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Dear colleagues,
Apologies to those of you receiving cross-postings.
The following articles on Yangtze finless porpoise have recently been
published:
Vladimir V. Popov, Alexander Ya. Supin, Ding Wang, Kexiong Wang, Jianqiang
Xiao, and Songhai Li. 2005. Evoked-potential audiogram of the Yangtze
finless porpoise Neophocaena phocaenoides asiaeorientalis (L). J. Acoust.
Soc. Am. 117 (5): 2728-2731.
Songhai Li, Kexiong Wang, Ding Wang, and Tomonari Akamatsu. 2005.
Echolocation signals of the free-ranging Yangtze finless porpoise
(Neophocaena phocaenoides asiaeorientialis). J. Acoust. Soc. Am. 117 (5):
3288-3296.
Tomonari Akamatsu, Ding Wang, and Kexiong Wang. 2005. Off-axis sonar beam
pattern of free-ranging finless porpoises measured by a stereo pulse event
data logger. J. Acoust. Soc. Am. 117 (5): 3325-3330.
Tomonari Akamatsu, Ding Wang, Kexiong Wang, and Yasuhiko Naito. 2005.
Biosonar behaviour of free-ranging porpoises. Proc. R. Soc. B. 272(1565):
797-801.
ABSTRACT
Vladimir V. Popov, Alexander Ya. Supin, Ding Wang, Kexiong Wang, Jianqiang
Xiao, and Songhai Li. 2005. Evoked-potential audiogram of the Yangtze
finless porpoise Neophocaena phocaenoides asiaeorientalis (L).
Evoked-potential audiograms were obtained in two (one male and one female)
Yangtze finless porpoises, Neophocaena phocaenoides asiaseorientalis.
Sinusoidal amplitude-modulated 20-ms tone bursts were used as probes with
recording envelope-following evoked potentials. A frequency range of 8 to
152 kHz was investigated. The range of greatest sensitivity covered
frequencies from 45 to 139 kHz, and the lowest thresholds of 47.2 and 48.5
dB re: 1 uPa were found at a frequency of 54 kHz in the two subjects,
respectively. At lower frequencies, threshold increased with a rate of
around 14 dB/octave, and threshold steeply increased at 152 kHz.
Songhai Li, Kexiong Wang, Ding Wang, and Tomonari Akamatsu. 2005.
Echolocation signals of the free-ranging Yangtze finless porpoise
(Neophocaena phocaenoides asiaeorientialis).
This paper describes the high-frequency echolocation signals from
free-ranging Yangtze finless porpoise in the Tian-e-zhou Baiji National
Natural Reserve in Hubei Province, China. Signal analysis showed that the
Yangtze finless porpoise clicks are typical high-frequency narrow-band
(relative width of the frequency spectrum Q=6.6+/-1.56, N=548) ultrasonic
pulses. The peak frequencies of the typical clicks range from 87 to 145 kHz
with an average of 125+/-6.92 kHz. The durations range from 30 to 122 us
with an average of 68+/-14.12 us. The characteristics of the signals are
similar to those of other members of the Phocoenidae as well as the
distantly related delphinids, Cephalorhynchus spp. Comparison of these
signals to those of the baiji (Lipotes vexillifer), who occupies habitat
similar to that of the Yangtze finless porpoise, showed that the peak
frequencies of clicks produced by the Yangtze finless porpoise are
remarkably higher than those produced by the baiji. Differenc!
e in peak frequency between the two species is probably linked to the
different size of preferred prey fish. Clear double-pulse and multi-pulse
reverberation structures of clicks are noticed, and there is no indication
of any low-frequency (<70 kHz) components during the recording period.
Tomonari Akamatsu, Ding Wang, and Kexiong Wang. 2005. Off-axis sonar beam
pattern of free-ranging finless porpoises measured by a stereo pulse event
data logger.
The off-axis sonar beam patterns of eight free-ranging finless porpoises
were measured using attached data logger systems. The transmitted sound
pressure level at each beam angle was calculated from the animal?s body
angle, the water surface echo level, and the swimming depth. The beam
pattern of the off-axis signals between 45? and 115? (where 0? corresponds
to the on-axis direction) was nearly constant. The sound pressure level of
the off-axis signals reached 162 dB re 1 uPa peak-to-peak. The surface echo
level received at the animal was over 140 dB, much higher than the auditory
threshold level of small odontocetes. Finless porpoises are estimated to be
able to receive the surface echoes of off-axis signals even at 50-m depth.
Shallow water systems (less than 50-m depth) are the dominant habitat of
both oceanic and freshwater populations of this species. Surface echoes may
provide porpoises not only with diving depth information but also with
information about surface di!
rection and location of obstacles (including prey items) outside the
on-axis sector of the sonar beam.
Tomonari Akamatsu, Ding Wang, Kexiong Wang, and Yasuhiko Naito. 2005.
Biosonar behaviour of free-ranging porpoises.
Detecting objects in their paths is a fundamental perceptional function of
moving organisms. Potential risks and rewards, such as prey, predators,
conspecifics or non-biological obstacles, must be detected so that an
animal can modify its behaviour accordingly. However, to date few studies
have considered how animals in the wild focus their attention. Dolphins and
porpoises are known to actively use sonar or echolocation. A newly
developed miniature data logger attached to a porpoise allows for
individual recording of acoustical search efforts and inspection distance
based on echolocation. In this study, we analysed the biosonar behaviour of
eight free-ranging finless porpoises (Neophocaena phocaenoides) and
demonstrated that these animals inspect the area ahead of them before
swimming silently into it. The porpoises inspected distances up to 77m,
whereas their swimming distance without using sonar was less than 20m. The
inspection distance was long enough to ensure a wide s!
afety margin before facing real risks or rewards. Once a potential prey
item was detected, porpoises adjusted their inspection distance from the
remote target throughout their approach.
The articles are available in PDF format by contacting
Please do not request reprints from the mail list.
Best regards,
XIAO, Jianqiang
17:31:29 2005-5-17
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XIAO, Jianqiang
Institute of Hydrobiology
The Chinese Academy of Sciences
Wuhan, 430072
China
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