One of the most important challenges researchers and managers confront in conservation ecology is predicting a population's response to sub-lethal stressors. Such predictions have been particularly ...elusive when assessing responses of large marine mammals to past anthropogenic pressures. Recently developed techniques involving baleen whale earplugs combine age estimates with cortisol measurements to assess spatial and temporal stress/stressor relationships. Here we show a relationship between baseline-corrected cortisol levels and corresponding whaling counts of fin, humpback, and blue whales in the Northern Hemisphere spanning the 20th century. We also model the impact of alternative demographic and environmental factors and determine that increased anomalies of sea surface temperature over a 46-year mean (1970-2016) were positively associated with cortisol levels. While industrial whaling can deplete populations by direct harvest, our data underscore a widespread stress response in baleen whales that is peripheral to whaling activities or associated with other anthropogenic change.
We quantified the relative influence of maternal fidelity to feeding grounds and natal fidelity to breeding grounds on the population structure of humpback whales Megaptera novaeangliae based on an ...ocean-wide survey of mitochondrial (mt) DNA diversity in the North Pacific. For 2193 biopsy samples collected from whales in 10 feeding regions and 8 breeding regions during the winter and summer of 2004 to 2006, we first used microsatellite genotyping (average, 9.5 loci) to identify replicate samples. From sequences of the mtDNA control region (500 bp) we identified 28 unique haplotypes from 30 variable sites. Haplotype frequencies differed markedly among feeding regions (overall F
ST = 0.121, ΦST = 0.178, p < 0.0001), supporting previous evidence of strong maternal fidelity. Haplotype frequencies also differed markedly among breeding regions (overall F
ST = 0.093, ΦST = 0.106, p < 0.0001), providing evidence of strong natal fidelity. Although sex-biased dispersal was not evident, differentiation of microsatellite allele frequencies was weak compared to differentiation of mtDNA haplotypes, suggesting male-biased gene flow. Feeding and breeding regions showed significant differences in haplotype frequencies, even for regions known to be strongly connected by patterns of individual migration. Thus, the influence of migratory fidelity seems to operate somewhat independently on feeding and breeding grounds over an evolutionary time scale. This results in a complex population structure and the potential to define multiple units to conserve in either seasonal habitat.
•Testosterone concentrations peak during January–February.•Lowest testosterone concentrations are observed June–September.•Testosterone concentrations decrease through the breeding ...season.•Testosterone concentrations peak in males from 8 to 25 years of age.•Testosterone concentrations in blubber and skin are not correlated.
Understanding reproductive profiles and timing of reproductive events is essential in the management and conservation of humpback whales (Megaptera novaeangliae).
Yet compared to other parameters and life history traits, such as abundance, migratory trends, reproductive rates, behavior and communication, relatively little is known about variations in reproductive physiology, especially in males. Here, an enzyme immunoassay (EIA) for testosterone was validated for use in biopsy samples from male humpback whales. Analyses were conducted on 277 North Pacific male humpback whale blubber samples, including 268 non-calves and 9 calves that were collected in the Hawaiian breeding grounds and the Southeast Alaskan feeding grounds from 2004 to 2006. Testosterone concentrations (ng/g) were significantly different between non-calves sampled in Hawaii (n = 182) and Alaska (n = 86, p < 0.05) with peak testosterone concentrations occurring in the winter (January–March) and the lowest concentrations occurring in the summer (June–September). Fall and spring showed increasing and decreasing trends in testosterone concentrations, respectively. Blubber testosterone concentrations in non-calves and calves sampled in Alaska were not significantly different. Blubber and skin from the same individual biopsies (n = 37) were also compared, with blubber having significantly higher testosterone concentrations (p < 0.05) than skin samples. We found variability in testosterone concentration with age, suggesting that male humpbacks reach peak lifetime testosterone concentrations in the breeding grounds around age 8–25 years. The testosterone profile of male humpback whales follows a predictable pattern for capital breeders, where testosterone begins to increase prior to the breeding season, stimulating the onset of spermatogenesis. Incorporation of reproductive hormonal profiles into our overall understanding of humpback whale physiology will shed additional light on the timing of reproduction and overall health of the recently delisted Hawaii distinct population segment (DPS).
Acoustically adept species in the marine environment have to contend with complex and highly variable soundscapes. In the ocean today, sounds from human sources contribute substantially to the ...underwater acoustic environment. We used a 4-element hydrophone array in Glacier Bay National Park to (1) identify primary drivers of ambient sound in this region, (2) investigate whether humpback whales Megaptera novaeangliae exhibit a Lombard response in response to ambient noise, and (3) investigate whether humpback whales adjust their calling activity in response to naturally occurring and vessel-generated sounds. We found that cruise ships and tour boats, roaring harbor seals Phoca vitulina, and weather events were primary drivers of ambient sound levels, and that they varied both seasonally and diurnally. As ambient sound levels increased, humpback whales responded by increasing the source levels of their calls (non-song vocalizations) by 0.81 dB (95% CI = 0.79–0.90) for every 1 dB increase in ambient sound. There was no evidence that the magnitude of the observed response differed between natural and man-made sounds. We also found that the probability of a humpback whale calling in the survey area decreased by 9% for every 1 dB increase in ambient sound. Controlling for ambient sound levels, the probability of a humpback whale calling in the survey area was 31–45% lower when vessel noise contributed to the soundscape than when only natural sounds were present.
•Corticosterone concentrations vary by sampling year.•Corticosterone concentrations are higher in calves than non-calves.•Corticosterone concentrations peak in males from 15 to 25 years of age.•The ...spread of corticosterone concentrations in Hawaii are greater than in Alaska.•Mean corticosterone concentrations are not significantly different between locations.•There is not a consistent trend in corticosterone concentration by season or month.•The variables that best predict corticosterone concentration are year and Julian day.
Developing a better understanding of the stress response is critical to ensuring the health and sustainability of marine mammal populations. However, accurately measuring and interpreting a stress response in free-ranging, large cetaceans is a nascent field. Here, an enzyme immunoassay for corticosterone was validated for use in biopsy samples from male humpback whales (Megaptera novaeangliae). Analyses were conducted on 247 male North Pacific humpback whale blubber samples, including 238 non-calves and 9 calves that were collected on the Hawaiian breeding and Southeast Alaskan feeding grounds from 2004 to 2006. Significant relationships were found when corticosterone concentrations were examined by year, age class and distribution between locations. When examined by year, corticosterone concentrations for male humpback whales were higher in Hawaii in 2004 than in 2005 and 2006 (p < 0.05). Corticosterone concentration also varied by age class with initially high concentrations at birth which subsequently tapered off and remained relatively low until sexual maturity was reached around age 8–10 years. Corticosterone concentrations appeared to peak in male humpback whales around 15–25 years of age. Blubber biopsies from Alaska and Hawaii had similar mean corticosterone concentrations, yet the variability in these samples was much greater for whales located in Hawaii. It is clear that much work remains to be done in order to accurately define or monitor a stress response in male humpback whales and that specific attention is required when looking at age, sex, and yearly trends. Our results suggest that a stress response may be most impacted by age and yearly oceanographic conditions and needs to be initially examined at the individual level.
The global COVID-19 pandemic caused a sharp decline in vessel traffic in many areas around the world, including vessel-based tourism throughout Alaska, USA in 2020. Marine vessel traffic has long ...been known to affect the underwater acoustic environment with direct and indirect effects on marine ecological processes. Glacier Bay National Park in southeastern Alaska has monitored underwater sound since 2000. We used continuous, calibrated hydrophone recordings to examine 2020 ambient sound levels compared with previous years: 2018, the most recent year with data available, and 2016 for historical perspective. Park tourism occurs mainly in May–September. Overall, the number of vessel entries in Glacier Bay was 44–49% lower in 2020 (2020:
n
= 1,831; 2018:
n
= 3,599; 2016:
n
= 3,212) affecting all vessel classes, including the complete absence of cruise ships and only three tour vessel trips. In all years, we found clear seasonal and diurnal patterns in vessel generated noise, focused from 06:00 to 20:00 local time (LT) in the summer months. Broadband (17.8–8,910 Hz) sound levels in the 2020 Visitor Season were 2.7 dB lower than 2018 and 2.5 dB lower than 2016. Focusing on morning (06:00–09:00 LT) and afternoon (15:00–18:00 LT) time-blocks when tour vessels and cruise ships enter and exit Glacier Bay, median broadband sound levels were 3.3–5.1 dB lower in 2020 than prior years. At the 95th percentile levels, morning and afternoon peak times in 2020 were 6.3–9.0 dB quieter than previous years. A 3 dB decline in median sound level in the 125 Hz one-third octave band in 2020 reflects a change in medium and large vessel noise energy and/or harbor seal vocalizations. Our results suggest that all types of vessels had a role in the quieter underwater sound environment in 2020, with the combined acoustic footprint of tour vessels and cruise ships most evident in the decrease in the 95th percentile loudest sounds. This and other descriptions of the pandemic-induced quiet, and the gradual return to increased activity, can help inform efforts to improve existing methods to mitigate vessel noise impacts and maintain the ecological integrity of marine protected areas.
Purpose
To evaluate the prognostic value of coronary atherosclerotic burden, assessed by coronary artery calcium (CAC) score, and coronary vascular function, assessed by coronary flow reserve (CFR) ...in patients with suspected coronary artery disease (CAD).
Methods
We studied 436 patients undergoing hybrid
82
Rb positron emission tomography/computed tomography imaging. CAC score was measured according to the Agatston method, and patients were categorized into three groups (0, <400, and ≥400). CFR was calculated as the ratio of hyperemic to baseline myocardial blood flow, and it was considered reduced when <2.
Results
Follow-up was 94% complete during a mean period of 47±15 months. During follow-up, 17 events occurred (4% cumulative event rate). Event-free survival decreased with worsening of CAC score category (
p
< 0.001) and in patients with reduced CFR (
p
< 0.005). At multivariable analysis, CAC score ≥400 (
p
< 0.01) and CFR (
p
< 0.005) were independent predictors of events. Including CFR in the prognostic model, continuous net reclassification improvement was 0.51 (0.14 in patients with events and 0.37 in those without). At classification and regression tree analysis, the initial split was on CAC score. For patients with a CAC score < 400, no further split was performed, while patients with a CAC score ≥400 were further stratified by CFR values. Decision curve analyses indicate that the model including CFR resulted in a higher net benefit across a wide range of decision threshold probabilities.
Conclusions
In patients with suspected CAD, CFR provides significant incremental risk stratification over established cardiac risk factors and CAC score for prediction of adverse cardiac events.
Abstract
Understanding reproductive physiology in mysticetes has been slowed by the lack of repeated samples from individuals. Analysis of humpback whale baleen enables retrospective hormone analysis ...within individuals dating back 3–5 years before death. Using this method, we investigated differences in four steroid hormones involved in reproduction and mating during confirmed pregnant and non-pregnant periods in two female humpback whales (Megaptera novaeangliae) with known reproductive histories based on sightings and necropsy data. Cortisol, corticosterone, testosterone, and estradiol concentrations were determined via enzyme immunoassay using subsamples of each baleen plate at 2 cm intervals. There were no significant differences in cortisol or corticosterone during pregnancy when compared to non-pregnancy (inter-calving interval), but there were significant differences between the two whales in average glucocorticoid concentrations, with the younger whale showing higher values overall. For testosterone, levels for the younger female peaked at parturition in one pregnancy, but also had spikes during non-pregnancy. The older female had three large spikes in testosterone, one of which was associated with parturition. Estradiol had large fluctuations in both whales but had generally lower concentrations during non-pregnancy than during pregnancy. There were peaks in estradiol before each pregnancy, possibly coinciding with ovulation, and peaks coinciding with the month of parturition. Both estradiol and testosterone could be useful for determining ovulation or impending birth. Using baleen to investigate retrospective steroid hormone profiles can be used for elucidating long-term patterns of physiological change during gestation.
Lay summary
Case studies of two pregnant humpback whales whose hormones were analyzed in baleen may illuminate when humpback whales ovulate, gestate, and give birth. These physiological metrics could assist in accurate population growth assessments and conservation of the species. This study shows that baleen hormone analysis can be a useful tool for understanding whale reproductive physiology.
Monitoring patterns in biodiversity and phenology have become increasingly important given accelerating levels of anthropogenic change. Long‐term monitoring programs have reported earlier occurrence ...of spring activity, reflecting species response to climate change. Although tracking shifts in spring migration represents a valuable approach to monitoring community‐level consequences of climate change, robust long‐term observations are challenging and costly. Audio recordings and metrics of bioacoustic activity could provide an effective method for monitoring changes in songbird activity and broader biotic interactions. We used 3 years of spring and fall recordings at six sites in Glacier Bay National Park, Alaska, an area experiencing rapid warming and glacial retreat, to examine the utility of bioacoustics to detect changes in songbird phenology. We calculated the Acoustic Complexity Index (ACI), an algorithm representing an index of bird community complexity. Abrupt changes in ACI values from winter to spring corresponded to spring transition, suggesting that ACI may be an effective, albeit coarse metric to detect the arrival of migrating songbirds. The first peak in ACI shifted from April 16 to April 11 from 2012 to 2014. Changes in ACI were less abrupt in the fall due to weather events, suggesting spring recordings are better suited to indicate phenology. To ensure changes in ACI values were detecting real changes in songbird activity, we explored the relationship between ACI and song of three species: varied thrush (Ixoreus naevius), Pacific wren (Troglodytes pacificus), and ruby‐crowned kinglet (Regulus calendula). ACI was positively related to counts of all species, but most markedly with song of the varied thrush, the most common species in our recordings and a known indicator of forest ecosystem health. We conclude that acoustic recordings paired with bioacoustic indices may be a useful method of monitoring shifts in songbird communities due to climate change and other sources of anthropogenic disturbance.
Audio recordings and metrics of bioacoustic activity could provide an effective method for monitoring changes in songbird phenology due to climate change. We used 3 years of spring and fall recordings at six sites in Glacier Bay National Park, Alaska, an area experiencing rapid warming and glacial retreat. Bioacoustic index values from recordings corresponded to the arrival of migrants in the spring and call counts of three songbird species, including a known indicator of forest ecosystem health.
Investigating long term trends in acoustic communication is essential for understanding the role of sound in social species. Humpback whales are an acoustically plastic species known for producing ...rapidly-evolving song and a suite of non-song vocalizations ("calls") containing some call types that exhibit short-term stability. By comparing the earliest known acoustic recordings of humpback whales in Southeast Alaska (from the 1970's) with recordings collected in the 1990's, 2000's, and 2010's, we investigated the long-term repertoire stability of calls on Southeast Alaskan foraging grounds. Of the sixteen previously described humpback whale call types produced in Southeast Alaska, twelve were detected in both 1976 and 2012, indicating stability over a 36-year time period; eight call types were present in all four decades and every call type was present in at least three decades. We conclude that the conservation of call types at this temporal scale is indicative of multi-generational persistence and confirms that acoustic communication in humpback whales is comprised of some highly stable call elements in strong contrast to ever-changing song.
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