Mark Bee

University of Minnesota Twin Cities | UMN · Department of Ecology, Evolution and Behaviour

Sound source perception refers to the auditory system's ability to parse incoming sensory information into coherent representations of distinct sound sources in the environment. Such abilities are no doubt key to successful communication in many taxa, but we know little about their function in animal communication systems. For anuran amphibians (fr...

Animals often use acoustic signals to communicate in groups or social aggregations in which multiple individuals signal within a receiver's hearing range. Consequently, receivers face challenges related to acoustic interference and auditory masking that are not unlike the human cocktail party problem, which refers to the problem of perceiving speec...

Albert Feng was a pioneer in the field of auditory neuroethology who used frogs to investigate the neural basis of spectral and temporal processing and directional hearing. Among his many contributions was connecting neural mechanisms for sound pattern recognition and localization to the problems of auditory masking that frogs encounter when commun...

Amphibians have inner ears with two sensory papillae tuned to different frequency ranges of airborne sounds. In frogs, male advertisement calls possess distinct spectral components that match the tuning of one or both sensory papillae. Female preferences for the spectral content of advertisement calls can depend on signal amplitude and can vary amo...

Albert Feng pioneered the study of neuroethology of sound localization in anurans by combining behavioral experiments on phonotaxis with detailed investigations of neural processing of sound direction from the periphery to the central nervous system. The main advantage of these studies is that many species of female frogs readily perform phonotaxis...

Multimodal communication signals consist of two or more distinct components produced in different sensory modalities and transduced by receivers using multiple sensory systems. One evolutionary trajectory by which incipient multimodal signals may arise is when receivers are selected to attend both to a well-established signal and a cue in a differe...

Many animals use signals to recognize familiar individuals but risk making mistakes because the signal properties of different individuals often overlap. Furthermore, outcomes of correct and incorrect decisions yield different fitness payoffs, and animals incur these payoffs at different frequencies depending on interaction rates. To understand how...

Noisy social environments constrain human speech intelligibility in two primary ways: spectro-temporal overlap between signals and noise reduces speech audibility (“energetic masking”) and noise interferes with processing the informative features of otherwise audible speech (“informational masking”). To date, informational masking has not been inve...

Significance Beyond sugars, many types of nectar solutes play important ecological roles; however, the molecular basis for the diversity of nectar composition across species is less explored. One rare trait among flowering plants is the production of colored nectar, which may function to attract and guide prospective pollinators. Our findings indic...

Sexual traits that promote species recognition are important drivers of reproductive isolation, especially among closely related species. Identifying neural processes that shape species differences in recognition is crucial for understanding the causal mechanisms of reproductive isolation. Temporal patterns are salient features of sexual signals wi...

Animals recognize familiar individuals to perform a variety of important social behaviors. Social recognition is often mediated by communication between signalers who produce signals that contain identity information and receivers who categorize these signals based on previous experience. We tested two hypotheses about adaptations in signalers and...

Many animals use signals, such as vocalizations, to recognize familiar individuals. However, animals risk making recognition mistakes because the signal properties of different individuals often overlap due to within-individual variation in signal production. To understand the relationship between signal variation and decision rules for social reco...

Sexual traits that promote species recognition are important drivers of reproductive isolation, especially among closely related species. Identifying neural processes that shape species differences in recognition is crucial for understanding the causal mechanisms of reproductive isolation. Temporal patterns are salient features of sexual signals th...

Synopsis Most animals experience reproductive transitions in their lives; for example, reaching reproductive maturity or cycling in and out of breeding condition. Some reproductive transitions are abrupt, while others are more gradual. In most cases, changes in communication between the sexes follow the time course of these reproductive transitions...

Animals recognize familiar individuals to perform a variety of important social behaviors. Social recognition is often mediated by communication between signalers who produce signals that contain identity information and receivers who categorize these signals based on previous experience. We tested two hypotheses about adaptations in signalers and...

Nesocodon mauritianus (Campanulaceae) produces a blood-red nectar that has been proposed to serve as a visual attractant for pollinator visitation. Here we show that the nectar’s red color is derived from a novel alkaloid termed nesocodin. The first nectar produced is acidic and pale yellow in color, but slowly becomes alkaline before taking on its...

The genus Raorchestes is a large radiation of Old World tree frogs for which the Western Ghats in Peninsular India is the major center for origin and diversification. Extensive studies on this group during the past two decades have resolved long-standing taxonomic confusions and uncovered several new species, resulting in a four-fold increase in th...

Environmental noise is a major source of selection on animal sensory and communication systems. The acoustic signals of other animals represent particularly potent sources of noise for chorusing insects, frogs, and birds, which contend with a multi-species analog of the human "cocktail party problem" (i.e., our difficulty following speech in crowds...

Glucocorticoids (GCs) are rarely studied in the context of female mate choice, despite the expression of receptors for these products in sexual, sensory and decision-making brain areas. Here we investigated the effects of GC concentrations on three aspects of female sexual behavior in breeding Cope's gray treefrogs (Hyla chrysoscelis): proceptivity...

Navigating social relationships frequently rests on the ability to recognize familiar individuals using phenotypic characteristics. Across diverse taxa, animals vary in their capacities for social recognition, but the ecological and social sources of selection for recognition are often unclear. In a comparative study of two closely related species...

According to Weber's law, discrimination between stimuli is based upon the proportional difference (ΔI/I), not the absolute difference (ΔI), between their magnitudes (I). How such nonlinear processing of signal information by receivers impacts the effectiveness of communication and drives patterns of signal evolution remains poorly understood. To i...

No PDF available ABSTRACT The University of Minnesota (UMN) has graduate programs that span the areas of Animal Bioacoustics, Psychological and Physiological Acoustics, and Speech Communication. Degrees are offered in Psychology (Ph.D.), Speech-Language-Hearing Sciences (M.A. in speech-language pathology, Au.D., and Ph.D. in speech-language-hearing...

For many animals, navigating their environment requires an ability to organize continuous streams of sensory input into discrete 'perceptual objects' that correspond to physical entities in visual and auditory scenes. The human visual and auditory systems follow several Gestalt laws of perceptual organization to bind constituent features into coher...

Amphibians are unique among extant vertebrates in having middle ear cavities that are internally coupled to each other and to the lungs. In frogs, the lung-to-ear sound transmission pathway can influence the tympanum's inherent directionality, but what role such effects might play in directional hearing remain unclear. In this study of the American...

Amphibians are unique among extant vertebrates in having middle ear cavities that are internally coupled to each other and to the lungs. In frogs, the lung-to-ear sound transmission pathway can influence the tympanum’s inherent directionality, but what role such effects might play in directional hearing remain unclear. In this study of the American...

Noise impairs signal perception and is a major source of selection on animal communication. Identifying adaptations that enable receivers to cope with noise is critical to discovering how animal sensory and communication systems evolve. We integrated biophysical and bioacoustic measurements with physiological modeling to demonstrate that the lungs...

Optimal mate choice based on the assessment of communication signals can be constrained by multiple sources of noise. One well-known impediment to acoustically guided mating decisions is the ambient noise created by multiple signaling individuals in large social groups, in which ambient noise can mask signals by impairing signal recognition and dis...

Accurately quantifying animal activity and movements is of fundamental importance in a broad range of disciplines, from biomedical research to behavioral ecology. In many instances, it is desirable to measure natural movements in controlled sensory environments in which the animals are not physically or chemically restrained, but their movements ar...

Like political stump speeches and product advertisements, animal signals are highly repetitive and function to persuade receivers to adopt behaviors benefiting the signaler. And like potential constituents and consumers, receivers assess signals to inform their behavioral decisions. However, inconsistency in sexual signals is widespread and potenti...

Navigating social relationships frequently rests on the ability to recognize familiar individuals using phenotypic characteristics. Across diverse taxa, animals vary in their capacities for social recognition but the ecological and social sources of selection for recognition are often unclear. In a comparative study of two closely related species o...

Synopsis Anurans (frogs and toads) have served as models for identifying relevant information in acoustic communication signals, and how it is represented and processed in their auditory systems. Anurans provide unparalleled stability as neurophysiological preparations, enabling in vivo whole-cell recordings and focal pharmacological manipulations....

Male secondary sexual traits potentially function as indicators of direct or indirect fitness benefits to females. Direct benefits, such as paternal care, may be especially important to females in species with biparental care. In an experimental field study of the golden rocket frog (Anomaloglossus beebei), a Neotropical species with biparental car...

Synthetic, computer-generated signals are widely used in playback studies of animal acoustic communication. Depending on the goals of the experimenter, they can offer several significant advantages over playbacks of recordings of edited or unedited natural signals. However, there are few ‘off the shelf’ software options for the bioacoustician inter...

Both behavioral receptivity and neural sensitivity to acoustic mate attraction signals vary across the reproductive cycle, particularly in seasonally breeding animals. Across a variety of taxa receptivity to signals increases, as does peripheral auditory sensitivity, as females transition from a non-breeding to breeding condition. We recently docum...

Animal sexual displays are typically repeated over time and consist of components that are also repeated within a display, creating potential for within-individual variation in signal production. Across taxa, patterns of variation in and female preferences for temporal properties of signals are well documented, but data describing how within-indivi...

In seasonal breeders, there are behavioral, endocrine, and neural adaptations that promote the sexual receptivity of females and tune their sensory systems to detect and discriminate among advertising males and to successfully copulate. What happens immediately after this key life history event is unclear, but this transitional moment offers a wind...

In many tropical frogs, offspring development and survival potentially depend on microhabitat features associated with sites that parents select for oviposition and tadpole rearing. We investigated the importance of microhabitat features in the selection of oviposition sites versus tadpole rearing sites, as well as in determining offspring survival...

Many animals communicate acoustically in large social aggregations. Among the best studied are frogs, in which males form large breeding choruses where they produce loud vocalizations to attract mates. Although chorus noise poses significant challenges to communication, it also possesses features, such as comodulation in amplitude fluctuations, tha...

Early in the twentieth century, the Gestalt psychologists outlined principles governing the ability of the human visual system to construct integrated percepts of objects in visual scenes. By the close of the twentieth century, ample evidence suggested that the human auditory system follows similar principles of perceptual organization. Several Ges...

Some territorial animals recognize familiar neighbours and are less aggressive to established neighbours than they are to strangers. This form of social recognition produces a ‘dear enemy’ effect, which may allow animals to reduce the costs of territory defence. The dear enemy effect is thought to reflect either the decreased threat posed by neighb...

In acoustically communicating animals such as anurans and orthopterans, individual signalers can display remarkable variation in signal traits, even within a single bout of calling. This within-individual variation has the potential to “mask” the between-individual variation that is the target of sexual selection. Thus, receivers may not always be...

In frogs, sound localization is facilitated by the directionality of their internally coupled ears, which are connected through the mouth cavity and Eustachian tubes. Acoustic input through the frog’s body wall and lungs also shapes the ear’s directionality. One hypothesized function of the lung input is to enhance directional hearing to improve lo...

In Cope’s gray treefrog (Hyla chrysoscelis), the pulse rate of advertisement calls is a species recognition cue. This temporal information is redundant across two spectral bands in the call’s bimodal spectrum that are primarily transduced by different inner ear papillae. Previous studies have shown that some neurons in the frog auditory midbrain ar...

Diverse animals communicate using multicomponent signals. How a receiver’s central nervous system integrates multiple signal components remains largely unknown. We investigated how female green treefrogs (Hyla cinerea) integrate the multiple spectral components present in male advertisement calls. Typical calls have a bimodal spectrum consisting of...

The University of Minnesota offers a wide variety of graduate programs related to acoustics, primarily in the areas of Speech Communication, Psychological and Physiological Acoustics, and Animal Bioacoustics. Degree programs include Psychology (Ph.D.), Speech-Language-Hearing Sciences (M.A., Au.D., and Ph.D.), Biomedical Engineering (M.S. and Ph.D....

Animal signals are complex, comprising multiple components that receivers may use to inform their decisions. Components may carry information of differing value to receivers, and selection on one component could modulate or reverse selection on another, necessitating a multivariate approach to estimating selection gradients. However, surprisingly f...

Diverse animals use environmental sounds to orient in ecological soundscapes. Yet, we know little about how acoustic information use drives behavioral decisions to orient. Although the sound generated by frog choruses functions as noise that impairs signal reception by listeners in the aggregation, it can also serve as an informative ecological sig...

Noise is a ubiquitous source of errors in all forms of communication [1]. Noise-induced errors in speech communication, for example, make it difficult for humans to converse in noisy social settings, a challenge aptly named the "cocktail party problem" [2]. Many nonhuman animals also communicate acoustically in noisy social groups and thus face bio...

Some territorial animals display a form of social recognition in which they direct low levels of aggression towards established neighbours, but maintain greater readiness to respond aggressively towards unfamiliar individuals. In many taxa, such as songbirds, this so-called ‘dear enemy’ effect involves discrimination between neighbours and stranger...

Acoustically-signaling animals such as crickets may experience interference from environmental noise, a particular concern given the rise in anthropogenic or other novel sources of sound. We examined the potential for acoustic interference of female phonotaxis to calling song in the Pacific field cricket (Teleogryllus oceanicus) by invasive coqui f...

Acoustic signaling plays key roles in mediating many of the reproductive and social behaviors of anurans (frogs and toads). Moreover, acoustic signaling often occurs at night, in structurally complex habitats, such as densely vegetated ponds, and in dense breeding choruses characterized by high levels of background noise and acoustic clutter. Funda...

Informational masking (IM) interferes with speech perception in the presence of multiple talkers. However, its impact on vocal communication in other animals has received little attention. This talk will present behavioral and neurophysiological evidence—much of it preliminary, circumstantial, or both—suggesting that frogs are also susceptible to I...

Anurans show the highest diversity in reproductive modes of all vertebrate taxa, with a variety of associated breeding behaviours. One striking feature of anuran reproduction is amplexus. During this process, in which the male clasps the female, both individuals’ cloacae are juxtaposed to ensure successful external fertilization. Several types of a...

Anurans show the highest diversity in reproductive modes of all vertebrate taxa, with a variety of associated breeding behaviours. One striking feature of anuran reproduction is amplexus. During this process, in which the male clasps the female, both individuals’ cloacae are juxtaposed to ensure successful external fertilization. Several types of a...

In contrast to humans and other mammals, many animals have internally coupled ears that function as inherently directional pressure-gradient receivers. Two important but unanswered questions are to what extent and how do animals with such ears exploit spatial cues in the perceptual analysis of noisy and complex acoustic scenes? This study of Cope's...

Empirical studies of contest behavior in anuran amphibians date back to the birth of behavioral ecology. Over the intervening years, considerable evidence has accumulated regarding two specific contest-related behaviors: the assessment and recognition of competitive rivals based on the exchange of vocal signals. In the first part of this chapter, w...

This edited volume on Psychological Mechanisms in Animal Communication highlights research on the sensory, perceptual, and cognitive mechanisms that underlie signaling and receiving. It brings together researchers working on a broad range of conceptual questions in diverse animal systems and using an assortment of empirical tools. Collectively, the...

Learning to recognize and categorize other individuals is a cornerstone of animal social behavior. By learning about individually distinctive signal properties, receivers can perceptually discriminate among conspecifics to direct appropriate behaviors toward particular individuals. One context for social recognition arises from contests over territ...

This book analyzes the psychological mechanisms critical to animal communication. The topics covered range from single neurons to broad-scale phylogenetic patterns, shedding new light on the sensory, perceptual, and cognitive processes that underlie the communicative behaviors of signalers and receivers alike. In so doing, the contributing authors...

In humans and some nonhuman vertebrates, a sound containing brief silent gaps can be rendered perceptually continuous by inserting noise into the gaps. This so-called "continuity illusion" arises from a phenomenon known as "auditory induction" and results in the perception of complete auditory objects despite fragmentary or incomplete acoustic info...

Anurans communicate using a repertoire of acoustic signals that can be classified as different call types based on differences in both their acoustic properties and the contexts in which they are produced. Descriptions of these repertoires represent a key first step towards understanding the vocal behaviour of any species and provide a critical fou...

Can you remember the last time you were awake but heard nothing? No people. No animals. No machines. No music. Nothing. If you are like me (and like most people with normal hearing), you probably have difficulty recalling an instance of hearing absolutely nothing at all. Someone or something somewhere is making sound — making noise. The inescapabil...

Sensory systems function most efficiently when processing natural stimuli, such as vocalizations, and it is thought that this reflects evolutionary adaptation. Among the best-described examples of evolutionary adaptation in the auditory system are the frequent matches between spectral tuning in both the peripheral and central auditory systems of an...

Animal acoustic communication often takes the form of complex sequences, made up of multiple distinct acoustic units. Apart from the well-known example of birdsong, other animals such as insects, amphibians, and mammals (including bats, rodents, primates, and cetaceans) also generate complex acoustic sequences. Occasionally, such as with birdsong,...

Humans exploit environmental regularities in sounds to perceptually bind acoustic energy occurring simultaneously at different frequencies. Such abilities influence vowel perception in speech and timbre perception in music. Other animals solve similar binding problems in the recognition of species-specific acoustic signals. Moreover, they commonly...

Anuran ears function as pressure difference receivers, and the amplitude and phase of tympanum vibrations are inherently directional, varying with sound incident angle. We quantified the nature of this directionality for Cope's gray treefrog, Hyla chrysoscelis. We presented subjects with pure tones, advertisement calls, and frequency-modulated swee...

The ability to reliably locate sound sources is critical to anurans, which navigate acoustically complex breeding choruses when choosing mates. Yet, the factors influencing sound localization performance in frogs remain largely unexplored. We applied two complementary methodologies, open and closed loop playback trials, to identify influences on lo...

Quantitative descriptions of animal vocalizations can inform an understanding of their evolutionary functions, the mechanisms for their production and perception, and their potential utility in taxonomy, population monitoring, and conservation. The goal of this study was to provide the first acoustical and statistical analysis of the advertisement...

Our knowledge of the hearing abilities of frogs and toads is largely defined by work with a few well-studied species. One way to further advance comparative work on anuran hearing would be greater use of minimally invasive electrophysiological measures, such as the auditory brainstem response (ABR). This study used the ABR evoked by tones and click...

The perceptual analysis of acoustic scenes involves binding together sounds from the same source and separating them from other sounds in the environment. In large social groups, listeners experience increased difficulty performing these tasks due to high noise levels and interference from the concurrent signals of multiple individuals. While a sub...

Choruses of acoustically signaling frogs and toads are among the most impressive acoustic spectacles known from the natural world. They are loud, raucous social environments that form for one purpose and one purpose only: sex. The loud sexual advertisement signals that males produce are often necessary and sufficient to elicit responses from reprod...

Where they co-occur, male anurans of different species may signal from diverse locations and use vocalizations that differ spectrally. However, the relevance of such differences to the problem of signal masking, as well as their ubiquity and efficacy, may have been over-emphasized, especially given data from recent studies. Of greater significance...

Mating duration is a reproductive behaviour that can impact fertilization efficiency and offspring number. Previous studies of factors influencing the evolution of mating duration have focused on the potential role of internal sperm competition as an underlying source of selection; most of these studies have been on invertebrates. For vertebrates w...

In Cope's gray treefrog (Hyla chrysoscelis), thresholds for recognizing conspecific calls are lower in temporally modulated noise backgrounds compared with unmodulated noise. The effect of modulated noise on discrimination among different conspecific calls is unknown. In quiet, females prefer calls with relatively more pulses. This study tested the...

Frogs form large choruses during the mating season in which males produce loud advertisement calls to attract females and repel rival males. High background noise levels in these social aggregations can impair vocal perception. In humans, spatial release from masking contributes to our ability to understand speech in noisy social groups. Here, we t...

The 'multitasking hypothesis' for complex signal function predicts performance trade-offs between signal components that negatively covary (e.g. due to energetic or mechanical constraints) and receiver preferences for more extreme values of the negatively covarying components that are difficult to produce simultaneously. We tested these two predict...

Hearing and acoustic communication in "real world," multi-source environments require animals to group sound elements produced by the same source into perceptually coherent "auditory objects." However, research on nonhuman animal communication rarely investigates perceptual processes involved in forming auditory objects of communication sounds. We...

Frogs are well known model systems in the study of communication for investigating the influences of noise on both signaling behavior and auditory processing. The best-studied frogs in this regard are two sister-species in the Hyla versicolor species complex (H. versicolor and H. chrysoscelis). Males of both species produce loud, pulsatile advertis...

Individual distinctiveness in acoustic signals can allow receivers to respond appropriately to different individuals. The aim of this research was to examine signal variation and to investigate the relative importance of different acoustic properties for coding individual distinctiveness in the advertisement calls of male golden rocket frogs (Anoma...

Frogs and toads have species-specific repertoires of vocalizations that function in contexts related to reproduction. Although some 6000 anuran species have been described to date, we have comparatively few descriptions of their vocalizations, which are among their most conspicuous behaviors. Statistical descriptions of vocal repertoires are key to...

The scientific study of frogs and toads as important systems in behavioural ecology traces its roots to an influential review published in this journal 36 years ago (Wells 1977a, 'The social behaviour of anuran amphibians', Animal Behaviour, 25, 666-693). In just 28 pages, Wells summarized the state of knowledge on important behaviours associated w...

Female frogs discriminate among potential mates based on individual variation in male advertisement calls. While considerable data have accumulated allowing comparisons of female preference functions among species, we still lack fundamental knowledge about how and why the shapes of preference functions for particular call properties vary among popu...

This study tested three hypotheses about the ability of female frogs to exploit temporal fluctuations in the level of background noise to overcome the problem of recognizing male advertisement calls in noisy breeding choruses. Phonotaxis tests with green treefrogs (Hyla cinerea) and Cope's gray treefrogs (Hyla chrysoscelis) were used to measure thr...

Despite the importance of perceptually separating signals from background noise, we still know little about how nonhuman animals solve this problem. Dip listening, an ability to catch meaningful 'acoustic glimpses' of a target signal when fluctuating background noise levels momentarily drop, constitutes one possible solution. Amplitude-modulated no...

This study describes the vocal repertoire of the Guyanan golden rocket frog, Anomaloglossus beebei, a bromeliad specialist with biparental care. Using multivariate analyses of nine call properties, as well as the occurrence of nonlinear phenomena, three signal types were distinguished-advertisement, courtship, and aggressive calls. Although all thr...

An important aspect of hearing and acoustic communication is the ability to discriminate differences in sound level. Little is known about level discrimination in anuran amphibians (frogs and toads), for which vocal communication in noisy social environments is often critical for reproduction. This study used two-choice phonotaxis tests to investig...

Twenty years ago, a new conceptual paradigm known as 'receiver psychology' was introduced to explain the evolution of animal communication systems. This paradigm advanced the idea that psychological processes in the receiver's nervous system influence a signal's detectability, discriminability and memorability, and thereby serve as powerful sources...

Signal detection in fluctuating background noise is a common problem in diverse fields of research and technology. It has been shown in hearing research that the detection of signals in noise that is correlated in amplitude across the frequency spectrum (comodulated) can be improved compared to uncorrelated background noise. We show that the mechan...