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Revista de Biología Tropical, ISSN: 2215-2075, Vol. 71(S4): e57280, diciembre 2023 (Publicado Nov. 01, 2023)
Southern Hemisphere humpback whales (Megaptera novaeangliae)
(Artiodactyla: Balaenopteridae) singing activity at Caño Island Biological
Reserve, Costa Rica before, during, and after COVID-19 lockdowns
Laura J. May-Collado1, 2*; https://orcid.org/0000-0002-4790-9524
Sawyer Bottoms1; https://orcid.org/0000-0002-8821-7348
Grace Durant1; https://orcid.org/0000-0002-1896-3900
Jose David Palacios-Alfaro3; https://orcid.org/0000-0002-0315-094X
Juan Jose Alvarado4, 5, 6; https://orcid.org/0000-0002-2620-9115
1. Department of Biology, University of Vermont, Burlington, VT 05405, USA; sawyer.miller-bottoms@uvm.edu,
grace.durant@uvm.edu
2. Smithsonian Tropical Research Institute, Panama, Panama; lmaycoll@uvm.edu (*corresponding author)
3. Fundación Panacetacea, St Paul Minnesota, 55118, USA; pala1611@gmail.com
4. Escuela de Biología, Universidad de Costa Rica, San José, Costa Rica, juan.alvarado@ucr.ac.cr
5. Centro de Investigación en Ciencias del Mar y Limología (CIMAR), Universidad de Costa Rica, San José, Costa Rica.
6. Ecología Tropical (CIBET), Universidad de Costa Rica, San José, Costa Rica.
Received 21-IX-2022. Corrected 13-II-2023. Accepted 11-IV-2023.
ABSTRACT
Introduction: Boat traffic is recognized as a major contributor of underwater noise. Increasing presence of boats
in coastal habitats is predicted to have important repercussions on the communication of marine mammals. In
Costa Rica, the waters of the Caño Island Biological Reserve are an important breeding area for humpback whales
from the Breeding-Stock G (BSG). Their predicted and abundant presence has fueled the development of whale
watching activities as an important component of the local economy, and while the country has norms of conduct
for this activity, whales often interact with multiple boats at the same time. The lockdowns associated with the
COVID-19 pandemic provided a unique opportunity to study the potential impacts of noise associated with boat
traffic on the singing activity of humpback whales.
Objective: Determine whether noise levels and boat acoustic presence around Caño Island Biological Reserve
changed during the COVID-19 lockdowns, and if it did, what is the impact on song detection of BSG humpback
whales.
Methods: Acoustic recordings were made using a bottom-mounted autonomous underwater recorder for 30 days
in September 2019, 2020, and 2021, resulting in a total recording effort of 480 hours.
Results: Our results show that broadband underwater noise levels (dBRMS) during pre-lockdown were signifi-
cantly higher, particularly at frequencies below 1kHz, than during and post-lockdown. This is likely due to a
decrease in the proportion of boat acoustic presence during the lockdown. Although the proportion of whale
songs detected did not vary among years, whale songs were detected similarly throughout the day during the
lockdown, compared to pre-and-post lockdown where the proportion of whale song presence decreased during
hours when more boats were present.
Conclusions: This study shows a clear change in underwater noise levels during the COVID-19 lockdown, likely
due to a decrease in boat presence. The study also highlights the potential impact of noise associated with boat
traffic on humpback whale singing activity. The results of this study can inform the Conservation Areas of Osa
https://doi.org/10.15517/rev.biol.trop..v71iS4.57280
SUPPLEMENT • WHALES
2Revista de Biología Tropical, ISSN: 2215-2075 Vol. 71(S4): e57280, diciembre 2023 (Publicado Nov. 01, 2023)
INTRODUCTION
Boat traffic (i.e., ecotourism, personal use,
fishing, water-taxis) is increasing rapidly in
many coastal environments contributing to an
increasingly noisier ocean (Erbe et al., 2019).
Concerns about the potential repercussions
of underwater noise impacts on whale com-
munication are increasing among scientists
worldwide (e.g., Cholewiak et al., 2018, Erbe et
al., 2019). High noise levels can reduce the dis-
tance at which these animals can communicate
(e.g., Cholewiak et al., 2018, Rey-Barquero et
al., Laude et al., 2022) and can interrupt bio-
logically important behaviors (e.g., Amrein et
al., 2020; Sprogis et al., 2020). For example,
Rey-Barquero et al., (2021) developed a model
based on empirical data that showed that even
in the presence of a single whale-watching
boat, humpback whale, Megaptera novaean-
gliae (Borowski, 1781) song communication
could be reduced by as much as 63 %. Another
study found whale-watching activities to be
one of the factors contributing to a decrease in
communication space, with humpback whales
experiencing masking levels of 80% or more
(ACOSA) in charge of managing Caño Island Biological Reserve, to develop and implement mitigation measures
to regulate underwater anthropogenic noise associated with tour boats.
Key words: ambient noise levels; boat traffic; whale-watching; tourism; bioacoustics.
RESUMEN
Actividad de canto de las ballenas jorobadas (Megaptera novaeangliae) (Artiodactyla: Balaenopteridae) del
hemisferio sur en la Reserva Biológica de la Isla del Caño, Costa Rica, antes, durante
y después de los cierres asociados a la pandemia de COVID-19
Introducción: Se reconoce que el tráfico de embarcaciones es uno de los principales contribuyentes al ruido
marino. Se predice que la creciente presencia de barcos en los hábitats costeros tendrá importantes repercusiones
en la comunicación de los mamíferos marinos. En Costa Rica, las aguas de la Reserva Biológica Isla del Caño son
un hábitat reproductivo importante para las ballenas jorobadas de la población reproductiva G (BSG). Su presen-
cia ha impulsado el desarrollo de las actividades de observación comercial de ballenas, el cual es un componente
importante de la economía local. Aunque el país tiene normas de conducta para esta actividad, las ballenas a
menudo interactúan con múltiples barcos turísticos al mismo tiempo. Los cierres y limitaciones de movilización
de botes asociados a la pandemia de COVID-19 brindan una oportunidad para estudiar el impacto potencial del
ruido asociado al tráfico de embarcaciones en la actividad de canto de las ballenas jorobadas.
Objetivo: Determinar si los niveles de ruido ambiental bajo el agua y la presencia de botes cambiaron antes,
durante y después de los cierres y cuarentena por COVID-19, y si estos cambios influyen en la detección de cantos
de machos de ballenas jorobadas.
Métodos: las grabaciones acústicas se realizaron con una grabadora autónoma montada en el fondo marino
durante 30 días en septiembre de 2019, 2020 y 2021, resultando en un esfuerzo de grabación de 480 horas.
Resultados: Nuestros resultados muestran que los niveles de ruido ambiental (dBRMS) antes del cierre (2019)
fueron significativamente más altos, particularmente a frecuencias bajas (<1kHz), que durante y después de los
cierres asociados a la pandemia de COVID-19. Es probable que esto se deba a una reducción en la presencia de
embarcaciones durante el cierre. Aunque la detección de cantos de ballenas jorobadas no varió entre años, durante
la cuarentena se detectaron los cantos de ballenas de forma uniforme durante el día, mientras que antes y después
de la cuarentena se notó un decrecimiento en la proporción de cantos a horas donde hay más detección de botes
presentes.
Conclusiones: Este estudio muestra un cambio claro en los niveles de ruido ambiental durante el cierre de
COVID-19, probablemente debido a una disminución en la presencia de embarcaciones. El estudio también
muestra el potencial impacto del ruido asociado al tráfico de embarcaciones en la actividad del canto de las
ballenas jorobadas. Los resultados de este estudio pueden informar al Área de Conservación de Osa (ACOSA), la
cual está a cargo de la Reserva Biológica Isla del Caño, a desarrollar e implementar medidas que regulen el ruido
antropogénico bajo el agua asociado a tráfico de botes turísticos.
Palabras clave: ruido ambiental; tráfico de botes; observación de ballenas; turismo; bioacoustica.
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Revista de Biología Tropical, ISSN: 2215-2075, Vol. 71(S4): e57280, diciembre 2023 (Publicado Nov. 01, 2023)
(Cholewiak et al., 2018). These studies show the
potential negative impact of noise associated
with boat traffic, particularly that of activities
that directly target these animals, such as whale
watching activities.
Whale-watching is a major catalyst of the
local economy in Latin America (Tambutti
& Gómez, 2020). The most recent review of
the state of whale watching in Latin America
is by Hoyt and Iñiguez (2008). The authors
find that between 1996 and 2006, boat-based
whale watching activities in the region grew
at a rate three times higher than the rate of
world tourism and five times higher than the
rate of all Latin American tourism over the
same period. Although many countries have
adopted whale watching guidelines, compliance
and enforcement remains limited (Gagne et al.,
2022). As a result, whales might be exposed to
noisy soundscapes.
In March 2020, the COVID-19 pandemic
led to a global and national lockdown in Costa
Rica to limit the spread of the virus. Widespread
mandatory lockdowns and stay-at-home orders
severely limited human mobility and activities
in land and in the ocean. Costa Rica’s economy
shrank by 4.1% in 2020 as a consequence of
these measures, and among the factors driving
this trend was the sharp drop in tourism (Eco-
nomic Survey of Latin America and the Carib-
bean, ECLAC, 2021). According to the CEIC
Global Economy Database (2022), the number
of air transported passengers dropped from
2,033,146 to 455,830 passengers. Worldwide,
this drop in human mobility resulted in an
increase in animal communication ranges; for
urban songbirds, their communication range
doubled in some places (Derryberry et al.,
2020) and for dolphin and fish it increased to
up to 65 % (Pine et al., 2021).
Male humpback whales are highly vocal
animals that perform acoustic displays pri-
marily during the breeding season (Herman
et.al., 2013). The South Pacific waters off the
coast of Costa Rica, and particularly the north
and east side of Caño Island, are an important
breeding area for Southeastern Pacific hump-
back whales, also known as the International
Whaling Commission, designated Breeding
Stock G (BSG) (Palacios-Alfaro et al., 2012;
Rasmussen et al., 2007) as well as for whales
from the “Central America” distinct population
segment (DPS) (Bettridge et al., 2015). The
BSG whales observed in Costa Rica migrate
from feeding areas off the Antarctic Penin-
sula and the Fuegian Archipelago in Chile
(Acevedo et al., 2017; Rasmussen et al., 2007).
Multiyear boat surveys in this area indicate
that BSG whales are particularly abundant in
September (Palacios-Alfaro et al., 2012), and
for this reason coastal communities in the area
celebrate a whale festival during this month
(Palacios-Alfaro, personal communication, 1
september 2022).
A previous study using passive acoustic
monitoring data near Caño island found that
male song activity occurred throughout the day,
with a drop in singing activity during the morn-
ing hours, suggesting a potential response to
whale watching tour boats presence (Chereskin
et al., 2019). In other breeding areas in Brazil,
increased boat traffic was shown to have a neg-
ative effect on humpback whale singing activity,
with whales singing less when the number of
boats increased (Sousa-Lima & Clark, 2008). In
a recent study, Laute et al. (2022) found that on
Icelandic foraging areas during the COVID-19
pandemic, whale watching trips were reduced
by 68.6 %, and humpback whale call detection
increased by nearly twofold. In this study we
examine whether noise levels and boat acous-
tic presence around Caño Island Biological
Reserve changed during the COVID-19 lock-
downs, and if it did, how the detection of BSG
humpback whale song was impacted.
MATERIALS AND METHODS
Study Area: This study took place at Caño
Island Biological Reserve, 16 km northeast off
the Osa Peninsula in the south Pacific coast of
Costa Rica. This reserve protects approximately
58 km2 of marine habitat around the island
(Executive Decree 20790-MIRENEM, 1991).
An autonomous underwater recorder was
deployed in a location at the northeast side of
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the island called El Jardin (8.719 N/-83.863W,
Fig. 1) at a depth of 25 m. This location is
approximately 0.8 km from the island and is
characterized by a sandy bottom (Chereskin
et al., 2019). This area of the island has been
highlighted by previous studies as an important
reproductive habitat for BSG humpback whales
(e.g., Rasmussen et al., 2007; Palacios-Alfaro et
al., 2012). The island is also a tourist attraction
with tour boats arriving to the island through-
out the day to observe whales and dolphins,
snorkel, and scuba dive.
Data Collection: An autonomous under-
water recorder, a Soundtrap model 300 SD
(Ocean Instruments; frequency range 20 Hz-150
kHz ±3dB; self-noise of less than sea-state in
the bandwidth 100 Hz-2 kHz, and sensitivity of
-203 dB re V/µPa) was deployed in El Jardin for
the entire month of September 2019, 2020, and
2021. The recorder was programmed to record
the soundscape at a sampling rate of 48 kHz
for five minutes every 30 minutes in 2019, and
for 15 minutes every 60 minutes in 2020 and
2021, resulting in a total of 480 hours record-
ing effort. For this study, we only analyzed the
first five minutes of every hour for each year,
resulting in a total of 180 hours analyzed. These
5-min files were uploaded to RFCx ARBIMON
(Rainforest Connection, 2020) for cataloguing
and spectral inspection for presence/absence
of whale songs and boats. The proportion of
acoustic files with song and boat presence was
calculated by dividing the number of 5-min
files with whale songs and boats by the total
number of 5-min files per year and time of day.
Fig. 1. Location of Caño Island Biological Reserve off the Osa Peninsula in the South Pacific of Costa Rica. The figure also
shows a cartoon of a straight-line from Costa Rica towards the feeding areas off the Antarctica Peninsula and the Fuegian
Archipelago in Chile to Caño Island, Costa Rica. The black star represents the deployment site of the autonomous underwater
recorder.
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Revista de Biología Tropical, ISSN: 2215-2075, Vol. 71(S4): e57280, diciembre 2023 (Publicado Nov. 01, 2023)
Ambient Noise Levels: To measure broad-
band ambient noise levels we used the software
dBWav from Marshall-Day Acoustics (https://
www.marshallday.com) which is tailored for
Ocean Instrument Soundtrap hydrophones.
Upon calibration following Ocean Instruments
instructions, the first five minutes of every hour
were selected manually. Manual selection was
done because dBWav does not automatically
select the region of interest. We selected a sub-
sample of days for this part of the data analysis
including the following days for each year: 4,
7, 10, 13, 16, 19, 22, 25, and 28. The average
root-mean-square (RMSdB) was then generated
for each 1/3 octave bands ranging from 12.5 Hz
to 10 kHz.
Statistical analysis: The statistical software
SPSS 25 (IBM, 2017) was used for summary
statistics and statistical analyses. An ANOVA
test for multiple independent variables (n-way)
was used to study the effect of year (pre, during,
and post lockdown), time of day (hour), and 1/3
octave frequency bands on noise levels (RMSdB).
Broadband noise levels were compared among
years using a non-parametric Kruskal-Wallis’
test. The 1/3 octave bands were grouped into
two categories: below and above 1kHz frequen-
cy categories. Below 1 kHz included bands from
12.5 to 800 Hz and above 1 kHz bands from 1
to 10 kHz. A Kruskal-Wallis test was also used
to assess if there are differences in these two fre-
quency categories among years. A Chi-Square
one sample test for goodness of fit was used
to compare the proportion of recordings with
whale song and boat presence per year. Finally,
the proportion of noise levels, whale song, and
boat presence were plotted against time of day
using a smoothing spline with a bootstrap con-
fidence of fit using a lambda of 0.05 to look for
diel patterns in ambient noise levels and whale
song and boat presence within each year.
RESULTS
Ambient Noise Levels: The results from
the ANOVA analysis suggest that year (F
=1610.5, df=2, p<0.001), time of day (hour)
(F=4.8, df=23, p<0.001), 1/3 octave frequency
bands (F=369.8, df=27, p <0.001), and the
interactions between year*time of day (F=9.6,
df=46, p <0.001) and year*1/3 octave frequency
bands (F=176.7, df=52, p <0.001) influenced
the variation in ambient noise levels. Broad-
band ambient noise levels varied significantly
among years (Kruskal-Wallis=876.06; df=2, p
<0.001, Table 1, Fig. 2A, Fig. 2B). In general,
ambient noise levels were higher in pre-lock-
down than during and post-lockdown (Table
1, Fig. 2A) and these differences among years
were maintained throughout the day (Fig. 2B).
When accounting for frequency categories
Tabl e 1
Summary statistics of ambient noise levels (in dB) and the proportion of whale song and boat presence in pre-lockdown,
during lockdown, and post-lockdown at Caño Island Biological Reserve.
Pre-lockdown (2019) During lockdown (2020) Post-lockdown (2021)
Ambient noise levels (dB)
Mean±SD 99.8 ± 15.3 93.0 ± 11.6 92.0 ± 11.0
Coefficient of Variation (CV) 15.3 12.5 11.8
Range (minimum-maximum) 63.9 –- 134 63.7 –- 127.4 62.1 –- 126.8
Acoustic boat presence
Mean±SD 0.08 ± 0.13 0.03 ± 0.06 0.04 ± 0.09
Coefficient of Variation (CV) 152.8 169.6 193.9
Range (minimum-maximum) 0 – 0.44 0 – 0.22 0 – 0.30
Acoustic whale song presence
Mean±SD 0.98 ± 0.02 0.99 ± 0.01 0.97 ± 0.04
Coefficient of Variation (CV) 2.0 0.8 4.2
Range (minimum-maximum) 0.93 – 1 0.96 – 1 0.86 – 1
6Revista de Biología Tropical, ISSN: 2215-2075 Vol. 71(S4): e57280, diciembre 2023 (Publicado Nov. 01, 2023)
Fig. 2. A. Broadband ambient noise (RMSdB) levels by year. B. Broadband ambient noise levels (RMSdB) by time of day. C.
Broadband ambient noise levels (RMSdB) by year and frequency category. Broadband noise levels measured as the average
root-mean-square (RMSdB) (a) by year and (b) time of day, in blue pre-lockdown (2019), in red during lockdown (2020) and
in green post-lockdown (2021), and by (c) 1/3 octave frequency bands grouped into two categories below 1 kHz in red (12.5
to 800 Hz) and above 1 kHz in blue (1-10 kHz) and year, at Caño Island Biological Reserve, Costa Rica. The box plots display
median, first and third quartiles, and maximum and lower values (excluding outliers) and the line plot uses a smoothing
spline and bootstrap confidences of fit with a lambda of 0.05.
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Revista de Biología Tropical, ISSN: 2215-2075, Vol. 71(S4): e57280, diciembre 2023 (Publicado Nov. 01, 2023)
above and below 1 kHz we find significant
differences among years. Ambient noise lev-
els below 1 kHz were significantly higher in
pre-lockdown (Kruskal-Wallis=1138.5; df=2,
p <0.001, Fig. 2C) while ambient noise levels
above 1 kHz were significantly higher during
and in post-lockdown (Kruskal-Wallis=465.5;
df=2, p <0.001, Fig. 2C).
Acoustic presence of whale songs and
boats: A total of 2 058 5-min per hour files
were used for this analysis (2019 = 695 files,
2020 = 643 files, 2021 = 720 files). Of these, a
total of 2 028 5-min files had an acoustic pres-
ence of whale song (2019 = 686 files, 2020 =
642 files, 2021 = 700 files) and 117 5-min files
contained sounds of passing boats (2019 =
60 files, 2020 = 22 files, 2021 = 35 files). The
proportion of 5-min files with boats passing by
was significantly lower during lockdown than
in pre-lockdown and post-lockdown (χ2=61,
df=2, p =0.003, Table 1). Interestingly, the diel
acoustic presence of boats across years fol-
lowed a similar pattern, with a peak in presence
between 9 a.m. and noon for all years (Fig. 3A).
No significant differences (p >0.05) were found
in the proportion of 5-min files with whale
songs across years, but pre-lockdown and post-
lockdown years showed the greatest reduction
in the proportion of files with whale songs com-
pared to during the lockdown (Table 1, Fig. 3B).
In addition, we found differences in diel pat-
terns of the proportion of whale song presence
among years. During pre-lockdown, the high-
est proportion of recordings with whale songs
occurred at midnight and around 2 p.m. Dur-
ing the lockdown, the presence of whale songs
was almost constant throughout the day, with a
slight decrease between 9 a.m. and 2 p.m., and
in post-lockdown a sharper decrease in whale
song presence occurs approximately between 5
a.m. and 6 p.m., with the lowest proportion of
whale song presence occurring between 10 a.m.
and noon (Fig. 3B).
DISCUSSION
This study shows that underwater ambient
noise levels and boat presence changed between
pre-lockdown, during lockdown, and post-
lockdown periods around Caño Island Bio-
logical Reserve. The year before the COVID-19
pandemic had the highest mean underwa-
ter noise levels, particularly at low frequency
below 1 kHz, and a higher proportion of boat
presence. Although the proportion of whale
song presence did not vary significantly among
years, but we did observe a decrease in the
proportion of acoustic files with whale songs
during pre-and-post-lockdown. We also found
differences in the diel pattern of song presence
by time of day among years, suggesting a poten-
tial impact of tour-boat traffic in the area.
Boat traffic and shipping activities are the
most dominant sources of underwater noise
at low frequency (Southall et al., 2017). Dur-
ing the COVID-19 pandemic these activities
were significantly reduced due to a slowdown
of the global trade activity in order to mitigate
and minimize the spread of the virus (Ryan
et al., 2021; Thompson & Barclay 2020). This
decrease in low-frequency underwater noise
levels resulted in a potential increase in animal
communication ranges during the COVID-
19 lockdowns. For example, in New Zealand,
underwater ambient noise levels dropped
nearly threefold, resulting in an increased in
dolphin and fish communication ranges to up
to 65 % (Pine et al., 2021), while in Iceland a
reduction of whale watching trips resulted in a
twofold increase in humpback whale call (Laute
et al., 2022), and a similar increase in dolphin
whistle detection rates were found in Panama
(Gagne et al., 2022).
Caño Island Biological Reserve is an
important breeding area for humpback whales
(Rasmussen et al., 2007). Therefore, it is not
surprising that their overall presence did not
change between periods. However, Caño Island
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Fig. 3. Diel song detection of BSG humpback whale songs (a) and boat sounds (b) measured as the proportion of 5-min
files per hour with songs and boat sounds during pre-lockdown (2019 in blue), during lockdown, (2020 in red) and post-
lockdown (2021 in green) at Caño Island Biological Reserve, Costa Rica. These figures were done using a smoothing spline
and bootstrap confidences of fit (light read and blue colors) with a lambda of 0.05. To facilitate visualization of the data, notice
that scales for the proportion of boats and whale song detections are different.
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Revista de Biología Tropical, ISSN: 2215-2075, Vol. 71(S4): e57280, diciembre 2023 (Publicado Nov. 01, 2023)
Biological Reserve is also an important tourist
destination, and while whales are not the pri-
mary target for all tour activities, boat presence
is high in the area (Chereskin et al., 2019). A
previous study showed that in September at
Caño Island, BSG humpback whale singing
activity happens primarily at nighttime hours
(Chereskin et al., 2019). Similar diel singing
activity patterns have been described in other
humpback whale populations and appears to
be widespread (e.g., Cholewiak 2008; Homfeldt
et al., 2022). However, in this study we found
that during the COVID-19 lockdown, the pro-
portion of whale song presence was similar
throughout the day (i.e., Fig. 3B). This suggests
that in ‘normal’ times tour-boats might be
reducing whale singing activity during the day,
leading to higher rates during nighttime hours.
For example, we observed a decrease in the
proportion of whale song detections when boat
presence increased during the day, particularly
in pre-and-post-lockdown years. A high pres-
ence of tour-boats could lead to signal masking,
which can lower the proportion of time that
whale songs are detected by passive acoustic
monitoring sensors, and similarly impacting
detection among whales. Alternatively, whales
may invest less in singing when there is a high
presence of boats (and associated noise) and
invest more time in singing at nighttime hours
when boat presence is low (e.g., Parks et al.,
2014). Such decision-making tradeoffs have
been shown in humpback whales off the Oga-
sawara Islands in south Tokyo, where whales
stopped singing when boats were nearby (Tsujii
et al., 2018), and in humpback whales from the
Abrolhos National Marine Park in Brazil, where
humpback whales sang less when the number
of boats increased (Sousa-Lima & Clark 2008).
The function of humpback whale song
continues to be a subject of debate. Songs have
been proposed to function as a reproductive
display, by which males compete among them-
selves and attract potential mates (Herman
2017, Garland & McGregor 2020; Whitten
2019). That these songs can be masked by the
underwater noise from human activities or
that whales stop their acoustic displays when
there is a high presence of boats is of concern.
The high proportion of acoustic files with
whale songs during the COVID-19 lockdown
suggests that whales have the potential to sing
similarly throughout the day, but nighttime is
likely the most efficient time to sing when boat
traffic is high during the day, and highlights the
potential impact boat traffic can have in their
reproductive displays (i.e., males singing less)
(Sousa-Lima & Clark 2008; Tsujii et al., 2018,)
and habitat use (i.e., changing behavioral activi-
ties) (Sprogis et al., 2020).
As lockdown restrictions are lifted, tour
boat presence is expected to return to normal
at Caño Island. This study shows the potential
impacts of unregulated tour boat presence
on this important reproductive environment.
These impacts are an important consideration
for mitigation efforts and government invest-
ment in the enforcement of whale-watching
regulations, as well as in the design and imple-
mentation of measures to regulate anthropo-
genic noise levels in this protected area.
Ethical statement: the authors declare that
they all agree with this publication and made
significant contributions; that there is no con-
flict of interest of any kind; and that we fol-
lowed all pertinent ethical and legal procedures
and requirements. All financial sources are fully
and clearly stated in the acknowledgments sec-
tion. A signed document has been filed in the
journal archives.
Author Contribution: LJMC conceptual-
ized the study, collected data in the field and
the lab, coordinated data collection, performed
data analysis, interpreted the data, and drafted
and revised the manuscript. SB generated noise
level data, and contributed to the drafting of the
manuscript. GD, generated presence-absence
data, and contributed to the drafting of the
manuscript. JDPA and JJA collected data in the
field, recovered and deployed soundtraps, and
contributed to the drafting of the manuscript.
10 Revista de Biología Tropical, ISSN: 2215-2075 Vol. 71(S4): e57280, diciembre 2023 (Publicado Nov. 01, 2023)
ACKNOWLEDGMENTS
We thank the University of Costa Rica and
University of Vermont for funding this study.
Data was collected under the research permit
number ACOSA 60-SINAC-ACOSA-DASP-
PI—R-060 2019 to 2022. We also thank Kristin
Rasmussen and two anonymous reviewers for
their feedback, edits, and suggestions.
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