Phylogenies of Flying Squirrels (Pteromyinae)

The phylogeny of flying squirrels was assessed, based on analyses of 80 morphological characters. Three published hypotheses were tested with constraint trees and compared with trees based on heuristic searches, all using PAUP*. Analyses were conducted on unordered data, on ordered data (Wagner), and on ordered data using Dollo parsimony. Compared with trees based on heuristic searches, the McKenna (1962) constraint trees were consistently the longest, requiring 8–11 more steps. The Mein (1970) constraint trees were shorter, requiring five to seven steps more than the unconstrained trees, and the Thorington and Darrow (2000) constraint trees were shorter yet, zero to one step longer than the corresponding unconstrained tree. In each of the constraint trees, some of the constrained nodes had poor character support. The heuristic trees provided best character support for three groups, but they did not resolve the basal trichotomy between a Glaucomys group of six genera, a Petaurista group of four genera, and a Trogopterus group of four genera. The inclusion of the small northern Eurasian flying squirrel, Pteromys, in the Petaurista group of giant South Asian flying squirrels is an unexpected hypothesis. Another novel hypothesis is the inclusion of the genus Aeromys, large animals from the Sunda Shelf, with the Trogopterus group of smaller "complex-toothed flying squirrels" from mainland Malaysia and southeast Asia. We explore the implications of this study for future analysis of molecular data and for past and future interpretations of the fossil record.     

Ultrasonic Vocalizations in Rat Sexual Behavior

Ultrasonic vocalizations are very conspicuous during rat matingactivity. Two types of calls are produced by both sexes. Thefirst, brief complex calls with the main frequency centeredabout 50 kHz, occur primarily in conjunction with solicitationand mounting activity. The second type of call is the long,22 kHz whistle which is emitted mainly by the male during thepostejaculatory refractory period, but also by both male andfemale at other times during the copulatory sequence. The occurrenceof ultrasonic vocalizations is correlated with sexual motivationof rats. Males emit more 50 kHz calls before successful matingtests than before tests in which they fail to ejaculate. Furthermore,more vocalizations are emitted by the pair prior to intromissionsthan prior to mounts without intromission. Just before ejaculationthere is a large increase in the rate of calling and, at times,transition by the male to calling at 22 kHz. This latter eventmay represent physiological dearousal by the male. Followingejaculation, the male characteristically emits 22 kHz vocalizationsand exhibits a sleep-like EEG pattern. The function of the postejaculatoryvocalization may be to enforce separation between the matingpair, while at the same lime maintaining contact between thepartners. Fifty kHz calls, on the other hand, prime and facilitatesexual responsiveness of the female. Tape recorded vocalizationsof mating rats facilitate solicitation behavior of estrous femalesin the presence of castrated males, and such females also showa preference for these sounds in a "Y" maze. Deafening of femalesdoes not affect their normal pacing of copulatory contacts,but it drastically reduces their solicitation behavior. Thestudies summarized in this paper lead us to conclude that ultrasonicvocalizations play a major role in the integration of reproductiveactivity in the Norway rat, Rattus norvegicus.     

Human Classification of Context-Related Vocalizations Emitted by Familiar And Unfamiliar Domestic Cats: An Exploratory Study

ABSTRACT

Previous research has shown that human classification of contextspecific domestic cat “meow” vocalizations is relatively poor, although improves with experience and/or general affinity to cats. To investigate whether such classification further improves when recipients (humans) of the vocalizations reside with the vocalizing animal (cat), cat owners (n=10) were asked to listen to eight audio recordings of a single meow (4 from their own cat and 4 from an unfamiliar cat) produced during one of four possible contexts, and identify the context in which each meow was emitted. Contexts comprised food preparation, food-withholding, negotiating a barrier, and attention solicitation. In addition, participants were asked to rate 20 meow vocalizations (produced by unfamiliar cats in the four contexts) on scales measuring pleasantness and urgency, in order to investigate whether participants reached consensus on the emotional content of the vocalizations. Successful identification of both the context and the hypothesized emotional content of the vocalization would comprise the first steps in our understanding of whether human-directed cat “meow” vocalizations are fully advantageous. Forty percent of the participants identified the correct contexts at a level greater than chance when the vocalizations belonged to their own cat. However, no participants performed above chance when vocalizations belonged to an unfamiliar cat. Participants’ urgency ratings were not significantly influenced by the context in which the vocalization was produced. Pleasantness ratings, however, were significantly higher for the context of negotiating a barrier in comparison with attention solicitation. These results suggest that the domestic cat, as a species, does not have a context-specific repertoire of human-directed vocalizations. Successful context classification of cat meows however, was possible for some owners. Whether such success was due to individual learning ability or recognition of hypothesized emotional content of the call requires further investigation.     

Discrimination of Ultrasonic Vocalizations by CBA/CaJ Mice (Mus musculus) Is Related to Spectrotemporal Dissimilarity of Vocalizations

The function of ultrasonic vocalizations (USVs) produced by mice (Mus musculus) is a topic of broad interest to many researchers. These USVs differ widely in spectrotemporal characteristics, suggesting different categories of vocalizations, although this has never been behaviorally demonstrated. Although electrophysiological studies indicate that neurons can discriminate among vocalizations at the level of the auditory midbrain, perceptual acuity for vocalizations has yet to be determined. Here, we trained CBA/CaJ mice using operant conditioning to discriminate between different vocalizations and between a spectrotemporally modified vocalization and its original version. Mice were able to discriminate between vocalization types and between manipulated vocalizations, with performance negatively correlating with spectrotemporal similarity. That is, discrimination performance was higher for dissimilar vocalizations and much lower for similar vocalizations. The behavioral data match previous neurophysiological results in the inferior colliculus (IC), using the same stimuli. These findings suggest that the different vocalizations could carry different meanings for the mice. Furthermore, the finding that behavioral discrimination matched neural discrimination in the IC suggests that the IC plays an important role in the perceptual discrimination of vocalizations.     

Targeted Training of Ultrasonic Vocalizations in Aged and Parkinsonian Rats

Voice deficits are a common complication of both Parkinson disease (PD) and aging; they can significantly diminish quality of life by impacting communication abilities. ^{1, 2} Targeted training (speech/voice therapy) can improve specific voice deficits,^{3, 4} although the underlying mechanisms of behavioral interventions are not well understood. Systematic investigation of voice deficits and therapy should consider many factors that are difficult to control in humans, such as age, home environment, age post-onset of disease, severity of disease, and medications. The method presented here uses an animal model of vocalization that allows for systematic study of how underlying sensorimotor mechanisms change with targeted voice training. The ultrasonic recording and analysis procedures outlined in this protocol are applicable to any investigation of rodent ultrasonic vocalizations.The ultrasonic vocalizations of rodents are emerging as a valuable model to investigate the neural substrates of behavior.^5-8 Both rodent and human vocalizations carry semiotic value and are produced by modifying an egressive airflow with a laryngeal constriction.^{9, 10} Thus, rodent vocalizations may be a useful model to study voice deficits in a sensorimotor context. Further, rat models allow us to study the neurobiological underpinnings of recovery from deficits with targeted training.To model PD we use Long-Evans rats (Charles River Laboratories International, Inc.) and induce parkinsonism by a unilateral infusion of 7 μg of 6-hydroxydopamine (6-OHDA) into the medial forebrain bundle which causes moderate to severe degeneration of presynaptic striatal neurons (for details see Ciucci, 2010).^{11, 12} For our aging model we use the Fischer 344/Brown Norway F1 (National Institute on Aging).Our primary method for eliciting vocalizations is to expose sexually-experienced male rats to sexually receptive female rats. When the male becomes interested in the female, the female is removed and the male continues to vocalize. By rewarding complex vocalizations with food or water, both the number of complex vocalizations and the rate of vocalizations can be increased (Figure 1).An ultrasonic microphone mounted above the male''s home cage records the vocalizations. Recording begins after the female rat is removed to isolate the male calls. Vocalizations can be viewed in real time for training or recorded and analyzed offline. By recording and acoustically analyzing vocalizations before and after vocal training, the effects of disease and restoration of normal function with training can be assessed. This model also allows us to relate the observed behavioral (vocal) improvements to changes in the brain and neuromuscular system.     

Attribution and Expression of Incentive Salience Are Differentially Signaled by Ultrasonic Vocalizations in Rats

During Pavlovian incentive learning, the affective properties of rewards are thought to be transferred to their predicting cues. However, how rewards are represented emotionally in animals is widely unknown. This study sought to determine whether 50-kHz ultrasonic vocalizations (USVs) in rats may signal such a state of incentive motivation to natural, nutritional rewards. To this end, rats learned to anticipate food rewards and, across experiments, the current physiological state (deprived vs. sated), the type of learning mechanism recruited (Pavlovian vs. instrumental), the hedonic properties of UCS (low vs. high palatable food), and the availability of food reward (continued vs. discontinued) were manipulated. Overall, we found that reward-cues elicited 50-kHz calls as they were signaling a putative affective state indicative of incentive motivation in the rat. Attribution and expression of incentive salience, however, seemed not to be an unified process, and could be teased apart in two different ways: 1) under high motivational state (i.e., hunger), the attribution of incentive salience to cues occurred without being expressed at the USVs level, if reward expectations were higher than the outcome; 2) in all experiments when food rewards were devalued by satiation, reward cues were still able to elicit USVs and conditioned anticipatory activity although reward seeking and consumption were drastically weakened. Our results suggest that rats are capable of representing rewards emotionally beyond apparent, immediate physiological demands. These findings may have translational potential in uncovering mechanisms underlying aberrant and persistent motivation as observed in drug addiction, gambling, and eating disorders.     

Behaviour Associated with Ultrasonic Vocalizations in Six Gerbilline Rodent Species

Encounters were staged between male and oestrus-induced females of the same or different taxa of the species/subspecies Gerbillurus paeba paeba, G. p. exilis, G. tytonis, G. setzeri, G. vallinus and Tatera brantsii. Each encounter lasted 20 min; converted ultrasonic emissions were recorded on videotape simultaneously with visual images. Videotapes were transcribed and sequences of acts and vocalizations were recorded. The frequency of acts was compared separately with the number of ultrasonic vocalizations during and after acts by χ² contingency table analysis, followed by partitioned χ² to identify individual acts which contributed significantly to the overall χ² value. Vocalizations occurred significantly more frequently than expected during sexual and/or huddling behaviour in all species-groups; and significantly less frequently than expected during exploratory, watching and/or submissive behaviour. Vocalizations were uncommon during investigative behaviour in all taxa, and aggressive behaviour in Gerbillurus taxa, but occurred significantly more frequently than expected after these behaviour categories in all taxa. Analysis of vocalizations immediately following acts verified the interpretations of function of vocalizations during acts. Ultrasonic vocalizations clearly play an important role in the communication of six taxa of southern African gerbils.     

Ultrasonic Vocalizations of Six Taxa of Southern African Gerbils (Rodentia: Gerbillinae)

Ultrasonic calling during male-female encounters between individuals of the same species was investigated in six taxa of southern African gerbils, namely Tatera brantsii, Gerbillurus paeba paeba, G. p. cxilis, G. tytonis, G. setzeri, and G. vallinus. Vocalizations were detected by means of a bat detector utilizing a superheterodyne signal converter and a countdown circuit. Signals were recorded at audible frequencies and analysed with a sonograph. All taxa vocalized at ultrasonic frequencies by means of strongly modulated frequency “sweep” calls, which differed among taxa in duration, maximum and minimum frequency. “Clicks” were emitted by G. p. paeba and G. p. exilis, and G. tytonis emitted a “stutter” vocalization which consisted of a series of clicks. Long modulated “whistles” were identified from G. vallinus and T. brantsii at lower frequencies than “sweep” calls. Only one call type, a “sweep” call which differed in duration and frequency from all other taxa, was identified in G. setzeri. Cluster analysis was applied to the data using 7 acoustic characters. G. p. paeba and G. p. exilis displayed the highest similarity level between taxa and differed only in frequency of “sweep” vocalizations. G. paeba, G. tytonis and G. setzeri formed one cluster, while G. vallinus and T. brantsii formed a separate cluster. Numbers of calls in interspecific encounters were non-significantly less than in intraspecific encounters in all taxa except G. p. paeba, in which more vocalizations were recorded in inter- than intraspecific encounters. It is not clear whether species discrimination, measured by numbers of vocalizations in interspecific encounters, occurs.     

The Evolution and Paleobiogeography of Flying Squirrels (Sciuridae, Pteromyini) in Response to Global Environmental Change

Flying squirrels are strictly arboreal squirrels adopting a special gliding form of locomotion. This group of animals has a long history that has mirrored the vicissitude of forests. The discrepancy in the distribution between fossils and extant species indicates a mysterious evolution history requiring further exploration. This study compiles the worldwide fossils of Pteromyini to the species level in order to reproduce the spatiotemporal distribution pattern of flying squirrels and deduce the ancestral distribution according to dispersal-vicariance analysis of a phylogeny of the extant species. In addition, we reconstruct the paleoenvironmental background and find that flying squirrels probably originated in the Oligocene–Miocene transition from Europe and immediately dispersed to Asia and North America. Influenced by glaciation, CO₂ reduction, geologic movements and the Paratethys retreat, the Northern Hemisphere underwent climate deterioration and grassland expansion during the late Miocene, and thus the diversity of Pteromyini dramatically decreased. The uplift of the Tibet Plateau in addition to the strengthened Asian monsoons intensified the aridity in central Asia, but brought sufficient water to the densely forested regions of South and Southeast Asia. These forests are likely both refugia and diversification center for flying squirrels during glacial periods in the Quarternary. The subsequent connection and separation events among these heterogeneous habitats has probably been a driving force in the speciation of flying squirrels. Based on this work, we predict a bleak future for the flying squirrels, one which is closely associated with the fate of forests in Asia.     

An Overrepresentation of High Frequencies in the Mouse Inferior Colliculus Supports the Processing of Ultrasonic Vocalizations

Mice are of paramount importance in biomedical research and their vocalizations are a subject of interest for researchers across a wide range of health-related disciplines due to their increasingly important value as a phenotyping tool in models of neural, speech and language disorders. However, the mechanisms underlying the auditory processing of vocalizations in mice are not well understood. The mouse audiogram shows a peak in sensitivity at frequencies between 15-25 kHz, but weaker sensitivity for the higher ultrasonic frequencies at which they typically vocalize. To investigate the auditory processing of vocalizations in mice, we measured evoked potential, single-unit, and multi-unit responses to tones and vocalizations at three different stages along the auditory pathway: the auditory nerve and the cochlear nucleus in the periphery, and the inferior colliculus in the midbrain. Auditory brainstem response measurements suggested stronger responses in the midbrain relative to the periphery for frequencies higher than 32 kHz. This result was confirmed by single- and multi-unit recordings showing that high ultrasonic frequency tones and vocalizations elicited responses from only a small fraction of cells in the periphery, while a much larger fraction of cells responded in the inferior colliculus. These results suggest that the processing of communication calls in mice is supported by a specialization of the auditory system for high frequencies that emerges at central stations of the auditory pathway.     

Ultrasonic Vocalizations of Male Mice Differ among Species and Females Show Assortative Preferences for Male Calls

Male house mice (Mus musculus) emit ultrasonic vocalizations (USVs) during courtship, which attract females, and we aimed to test whether females use these vocalizations for species or subspecies recognition of potential mates. We recorded courtship USVs of males from different Mus species, Mus musculus subspecies, and populations (F1 offspring of wild-caught Mus musculus musculus, Mus musculus domesticus (and F1 hybrid crosses), and Mus spicilegus), and we conducted playback experiments to measure female preferences for male USVs. Male vocalizations contained at least seven distinct syllable types, whose frequency of occurrence varied among species, subspecies, and populations. Detailed analyses of multiple common syllable types indicated that Mus musculus and Mus spicilegus could be discriminated based on spectral and temporal characteristics of their vocalizations, and populations of Mus musculus were also distinctive regardless of the classification model used. Females were able to discriminate USVs from different species, and showed assortative preferences for conspecific males. We found no evidence that females discriminate USVs of males from a different subspecies or separate populations of the same species, even though our spectral analyses identified acoustic features that differ between species, subspecies, and populations of the same species. Our results provide the first comparison of USVs between Mus species or between Mus musculus subspecies, and the first evidence that male USVs potentially facilitate species recognition.     

The Mechanism of Replacement of Red Squirrels by Grey Squirrels: A Test of the Interference Competition Hypothesis

Introduced American grey squirrels have replaced native red squirrels in most of the range currently occupied in Britain and northern Italy. The mechanisms of the replacement are not yet fully understood. We restated the commonly cited Interference Competition Hypothesis (ICH) that grey squirrels interfere with the behaviour of red squirrels in three possible ways: 1. by direct aggressive interactions; 2. by interrupting red squirrel mating-chases; or 3. by forcing red squirrels to actively avoid areas intensively used by grey squirrels. We compared the activity pattern, behaviour and reproductive performance of red squirrels in two study areas in northern Italy, one with only red squirrels (control area C1), the other with both species (experimental area E1). The following predictions were tested: 1. the total time spent in both intraspecific and interspecific interactions by red squirrels increases in the experimental area; 2. most interspecific interactions are aggressive, with grey squirrels being the dominant species; 3. the proportion of breeding female red squirrels that are unsuccessful at weaning offspring increases in area E1; 4. grey squirrels take part and interfere with red squirrel mating-chases, and thereby decrease the reproductive output of red squirrel females; 5. the activity pattern of red squirrels in the mixed-species area is shifted with respect to that in the control area to the hours of the day during which grey squirrels show little activity; and 6. red squirrels will shift their home range (or at least their core-area) when grey squirrel densities increase to avoid interspecific core-area overlap. Our results supported only the first prediction of the ICH: they failed to support all the other predictions. Moreover, the increase in the percentage of active time red squirrels spent interacting with other squirrels in the experimental study area was very small (only 1–2 min/day). Red squirrels did not avoid the woodland patches most intensively used by grey squirrels and the interspecific core-area overlap was similar to red squirrel intraspecific core-area overlap. This suggested that red squirrels avoided spatial overlap with grey squirrels in a similar manner as with conspecifics and that an increase in grey squirrel numbers will augment the intensity of resource competition. We therefore conclude that our results do not lend support to the Interference Competition Hypothesis and that interference competition by grey squirrels cannot explain the large-scale replacement of red by grey squirrels that has occurred in Britain and in Piedmont.     

Biology and Conservation Status of Flying Squirrels (Pteromyini,Sciuridae, Rodentia) in India: An Update and Review

Flying squirrels are capable of gliding and one of the least known mammals of the world. Work on these animals is less and sporadic due to their crepuscular and cryptic habits. At the present scenario, a complete pilot study is in an urgent need to formulate conservation strategies and policies to conserve them in India. Therefore, a thorough review on biology and conservation status of flying squirrels in India is provided here. A total of 13 species of flying squirrels present in India i.e., Belomys pearsonii, Biswamoyopterus biswasi, Eupetaurus cinereus, Eoglaucomys fimbriatus, Hylopetes alboniger, Petaurista elegans, P. mishmiensis, P. magnificus, P. mechukaensis, P. nobilis, P. petaurista, P. philippensis and Petinomys fuscocapillus, wherein three are endemic to the country. P. philippensis has broader distribution and is found to be more studied than others. Eastern part of the country contains the highest species number (n = 10) follows three in northern part, two in southern part and one in western part subsequently. All species are facing threat to their population due to native habitat loss, degradation and hunting. Harmonization, alliances and partnership between various stakeholders along with better application of standard techniques would be strengthen to develop conservation strategies and implementing their coordinated actions could preserve flying squirrels’ future in the country landscape.     

Biosynthesis of Organic Compounds Emitted by Plants

Abstract: Trees produce a wide spectrum of volatile organic compounds (VOCs) including isoprene and monoterpenes, as well as oxygenated compounds like aldehydes, alcohols and carboxylic acids. In recent years, much progress has been made regarding the elucidation of metabolic pathways leading to the production of these compounds. This is particularly true for the biosynthesis of the isoprenoid precursors, isopentenyl diphos-phate (lOP) and dimethyl allyl diphosphate (DMADP). In addition to the classical mevalonate pathway which leads to the biosynthesis of these compounds, recent studies indicate the presence of a non-mevalonate pathway originating from pyru-vate and glyceraldehyde-3-phosphate (GAP), also leading to isoprenoid precursors. This new 1-deoxy-D-xylulose-5-phos-phate (DOXP) pathway is probably responsible for the formation of all plastid-derived isoprenoid compounds in plants, including carotenoids, plastochinones, the prenyl side chains of chlorophyll, as well as monoterpenes and diterpenes. Because all plas-tidic isoprenoids studied so far are formed via this new pathway, it is assumed that isoprene synthesized in the chloroplasts is also produced via this metabolic route. Among the oxygenated hydrocarbons which are emitted by the leaves of trees, C-1 and C-2 aldehydes, alcohols and carboxylic acids are of great importance. C-i compounds are synthesized during many growth and developmental processes such as seed maturation, cell expansion, cell wall degradation, leaf abscission and senescence of plant tissues. The production of C-2 compounds, however, seems mainly to be associated with changing environmental conditions, particularly during stress. Acetaldehyde, for example, is produced in the leaves of trees if the roots are exposed to anaerobic conditions which in nature may be caused by flooding. As a consequence of anaerobiosis, roots produce ethanol through alcoholic fermentation. Ethanol is loaded into the xy-lem, transported to the leaves and oxidized there under aerobic conditions, thereby releasing acetaldehyde and acetic acid.     

Reduction in Ultrasonic Vocalizations in Pups Born to Rapid Eye Movement Sleep Restricted Mothers in Rat Model

The effects of rapid eye movement sleep restriction (REMSR) in rats during late pregnancy were studied on the ultrasonic vocalizations (USVs) made by the pups. USVs are distress calls inaudible to human ears. Rapid eye movement (REM) sleep was restricted in one group of pregnant rats for 22 hours, starting from gestational day 14 to 20, using standard single platform method. The USVs of male pups were recorded after a brief isolation from their mother for two minutes on alternate post-natal days, from day one till weaning. The USVs were recorded using microphones and were analysed qualitatively and quantitatively using SASPro software. Control pups produced maximum vocalization on post-natal days 9 to 11. In comparison, the pups born to REMSR mothers showed not only a reduction in vocalization but also a delay in peak call making days. The experimental group showed variations in the types and characteristics of call types, and alteration in temporal profile. The blunting of distress call making response in these pups indicates that maternal sleep plays a role in regulating the neural development involved in vocalizations and possibly in shaping the emotional behaviour in neonates. It is suggested that the reduced ultrasonic vocalizations can be utilized as a reliable early marker for affective state in rat pups. Such impaired vocalization responses could provide an important lead in understanding mother-child bonding for an optimal cognitive development during post-partum life. This is the first report showing a potential link between maternal REM sleep deprivation and the vocalization in neonates and infants.     

Translational Analysis of Effects of Prenatal Cocaine Exposure on Human Infant Cries and Rat Pup Ultrasonic Vocalizations

Spectral and temporal features of human infant crying may detect neurobehavioral effects of prenatal cocaine exposure (PCE). Finding comparable measures of rodent ultrasonic vocalizations (USVs) would promote translational analyses by controlling the effects of correlated variables that confound human studies. To this end, two studies examined the sensitivity of similar acoustic structures in human infant and rat pup vocalizations to effects of PCE. In Study 1, cry sounds of 107 one month-old infants were spectrum analyzed to create a novel set of measures and to detect the presence of hyperphonation - a qualitative shift to an atypically high fundamental frequency (basic pitch) associated with neurobehavioral insult. Infants with PCE were compared to infants with prenatal polydrug-exposure (PPE) without cocaine and with infants in a standard comparison (SC) group with no prenatal drug exposure. In Study 2, USVs of 118 five day-old rat pups with either PCE, prenatal saline exposure or no prenatal exposures were spectrum analyzed to detect the presence of frequency shifts – acoustic features that have a frequency waveform similar to that of hyperphonation. Results of study 1 showed PCE had two sets of sex-dependent effects on human infants: PCE males had higher pitched cries with more dysphonation (turbulence); PCE females had longer pauses between fewer cry sounds that were of lower amplitude than comparison groups. PCE and PPE infants had more cries with hyperphonation than SC infants. In study 2, PCE pups had a greater percentage of USVs with shift in the acoustic structure than pups in the two control groups. As such, the novel measures of human infant crying and rat pup USVs were sensitive to effects of PCE. These studies provide the first known translational analysis of similar acoustic structures of vocalizations in two species to detect adverse effects of prenatal drug exposure.