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59
TECHNOLOGY INNOVATION
MALE HUMPBACK WHALES (MEGAPTERA NOVAE-
ANGLIAE) (fi g. 1) produce “songs”—long, patterned
sequences of sounds—that are presumed to function
as a reproductive display on the breeding grounds (Payne and
McVay 1971; Winn and Winn 1978; Tyack 1981). Many preferred
breeding areas are conservation hot spots protected by marine
parks, and the whale-watching industry has fl ourished in those
sites (Hoyt 2001). Noise generated from whale-watching boat
traffi c can mask important aspects of whale communication. This
raises concerns about the potential infl uence of noise on repro-
ductive success and population growth. Gray whales may tempo-
rarily or permanently abandon critical areas because of excessive
exposure to boat noise (Bryant et al. 1984). Therefore, managers
in parks created to protect and conserve whales are often faced
with the task of managing noise-generating tourism activities,
especially in breeding areas.
Because whales are acoustic specialists (Richardson et al. 1995),
investigations can rely on listening to understand their social
system. Recent advances in passive acoustic technology allow
researchers to follow the movements of whales by locating and
tracking vocalizing individuals. By continuously sampling and
simultaneously following multiple whales, investigators can
describe the movements of cohorts of individuals. By comparing
whale tracks with the tracks and acoustic characteristics of human
activities, investigators can measure whale responses to human-
caused disturbance, such as an approaching vessel.
Figure 1. A humpback whale (Megaptera novaeangliae) exposes its
tail or fl uke, a common occurrence while singing, in Abrolhos Marine
National Park. Scientists use the unique black-and-white markings
of the underside of the fl uke to identify individuals. Brazilian Navy
facilities are visible on Santa Bárbara Island in the background.
Whale sound recording technology as
a tool for assessing the effects of boat
noise in a Brazilian marine park
Using passive acoustic technology,
researchers record the movements of whales,
assess the impacts of noise from boat tours, and
help refi ne tourism management
By Renata S. Sousa-Lima and Christopher W. Clark
COURTESY OF RENATA SOUSA-LIMA
Editor’s Note: You can hear whale song recordings and see a brief
video clip showing the movements of two whales before, during,
and after exposure to tourism boat noise, both products of this
study, on the Park Science Web site (http://www.nature.nps.gov/
ParkScience/index.cfm?ArticleID=270).
PARK SCIEN CE • VOLUME 26 • NUMBER 1 • SPRING 2009
In this study, we used passive acoustic technology to evaluate the
eff ects of boat traffi c on the spatial-acoustic behavior of vocally
active male humpback whales in the Abrolhos Marine National
Park, Brazil (fi g. 2); this park is situated in the main humpback
whale breeding grounds in the southwestern Atlantic Ocean (En-
gel 1996). Our specifi c objectives were (1) to determine the types
of singer responses to an approaching boat, and (2) to identify the
“distance of disturbance”—the distances to which avoidance (i.e.,
movement away from boat) and behavioral disruption (i.e., cessa-
tion of singing) are observed.
Methods
We deployed an array of four “pop-ups” (fi g. 3) programmed to
record continuously from 5 July to 4 October 2005 inside the area
of the Abrolhos Marine National Park in the northeastern part
of the Abrolhos Bank (16°40'–19°30'S). The whale sounds were
detected and located in the recordings using the software XBAT
(http://www.xbat.org) written in MATLAB (the MathWorks com-
puting language and interactive environment). We assigned each
located whale sound to a particular individual singer based on (1)
the unique repetition pattern of the sounds within the humpback
whale song and (2) the location of the sound in relation to other
located singers. We consolidated all located sounds from the
same singer within 90 seconds into a single median point loca-
tion and interpolated the sequences of such locations to yield an
acoustic track using a custom programming routine (ISRAT_LT
1.3.2, Urazghildiiev unpublished) also written in MATLAB.
We gave Global Positioning System (GPS) units to tourism boats
before they visited the park, and generated boat tracks from the
GPS locations in ISRAT_LT 1.3.2. We used tracks of whales and
boats to measure speed and boat-whale distances. We analyzed
the spatiotemporal patterns of the movements of singers and
boats to determine the orientation of each singer’s movement
in relation to a boat’s movement. Possible orientations included
away, toward, and neutral movement; neutral movement indi-
cated that the boat track was parallel to the whale track after the
closest point of approach between whale and boat.
We de fi ned treatment periods (pre-exposure, exposure, and
post-exposure) for each singer based on the distances between
singer and vessel. Pre-exposure was defi ned as the period before
the closest point of approach between whale and boat during
which distances were greater than 4.0 kilometers (2.5 mi). The
period considered “exposure” occurred while the distances
between whale and boat were less than 4.0 kilometers, which is a
documented mean for whale-boat distance shown to have caused
bowhead and humpback whales to respond to vessels (Rich-
ardson et al. 1985; Baker and Herman 1989). Post-exposure was
60
Figure 2. Investigators used passive acoustic technology to
document and analyze the effects of boat traffi c on the spatial-
acoustic behavior of vocally active male humpback whales in
Abrolhos National Marine Park. The polygons in the inset image
defi ne the park area.
COURTESY OF RENATA SOUSA-LIMA
Figure 3. “Pop-ups”—marine autonomous recording units
developed by the Bioacoustics Research Program at Cornell
University—are ready to be deployed at sea.
INSET:
COURTESY OF LANDSAT.ORG, GLOBAL
OBSERVATORY FO R ECOSYSTEM SERVI CES,
MICHIG AN STATE UNIVERSI TY
(HTTP://LAN DSAT.ORG)
61
TECHNOLOGY INNOVATION
defi ned as the period after the closest point of approach between
whale and boat during which distances were greater than 4.0
kilometers.
Results
We analyzed four tracks of a single tourism boat and 11 acousti-
cally tracked singers. Some singers moved away and stopped singing
as the boat approached their location (four out of nine or 44.5%);
others moved away but kept singing (fi ve out of nine or 55.5%).
The predominant movement of singers relative to the boat’s
closest point of approach was “away” (77.8%). Six of the nine
singers (66.7%) that moved away from the boat initiated move-
ment before 4.0 kilometers (2.5 mi). The proportions of time
devoted to movement away from, toward, and neutral to the boat
were similar during pre-exposure. However, an increase in the
proportion of time moving away occurred during the exposure,
which continued to be disproportional during post-exposure
(fi g. 4). We identifi ed two types of singer responses to the boat:
(1) displacement followed by cessation of vocal activity (44.5%)
and (2) displacement and continued vocal activity (55.5%). All
located singers in the sampled area were displaced as the boat
approached, and the ones that quit singing did not resume singing
for at least 20 minutes.
Discussion
All whales moved from their original positions as the boat ap-
proached. Direct observations of singers being approached by
boats in Abrolhos show that if they stopped singing, they invari-
ably also left the area. Thus, we interpret cessation of singing as
displacement.
Bejder et al. (2006) proposed that the individuals that are most
sensitive to boat approaches would abandon preferred areas
because of increased boat disturbance. Assuming this is true, only
the individuals less sensitive to boat disturbances would remain in
the area. The eff ect this selection for boat noise–habituated males
could have on the population structure is unknown; it could aff ect
Toward
Neutral
Away
Post-ExposureExposurePre-Exposure
28.6%
44.8%
26.7%
15.9%
15.8%
68.4% 41%
9%
50%
Figure 4. The pie graphs show the proportion of total time that the whales spent moving away from the boat (brown), neutral or not moving
(beige), or moving toward the boat (purple) during each treatment period. Pre-exposure was defi ned as the period before the closest point
of approach between whale and boat during which distances were greater than 4.0 kilometers (2.5 mi). The period considered “exposure”
occurred while the distances between whale and boat were less than 4.0 kilometers. Post-exposure was defi ned as the period after the
closest point of approach between whale and boat during which distances were greater than 4.0 kilometers.
Noise generated from whale-watching
boat traffi c can mask important aspects
of whale communication. This raises
concerns about the potential infl uence
of noise on reproductive success and
population growth.
PARK SCIEN CE • VOLUME 26 • NUMBER 1 • SPRING 2009
62
female choice and consequently the distribution of breeding suc-
cess among the males of this population. A primary management
concern is that whale habituation to boats could increase the
probability of fatal encounters with vessels.
The majority of the singers (77.8%) moved away from the boat
at the boat’s closest point of approach, suggesting avoidance, al-
though the most compelling evidence that singers avoid boats was
the direction of their movement. Almost 70% of singer movement
was away from the boat when the singer-boat distance was less
than 4.0 kilometers (2.5 mi). Vessel-singer distance also aff ected
swimming direction of humpbacks off Hawai’i (Frankel and Clark
1988) and Alaska (Baker and Herman 1989): Whales moved away
from approaching vessels. In our study, during the post-exposure
period, singers were still moving away from the boat, which sug-
gests a residual avoidance of the disturbance area.
Baker and Herman (1989) have observed boat avoidance orienta-
tion in humpback whales out to 8.0 kilometers (5.0 mi). The ma-
jority of singers in our study responded by swimming away from
the boat at distances greater than 4.0 kilometers (mean distance
of approximately 7.5 kilometers [4.7 mi]). Other studies from
boats and land-based platforms found that whales were disturbed
at closer ranges (<300 meters [984 ft]) (Watkins 1986; Corkeron
1995; Sousa-Lima et al. 2002; Morete 2007). While this could be a
refl ection of smaller sampling areas or specifi c close-range ana-
lytical designs, it could also be a bias toward less sensitive whales.
We have shown that the use of an acoustic array provides the
acoustic equivalent of a bird’s-eye view into cetacean behavior
and can be a cost-eff ective monitoring tool to evaluate marine
animal responses to human disturbances. Our results should aid
park managers in directing resources to keep noise disturbance at
low levels in the park, perhaps through expansion and enforce-
ment of regulatory measures such as the use of quieter engines,
speed regulation, and boat quantity limitation.
Park managers can use passive acoustic technology in a variety of
wildlife management scenarios. This technology will help docu-
ment and monitor wildlife distributions and responses to human
activities, especially in areas of low visibility, diffi cult access, at
night, or underwater. The U.S. National Park Service has begun
to use acoustic monitoring of protected areas (e.g., Glacier Bay
National Park), and its use as a diagnostic and regulatory tool for
park rangers and managers may increase as its benefi ts become
known.
Acknowledgments
We thank Stephen Morreale, Milo Richmond, and John Herman-
son for their suggestions; Lucas Goulart Collares, Bruna Mazoni
Guerra, and the Piloto crew for fi eld assistance; Eric Shannon,
Michelle Mathios, Jessica Musa, Caitlin Armstrong, and Roman
Lesko for data processing. The Instituto Baleia Jubarte and its
sponsor Petroleo Brasileiro S.A. (Petrobras), Abrolhos tourism
operators and boat owners, the Brazilian government (CAPES,
BEX 1523-01-5), Cornell Laboratory of Ornithology, and the
Canon National Parks Science Scholars Program provided fund-
ing and support.
References
Baker, C. S., and L. M. Herman. 1989. Behavioral responses of summering
humpback whales to vessel traffi c: Experimental and opportunistic
observations. Final Report NPS-NR-TRS-89-01. U.S. Department of the
Interior, National Park Service, Anchorage, Alaska, USA.
Bejder, L., A. Samuels, H. Whitehead, N. Gales, J. Mann, R. Connor,
M. Heithaus, J. Watson-Capps, C. Flaherty, and M. Krutzen. 2006.
Decline in relative abundance of bottlenose dolphins exposed to long-
term disturbance. Conservation Biology 20:1791–1798.
Our results should aid park managers in directing resources to keep noise
disturbance at low levels in the park, perhaps through expansion and enforcement
of regulatory measures such as the use of quieter engines, speed regulation, and boat
quantity limitation.
63
TECHNOLOGY INNOVATION
Bryant, P. J., C. M. Lafferty, and S. K. Lafferty. 1984. Reoccupation of
Laguna Guerrero Negro, Baja California, Mexico, by gray whales. Pages
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About the authors
Renata S. Sousa-Lima was a 2003 Canon Scholar from the
Department of Natural Resources and Bioacoustics Research
Program, Cornell University, and an associate researcher of the
Instituto Baleia Jubarte (Humpback Whale Institute), Brazil. She
completed her dissertation, “Acoustic ecology of humpback whales
(Megaptera novaeangliae) in the Abrolhos Marine National Park,
Brazil,” in 2007. Dr. Sousa-Lima currently is an FAPEMIG (Fundação
de Amparo à Pesquisa do Estado de Minas Gerais) postdoctoral
fellow at the Universidade Federal de Minas Gerais, Brazil, and can
be reached at renata.sousalima@icb.ufmg.br or RSL32@cornell.
edu.
Christopher W. Clark is the I. P. Johnson Director of the
Bioacoustics Research Program, Cornell Laboratory of Ornithology,
and a senior scientist of the Department of Neurobiology and
Behavior, Cornell University.
