Article

Vocalisations of the Degu Octodon degus, a social caviomorph rodent

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Abstract

Caviomorph species are well known for their social nature and variety of vocal sounds used in intra-species communication, making them ideal candidates for the study of vocalisations. Here, I provide a much needed categorisation for one such species, the Degu Octodon degus. By analysing 3535 vocal sounds, I demonstrate that there are 15 distinct categories for degu vocalisations, showing that degus have a wider and more complex vocal repertoire than was previously assumed. I find that the use of vocal sounds varies widely with season and behavioural context, consistent with interaction in a complex social hierarchy. I identify that certain categories are not used by pups and that others may be gender-specific. In addition, I find that vocalisations used by lactating females may have an alternative function to that previously assumed. By examining the frequency range of the vocalisations identified, I predict that the hearing range of the degu lies between 71 Hz to 21.7 kHz. Finally, I describe the structure, causation and likely function of each vocal type.

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... The vocal repertoire of spotted paca herein described, provides some reflection regarding the presence of homologies among caviomorph rodents. The cry call, for example, is structurally similar and seems to occur in the same behavioral context (contact/isolation) as the degu's (Octodon degus) loud whistle [67] and the guinea pig's (Cavia porcellus) isolation whistle [68]. The emission of tooth chattering, a mechanical signal described for spotted paca, was also present in several caviomorph species, including Hydrochoerus hydrochaeris [44], Cavia sp. ...
... [68], Kerodon rupestris [69], Ctenomys talarum [70], and showing similarities in behavioral contexts and acoustic structures [37]. The groan vocalization in the spotted paca is functionally like groans in degu [67] and whine in rock cavy (Kerodon rupestris) [69] and guinea pigs [68], all emitted in aggressive contexts. Growls emitted by spotted paca are agonistic calls and are possibly used as defensive function of the grunt call in tuco-tuco (Ctenomys talarum) [70], rock cavy [69], and degu [67], which provide similar acoustic patterns. ...
... The groan vocalization in the spotted paca is functionally like groans in degu [67] and whine in rock cavy (Kerodon rupestris) [69] and guinea pigs [68], all emitted in aggressive contexts. Growls emitted by spotted paca are agonistic calls and are possibly used as defensive function of the grunt call in tuco-tuco (Ctenomys talarum) [70], rock cavy [69], and degu [67], which provide similar acoustic patterns. Bark calls of spotted paca also show similarities with the capybara's bark [44] in both function (alarm call) and acoustic features. ...
Article
Full-text available
The evolution of sociality is related to many ecological factors that act on animals as selective forces, thus driving the formation of groups. Group size will depend on the payoffs of group living. The Social Complexity Hypothesis for Communication (SCHC) predicts that increases in group size will be related to increases in the complexity of the communication among individuals. This hypothesis, which was confirmed in some mammal societies, may be useful to trace sociality in the spotted paca (Cuniculus paca), a Neotropical caviomorph rodent reported as solitary. There are, however, sightings of groups in the wild, and farmers easily form groups of spotted paca in captivity. Thus, we aimed to describe the acoustic repertoire of captive spotted paca to test the SCHC and to obtain insights about the sociability of this species. Moreover, we aimed to verify the relationship between group size and acoustic repertoire size of caviomorph rodents, to better understand the evolution of sociality in this taxon. We predicted that spotted paca should display a complex acoustic repertoire, given their social behavior in captivity and group sightings in the wild. We also predicted that in caviomorph species the group size would increase with acoustic repertoire, supporting the SCHC. We performed a Linear Discriminant Analysis (LDA) based on acoustic parameters of the vocalizations recorded. In addition, we applied an independent contrasts approach to investigate sociality in spotted paca following the social complexity hypothesis, independent of phylogeny. Our analysis showed that the spotted paca’s acoustic repertoire contains seven vocal types and one mechanical signal. The broad acoustic repertoire of the spotted paca might have evolved given the species’ ability to live in groups. The relationship between group size and the size of the acoustic repertoires of caviomorph species was confirmed, providing additional support for the SCHC in yet another group of diverse mammals–caviomorph rodents.
... This allows investigation of same-sex peer motivations without the confound of selective long-term bonds, meanwhile also minimizing aggressive behaviors that are typical between unfamiliar, same-sex adults of many rodent species. In native habitats, female degus are recognized for their constructive interactions, such as communal nursing, with both related and unrelated, same-sex individuals [26,[30][31][32][33]. Degus also express a wide range of vocalizations in the human hearing range, and these have been manually classified based on spectral features and the social contexts in which they are used [34]. Degus therefore express a high dimensionality of social behavior that can be quantified to compare interactions between different experimental conditions. ...
... To unpack this result, vocalization syllables were manually and automatically parsed into types. Manual classification included 32 categories, guided by previous research on degu social vocalizations [34]. Of these, only approximately 14 vocalization types were observed at least once, on average, per session-for the purposes of analysis, all others were included within a 15 th "mixed" category. ...
... This syllable type was often manually scored as a "chaff" (Fig 1I) and was distinguished by relatively high average dominant frequencies around 6000 Hz, slightly lower-than-average entropy or frequency dispersion (i.e., more "scratchy") and slightly higher than average amplitude. These vocalizations were not more temporally associated with specific interactive behaviors than average vocalizations, although prior work has suggested that chaffs may be more agonistic in nature [34]. ...
Article
Many animals become more motivated to interact after a period of isolation. This phenomenon may involve general drives, e.g. for social touch or companionship, as well as drives that are specific to particular peers, and which ultimately serve to reestablish relationships between the individuals. Female degus are known to be affiliative with multiple other individuals, including unrelated and unfamiliar conspecifics, offering an opportunity to study social motivation independent from exclusive pair-bonds or overt, same-sex competition. We attempted to disentangle factors driving peer interaction by examining reunion behavior across several social isolation and separation manipulations. High levels of interaction were observed between adult females who had been separated even without isolation, revealing a drive to re-establish relationships with specific peers. The content of separation-only reunions differed from isolation, with the latter involving more early-session interaction, higher levels of allogrooming before rear-sniffing, and a higher ratio of chitter vocalizations. To assess whether post-isolation behavior was related to stress, we examined reunions following a non-social (footshock) stressor. Like isolation, footshock increased early-session interactions, but did not increase allogrooming before rear-sniffing or chittering, as compared with controls. To test whether separation-only reunion behavior shared qualities with relationship formation, we also examined reunions of new (stranger) dyads. Strangers exhibited higher levels of interaction than cagemates, with particularly high levels of late-session rear-sniffing. Like separation-only reunions, strangers showed more non-chitter vocalizations and lower levels of allogrooming before rear-sniffing. Across experiments, an exploratory clustering method was used to identify vocalizations that differed between conditions. This yielded promising leads for future investigation, including a chaff-type syllable that may have been more common during relationship renewal. Overall, results are consistent with the hypothesis that female degu reunions are supported by both general and peer-stimulus specific drives, expressed through the structure of physical and vocal interactions over time.
... Degus also exhibit a rich vocal repertoire that regulates the level physical proximity with a conspecific from the first day of life. For example, isolated pups emit ''whistle'' vocalizations that may induce retrieval by an adult (Fuchs, Iacobucci, MacKinnon, & Panksepp, 2010;Long, 2007). Degu pups also interact with siblings from the first days of life. ...
... Peer-play episodes appear during the second week of life (Wilson & Kleiman, 1974) and peak in the following week (Fuchs, Iacobucci, MacKinnon, & Panksepp, 2007). During playful interactions, they emit typical ''warble'' vocalizations (Long, 2007). In adulthood, the richness of the vocal repertoire is extended. ...
... In this instance, during agonistic encounters, degus emit ''groan'' and ''grunt'' vocalizations that repel the conspecific. On the other hand, isolated adults emit ''chaff'' and ''chitter'' vocalizations that elicit the approach of a distant partner and encourage social engagement (Long, 2007). Therefore, social interactions in degus are strongly evident from early infancy through the life course, making this species valuable for the study of early social bonds. ...
Article
We investigated whether positive daily peer-interactions counteract the effects of isolation in Octodon degus. Twenty-five-day-old degus were either isolated (ISO), socially housed (SOCIAL), or isolated and allowed 1-hr daily peer interaction (PARTIAL-ISO). The animals were observed over 4 weeks. Just prior to isolation and after 2 weeks of individual housing, the subjects were assessed for response to pleasant stimuli via a sucrose preference test and to fearful situations in open field and startle tests. Two weeks after the previous tests, the subjects were retested as above and observed in novelty and sociability tests. Only the ISO group showed significant alterations in sensitivity to reward and increased risk-taking behavior in fearful situations. The ISO group consumed more sucrose, spent less time freezing in the startle test and exhibited increased exploration in open field and novelty tests compared to PARTIAL-ISO and SOCIAL groups. In the sociability test, the SOCIAL group vocalized more than the other two groups during encounters with an unfamiliar degus. Our findings suggest that (i) chronic isolation induces alteration of hedonic, emotional and social profiles, with a maturational delay in fear-related responses; (ii) friendly interaction attenuates most behavioral changes induced by total social isolation. However, the positive effects of daily social interactions did not fully counteract deficits in social vocalizations. Our study represents one of the few available studies focused not only on the consequences of negative life events in this species, but also the protective role of relatively short periods of positive social activity on subsequent emotional development. © 2010 Wiley Periodicals, Inc. Dev Psychobiol 53:280-290, 2011.
... Degus also exhibit a rich vocal repertoire that regulates the level physical proximity with a conspecific from the first day of life. For example, isolated pups emit ''whistle'' vocalizations that may induce retrieval by an adult (Fuchs, Iacobucci, MacKinnon, & Panksepp, 2010;Long, 2007). Degu pups also interact with siblings from the first days of life. ...
... Peer-play episodes appear during the second week of life (Wilson & Kleiman, 1974) and peak in the following week (Fuchs, Iacobucci, MacKinnon, & Panksepp, 2007). During playful interactions, they emit typical ''warble'' vocalizations (Long, 2007). In adulthood, the richness of the vocal repertoire is extended. ...
... In this instance, during agonistic encounters, degus emit ''groan'' and ''grunt'' vocalizations that repel the conspecific. On the other hand, isolated adults emit ''chaff'' and ''chitter'' vocalizations that elicit the approach of a distant partner and encourage social engagement (Long, 2007). Therefore, social interactions in degus are strongly evident from early infancy through the life course, making this species valuable for the study of early social bonds. ...
Article
Full-text available
We investigated whether positive daily peer-interactions counteract the effects of isolation in Octodon degus. Twenty-five-day-old degus were either isolated (ISO), socially housed (SOCIAL), or isolated and allowed 1-hr daily peer interaction (PARTIAL-ISO). The animals were observed over 4 weeks. Just prior to isolation and after 2 weeks of individual housing, the subjects were assessed for response to pleasant stimuli via a sucrose preference test and to fearful situations in open field and startle tests. Two weeks after the previous tests, the subjects were retested as above and observed in novelty and sociability tests. Only the ISO group showed significant alterations in sensitivity to reward and increased risk-taking behavior in fearful situations. The ISO group consumed more sucrose, spent less time freezing in the startle test and exhibited increased exploration in open field and novelty tests compared to PARTIAL-ISO and SOCIAL groups. In the sociability test, the SOCIAL group vocalized more than the other two groups during encounters with an unfamiliar degus. Our findings suggest that (i) chronic isolation induces alteration of hedonic, emotional and social profiles, with a maturational delay in fear-related responses; (ii) friendly interaction attenuates most behavioral changes induced by total social isolation. However, the positive effects of daily social interactions did not fully counteract deficits in social vocalizations. Our study represents one of the few available studies focused not only on the consequences of negative life events in this species, but also the protective role of relatively short periods of positive social activity on subsequent emotional development. ß 2010 Wiley Periodicals, Inc. Dev Psychobiol 53: 280-290, 2011.
... Relatedness of colony members is also variable, ranging from 0.07 to 0.48 between females in one wild population, and averaging 0.25 which is equivalent to second-order kinship (Ebensperger et al., 2004). During the daytime, the group members roam above ground and coordinate their foraging activity by keeping visual contact (Ebensperger and Bozinovic, 2000;Ebensperger et al., 2002;Quirici et al., 2008;Vasquez, 1997) and emitting audible vocalizations (Long, 2007). They synchronize their digging activity to build complex underground burrows, which they share when night falls, and use routinely as refuges to raise their precocious but unweaned pups (Ebensperger et al., 2004;Fulk, 1976;Lee, 2004). ...
... By contrast, degus use a variety of vocalizations to adjust their level of social proximity during all developmental stages. For instance, isolated degu pups emit "whistle" DVs which, in early development, induce retrieval by adults (Fuchs et al., 2010;Long, 2007). Once reunited with their mother, degu infants emit specific reunion calls, which are characterized by 4-kHz chirping components (Iacobucci, personal observation). ...
... Degu pups exhibit clear bouts of rough-and-tumble play, which is also well developed in most domestic rats, but not domestic mice. When degu pups playfully interact with their siblings, they emit a variety of vocalizations, including "warble" calls (Long, 2007) that resemble their reunion calls, and when interactions between siblings become too vigorous, perhaps verging into aggression, the father squeaks "at" the pups and appears to actively separate them (Wilson, 1982). During foraging, degus emit specific alarm calls (Long, 2007), and the social interactions of adults and adolescents are accompanied by a diversity of warbling, whistling and grunting noises (characterized by Long, 2007). ...
Chapter
Full-text available
The scientific interest in caviomorph rodents as possible animal models for social and affective neuroscience is increasing in a remarkable way. The present contribution reviews the literature on the social behavior of caviomorph species, with an emphasis on domestic guinea pigs and Octodon degus. After providing an overview of the developmental milestones, we present current laboratory-based studies on the strength of social bonds, sensitivity to social environment, and the developmental and epigenetic factors involved in the expression of social behavior. Finally, we discuss possible lines of research to broaden our knowledge of the social behavior of these promising animal models. Keywords: degus; epigenetic; guinea pigs; social behaviour; social bonding
... Relatedness of colony members is also variable, ranging from 0.07 to 0.48 between females in one wild population, and averaging 0.25 which is equivalent to second-order kinship (Ebensperger et al., 2004). During the daytime, the group members roam above ground and coordinate their foraging activity by keeping visual contact (Ebensperger and Bozinovic, 2000;Ebensperger et al., 2002;Quirici et al., 2008;Vasquez, 1997) and emitting audible vocalizations (Long, 2007). They synchronize their digging activity to build complex underground burrows, which they share when night falls, and use routinely as refuges to raise their precocious but unweaned pups (Ebensperger et al., 2004;Fulk, 1976;Lee, 2004). ...
... By contrast, degus use a variety of vocalizations to adjust their level of social proximity during all developmental stages. For instance, isolated degu pups emit "whistle" DVs which, in early development, induce retrieval by adults (Fuchs et al., 2010;Long, 2007). Once reunited with their mother, degu infants emit specific reunion calls, which are characterized by 4-kHz chirping components (Iacobucci, personal observation). ...
... Degu pups exhibit clear bouts of rough-and-tumble play, which is also well developed in most domestic rats, but not domestic mice. When degu pups playfully interact with their siblings, they emit a variety of vocalizations, including "warble" calls (Long, 2007) that resemble their reunion calls, and when interactions between siblings become too vigorous, perhaps verging into aggression, the father squeaks "at" the pups and appears to actively separate them (Wilson, 1982). During foraging, degus emit specific alarm calls (Long, 2007), and the social interactions of adults and adolescents are accompanied by a diversity of warbling, whistling and grunting noises (characterized by Long, 2007). ...
Article
A challenge for social-affective neuroscience programs is to identify simple and yet valid animal models for studying the expression of basic social emotions and their role during different developmental windows, from infancy to adulthood. For example, although laboratory rats are useful for studying juvenile social interactions, they are not ideal for studying infant attachment bonds. Here, we evaluate current understanding of the social behavior of Octodon degus, a diurnal precocial rodent, to elucidate the value of this species as a model for social-affective neuroscience research. After a synopsis of species-specific characteristics and brain susceptibility to changes of social environment, our behavioral findings on degu social proclivities are summarized. We then discuss why this pre-clinical model provides a valuable addition to the commonly available animal models for the study of human psychopathology.
... Degus are often used in attachment studies because they display several relevant social traits. For example, they live in extended family groups consisting of one or two males and one to four females and their young [3,4], they cooperate to increase vigilance to predators [5][6][7] and communicate with each other using more than 15 types of sounds [8,9]. These social traits could indicate that degus are sensitive to social environments, and that they might show human-like behavioral changes in response to social isolation. ...
... The mean number decreased in the second half of trials for all weeks except at 2 weeks for the nonisolated group and at 6 weeks for the isolated group. A three-way ANOVA revealed a significant main effect of "trial epoch" (F (1,8) = 46.79, p < 0.001). ...
... We found a significant firstorder interaction between "age" and "trial epoch" (F(4,32) = 5.28, p < 0.005) and a second-order The number of entries lessened from the first half to the second half of trials for both groups, except for the nonisolated group at 2 weeks and isolated group at 6 weeks. A three-way ANOVA revealed a significant main effect of "trial epoch" (F (1,8) = 34.71, p < 0.001). ...
Article
Full-text available
Our previous research using Octodon degus (degus) revealed that preweaning social isolation negatively affected object exploratory behavior. However, it remains unknown how social isolation affects animal psychology and other behaviors. The present study examined the effects of neonatal social isolation on degu emotion and mother–infant interactions before and after weaning. Because degus have a complex social repertoire, we predicted that they would be sensitive to social isolation and show similarities with humans in their social interaction. Pups in the isolation group were separated from their family seven times for 30 min a day from 8 to 15 days post-birth. Pups in the nonisolation group were reared with their family. At 2, 3, 4, 5, and 6 weeks of age, pups underwent a zero-maze test to measure anxiety and a mother–infant interaction test to assess mother–infant attachment. Isolated pups showed more activity in the zero-maze test than nonisolated pups at 3 weeks of age. We found no significant effects of social isolation on mother–infant interactions. These results suggest that while neonatal social isolation might affect emotion during weaning, it does not influence mother–infant relationships.
... We used captive degus, Octodon degus (Rodentia, Octodontidae). The degu is a social rodent and has a vocal repertoire of at least 15 items (Long 2007), but their vocal learning (contextual/production learning) has not been investigated (Janik and Slater 2000). Our captive degus had never experienced genuine predators, enabling us to explore both the innate production of alarm calls and the intrinsic responses to the alarm call of degus in the laboratory, although alarm call production and response are often different between captive and free-living animals (Mateo and Holmes 1999;Ouattara et al. 2009). ...
... Alarm calls emitted by the degu were recorded using a solid state recorder (Marantz Professional PMD660; D&M Holdings, Kanagawa, Japan; sampling rate of 48 kHz, 16-bit, monaural channel, wav format), which was connected to a 21-mm condenser microphone (AT3031; Audio-Technica, Tokyo, Japan; ±5 dB at 30 Hz to 20 kHz) set at a distance of 10 or 30 cm from the center of the cage floor. By comparing with the alarm calls from captive degus (Long 2007), we identified the alarm calls emitted from the degus in alarming events: the degus produced a distress call in similar situations, but we could distinguish alarm calls from distress calls on the basis of syllable durations (alarm call, \100 ms; distress call, [200 ms). Recorded syllables were transferred to a PC on a USB flash memory device and analyzed with Avisoft-SASLab Pro v.4.52 (Avisoft Bioacoustics, Berlin, Germany) at an FFT (Fast Fourier Transformation) size of 512 (Hanning window) after highpass filtering at 2,000 Hz to eliminate low frequency background noise. ...
... Recorded syllables were transferred to a PC on a USB flash memory device and analyzed with Avisoft-SASLab Pro v.4.52 (Avisoft Bioacoustics, Berlin, Germany) at an FFT (Fast Fourier Transformation) size of 512 (Hanning window) after highpass filtering at 2,000 Hz to eliminate low frequency background noise. This filtering did not affect the acoustic analysis because the typical lowest frequency of the degu alarm call is higher than 4,000 Hz (Long 2007). Syllable duration, peak frequency, bandwidth of frequency range within 10 dB below the peak frequency (Q 10 dB ), and entropy were compared between syllable types. ...
Article
Full-text available
Many social animals develop vocal communications to send and receive information efficiently in a group. In alarm communication, call recipients in a social group evaluate alarm calls, enhancing their probability of survival in the face of predatory threats. Calls from naïve and younger group members might be less evocative, in terms of rendering group members vigilant, than calls from more experienced adults because adults are generally more reliable. It remains uncertain, however, what acoustic characteristics render an alarm call reliable. Here, we report that adult degus, Octodon degus (Rodentia, Octodontidae), produced an alarm with a frequency-modulated (FM) syllable, accompanied by low bandwidth and entropy, to evoke a high-vigilance response amongst receivers. Unlike adults, subadult degus did not emit the FM syllable in the warning context, and their call without the FM syllable evoked less vigilance than the adult alarm. We suggest that the FM structure of the adult-produced syllable serves as the primary feature characterizing a reliable alarm call. Our results are consistent with those found in other social rodents, e.g., ground squirrels and gerbils, also produce FM alarm calls in high-urgency situations supports the importance of the FM syllable in alarm communication.
... Anxious and frightening situations are avoided and energy is spent in pleasureable and relaxed activities such as foraging, socialising, playing, sleeping, eating and grooming (Panksepp 1998 Wolff and Sherman 2007) with more into the role of sound, particularly ultrasound (e.g. Sales and Pye 1974;Long 2007Long , 2009Panksepp 2007) and visual signals. For example, recent work into pain and analgesia has revealed clear visual signals and the development of reliable species-specific Facial Grimace Scales (Langford et al. 2010;Keating et al. 2012;Oliver et al. 2014;Miller and Leach 2015); useful resources for both owners and professionals. ...
... These reflect adaptations to the soundscapes of differing natural habitats, be that grasslands, woods, rocky areas or open desert spaces. SPM hearing ranges overlap ours but extend into the ultrasonic, with mice hearing up to 85 KHz, guinea-pig 50KHz and rabbit 42KHz (Sales and Pye 1974;Berryman 1976;Heffner and Heffner 2007;Long 2007Long , 2009). ...
Article
People have obligations to ensure the welfare of animals under their care. Offences under the UK Animal Welfare Act (HMSO 2006) are acts, or failures of action, causing unnecessary suffering. Veterinary professionals need to be able to provide current, scientifically-based prophylactic advice, and respect the limits of their expertise. The ethical concept of a life worth living and the Five Freedoms are core to welfare (FAWC 2009; Broom and Fraser 2015). Behaviour is a central component, both influencing and influenced by physical health. Keepers of small prey mammals (SPM) frequently misunderstand their behaviour and how to meet their needs. This review provides insight into the physical-social (external) and the cognitive-emotional (internal) environments of SPM, contextualised within an evolutionary perspective. This is extrapolated to captivity and practical suggestions given for meeting behavioural freedoms and enhancing client understanding and enjoyment of their animals, thereby improving welfare for both.<br/
... The tweet call was classified mainly as an offspring vocalization emitted during mother cleaning maintenance, and likely related to increase proximity and maintain parental care-taking behavior. Degu offspring use two types of isolation calls (Long 2007): the loud whistle and the low whistle, both non-modulated sounds classified as a distress signal (loud whistle) and an affiliative signal (low whistle). The loud whistle is probably a "true" isolation call because it triggers recovery and care behavior from adults, while the low whistle could be more a location signal when pups are away from the nest. ...
Chapter
-Fully integrative approach to the socibiology of caviomorph rodents. Brings together research on social systems with that on epigenetic, neurendocrine and developmental mechanisms of social behavior. Describes the social systems of many previously understudied caviomorph species, identifying the fitness costs and benefits of social living in current day populations as well as quantified evolutionary patterns or trends. Highlights potential parallels and differences with other animal models.
... The tweet call was classified mainly as an offspring vocalization emitted during mother cleaning maintenance, and likely related to increase proximity and maintain parental care-taking behavior. Degu offspring use two types of isolation calls (Long 2007): the loud whistle and the low whistle, both non-modulated sounds classified as a distress signal (loud whistle) and an affiliative signal (low whistle). The loud whistle is probably a "true" isolation call because it triggers recovery and care behavior from adults, while the low whistle could be more a location signal when pups are away from the nest. ...
... According to Marx et al. (2003), emission parameters related to energy, frequency and duration are particularly effective for characterising call types. For example, low-tone vocalisations, such as grunts by sheep, are used to maintain social contact with members of the group, while many high-pitched screams are similar to those used in an excited state (Ferreira et al. 2000;Charrier et al. 2001;Long 2007;Martinez et al. 2011). ...
Article
The aim of this review is to discuss sensory recognition (olfaction, vision, vocalisation, hearing and direct contact) in relation to the ewe-lamb bond, and the relevance of this information for animal management, considering that sensory recognition between ewes and their offspring is a key element of lamb welfare. In some parental care strategies, parents promote recognition of their own young in order to ensure their survival by providing them - and only them - with food, while the young simultaneously learn features of the environment. In the specific case of sheep, mother-young bonding is established during the sensitive period of the first 4 h after birth. The ewe prints a distinctive signal on her lambs that marks her as the legitimate mother, while stimulating the offspring's learning processes through olfactory, visual and acoustic cues. However, the sensory basis for proximal recognition of lambs changes over time as they learn to recognise the signals emitted by the mother. After 4 h - or less - the ewe becomes maternally selective; this means that she accepts only her own lambs at the udder, while actively rejecting alien newborns. Likewise, newborn lambs develop a preference for their mothers in less than one day. This preference is regulated by the difference between the acceptance behaviour manifested by the lamb's own mother and the aggressive rejecting behaviour shown by alien ewes. This early discriminative ability allows the lamb to avoid the aggressive actions of alien dams and maintain close contact with its own lactating mother. At around one week of age, lambs learn to develop the sensory cues that allow them to recognize their mother. These include olfactory, visual, acoustic and tactile information. Mutual ewe-lamb recognition at an early age also ensures that newborns will be fed and cared for by their own mother, which satisfies some of the requirements for their survival and welfare. For all these reasons, any disruption of ewe-lamb bonding during parturition is detrimental to lamb welfare and survival.
... The tweet call was classified mainly as an offspring vocalization emitted during mother cleaning maintenance, and likely related to increase proximity and maintain parental care-taking behavior. Degu offspring use two types of isolation calls (Long 2007): the loud whistle and the low whistle, both non-modulated sounds classified as a distress signal (loud whistle) and an affiliative signal (low whistle). The loud whistle is probably a "true" isolation call because it triggers recovery and care behavior from adults, while the low whistle could be more a location signal when pups are away from the nest. ...
Chapter
In this chapter we examine the mechanisms of communication in caviomorph rodents. Our aim was to review the available information, putting it into the context of social systems (social versus solitary species), while taking a look at different areas of social behavior for which signals in different modalities have been described and analyzed. We found that there is not much data available on the majority of the communication modalities in caviomorphs. Most of our understanding comes from research on acoustic signals. Several families with social species (Chinchillidae, Echimyidae, Caviidae, Octodontidae) exhibit alarm call “systems,” conveying information on predator proximity or danger level, and that could reflect high social complexity. This result is consistent with the theoretical statement that higher social complexity is correlated with higher communicative complexity. Another finding was that Caviomorphs appear to use many multimodal signals. In particular, octodontids and other related groups produce UV-reflectant urine, implying that use of multimodal signals is associated with the use of underground tunnels and/or refuges. Research aimed at understanding multi-modal signals as well as the repertories of most Caviomorphs, in all their modalities, is needed to enhance our understanding of the role of communication in the social life of these animals.
... In most rodents, acoustic communication between parents and offspring or between adults is primarily based on the ultrasonic calls over 20 kHz (Vieira and Brown, 2002;Riede, 2011Riede, , 2013Riede, , 2018Brudzynski, 2014;Pasch et al., 2017;Klenova et al., 2021b) or on the audible-through-ultrasonic calls, starting below and ending above 20 kHz or vice versa (Pasch et al., 2011;Kobayasi and Riquimaroux, 2012;Campbell et al., 2014;Riede and Pasch, 2020). At the same time, pups of precocious caviomorph rodents seem to vocalize only in the audible range of frequencies (Tokumaru et al., 2004;Long, 2007;Monticelli and Ades, 2013), although Long (2009) interprets the upper harmonics of the audible call as ultrasound. Some rodents, as yellow steppe lemmings Eolagurus luteus, equally use at isolation and handling both ultrasonic and audible call types from the first day onwards throughout ontogeny (Rutovskaya, 2019;Yurlova et al., 2020;Klenova et al., 2021a;Volodin et al., 2021b). ...
Article
Acoustic individuality is present in diverse taxa of mammals and birds, becoming especially prominent in those age groups for which discriminating conspecifics by voice is critically important. This study compares, for the first time, the ontogenetic changes of acoustic individuality of ultrasonic and audible calls (USVs and AUDs) across 12 age-classes (from neonates to adults) in captive yellow steppe lemmings Eolagurus luteus. We found that, in this rodent species, the isolation-induced USVs and AUDs are not individually distinct at any age. We discuss that this result is unusual, because discriminating individuals by individualistic vocal traits may be important for such a social species as yellow steppe lemming. We also discuss the potential role of acoustic individuality in studies including rodent models.
... Another interesting degu social trait is the production of phonemes of different frequency. By combining phonemes, degus can make more than 15 different sounds and can use these to communicate (Long, 2007;Tokimoto, Tokin, & Okanoya, 2005). ...
Article
The unique social behavior of degus (Octodon degus) makes them a suitable animal model for social and emotional studies. Using degu pups, we examined the effects of repetitive short-term isolation on novel object exploratory behavior at 3, 4, 5, 6, and 7 weeks of age. Isolated pups were separated from their family 14 times for 30 min a day from 6–23 days post-birth. Non-isolated pups were reared with their families. A two-condition (with-mother or without-mother) object exploration test showed an isolation effect at 3 weeks. Compared with non-isolated pups, isolated pups showed longer start latency under the without-mother condition than under the with-mother condition, and less frequent contact with a novel object even when their mother was present. Non-isolated pups showed more frequent contact with the novel object under the with-mother condition than the without-mother condition. Repetitive maternal separation in early life negatively affected degu novel object exploratory behavior.
... In addition, degu demonstrate social-affective bonds across a range of developmental stages (Colonnello et al., 2011). During the daytime, the group members are above ground and coordinate their foraging activity by keeping visual contact (Ebensperger and Bozinovic, 2000;Ebensperger et al., 2002;Quirici et al., 2008;Vasquez, 1997;Colonnello, 2011) and emitting audible vocalizations (Long, 2007;Colonnello et al., 2011). They synchronize their digging activity to build complex underground burrows, their sociality is non-kin based and social networks are influenced by local conditions (Vasquez et al., 2002). ...
Article
Alzheimer's disease (AD) is a multifactorial progressive neurodegenerative disease. Despite decades of research, no disease modifying therapy is available and a change of research objectives and/or development of novel research tools may be required. Much AD research has been based on experimental models using animals with a short lifespan that have been extensively genetically manipulated and do not represent the full spectrum of late-onset AD, which make up the majority of cases. The aetiology of AD is heterogeneous and involves multiple factors associated with the late-onset of the disease like disturbances in brain insulin, oxidative stress, neuroinflammation, metabolic syndrome, retinal degeneration and sleep disturbances which are all progressive abnormalities that could account for many molecular, biochemical and histopathological lesions found in brain from patients dying from AD. This review is based on the long-lived rodent Octodon degus (degu) which is a small diurnal rodent native to South America that can spontaneously develop cognitive decline with concomitant phospho-tau, β-amyloid pathology and neuroinflammation in brain. In addition, the degu can also develop several other conditions like type 2 diabetes, macular and retinal degeneration and atherosclerosis, conditions that are often associated with aging and are often comorbid with AD. Long-lived animals like the degu may provide a more realistic model to study late onset AD.
... Reports of research on vocal repertoires of wild rodents in the literature are limited, with the majority of focus on laboratory mice and rats (Sales 2010). However, an increasing number of studies describe the varieties of calls made by wild rodents (Wilson and Hare 2004;Long 2007;Miller and Engstrom 2007;Briggs and Kalcounis-Rueppell 2011;Soltis et al. 2012;Ancillotto et al. 2017), which can have implications for monitoring and managing these species (e.g., Diggins et al. 2016). ...
Article
Most surveys for bats are conducted using mist nets in riparian areas along stream corridors. Various methods exist for deploying mist nets, but success of using different configurations has not been assessed. We tested efficiency of three configurations of mist nets during summers of 2000 and 2001 at the Milan Army Ammunition Plant (Carroll and Gibson counties) in western Tennessee. Configurations of mist nets included: I (one net placed transverse to stream), T (one net placed transverse to stream, and one net positioned perpendicular to first net in midstream), and Z (two nets positioned parallel to stream, and a center net positioned diagonally between the two nets). The study consisted of 347 net nights and 220 captures of bats (85 I, 62 T, 73 Z). Four species were captured including: 133 Lasiurus borealis, 63 Perimyotis subflavus, 15 Nycticeius humeralis, and nine Myotis austroriparius. Sex-ratios for adults were female biased, while juvenile sex-ratios were near equal. Netting results suggest that traditional I-configurations were statistically equal to T- and Z-configurations for all analyses of total captures and for the two dominant species captured: L. borealis and P. subflavus. Because the I-configuration requires less equipment and time for set-up, capturing bats in linear corridors could be optimized by using more I-nets rather than multiple net configurations.
... Several visual signals have been identified in association with male-male aggression, mating, and play behaviors (Davis, 1975;Wilson and Kleiman, 1974). A variety of vocalizations are produced, all apparently within the range of human hearing (Long, 2007;Reynolds and Wright 1979). Degus produce specific courtship calls; contact calls between mother and young; loud alarm calls; and a variety of squeaks, whistles, snorts, and whines, which are apparently related to varying levels of arousal but the specificity of which is still unknown (Braun and Scheich, 1997;Kleiman et al., 1979;Poeggel and Braun, 1996). ...
Chapter
This chapter studies the degu, its attributes, and uses as a laboratory animal species. Degus are mostly associated with the study of circadian rhythms due to their diurnal activities in the wild and they have also been established as valuable animal models in the study of a wide range of scientific areas including developmental biology, diabetes mellitus, cataracts, and Alzheimer's disease. The organ systems and physiological processes that have made the degu a useful animal model in various areas of research have been described in detail such as external features, circulatory system, and the nervous system. Due to less established laboratory colonies, much remains to be discovered regarding optimal housing, disease control, and veterinary care of the species. The chapter describes the management, husbandry, nutrition, diseases, and behavioral patterns of the degu. The degu is chosen as an animal for experimental model due to its characteristics such as complex familial and social structure and highly developed vocal repertoire. Also degus are relatively long-lived when compared to many other laboratory rodents. The research models that have been explained are thymic research, Alzheimer's disease, production of antisera, and atherosclerosis.
... The degu, a so-called "singing rat" of the Andes, is a rodent that originates in the mountainous areas of Chile. They have more than 15 sounds (Long, 2007). This species is considered suitable for musical preference studies for several reasons. ...
Article
Full-text available
Most nonhuman animals do not show selective preference for types of music, but researchers have typically employed only Western classical music in such studies. Thus, there has been bias in music choice. Degus (Octodon degus), originally from the mountain areas of Chile, have highly developed vocal communication. Here, we examined music preference of degus using not only Western classical music (music composed by Bach and Stravinsky), but also South American folk music (Chilean and Peruvian). The degus preferred the South American music to the Western classical music but did not show selective preference between the two Western classical music choices. Furthermore, the degus preferred the Chilean to the Peruvian music to some extent. In the second experiment, we examined preference for music vs. silence. Degus overall showed a preference for Chilean music over silence, but preferred silence over Western music. The present results indicate that the previous negative data for musical preference in nonhuman animals may be due to biased music selection (Krause, 2012). Our results suggest the possibility that the soundscape of an environment influences folk music created by native peoples living there and the auditory preference of other resident animals there.
... developmental stages (Colonnello et al., 2011). During the daytime, the group members are above ground and coordinate their foraging activity by keeping visual contact (Ebensperger and Bozinovic, 2000;Ebensperger et al., 2002;Quirici et al., 2008;Vasquez, 1997;Colonnello, 2011) and emitting audible vocalizations (Long, 2007;Colonnello et al., 2011). They synchronize their digging activity to build complex underground burrows, their sociality is non-kin based and social networks are influenced by local conditions (Vasquez et al., 2002). ...
Book
Neurodegenerative diseases are the most frequent cause of dementia, representing a burden for public health systems (especially in middle and middle-high income countries). Although most research on this issue is concentrated in first-world centers, growing efforts in South America are affording important breakthroughs. This emerging agenda poses new challenges for the region but also new opportunities for the field. This book aims to integrate the community of experts across the globe and the region, and to establish new challenges and developments for future investigation. We present research focused on neurodegenerative research in South America. We introduce studies assessing the interplay among genetic, neural, and behavioral dimensions of these diseases, as well as articles on vulnerability factors, comparisons of findings from various countries, and works promoting multicenter and collaborative networking. More generally, our book covers a broad scope of human-research approaches (behavioral assessment, neuroimaging, electromagnetic techniques, brain connectivity, peripheral measures), animal methodologies (genetics, epigenetics, proteomics, metabolomics, other molecular biology tools), species (all human and non-human animals, sporadic, and genetic versions), and article types (original research, review, and opinion papers). Through this wide-ranging proposal, we hope to introduce a fresh approach to the challenges and opportunities of research on neurodegeneration in South America.
... Reports of research on vocal repertoires of wild rodents in the literature are limited, with the majority of focus on laboratory mice and rats (Sales 2010). However, an increasing number of studies describe the varieties of calls made by wild rodents (Wilson and Hare 2004;Long 2007;Miller and Engstrom 2007;Briggs and Kalcounis-Rueppell 2011;Soltis et al. 2012;Ancillotto et al. 2017), which can have implications for monitoring and managing these species (e.g., Diggins et al. 2016). ...
Article
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Studies determining and categorizing ultrasonic calls in mammals have generally been limited to laboratory experiments with mice and rats or field research on bats. However, recent studies have discovered high-frequency sounds in several mammalian taxa. We describe the vocal repertoire of high-frequency calls in two species of North American flying squirrels (Glaucomys sabrinus and G. volans). We collected passive recordings from captive colonies of G. sabrinus and G. volans to generate a library of calls for each species. Using visual and auditory assessments, as well as quantitative measurements (i.e., spectral and temporal characteristics), we identified 10 specific call-types for G. sabrinus and 27 specific call-types for G. volans. The most common call-types emitted by G. sabrinus included arc chirps, tonal chirps, two-toned chirps, trills, and upsweeps; and for G. volans included arc chirps, barks, descending crows, tonal chirps, and trills. Additionally, we recorded two call-types made by G. volans juveniles: trills and tonal chirps. Most call-types emitted by G. sabrinus were also emitted by G. volans, showing overlap in the repertoire of both species, although variation between species is evident in certain call-types. We also found both species displayed evidence of frequency alteration (i.e., modification of the frequency of one squirrel's call when simultaneously calling with another squirrel using similar call-types). Our call library demonstrates a complex vocal range of tonal and frequency-modulated calls emitted by both species. Acoustic detection of North American flying squirrels is a new monitoring technique that can be used for conservation and management purposes. Differences in the trills, tonal chirps, and arc chirps provide a means to distinguish calls between these species. Increasing understanding of behavior associated with vocalizations may provide a more complete understanding of flying squirrel ecology, including intra-and interspecific interactions.
... In this context, we contrasted the effects of a classic total social isolation procedure in Octodon degus with the effects of relatively unexplored restricted reunion procedures on later socioemotional development of young degus. We chose to study this precocial species because of its rich social vocal repertoire (Long, 2007) and the fact that degu pups, unlike most common laboratory rodents, choose to remain in the natal environment for extended periods following adolescent development. Also, infant DVs in degus are modulated by availability of social stimuli: familiar odor cues trigger DVs and brief reunions with the mother or even unfamiliar females prior to reisolation episodes can counteract time-dependent decreases of isolation calls (Fuchs et al., 2010). ...
Article
Full-text available
Octodon degus is a social caviomorph species that exhibits strong social bonds and robust distress responses to maternal separation. To understand the impact of early social isolation on social motivation, we investigated how social isolation during infancy, associated with repeated restricted interactions with mother and siblings, altered social motivation in young degus. In Experiment 1, three treatments were compared: complete isolation (ISOLATED group), nearly complete isolation, with daily half hour partition-restricted reunions with the mother and siblings (RESTRICTED group), and social-housing with the mother and siblings (FAMILY group). After 10 days of treatment, all subjects underwent a 5-day choice test between mothers and unfamiliar females. During the treatment period, the RESTRICTED animals emitted more isolation calls and spent more time close to the partition that separated them from mothers than ISOLATED animals. During the first social-choice day, FAMILY reared animals showed a preference for the mother for a few minutes, while the RESTRICTED animals preferred the mother for the whole session. Totally ISOLATED pups exhibited no social preferences. Since during successive testing periods the isolation calls decreased over the days, in Experiment 2 we investigated whether this decline was related to age or habituation to testing procedures. Animals were observed during a single exposure to isolation (ISOLATED) or restricted-reunion (RESTRICTED) at PND 21 and 31. The decrease of vocalizations was due to an age-effect. The findings clarify the nature of social bonds in degus. ß 2011 Wiley Periodicals, Inc. Dev Psychobiol 53: 657-669, 2011.
... In this context, we contrasted the effects of a classic total social isolation procedure in Octodon degus with the effects of relatively unexplored restricted reunion procedures on later socioemotional development of young degus. We chose to study this precocial species because of its rich social vocal repertoire (Long, 2007) and the fact that degu pups, unlike most common laboratory rodents, choose to remain in the natal environment for extended periods following adolescent development. Also, infant DVs in degus are modulated by availability of social stimuli: familiar odor cues trigger DVs and brief reunions with the mother or even unfamiliar females prior to reisolation episodes can counteract time-dependent decreases of isolation calls (Fuchs et al., 2010). ...
Article
Octodon degus is a social caviomorph species that exhibits strong social bonds and robust distress responses to maternal separation. To understand the impact of early social isolation on social motivation, we investigated how social isolation during infancy, associated with repeated restricted interactions with mother and siblings, altered social motivation in young degus. In Experiment 1, three treatments were compared: complete isolation (ISOLATED group), nearly complete isolation, with daily half hour partition-restricted reunions with the mother and siblings (RESTRICTED group), and social-housing with the mother and siblings (FAMILY group). After 10 days of treatment, all subjects underwent a 5-day choice test between mothers and unfamiliar females. During the treatment period, the RESTRICTED animals emitted more isolation calls and spent more time close to the partition that separated them from mothers than ISOLATED animals. During the first social-choice day, FAMILY reared animals showed a preference for the mother for a few minutes, while the RESTRICTED animals preferred the mother for the whole session. Totally ISOLATED pups exhibited no social preferences. Since during successive testing periods the isolation calls decreased over the days, in Experiment 2 we investigated whether this decline was related to age or habituation to testing procedures. Animals were observed during a single exposure to isolation (ISOLATED) or restricted-reunion (RESTRICTED) at PND 21 and 31. The decrease of vocalizations was due to an age-effect. The findings clarify the nature of social bonds in degus.
... The degus have complex auditory communication (Long 2007), and their hearing range is similar to that of humans (Braun et al. 2003). Ground squirrels, diurnal animals, displayed anti-predatory behavior against the sound of rattling (Owings et al. 2002). ...
Article
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Phobia against spiders or snakes is common in humans, and similar phobia-like behaviors have been observed in non-human animals. Visual images of snakes elicit phobia in humans, but sensory modalities that cause snake aversion in non-human animals are not well examined. In this study, we examined visually induced snake aversion in two rodent species. Using a three-compartment experimental chamber, reactions to images of snakes were compared between the diurnal precocious rodent Octodon degus and nocturnal laboratory mice. The snakes whose images were presented do not live in the original habitats of degus or mice. Snake aversion was assessed by presenting snake vs. no-image, snake vs. flower, snake vs. degu, and snake vs. mouse images. The time spent in a compartment with the snake image and with the non-snake images were measured. Degus avoided images of snakes in every tests. In contrast, mice did not display snake aversion. Degus are diurnal animals, i.e., visual information is important for their survival. Since mice are nocturnal, visual information is less important for survival. Such behavioral differences in the two species may explain the difference in visually induced aversion to snakes. A principal component analysis of the stimulus images suggests that elementary cues, such as color, do not explain the differences in the species’ aversion to snakes. Finally, snake aversion in degus suggests that aversion is innate, since the animals were born and raised in a laboratory.
... Given that the resting-associated vocalization in the Asian house shrew is quite noticeable, it is interesting that apart from two more white-toothed shrews [17,19] and the Senegal bush baby [18], there is not much evidence in the literature [see, e.g., [6], [43], [44], [45]] suggesting that this vocalizationis a common part of the vocal repertoires of other small mammals (but see Credner et al. [46] for a description of tooth grinding recorded in adult resting and sleeping mole rats Cryptomys sp.). Is this type of vocalization indeed a rare phenomenon occurring in some captive colonies or specific taxa only, or has it remained undetected in some species? ...
Article
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Shrews have rich vocal repertoires that include vocalizations within the human audible frequency range and ultrasonic vocalizations. Here, we recorded and analyzed in detail the acoustic structure of a vocalization with unclear functional significance that was spontaneously produced by 15 adult, captive Asian house shrews (Suncus murinus) while they were lying motionless and resting in their nests. This vocalization was usually emitted repeatedly in a long series with regular intervals. It showed some structural variability; however, the shrews most frequently emitted a tonal, low-frequency vocalization with minimal frequency modulation and a low, non-vocal click that was clearly noticeable at its beginning. There was no effect of sex, but the acoustic structure of the analyzed vocalizations differed significantly between individual shrews. The encoded individuality was low, but it cannot be excluded that this individuality would allow discrimination of family members, i.e., a male and female with their young, collectively resting in a common nest. The question remains whether the Asian house shrews indeed perceive the presence of their mates, parents or young resting in a common nest via the resting-associated vocalization and whether they use it to discriminate among their family members. Additional studies are needed to explain the possible functional significance of resting-associated vocalizations emitted by captive Asian house shrews. Our study highlights that the acoustic communication of shrews is a relatively understudied topic, particularly considering that they are highly vocal mammals.
Article
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Primates are intensely social and exhibit extreme variation in social structure, making them particularly well suited for uncovering evolutionary connections between sociality and vocal complexity. Although comparative studies find a correlation between social and vocal complexity, the function of large vocal repertoires in more complex societies remains unclear. We compared the vocal complexity found in primates to both mammals in general and human language in particular and found that non-human primates are not unusual in the complexity of their vocal repertoires. To better understand the function of vocal complexity within primates, we compared two closely related primates (chacma baboons and geladas) that differ in their ecology and social structures. A key difference is that gelada males form long-term bonds with the 2-12 females in their harem-like reproductive unit, while chacma males primarily form temporary consortships with females. We identified homologous and non-homologous calls and related the use of the derived non-homologous calls to specific social situations. We found that the socially complex (but ecologically simple) geladas have larger vocal repertoires. Derived vocalizations of geladas were primarily used by leader males in affiliative interactions with 'their' females. The derived calls were frequently used following fights within the unit suggesting that maintaining cross-sex bonds within a reproductive unit contributed to this instance of evolved vocal complexity. Thus, our comparison highlights the utility of using closely related species to better understand the function of vocal complexity.
Article
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Soricids produce a considerable variety of vocalizations. However, these calls have been studied insufficiently with the exception of echolocation calls. In this study, 1,645 calls from 18 juvenile, ten sub-adult and 36 adult Asian house shrews (Suncus murinus) were acoustically and statistically analyzed to describe this species’ vocal repertoire and its ontogeny. The vocal repertoire of S. murinus includes 17 call types, seven tonal (whistle, chirp, twitter, whimper, squeak, scream and short scream) and ten non-tonal (churr, shriek, babble, click, boom, snort, screech, short screech, sniff and low click), of which ten call types (whimper, squeak, scream, short scream, churr, babble, snort, short screech, sniff and low click) were newly described by this study. This relatively extensive vocal repertoire, including one call type emitted during collective resting, indicates that this species possibly possesses a higher degree of sociality and cohesiveness than previously expected. High structural similarities were observed between calls produced by juveniles and sub-adults during caravanning and those produced by adult males during courtship. Therefore, the results of this study support a previously suggested hypothesis that in shrews, adult courtship calls are derived from calls emitted by the young. The results of this study also showed that the largest changes in the ontogeny of the vocal repertoire occurred at approximately 10 days old and was in close connection to the eyes opening. The results are discussed with available information on the vocal repertoires of other soricids.
Preprint
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Social separation is thought to induce a strong stress response in social juvenile mammals, but little is known about how this response might vary throughout the development. The present study examines the long-term effects of early-life stress (ELS) induced by social separation on individual behaviors later in life using the social and precocious species Octodon degus . Four experimental groups were established a positive control group of mothers and siblings from three litters comprised the socially housed (SH) group, while pups from six litters were randomly assigned to three treatments: pups experiencing no separation (NS) treatment while their siblings did; repeated bouts of consecutive separation (CS); intermittent separation (IS). We analyzed the effects of separation treatment on the frequency and duration of freezing, rearing and grooming behaviors. ELS was correlated with higher hyperactivity later in life, especially in developed males, and hyperactivity increased with more frequent separation. The SH group containing siblings that did not experience parental separation gained more weight than the other groups. The findings suggest that the NS group was indirectly affected by ELS, especially females. In summary, the long-term effects of ELS are more direct in males while those are more indirect in females.
Article
Previous research into the juvenile vocalisations of the degu (Octodon degus), a semi-fossorial caviomorph rodent from central Chile, revealed interesting features of the calls used to elicit care from an adult, suggesting features present in the ultrasonic region. Here, it is determined that such vocalisations can include frequencies from 2.8 - 61.6 kHz, demonstrating ultrasonic harmonics well above the range that was previously recorded, although most energy is contained within the 10 kHz region. This provides the first reported case of ultrasound production by the species. These 'loud whistle' calls were found to have properties that varied significantly between behavioural contexts and between litters, suggesting the potential for individual litter and context recognition by adult degus. Features of the vocalisation such as duration were found to vary significantly with pup age, indicating changes to the qualities with pup growth and development. Finally, the recommended recording range for this species is given as 20 Hz - 65 kHz.
Chapter
Caviomorph rodents show a large diversity of living forms, with many social species, showing a large spectrum of cooperative behaviors. This chapter begins by reviewing the four mechanisms proposed for the evolution of cooperative behaviors, namely, kin selection, by-product mutualism, reciprocity, and group selection. Thereafter, it reviews examples of cooperative behaviors observed in caviomorph species, comprising anti-predator vigilance, communal breeding, and kin-biased behaviors. The review shows that most studies on cooperative behavior have been carried out in a few species, highlighting Octodon degus as the most studied species. Several studies have assessed antipredator vigilance within social groups, though results so far show that changing vigilance levels according to group size seems to be a group size effect rather than a cooperative strategy. Communal breeding is a commonly observed social system where some individuals provide care for offspring that are not their own, and several behaviors seem to be kin selected, though several studies show contradictory results. Future research should tackle a range of ecological conditions, using intra- and inter-specific studies.
Article
Some animals learn to fear a situation after observing another individual come to harm, and this learning is influenced by the animals’ social relationship and history. An important but sometimes overlooked factor in studies of observational fear learning is that social context not only affects observers, but may also influence the behavior and communications expressed by those being observed. Here we sought to investigate whether observational fear learning in the degu (Octodon degus) is affected by social familiarity, and the degree to which vocal expressions of alarm or distress contribute. ‘Demonstrator’ degus underwent contextual fear conditioning in the presence of a cagemate or stranger observer. Among the 15 male pairs, observers of familiar demonstrators exhibited higher freezing rates than observers of strangers when returned to the conditioning environment one day later. Observer freezing during testing was, however, also related to the proportion of short- versus long- inter-call-intervals (ICIs) in vocalizations recorded during prior conditioning. In a regression model that included both social relationship and ICI patterns, only the latter was significant. Further investigation of vocalizations, including use of a novel, directed k-means clustering approach, suggested that temporal structure rather than tonal variations may have been responsible for communicating danger. These data offer insight into how different expressions of distress or fear may impact an observer, adding to the complexity of social context effects in studies of empathy and social cognition. The experiments also offer new data on degu alarm calls and a potentially novel methodological approach to complex vocalizations.
Chapter
This chapter introduces representative studies in acoustic communication in rodents. By using rodents as a model in which to study the evolution of vocal communication, researchers are able to utilize their diversity in physical habitats, social complexity, and sexual rituals. The widespread use of rodents as subjects of acoustic communication research is largely because many such species are the most successful mammalian group in terms of speciation. Much attention has been paid to isolation calls, alarm calls, and contact (or signature) calls in several species of rodents, with emphasis on the physical, social, and sexual variables involved in their production. Emergence of song-like vocalizations in both mother-infant contexts and male-female mating contexts are also discussed. Furthermore, the chapter focuses on the degree of plasticity in perception, production, and usage of these vocalizations in relation to the organization of neural structures related to hearing and vocalizations in rodents. Finally, these observations are integrated to suggest a general hypothesis on the evolution of vocal communication in rodents.
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Guinea pigs, chinchillas, and degus are rodent members of the class Mammalia, order Rodentia, suborder of hystricomorphs, and parvorder of caviomorpha. All three species were originally kept for reasons other than as companions: the guinea pig for food, the chinchilla for fur, and the degu for laboratory use as a model for diabetes. These species all need the company of their own species. Living in social groups can provide better vigilance for predators and opportunities for play and mutual grooming. Caviomorphs may find handling stressful, especially if they have had limited or negative experiences. Gastrointestinal disease is common in all three species, often linked to an inadequate diet. The best method of euthanasia is usually sedation if needed, followed by the injection of an overdose of pentobarbitone into a vein. Stress‐related behaviours and health conditions include over‐ or under‐eating, pica, over‐ or under‐grooming, repetitive behaviours, and aggression either to other animals or humans.
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A full understanding of a species' sociality requires knowledge of their specific social motivations. Following social isolation, animals may show general interest in companionship as a buffer for stress or loneliness, but may also be driven to re-establish expectations and dyadic roles with individuals they had been previously separated from. By deconstructing social behavior across experimental manipulations, it may become possible to disentangle these motivational factors. Physical and vocal interactions were recorded from adult female degu dyads during a series of 20 minute reunion sessions across four experiments. Experiments 1 and 2 found that degu interactions increased following isolation, but also increased after dyads were separated without isolation from other conspecifics. Isolation resulted in more early-session interactions, higher allogrooming before rear-sniffing, and a higher ratio of chitter to non-chitter vocalizations. Experiment 3 showed that a non-social, footshock stressor selectively increased early-session interaction, and Experiment 4 revealed high interaction rates between strangers, with more non-chitter vocalizations and late-session rear-sniffing, and reduced pre-rear-sniff allogrooming. A novel, repeated-k-means clustering approach helped to further specify differences in vocalizations between conditions; e.g., "chaff"-type syllables were more common when relationships were new or potentially being renewed. Results suggest that degus are motivated to establish or re-establish expectations with one-another, and these interactions can differ from those associated with the stress of isolation.
Article
Octodon degus is said to be one of the most human-like rodents because of its improved cognitive function. Focusing on its high sociality, we cloned and characterized some sociality-related genes of degus, in order to establish degus as a highly socialized animal model in molecular biology. We cloned degus Neurexin and Neuroligin as sociality-related genes, which are genetically related to autism spectrum disorder in human. According to our results, amino acid sequences of Neurexin and Neuroligin expressed in degus brain, are highly conserved to that of human sequences. Most notably, degus Neuroligin4 is highly similar to human Neuroligin4X, which is one of the most important autism-related genes, whereas mouse Neuroligin4 is known to be poorly similar to human Neuroligin4X. Furthermore, our work also indicated that testosterone directly binds to degus Neurexin and intercepts intercellular Neurexin-Neuroligin binding. Moreover, it is of high interest that testosterone is another key molecule of the higher incidence of autism in male. These results indicated that degus has the potential for animal model of sociality, and furthermore may promote understanding toward the pathogenic mechanism of autism.
Article
Complex social play is well-documented across many animals. During play, animals often use signals that facilitate beneficial interactions and reduce potential costs, such as escalation to aggression. Although greater focus has been given to visual play signals, here we demonstrate that vocalisations constitute a widespread mode of play signalling across species. Our review indicates that vocal play signals are usually inconspicuous, although loud vocalisations, which suggest a broadcast function, are present in humans and some other species. Spontaneous laughter in humans shares acoustic and functional characteristics with play vocalisations across many species, but most notably with other great apes. Play vocalisations in primates and other mammals often include sounds of panting, supporting the theory that human laughter evolved from an auditory cue of laboured breathing during play. Human social complexity allowed laughter to evolve from a play-specific vocalisation into a sophisticated pragmatic signal that interacts with a large suite of other multimodal social behaviours in both intragroup and intergroup contexts. This review provides a foundation for detailed comparative analyses of play vocalisations across diverse taxa, which can shed light on the form and function of human laughter and, in turn, help us better understand the evolution of human social interaction.
Article
Previous studies of rodents reported that the hippocampus plays an important role in social behavior as well as spatial behavior. However, there are inconsistencies between reports of the effects of hippocampal lesions on social behavior. The present study sought to clarify the aspects of social behavior in which the hippocampus plays a role in the degu, Octodon degus, a social rodent. We examined the effects of hippocampal lesions on social behavior in the degu using familiar and novel partners. When placed in a familiar environment with a familiar partner after surgery, sham operation control (S.Cont) degus exhibited affinitive behavior longer compared with hippocampal lesioned (HPC) degus. In a novel environment, S.Cont degus exhibited longer aggressive behavior toward novel partners, and longer affinitive behavior with familiar partners compared with HPC degus. HPC degus did not show evidence of differentiation in social behavior, regardless of partner's novelty. The results of an anxiety test confirmed that these findings could not be attributed to changes in emotional state. We conducted an object-recognition test with the same subjects. HPC degus showed an impairment in spatial recognition but not object recognition. Taken together, these results suggest that the degu hippocampus plays an important role not only in spatial recognition but also social recognition. The changes in social behavior resulting from hippocampal lesions were interpreted as due to an impairment of social recognition rather than an impairment in novelty detection.
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A previous experiment suggested that male degus, Octodon degus, use dustbathing during intrasexual communication. Herein, we assessed whether dustbathing by male and female degus is influenced by the social familiarity of previous marks. During 15-min tests, we contrasted the behavior of degus individually exposed during to an arena containing loose, previously dustbathed sand by a same-sex and socially familiar individual with that of degus exposed to an arena with soil previously dustbathed by a same-sex but socially unfamiliar conspecific. We measured the number of dusbathing eventts per min, the latency of first dusbathing event, and the location of dusbathing events by depositor and responser individuals. Both male and female degus dusbathe at a higher rate when subjected to soil previously used by a familiar conspecific tha when exposed to a substratum previously dusbathed by an unfamiliar degu. The latency of first dusbathing event by responser male or female degu was unaffected by the social familiarity of previous marks left by depositors. Similary, the place chosen by male and female responders to conduct their dusbathing behavior was unrelated to the micro-location of previous marks left by a familiar or an unfamiliar depositor degu. We conclude that degus are capable of discriminating socially familiar fron unfamiliar scents of conspecifics and deposited in the substratum during dusbathing . We discuss the implications of such ability in the context of degu social bahavior.
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A colony of approximately 150 adult and infant guinea-pigs was studied in order to investigate the structure, causation and function of guinea-pig vocalizations. Behaviour and sound recordings were made in a wide variety of contexts and sounds were analysed on the Kay Electric Sonagraph 6061 B. Sonagrams were measured, and on the basis of physical structure alone, 11 call types were distinguished. Behavioural records were examined and it was suggested that 5 functional categories existed. The significance of vocal communication in guinea-pig social behaviour was discussed. Meerschweinchenlaute wurden in Tonbandaufnahmen und Sonagrammen analysiert. Die Laute wurden in verschiedenen Situationen, sowohl von Einzeltieren als auch in Gruppen aufgenommen. Die Versuchstiere waren zum Teil einzeln, zum Teil in Gruppen verschiedener Größe aufgezogen worden. Aufgrund der Sonagramme konnten die Rufe in 11 strukturell verschiedene Kategorien aufgeteilt werden. Die Situationen, in welchen diese Rufe auftreten, werden beschrieben. Es wird vorgeschlagen, die Laute wie folgt in 5 funktionelle Gruppen zusammenzufassen: Rufe, welche (1.) intimen Kontakt bewirken, (2.) sozialen Kontakt bewahren, (3.) andere Tiere aus größerer Distanz anlocken, sowie (4.) Jammerund (5.) Warnrufe.
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The number of turns in the cochlear spiral and length of the basilar membrane in several mammalian species were compared with the octave range and the high-and low-frequency limits of hearing. Basilar membrane length and the number of spiral turns were not related. Among ground dwelling mammals, the number of turns in the cochlear spiral was more strongly related to octave range than was basilar membrane length. Basilar membrane length was inversely related to the high-and low-frequency limits of hearing. The best estimates of high-and low-frequency limits and octave range were derived from formulas which included both the number of turns in the cochlear spiral and the basilar membrane length as factors. The number of turns in the cochlear spiral was most highly correlated with the difference between the low-frequency limit of hearing and the lowest frequency mechanically analyzed by the traveling-wave envelope, peak-shift property of the basilar membrane [von Békésy, Experiments in Hearing (McGraw-Hill, New York, 1960)]. The coefficient of correlation for the number of spiral turns and the octave difference between the lowest audible frequency and the lowest frequency distributed as a unique point of maximum displacement along the basilar membrane was r = 0.997 (P less than .001) at 60 dB SPL. Mechanisms by which the spiral form of the cochlea may affect the motion of hair cells and the selective response of the tectorial membrane to differences among traveling-wave envelope slopes and peak locations were reviewed. It was proposed that in ground dwelling mammals, the spiral form of the cochlea extends the octave range of hearing and that through mechanisms such as these increases the sensitivity of the cochlea to frequencies below the low-frequency peak-shift limit of the basilar membrane.
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A series of tests were conducted to determine whether infant degus (Octodon degus) will (a) show sensitivity to maternal olfactory cues and/or (b) discriminate between a novel adult lactating female and their mother. The pups showed no preferences when exposed to an array of different olfactory stimuli but did spend significantly more time in proximity with the novel lactating female than with their mothers. It is hypothesized that the communal rearing systems which are apparently characteristic of degus in the wild, coupled with the novelty of the lactating female, may account for these results.
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Degu mothers (Octodon degus) utter specific maternal calls during nursing which presumably stimulate and reinforce suckling. Pups from surgically muted mothers show a reduced gain of body weight during postnatal development compared to pups from normally vocalizing mothers. Our behavioral studies suggest that the pups have to learn the meaning of the maternal calls during the first two weeks of life. Two-week-old pups from normally vocalizing mothers expressed a preference for the maternal call in a behavioral discrimination test, in contrast to pups from surgically muted mothers. Investigation of brain activities using the 2-[14C]fluoro-deoxyglucose (2-FDG) method revealed that pups from normal mothers display a significantly higher 2-FDG uptake in precentral medial, anterior cingulate cortex and a slight, non-significant increase in the prelimbic cortex and orbital PFC upon presentation of the maternal call, compared to pups from muted mothers, for which the maternal call was unfamiliar and meaningless. These prefrontal cortical areas are known to be involved in associative learning processes and our data suggest that they are involved in the association between the maternal call and the positive emotional situation during nursing.
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Several types and subtypes of vocalizations which have a behavioral impact on degu pups were identified. Among these the complex "mothering call" which is exclusively uttered by females and first during extensive nursing periods in the nest is a candidate for filial learning. In 14C-2-fluoro-2-deoxyglucose (FDG) experiments two-weeks-old pups raised by normal mothers showed higher metabolic activity in somatosensory frontoparietal and frontal cortex upon play back of a mothering call than pups raised by muted mothers. It is suggested that pups learn to associate the mothering call with close body contact with their mother early in life. In addition, FDG representation of the call, of its components and of tone and noise stimuli were studied in degu auditory cortex. Five fields and some aspects of tonotopic organization were identified. The mothering call activated all fields, but with more spatial extent of labeling in normally raised pups. A rostral field was activated by play-back of the mothering call, noise, and two-tone sequences, but hardly by single-frequency tones and the narrow-band component of the mothering call.
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In a variety of animal species, including primates, vocal communication is an essential part to establish and maintain social interactions, including the emotional bond between the newborn, its parents and siblings. The aim of this study in pups of the trumpet-tailed rat, Octodon degus, was to identify cortical and subcortical brain regions, which are involved in the perception of vocalizations uttered by the mother. In this species, which is characterized by an elaborated vocal repertoire, the (14C)-2-fluoro-deoxyglucose autoradiography was applied to measure region-specific metabolic activation in response to the presentation of a learned emotionally relevant acoustic stimulus, the maternal calls. Already at the age of eight days the precentral medial cortex, anterior cingulate cortex and the lateral thalamus could be identified by their enhanced metabolic activation in response to the presentation of the emotionally relevant maternal nursing calls, whereas other brain areas, such as the hippocampus and amygdala did not show stimulus-induced activation. Since in humans changes of activity patterns in relation to the emotional content of spoken language have been observed in similar brain regions, e.g. in the anterior cingulate cortex, Octodon degus may provide a suitable animal model to study the cellular and synaptic mechanisms underlying perception, production and processing of conspecific vocalizations.
Article
Repeated separation from the family during very early stages of life is a stressful emotional experience which induces a variety of neuronal and synaptic changes in limbic cortical areas that may be related to behavioral alterations. First, we investigated whether repeated parental separation and handling, without separation from the family, leads to altered spontaneous exploratory behavior in a novel environment (open field test) in 8-day-old Octodon degus. Second, we tested whether the parentally deprived and handled animals display different stimulus-evoked exploratory behaviors in a modified open field version, in which a positive emotional stimulus, the maternal call, was presented. In the open field test a significant influence of previous emotional experience was found for the parameters of running, rearing, and vocalization. Parentally deprived degus displayed increased horizontal (running) and vertical (rearing) motoric activities, but decreased vocalization, compared to normal and handled controls. The presentation of maternal vocalizations significantly modified running, vocalization, and grooming activities, which in the case of running activity was dependent on previous emotional experience. Both deprivation-induced locomotor hyperactivity together with the reduced behavioral response towards a familiar acoustic emotional signal are similar to behavioral disturbances observed in human attachment disorders.
Article
Although the potential vulnerability of the postnatally developing brain toward adverse environmental influences is generally recognized, relatively little is known about the basic mechanisms involved. The plasticity and adaptability of the postnatally developing brain in response to adverse emotional experiences was analyzed in the South American Octodon degus. Our study revealed that repeated brief separation from the parents and exposure to an unfamiliar environment induces an up-regulation of dopamine (D1) and 5-hydroxytrytamine (5HT1(A))-receptor density in the precentral medial, anterior cingulate, prelimbic and infralimbic cortices in female pups. No significant changes of gamma aminobutyric acid (GABA(A)) receptor density were found in deprived animals of both genders. The acoustic presence of the mother during parental separation suppressed the D1-receptor up-regulation as well as the 5-HT1(A)-receptor up-regulation, again only in the female pups. These results demonstrate that that early adverse emotional experience alters aminergic function within the prefrontal cortex in the female but not the male brain. The mother's voice, a powerful emotional signal, can protect the developing cortex from separation-induced receptor changes.
Article
Unlabelled: The development of adult circadian function, particularly sexual dimorphism of function, has been well studied only in rapidly developed rodents. In such species development is complete by weaning. Data from adolescent humans suggest that significant development occurs during the pubertal period. We hypothesized that a more slowly developing rodent might better mimic the changes in circadian function around puberty in humans and allow us to determine the underlying neural changes. Entrained and free-running circadian rhythms were analyzed and correlated with pubertal development in male and female Octodon degus (degu) that remained gonadally intact or were gonadectomized at weaning. Brains were collected during development to measure androgen and estrogen receptors in the suprachiasmatic nuclei (SCN) Adult circadian period does not develop until 10-12 months of age in degus, long after the onset of gonadal maturation (3-5 months). The timing of circadian period maturation correlates with the appearance of steroid receptors in the SCN. Changes in free-running rhythms only occurred in gonadally intact degus. Adult phase angles of activity onset develop between 2 and 3 months of age (comparing results of two experiments), soon after the onset of pubertal changes. Conclusion: The development of sexually dimorphic adult circadian period occurs after gonadal puberty is complete and requires the presence of gonadal steroids. The delay in development until after gonadal puberty is likely due to the delayed appearance of steroid receptors in the SCN. Phase is not sexually dimorphic and changes in the absence of steroid hormones.
Article
Relatively little is known about the basic mechanisms that play a role in the vulnerability of the developing brain toward adverse environmental influences. Our study in the South American rodent Octodon degus revealed that repeated brief separation from the parents and exposure to an unfamiliar environment induces in the hippocampal formation of male and female pups an upregulation of D1 and 5-HT1A receptor density in the stratum radiatum and stratum lacunosum moleculare of the CA1 region. In the CA3 region, only the 5-HT1A receptors were upregulated; no changes were observed for D1 receptors in this region. GABA(A) receptor density in the hippocampus and amygdala was downregulated (nonsignificant trend) after parental separation. The acoustic presence of the mother during parental separation suppressed the D1 and 5-HT1A receptor upregulation in some regions of the hippocampus; no such suppressing influence was observed for the GABA(A) receptors. In the basomedial amygdala, the maternal calls enhanced the separation-induced 5-HT1A receptor upregulation in the male pups, whereas in the female pups the separation-induced receptor densities were not only suppressed by the maternal call but further downregulated, compared with the control group. These results demonstrate that early adverse emotional experience alters aminergic function within the hippocampus and amygdala and that the mother's voice, a powerful emotional signal, can modulate these effects in the developing limbic system.
Ecoetología de Octodon degus
  • J Yáñez
Yáñez, J. (1976) Ecoetología de Octodon degus. Batchelor in Sciences Thesis, Universidad de Chile, Santiago: 67pp.
Learned relevance of species-specific vocalisations and their 14C-2-DG pattern in auditory cortex of the degu (Octodon degus)
  • S Braun
  • H Scheich
Braun, S. & Scheich, H. (1991) Learned relevance of species-specific vocalisations and their 14C-2-DG pattern in auditory cortex of the degu (Octodon degus). 21st Annual meeting of the Society of Neuroscience, 2 (559.17), 1404.
Octodon degus. Mammalian Species
  • C Woods
  • D Boraker
Woods, C. & Boraker, D. (1975) Octodon degus. Mammalian Species, 67, 1-5.