Vocalization Rate Research Articles

Distribution and Habitat Use of a Cryptic Small Cetacean, the Burmeister's Porpoise, Monitored From a Small-Scale Fishery Platform

There is widespread evidence that small-scale fisheries (SSF) bycatch threatens many populations of small cetaceans, yet conservation efforts are often limited by a lack of basic knowledge regarding their abundance, distribution and habitat use. Here, we used passive acoustic monitoring from an SSF platform-of-opportunity to better characterize the distribution and habitat use of small cetaceans in northern Peru, focussing on the little known Burmeister’s porpoise Phocoena spinipinnis. From 2009 to 2012, acoustic click detectors (C-PODs) were attached to fishing nets for the duration of 116 fishing sets (30 fishing trips). Dolphins (unspecified delphinids) and porpoises were recorded around 71% and 22% of fishing sets, respectively. The probability of occurrence and buzzing activity (a proxy of foraging), and time spent were linked to both static and dynamic environmental variables to examine the drivers of habitat use. Dolphin activity was spread evenly throughout the fishing area and was not linked to any habitat variables. In contrast, porpoises were detected in neritic waters and habitat models performed well, identifying preferences for shallow (< 200 m depth) and cooler (17-18 °C) waters, close (< 50 km) to shore. The high bycatch rate of small cetaceans in the Peruvian SSF gave us the unique opportunity to investigate the link between bycatch and cetacean acoustic activity. We found a positive relationship between the likelihood of a bycatch event and acoustic presence for both dolphins and porpoises, however as we did not know the timing of entanglement, we could not link vocalization rates to mortality events. Nonetheless, as small cetaceans (particularly dolphins) frequently encounter fishing boats, the likelihood of entanglements may be reduced through effective efforts to alert animals to the presence of the net, either acoustically (through acoustic alarms) or visually. This study demonstrates that passive acoustic monitoring from a fisheries platform can provide insights into the distribution and habitat use of small cetaceans at relatively low cost, and is likely to be suitable in regions with low monitoring effort and high fishing pressure.

Temporal-spatial and source level distributions for a repertoire of fin whale vocalizations in the Norwegian Sea observed with a coherent hydrophone array

The vocalizations of the fin whale are detected, characterized and localized over instantaneous wide areas of the Norwegian and Barents Seas using a large-aperture densely-sampled coherent hydrohone array via the passive ocean acoustic waveguide remote sensing (POAWRS) technique from observations in late winter to early spring 2014. The fin whale vocalizations are comprised of their characteristic 20 Hz pulses, interspersed by 130 Hz upsweeps, less abundant 30-100 Hz downsweep chirps and 18-19 Hz centered backbeats. The time-frequency characteristics of these vocalization types and their diel occurrence rate time-series are quantified in three distinct regions of the Norwegian Sea, off the coasts of Alesund, Lofoten, and the Northern Finnmark. Their vocalization rates are a factor of roughly 5 times and 17 times larger respectively for the 20 Hz and 130 Hz centered vocalizations off Northern Finnmark than the other regions. The vocalization rate spatial density distributions, source level distributions an...

Evaluating autonomous acoustic surveying techniques for rails in tidal marshes

ABSTRACTThere is a growing interest toward the use of autonomous recording units (ARUs) for acoustic surveying of secretive marsh bird populations. However, there is little information on how ARUs compare to human surveyors or how best to use ARU data that can be collected continuously throughout the day. We used ARUs to conduct 2 acoustic surveys for king (Rallus elegans) and clapper rails (R. crepitans) within a tidal marsh complex along the Pamunkey River, Virginia, USA, during May–July 2015. To determine the effectiveness of an ARU in replacing human personnel, we compared results of callback point‐count surveys with concurrent acoustic recordings and calculated estimates of detection probability for both rail species combined. The success of ARUs at detecting rails that human observers recorded decreased with distance (P ≤ 0.001), such that at &lt;25 m, 90.3% of human‐recorded rails also were detected by the ARU, but at &gt;75 m, only 34.0% of human‐detected rails were detected by the ARU. To determine a subsampling scheme for continuous ARU data that allows for effective surveying of presence and call rates of rails, we used ARUs to conduct 15 continuous 48‐hr passive surveys, generating 720 hr of recordings. We established 5 subsampling periods of 5, 10, 15, 30, and 45 min to evaluate ARU‐based presence and vocalization detections of rails compared with each of the full 60‐min sampling of ARU‐based detection of rails. All subsampling periods resulted in different (P ≤ 0.001) detection rates and unstandardized vocalization rates compared with the hourly sampling period. However, standardized vocalization counts from the 30‐min subsampling period were not different from vocalization counts of the full hourly sampling period. When surveying rail species in estuarine environments, species‐, habitat‐, and ARU‐specific limitations to ARU sampling should be considered when making inferences about abundances and distributions from ARU data. © 2018 The Wildlife Society.

Effects of arginine vasopressin on Richardson's ground squirrel social and vocal behavior.

In nearly every vertebrate species examined thus far arginine vasopressin (AVP) and its homologues modulate behavior; thus, providing rich systems for comparative research. In rodents, AVP is best known for its modulation of social behavior; however, to date, research on AVPs effects on behavior have been limited to laboratory models and a few experiments using large outdoor enclosures. To extend our understanding of AVPs role in modulating social behavior and communication in an ecologically relevant context, we examined the effects of AVP on behavior of free-living Richardson's ground squirrels (Urocitellus richardsonii). To test the hypothesis that AVP influences social behavior and communication, we implanted osmotic minipumps into Richardson's ground squirrels and centrally administered AVP or saline as a control. Three different behavioral experiments quantifying behavior before and after AVP or saline administration were performed: a general behavior survey, a predator model presentation, and a social challenge test. AVP administration increased male vocalization rate when approached by a conspecific, but not when presented with a predator model. In males, social aggression decreased, but antipredator vigilance increased with AVP administration. Finally, AVP-treated females had increased "anxiety-like" behaviors during the social challenge test. Our data reveal that AVP has sex-specific effects on vocalizations and antipredator vigilance, as well as other social behaviors. Further, our data illustrate the importance of social context to AVPs modulation of behavior. (PsycINFO Database Record

Individual stability in vocalization rates of preweaning piglets.

Piglet vocalization rates are used as welfare indicators. The emission rates of the two gross categories of piglet calls, namely low frequency calls ("grunts") and high frequency calls ("screams"), may contain different information about the piglet's internal state due to differing communicative functions of the two call types. More knowledge is needed about the sources of variation in calling rates within and between piglets. We examined to what extent the emission rates of the two call types are codetermined by individual and litter identity, i.e., whether the rates are repeatable within individuals and similar between littermates. We recorded frequency of grunts and screams in one mildly negative (short-term Isolation) and one moderately negative (manual Restraint) situation during the first week (week 1) and the 4th week (week 4) of life and asked the following questions: 1) Are within-individual vocalization rates stable across the suckling period? 2) Are within-individual vocalization rates stable across the two situations? 3) Is there within-litter similarity in vocalization rates? 4) Does this within-litter similarity increase during the suckling period? Within-individual vocalization rates were stable between week 1 and week 4 (grunts in Restraint P < 0.05; grunts in Isolation P < 0.001; screams in Restraint P < 0.001; screams in Isolation P < 0.001). Across the two situations at the same age, the vocalization rates were not stable for grunts but were stable for screams at week 1 and week 4 (P < 0.05). Vocalization rates were more similar between littermates than between piglets belonging to different litters (grunts in Restraint P < 0.001; grunts in Isolation P < 0.01; screams in Restraint P < 0.001; screams in Isolation P < 0.001). This litter effect did not grow stronger from week 1 to week 4 as the within-litter coefficient of variance did not decrease between the two ages. Sex of the piglet had no influence on vocalization rates while greater body weight was associated with lower screaming rates in the Restraint situation (P < 0.05). In conclusion, our study demonstrates that both individuality of the piglet and litter identity affect the vocalization rates of piglets in negatively valenced situations. For screams, the repeatability of individual vocalization rates holds even across situations, while for grunts, the rates are repeatable during ontogeny within the situations, but not across situations.

Vocalization as an indicator of estrus climax in Holstein heifers during natural estrus and superovulation

The reliable detection of estrus is an important scientific and practical challenge in dairy cattle farming. Female vocalization may indicate reproductive status, and preliminary evidence suggests that this information can be used to detect estrus in dairy cattle. The aim of this study was to associate the changes in the vocalization rate of dairy heifers with behavioral estrus indicators as well as test the influence of the type of estrus (natural estrus vs. superovulation-induced estrus). We analyzed 6 predefined estrus-related behavior patterns (standing to be mounted, head-side mounting, active mounting, chin resting, being mounted while not standing, and active sniffing in the anogenital region) and vocalization rates in the peri-estrus period (day of estrus ± 1 d) of 12 German Holstein heifers using audio-visual recordings. Each heifer was observed under natural estrus and a consecutive superovulation induced by FSH and cloprostenol. Estrus was determined by behavioral patterns and confirmed by clinical examination (vaginoscopy and ultrasound imaging of the ovaries) as well as by the concentration of peripheral progesterone. Estrus behavior and vocalization rates were analyzed in 3-h intervals (an average of 19 intervals for each heifer), and an estrus score was calculated based on the 6 behaviors. The interval with the highest estrus score (I0) was considered the estrus climax. We demonstrated similar time courses for the estrus score and vocalization rate independent of estrus type. However, in natural estrus, the maximum vocalization rate (±SE) occurred in the interval before estrus climax (I-1; 42.58 ± 21.89) and was significantly higher than that in any other interval except estrus climax (I0; 27.58 ± 9.76). During natural estrus, the vocalization rate was significantly higher within the interval before estrus climax (I-1; 42.58 ± 21.89 vs. 11.58 ± 5.51) than under superovulation. The results underscore the potential use of vocalization rate as a suitable indicator of estrus climax in automated estrus detection devices. Further studies and technical development are required to record and process individual vocalization rates.

The influence of age and sex on the vocal repertoire of the Antillean manatee (Trichechus manatus manatus) and their responses to call playback

AbstractLimited information is available regarding the acoustic communication of Antillean manatees, however, studies have shown that other manatee taxa produce vocalizations as a method of individual recognition and communication. Here, the acoustic signals of 15 Antillean manatees in captivity were recorded, aiming to (1) describe their acoustic repertoire, (2) investigate the influence of sex and age on vocalization, and (3) examine manatee responses to call playback. Six acoustic signals ranging in mean fundamental frequencies from 0.64 kHz to 5.23 kHz were identified: squeaks and screeches were common to adult males, adult females, and juveniles; trills were common to adult males and females; whines were specific to males; creaks were specific to females; and rubbing was specific to juveniles. The structure of squeak vocalizations was significantly different between age and sex classes and screech structure was significantly different between age classes. Squeaks and screeches produced by juveniles had higher frequencies of maximum energy when compared to those produced by adult males and females. A significant increase in the vocalization rate following vocalization playbacks was found for all three age/sex groups. Our results introduce the potential of using acoustic signals in identifying and noninvasively monitoring manatees in the wild in Brazil.

Sex-dependent modulation of ultrasonic vocalizations in house mice (Mus musculus musculus).

House mice (Mus musculus) emit ultrasonic vocalizations (USVs), which are surprisingly complex and have features of bird song, but their functions are not well understood. Previous studies have reported mixed evidence on whether there are sex differences in USV emission, though vocalization rate or other features may depend upon whether potential receivers are of the same or opposite sex. We recorded the USVs of wild-derived adult house mice (F1 of wild-caught Mus musculus musculus), and we compared the vocalizations of males and females in response to a stimulus mouse of the same- or opposite-sex. To detect and quantify vocalizations, we used an algorithm that automatically detects USVs (Automatic Mouse Ultrasound Detector or A-MUD). We found high individual variation in USV emission rates (4 to 2083 elements/10 min trial) and a skewed distribution, with most mice (60%) emitting few (≤50) elements. We found no differences in the rates of calling between the sexes overall, but mice of both sexes emitted vocalizations at a higher rate and higher frequencies during opposite- compared to same-sex interactions. We also observed a trend toward higher amplitudes by males when presented with a male compared to a female stimulus. Our results suggest that mice modulate the rate and frequency of vocalizations depending upon the sex of potential receivers.

AUDITORY EVOKED POTENTIALS AND BEHAVIORAL CONSIDERATIONS WITH HEARING LOSS IN SMALL CETACEANS: APPLICATION AS A STANDARD DIAGNOSTIC TEST IN HEALTH ASSESSMENT.

The primary sense in odontocetes is hearing and a large portion of the odontocete brain is devoted to the auditory processing of echolocation signals. Hearing deficits in odontocetes potentially compromise the ability to forage, navigate, socialize, and evade predators. This presents a challenge to survival and reproduction in wild odontocetes and can affect the general welfare of odontocetes under human care. Currently, little empirical information on how odontocete behavior is affected by hearing loss exists. This study investigated hearing deficits in several species of stranded dolphins and age-related hearing deficits in dolphins kept under human care through auditory evoked potential (AEP) testing and evaluated whether individual behavior correlated with hearing impairment. Behavioral questionnaires for participating animals were completed by individuals with extensive knowledge of the animals' history and behavior. A chi-square analysis determined whether animals with hearing impairment demonstrated behaviors that differed significantly from those considered normal. All tested individuals under human care over 35 years of age had some degree of hearing loss, as did a large percentage of previously stranded animals. Individuals with hearing loss exhibited a range of behavioral changes, including delays in learning new behaviors, accepting novel enrichment, and habituating to new environments. Some individuals with profound hearing loss also displayed a change in vocalization rate in various situations. Findings within previously stranded animals suggest AEP studies should be conducted in all stranded individuals entering rehabilitation. It is further recommended that dolphins living under human care undergo hearing tests as part of their normal health assessments, with emphasis on aging individuals and animals that exhibit delayed learning, respond poorly to audible cues, or show atypical vocalization behavior.

Comparing Contact Calling Between Black Tufted-Ear Marmosets (Callithrix penicillata) in a Noisy Urban Environment and in a Quiet Forest

All habitats have some level of noise but anthropogenic sounds such as those produced by traffic are structurally different from natural sounds, and could cause organisms living in noisy urban areas to modify their vocal communication. We compared temporal and spectral parameters of contact calls in black tufted-ear marmosets (Callithrix penicillata) living in a noisy and a quiet area. From February 2009 to March 2012 we recorded spontaneously produced phee vocalizations by marmosets in two areas in Minas Gerais, Brazil: a noisy urban park (N = 581) in Belo Horizonte, and a quiet natural forest, on Cauaia farm in Matozinhos city (N = 560). We measured the duration, frequencies, and rate of phee vocalizations. We found that marmosets’ phee vocalizations were significantly longer in the noisy area than in the quiet area. The low, high, and dominant frequencies were significantly lower in the noisy area than in the quiet area, and contact calling was less frequent in the noisy area than in the quiet area. We suggest that the differences between marmoset contact calls from noisy and quiet areas are influenced by anthropogenic noise.

Vocalizing during gaps in anthropogenic noise is an uncommon trait for enhancing communication in songbirds

Mounting evidence suggests that anthropogenic noise neg-atively impacts many wildlife species, including songbirds. One mechanism by which noise affects songbirds may be through acoustic obstruction to their systems of vocal communication. However, many species increase the amplitude or pitch of their vocalizations, which may partially mitigate the impact of high noise levels. When the amplitude of anthropogenic noise varies over time, such as near a moderate-use highway, short gaps between noise events may also provide an important oppor- tunity for communication. But, whether songbirds adjust vocalization rates rapidly to avoid overlap with noise is unknown for most species. We used acoustic playback to expose song- birds to simulated road noise during the dawn chorus in oth- erwise quiet habitats. We measured vocalization rates under ambient conditions and during quiet gaps embedded within playback of road noise to assess whether a community of songbirds, and nineteen individual species, vocalize more reg- ularly during noise gaps. There were no significant differences in community-wide acoustic output. Species-specific analysis revealed that only four species altered their vocal rates during quiet gaps in noise, but that the direction of the effect varied by species. Point count results revealed that birds generally remained on site for the duration of the experiment, suggesting that abandonment of noisy locations was unlikely to confound our results. In sum, increasing vocal output during short gaps in noise occurred in only a handful of species, perhaps con- tributing to the limited number of species that are found within noisy habitats.

Vocalizing during gaps in anthropogenic noise is an uncommon trait for enhancing communication in songbirds

Abstract Mounting evidence suggests that anthropogenic noise negatively impacts many wildlife species, including songbirds. One mechanism by which noise affects songbirds may be through acoustic obstruction to their systems of vocal communication. However, many species increase the amplitude or pitch of their vocalizations, which may partially mitigate the impact of high noise levels. When the amplitude of anthropogenic noise varies over time, such as near a moderate-use highway, short gaps between noise events may also provide an important opportunity for communication. But, whether songbirds adjust vocalization rates rapidly to avoid overlap with noise is unknown for most species. We used acoustic playback to expose songbirds to simulated road noise during the dawn chorus in otherwise quiet habitats. We measured vocalization rates under ambient conditions and during quiet gaps embedded within playback of road noise to assess whether a community of songbirds, and nineteen individual species, vocalize more regularly during noise gaps. There were no significant differences in community-wide acoustic output. Species-specific analysis revealed that only four species altered their vocal rates during quiet gaps in noise, but that the direction of the effect varied by species. Point count results revealed that birds generally remained on site for the duration of the experiment, suggesting that abandonment of noisy locations was unlikely to confound our results. In sum, increasing vocal output during short gaps in noise occurred in only a handful of species, perhaps contributing to the limited number of species that are found within noisy habitats.

Investigating the performance of soundscape metrics using known data sources and numerical simulations

Metrics such as the acoustic complexity index, acoustic diversity index, entropy, evenness, and roughness have been correlated with anthropogenic and biologic sound sources in terrestrial soundscapes. The metrics offer the possibility of characterizing the presence of sound sources and the biodiversity of an environment in large datasets without having to perform detailed automated or manual analysis. However, the metrics are less successful at separating soundscape components and measuring biodiversity when applied to marine soundscapes. The reasons provided for the are the spectral overlap between anthropogenic and biologic sources, the wide range of source levels, long propagation ranges, and the difficulty comparing acoustics to observations, especially for species that are soniferous at night and hidden by day. In this analysis, we examine several popular soundscape metrics for marine data containing typical ambient noise, anthropogenic sources, or a single species. We then examine how the metrics change as different magnitudes and repetition rates of simulated marine life vocalizations are added to the data files.

Differences in Vocalisation Patterns of Dugongs Between Fine-Scale Habitats Around Talibong Island, Thailand

Examining characteristics of a species’ fine-scale habitat use contributes to effective and practical spatially explicit conservation. Dugongs (Dugong dugon) are endangered herbivorous mammals that use vocalisation for communication. In a small, specific area of Thai waters, classified here as a “vocal hotspot,” vocalisation rates are elevated, implying that in this area acoustic communication plays an important role. We recorded dugong calls in the vocal hotspot and a nearby feeding area. We then compared temporal patterns of vocalisation between the two sites to investigate the degree of variability in vocalisation between fine-scale habitats, which is important for understanding dugong habitat use by passive acoustic monitoring. From the 489 total hours of recording, 6607 and 2032 calls were observed in the vocal hotspot and feeding area, with mean vocalisation rates (calls per hour) 13.5 and 4.2, respectively. Vocalisation rate had distinctive 24-h periodicity in only the vocal hotspot. Environmental factors that correlated with changes in detected vocalisation rate also differed between the two locations. Water level correlated with vocalisation rate in the feeding area; in contrast, current direction correlated with vocalisation rate in the vocal hotspot. In conclusion, the vocalisation pattern for dugongs differed between the two sites, and we suggest that their habitat use varies at fine spatial scales.

Vocalization Rate and Consonant Production in Toddlers at High and Low Risk for Autism.

Previous work has documented lower vocalization rate and consonant acquisition delays in toddlers with autism spectrum disorder (ASD). We investigated differences in these variables at 12, 18, and 24 months in toddlers at high and low risk for ASD. Vocalization rate and number of different consonants were obtained from speech samples from a prospective study of infant siblings of children with ASD. Three groups were compared: 18 toddlers at low risk for ASD (low-risk control), 18 high-risk siblings without ASD (HRA-), and 10 high-risk siblings with ASD (HRA+). All groups' mean language scores were within the normal range. HRA+ toddlers showed consistently lower vocalization rate; vocalization rate did not predict number of different consonants at 12 months for HRA+. HRA-, not HRA+, toddlers had the smallest number of different consonants and produced significantly fewer different consonants than predicted by their vocalization rate at 12 months. Consonant-acquisition trajectories differed between groups, with HRA- showing the greatest increase from 12 to 18 months. Lower vocalization rate was not associated with reduced number of different consonants in these toddlers. Between-groups differences in developmental trajectories are discussed in the context of the social feedback loop and differential ability to benefit from adult feedback between groups.

Social calls honestly signal female competitive ability in Asian particoloured bats

Why a variety of social animals vocalize during agonistic foraging interactions remains obscure. One possibility is that these signals advertise the signaller's competitive ability, playing a role in the defence of food resources, yet there is limited evidence in support of this idea. Here, we used adult female Asian particoloured bats, Vespertilio sinensis, to test whether individual variation in competitive ability when foraging can be explained by social calls. Using synchronized infrared video and audio recording, we monitored bat social vocalizations, dominance rank and weight gain in triads under controlled food conditions. Additionally, subsequent playbacks, consisting of experimental stimuli, echolocation pulses and silence, were presented to feeding bats in a laboratory. Analyses showed that females uttered low-frequency social calls composed of one to five syllable types during feeding competition. The rates of social vocalizations increased with reduced food availability. Interestingly, dominance score and weight gain correlated weakly with body size, but positively with call rate and associated parameters. Playback of social calls inhibited the visits of bats to the focal food dish compared to playback of silence and echolocation pulses. The amount of food consumed was greatly reduced in the presence of experimental stimuli versus controls. Collectively, these results highlight that acoustic signals serve as an honest indicator of bat competitive ability.

Naturalistic Language Recordings Reveal "Hypervocal" Infants at High Familial Risk for Autism.

Children's early language environments are related to later development. Little is known about this association in siblings of children with autism spectrum disorder (ASD), who often experience language delays or have ASD. Fifty-nine 9-month-old infants at high or low familial risk for ASD contributed full-day in-home language recordings. High-risk infants produced more vocalizations than low-risk peers; conversational turns and adult words did not differ by group. Vocalization differences were driven by a subgroup of "hypervocal" infants. Despite more vocalizations overall, these infants engaged in less social babbling during a standardized clinic assessment, and they experienced fewer conversational turns relative to their rate of vocalizations. Two ways in which these individual and environmental differences may relate to subsequent development are discussed.

Efficient karaoke song recommendation via multiple kernel learning approximation

Online karaoke allows users to practice singing and distribute recordings. Different from traditional music recommendation, online karaoke need to consider users’ vocal competence besides their tastes. In this paper, we develop a karaoke recommender system by taking into account vocal competence. Alone this line, we propose a joint modeling method named MKLA by adopting bregman divergence as the regularizer in the formulation of multiple kernel learning. Specially, we first extract users’ vocal ratings from their singing recordings. Due to an ever-increasing number of recordings, the evaluations in large-scale kernel matrix may cost lots of time and internal storage. Therefore, we propose a sample compression method to eliminate users’ vocal ratings, exploit an MKL method, and learn the latent features of the vocal ratings. These latent features are simultaneously fed into a bregman divergence and then we use the trained classifier to predict the overall rating of a user with respect to a song. Enhanced by this new formulation, we develop the SMO method for optimizing the MKLA dual and present a theoretical analysis to show the lower bound of our method. With the estimated model, we compute the matching degree of users and songs in terms of pitch, volume and rhythm and recommend songs to users. Finally, we conduct extensive experiments with online karaoke data. The results demonstrate the effectiveness of our method.

Diel Variation in Detection and Vocalization Rates of King (Rallus elegans) and Clapper (Rallus crepitans) Rails in Intracoastal Waterways

Abstract. Surveys for secretive marsh birds could be improved with refinements to address regional and species-specific variation in detection probabilities and optimal times of day to survey. Diel variation in relation to naive occupancy, detection rates, and vocalization rates of King (Rallus elegans) and Clapper (R. crepitans) rails were studied in intracoastal waterways in Virginia, USA. Autonomous acoustic devices recorded vocalizations of King and Clapper rails at 75 locations for 48-hr periods within a marsh complex. Naive King and Clapper rail occupancy did not vary hourly at either the marsh or the study area level. Combined King and Clapper rail detections and vocalizations varied across marshes, decreased as the sampling season progressed, and, for detections, was greatest during low rising tides (P < 0.01). Hourly variation in vocalization and detection rates did not show a pattern but occurred between 7.8% of pairwise comparisons for detections and 10.5% of pairwise comparisons for vocalizati...

Behavioral Ecology of American Pikas (Ochotona princeps) at Mono Craters, California: Living on the Edge

The behavioral ecology of the American pika (Ochotona princeps) was investigated at a relatively hot south-facing, low-elevation site in the Mono Craters, California, a habitat quite different from the upper montane regions more typically inhabited by this species and where most prior investigations have been conducted. Mono Craters pikas exhibited a behavioral profile that contrasted significantly with that of pikas found in upper montane regions. Mono Craters pikas were less surface active than pikas in studies at high-elevation sites, although their rate of short-call vocalizations was similar. Mono Craters pikas did not exhibit typical foraging behavior: they fed and collected hay at significantly reduced rates, and did not construct large central-place hay piles. Social behaviors (conspecific aggression, social tolerance, avoidance) were infrequent compared with data from prior studies in upper montane environments. The Mono Craters site appears to be one of the warmest localities in which pikas have been observed. Recorded talus surface temperatures consistently exceeded 30 °C, and temperatures >40 °C were commonly recorded. In contrast, temperatures measured in the matrix of the talus were consistently cooler, and the apparent insulating effect of talus, as measured by the difference between surface and matrix temperatures, was typically most pronounced on the hottest days. Although pika activity was most frequent in early morning, late afternoon, and at night, pikas were also active during the hottest part of the day, presumably because of their ability to behaviorally thermoregulate by retreating into the cooler talus matrix. Data on populations of pikas which inhabit marginal sites can help us understand how pikas and other montane animals might respond in a world of climate change so that we may more effectively plan for their conservation.