Dear colleagues,
We are pleased to announce the publication of two articles on St. Lawrence
Estuary beluga, one discussing their decline and potential causes, with an
updated analysis of carcass recovery rates up to 2019, and the other examining
impacts of underwater noise on communication space, with particular emphasis on
potential effects of communication masking on mother-calf acoustic contact.
Both are part of the Polar Research Special Issue "Beluga whales
(Delphinapterus leucas): Knowledge from the wild, human care and TEK”.
Lesage, V. 2021. The challenges of a small population exposed to multiple
anthropogenic stressors and a changing climate: the St. Lawrence Estuary
beluga. Polar Research 40, 5523. The article is open access and available here:
https://doi.org/10.33265/polar.v40.5523
<https://doi.org/10.33265/polar.v40.5523>
ABSTRACT: Until 2012, the St. Lawrence Estuary beluga population was considered
stable with about 1100 individuals. An abnormally high number of calves
reported dead that year triggered a population status reassessment. This review
article summarizes the findings from this reassessment and various studies
subsequent to it and provides an updated analysis of carcass recovery rates up
to 2019. The 2013 review indicated a decreased incidence of cancer in adults,
suggesting positive impacts from the regulation of toxic substances (e.g., PCBs
and PAHs). However, the review also revealed that the population initiated a
decline of ca. 1% per year in the early 2000s and had reached a size of ca. 900
individuals by 2012. This decline was accompanied by high inter-annual
variability in calf survival and pregnancy rates and by more frequent
peripartum complications among dead females. The change in population dynamics
coincided with a shift in the St. Lawrence ecosystem structure and warmer
environmental conditions, suggesting a link through effects on reproductive
success and adult female body condition. This was supported by the continued
high calf mortality after 2012 and a documented decline of fat reserves in
beluga blubber from 1998 to 2016. Other factors, such as the exposure to
chronic vessel noise, increasing whale-watching activities, high contaminant
levels and episodic harmful algal blooms, may also be contributing to the
long-term non-recovery and current decline of the population. The strong natal
philopatry and complex social system of the beluga likely increase its
vulnerability to extinction risk by limiting dispersal.
Vergara, V., Wood, J., Lesage, V., Ames, A., Mikus, MA., and Michaud, R. 2021.
Can you hear me? Impacts of underwater noise on communication space of adult,
sub-adult, and calf contact calls of endangered St. Lawrence belugas (D.
leucas). Polar Research 40, 5521. The article is open access and available
here: https://doi.org/10.33265/polar.v40.5521
<https://doi.org/10.33265/polar.v40.5521>
ABSTRACT: Noise and anthropogenic disturbances from vessel traffic are an
important threat to the recovery of the endangered St. Lawrence Estuary (SLE)
beluga population. The consequences of acoustic masking could be particularly
adverse in the case of critical vocalizations that maintain contact between
mothers and their dependent but mobile calves. This study models the
communication range of adults, sub-adults and newborn beluga contact calls in
the presence and absence of vessels in an important summering area for this
population. Ambient noise measurements, a composite beluga audiogram and
apparent source levels of adult/sub-adult and newborn calls, informed the
model. Apparent source levels were estimated from received levels of contact
calls produced by four individuals carrying digital acoustic tags in the SLE,
Canada, and from received levels of calls recorded from two adults and a
newborn calf at an aquarium, at known distances from a calibrated hydrophone.
The median communication ranges were over 18 times larger for SLE adult and
sub-adult calls than for newborn calls, with a 57 and 53% reduction in range in
the presence of vessel noise, respectively. For newborn calls, this results in
a median range of 170 m in vessel noise. These first estimates of the
communication range of beluga vocalizations with a known function suggest that
masking of the quiet calls of newborns by anthropogenic noise could impair
mother–calf contact.
Please feel free to contact us at [email protected] or
[email protected] if you have any questions.
Best Wishes,
Valeria Vergara, Ph.D.
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