A novel RT-qPCR health assay reveals differential expression of stress and immunoregulatory genes between the seasonal migrations of humpback whales (Megaptera novaeangliae)

Health information is essential for the conservation management of whale species. However, assessing the health of free-ranging whales is challenging as samples are primarily limited to skin and blubber tissue. Reverse transcription quantitative polymerase chain reaction (RT-qPCR) offers a method to measure health from blubber RNA, providing insights into energetic status, stress and immune activity. To identify changes in health, natural differences in baseline gene expression linked to an individual's sex, reproductive status and life-history stage must first be quantified. This study aimed to establish baseline gene expression indices of health in migrating humpback whales (Megaptera novaeangliae). To do this, we developed an assay to quantify seven health-related gene transcripts (Leptin, Leptin Receptor, Adiponectin, Aryl Hydrocarbon Receptor, Tumour Necrosis Factor-α, Interleukin-6, Heat Shock Protein-70) and used Bayesian mixed effect models to assess differential baseline expression based on sex, lactation status and migration stage (northbound to and southbound from the annual breeding grounds). Results showed no significant contribution of sex to differential baseline expression. However, lactating individuals exhibited downregulated AhR and HSP-70 compared to non-lactating conspecifics. Additionally, southbound individuals demonstrated significantly upregulated HSP-70 and downregulated TNF-alpha, suggesting a relationship between these inflammation-linked transcripts and migratory fasting. Our results suggest that baseline differences due to migratory stage and lactation status should be considered in health applications of this assay. Future monitoring efforts can use our baseline measurements to better understand how gene expression is tied to population-level impacts, such as reduced prey availability or migratory stressors.

Singing humpback whales respond to wind noise, but not to vessel noise

Animal communication systems evolved in the presence of noise generated by natural sources. Many species can increase the source levels of their sounds to maintain effective communication in elevated noise conditions, i.e. they have a Lombard response. Human activities generate additional noise in the environment creating further challenges for these animals. Male humpback whales are known to adjust the source levels of their songs in response to wind noise, which although variable is always present in the ocean. Our study investigated whether this Lombard response increases when singing males are exposed to additional noise generated by motor vessels. Humpback whale singers were recorded off eastern Australia using a fixed hydrophone array. The source levels of the songs produced while the singers were exposed to varying levels of wind noise and vessel noise were measured. Our results show that, even when vessel noise is dominant, singing males still adjust the source levels of their songs to compensate for the underlying wind noise, and do not further increase their source levels to compensate for the additional noise produced by the vessel. Understanding humpback whales' response to noise is important for developing mitigation policies for anthropogenic activities at sea.

A mammalian messenger RNA sex determination method from humpback whale (Megaptera novaeangliae) blubber biopsies

The large size of free-ranging mysticetes, such as humpback whales (Megaptera novaeangliae), make capture and release health assessments unfeasible for conservation research. However, individual energetic condition or reproductive health may be assessed from the gene expression of remotely biopsied tissue. To do this, researchers must reliably extract RNA and interpret gene expression measurements within the context of an individual's sex. Here, we outline an RNA extraction protocol from blubber tissue and describe a novel mammalian RNA sex determination method. Our method consists of a duplex reverse transcription-quantitative (real-time) polymerase chain reaction (RT-qPCR) with primer sets for a control gene (ACTB) and the X-chromosome inactivation gene (XIST). Products of each RT-qPCR had distinct melting temperature profiles based on the presence (female) or absence (male) of the XIST transcript. Using high-resolution melt analysis, reactions were sorted into one of two clusters (male/female) based on their melting profiles. We validated the XIST method by comparing results with a standard DNA-based method. With adequate quantities of RNA (minimum of approx. 9 ng µl^-1), the XIST sex determination method shows 100% agreement with traditional DNA sex determination. Using the XIST method, future cetacean health studies can interpret gene expression within the context of an individual's sex, all from a single extraction.

Humpback whale adult females and calves balance acoustic contact with vocal crypsis during periods of increased separation

Acoustic communication is important for animals with dependent young, particularly when they are spatially separated. Maternal humpback whales (Megaptera novaeangliae) use acoustic calling to help minimize the risk of separation from their young calves during migration. These pairs also use acoustic crypsis to minimize detection by males. How they balance a restricted active space with the need to maintain acoustic contact during periods of separation is not yet understood. Here, we analyzed movement metrics of tagged adult female-calf pairs during migration to identify two behavioral states, "resting/milling" and "travelling." When travelling, these pairs dived synchronously and exhibited little to no spatial separation. Alternatively, adult females had significantly longer dive durations (p < .01) when resting, and while they spent prolonged times at depth, calves would surface several times independently. This demonstrated that these pairs are frequently separated during periods of rest. We then determined whether the call rates and acoustic levels of these pairs increased with more frequent separation, finding that both adult females and calves significantly increased their call rates, but not levels, when resting. We also found that adult female-calf pairs have a restricted active space, with less than 15% of calls estimated to be detectable beyond 2 km. However, as with call level, detection distance did not differ significantly between the two behavioral states. In summary, adult female-calf pairs maintain successful communication during periods of separation by calling more frequently rather than by producing louder calls. This strategy aids in maintaining acoustic contact while simultaneously limiting detectability by conspecifics.

Fuzzy clustering as a tool to differentiate between discrete and graded call types

Animals may communicate potential information to conspecifics using stereotyped "discrete" calls and variable "graded" calls. However, animal vocal research often centers on identifying the number of call types in a repertoire rather than quantifying the amount of gradation. Here, fuzzy clustering was applied to the social call repertoire of a species with a complex communication system, the humpback whale (Megaptera novaeangliae). Of 26 call types, 6 were classified as discrete, 7 as graded, and 13 as intermediate. These results indicate that humpback whales have a graded call repertoire, and fuzzy clustering may be a useful approach to investigate this variability.

Cyanotoxin Analysis and Amino Acid Profiles of Cyanobacterial Food Items from Chad

In some parts of the world, cyanobacteria are used as a food in the human diet, due to their ready availability. Lake Chad, has long been a traditional site for the collection of Arthrospira fusiformis which is dried and processed at the lake into thin wafers called Dihé for later consumption or is transported to market for sale. However, Dihé purchased from markets in Chad has not been analyzed for known cyanobacterial toxins or assessed for total amino acid content. Since BMAA in traditional foodstuffs of the indigenous Chamorro people of Guam causes neurodegenerative illness, it is important that Dihé from Chad be analyzed for this neurotoxin. BMAA and its isomer AEG were not detected in our analyses, but a further isomer DAB was detected as both a free and bound amino acid, with an increase in the free concentration after acid hydrolysis of this fraction. Microcystins were present in 6 samples at up to 20 μg/g according to UPLC-PDA, although their presence could not be confirmed using PCR for known microcystin synthetic genes. Amino acid analysis of the cyanobacterial material from Chad showed the presence of large amounts of canonical amino acids, suggesting that this may supplement indigenous people on low protein diets, although regular monitoring of the foodstuffs for the presence of cyanotoxins should be performed.

Blubber cortisol levels in humpback whales (Megaptera novaeangliae): A measure of physiological stress without effects from sampling

Baleen whales are vulnerable to environmental impacts due to low fecundity, capital breeding strategies, and their reliance on a large amount of prey resources over large spatial scales. There has been growing interest in monitoring health and physiological stress in these species but, to date, few measures have been validated. The purpose of this study was to examine whether blubber cortisol could be used as a measure of physiological stress in humpback whales. Cortisol concentrations were initially compared between live, presumably 'healthy' whales (n = 187) and deceased whales (n = 35), which had died after stranding or entanglement, or washed ashore as a carcass. Deceased whales were found to have significantly higher cortisol levels (mean ± SD; 5.47 ± 4.52 ng/g) than live whales (0.51 ± 0.14 ng/g; p < 0.001), particularly for those animals that had experienced prolonged trauma (e.g. stranding) prior to death. Blubber cortisol levels in live whales were then examined for evidence of life history-related, seasonal, or sampling-related effects. Life history group and sampling-related factors, such as encounter time and the number of biopsy sampling attempts per animal, were found to be poor predictors of blubber cortisol levels in live whales. In contrast, blubber cortisol levels varied seasonally, with whales migrating north towards the breeding grounds in winter having significantly higher levels (0.54 ± 0.21 ng/g, p = 0.016) than those migrating south towards the feeding grounds in spring (0.48 ± 1.23 ng/g). These differences could be due to additional socio-physiological stress experienced by whales during peaks in breeding activity. Overall, blubber cortisol appears to be a suitable measure of chronic physiological stress in humpback whales.

Ships and air guns reduce social interactions in humpback whales at greater ranges than other behavioral impacts

Understanding the interactions between human activity in the ocean and marine mammals is a fundamental step to developing responsible mitigation measures and informing policy. Here, the response of migrating humpback whales to vessels towing seismic air gun arrays (on or off) was quantified as a reduction in their likelihood of socially interacting (joining together). Groups were significantly less likely to participate in a joining interaction in the presence of a vessel, regardless of whether or not the air guns were active. This reduction was especially pronounced in groups within a social environment that favored joining, that is, when singing whales or other groups were nearby. Seismic survey mitigation practices are designed primarily to prevent damage to whales' hearing from close-by sources. Here, we found potentially detrimental behavioral changes at much greater ranges, and much lower received levels, than those used for current mitigation recommendations.

The influence of physiological status on the reproductive behaviour of humpback whales (Megaptera novaeangliae)

For most cetacean species, there is little known about how an individual's physiology influences its behaviour. Humpback whales (Megaptera novaeangliae) are a good candidate to examine such links as they have a well-described distribution and behaviour, can be consistently sampled using remote biopsy systems, and have been the subject of several previous endocrine studies. The objective here was to examine whether a female humpback whale's social state (i.e. escorted by a male or not) is related to her endocrine condition, and whether male dominance ranking is related to testosterone levels. Skin and blubber biopsies were collected from the east and west Australian humpback whale populations in 2010-2016 (n = 252) at multiple times throughout the winter-spring breeding season. Steroid hormones were extracted from blubber and concentrations of progesterone (a marker for pregnancy), testosterone (a marker of male testicular activity) and oestradiol (a potential marker of ovarian activity) measured using enzyme-immunoassays. Principal escorts-the dominant males in mixed sex groups-had significantly higher blubber testosterone levels (mean ± SE; 1.43 ± 0.20 ng/g wet weight) than subordinate, secondary escorts (0.69 ± 0.06 ng/g wet weight). Females that were escorted by males typically possessed elevated blubber oestradiol levels (1.96 ± 0.25 ng/g wet weight; p = 0.014); few were considered to be pregnant (p = 0.083). 'Unescorted' females displayed characteristically lower blubber oestradiol levels (0.56 ± 0.06 ng/g wet weight). Together, these results are consistent with 'challenge hypothesis' theory and suggest the existence of associated reproductive patterns in humpback whales.

Network analysis reveals underlying syntactic features in a vocally learnt mammalian display, humpback whale song

Vocal communication systems have a set of rules that govern the arrangement of acoustic signals, broadly defined as 'syntax'. However, there is a limited understanding of potentially shared or analogous rules across vocal displays in different taxa. Recent work on songbirds has investigated syntax using network-based modelling. This technique quantifies features such as connectivity (adjacent signals in a sequence) and recurring patterns. Here, we apply network-based modelling to the complex, hierarchically structured songs of humpback whales (Megaptera novaeangliae) from east Australia. Given the song's annual evolving pattern and the cultural conformity of males within a population, network modelling captured the patterns of multiple song types over 13 consecutive years. Song arrangements in each year displayed clear 'small-world' network structure, characterized by clusters of highly connected sounds. Transitions between these connected sounds further suggested a combination of both structural stability and variability. Small-world network structure within humpback songs may facilitate the characteristic and persistent vocal learning observed. Similar small-world structures and transition patterns are found in several birdsong displays, indicating common syntactic patterns among vocal learning in multiple taxa. Understanding the syntactic rules governing vocal displays in multiple, independently evolving lineages may indicate what rules or structural features are important to the evolution of complex communication, including human language.

The effects of vessel noise on the communication network of humpback whales

Humpback whales rely on acoustic communication to mediate social interactions. The distance to which these social signals propagate from the signaller defines its communication space, and therefore communication network (number of potential receivers). As humpback whales migrate along populated coastlines, they are likely to encounter noise from vessel traffic which will mask their social signals. Since no empirical data exist on baleen whale hearing, the consequences of this are usually assumed, being the modelled reduction in their communication space. Here, the communication space and network of migrating humpback whales was compared in increasing wind-dominated and vessel-dominated noise. Behavioural data on their social interactions were then used to inform these models. In typical wind noise, a signaller's communication space was estimated to extend to 4 km, which agreed with the maximum separation distance between groups that socially interacted. An increase in vessel noise reduced the modelled communication area, along with a significant reduction in group social interactions, probably due to a reduction in their communication network. However, signal masking did not fully explain this change in social behaviour, implying there was also an additional effect of the physical presence of the vessel on signaller and receiver behaviour. Though these observed changes in communication space and social behaviour were likely to be short term and localized, an increase in vessel activity due to tourism and coastal population growth may cause more sustained changes along the humpback whale migration paths.

Evaluation of respiratory vapour and blubber samples for use in endocrine assessments of bottlenose dolphins (Tursiops spp.)

Blubber and respiratory vapour ('blow') are now commonly used for endocrine studies on cetaceans, primarily because they can be obtained using minimally invasive methods. For many species, these samples have yet to be validated for these purposes. The objective of this study was to examine the performance of blow and blubber hormone monitoring, relative to serum hormone monitoring, for evaluating the reproductive and adrenal condition of captive bottlenose dolphins (Tursiops spp.). Eighteen bottlenose dolphins were sampled five times for serum and blow and twice for blubber throughout a one-year period. Concentrations of progesterone, testosterone, oestradiol and cortisol were measured in each sample type. Hormone levels were examined in relation to dolphin age, sex, reproductive status, season, time of sample collection (morning/afternoon) and collection type (in- or out-of-water sampling). Patterns in hormone levels were similar for serum and blubber. For instance, in both sample types, progesterone levels were significantly higher in pregnant (serum: 34.10 ± 8.64 ng/mL; blubber: 13.01 ± 0.72 ng/g) than in non-pregnant females (serum: 0.32 ± 0.09 ng/mL; blubber: 1.17 ± 0.10 ng/g). This pattern was not detected in blow, primarily because seawater contamination, nylon sampling materials and variable sample volumes influenced measured concentrations. In addition, the respiratory water content of a blow sample is known to affect measured hormone levels. Two methods were trialled to control for variability in sample volumes and dilution: (1) normalising blow hormone concentrations relative to urea nitrogen levels (a potential endogenous standard), and (2) measuring the relative proportions (i.e. ratios) of blow hormones. These correction measures had little influence on blow hormone results. Further refinement of blow hormone monitoring methods is required before they can be used for reproductive or adrenal assessments of bottlenose dolphins. Blubber, on the other hand, should be a suitable proxy for serum when attempting to classify pregnancy status and male maturity in these species.

Source levels of humpback whales decrease with frequency suggesting an air-filled resonator is used in sound production

Source level and frequency are important in determining how far an acoustic signal can travel. However, in some species these sound characteristics have been found to be biomechanically linked, and therefore cannot be modified independently to achieve optimal transmission. This study investigates the variability in source levels and their relationship with frequency in the songs of humpback whales (Megaptera novaeangliae). Songs were recorded off eastern Australia using a fixed hydrophone array deployed on the whales' migratory corridor. Singing whales were acoustically tracked. An empirical, frequency-dependent model was used to estimate transmission loss. Source levels and frequency were measured for 2408 song units from 19 singers. Source levels varied from 138 to 187 dB re 1 μPa at 1 m (root mean squared), while peak frequency ranged between 52 and 3877 Hz. Much of the variability in source levels was accounted for by differences between the unit types, with mean source levels for each unit type varying by up to 17 dB. Source levels were negatively correlated with peak frequency and decreased by 2.3 dB per octave. The negative correlation between source levels and frequency is consistent with the presence of an air-filled resonator in the whales' sound production system.

Cultural revolutions reduce complexity in the songs of humpback whales

Much evidence for non-human culture comes from vocally learned displays, such as the vocal dialects and song displays of birds and cetaceans. While many oscine birds use song complexity to assess male fitness, the role of complexity in humpback whale (Megaptera novaeangliae) song is uncertain owing to population-wide conformity to one song pattern. Although songs change gradually each year, the eastern Australian population also completely replaces their song every few years in cultural 'revolutions'. Revolutions involve learning large amounts of novel material introduced from the Western Australian population. We examined two measures of song structure, complexity and entropy, in the eastern Australian population over 13 consecutive years. These measures aimed to identify the role of complexity and information content in the vocal learning processes of humpback whales. Complexity was quantified at two hierarchical levels: the entire sequence of individual sound 'units' and the stereotyped arrangements of units which comprise a 'theme'. Complexity increased as songs evolved over time but decreased when revolutions occurred. No correlation between complexity and entropy estimates suggests that changes to complexity may represent embellishment to the song which could allow males to stand out amidst population-wide conformity. The consistent reduction in complexity during song revolutions suggests a potential limit to the social learning capacity of novel material in humpback whales.

A behavioural dose-response model for migrating humpback whales and seismic air gun noise

The behavioural responses of migrating humpback whales to an air gun, a small clustered seismic array and a commercial array were used to develop a dose-response model, accounting for the presence of the vessel, array towpath relative to the migration and social and environmental parameters. Whale groups were more likely to show an avoidance response (increasing their distance from the source) when the received sound exposure level was over 130 dB re 1 μPa²·s and they were within 4 km of the source. The 50% probability of response occurred where received levels were 150-155 dB re 1 μPa²·s and they were within 2.5 km of the source. A small number of whales moving rapidly close to the source vessel did not exhibit an avoidance response at the highest received levels (160-170 dB re 1 μPa²·s) meaning it was not possible to estimate the maximum response threshold.

The communication space of humpback whale social sounds in wind-dominated noise

In animal social networks, a large acoustic communication space tends to involve complex networks. Signal masking may reduce this space, leading to detrimental effects on the animal's ability to obtain important social information. Humpback whales use acoustic social sounds (vocal sounds and surface-generated sounds from breaching or fin slapping) for within- and between-group communication. In this study, changes in various sound parameters (e.g., signal-above-noise and frequency content) of received humpback whale social sounds were statistically modeled against the combined effect of increasing wind-dominated noise and distance from the source (whale) to produce masking models. Behavioral data on vocalizing groups were also used to inform these models. The acoustic communication space, in this shallow water (<50 m) environment, extended to approximately 4 km from the signaler in median wind noise. However, the majority of behavioral interactions occurred within 2 km of the signaler. Surface-generated signals propagated better and likely function to maintain this space in higher wind noise. This study provides a basic wind-noise masking model for social communication signals in humpback whales which can be updated as more information on humpback auditory capabilities, and potential masking effects of anthropogenic noise sources, becomes available.

The communication space of humpback whale social sounds in wind-dominated noise

In animal social networks, a large acoustic communication space tends to involve complex networks. Signal masking may reduce this space, leading to detrimental effects on the animal's ability to obtain important social information. Humpback whales use acoustic social sounds (vocal sounds and surface-generated sounds from breaching or fin slapping) for within- and between-group communication. In this study, changes in various sound parameters (e.g., signal-above-noise and frequency content) of received humpback whale social sounds were statistically modeled against the combined effect of increasing wind-dominated noise and distance from the source (whale) to produce masking models. Behavioral data on vocalizing groups were also used to inform these models. The acoustic communication space, in this shallow water (<50 m) environment, extended to approximately 4 km from the signaler in median wind noise. However, the majority of behavioral interactions occurred within 2 km of the signaler. Surface-generated signals propagated better and likely function to maintain this space in higher wind noise. This study provides a basic wind-noise masking model for social communication signals in humpback whales which can be updated as more information on humpback auditory capabilities, and potential masking effects of anthropogenic noise sources, becomes available.

The communication space of humpback whale social sounds in wind-dominated noise

In animal social networks, a large acoustic communication space tends to involve complex networks. Signal masking may reduce this space, leading to detrimental effects on the animal's ability to obtain important social information. Humpback whales use acoustic social sounds (vocal sounds and surface-generated sounds from breaching or fin slapping) for within- and between-group communication. In this study, changes in various sound parameters (e.g., signal-above-noise and frequency content) of received humpback whale social sounds were statistically modeled against the combined effect of increasing wind-dominated noise and distance from the source (whale) to produce masking models. Behavioral data on vocalizing groups were also used to inform these models. The acoustic communication space, in this shallow water (<50 m) environment, extended to approximately 4 km from the signaler in median wind noise. However, the majority of behavioral interactions occurred within 2 km of the signaler. Surface-generated signals propagated better and likely function to maintain this space in higher wind noise. This study provides a basic wind-noise masking model for social communication signals in humpback whales which can be updated as more information on humpback auditory capabilities, and potential masking effects of anthropogenic noise sources, becomes available.

The behavioural response of migrating humpback whales to a full seismic airgun array

Despite concerns on the effects of noise from seismic survey airguns on marine organisms, there remains uncertainty as to the biological significance of any response. This study quantifies and interprets the response of migrating humpback whales (Megaptera novaeangliae) to a 3130 in³ (51.3l) commercial airgun array. We compare the behavioural responses to active trials (array operational; n = 34 whale groups), with responses to control trials (source vessel towing the array while silent; n = 33) and baseline studies of normal behaviour in the absence of the vessel (n = 85). No abnormal behaviours were recorded during the trials. However, in response to the active seismic array and the controls, the whales displayed changes in behaviour. Changes in respiration rate were of a similar magnitude to changes in baseline groups being joined by other animals suggesting any change group energetics was within their behavioural repertoire. However, the reduced progression southwards in response to the active treatments, for some cohorts, was below typical migratory speeds. This response was more likely to occur within 4 km from the array at received levels over 135 dB re 1 µPa²s.

Stereotypic and complex phrase types provide structural evidence for a multi-message display in humpback whales (Megaptera novaeangliae)

Male humpback whales produce a mating display called "song." Behavioral studies indicate song has inter- and/or intra-sexual functionality, suggesting song may be a multi-message display. Multi-message displays often include stereotypic components that convey group membership for mate attraction and/or male-male interactions, and complex components that convey individual quality for courtship. Humpback whale song contains sounds ("units") arranged into sequences ("phrases"). Repetitions of a specific phrase create a "theme." Within a theme, imperfect phrase repetitions ("phrase variants") create variability among phrases of the same type ("phrase type"). The hypothesis that song contains stereotypic and complex phrase types, structural characteristics consistent with a multi-message display, is investigated using recordings of 17 east Australian males (8:2004, 9:2011). Phrase types are categorized as stereotypic or complex using number of unit types, number of phrase variants, and the proportion of phrases that is unique to an individual versus shared amongst males. Unit types are determined using self-organizing maps. Phrase variants are determined by Levenshtein distances between phrases. Stereotypic phrase types have smaller numbers of unit types and shared phrase variants. Complex phrase types have larger numbers of unit types and unique phrase variants. This study supports the hypothesis that song could be a multi-message display.

Mechanisms of L-Serine Neuroprotection in vitro Include ER Proteostasis Regulation

β-N-methylamino-L-alanine (L-BMAA) is a neurotoxic non-protein amino acid produced by cyanobacteria. Recently, chronic dietary exposure to L-BMAA was shown to trigger neuropathology in nonhuman primates consistent with Guamanian ALS/PDC, a paralytic disease that afflicts Chamorro villagers who consume traditional food items contaminated with L-BMAA. However, the addition of the naturally occurring amino acid L-serine to the diet of the nonhuman primates resulted in a significant reduction in ALS/PDC neuropathology. L-serine is a dietary amino acid that plays a crucial role in central nervous system development, neuronal signaling, and synaptic plasticity and has been shown to impart neuroprotection from L-BMAA-induced neurotoxicity both in vitro and in vivo. We have previously shown that L-serine prevents the formation of autofluorescent aggregates and death by apoptosis in human cell lines and primary cells. These effects are likely imparted by L-serine blocking incorporation of L-BMAA into proteins hence preventing proteotoxic stress. However, there are likely other mechanisms for L-serine-mediated neuroprotection. Here, we explore the molecular mechanisms of L-serine neuroprotection using a human unfolded protein response real-time PCR array with genes from the ER stress and UPR pathways, and western blotting. We report that L-serine caused the differential expression of many of the same genes as L-BMAA, even though concentrations of L-serine in the culture medium were ten times lower than that of L-BMAA. We propose that L-serine may be functioning as a small proteostasis regulator, in effect altering the cells to quickly respond to a possible oxidative insult, thus favoring a return to homeostasis.

Using self-organizing maps to classify humpback whale song units and quantify their similarity

Classification of vocal signals can be undertaken using a wide variety of qualitative and quantitative techniques. Using east Australian humpback whale song from 2002 to 2014, a subset of vocal signals was acoustically measured and then classified using a Self-Organizing Map (SOM). The SOM created (1) an acoustic dictionary of units representing the song's repertoire, and (2) Cartesian distance measurements among all unit types (SOM nodes). Utilizing the SOM dictionary as a guide, additional song recordings from east Australia were rapidly (manually) transcribed. To assess the similarity in song sequences, the Cartesian distance output from the SOM was applied in Levenshtein distance similarity analyses as a weighting factor to better incorporate unit similarity in the calculation (previously a qualitative process). SOMs provide a more robust and repeatable means of categorizing acoustic signals along with a clear quantitative measurement of sound type similarity based on acoustic features. This method can be utilized for a wide variety of acoustic databases especially those containing very large datasets and can be applied across the vocalization research community to help address concerns surrounding inconsistency in manual classification.

L-Serine: a Naturally-Occurring Amino Acid with Therapeutic Potential

In human neuroblastoma cell cultures, non-human primates and human beings, L-serine is neuroprotective, acting through a variety of biochemical and molecular mechanisms. Although L-serine is generally classified as a non-essential amino acid, it is probably more appropriate to term it as a "conditional non-essential amino acid" since, under certain circumstances, vertebrates cannot synthesize it in sufficient quantities to meet necessary cellular demands. L-serine is biosynthesized in the mammalian central nervous system from 3-phosphoglycerate and serves as a precursor for the synthesis of the amino acids glycine and cysteine. Physiologically, it has a variety of roles, perhaps most importantly as a phosphorylation site in proteins. Mutations in the metabolic enzymes that synthesize L-serine have been implicated in various human diseases. Dosing of animals with L-serine and human clinical trials investigating the therapeutic effects of L-serine support the FDA's determination that L-serine is generally regarded as safe (GRAS); it also appears to be neuroprotective. We here consider the role of L-serine in neurological disorders and its potential as a therapeutic agent.

Changes in humpback whale singing behavior with abundance: Implications for the development of acoustic surveys of cetaceans

Acoustic surveys of vocal animals can have significant advantages over visual surveys, particularly for marine mammals. For acoustic density estimates to be viable, however, the vocal output of the animals surveyed needs to be determined under a range of conditions and shown to be a robust predictor of abundance. In this study, the songs of humpback whales, one of the most vocal and best studied species of marine mammals, were tested as predictors of abundance. Two acoustic metrics, the number of singing whales and amount of songs produced, were compared with the number of whales seen traversing a study site on the eastern coast of Australia over an 18 year period. Although there were predictive relationships between both metrics and numbers of passing whales, these relationships changed significantly as the population grew in size. The proportion of passing whales that sang decreased as the population increased. Singing in humpback whales, therefore, is a poor predictor even of relative abundance and illustrates the caution required when developing acoustic survey techniques particularly when using social vocalizations.

Determining the behavioural dose–response relationship of marine mammals to air gun noise and source proximity

The effect of various anthropogenic sources of noise (e.g. sonar, seismic surveys) on the behaviour of marine mammals is sometimes quantified as a dose–response relationship, where the probability of an animal behaviourally ‘responding’ (e.g. avoiding the source) increases with ‘dose’ (or received level of noise). To do this, however, requires a definition of a ‘significant’ response (avoidance), which can be difficult to quantify. There is also the potential that the animal ‘avoids’ not only the source of noise but also the vessel operating the source, complicating the relationship. The proximity of the source is an important variable to consider in the response, yet difficult to account for given that received level and proximity are highly correlated. This study used the behavioural response of humpback whales to noise from two different air gun arrays (20 and 140 cubic inch air gun array) to determine whether a dose–response relationship existed. To do this, a measure of avoidance of the source was developed, and the magnitude (rather than probability) of this response was tested against dose. The proximity to the source, and the vessel itself, was included within the one-analysis model. Humpback whales were more likely to avoid the air gun arrays (but not the controls) within 3 km of the source at levels over 140 re. 1 µPa2 s−1, meaning that both the proximity and the received level were important factors and the relationship between dose (received level) and response is not a simple one.

Potential motivational information encoded within humpback whale non-song vocal sounds

Acoustic signals in terrestrial animals follow motivational-structural rules to inform receivers of the signaler's motivational state, valence and level of arousal. Low-frequency "harsh" signals are produced in aggressive contexts, whereas high-frequency tonal sounds are produced in fearful/appeasement contexts. Using the non-song social call catalogue of humpback whales (Megaptera novaeangliae), this study tested for potential motivational-structural rules within the call catalogue of a baleen whale species. A total of 32 groups within different social contexts (ranging from stable, low arousal groups, such as a female with her calf, to affiliating, higher arousal, groups containing multiple males competing for access to the central female) were visually and acoustically tracked as they migrated southwards along the eastern coast of Australia. Social calls separated into four main cluster types, with signal structures in two categories consistent with "aggressive" signals and, "fearful/appeasement" signals in terrestrial animals. The group's use of signals within these clusters matched their context in that presumed low arousal non-affiliating groups almost exclusively used "low-arousal" signals (a cluster of low frequency unmodulated or upsweep sounds). Affiliating groups used a higher proportion of an intermediate cluster of signal types deemed "higher arousal" signals and groups containing three or more adults used a higher proportion of "aggressive" signal types.

Changes in vocal parameters with social context in humpback whales: considering the effect of bystanders

Abstract

Many theories and communication models developed from terrestrial studies focus on a simple dyadic exchange between a sender and receiver. During social interactions, the “frequency code” hypothesis suggests that frequency characteristics of vocal signals can simultaneously encode for static signaler attributes (size or sex) and dynamic information, such as motivation or emotional state. However, the additional presence of a bystander may result in a change of signaling behavior if the costs and benefits associated with the presence of this bystander are different from that of a simple dyad. In this study, two common humpback whale social calls (“wops” and “grumbles”) were tested for differences related to group social behavior and the presence of bystanders. “Wop” parameters were stable with group social behavior, but were emitted at lower (14 dB) levels in the presence of a nearby singing whale compared to when a singing whale was not in the area. “Grumbles” were emitted at lower (30–39 Hz) fundamental frequencies in affiliative compared to non-affiliative groups and, in the presence of a nearby singing whale, were also emitted at lower (14 dB) levels. Vocal rates did not significantly change. The results suggest that, in humpbacks, the frequency in certain sound types relates to the social behavior of the vocalizing group, implying a frequency code system. The presence of a nearby audible bystander (a singing whale) had no effect on this frequency code, but by reducing their acoustic level, the signal-to-noise ratio at the singer would have been below 0, making it difficult for the singer to audibly detect the group.

Significance statement

The frequency, duration, and amplitude parameters of humpback whale social vocalizations were tested between different social contexts: group social behavior (affiliating versus non-affiliating), the presence of a nearby singing whale, and the presence of a nearby non-singing group. “Grumbles” (commonly heard low-frequency unmodulated sounds) frequencies were lower in affiliating groups compared to non-affiliating groups, suggesting a change in group motivation (such as levels of aggression). “Wop” (another common sound type) structure (frequency and duration) was similar in affiliating and non-affiliating groups. In the presence of an audible bystander (a singing whale), both sound types were emitted at similar rates, but much lower amplitudes (14 dB), vastly reducing the detectability of these sounds by the singer. This suggests that these groups were acoustically avoiding the singing whale. They did not, however, acoustically respond to the presence of a nearby non-singing group.

Response of humpback whales (Megaptera novaeangliae) to ramp-up of a small experimental air gun array

'Ramp-up', or 'soft start', is a mitigation measure used in seismic surveys and involves increasing the radiated sound level over 20-40 min. This study compared the behavioural response in migrating humpback whales to the first stages of ramp-up with the response to a 'constant' source, 'controls' (in which the array was towed but not operated) with groups in the absence of the source vessel used as the 'baseline'. Although the behavioural response, in most groups, resulted in an increase in distance from the source (potential avoidance), there was no evidence that either 'ramp-up' or the constant source at a higher level was superior for triggering whales to move away from the source vessel. 'Control' groups also responded suggesting the presence of the source vessel had some effect. However, the majority of groups appeared to avoid the source vessel at distances greater than the radius of most mitigation zones.

Non-song social call bouts of migrating humpback whales

The use of stereotyped calls within structured bouts has been described for a number of species and may increase the information potential of call repertoires. Humpback whales produce a repertoire of social calls, although little is known about the complexity or function of these calls. In this study, digital acoustic tag recordings were used to investigate social call use within bouts, the use of bouts across different social contexts, and whether particular call type combinations were favored. Call order within bouts was investigated using call transition frequencies and information theory techniques. Call bouts were defined through analysis of inter-call intervals, as any calls within 3.9 s of each other. Bouts were produced significantly more when new whales joined a group compared to groups that did not change membership, and in groups containing multiple adults escorting a female and calf compared to adult only groups. Although social calls tended to be produced in bouts, there were few repeated bout types. However, the order in which most call types were produced within bouts was non-random and dependent on the preceding call type. These bouts appear to be at least partially governed by rules for how individual components are combined.

Evidence of a Lombard response in migrating humpback whales (Megaptera novaeangliae)

The Lombard reflex is an increase in the subject's vocal levels in response to increased noise levels. This functions to maintain an adequate signal-to-noise ratio at the position of the receiver when noise levels vary. While it has been demonstrated in a small number of mammals and birds including some whales, it has not yet been shown to occur in one of the most vocal species of baleen whale, the humpback whale (Megaptera novaeangliae). Humpback whales were simultaneously visually and acoustically tracked (using an array of calibrated hydrophone buoys) as they migrated southward. Source levels of social vocalizations were estimated from measured received levels and a site-specific empirical sound propagation model developed. In total, 226 social vocalizations from 16 passing groups of whales were selected for final analysis. Noise levels were predominantly wind-dependent (from sea surface motion) and ranged from 81 to 108 dB re 1 μPa in the 36 Hz-2.8 kHz band. Vocalization source levels increased by 0.9 dB for every 1 dB increase in wind-dependent background noise levels, with source levels (at 1 m) being maintained ∼60 dB above the noise level.

Source levels of social sounds in migrating humpback whales (Megaptera novaeangliae)

The source level of an animal sound is important in communication, since it affects the distance over which the sound is audible. Several measurements of source levels of whale sounds have been reported, but the accuracy of many is limited because the distance to the source and the acoustic transmission loss were estimated rather than measured. This paper presents measurements of source levels of social sounds (surface-generated and vocal sounds) of humpback whales from a sample of 998 sounds recorded from 49 migrating humpback whale groups. Sources were localized using a wide baseline five hydrophone array and transmission loss was measured for the site. Social vocalization source levels were found to range from 123 to 183 dB re 1 μPa @ 1 m with a median of 158 dB re 1 μPa @ 1 m. Source levels of surface-generated social sounds ("breaches" and "slaps") were narrower in range (133 to 171 dB re 1 μPa @ 1 m) but slightly higher in level (median of 162 dB re 1 μPa @ 1 m) compared to vocalizations. The data suggest that group composition has an effect on group vocalization source levels in that singletons and mother-calf-singing escort groups tend to vocalize at higher levels compared to other group compositions.

Temporal stability and change in the social call repertoire of migrating humpback whales

Quantifying the stability of a species vocal repertoire is fundamental for further investigations into repertoire function and geographic variation. Changes to the repertoire of sounds used in the song displays of male humpback whales have been well studied. In contrast, little is known about the stability of this species' non-song vocal calls. The stability of the social call repertoire of east Australian humpback whales was investigated from 1997, 2003-2004, and 2008. Out of 46 qualitatively defined call types, 19 were classified as "song-unit calls" that tended to change with the song, and 15 were "inconsistent" and only found in one or two years. Twelve call types were "stable" and present in all years and were commonly produced (64.2% of calls). Stable calls tended to vary in some of the measured call parameters but there was no clear trend between years. This result could indicate that minor changes to calls are not permanent, but reflect individual differences in call production or the graded nature of calls within different social environments. This research has clearly identified stable calls in the call repertoire of humpback whales and while their function is not well understood, their stability suggests an important role in social interactions.

Multivariate analysis of behavioural response experiments in humpback whales (Megaptera novaeangliae)

The behavioural response study (BRS) is an experimental design used by field biologists to determine the function and/or behavioural effects of conspecific, heterospecific or anthropogenic stimuli. When carrying out these studies in marine mammals it is difficult to make basic observations and achieve sufficient samples sizes because of the high cost and logistical difficulties. Rarely are other factors such as social context or the physical environment considered in the analysis because of these difficulties. This paper presents results of a BRS carried out in humpback whales to test the response of groups to one recording of conspecific social sounds and an artificially generated tone stimulus. Experiments were carried out in September/October 2004 and 2008 during the humpback whale southward migration along the east coast of Australia. In total, 13 'tone' experiments, 15 'social sound' experiments (using one recording of social sounds) and three silent controls were carried out over two field seasons. The results (using a mixed model statistical analysis) suggested that humpback whales responded differently to the two stimuli, measured by changes in course travelled and dive behaviour. Although the response to 'tones' was consistent, in that groups moved offshore and surfaced more often (suggesting an aversion to the stimulus), the response to 'social sounds' was highly variable and dependent upon the composition of the social group. The change in course and dive behaviour in response to 'tones' was found to be related to proximity to the source, the received signal level and signal-to-noise ratio (SNR). This study demonstrates that the behavioural responses of marine mammals to acoustic stimuli are complex. In order to tease out such multifaceted interactions, the number of replicates and factors measured must be sufficient for multivariate analysis.

Kavalactones Yangonin and Methysticin induce apoptosis in human hepatocytes (HepG2) in vitro

While cases of severe kava hepatotoxicity have been reported, studies examining the toxicity of individual kavalactones are limited. The present study examined the in vitro hepatotoxicity of kavain, methysticin and yangonin on human hepatocytes (HepG2) and the possible mechanism(s) involved. Cytotoxicity was assessed using lactate dehydrogenase (LDH) and ethidium bromide (EB) assays. The mode of cell death was analysed with acridine orange/ethidium bromide dual staining with fluorescence microscopy. Glutathione oxidation was measured using the ortho-phthalaldehyde (OPT) fluorescence assay. Kavain had minimal cytotoxicity, methysticin showed moderate concentration-dependent toxicity and yangonin displayed marked toxicity with ~ 40% reduction in viability in the EB assay. Acridine orange/ethidium bromide staining showed the predominant mode of cell death was apoptosis rather than necrosis. No significant changes were observed in glutathione levels, excluding this as the primary mechanism of cell death in this model. Further studies may elucidate the precise apoptotic pathways responsible and whether toxic kavalactone metabolites are involved.

Your attention please: increasing ambient noise levels elicits a change in communication behaviour in humpback whales (Megaptera novaeangliae)

High background noise is an important obstacle in successful signal detection and perception of an intended acoustic signal. To overcome this problem, many animals modify their acoustic signal by increasing the repetition rate, duration, amplitude or frequency range of the signal. An alternative method to ensure successful signal reception, yet to be tested in animals, involves the use of two different types of signal, where one signal type may enhance the other in periods of high background noise. Humpback whale communication signals comprise two different types: vocal signals, and surface-generated signals such as 'breaching' or 'pectoral slapping'. We found that humpback whales gradually switched from primarily vocal to primarily surface-generated communication in increasing wind speeds and background noise levels, though kept both signal types in their repertoire. Vocal signals have the advantage of having higher information content but may have the disadvantage of loosing this information in a noisy environment. Surface-generated sounds have energy distributed over a greater frequency range and may be less likely to become confused in periods of high wind-generated noise but have less information content when compared with vocal sounds. Therefore, surface-generated sounds may improve detection or enhance the perception of vocal signals in a noisy environment.

The social vocalization repertoire of east Australian migrating humpback whales (Megaptera novaeangliae)

Although the songs of humpback whales have been extensively studied, other vocalizations and percussive sounds, referred to as "social sounds," have received little attention. This study presents the social vocalization repertoire of migrating east Australian humpback whales from a sample of 660 sounds recorded from 61 groups of varying composition, over three years. The social vocalization repertoire of humpback whales was much larger than previously described with a total of 34 separate call types classified aurally and by spectrographic analysis as well as statistically. Of these, 21 call types were the same as units of the song current at the time of recording but used individually instead of as part of the song sequence, while the other 13 calls were stable over the three years of the study and were not part of the song. This study provides a catalog of sounds that can be used as a basis for future studies. It is an essential first step in determining the function, contextual use and cultural transmission of humpback social vocalizations.

Token economy, pimozide and chronic schizophrenia

Response to a token economy was assessed in male chronic schizophrenic in-patients who were given, in a double-blind cross-over trial, pimozide (up to 20 mg daily) or chlorpromazine )up to 1,000 mg daily), each for three months. After six months there was little change in the patients' mental state, but general ward behaviour and token-rewarded "target" behaviours improved significantly. There were no statistically significant between-drug differences, but the trend was that general ward behaviour, but not token-rewarded behaviour, improved more on pimozide. The patients who showed initiative and cooperated best with staff were those whose token-rewarded behaviour was most satisfactory.