepthiw
@JoseServera