Tail Slap Research Articles

Numerical–experimental study on the stability mechanism of tail slapping motion of supercavitation projectile

Tail slapping is considered to be a prominent mode for facilitating the movement of supercavitating projectiles underwater. Stability mechanism of the tail slapping and stability criterion of projectiles was numerically investigated in this paper. A numerical method was conducted to calculate the free flight of projectiles by combining the finite volume method, the mixture multiphase model, and a dynamic meshing scheme. The accuracy and applicability of the numerical calculation method are verified by experiments. Three typical stability modes of tail slapping motion, namely, stable, conditionally stable, and unstable, were identified through the free flight numerical simulations of projectiles with varying length-to-diameter ratios under different initial angular velocities. The stability criterion of projectiles was proposed, indicating that the tail slapping stability can be determined by analyzing the curve of the moment variation with the angle of attack at any velocity above 200 m/s. Furthermore, it was found that the stable projectiles possess inherent motion states that are exclusively determined by their structural features and are unaffected by the initial motion conditions.

Studies of the acoustic activity of white whales (in captive conditions and the possibility of their signals using to control behavior of fish in fishing process

The purpose of the work: identification of acoustic activity of belugas in conditions of aviary keeping and justification of the possibility of using their signals in fishing.The material of research was digital audio recordings of hydroacoustic signals of belugas collected from 2016 to 2018.Methods used: analysis of hydroacoustic data, visualization of the daily acoustic activity of belugas in different seasons, identification of stereotypes of acoustic behavior and characteristic signals in captive conditions and during fish hunting. Novelty: for the first time a substantiation for the possibility of using signals of one of the species of toothed whales — belugas registered in the captive conditions, to influence on the behavior of hydrobionts and solve practical problems of fishing and fish protection is given.Results: the highest acoustic activity of white whales is observed during the day and noticeably decreases at night with increase and decrease in the morning and evening hours. Maximum acoustic activity precedes the feeding of dolphins.The most common tones are those containing the fundamental frequency and harmonics. Characteristic features of the sounds are high variability of duration from 0.25 to 2.5 s, pronounced frequency components in the 500–2500 Hz spectrum zones, amplitude and frequency modulation, sound pressure levels of the signal up to 500 Pa /1 m.Acoustic activity of belugas during fish hunting and in the period preceding feeding in captive conditions, stereotypical. Typical are low-frequency frequency-modulated calls and whistles in the hearing range of fish, as well as a curtain of air bubbles and body and tail slaps. Possible ways of using beluga whale signals to increase the efficiency of fishing are proposed.Practical significance: the results of the study open up the possibility of using the signals of belugas to remotely control the movement of fish, create artificial concentrations and deterrent of hydrobionts in the intended areas.

Context of breaching and tail slapping in Indo-Pacific humpback dolphins in the northern South China Sea

Context of breaching and tail slapping in Indo-Pacific humpback dolphins in the northern South China Sea

A historical approach to describing the complex behaviour of a large species of predatory shark — Case study 2: the white shark, Carcharodon carcharias

Abstract A historical example, case study 2, is one of two cases illustrating the complexity of interactions between sharks in their natural environment. Evidence is presented that the white shark is a selective feeder, consuming seals and sea lions with high fat content yet rejecting a pelican, human, and sea otters with low fat content. After biting seals, these sharks carry them in their jaws for a prolonged time underwater to kill them through blood-loss, i.e., exsanguination. Multiple sharks compete to feed on the remaining seal carcass when it floats to the surface. The sharks perform the Tail Slap, consisting of lifting the caudal fin and splashing water toward the accompanying shark. A combatant is permitted to feed further on a seal only if the vigor and frequency of its tail slaps are greater than those of its opponent. Thus, this is an agonistic display, functioning to ward off potential competitors.

Scalloped Hammerhead (Sphyrna lewini) Movement Behavior toward Diver in Banda Waters, Maluku

Shark diving tourism opens opportunities to study shark behavior towards diver. As one of the popular attractions for the marine tourism in Indonesia, shark diving play significant role for the conservation in the eastern part of Indonesia. Banda Sea, as well as Morotai, Derawan, Raja Ampat, Nabire and Teluk Cenderawasih, Bali, Lombok, Komodo, and Gorontalo, is famous for its shark diving attraction. Despite its famous status as a tourism attraction, little is known about the behavior of scalloped hammerhead shark during the interaction with Self-Contained Underwater Breathing Apparatus (SCUBA) diver. The information of scalloped hammerhead shark movement behavior during interaction with SCUBA diver is important for developing ecological assessment, safe diving practice, and shark tourism carrying capacity. This research involves DOV (Diver Operated Video) to record the movement patterns of shark while interacting with SCUBA Diver. Evaluation of approximately 457 photos and 32 videos of the Sphyrna lewini during 14 days of observations has been analyzed during SCUBA diving shows the most common shark agonistic display: pectoral fins depression - apart from other displays such as tail slapping, flank displaying, charging, snout raise, and jaw gapping. It also reveals three (3) new shark agonistic postures which were never been recorded previously: charging, snout raise, and jaw gapping. This study showed that there are consistent behaviors observed while meeting with SCUBA divers and this may be beneficial for development of safety diving management, as well as conservation efforts.

Load and motion behaviors of ogive-nosed projectile during high-speed water entry with angle of attack

Hazardous loads exist not only during the water impact but during the entire high-speed water entry process. This article systematically investigates the load behavior of an ogive-nosed projectile during the entire process from the impact to the full wetting by experimental and numerical methods. It is found that the hazardous loads during the entire water entry process mainly exist in the three stages of water impact, tail slap and beginning of wetting. The formation mechanisms of hazardous loads are revealed. The initial angle of attack (IAA) within 8° in absolute value has little influence on the axial load, with the maximum difference of 4 g. In contrast, the effect of the IAA on the radial load is significant in terms of the direction, the peak, the beginning time of wetting, and the magnitude after wetting. The peak radial load of the tail slap reaches 3.7 times the peak axial impact load at the IAA of −8°. When the IAA is large (±8°), serious deflection of the trajectory occurs, such as the water exit at +8° and the backward movement at −8°; the angle of attack eventually diverges; and the pitch angle change reaches over 200°. The results provide helpful guidance in effectively identifying all hazardous loads during the entire water entry process and clearly understanding the motion behavior under the action of the loads.

Observations of parturition in humpback whales (Megaptera novaeangliae) and occurrence of escorting and competitive behavior around birthing females

AbstractDocumented cases of cetacean births in the wild are rare. While there are currently no direct observations of a complete humpback whale birth, they are one of the few large whale species where observers have been present during a birthing event. We compiled eye‐witnessed accounts of all known humpback whale birthing events and found nine well‐documented cases globally (three published and six “new” unpublished). In two‐thirds of the accounts another “escort” whale was present and in close association with the birthing female, and of these, most cases involved multiple escorts (n = 4). We describe details of birthing events, including mother, neonate and escort(s)’ behavior, neonate appearance, and discuss reasons for escort presence during parturition. We note that immediately postpartum: (1) blood and/or placenta were not always apparent during above water observations, (2) females often (but not always) supported calves at the surface, (3) constant travel and tail slapping were typical neonate behaviors, (4) two cases of temporary calf abandonment (<10 min), and (5) evidence of shark scavenging (of placenta) and possible predation attempts (of neonate). Lastly, we suggest curled tail flukes as an additional trait for identifying neonates and note that fetal folds are not always evident in newborn humpback whales.

Tourist Knowledge, Pro-Conservation Intentions, and Tourist Concern for the Impacts of Whale-Watching in Las Perlas Archipelago, Panama

Whale watching has become an important economic activity for many coastal areas where whales aggregate at certain times of year. Las Perlas Archipelago in Panama is a breeding ground for humpback whales, where the numbers of both visitors and tour operators have increased in recent years with little compliance and enforcement of regulations. Nevertheless, there is potential to improve whale-watching management at this site and its use as a tool for education and conservation awareness. Our objective was to assess tourist knowledge, perceptions and pro-conservation attitudes related to whale watching and how this activity is managed in Las Perlas. One hundred and eleven tourists were surveyed in the summer of 2019 after they participated in whale−watching tours. Overall, respondents had little knowledge about whales and their conservation before a whale-watching trip. However, after the excursion, tourists felt they had learned more about whale biology and the regulations for whale-watching. Trip satisfaction after whale-watching activities was higher when whale behaviors, including breaching and tail slaps, were observed. Respondents expressed low satisfaction when there was an excessive number of boats around a whale-sighting. Concern for lack of compliance seemed to be associated with whale-watching operations that onboard tour guides. This study highlights the importance of whale watching as a tool for promoting whale conservation through education and the need to improve the enforcement of existing regulations and visitor monitoring to reduce potential negative impacts of whale-watching.

Assessment on the effectiveness of vessel-approach regulations to protect cetaceans in Australia: A review on behavioral impacts with case study on the threatened Burrunan dolphin (Tursiops australis).

Vessels cause considerable disturbance to cetaceans world-wide, with potential long-term impacts to population viability. Here we present a comprehensive review of vessel impacts to cetacean behavior in Australian waters (2003–2015), finding inadequate protections to be in place. The majority of these studies found trends of decreased animal travel and resting behavioral states as well as low compliance to regulations, and they recommended further regulatory action such as greater enforcement or monitoring, or passive management strategies. As a case study, we conducted the first field assessment of vessel compliance with the Wildlife (Marine Mammal) Regulations 2009 in Gippsland Lakes, Australia, and provide the first assessment of the endangered Gippsland Lakes Burrunan dolphin (Tursiops australis) population’s behavioral ecology. Dolphin behavior and vessel regulation compliance data were collected during boat-based surveys of Gippsland Lakes from July 2017 to January 2018, with a total of 22 dolphin group sightings resulting in 477 five-minute point samples. 77% of dolphin sightings involved vessel interactions (within 400 m), and 56 regulation breaches were observed. These breaches were most severe in summer (mean = 4.54 breaches/hour). Vessels were found to alter dolphin behavior before, during, and after interactions and regulation breaches, including increased mating (mate guarding) and milling behavioral states, and increased ‘fish catch’, ‘high leap’ and ‘tail slap’ behavioral events. These behavioral changes may indicate masking of the dolphins' acoustic communication, disturbance of prey, increased dolphin transition behaviors, and/or induced stress and changes to group structure (including increased mate guarding). While our results provide evidence of short-term altered behavior, the potential for long-term effects on population dynamics for this threatened species is high. In the context of reported inadequate cetacean protection Australia-wide, our management recommendations include greater monitoring and enforcement, and the utilisation of adaptive management.

AGE, SEX CLASS, AND PREY ABUNDANCE INFLUENCE THE FREQUENCY AND TYPE OF PERCUSSIVE BEHAVIOR IN THE SOUTHERN RESIDENT KILLER WHALE (ORCINUS ORCA) POPULATION AT LIME KILN POINT STATE PARK

The endangered Southern Resident Killer Whale (Orcinus orca, SRKW) is an iconic species in the Pacific Northwest. Although many ecological aspects of this population have been studied, why SRKW perform above-surface “percussive” behavior such as breaching, cartwheeling, pectoral-fin slapping, tail lobbing, and dorsal-fin slapping remains unclear. In the present study, we observed SRKW in Haro Strait, Washington, to evaluate trends in percussive behavior by age and sex class during the summer of 2016, and used long-term data (1996–2016) to compare the relationship between the seasonal frequency of percussive behaviors and the abundance of Chinook Salmon (Oncorhynchus tshawytscha) the primary food source of SRKW. Over the summer season in 2016, we documented 24 encounters involving percussive behavior. We found a significant difference between ages and sexes in the rate of percussive behaviors performed, with adult females performing the most behaviors among these groups, and tail slaps comprising the most frequent behavior performed. We also found a significant positive relationship between the rate of percussive behaviors and Chinook Salmon abundance in the Salish Sea over the past 2 decades. These findings present a preliminary investigation into the potential for behavioral observations to serve as indicators of population-level health or behavioral trends, which could be important for this population's conservation.

Surface activity of Humpback whales Megaptera novaeangliae (Cetacea, Mysticeti) on the northern coast of Bahia, Brazil

Surface activities of humpback whale groups were studied during the reproductive seasons of 2008, 2009 and 2010 on the northern coast of Bahia State, Brazil, near the district of Praia do Forte. The level of surface activity exhibited by 342 groups of whales was evaluated according to the sea state (measured on the Beaufort scale) and cloud coverage. Five behaviours were recorded: breaching, head slapping, tail slapping, pectoral flipper slapping and tail breaching. Most of the sightings occurred with a sea state classified on the Beaufort scale as 2, and with a cloud coverage of 26 to 50%. The most recorded level of surface activity was pectoral flipper slapping. The results showed that humpback whale behaviours do not seem to be influenced by the sea state or by cloud coverage.

Integument-based inferences on the swimming ability and prey hunting strategy of the bigeye thresher shark, Alopias superciliosus (Lamniformes: Alopiidae)

Alopias is a group of lamniform sharks characterized by a highly elongate caudal fin with three known extant species: Alopias pelagicus (pelagic thresher shark), Alopias superciliosus (bigeye thresher shark), and Alopias vulpinus (common thresher shark). Alopias pelagicus and A. vulpinus are considered fast swimmers and use their caudal fin to hunt for small schooling fish by stunning them, but this feeding behavior has never been directly observed for A. superciliosus. In this study, we examined four integumentary variables of selected fast swimming (e.g. A. pelagicus, A. vulpinus, and Lamna) and slow swimming (e.g. Mitsukurina and Megachasma) lamniform sharks to determine whether A. superciliosus is a fast swimmer or a slow swimmer. Our data indicate that A. superciliosus is a slow swimming lamniform, but it probably employs a simple laterally directed tail slap to capture its prey. Overall, our study points to an interpretation that A. superciliosus is an ambush predator, rather than an active prey-pursuing hunter. Mapping of scale data onto previously published phylogenetic trees indicate that slow swimming is a plesiomorphic condition in the order Lamniformes. Our work represents the most extensive comparative study of the morphology and variation of integumentary structures, especially placoid scales, conducted so far for Lamniformes.

Behaviour reactions of bottlenose dolphins (Tursiops truncatus) to multirotor Unmanned Aerial Vehicles (UAVs)

Unmanned aerial vehicles (UAVs) represent a novel and cost effective research tool to investigate cetacean behaviour, as conventional aircraft are expensive, limited in the altitude they can fly at and potentially disturb sensitive wildlife. In addition, the aerial observation from the UAVs allows assessment of cetacean behaviour from an advantageous perspective and can collect high spatial and temporal resolution data, providing the opportunity to gather accurate data about group size, age class and subsurface behaviour. However, concerns have been raised about the potential risks of disturbance to animals caused by the UAV’s visual and acoustic stimuli. Boat-based surveys were conducted to assess the short-term behavioural responses of resting bottlenose dolphins (Tursiops truncatus) to a lightweight Vertical take-off and landing (VTOL) UAV flown at 10, 25, and 40 m altitude. Changes in group swim direction and frequencies of surface and aerial behavioural events were recorded from an anchored research vessel before (control) and during the aerial survey. The number of reorientation and tail slap events increased significantly between controls and flights when the UAV was flown at 10 m over the animals. In contrast, no significant differences were detected when the aircraft was flown at 25 and 40 m altitude. However, a precautionary approach is recommended for research applications requiring lower flight altitudes, with further research recommended to assess how different cetacean species and age class may respond to the UAV presence.

Modeling of the Tail Slap for an Underwater Projectile within Supercavitation

Detailed process of the tail slap for an underwater projectile in supercavitation is studied in this paper. Firstly, the horizontal equation of motion for the projectile and a dynamic model of the projectile’s tail slap are introduced through a mathematical derivation, including a simple harmonic motion model of the projectile within the supercavitation layer and the tail slap reflection movement model inside the cavity. Subsequently, the MATLAB software package is used to model the projectile’s motion. Characteristics for force from the projectile tail on the water layer during a single tail slap and the behavior of the projectile’s angular motion as well as the characteristics of projectile tail motion through multiple tail slaps are investigated. It is found that the force magnitude of the water on the projectile tail decreases gradually while the relative motion angle of the projectile tail into the water layer and the contact time increase obviously as the projectile repeatedly slaps the cavity interface. When the projectile velocity decreases into a certain range, i.e., less than 50 m/s, the contact time of the tail in the water layer increases dramatically, and the supercavitation can tend to collapse and lead to unstable projectile motion. With increasing lateral deviation and angular velocity of the projectile tail, the number of tail slaps and the angle of reflection both increase significantly. In the case of supercavitation, the parameters of different tail slap points tend to be stable with time.

To buzz or burst-pulse? The functional role of Heaviside's dolphin, Cephalorhynchus heavisidii, rapidly pulsed signals

Four groups of toothed whales have independently evolved to produce narrowband high-frequency (NBHF) echolocation signals (i.e. clicks) with a strikingly similar waveform and centroid frequency around 125 kHz. These signals are thought to help NBHF species avoid predation by echolocating and communicating at frequencies inaudible to predators, a form of acoustic crypsis. Heaviside's dolphins produce NBHF echolocation clicks in trains and often in rapid succession in the form of buzzes. In addition, a second click type with a lower frequency and broader bandwidth was recently described, typically emitted in rapid succession in the form of burst-pulses. We investigated the relationship between buzz and burst-pulse signals and both surface behaviour (foraging, ‘interacting with the kayak’ and socializing) and group size, using a multivariable regression on the signal occurrence and signal count data. Signal occurrence and counts were not related to group size in the regression analysis. Burst-pulses were strongly linked to socializing behaviour, occurring more often and more frequently during socializing and much less during foraging. Buzz vocalizations were not strongly linked to a specific behaviour although there was some evidence of an increase in production during foraging and socializing. In addition, individual level production rates of buzzes during foraging and socializing, and burst-pulses during socializing decreased with increasing group size. Temporally patterned burst-pulse signals were also identified, often occurring within a series of burst-pulses and were directly linked to specific events such as aerial leaping, backflipping, tail slapping and potential mating. Our findings suggest Heaviside's dolphins have a more complex communication system based on pulsed vocalizations than previously understood, perhaps driven by the need to facilitate the social interactions of this species.

Dolphins that help us fish also have an odd accent

All bottlenose dolphins whistle, but those that work with humans have a distinctive way of doing it. This unusual calling style may help them recognise each other. In the seas off Laguna, Brazil, fishers stand in a line in waist-deep water or wait in canoes while, farther out, bottlenose dolphins chase shoals of mullet to the shore. The fishers can't see the fish in the murky water, so they wait for the dolphins to give a signal--like an abrupt dive or tail slap--before casting their nets. Dolphins likely reap similar benefits, says Mauricio Cantor of the Federal University of Santa Catarina in Brazil

Icelandic herring-eating killer whales feed at night

Herring-eating killer whales debilitate herring with underwater tail slaps and likely herd herring into tighter schools using a feeding-specific low-frequency pulsed call (‘herding’ call). Feeding on herring may be dependent upon daylight, as the whales use their white underside to help herd herring; however, feeding at night has not been investigated. The production of feeding-specific sounds provides an opportunity to use passive acoustic monitoring to investigate feeding behaviour at different times of day. We compared the acoustic behaviour of killer whales between day and night, using an autonomous recorder deployed in Iceland during winter. Based upon acoustic detection of underwater tail slaps used to feed upon herring we found that killer whales fed both at night and day: they spent 50% of their time at night and 73% of daytime feeding. Interestingly, there was a significant diel variation in acoustic behaviour. Herding calls were significantly associated with underwater tail slap rate and were recorded significantly more often at night, suggesting that in low-light conditions killer whales rely more on acoustics to herd herring. Communicative sounds were also related to underwater tail slap rate and produced at different rates during day and night. The capability to adapt feeding behaviour to different light conditions may be particularly relevant for predator species occurring in high latitudes during winter, when light availability is limited.

Low-frequency signals produced by Northeast Atlantic killer whales (Orcinus orca).

Killer whale acoustic behavior has been extensively investigated; however, most studies have focused on pulsed calls and whistles. This study reports the production of low-frequency signals by killer whales at frequencies below 300 Hz. Recordings were made in Iceland and Norway when killer whales were observed feeding on herring and no other marine mammal species were nearby. Low-frequency sounds were identified in Iceland and ranged in duration between 0.14 and 2.77 s and in frequency between 50 and 270 Hz, well below the previously reported lower limit for killer whale tonal sounds of 500 Hz. Low-frequency sounds appeared to be produced close in time to tail slaps, which are indicative of feeding attempts, suggesting that these sounds may be related to a feeding context. However, their precise function is unknown, and they could be the by-product of a non-vocal behavior rather than a vocal signal deliberately produced by the whales. Although killer whales in Norway exhibit similar feeding behavior, this sound has not been detected in recordings from Norway to date. This study suggests that, like other delphinids, killer whales produce low-frequency sounds, but further studies will be required to understand whether similar sounds exist in other killer whale populations.

Acoustic Communication in Butterflyfishes: Anatomical Novelties, Physiology, Evolution, and Behavioral Ecology.

Coral reef fishes live in noisy environments that may challenge their capacity for acoustic communication. Butterflyfishes (Family Chaetodontidae) are prominent and ecologically diverse members of coral reef communities worldwide. The discovery of a novel association of anterior swim bladder horns with the lateral line canal system in the genus Chaetodon (the laterophysic connection) revealed a putative adaptation for enhancement of sound reception by the lateral line system and/or the ear. Behavioral studies show that acoustic communication is an important component of butterflyfish social behavior. All bannerfish (Forcipiger, Heniochus, and Hemitaurichthys) and Chaetodon species studied thus far produce several sound types at frequencies of <1 to >1000 Hz. Ancestral character state analyses predict the existence of both shared (head bob) and divergent (tail slap) acoustic behaviors in these two clades. Experimental auditory physiology shows that butterflyfishes are primarily sensitive to stimuli associated with hydrodynamic particle accelerations of ≤500 Hz. In addition, the gas-filled swim bladder horns in Chaetodon are stimulated by sound pressure, which enhances and extends their auditory sensitivity to 1700-2000 Hz. The broadband spectrum of ambient noise present on coral reefs overlaps with the frequency characteristics of their sounds, thus both the close social affiliations common among butterflyfishes and the evolution of the swim bladder horns in Chaetodon facilitate their short-range acoustic communication. Butterflyfishes provide a unique and unexpected opportunity to carry out studies of fish bioacoustics in the lab and the field that integrate the study of sensory anatomy, physiology, evolution, and behavioral ecology.

The effect of vessel noise on humpback whale, Megaptera novaeangliae, communication behaviour

The modification of communication signals in response to a changing noise environment has been demonstrated in many terrestrial species, although there are comparatively fewer studies in marine mammals. It is rare, even in terrestrial studies, that the response to an anthropogenic source of noise is compared with a natural source of noise in order to evaluate how animals cope with anthropogenic noise. Humpback whales produce two different types of communication signal other than song: vocal sounds and nonvocal sounds from surface-generated behaviours (breaches, pectoral slapping, tail slapping). In this study, the response of humpback whales to noise dominated by wind (a natural source of noise from breaking waves) was compared with the response to noise dominated by a passing vessel (anthropogenic noise). There were no significant changes in frequency or duration of two common vocal sounds in response to increases in either wind or vessel noise. As with previous studies, humpback whale groups, in response to increasing wind-dominated noise, increased their vocal source level and switched from using primarily vocal sounds to surface-generated sounds in their repertoire. In response to an increase in vessel noise, groups did neither. The proportion of nonvocal sounds in their repertoire was significantly correlated with wind speed (and therefore wind noise) regardless of vessel noise suggesting this response is specific to increased wind noise. However, vocal source levels were lower than expected in vessel noise, suggesting a potential for signal masking in these groups. This comparison of response to two different sources of noise shows that humpback whales may not be able to cope with an increase in anthropogenic noise in the same way they cope with an increase in natural noise. The results highlight the benefits of using the response to a natural source to assess the potential effects of anthropogenic noise on animal communication.