Duration Of Ultrasonic Vocalizations Research Articles

2-Chloro-3,7,8-tribromodibenzofuran as a new environmental pollutant inducing atypical ultrasonic vocalization in infant mice.

Epidemiological and experimental studies indicate that maternal exposure to environmental pollutants impairs the cognitive and motor functions of offspring in humans and laboratory animals. Infant ultrasonic vocalizations (USVs), the communicative behavior of pups toward caregivers, are impaired in rodent models of neurodevelopmental disorders, suggesting a useful method to evaluate the developmental neurotoxicity of environmental pollutants. Therefore, we investigated USVs emitted by mouse pups of dams exposed to 2-chloro-3,7,8-tribromodibenzofuran (TeXDF) and 1,2,3,7,8-pentabromodibenzofuran (PeBDF), which are detected in the actual environment. The USV duration and number in the pups born to dams administered with TeXDF 40μg/kg body weight (b.w.), but not 8μg/kg b.w., on gestational day (GD) 12.5, were significantly lower than those in the corresponding pups on postnatal days 3-9. Conversely, there was no statistical change in the USVs emitted by the pups of dams administered with PeBDF 35 or 175μg/kg b.w. on GD 12.5. To examine whether maternal exposure leads to behavioral impairments in adulthood, we analyzed exploratory behaviors in a novel environment using IntelliCage, a fully automated testing apparatus for group-housed mice. Neither TeXDF nor PeBDF exposure induced significant differences in offspring exploration. Considered together, our findings revealed that TeXDF induces atypical USV emission in infant mice, suggesting the importance of further studies on the risk assessment of mixed brominated/chlorinated dibenzo-p-dioxins and dibenzofurans.

The Deepsqueak analysis system is as accurate, yet more efficient, than the Avisoft system across C57BL/6, FVB.129, and FVB mice

Mouse communicative behaviors are referred to as ultrasonic vocalizations (USVs). USVs are relevant to human health and are commonly recorded with the Avisoft-SASLab Pro recording system and the DeepSqueak system however, no study has compared DeepSqueak's accuracy to Avisoft-SASLab Pro's so it is unclear which is the optimal program. We used male and female C57BL/6, FVB.129, and FVB mice and assessed the total USVs detected, USV duration, fundamental frequency, and within system consistency for each system. We found that for all strains assessed, there were extremely high correlations for the quantity of vocalizations that were detected between Avisoft-SASLab Pro and DeepSqueak. Furthermore, no significant differences in USV detection between systems were found for any of the strains. A partial correlation was run to control for the strain, sex, and age covariates and found that no covariate substantially influenced the relationship between the USVs detected in Avisoft-SASLab Pro and those detected in DeepSqueak. We also investigated the duration and fundamental frequency of vocalizations between systems and found medium to large correlations across all strains and several significant differences. We next found that DeepSqueak has higher internal consistency than Avisoft-SASLab Pro when assessing USV duration and fundamental frequency. Lastly, we assessed the average time taken to analyze a file and found DeepSqueak to be the faster system. Altogether, these findings demonstrate that while both DeepSqueak and Avisoft-SASLab Pro are accurate and reliable, DeepSqueak is a more efficient USV analysis program.

Ultrasonic vocalizations in laboratory mice: strain, age, and sex differences.

Mice produce ultrasonic vocalizations (USVs) in different social contexts across lifespan. There is ethological evidence that pup USVs elicit maternal retrieval and adult USVs facilitate social interaction with a conspecific. Analysis of mouse vocal and social repertoire across strains, sex and contexts remains not well explored. To address these issues, in inbred (C57BL/6, FVB) and outbred (CD-1) mouse strains, we recorded and evaluated USVs as neonates and during adult social encounters (male-female and female-female social interaction). We showed significant strain differences in the quantitative (call rate and duration of USVs) and qualitative vocal analysis (spectrographic characterization) from early stage to adulthood, in line with specific patterns of social behaviors. Inbred C57BL/6 mice produced a lower number of calls with less internal changes and shorter duration; inbred FVB mice displayed more social behaviors and produced more syllables with repeated internal changes; outbred CD-1 mice had an intermediate profile. Our results suggest specific vocal signatures in each mouse strain, thus helping to better define socio-communicative profiles of mouse strains and to guide the choice of an appropriate strain according to the experimental settings.

Rapamycin, but not minocycline, significantly alters ultrasonic vocalization behavior in C57BL/6J pups in a flurothyl seizure model

Epilepsy is one of the most common neurological disorders, with individuals having an increased susceptibility of seizures in the first few years of life, making children at risk of developing a multitude of cognitive and behavioral comorbidities throughout development. The present study examined the role of PI3K/Akt/mTOR pathway activity and neuroinflammatory signaling in the development of autistic-like behavior following seizures in the neonatal period. Male and female C57BL/6J mice were administered 3 flurothyl seizures on postnatal (PD) 10, followed by administration of minocycline, the mTOR inhibitor rapamycin, or a combined treatment of both therapeutics. On PD12, isolation-induced ultrasonic vocalizations (USVs) of mice were examined to determine the impact of seizures and treatment on communicative behaviors, a component of the autistic-like phenotype. Seizures on PD10 increased the quantity of USVs in female mice and reduced the amount of complex call types emitted in males compared to controls. Inhibition of mTOR with rapamycin significantly reduced the quantity and duration of USVs in both sexes. Changes in USVs were associated with increases in mTOR and astrocyte levels in male mice, however, three PD10 seizures did not result in enhanced proinflammatory cytokine expression in either sex. Beyond inhibition of mTOR activity by rapamycin, both therapeutics did not demonstrate beneficial effects. These findings emphasize the importance of differences that may exist across preclinical seizure models, as three flurothyl seizures did not induce as drastic of changes in mTOR activity or inflammation as observed in other rodent models.

Exposure to quinestrol and levonorgestrel affects maternal behavior and offspring development in midday gerbil (Meriones meridianus)

Quinestrol and levonorgestrel (EP-1, at a ratio of 1:2) are often used as anti-fertility compounds (sterilants) in rodents. As most of the research has focused on the sterility and damage caused in parental reproductive organs, there is little research on the effect of these contraceptive hormones on maternal behavior and offspring's early development. In this study, we examined maternal behavior after treatment with different doses of EP-1 (10 ml/kg) at postnatal days 3 and 10, separately. Various parameters were measured after treatment, including oxytocin expression, serum levels of estradiol and luteinizing hormone (LH), ovary damage after weaning of offspring, as well as the development and ultrasonic vocalizations (USVs) of midday gerbil (Meriones meridianus) offspring. At postnatal days 5 and 12, the EP-1 increased maternal licking, grooming, and retrieving behavior, while reducing contacting behavior. Oxytocin expression in the hypothalamic paraventricular and supraoptic nuclei increased, while the levels of estradiol and LH decreased. The ovaries and the development of follicles were clearly affected by the treatment. The EP-1 significantly reduced the pups’ body weight, the amount and pulse duration of USVs, whereas the frequency range variation of USVs was increased. Overall, treatment with EP-1 during lactation significantly affected maternal behavior and impaired offspring early development in the midday gerbil.

Rapid development of mature vocal patterns of ultrasonic calls in a fast-growing rodent, the yellow steppe lemming (Eolagurus luteus).

Ultrasonic vocalizations (USV) of laboratory rodents may serve as age-dependent indicators of emotional arousal and anxiety. Fast-growing Arvicolinae rodent species might be advantageous wild-type animal models for behavioural and medical research related to USV ontogeny. For the yellow steppe lemming Eolagurus luteus, only audible calls of adults were previously described. This study provides categorization and spectrographic analyses of 1176 USV calls emitted by 120 individual yellow steppe lemmings at 12 age classes, from birth to breeding adults over 90 days (d) of age, 10 individuals per age class, up to 10 USV calls per individual. The USV calls emerged since 1st day of pup life and occurred at all 12 age classes and in both sexes. The unified 2-min isolation procedure on an unfamiliar territory was equally applicable for inducing USV calls at all age classes. Rapid physical growth (1 g body weight gain per day from birth to 40 d of age) and the early (9–12 d) eyes opening correlated with the early (9–12 d) emergence of mature vocal patterns of USV calls. The mature vocal patterns included a prominent shift in percentages of chevron and upward contours of fundamental frequency (f0) and the changes in the acoustic variables of USV calls. Call duration was the longest at 1–4 d, significantly shorter at 9–12 d and did not between 9-12-d and older age classes. The maximum fundamental frequency (f0max) decreased with increase of age class, from about 50 kHz in neonates to about 40 kHz in adults. These ontogenetic pathways of USV duration and f0max (towards shorter and lower-frequency USV calls) were reminiscent of those in laboratory mice Mus musculus.

Subjecting Dams to Early Life Stress and Perinatal Fluoxetine Treatment Differentially Alters Social Behavior in Young and Adult Rat Offspring.

Recently, the putative association between selective serotonin reuptake inhibitor (SSRI) exposure during pregnancy and the development of social disorders in children has gained increased attention. However, clinical studies struggle with the confounding effects of maternal depression typically co-occurring with antidepressant treatment. Furthermore, preclinical studies using an animal model of maternal depression to study effects of perinatal SSRI exposure on offspring social behavior are limited. Therefore, the aim of this study was to investigate effects of perinatal fluoxetine exposure on juvenile and adult social behavior in male and female rat offspring, using an animal model of maternal vulnerability. We exposed heterozygous serotonin transporter (SERT) deficient female rats to early life maternal separation stress, and used this as a model for maternal vulnerability. Control and early life stressed heterozygous serotonin transporter knockout (SERT) dams were treated with the SSRI fluoxetine or vehicle throughout gestation and lactation. Subsequently, both male and female wildtype (SERT+/+) and heterozygous (SERT+/-) rat offspring were tested for pup ultrasonic vocalizations (USVs), juvenile social play behavior and adult social interaction. Fluoxetine treatment of the dams resulted in a reduced total USV duration in pups at postnatal day 6, especially in SERT+/+ males. Perinatal fluoxetine exposure lowered social play behavior in male offspring from both control and early life stressed dams. However, in females a fluoxetine-induced reduction in juvenile play behavior was only present in offspring from control dams. Offspring genotype did not affect juvenile play behavior. Despite fluoxetine-induced behavioral effects at juvenile age, fluoxetine reduced male adult social behavior in offspring from control dams only. Effects of fluoxetine on female adult social behavior were virtually absent. Interestingly, early life stress in dams increased adult social exploration in vehicle exposed SERT+/+ female offspring and total social behavior in fluoxetine exposed adult SERT+/- male offspring. Furthermore, SERT+/- males appeared less social during adulthood compared to SERT+/+ males. Overall, the present study shows that chronic blockade of the serotonin transporter by fluoxetine during early development has a considerable impact on pup USVs, juvenile social play behavior in both male and female offspring, and to a lesser extent on male social interaction in adulthood.

The Impact of Tauopathy on Ultrasonic Vocalization in a Mouse Model of Frontotemporal Dementia

Tauopathy features in many neurodegenerative diseases, including Alzheimer's disease and frontotemporal dementia and parkinsonism linked to chromosome 17 (FTDP‐17), where aggregation of misfolded and hyperphosphorylated tau impairs cytoplasmic function and axonal transport, and ultimately leads to cell death. Common complications in patients with FTDP‐17 include upper airway dysfunctions such as swallowing and voice disorders and mutism, and in previous work we demonstrated that upper airway and swallowing complications also occur in a mouse model of FTDP‐17 carrying the P301L mutation. Because of these complications, we investigated: 1) Whether Tau‐P301L transgenic mice also have impaired vocalization, owing to vocalization requiring expiratory airflow through the larynx; and 2) The underlying pathology in Tau‐P301L mice linking irregular vocal patterns to tauopathy.Male Tau‐P301L mice on an FVB/N background interacted with a female wildtype (WT) mouse in estrous for 5 minutes, during which ultrasonic vocalizations (USV) were recorded (UltraSoundGate condensor microphone, Avisoft Berlin, Germany). USV recordings were obtained from Tau‐P301L and wild‐type mice aged 3, 5, 7 and 9 months. In parallel, social interactivity was also monitored. While a trend for a lower number and duration of USV and a higher frequency of USV was observed in Tau‐P301L mice, USV in both Tau‐P301L and WT mice were diverse, with the large variance in the number, duration and frequency of vocalizations in Tau‐P301L and WT mice indicating no statistical difference between groups. However, in each age group, the number and duration of USV in a subpopulation of Tau‐P301L mice was lower than and outside the range of WT mice. In these Tau‐P301L mice, 80% of calls were less than 45 msec duration (vs 55% in WT), while 20% of calls were greater than 45 msec duration (vs 45% in WT). The same subpopulation of Tau‐P301L mice displayed a decreased complexity (frequency modulation) and repertoire (call types) of USV compared to WT. These changes to USV in a subpopulation of Tau‐P301L mice were already present in mice aged 3 months, and the parameters measured deteriorated with age. Immunohistochemical analysis identified presence of anti‐human PHF‐Tau (clone AT8, ThermoScientific) and anti‐tau phosphoserine 199/202 (Millipore) immunoreactivity in cell bodies of upper airway and vocalization‐related brain nuclei, including the Periaqueductal Gray (PAG), Nucleus Ambiguus and Kölliker Fuse (KF) nuclei. Further, compared to WT, 40% fewer forkhead box protein P2 (FOXP2) immunoreactive cell bodies were present in the KF of 9‐month‐old Tau‐P301L mice, while the number of FOXP2 immunoreactive cells in the PAG was similar.Our data indicate: 1) an early onset of vocalization disorder in a subpopulation of Tau‐P301L mice; 2) a deterioration in USV that progresses as Tau‐P301L mice age; and 3) presence of tauopathy and neurodegeneration in brain regions that regulate the upper airways and vocalization. Our results also provide a base for examining whether vocalization/voice disturbances are a potential ‘early’ detection diagnostic for dementia.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Adult male mice exposure to nonylphenol alters courtship vocalizations and mating

The neural circuitry processing male sexual behavior is tightly regulated by testosterone and its neural metabolite estradiol. The present study evaluated the effects of adult exposure to low doses of nonylphenol (NP), a widespread environmental contaminant, on the neuroendocrine regulation of testosterone and expression of sexual behavior. Oral exposure of C57BL/6J males to NP (0.5, 5 or 50 μg/kg/day) for 4 weeks did not affect circulating levels of testosterone or the kisspeptin system, a key regulator of the gonadotropic axis. In contrast, mice exposed to NP at 5 μg/kg/day emitted an increased number and duration of ultrasonic vocalizations, took longer to reach ejaculation and showed increased number of mounts, intromissions and thrusts. This was associated with normal olfactory preference and locomotor activity, and increased anxiety level. Analysis of the neural circuitry that underlies sexual behavior showed changes in the number of cells expressing androgen and estrogen receptors in males exposed to NP at 5 μg/kg/day. The neural circuitry underlying sexual behavior is thus highly sensitive to adult exposure to NP. Furthermore, almost all the observed effects were induced at 5 μg/kg/day of NP, indicating that this endocrine disrupter triggers a non-monotonic response in the adult male mouse brain.

Early-Life Social Isolation Influences Mouse Ultrasonic Vocalizations during Male-Male Social Encounters.

Early-life social isolation has profound effects on adult social competence. This is often expressed as increased aggression or inappropriate displays of courtship-related behaviors. The social incompetence exhibited by isolated animals could be in part due to an altered ability to participate in communicatory exchanges. House mice (Mus musculus) present an excellent model for exploring this idea, because social isolation has a well-established influence on their social behavior, and mice engage in communication via multiple sensory modalities. Here, we tested the prediction that social isolation during early life would influence ultrasonic vocalizations (USVs) emitted by adult male mice during same-sex social encounters. Starting at three weeks of age, male mice were housed individually or in social groups of four males for five weeks, after which they were placed in one of three types of paired social encounters. Pair types consisted of: two individually housed males, two socially housed males, or an individually housed and a socially housed male (“mixed” pairs). Vocal behavior (USVs) and non-vocal behaviors were recorded from these 15-minute social interactions. Pairs of mice consisting of at least one individually housed male emitted more and longer USVs, with a greater proportional use of USVs containing frequency jumps and 50-kHz components. Individually housed males in the mixed social pairs exhibited increased levels of mounting behavior towards the socially housed males. Mounting in these pairs was positively correlated with increased number and duration of USVs as well as increased proportional use of spectrally more complex USVs. These findings demonstrate that USVs are part of the suite of social behaviors influenced by early-life social isolation, and suggest that altered vocal communication following isolation reflects reduced social competence.

Strain-and context-based 50 kHz ultrasonic vocalizations and anxiety behaviour in the Wistar-Kyoto rat.

Rodent ultrasonic vocalizations (USVs) are influenced by immediate, prior contexts and have emerged as important indicators that monitor an individual's 'state'. They also index direct reflections of inherent 'trait' and are suggested to constitute non-invasive read-outs of pathological conditions. Analysis of USVs emitted under particular contexts could help discern strain-specific differences and existence of individual USV profiles. USVs of the Wistar-Kyoto (WKY) strain, a putative model of depression, could indicate social communication deficits. In the cage, USV emission was significantly reduced in WKYs. An elevated plus maze exposure led to no change in USV emission in WKYs, while it significantly reduced USVs in Wistars. Re-exposure induced strain-specific differences in behaviour and total calling time. Sonographic patterns indicated that the predominant USV subtype were flat 50 kHz USVs. EPMexposure induced a reduction in peak amplitude in WKY USVs and in USV length in both strains. USV peak frequency and amplitude, genetically determined spectral features, were strain-specific, while bandwidth and temporal features such as total calling time and USV duration were context-dependent. WKY USVs demonstrated characteristic spectral structures such as increased call length and reduced peak frequency while other parameters were not quantitatively different, reflecting the shared phylogeny between Wistars and WKYs.

Effect of lithium-pilocarpine-induced status epilepticus on ultrasonic vocalizations in the infant rat pup

Evidence shows that febrile convulsions induced in rat pups increase ultrasonic vocalizations (USVs); however, the effect of status epilepticus (SE) induced in developing rats on USVs has not been fully investigated. The goal of this study was to analyze USVs following lithium-pilocarpine-induced SE in fourteen-day-old (P14) rat pups. The rat pups were given 3-mEq/kg lithium chloride i.p. on the day before the induction of SE, which was carried out at P14 by subcutaneous injection of 100-mg/kg pilocarpine hydrochloride; control animals were given an equal volume of lithium chloride and saline on P13 and P14, respectively. Ultrasonic vocalizations were monitored at P15, P16, and P21 with a Mini 3 Bat Detector Ultra Sound Advice (15kHz–160kHz) set at 40±4kHz and digitally recorded in WAV format using the Audacity 1.3 beta software. A clear box (60×40×30cm) split down the middle with a holed wall was used; each pup was placed alone in one compartment, whereas its dam was placed on the other cage side at room temperature. Vocalizations were recorded over a 5-minute period, converted to sonograms and spectrograms, and analyzed using the Raven software. Parameters evaluated were as follows: USV frequency, latency to the first USV, and mean USV duration. There was a significant decrease in the latency (35.5±6.9s) and duration (50.8±8.6s) of USVs after SE compared with the control group (81.9±10.8s and 78.1±9.9s, respectively). Status epilepticus affected male and female rats differentially.

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.

Duration of ultrasonic vocalizations in the isolated rat pup as a behavioral measure: Sensitivity to anxiolytic and antidepressant drugs

Neo-natal rats emit ultrasonic vocalizations (USVs) when isolated from their mothers and littermates. Clinically effective anxiolytics reliably reduce USVs, making this behavior a useful animal model of the anxiolytic potential of novel pharmacological approaches to the treatment of anxiety. Here, we assess the hypothesis that USV duration (total time spent vocalizing) is a more sensitive measure of anxiolytic and antidepressant efficacy than USV number by testing established and putative anxiolytics in this model. Negative geotaxis and righting reflex latency were measured to assess sedating properties. The benzodiazepines, CDP (1–10 mg/kg) and diazepam (0.3–3 mg/kg), the 5HT 1A partial agonist, buspirone (0.3–3 mg/kg), and the mGluR5 antagonist, MTEP (1–30 mg/kg), reduced USV duration at lower doses and to a greater magnitude than USV number. The benzodiazepines, unlike buspirone and MTEP, produced measurable sedation, but it was dissociable from reductions in USV duration. The SSRI antidepressants, fluoxetine (1–30 mg/kg) and citalopram (0.3–30 mg/kg), reduced USV duration more than number with no measurable effect on sedation. The tricyclic antidepressants, imipramine (1–10 mg/kg) and amitriptyline (1–30 mg/kg), had no effect dissociable from sedation. These data support USV duration as a more sensitive and useful measure than USV number in the isolated rat pup model.

Fear state induced by ethanol withdrawal may be due to the sensitization of the neural substrates of aversion in the dPAG

The neural substrate underlying the aversive effects induced by ethanol abstinence is still unclear. One candidate for such effects is the dorsal periaqueductal gray (dPAG), a core structure of the brain aversion system. The main aim of this study is to examine the role of the dPAG as a possible locus of the aversive effects following abrupt alcohol withdrawal. To this end, rats were subjected to an oral ethanol self-administration procedure, in which animals were offered 6-8% (v/v) ethanol solution for a period of 21 days followed by an abrupt discontinuation of the treatment on the two subsequent days. Control animals received control dietary fluid for similar periods of time. The effects of ethanol withdrawal were examined in the elevated plus-maze (EPM) (Exp. I), on the prepulse inhibition of startle to loud sounds (Exp. II) and on the freezing and escape responses induced by electrical stimulation of the dPAG (Exp. III). In Experiment III, rats were implanted with an electrode aimed at the dPAG and the number and duration of ultrasonic vocalizations (USVs) were also recorded in the rats that received dPAG stimulation at freezing and escape thresholds. Data obtained showed that ethanol withdrawal elicited significant "anxiety-like" behaviors, as revealed by the decrease in the number of entries into and time spent onto the open arms of the EPM. Startle reflex and prepulse inhibition remained unchanged in withdrawn animals. In addition, discontinuation from the chronic ethanol regimen caused a reduction in the stimulation thresholds for freezing and escape and in the number and duration of USVs. Together, these effects have been interpreted in the frame of a high fear state elicited by activation of the dPAG. These findings are indicative that ethanol withdrawal sensitizes the substrates of fear at the level of this midbrain structure.

The Ontogeny of Ultrasonic Vocalization in Microtus Montanus

AbstractDevelopmental changes in parameters of ultrasound production were investigated in M. montanus young. The rate of ultrasonic vocalization reached a peak on Day 2 of postnatal ontogeny and declined to zero on Day 15. A similar developmental pattern has been found in several other rodent species. However, the comparatively early peak rate is indicative of a degree of ontogenic precociousness. Other developmental changes, both behavioural and morphological, tend to confirm that M. montanus young are relatively precocious. The duration of ultrasonic vocalizations did not show a significant change across early development. The mean duration for each vocalization sampled was 22.92 msec. The distribution of these vocalizations showed that a considerable number of vocalizations were of very short duration (<30 msec). The developmental changes in the percentage of young emitting ultrasounds began to decline following Day 8 and reached zero percent on Day 15. This decline in the percentage of young vocalizing corresponded to changes in maternal behaviour. Both the rate of ultrasonic vocalization and the percentage of young vocalizing were significantly correlated with the age of the young. Being correlated with age, these parameters of ultrasound production have the possibility of having great communicative value for the purposes of maternal care.