Non-hibernating pikas collect winter food reserves and store them in hay piles. Individualization of alarm calls might allow discrimination between colony members and conspecifics trying to steal food items from a colony pile. We investigated vocal posture, vocal tract length, and individual acoustic variation of alarm calls, emitted by wild-living Altai pikas Ochotona alpina toward a researcher. Recording started when a pika started calling and lasted as long as possible. The alarm call series of 442 individual callers from different colonies consisted of discrete short (0.073–0.157 s), high-frequency (7.31–15.46 kHz), and frequency-modulated calls separated by irregular intervals. Analysis of 442 discrete calls, the second of each series, revealed that 44.34% calls lacked nonlinear phenomena, in 7.02% nonlinear phenomena covered less than half of call duration, and in 48.64% nonlinear phenomena covered more than half of call duration. Peak frequencies varied among individuals but always fitted one of three maxima corresponding to the vocal tract resonance frequencies (formants) calculated for an estimated 45-mm oral vocal tract. Discriminant analysis using variables of 8 calls per series of 36 different callers, each from a different colony, correctly assigned over 90% of the calls to individuals. Consequently, Altai pika alarm calls are individualistic and nonlinear phenomena might further increase this acoustic individualization. Additionally, video analysis revealed a call-synchronous, very fast (0.13–0.23 s) folding, depression, and subsequent re-expansion of the pinna confirming an earlier report of this behavior that apparently contributes to protecting the hearing apparatus from damage by the self-generated high-intensity alarm calls. 相似文献
This paper is devoted to the numerical and experimental investigation of hydrogen self-ignition as a result of the formation of a primary shock wave in front of a cold expanding hydrogen gas jet. Temperature increase, as a result of this shock wave, leads to the ignition of the hydrogen–air mixture formed on the contact surface. The required condition for hydrogen self-ignition is to maintain the high temperature in the area for a time long enough for hydrogen and air to mix and inflammation to take place.
Calculations of the self-ignition of a hydrogen jet are based on a physicochemical model involving the gas-dynamic transport of a viscous gas, the kinetics of hydrogen oxidation, the multi-component diffusion, and the heat exchange. We found that the reservoir pressure range, when a shock wave formed in the air during depressurization, has sufficient intensity to produce self-ignition of the hydrogen–air mixture formed at the front of a jet of compressed hydrogen. We present an analysis of the initial conditions (the hydrogen pressure inside the vessel, the temperature of the compressed hydrogen and the surrounding air, and the diameter of the hole through which the jet was emitted), which leads to combustion. 相似文献
The questions of individuality and stability of cues to identity in vocal signals are of considerable importance from theoretical
and conservation perspectives. While individuality in alarm calls has been reported for many sciurids, it is not well-documented
that the vocal identity encoded in the alarm calls is stable between different encounters with predators. Previous studies
of two obligate hibernating rodents, speckled ground squirrels Spermophilus suslicus, and yellow ground squirrels Spermophilus fulvus demonstrated that, after hibernation, most individuals could not be identified reliably by their alarm calls. Moreover, in
most speckled ground squirrels, individual patterns of alarm calls changed progressively over as little as 2 weeks. However,
these previous data have been obtained using the collection of alarm calls from trapped animals. Here, we examined ten free-ranging
dye-marked yellow ground squirrels to determine whether their alarm calls retain the cues to individuality between two encounters
of surrogate predators (humans), separated on average by 3 days. Discriminant function analysis showed that the alarm calls
of individual yellow ground squirrels were very similar within a recording session, providing very high individual distinctiveness.
However, in six of the ten animals, the alarm calls were unstable between recording sessions. Also, we examined ten dye-marked
individuals for consistency of acoustic characteristics of their alarm calls between the encounters of humans, differing in
techniques of call collection, from free-ranging vs trapped animals. We found differences only in two variables, both related
to sound degradation in the environment. Data are discussed in relation to hypotheses explaining the adaptive utility of acoustic
individuality in alarm calls. 相似文献
In addition to encoding referential information and information about the sender’s motivation, mammalian alarm calls may encode
information about other attributes of the sender, providing the potential for recognition among kin, mates, and neighbors.
Here, we examined 96 speckled ground squirrels (Spermophilus suslicus), 100 yellow ground squirrels (Spermophilus fulvus) and 85 yellow-bellied marmots (Marmota flaviventris) to determine whether their alarm calls differed between species in their ability to encode information about the caller’s
sex, age, and identity. Alarm calls were elicited by approaching individually identified animals in live-traps. We assume
this experimental design modeled a naturally occurring predatory event, when receivers should acquire information about attributes
of a caller from a single bout of alarm calls. In each species, variation that allows identification of the caller’s identity
was greater than variation allowing identification of age or sex. We discuss these results in relation to each species’ biology
and sociality. 相似文献
This paper describes a numerical and experimental investigation of hydrogen self-ignition occurring as a result of the formation of a shock wave. The shock wave is formed in front of high-pressure hydrogen gas propagating in a tube. The ignition of the hydrogen–air mixture occurs at the contact surface of the hydrogen and oxidant mixture and is due to the temperature increase produced as a result of the shock wave. The required condition for self-ignition is to maintain the high temperature in the mixture for a time long enough for inflammation to take place. The experimental technique employed was based on a high-pressure chamber pressurized with hydrogen, to the point of a burst disk operating to discharge pressurized hydrogen into a tube of cylindrical or rectangular cross section containing air. A physicochemical model involving gas-dynamic transport of a viscous gas, detailed kinetics of hydrogen oxidation and heat exchange in the laminar approach was used for calculations of high-pressure hydrogen self-ignition. The reservoir pressure range, when a shock wave is formed in the air that has sufficient intensity to produce self-ignition of the hydrogen–air mixture, is found. An analysis of governing physical phenomena based on the experimental and numerical results of the initial conditions (the hydrogen pressure inside the vessel, and the shape of the tube in which the hydrogen was discharged) and physical mechanisms that lead to combustion is presented. 相似文献
In most mammals, larger adult body size correlates with lower fundamental frequency and more closely spaced formants in vocalizations
relative to juveniles. In alarm whistles of two free-living rodents, the speckled ground squirrel Spermophilus suslicus and yellow ground squirrel S. fulvus, these cues to body size were absent despite prominent differences in body weight and skull and larynx sizes between juveniles
and adults. No significant correlations were found between the individual maximum fundamental frequency and body weight, both
within age classes and for pooled samples of all animals within species. Furthermore, the mean alarm whistle maximum fundamental
frequencies did not differ significantly between age classes (juvenile versus adult) in the speckled squirrel and were even
significantly lower in juvenile yellow squirrels. We discuss the hypothesis that the obfuscation of vocal differences between
juvenile and adult squirrels may represent a special adaptation of pup vocal behaviour—a form of “vocal mimicry,” resulting
in imitation of adult vocal pattern to avoid infanticide and age-dependent predation risk. 相似文献
In goitred gazelles (Gazella subgutturosa), sexual dimorphism of larynx size and position is reminiscent of the case in humans, suggesting shared features of vocal
ontogenesis in both species. This study investigates the ontogeny of nasal and oral calls in 23 (10 male and 13 female) individually
identified goitred gazelles from shortly after birth up to adolescence. The fundamental frequency (f0) and formants were measured
as the acoustic correlates of the developing sexual dimorphism. Settings for LPC analysis of formants were based on anatomical
dissections of 5 specimens. Along ontogenesis, compared to females, male f0 was consistently lower both in oral and nasal
calls and male formants were lower in oral calls, whereas the first two formants of nasal calls did not differ between sexes.
In goitred gazelles, significant sex differences in f0 and formants appeared as early as the second week of life, while in
humans they emerge only before puberty. This result suggests different pathways of vocal ontogenesis in the goitred gazelles
and in humans. 相似文献