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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