Beth Pettitt | St. Olaf College (original) (raw)
Papers by Beth Pettitt
Journal of the Acoustical Society of America, Jun 1, 2012
This study describes the vocal repertoire of the Guyanan golden rocket frog, Anomaloglossus beebe... more 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 three call types were composed of a short series of rapidly repeated pulses, advertisement calls were produced at higher amplitudes and had longer pulse durations than both courtship calls and aggressive calls. Courtship calls exhibited lower dominant frequencies than both advertisement and aggressive calls, which had similar dominant frequencies. Aggressive calls had more pulses per call, had longer intervals between calls, and occasionally contained one or two introductory pulses preceding the pulsed call. Several acoustic properties predicted aspects of the signaler's body size and condition. Our study demonstrates the reliability of human observers to differentiate the multiple call types of A. beebei based on hearing calls and observing the social context in which they are produced under field conditions.
Journal of Zoology, 2008
The reproductive output of iteroparous females is influenced by parity and resource availability.... more The reproductive output of iteroparous females is influenced by parity and resource availability. To gain a better understanding of the reproductive decisions made when animals are faced with potential trade‐offs between current and future reproduction; we investigated the relationship of parity and resources availability on reproductive intervals and success by comparing the performance of primiparous and multiparous female Cape ground squirrels Xerus inauris from two study sites that differed in resource availability. Our study included the correlation of reproductive behavioral data with fecal hormonal information to establish a normative endocrine profile for pregnancy and lactation. Parity had a major influence on juvenile emergence with multiparous females having more juveniles emerge successfully. Resource availability did not influence reproductive output, either because of an interaction among multiple resource components including quantity, predictability and length of tim...
Behavioral Ecology, 2019
Male secondary sexual traits potentially function as indicators of direct or indirect fitness ben... more 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 care, we tested predictions from four hypotheses proposed to explain the evolutionary relationship between male secondary sexual traits and paternal care quality (the “good parent,” “differential allocation,” “trade-off,” and “essential male care” hypotheses). We examined: 1) the influence of paternal care on offspring survival, 2) the relationships between male calls and paternal care, maternal care, and opportunities for males to acquire multiple mates, and 3) female preferences for three acoustic properties of male advertisement calls. Our results reveal that paternal care positively impacts offspring survival, that males producing longer ...
Ethology, Mar 1, 2010
An important and necessary step in the analysis of any communication system involves quantitative... more An important and necessary step in the analysis of any communication system involves quantitative descriptions of how signals vary at multiple levels of organization (e.g., species, populations, individuals). Such descriptions provide a basis for generating testable predictions about the functions of signals and their specific physical properties in different behavioral contexts. Here, we report results from acoustical and statistical analyses of the advertisement calls of the boreal chorus frog, Pseudacris maculata. In addition to characterizing measures of central tendency and dispersion for our study population, we assess how calls encode potentially relevant information in the contexts of sexual selection and social recognition. Specifically, we describe the relationships between call properties and both body size and condition, and relate these findings to predictions about female mate choice and male-male competition. We also make predictions about the shapes of female preference functions based on analyses of the patterns of within-individual variation in call properties. Findings from multivariate analyses of advertisement calls are used to generate testable predictions about the potential for these signals to function in social recognition. We also discuss our results in relation to wildlife conservation and relevant studies of geographic variation.
The Journal of the Acoustical Society of America, 2012
This study describes the vocal repertoire of the Guyanan golden rocket frog, Anomaloglossus beebe... more 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 three call types were composed of a short series of rapidly repeated pulses, advertisement calls were produced at higher amplitudes and had longer pulse durations than both courtship calls and aggressive calls. Courtship calls exhibited lower dominant frequencies than both advertisement and aggressive calls, which had similar dominant frequencies. Aggressive calls had more pulses per call, had longer intervals between calls, and occasionally contained one or two introductory pulses preceding the pulsed call. Several acoustic properties predicted aspects of the signaler's body size and condition. Our study demonstrates the reliability of human observers to differentiate the multiple call types of A. beebei based on hearing calls and observing the social context in which they are produced under field conditions.
The Journal of the Acoustical Society of America
This study describes the vocal repertoire of the Guyanan golden rocket frog, Anomaloglossus beebe... more 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 three call types were composed of a short series of rapidly repeated pulses, advertisement calls were produced at higher amplitudes and had longer pulse durations than both courtship calls and aggressive calls. Courtship calls exhibited lower dominant frequencies than both advertisement and aggressive calls, which had similar dominant frequencies. Aggressive calls had more pulses per call, had longer intervals between calls, and occasionally contained one or two introductory pulses preceding the pulsed call. Several acoustic properties predicted aspects of the signaler's body size and condition. Our study demonstrates the reliability of h...
General and Comparative Endocrinology, 2007
Fecal steroid analysis is an increasingly common non-invasive technique used in both captive and ... more Fecal steroid analysis is an increasingly common non-invasive technique used in both captive and field studies to measure an animal's approximate hormonal levels and corresponding physiological state. Fecal collection in the field necessitates storage and transportation methods that will prevent the degradation of hormonal metabolites by fecal bacteria. To determine the most stable and therefore preferred method of storage, 48 fecal samples were collected from six captive female Cape ground squirrels (Xerus inauris). Each sample was randomly divided into three sub-samples to be processed for storage through freezing, drying, or preservation in ethanol. Frozen samples were stored at -20 degrees C, dried-treated samples were desiccated in a conventional oven at 40 degrees C for 4 h, and alcohol-treated samples were preserved in 3 ml of 95% ethanol. Samples were stored for 330 days followed by enzyme immunoassay analysis (EIA) to determine their progestogen and estrone conjugate (E(1)C) concentrations. Validations were performed to establish that the progestogen and E(1)C assays accurately measure fecal progestogen and estrone conjugate concentrations and were sensitive enough to detect biologically meaningful differences in these steroid metabolite concentrations in female X. inauris. Validation results showed a significant difference in progestogen concentrations of gravid females compared to sub-adults and non-gravid females. There was also a significant difference in estrone conjugates between sub-adult and adult females. Duration of storage time did not affect progestogen or estrone metabolite concentrations after being frozen for 3 months. Storage treatment results showed no significant difference between frozen and dried samples, but a significant difference was found between frozen and ethanol samples in both progestogen and estrone conjugate concentrations demonstrating that drying feces provides a reliable method for long-term preservation of fecal steroid concentrations and is the better alternative when freezing is not a viable option.
Ethology, 2013
ABSTRACT Individual distinctiveness in acoustic signals can allow receivers to respond appropriat... more ABSTRACT 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 (Anomaloglossus beebei). We examined patterns of within-individual and among-individual variability in 760 advertisement calls of 40 males as well as repeatability in 16 additional males that were recorded on two different occasions. We examined eight call properties, and all properties exhibited significant among-individual variation and moderate to high repeatability across days. We employed discriminant function analysis to examine individual distinctiveness statistically. These analyses assigned 79% of calls to the correct individual. Fine temporal properties, including pulse duration, pulse rate, and pulse interval, as well as the spectral property of dominant frequency, contributed most toward discrimination among individuals. These results indicate that individual male golden rocket frogs can be distinguished statistically by their advertisement calls. We use these findings to evaluate results of previous playback studies in A. beebei and to generate testable predictions regarding the potential for specific call properties to function in mate selection and social recognition.
Journal of Mammalogy, 2011
We studied the simultaneous effects of social and environmental factors on the age of sexual matu... more We studied the simultaneous effects of social and environmental factors on the age of sexual maturity to identify the major determinants of reproductive delay in the cooperatively breeding female Cape ground squirrel (Xerus inauris). We verified inhibition of sexual maturity by monitoring reproductive behaviors and hormones (using a noninvasive fecal steroid hormone analysis) in prereproductive and reproductive females from 2 populations of squirrels found in southern Africa. We found that 2 social parameters hold the most influence on the timing of female sexual maturity; specifically, the number of adult breeding female group mates and related adult male group mates were associated with a substantial inhibition of female reproductive maturity. Subadult females in social groups with 0 or 1 adult breeding female became sexually mature significantly earlier than similar-aged females in social groups with 2 adult breeding females. Likewise, subadult females in social groups with ,2 related adult male group mates became sexually mature significantly earlier than similar-aged females in social groups with 2 adult related males. Our results show the influence of multiple social parameters on sexual maturity and are consistent with the predictions of the incomplete control model of skew.
Journal of the Acoustical Society of America, Jun 1, 2012
This study describes the vocal repertoire of the Guyanan golden rocket frog, Anomaloglossus beebe... more 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 three call types were composed of a short series of rapidly repeated pulses, advertisement calls were produced at higher amplitudes and had longer pulse durations than both courtship calls and aggressive calls. Courtship calls exhibited lower dominant frequencies than both advertisement and aggressive calls, which had similar dominant frequencies. Aggressive calls had more pulses per call, had longer intervals between calls, and occasionally contained one or two introductory pulses preceding the pulsed call. Several acoustic properties predicted aspects of the signaler's body size and condition. Our study demonstrates the reliability of human observers to differentiate the multiple call types of A. beebei based on hearing calls and observing the social context in which they are produced under field conditions.
Journal of Zoology, 2008
The reproductive output of iteroparous females is influenced by parity and resource availability.... more The reproductive output of iteroparous females is influenced by parity and resource availability. To gain a better understanding of the reproductive decisions made when animals are faced with potential trade‐offs between current and future reproduction; we investigated the relationship of parity and resources availability on reproductive intervals and success by comparing the performance of primiparous and multiparous female Cape ground squirrels Xerus inauris from two study sites that differed in resource availability. Our study included the correlation of reproductive behavioral data with fecal hormonal information to establish a normative endocrine profile for pregnancy and lactation. Parity had a major influence on juvenile emergence with multiparous females having more juveniles emerge successfully. Resource availability did not influence reproductive output, either because of an interaction among multiple resource components including quantity, predictability and length of tim...
Behavioral Ecology, 2019
Male secondary sexual traits potentially function as indicators of direct or indirect fitness ben... more 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 care, we tested predictions from four hypotheses proposed to explain the evolutionary relationship between male secondary sexual traits and paternal care quality (the “good parent,” “differential allocation,” “trade-off,” and “essential male care” hypotheses). We examined: 1) the influence of paternal care on offspring survival, 2) the relationships between male calls and paternal care, maternal care, and opportunities for males to acquire multiple mates, and 3) female preferences for three acoustic properties of male advertisement calls. Our results reveal that paternal care positively impacts offspring survival, that males producing longer ...
Ethology, Mar 1, 2010
An important and necessary step in the analysis of any communication system involves quantitative... more An important and necessary step in the analysis of any communication system involves quantitative descriptions of how signals vary at multiple levels of organization (e.g., species, populations, individuals). Such descriptions provide a basis for generating testable predictions about the functions of signals and their specific physical properties in different behavioral contexts. Here, we report results from acoustical and statistical analyses of the advertisement calls of the boreal chorus frog, Pseudacris maculata. In addition to characterizing measures of central tendency and dispersion for our study population, we assess how calls encode potentially relevant information in the contexts of sexual selection and social recognition. Specifically, we describe the relationships between call properties and both body size and condition, and relate these findings to predictions about female mate choice and male-male competition. We also make predictions about the shapes of female preference functions based on analyses of the patterns of within-individual variation in call properties. Findings from multivariate analyses of advertisement calls are used to generate testable predictions about the potential for these signals to function in social recognition. We also discuss our results in relation to wildlife conservation and relevant studies of geographic variation.
The Journal of the Acoustical Society of America, 2012
This study describes the vocal repertoire of the Guyanan golden rocket frog, Anomaloglossus beebe... more 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 three call types were composed of a short series of rapidly repeated pulses, advertisement calls were produced at higher amplitudes and had longer pulse durations than both courtship calls and aggressive calls. Courtship calls exhibited lower dominant frequencies than both advertisement and aggressive calls, which had similar dominant frequencies. Aggressive calls had more pulses per call, had longer intervals between calls, and occasionally contained one or two introductory pulses preceding the pulsed call. Several acoustic properties predicted aspects of the signaler's body size and condition. Our study demonstrates the reliability of human observers to differentiate the multiple call types of A. beebei based on hearing calls and observing the social context in which they are produced under field conditions.
The Journal of the Acoustical Society of America
This study describes the vocal repertoire of the Guyanan golden rocket frog, Anomaloglossus beebe... more 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 three call types were composed of a short series of rapidly repeated pulses, advertisement calls were produced at higher amplitudes and had longer pulse durations than both courtship calls and aggressive calls. Courtship calls exhibited lower dominant frequencies than both advertisement and aggressive calls, which had similar dominant frequencies. Aggressive calls had more pulses per call, had longer intervals between calls, and occasionally contained one or two introductory pulses preceding the pulsed call. Several acoustic properties predicted aspects of the signaler's body size and condition. Our study demonstrates the reliability of h...
General and Comparative Endocrinology, 2007
Fecal steroid analysis is an increasingly common non-invasive technique used in both captive and ... more Fecal steroid analysis is an increasingly common non-invasive technique used in both captive and field studies to measure an animal's approximate hormonal levels and corresponding physiological state. Fecal collection in the field necessitates storage and transportation methods that will prevent the degradation of hormonal metabolites by fecal bacteria. To determine the most stable and therefore preferred method of storage, 48 fecal samples were collected from six captive female Cape ground squirrels (Xerus inauris). Each sample was randomly divided into three sub-samples to be processed for storage through freezing, drying, or preservation in ethanol. Frozen samples were stored at -20 degrees C, dried-treated samples were desiccated in a conventional oven at 40 degrees C for 4 h, and alcohol-treated samples were preserved in 3 ml of 95% ethanol. Samples were stored for 330 days followed by enzyme immunoassay analysis (EIA) to determine their progestogen and estrone conjugate (E(1)C) concentrations. Validations were performed to establish that the progestogen and E(1)C assays accurately measure fecal progestogen and estrone conjugate concentrations and were sensitive enough to detect biologically meaningful differences in these steroid metabolite concentrations in female X. inauris. Validation results showed a significant difference in progestogen concentrations of gravid females compared to sub-adults and non-gravid females. There was also a significant difference in estrone conjugates between sub-adult and adult females. Duration of storage time did not affect progestogen or estrone metabolite concentrations after being frozen for 3 months. Storage treatment results showed no significant difference between frozen and dried samples, but a significant difference was found between frozen and ethanol samples in both progestogen and estrone conjugate concentrations demonstrating that drying feces provides a reliable method for long-term preservation of fecal steroid concentrations and is the better alternative when freezing is not a viable option.
Ethology, 2013
ABSTRACT Individual distinctiveness in acoustic signals can allow receivers to respond appropriat... more ABSTRACT 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 (Anomaloglossus beebei). We examined patterns of within-individual and among-individual variability in 760 advertisement calls of 40 males as well as repeatability in 16 additional males that were recorded on two different occasions. We examined eight call properties, and all properties exhibited significant among-individual variation and moderate to high repeatability across days. We employed discriminant function analysis to examine individual distinctiveness statistically. These analyses assigned 79% of calls to the correct individual. Fine temporal properties, including pulse duration, pulse rate, and pulse interval, as well as the spectral property of dominant frequency, contributed most toward discrimination among individuals. These results indicate that individual male golden rocket frogs can be distinguished statistically by their advertisement calls. We use these findings to evaluate results of previous playback studies in A. beebei and to generate testable predictions regarding the potential for specific call properties to function in mate selection and social recognition.
Journal of Mammalogy, 2011
We studied the simultaneous effects of social and environmental factors on the age of sexual matu... more We studied the simultaneous effects of social and environmental factors on the age of sexual maturity to identify the major determinants of reproductive delay in the cooperatively breeding female Cape ground squirrel (Xerus inauris). We verified inhibition of sexual maturity by monitoring reproductive behaviors and hormones (using a noninvasive fecal steroid hormone analysis) in prereproductive and reproductive females from 2 populations of squirrels found in southern Africa. We found that 2 social parameters hold the most influence on the timing of female sexual maturity; specifically, the number of adult breeding female group mates and related adult male group mates were associated with a substantial inhibition of female reproductive maturity. Subadult females in social groups with 0 or 1 adult breeding female became sexually mature significantly earlier than similar-aged females in social groups with 2 adult breeding females. Likewise, subadult females in social groups with ,2 related adult male group mates became sexually mature significantly earlier than similar-aged females in social groups with 2 adult related males. Our results show the influence of multiple social parameters on sexual maturity and are consistent with the predictions of the incomplete control model of skew.