Reduced scent marking and ultrasonic vocalizations in the BTBR T+tf/J mouse model of autism

Qualitative impairments in communication, such as delayed language and poor interactive communication skills, are fundamental to the diagnosis of autism. Investigations into social communication in adult BTBR T+tf/J (BTBR) mice are needed to determine whether this inbred strain incorporates phenotypes relevant to the second diagnostic symptom of autism, communication deficits, along with its strong behavioral phenotypes relevant to the first and third diagnostic symptoms, impairments in social interactions and high levels of repetitive behavior. The aim of the present study was to simultaneously measure female urine‐elicited scent marking and ultrasonic vocalizations in adult male BTBR mice, in comparison with a standard control strain with high sociability, C57BL/6J (B6), for the assessment of a potential communication deficit in BTBR. Adult male BTBR mice displayed lower scent marking and minimal ultrasonic vocalization responses to female urine obtained from both B6 and BTBR females. Lower scent marking and ultrasonic vocalizations in a social setting by BTBR, as compared with B6, are consistent with the well‐replicated social deficits in this inbred mouse strain. Our findings support the interpretation that BTBR incorporate communication deficits, and suggest that scent marking and ultrasonic vocalizations offer promising measures of interest in social cues that may be widely applicable to investigations of mouse models of autism.     

Communication impairments in mice lacking Shank1: reduced levels of ultrasonic vocalizations and scent marking behavior

Autism is a neurodevelopmental disorder with a strong genetic component. Core symptoms are abnormal reciprocal social interactions, qualitative impairments in communication, and repetitive and stereotyped patterns of behavior with restricted interests. Candidate genes for autism include the SHANK gene family, as mutations in SHANK2 and SHANK3 have been detected in several autistic individuals. SHANK genes code for a family of scaffolding proteins located in the postsynaptic density of excitatory synapses. To test the hypothesis that a mutation in SHANK1 contributes to the symptoms of autism, we evaluated Shank1(-/-) null mutant mice for behavioral phenotypes with relevance to autism, focusing on social communication. Ultrasonic vocalizations and the deposition of scent marks appear to be two major modes of mouse communication. Our findings revealed evidence for low levels of ultrasonic vocalizations and scent marks in Shank1(-/-) mice as compared to wildtype Shank1(+/+) littermate controls. Shank1(-/-) pups emitted fewer vocalizations than Shank1(+/+) pups when isolated from mother and littermates. In adulthood, genotype affected scent marking behavior in the presence of female urinary pheromones. Adult Shank1(-/-) males deposited fewer scent marks in proximity to female urine than Shank1(+/+) males. Call emission in response to female urinary pheromones also differed between genotypes. Shank1(+/+) mice changed their calling pattern dependent on previous female interactions, while Shank1(-/-) mice were unaffected, indicating a failure of Shank1(-/-) males to learn from a social experience. The reduced levels of ultrasonic vocalizations and scent marking behavior in Shank1(-/-) mice are consistent with a phenotype relevant to social communication deficits in autism.     

The Role of Gonadal Steroid Receptor Activation in the Restoration of Sociosexual Behavior in Adult Male Rats

This work tested the hypothesis that gonadal steroid receptor activation was necessary for the restoration of several sociosexual behaviors (such as copulatory behavior, partner preference, 50-kHz vocalizations, and scent marking) in testosterone-treated gonadectomized male rats. Gonadal steroid receptors were blocked by systemic administration of the antiandrogen hydroxyflutamide, the antiestrogen RU 58668, or both antagonists simultaneously in a restoration paradigm. Inhibiting androgen receptors with hydroxyflutamide blocked the restoration of male copulatory behavior, partner preference (time spent with a sexually receptive female over a nonreceptive female), 50-kHz ultrasonic vocalizations, and scent marking. On the other hand, we did not find that blocking estrogen receptors with RU 58668 inhibited the restoration of copulatory behavior or partner preference in testosterone-treated gonadectomized male rats, even though the level of brain nuclear estrogen receptor occupation was significantly reduced to the level found in gonadectomized males. However, the restoration of scent marking and 50-kHz vocalizations were impaired by RU 58668. Blocking both nuclear androgen and estrogen receptors with the two antagonists simultaneously did not have a greater inhibitory effect than treatment with each antagonist alone. Therefore, the activation of nuclear estrogen receptors is necessary for the restoration of some, but not all, sociosexual behaviors, which are also androgen receptor-dependent. Besides nuclear estrogen receptors, there are additional, but unknown, targets of estradiol that play a role in mediating copulatory behavior in adult male rats. Moreover, the signals from multiple gonadal steroid signaling pathways converge in the regulation of some sociosexual behaviors in adult male rats.     

Sociosexual development,pair bond formation,and mechanisms of fertility suppression in female cotton-top tamarins (Saguinus oedipus oedipus)

The effect of various social environments on sociosexual behavior was examined in six young female cotton-top tamarins (Saguinus oedipus oedipus) and in three established breeding females. Behavioral observations and hormonal samples were collected on young females while they were living with their families, when they were isolated from conspecifics, and after they were paired with an unrelated male. While living with the family, all females showed a suppression of fertility and low frequencies of sociosexual behavior. Following removal from the family, isolated females displayed an increase in rate of scent marking and an increase in hormonal levels. When young females were paired with males, they were exposed to scent secretions from their natal families, from an unfamilar family, and from a control for a total of 24 weeks. After pairing, hormonal levels increased dramatically, and ovarian cyclicity began. An increase in sociosexual behavior and elevated levels of scent marking accompanied this physiological change. Newly paired females had higher rates of affiliative behavior and scent marking than did established breeding females. However, both newly paired and established breeding males were more likely to initiate contact, grooming bouts, and social sniffing than were females. Time to first ovulation was later in females who were exposed to scent secretions from their natal families than it was in those females given a control for the first 8 weeks following pairing. No female conceived during exposure to scent secretions. However, once normal ovarian cycling had begun or a pregnancy was established, exposure to scent secretions had no effect. Thus, the social environment influences the fertility, sociosexual behavior, and pair bond formation of cotton-top tamarins. In addition, chemical stimuli found in the scent secretions produced by the natal family are most likely involved in reproductive suppression.     

The effect of social environment on estrogen excretion,scent marking,and sociosexual behavior in tamarins (Saguinus oedipus)

The influence of various social environments on estrogen excretion, scent marking, and the expression of sociosexual behavior was examined in cotton-top tamarins (Sanguinus o. oedipus). Behavioral observations and urine collections were conducted on five females while first housed in their natal family group or in the presence of another cycling adult female and then while housed with an unrelated adult male in a separate cage. Behavioral observations only were conducted on males in natal family groups and while housed with an unrelated adult female. Levels of urinary estrone and estradiol for females were measured by specific radioimmunoassays. Females housed in family groups or in the presence of an adult cycling female showed low and noncyclic patterns of estrogen excretion. Removal from these environments resulted in a rapid increase in urinary estrone and estradiol and three of five females demonstrated cyclic patterns of estrone excretion. Rates of anogenital marking in females were elevated after the social change, and sexual interactions, virtually absent in the original environments, were observed in all five females. In males, similar manipulations of the social environment affected the expression of sexual behavior, but not scent marking. The social environment, therefore has a profound impact on fertility and sociosexual behavior in cotton-top tamarin groups, with implications for callitrichid social structure and behavior.     

Social behavior in a genetic model of dopamine dysfunction at different neurodevelopmental time points

Impairments in social behavior characterize many neurodevelopmental psychiatric disorders. In fact, the temporal emergence and trajectory of these deficits can define the disorder, specify their treatment and signal their prognosis. The sophistication of mouse models with neurobiological endophenotypes of many aspects of psychiatric diseases has increased in recent years, with the necessity to evaluate social behavior in these models. We adapted an assay for the multimodal characterization of social behavior at different development time points (juvenile, adolescent and adult) in control mice in different social contexts (specifically, different sex pairings). Although social context did not affect social behavior in juvenile mice, it did have an effect on the quantity and type of social interaction as well as ultrasonic vocalizations in both adolescence and adulthood. We compared social development in control mice to a transgenic mouse model of the increase in postsynaptic striatal D2R activity observed in patients with schizophrenia (D2R‐OE mice). Genotypic differences in social interactions emerged in adolescence and appeared to become more pronounced in adulthood. That vocalizations emitted from dyads with a D2R‐OE subject were negatively correlated with active social behavior while vocalizations from control dyads were positively correlated with both active and passive social behavior also suggest social deficits. These data show that striatal dopamine dysfunction plays an important role in the development of social behavior and mouse models such as the one studied here provide an opportunity for screening potential therapeutics at different developmental time points.     

Scent marking in two western Amazonian populations of woolly monkeys (Lagothrix lagotricha)

We describe patterns of scent marking observed in two wild populations of lowland woolly monkeys that were the subjects of long-term studies in the westernmost portion of the Amazon basin. The woolly monkeys engaged primarily in two types of scent marking: chest rubbing and anogenital rubbing. In both study populations, males and females performed both types of scent marking, but males chest-rubbed more commonly than females, while females engaged in more anogenital rubbing. We evaluated two nonexclusive hypotheses for the function of scent marking by woolly monkeys: 1) that scent marking is used in sociosexual contexts, and 2) that scent marking is used to convey information about occupancy of or willingness to defend an area from conspecifics in other social groups. We found no association between the occurrence of scent-marking behavior and location within the home range, but did find that scent marking occurred more commonly than expected on days when copulations, mating solicitations, and intergroup encounters were observed. Additionally, mating activity and chest rubbing were highly correlated across the yearly cycle, even when the potentially confounding variable of ripe fruit availability was controlled for. In woolly monkeys, overt male-male competition is rare and female choice is an important part of the mating system. Our results are most consistent with the idea that scent marking plays a role in advertising male quality or competitive ability, and perhaps in coordinating mating activity.     

Scent Marking, Sexual Behavior and Aggression in Male Gerbils: Comparative Analysis of Endocrine Control

SYNOPSIS. The aggressive, sexual, and scent marking behaviorsof male gerbils (Meriones unguiculatus) are sensitive to gonadalandrogens, but androgens are not equally important in the controlof each behavior. In this species, territorial residency, prioraggressive experience, and unidentified factors that contributeto large individual differences in aggressiveness, influencethe aggressive behavior of males at least as much as androgensdo. To the extent that androgens affect aggression between malegerbils, they act partially by altering aggressiveness and partiallyby altering production of aggression-eliciting cues. The natureof these cues is unknown. Understanding the role of androgensin aggression in this species is further complicated by theobservation that castration can either increase or decreaseaggression depending on the age at which the surgery is performed.In contrast, androgens play aprimary role in the control ofsexual behavior and scent marking. Both behaviors consistentlydecline following castration despite prior experience of themales. Both behaviors are also controlled by the medial preopticarea-anterior hypothalamus, an area of the brain often implicatedin the control of male sociosexual behaviors. It appears, though,that the sites, and possibly the mechanisms, of hormone actionunderlying scent marking and sexual behavior differ. Studyingboth behaviors in the same species, and whenever possible inthe same individuals, is proving to be a useful technique foridentifying such differences between behaviors as their sensitivityto steroids and to brain lesions.     

Long-term effects of pubertal anabolic-androgenic steroid exposure on reproductive and aggressive behaviors in male rats

The current study examined acute and long-term effects of anabolic-androgenic steroid (AAS) exposure during puberty on copulation, vocalizations, scent marking, and intermale aggression, both with and without tail pinch, in intact male rats. Animals received 5 mg/kg of testosterone, nandrolone, stanozolol, or vehicle, beginning at puberty. After 5 weeks, behavior tests were performed while continuing AAS injections. AAS treatment was then discontinued. Behaviors were tested during 3-5 weeks, 9-11 weeks, and 15-17 weeks of withdrawal. During AAS administration, stanozolol males showed significant reductions in all behaviors compared with controls, except aggression with tail pinch. Nandrolone treatment significantly reduced vocalizations and scent marking, and testosterone had no significant effect on behavior. During withdrawal, behaviors in stanozolol males recovered to control levels at variable rates: aggression at 4 weeks; mounts, vocalizations, and scent marking at 9 weeks; and ejaculations at 15 weeks of withdrawal. Stanozolol males showed significantly higher levels of tail pinch-induced aggression during every withdrawal test. Nandrolone-treated males scent-marked at control levels by 9 weeks withdrawal but displayed significantly fewer vocalizations and significantly more tail pinch-induced aggression than controls for the entire study. Testosterone-treated males scent-marked significantly below controls at 3 weeks withdrawal and showed significantly more tail pinch-induced aggression at 5 weeks withdrawal. All three AAS significantly increased tail pinch-induced aggression compared with corresponding nontail pinch tests, even at study endpoint. These results suggest that alterations in androgen-dependent behaviors by pubertal AAS exposure can persist long after drug exposure, and some effects may even be permanent.     

Mice Genetically Depleted of Brain Serotonin Display Social Impairments,Communication Deficits and Repetitive Behaviors: Possible Relevance to Autism

Autism is a complex neurodevelopmental disorder characterized by impaired reciprocal social interaction, communication deficits and repetitive behaviors. A very large number of genes have been linked to autism, many of which encode proteins involved in the development and function of synaptic circuitry. However, the manner in which these mutated genes might participate, either individually or together, to cause autism is not understood. One factor known to exert extremely broad influence on brain development and network formation, and which has been linked to autism, is the neurotransmitter serotonin. Unfortunately, very little is known about how alterations in serotonin neuronal function might contribute to autism. To test the hypothesis that serotonin dysfunction can contribute to the core symptoms of autism, we analyzed mice lacking brain serotonin (via a null mutation in the gene for tryptophan hydroxylase 2 (TPH2)) for behaviors that are relevant to this disorder. Mice lacking brain serotonin (TPH2−/−) showed substantial deficits in numerous validated tests of social interaction and communication. These mice also display highly repetitive and compulsive behaviors. Newborn TPH2−/− mutant mice show delays in the expression of key developmental milestones and their diminished preference for maternal scents over the scent of an unrelated female is a forerunner of more severe socialization deficits that emerge in weanlings and persist into adulthood. Taken together, these results indicate that a hypo-serotonin condition can lead to behavioral traits that are highly characteristic of autism. Our findings should stimulate new studies that focus on determining how brain hyposerotonemia during critical neurodevelopmental periods can alter the maturation of synaptic circuits known to be mis-wired in autism and how prevention of such deficits might prevent this disorder.     

Ultrasonic vocalizations induced by sex and amphetamine in M2, M4, M5 muscarinic and D2 dopamine receptor knockout mice

Adult mice communicate by emitting ultrasonic vocalizations (USVs) during the appetitive phases of sexual behavior. However, little is known about the genes important in controlling call production. Here, we study the induction and regulation of USVs in muscarinic and dopaminergic receptor knockout (KO) mice as well as wild-type controls during sexual behavior. Female mouse urine, but not female rat or human urine, induced USVs in male mice, whereas male urine did not induce USVs in females. Direct contact of males with females is required for eliciting high level of USVs in males. USVs (25 to120 kHz) were emitted only by males, suggesting positive state; however human-audible squeaks were produced only by females, implying negative state during male-female pairing. USVs were divided into flat and frequency-modulated calls. Male USVs often changed from continuous to broken frequency-modulated calls after initiation of mounting. In M2 KO mice, USVs were lost in about 70-80% of the mice, correlating with a loss of sexual interaction. In M5 KO mice, mean USVs were reduced by almost 80% even though sexual interaction was vigorous. In D2 KOs, the duration of USVs was extended by 20%. In M4 KOs, no significant differences were observed. Amphetamine dose-dependently induced USVs in wild-type males (most at 0.5 mg/kg i.p.), but did not elicit USVs in M5 KO or female mice. These studies suggest that M2 and M5 muscarinic receptors are needed for male USV production during male-female interactions, likely via their roles in dopamine activation. These findings are important for the understanding of the neural substrates for positive affect.     

The role of scent marking in the social communication of wild golden lion tamarins, Leontopithecus rosalia

The role of scent marking in the social communication of mammals is widely variable. One reason for this variation is that the function of scent marking may vary with different ecological and social conditions. The purpose of this study was to test four nonexclusive hypotheses explaining the role of scent-marking frequency in different ecological and social contexts for wild golden lion tamarins. Relative to ecological contexts, we compared scent-marking frequency during seasons of abundant and scarce food resources. Relative to social contexts, we compared scent-marking frequency when groups were isolated and when groups were in the presence of neighbouring groups. We found that the tamarins used scent marking to mark the location of food resources. Additionally, males used scent marking to communicate intrasexual dominance within their groups, while females did not. Our results also indicate that alpha females increased their scent-marking frequency to communicate to members of other groups, while the presence of members of other groups did not elicit a similar response by alpha males. We did not find evidence for a territorial function of scent marking in golden lion tamarins. Copyright 2003 Published by Elsevier Science Ltd on behalf of The Association for the Study of Animal Behaviour      

Intracranial androgenic and estrogenic stimulation of male-typical behaviors in house mice (Mus domesticus).

Two experiments in house mice (Mus domesticus) examined the neural sites at which steroid hormones activate the following male-typical behaviors: 70 kHz ultrasonic mating vocalizations in response to stimulus females or their urine, urinary marking in response to stimulus males or stimulus females, mounting of estrous females, and intermale aggression. In the first experiment, four groups of castrated males received bilateral intracranial implants of testosterone (T) into either the septum (SEPTUM), medial preoptic area (MPO), anterior hypothalamus (AHA), or ventromedial hypothalamus (VMH). Two control groups received subcutaneous silastic capsules of T (TSIL) or empty silastic capsules (BSIL). The TSIL males performed all behaviors at male-typical levels while the BSIL males were unresponsive. MPO males emitted ultrasonic mating vocalizations at high levels while few vocalizations were seen in males of the other brain implant groups. The VMH, AHA, and MPO males urine marked at higher levels than the BSIL males but did not exhibit the high levels of the TSIL males. Mounting was observed only in MPO and TSIL males. Aggression was rare in males from any of the brain implant groups. In the second experiment, the hormone activity of the implants was increased by using testosterone propionate (TP) or a 50% mixture of estradiol (E2) and cholesterol. The six groups were SEPTUMTP, SEPTUME2, MPOTP, MPOE2, TPSIL, and BSIL. The TPSIL males performed all behaviors at male-typical levels while the BSIL males were unresponsive. TP was effective at restoring vocalizations and urine marking only when placed in the MPO; however, E2 was effective at both sites. Again aggression and mounting were less evident in the brain implanted males. In conclusion, implants of T or TP were effective in restoring ultrasonic mating vocalization when placed into the MPO. MPO implants of T and TP were also effective in stimulating urine marking, although VMH and AHA implants also showed some effectiveness. The restorative effects of E2 were not localized which is probably related to the greater hormonal activity of this treatment. Comparisons of the properties of the various brain implants to restore more than one behavior were discussed.     

Male‐specific alterations in structure of isolation call sequences of mouse pups with 16p11.2 deletion

16p11.2 deletion is one of the most common gene copy variations that increases the susceptibility to autism and other neurodevelopmental disorders. This syndrome leads to developmental delays, including speech impairment and delays in expressive language and communication skills. To study developmental impairment of vocal communication associated with 16p11.2 deletion syndrome, we used the 16p11.2del mouse model and performed an analysis of pup isolation calls (PICs). The earliest PICs at postnatal day 5 from 16p11.2del pups were found altered in a male‐specific fashion relative to wild‐type (WT) pups. Analysis of sequences of ultrasonic vocalizations (USVs) emitted by pups using mutual information between syllables at different positions in the USV spectrograms showed that dependencies exist between syllables in WT mice of both sexes. The order of syllables was not random; syllables were emitted in an ordered fashion. The structure observed in the WT pups was identified and the pattern of syllable sequences was considered typical for the mouse line. However, typical patterns were totally absent in the 16p11.2del male pups, showing on average random syllable sequences, while the 16p11.2del female pups had dependencies similar to the WT pups. Thus, we found that PICs were reduced in number in male 16p11.2 pups and their vocalizations lack the syllable sequence order emitted by WT males and females and 16p11.2 females. Therefore, our study is the first to reveal sex‐specific perinatal communication impairment in a mouse model of 16p11.2 deletion and applies a novel, more granular method of analysing the structure of USVs.     

Does human infrastructure shape scent marking in a solitary felid?

Human development, such as construction of roads and trails, can affect several animal behaviour traits and is increasing worldwide. Despite the importance of scent marking for communication and social organization in many mammals, it is not clearly understood how scent marking is affected by human habitat modification. We used snow tracking data collected across six winters to study the effects of road infrastructure on the marking behaviour of Eurasian lynx (Lynx lynx) in a human-dominated landscape. We found that lynx marked at higher rates (11.2 urine sprays/km) on human routes (forest roads and logging trails) than when walking in natural habitat (5.8 sprays/km). This pattern was noted in both sexes, although males walked on human routes more frequently and scent marked more often than females. Compared to previous studies the mean marking rates we observed were the highest documented so far for wild felids. This may mainly be due to regular use of human routes (42% of all lynx movement) and the high scent marking rates found thereon. Human routes channelize lynx movement, and scent marking on these routes likely increases the probability of the chemical message being received by a conspecific; therefore human routes might enable more effective communication in territorial felids. Since most of the landscapes worldwide are covered by road networks and various human objects, the marking behaviour of wild mammals may be profoundly changed due to human-caused habitat modifications.     

Sexual dimorphism and gonadal control of ultrasonic vocalizations in adult pine voles, Microtus pinetorum

We investigated the vocalizations produced by adult pine voles during various social interactions by presenting an experimental animal with either an anesthetized or awake (unanesthetized) conspecific. Ultrasonic vocalizations (USVs) occurred frequently during tests in which an awake male was present, but were rarely detected in tests involving only awake females, or when a female was presented with an anesthetized conspecific. Higher rates of USVs were produced when males were tested with a familiar female than when tested with an unfamiliar male or female. Equivalent rates were produced when males were presented with either anesthetized or awake animals, but female-soiled bedding failed to elicit USVs from males. Sonic vocalizations (SVs) were produced by both sexes and were associated with aggressive behavior, but occurred only in tests between awake, unfamiliar animals. Castration greatly reduced and testosterone therapy restored USVs emitted by males in response to anesthetized conspecifics. Our results suggest that (i) USVs are emitted predominantly by males; (ii) familiarity enhances USV response; (iii) SVs are produced during aggressive interactions; and (iv) androgens regulate the production of USVs by males. Possible roles for pine vole vocalizations are discussed.     

Sex differences in ultrasonic vocalizations and coordinated movement in the California mouse (Peromyscus californicus)

Geyer [Am. Zool. 21 (1981) 117] hypothesized that infant rodents increased the number of ultrasonic vocalizations when they moved in and out of the nest in order to elicit extended care from parents. We tested these hypotheses by recording ultrasonic vocalizations (USVs) and coordinated movements (locomotion and grooming) in California mouse and by recording USVs from pups before and after their parents retrieved them. In Experiment 1, USVs and coordinated movements were recorded from 2 to 30 days of age, in female and male Peromyscus californicus pups. USVs at 37, 42, 47, and 52kHz were digitized and recorded by computer and an event recorder program which was simultaneously used to record coordinated movement. Vocalizations persisted to 30 days of age. Vocalizations increased for both males and females after they spent more than 180s in coordinated movement and females vocalized more than males. Females also displayed more coordinated movement and earlier development of coordinated movement than males. There was no effect of litter size on USVs. In Experiment 2, the number of USVs emitted by pups and the latency of dams and sires to contact their pups and retrieve them was measured. There was no significant correlation between the number of USVs emitted by pups and the latency for a parent to contact or retrieve a pup. Results from Experiment 1 provided some support for Geyer's (1981) hypothesis and results from Experiment 2 did not support the hypothesis that the main function of USVs in California mouse pups was to elicit parental care.     

Female presence and estrous state influence mouse ultrasonic courtship vocalizations

The laboratory mouse is an emerging model for context-dependent vocal signaling and reception. Mouse ultrasonic vocalizations are robustly produced in social contexts. In adults, male vocalization during courtship has become a model of interest for signal-receiver interactions. These vocalizations can be grouped into syllable types that are consistently produced by different subspecies and strains of mice. Vocalizations are unique to individuals, vary across development, and depend on social housing conditions. The behavioral significance of different syllable types, including the contexts in which different vocalizations are made and the responses listeners have to different types of vocalizations, is not well understood. We examined the effect of female presence and estrous state on male vocalizations by exploring the use of syllable types and the parameters of syllables during courtship. We also explored correlations between vocalizations and other behaviors. These experimental manipulations produced four main findings: 1) vocalizations varied among males, 2) the production of USVs and an increase in the use of a specific syllable type were temporally related to mounting behavior, 3) the frequency (kHz), bandwidth, and duration of syllables produced by males were influenced by the estrous phase of female partners, and 4) syllable types changed when females were removed. These findings show that mouse ultrasonic courtship vocalizations are sensitive to changes in female phase and presence, further demonstrating the context-sensitivity of these calls.     

Effects of prepubertal ovariectomy on the development of scent glands, scent marking, and aggressive behaviors of female tamarin monkeys (Saguinus fuscicollis)

The effects of prepubertal ovariectomy on scent gland development, scent marking behavior, and on social interactions with strange adult conspecifics were studied in adult females cohabiting with intact males. Eight females were ovariectomized and eight underwent control surgery at 6 months of age. All were returned to their families after surgery and allowed to reach sexual maturity. At 18 months of age, each female was permanently paired with an adult, intact male. When the subjects were 21 months old, the social interactions of all pairs with strange adults were tested in a situation analogous to a territorial encounter. The scent marking activities of the subjects and their mates were studied during “territorial encounters,” in trial-free control situations, and in the presence of novel objects. Ovariectomy prior to puberty retarded the development of the scent gland but did not inhibit it completely. Social interactions with strange conspecifics were also affected. Ovariectomized females showed fewer threat displays than did control females, but there was no significant difference in the amount of injurious aggression both female groups directed at the strangers. Under all testing conditions, ovariectomized females tended to scent mark less frequently with the circumgenital-suprapubic gland than did controls. This difference was statistically significant only under some of the testing conditions. Intact females scent marked more frequently than their males but ovariectomized females did so only under trial-free testing conditions. The sternal scent gland was used very infrequently by all subjects and there was no difference in marking activity between males and females or between ovariectomized and control females.     

Structure of rat ultrasonic vocalizations and its relevance to behavior

Rats are known to emit ultrasonic vocalizations (USVs). These USVs have been hypothesized to hold biological meaning, and the relationship between USVs and behavior has been extensively studied. However, most of these studies looked at specific conditions, such as fear-inducing situations and sexual encounters. In the present experiment, the USVs of pairs of rats in ordinary housing conditions were recorded and their features were examined. Three clusters of USVs in the 25-, 40-, and 60-kHz range were detected, which roughly corresponded to fighting, feeding, and moving, respectively. We analyzed sequential combinations of two or more clusters using a state transition model. The results revealed a more specific correspondence between the USVs and behaviors, suggesting that rat USV may work as a type of communication tool.