Evidence for acoustic communication among bottom foraging humpback whales

Humpback whales (Megaptera novaeangliae), a mysticete with a cosmopolitan distribution, demonstrate marked behavioural plasticity. Recent studies show evidence of social learning in the transmission of specific population level traits ranging from complex singing to stereotyped prey capturing behaviour. Humpback whales have been observed to employ group foraging techniques, however details on how individuals coordinate behaviour in these groups is challenging to obtain. This study investigates the role of a novel broadband patterned pulsed sound produced by humpback whales engaged in bottom-feeding behaviours, referred to here as a ‘paired burst’ sound. Data collected from 56 archival acoustic tag deployments were investigated to determine the functional significance of these signals. Paired burst sound production was associated exclusively with bottom feeding under low-light conditions, predominantly with evidence of associated conspecifics nearby suggesting that the sound likely serves either as a communicative signal to conspecifics, a signal to affect prey behaviour, or possibly both. This study provides additional evidence for individual variation and phenotypic plasticity of foraging behaviours in humpback whales and provides important evidence for the use of acoustic signals among foraging individuals in this species

Effects of Increasing Temperature on Acoustic Advertisement in the Tettigoniidae

Acoustic communication in insects is vital for reproduction. In the family Tettigoniidae, certain features of acoustic signals are impacted by ambient temperature. The current study investigates the correlation between increased ambient temperature and signaling behavior in four species of katydids in two subfamilies under conditions that may be encountered as environmental temperatures continue to rise due to climate change. This is the first systematic investigation into the potential effects of temperature on song parameters in these four species. Individuals were tested at five different temperatures, ranging from 20 °C to 40 °C at 5°C intervals, and measurements were taken on six acoustic parameters: buzz duration, interbuzz interval (IBI) duration, number of ticks in the IBI, tick rate in the IBI, pulse rate within a buzz, and percent time spent calling. Results indicated a statistically significant effect of temperature on pulse rate, buzz duration, and interbuzz interval duration for all species tested. The percent time calling and buzz duration increased at higher temperatures in the single species in the subfamily Tettigoniinae, in contrast with the three species in the subfamily Conocephalinae which showed decreased percent time calling and reduced buzz duration in increased temperature. These results highlight the potential differences in the behavioral responses among different species to increasing global temperatures. Further research is necessary to assess the potential impact of variable calling parameters on female choice in these and other katydid species

A description of defensive hiss types in the flat horned hissing cockroach (Aeluropoda insignis)

Acoustic communication can inform studies of behaviour and phylogeny in insect species. Despite there being 4600 described species of cockroach, few studies have focused on their ability to communicate acoustically. Cockroaches have been found to produce sound in a variety of ways. Species within the tribe Gromphadorhini produce sound through modified spiracles, often referred to as hisses. Sound parameters have been described for the species Gromphadorhina portentosa and Elliptorhina chopardi. Aeluropoda insignis, within the same tribe, produces sound and is morphologically similar to these two species, but no research has been published describing its acoustic signals. Our study explores the defensive acoustic signals of this species and indicates that A. insignis is capable of producing three classes of acoustic signals (whistles, whistle–hisses and hisses) associated with defensive behaviour. Sexes differed in the entropy and the frequency of their signals, with males producing signals with lower entropy and at higher frequency than females. Future studies on acoustic communication within Blattodea could give more insight into the complexity of signals and their relationship to behavioural context

North Atlantic right whale (Eubalaena glacialis) acoustic behavior on the calving grounds

Passive acoustic monitoring is a common method for detection of endangered North Atlantic right whales. This study reports on the acoustic behavior of right whales on the winter calving grounds to assess their acoustic detectability in this habitat. In addition to known call types, previously undescribed low amplitude short broadband signals were detected from lactating females with calves. The production of higher amplitude tonal calls occurred at lower rates for lactating females than from other age/sex classes suggesting that passive acoustic monitoring may be less effective in detecting mother-calf pairs in this critical habitat area

Acoustic crypsis in communication by North Atlantic right whale mother–calf pairs on the calving grounds

Mammals with dependent young often rely on cryptic behaviour to avoid detection by potential predators. In the mysticetes, large baleen whales, young calves are known to be vulnerable to direct predation from both shark and orca predators; therefore, it is possible that mother–calf pairs may show cryptic behaviours to avoid the attention of predators. Baleen whales primarily communicate through low-frequency acoustic signals, which can travel over long ranges. In this study, we explore the potential for acoustic crypsis, a form of cryptic behaviour to avoid predator detection, in North Atlantic right whale mother–calf pairs. We predicted that mother–calf pairs would either show reduced calling rates, reduced call amplitude or a combination of these behavioural modifications when compared with other demographic groups in the same habitat. Our results show that right whale mother–calf pairs have a strong shift in repertoire usage, significantly reducing the number of higher amplitude, long-distance communication signals they produced when compared with juvenile and pregnant whales in the same habitat. These observations show that right whale mother–calf pairs rely upon acoustic crypsis, potentially to minimize the risk of acoustic eavesdropping by predators

Calls of North Atlantic right whales Eubalaena glacialis contain information on individual identity and age class

Passive acoustic monitoring is a powerful tool that allows remote detection of marine mammals through their vocalizations. While call detection provides information on species presence, additional information may be contained within the vocalizations that could provide more information regarding the demographics and/or number of individuals in a particular area based on passive acoustic detections. The North Atlantic right whale Eubalaena glacialis produces a stereotyped upswept call, termed the upcall, that is thought to function as a long-distance contact call in this species. As such, the call is likely to contain cues providing information about the individual producing it. The goal of this study was to test whether the right whale upcall could potentially encode information related to the identity and age of the caller. Using upcalls recorded from 14 known individuals through non-invasive suction cup archival acoustic tags, we demonstrate that the upcall does contain sufficient information to discriminate individual identity and age class, with average classification levels of 72.6 and 86.1%, respectively. Parameters measured from the fundamental frequency, duration, and formant structure were most important for discrimination among individuals. This study is the first step in demonstrating the feasibility of obtaining additional data from passive acoustic monitoring to aid in the conservation efforts for this highly endangered species

Noise impacts on social sound production by foraging humpback whales

The Stellwagen Bank National Marine Sanctuary, located in an urbanized coastal area off the coast of Massachusetts in the United States, serves as an important foraging habitat for North Atlantic humpback whales (Megaptera novaeangliae). During the summer , large numbers of vessels are present in the vicinity of foraging humpback whales. Humpback whales produce a wide variety of low frequency(12 hours between 2008-2012 showed decreased call rates and increased call frequency during close vessel passages. The response of the lone lactating female in the analyses was opposite of other whales, in that call rates increased during and after the increased vessel noise. This study is a first step in considering the long-term acoustic environment experienced by free-ranging humpbacks in urbanized habitats and to document the behavioral responses of individuals to shifting background noise levels

A lifetime of changing calls: North Atlantic right whales, Eubalaena glacialis, refine call production as they age

The trajectory of development and refinement of communication signals closely map physical and social development in many vertebrate species. Although marine mammals exhibit highly complex and diverse communication signals, asking similar questions about signal development can be challenging when dealing with long-lived species that roam widely at sea. North Atlantic right whales, a large baleen whale species, are intensely studied due to their endangered status. We examine whether right whale acoustic signals vary with the physical and social development of individuals from birth to adulthood using a latitudinal analysis. Data included 986 high-quality calls recorded from 49 individuals of known age spanning from 1 month to 37 years, with two individuals measured at different ages. Calls produced by calves younger than 1 year were easily distinguished by their short duration, a high degree of frequency modulation and a high percentage of nonlinear phenomena. Nonlinear phenomena within calls shifted from disorder (deterministic chaos) to increased control (biphonation and subharmonics) with increasing age. The overall percentage of calls containing nonlinear phenomena decreased with increasing age. Duration of the calls and calling bouts increased in direct correlation with age. Notably there was no clear indication of fixation in any of the measured parameters with age, with directional changes continuing over the entire age range studied. This study presents the first evidence that acoustic maturation does not stop at sexual maturity (∼9 years) in right whales and that refinement of calls continues through adulthood. Clear age-related voice cues have been documented in a range of terrestrial species with increases in call duration often reflecting increased stamina or condition in older adults. This study shows a similar trend in right whale sound production, with changes detectable across three-decade age range of available data

Evidence for acoustic communication among bottom foraging humpback whales

Humpback whales (Megaptera novaeangliae), a mysticete with a cosmopolitan distribution, demonstrate marked behavioural plasticity. Recent studies show evidence of social learning in the transmission of specific population level traits ranging from complex singing to stereotyped prey capturing behaviour. Humpback whales have been observed to employ group foraging techniques, however details on how individuals coordinate behaviour in these groups is challenging to obtain. This study investigates the role of a novel broadband patterned pulsed sound produced by humpback whales engaged in bottom-feeding behaviours, referred to here as a 'paired burst' sound. Data collected from 56 archival acoustic tag deployments were investigated to determine the functional significance of these signals. Paired burst sound production was associated exclusively with bottom feeding under low-light conditions, predominantly with evidence of associated conspecifics nearby suggesting that the sound likely serves either as a communicative signal to conspecifics, a signal to affect prey behaviour, or possibly both. This study provides additional evidence for individual variation and phenotypic plasticity of foraging behaviours in humpback whales and provides important evidence for the use of acoustic signals among foraging individuals in this species