Ashley Marie Blawas

All Publications

• Short-finned pilot whales modulate surfacing and breathing patterns more strongly in response to dives than in anticipation. American journal of physiology. Regulatory, integrative and comparative physiology Blawas, A. M., Shearer, J. M., Fahlman, A., Read, A. J., Nowacek, D. P. 2025

  Abstract

  Diving marine mammals must allocate time between respiring at the surface and foraging underwater. Previous studies of optimal diving theory have attempted to predict such patterns, but the amount of time divers must spend at the surface before and after dives of varying durations remains difficult to assess. Here, we examined the surfacing and breathing patterns of short-finned pilot whales (Globicephala macrorhynchus) from biologger data to examine their use of anticipatory versus reactive strategies. We used linear mixed effects models to examine the effect of dive characteristics on surface interval (SI) durations and breathing rate. Pilot whales increased SI duration before dives of increasing duration and after dives of increasing activity. Instantaneous breathing rates (fRs) of pilot whales demonstrated little anticipation but rather a strong reactive pattern seen by the modulation of fR in response to the previous rather than upcoming dive. During typical SIs, fR was predicted by time since previous dive, duration of the previous dive, time until upcoming dive, and activity of the previous dive. Short-finned pilot whales in our study area exhibit both benthic and pelagic foraging which may compel anticipation when prey capture is predictable and reaction when prey capture is difficult to predict. The observed surfacing and breathing patterns therefore likely reflect a balance of the needs for blood gas homeostasis, aerobic metabolism, and the variability of foraging opportunities. An improved understanding of how animals make decisions about diving is critical for informing predictions of how they will contend with changing ocean landscapes.

  View details for DOI 10.1152/ajpregu.00145.2025

  View details for PubMedID 41297039

• Daily energetic expenditure and energy consumption of short-finned pilot whales. The Journal of experimental biology Gough, W. T., Madrigal, B. C., Hollers, A., Currie, J. J., Baird, R. W., West, K. L., Fahlman, A., Fish, F. E., Evans, L., van Aswegen, M., Stirling, B., Pacini, A., Olson, G. L., Stack, S. H., Blawas, A. M., Walker, W. A., Bejder, L. 2025; 228 (21)

  Abstract

  Diving is one of the most important behaviors undertaken by marine mammals. Pilot whales (Globicephala spp.) are oceanic dolphins that regularly forage at extreme depths (∼600-1000 m) and maintain body sizes similar to beaked whales. They are also listed as data deficient, with little known about their population dynamics. To help fill this knowledge gap, we estimated their energetic demands through a combination of multiple data streams (e.g. unoccupied aerial systems photogrammetry, high-resolution accelerometry tag data, stomach content analysis and long-duration dive data from satellite tags) from short-finned pilot whales (Globicephala macrorhynchus) in Hawaiian waters. We estimated and compared pilot whale field metabolic rates from breathing frequency against a more granular cost of transport method developed from morphometrics and swimming kinematics, finding that these methods gave similar estimates of energetic expenditure during foraging dives. We then combined expenditure and intake estimates into an exploratory model of daily net energetic balance. Using an estimate of prey size derived from squid beaks collected from a stranded animal, we found that an average of 142±59.8 squid day-1 (52,000±21,800 squid year-1) is enough for an average adult short-finned pilot whale to reach a neutral net energetic balance. This species has an estimated population abundance of ∼8000 individuals in Hawaiian waters, suggesting that the population as a whole would require 416±175 million squid (at an average of 559±126 kJ squid-1) or approximately 88,000±37,000 tonnes of squid annually, assuming similar energetic requirements for each animal.

  View details for DOI 10.1242/jeb.249821

  View details for PubMedID 41232179

• Life in the slowest lane: Feeding allometry lowers metabolic rate scaling in the largest whales. Science advances Blawas, A. M., Videsen, S. K., Cade, D. E., Calambokidis, J., Friedlaender, A. S., Johnston, D. W., Madsen, P. T., Goldbogen, J. A. 2025; 11 (32): eadw2232

  Abstract

  The hypothesized impacts of whale foraging on ocean productivity are ultimately defined by their metabolic rate, but determining energy expenditure for ocean giants remains challenging. The largest baleen whales use a high-drag lunge-feeding strategy that is hypothesized to come at a high energetic cost, thus requiring exceptional calorie intake. We used biologging tags to measure respiratory rates in foraging rorquals and demonstrate that their field metabolic rates are less than half that predicted by prey consumption estimates and by scaling predictions from smaller marine mammals. The relative cost of rorqual foraging decreases with increasing size as larger whales spend disproportionately longer time filtering prey from engulfed water. By decoupling active swimming and filtration, the largest rorquals forage with limited movement costs. The evolution of lunge feeding confers an energetic advantage that is unique among filter feeders and may have provided an evolutionary pathway to the largest body sizes.

  View details for DOI 10.1126/sciadv.adw2232

  View details for PubMedID 40768593

  View details for PubMedCentralID PMC12327476

• Role of low-impact-factor journals in conservation implementation. Conservation biology : the journal of the Society for Conservation Biology Choi, J. J., Gaskins, L. C., Morton, J. P., Bingham, J. A., Blawas, A. M., Hayes, C., Hoyt, C., Halpin, P. N., Silliman, B. 2024: e14391

  Abstract

  Academic review, promotion, and tenure processes place a premium on frequent publication in high-impact factor (IF) journals. However, conservation often relies on species-specific information that is unlikely to have the broad appeal needed for high-IF journals. Instead, this information is often distributed in low-IF, taxa- and region-specific journals. This suggests a potential mismatch between the incentives for academic researchers and the scientific needs of conservation implementation. To explore this mismatch, we looked at federal implementation of the United States Endangered Species Act (ESA), which requires the use of the "best available science" to list a species as endangered or threatened and thus receive powerful legal protections. In assessing the relationship between academic sources of this "best available science" and ESA implementation, we looked at the 13,292 sources (e.g., academic journals, books, reports, regulations, personal communications, etc.) cited by the second Obama administration (2012-2016) across all ESA listings. We compared the IFs of all 4836 journals that published peer-reviewed papers cited in these listings against their citation frequency in ESA listings to determine whether a journal's IF varied in proportion with its contribution to federal conservation. Most of the peer-reviewed academic articles referenced in ESA listings came from low-IF or no-IF journals that tended to focus on specific taxa or regions. Although we support continued attention to cutting-edge, multidisciplinary science for its ability to chart new pathways and paradigms, our findings stress the need to value and fund the taxa- and region-specific science that underpins actionable conservation laws.

  View details for DOI 10.1111/cobi.14391

  View details for PubMedID 39417626

• Aerobic dive limit in short-finned pilot whales Globicephala macrorhynchus: an assessment of behavioral criteria MARINE ECOLOGY PROGRESS SERIES Blawas, A. M., Miller, L. E., Shearer, J. M., Cioffi, W. R., Webster, D. L., Swaim, Z. T., Foley, H. J., Waples, D. M., Quick, N. J., Nowacek, D. P., Read, A. J. 2024; 744: 161-170

  View details for DOI 10.3354/meps14670

  View details for Web of Science ID 001339267100002

• Passive acoustic surveys demonstrate high densities of sperm whales off the mid-Atlantic coast of the USA in winter and spring. Marine environmental research Boisseau, O., Nowacek, D., Pabst, D. A., Roberts, J., Blawas, A., Clabaugh, A., McLanaghan, R., Moscrop, A., Levenson, J. J. 2024; 201: 106674

  Abstract

  Oceans are increasingly crowded by anthropogenic activities yet the impact on Outer Continental Shelf (OCS) marine life remains largely unquantified. The MAPS (Marine Mammal Acoustic and Spatial Ecology) study of 2019 included passive acoustic and visual vessel surveys over the Mid-Atlantic OCS of the USA to address data gaps in winter/spring for deep-diving cetaceans, including sperm whales. Echolocation clicks were used to derive slant ranges to sperm whales for design- and model-based density estimates. Although more survey effort was realised in the spring, high densities of whales were identified in both winter and spring (10.46 and 8.89 per 1000 km2 respectively). The spring model-based abundance estimate of 1587 whales (CI 946-2663) was considered the most representative figure, in part due to lower coefficients of variation. Modelling suggested that high densities of whales were associated with warm core rings, eddies and edges. As OCS waters provide an important foraging habitat for North Atlantic sperm whales, appropriate mitigation is required to ensure commercial pressures to develop offshore energy do not negatively affect this endangered species.

  View details for DOI 10.1016/j.marenvres.2024.106674

  View details for PubMedID 39168086

• An integrated comparative physiology and molecular approach pinpoints mediators of breath-hold capacity in dolphins. Evolution, medicine, and public health Blawas, A. M., Ware, K. E., Schmaltz, E., Zheng, L., Spruance, J., Allen, A. S., West, N., Devos, N., Corcoran, D. L., Nowacek, D. P., Eward, W. C., Fahlman, A., Somarelli, J. A. 2021; 9 (1): 420-430

  Abstract

  Ischemic events, such as ischemic heart disease and stroke, are the number one cause of death globally. Ischemia prevents blood, carrying essential nutrients and oxygen, from reaching tissues, leading to cell and tissue death, and eventual organ failure. While humans are relatively intolerant to ischemic events, other species, such as marine mammals, have evolved a unique tolerance to chronic ischemia/reperfusion during apneic diving. To identify possible molecular features of an increased tolerance for apnea, we examined changes in gene expression in breath-holding dolphins.Here, we capitalized on the adaptations possesed by bottlenose dolphins (Tursiops truncatus) for diving as a comparative model of ischemic stress and hypoxia tolerance to identify molecular features associated with breath holding. Given that signals in the blood may influence physiological changes during diving, we used RNA-Seq and enzyme assays to examine time-dependent changes in gene expression in the blood of breath-holding dolphins.We observed time-dependent upregulation of the arachidonate 5-lipoxygenase (ALOX5) gene and increased lipoxygenase activity during breath holding. ALOX5 has been shown to be activated during hypoxia in rodent models, and its metabolites, leukotrienes, induce vasoconstriction.The upregulation of ALOX5 mRNA occurred within the calculated aerobic dive limit of the species, suggesting that ALOX5 may play a role in the dolphin's physiological response to diving, particularly in a pro-inflammatory response to ischemia and in promoting vasoconstriction. These observations pinpoint a potential molecular mechanism by which dolphins, and perhaps other marine mammals, respond to the prolonged breath holds associated with diving.

  View details for DOI 10.1093/emph/eoab036

  View details for PubMedID 35169481

  View details for PubMedCentralID PMC8833867

• Conditioned Variation in Heart Rate During Static Breath-Holds in the Bottlenose Dolphin (Tursiops truncatus). Frontiers in physiology Fahlman, A., Cozzi, B., Manley, M., Jabas, S., Malik, M., Blawas, A., Janik, V. M. 2020; 11: 604018

  Abstract

  Previous reports suggested the existence of direct somatic motor control over heart rate (f H) responses during diving in some marine mammals, as the result of a cognitive and/or learning process rather than being a reflexive response. This would be beneficial for O2 storage management, but would also allow ventilation-perfusion matching for selective gas exchange, where O2 and CO2 can be exchanged with minimal exchange of N2. Such a mechanism explains how air breathing marine vertebrates avoid diving related gas bubble formation during repeated dives, and how stress could interrupt this mechanism and cause excessive N2 exchange. To investigate the conditioned response, we measured the f H-response before and during static breath-holds in three bottlenose dolphins (Tursiops truncatus) when shown a visual symbol to perform either a long (LONG) or short (SHORT) breath-hold, or during a spontaneous breath-hold without a symbol (NS). The average f H (if Hstart), and the rate of change in f H (dif H/dt) during the first 20 s of the breath-hold differed between breath-hold types. In addition, the minimum instantaneous f H (if Hmin), and the average instantaneous f H during the last 10 s (if Hend) also differed between breath-hold types. The dif H/dt was greater, and the if Hstart, if Hmin, and if Hend were lower during a LONG as compared with either a SHORT, or an NS breath-hold (P < 0.05). Even though the NS breath-hold dives were longer in duration as compared with SHORT breath-hold dives, the dif H/dt was greater and the if Hstart, if Hmin, and if Hend were lower during the latter (P < 0.05). In addition, when the dolphin determined the breath-hold duration (NS), the f H was more variable within and between individuals and trials, suggesting a conditioned capacity to adjust the f H-response. These results suggest that dolphins have the capacity to selectively alter the f H-response during diving and provide evidence for significant cardiovascular plasticity in dolphins.

  View details for DOI 10.3389/fphys.2020.604018

  View details for PubMedID 33329056

  View details for PubMedCentralID PMC7732665