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This study by Breed et al. (2024) investigates the This study by Breed et al. (2024) investigates the longevity of Balaenid whales, focusing on the southern right whale (SRW, Eubalaena australis) and the North Atlantic right whale (NARW, Eubalaena glacialis). By analyzing over 40 years of mark-recapture data, the authors estimate life spans and survival patterns, revealing that extreme longevity (exceeding 130 years) is likely the norm rather than the exception in Balaenid whales, challenging previously accepted maximum life spans of 70–75 years. The study also highlights the impact of anthropogenic factors, particularly industrial whaling, on the significantly reduced life span of the endangered NARW.
Key Findings
Southern right whales (SRWs) have a median life span of approximately 73.4 years, with 10% of individuals surviving beyond 131.8 years.
North Atlantic right whales (NARWs) have a median life span of only 22.3 years, with 10% living past 47.2 years—considerably shorter than SRWs.
The reduced NARW life span is attributed to anthropogenic mortality factors, including ship strikes and entanglements, not intrinsic biological differences.
The study uses survival function modeling, bypassing traditional aging methods that rely on lethal sampling and growth layer counts, which tend to underestimate longevity.
Evidence from other whales, especially bowhead whales, supports the hypothesis that extreme longevity is widespread among Balaenids and possibly other large cetaceans.
Background and Context
Early longevity estimates in whales, such as blue and fin whales, came from counting annual growth layers in ear plugs, revealing ages up to 110–114 years.
Bowhead whales have been documented to live over 150 years, with some individuals estimated at 211 years based on aspartic acid racemization (AAR) and corroborating archaeological evidence (e.g., embedded antique harpoon tips).
Longevity estimates from traditional methods are biased low due to:
Difficulty in counting growth layers in very old whales due to tissue remodeling.
Removal of older age classes from populations by industrial whaling.
The need for lethal sampling to obtain age data, which is rarely possible in protected species.
The relation between body size and longevity supports the potential for extreme longevity in large whales, although bowhead whales exceed predictions from terrestrial mammal models.
Methodology
Data Sources:
SRW mark-recapture data from South Africa (1979–2021), including 2476 unique females, of which 139 had known birth years.
NARW mark-recapture data from the North Atlantic (1974–2020), including 328 unique females, of which 205 had known birth years.
Survival Models:
Ten parametric survival models were fitted, including Gompertz, Weibull, Logistic, and Exponential mortality functions with adjustments (Makeham and bathtub).
Models were fit using Bayesian inference with the R package BaSTA, which accounts for left truncation (unknown birth years) and right censoring (individuals surviving past the study period).
Model selection was based on Deviance Information Criterion (DIC).
Validation:
Simulated datasets, generated from fitted model parameters, were used to test for bias and accuracy.
Models accurately recovered survival parameters with minimal bias.
Estimating Reproductive Output:
The total number of calves produced by females was estimated by integrating survival curves and applying calving intervals ranging from 3 to 7 years.
Results
Parameter Southern Right Whale (SRW) North Atlantic Right Whale (NARW)
Median life span (years) 73.4 (95% CI [60.0, 88.3]) 22.3 (95% CI [19.7, 25.1])
10% survive past (years) 131.8 (95% CI [110.9, 159.3]) 47.2 (95% CI [43.0, 53.3])
Annual mortality hazard (age 5) ~0.5% 2.56%
Maximum life span potential >130 years Shortened due to anthropogenic factors
**SRW survival best fits an unmodified Gompertz model; NARW fits a Gompertz model with
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