BIOACOUSTICS OF DOMESTICATION: ALARM AND COURTSHIP CALLS OF WILD AND DOMESTIC CAVIES

ABSTRACT

Comparisons of wild (Cavia aperea) and domestic (C. porcellus) cavies promote an understanding of the physiological and behavioral effects of domestication. The richness and peculiarities of Cavia acoustic repertoires encourage the use of this model for testing how domestication alters repertoires and the physical structure of calls. We present a comparison between alarm and courtship calls of domestic and two populations of wild cavies from different geographic regions, one of them with a short-term captivity history of 25 generations. We found significant differences between domestic and wild cavies in both calls, particularly in temporal parameters, and only spectral differences between two wild populations in alarm calls. There were also differences in the frequency of emission of calls: alarm calls were more frequent in the wild and courtship calls were more frequent in the domestic species. Our results suggest that domestication has influenced the temporal parameters of both alarm and courtship calls of C. porcellus, but not the spectral parameters that, instead, may be influenced by environment or population factors.     

New findings on the origin of Cavia intermedia,one of the world's rarest mammals

Cavia intermedia, a rare species of cavy found exclusively on Moleques do Sul Island, Brazil, differs from other cavies in genetic and morphological characteristics and has been regarded as phylogenetically closest to Cavia magna. Here, I present morphological evidence for the likely origin of Cavia intermedia from an ancestor shared with Cavia magna: an external female genital organ similar in size and appearance to the male's penis. Masculinization of the female genitalia has been observed in Cavia magna but does not occur in Cavia aperea, which suggests a sister relationship between Cavia magna and Cavia intermedia.     

A new karyotype for <Emphasis Type="Italic">Cavia magna</Emphasis> (Rodentia: Caviidae) from an estuarine island and <Emphasis Type="Italic">C. aperea</Emphasis> from adjacent mainland

We describe a new karyotype for Cavia magna Ximenez, 1980 from an estuarine island and the karyotype of Cavia aperea Erxleben, 1777 from an adjacent mainland. The species have differences in diploid number (2n), autosomal fundamental number, quantity, and distribution of heterochromatin as dissimilar distributions of the nucleolus-organizing regions (Ag-NORs). The C. aperea karyotype has a diploid number of 64 as previously reported for C. aperea and most other Cavia species. In contrast, this new C. magna karyotype exhibits a variant diploid number of 2n = 62, considering that previous work reported a karyotype of 2n = 64 for C. magna. The discovery of a distinct diploid number within C. magna represents the first record of intra-specific chromosomal variation in a species of Caviidae. The diploid number of 2n = 62, heterochromatin quantity, Ag-NOR distributions, and inversed X chromosome from this population of C. magna are as seen in the geographically proximate (Cavia intermedia Cherem Olimpio and Ximenez; intermediate Cavy). These data provide further evidence supporting C. magna as the sister species of C. intermedia.     

Genetic variation of phosphoglucose isomerase in some hystricomorph rodents

Phosphoglucose isomerase electrophoretic variation has been studied in hystricomorph rodents. Intraspecies variation was found in chinchilla (Chinchilla laniger) and cuis (Galea musteloides). Interspecies hybridization of Cavia aperea and Cavia porcellus was found to produce hybrid enzymes. In all cases, breeding data indicated an autosomal mode of inheritance, while electrophoretic patterns were consistent with a dimeric structure for the enzyme. Possible evolutionary relationships of phosphoglucose isomerase with respect to taxonomy are discussed.The laboratory studies were supported by the Royal Society and Agricultural Research Council (N. D. C. and M. R. H.) and the Ford Foundation (B. J. W.).     

Molecular systematics,taxonomy and biogeography of the genus Cavia (Rodentia: Caviidae)

Phylogenetic analyses were conducted on cytochrome b sequence data of the most geographically and taxonomically broad sampling of Cavia taxa to date. Primary objectives included providing the first extensive molecular phylogenetic framework for the genus, testing the taxonomic and systematic hypotheses of previous authors and providing insight into the evolutionary and biogeographic history of the genus. Support was found for the morphologically defined species C. aperea, C. tschudii, C. magna and C. fulgida and the taxonomic placement of taxa previously subject to conflicting taxonomic opinions (e.g. C. nana, C. anolaimae and C. guianae) was further resolved. Additionally, we elevate the Ecuadorian C. a. patzelti to species status, restrict the distributional limits and suggest taxonomic affiliations of some C. tschudii subspecies, and provide strong evidence for the geographic origin of guinea pig domestication. Finally, we provide an estimated evolutionary timeline for the genus Cavia, which appears to extend well into the late Miocene.     

Mother is not like mother: Concurrent pregnancy reduces lactating guinea pigs’ responsiveness to pup calls

Offspring signalling can serve to communicate need to the parents and thus influence parental readiness to provide care. Offspring stimuli that affect parental care have been investigated extensively. Yet much less is known about the mechanisms leading to a decline in maternal motivation when conflicts of provisioning current and future offspring may arise. Here we tested responses by pregnant and non-pregnant female guinea pigs (Cavia aperea f. porcellus) to playback of pup calls during their period of lactation for dependent offspring. Most concurrently pregnant and lactating females did not respond to pup calls, whereas non-pregnant lactating females responded strongly. Our findings expand on previous studies by showing that female behavioural responsiveness to pup stimuli is strongly reduced by concurrent pregnancy and lactation. These instantaneous measurements of female responsiveness to young show more directly than standard measures like nursing performance or time to weaning how female motivation to care for current offspring is diminished by simultaneous gestation.     

Absence of temporal pattern in courtship signals suggests loss of species recognition in gecko lizards

According to the concept of ritualization, acquisition of signal function (i.e., species recognition) leads to formalization of specific signal structure (i.e., species-specific pattern). By contrast, loss of species recognition may result in specific pattern collapse of the signal, from a temporally regular pattern to an irregular form. Several studies have reported the loss of species recognition driven by release from selective pressure against hybridization under isolation from close relatives, but no study has reported collapse of a regular signal pattern that serves in species recognition. In nocturnal lizards of the genus Gekko, several species pairs hybridize when brought together, whereas other species pairs never hybridize, despite being sympatric. I investigated the relationship between the existence of natural hybridization, courtship call similarity and species recognition ability in eight species of Gekko. I found that males of all eight species court using calls, and four of these species have species-specific regular patterns in the courtship calls, whereas the other four have no temporal patterns. In playback experiments, females of the species-specific pattern call species discriminated species by the call. On the other hand, in the patternless call species, females did not discriminate species by the call, suggesting that natural hybridization has resulted from the loss of species recognition ability in the patternless call species. In insular Gekko isolated from congeners, acoustic species recognition might have been lost, followed by pattern collapse of the courtship calls. This unique example of the signal pattern collapse would provide a key to answer basic questions concerning the causes and consequences of signal evolution.     

Mandibular movement and muscle activity during mastication in the guinea pig (Cavia porcellus)

Optoelectronic analysis of mandibular movement and electromyography (EMG) of masticatory muscles in Cavia porcellus indicate bilateral, unilateral, and gnawing cycles. During bilateral and unilateral cycles, the mandibular tip moves forward, lateral, and down during the lingual phase of the power stroke to bring the teeth into occlusion. EMG activity is generally asymmetric, with the exception of activity of the temporalis muscle during bilateral cycles. During gnawing cycles, the mandible moves in an anteroposterior direction that is opposite that during bilateral and unilateral chew cycles. Bilateral and unilateral cycles of pellets were significantly longer than carrot. With the exception of the width of bilateral cycles, the magnitude of cycle width, length, and height during the mastication of carrots was greater than that during the mastication of pellets. Significant differences exist between EMG durations during mastication of pellets and carrots. The lateral pterygoid displays continuous activity during gnawing cycles. Significant differences also exist in the durations of EMG activity between the working and balancing side during all three cycle types. High level activity of balancing side temporalis and anterior belly of digastric (ABD) during bilateral cycles occurs during rotation and depression of the mandible during the power stroke. The temporalis apparently provides a ?braking”? or compensatory role during closing and power strokes. Differences between Cavia masticatory patterns and those shown by Rattus and Mesocricetus are apparently due to differences in dental morphology, occlusal relationships, and, possibly, the poorly developed temporalis in Cavia. The large number and wide diversity of rodent groups afford students of mammalian mastication an opportunity to investigate and compare different masticatory specializations.     

Inbreeding and courtship calling in the cricket Teleogryllus commodus

Male field crickets produce two acoustic signals for mating: advertisement calls and courtship calls. While the importance of advertisement calling in mate attraction is well understood, the function of courtship calling is less clear. Here, we tested if the courtship call of male crickets Teleogryllus commodus signals aspects of male quality by comparing the calls of inbred and outbred males. We examined the effect of one generation of full sibling mating on fine‐scale call structure, along with several life history traits. Inbreeding reduced nymph survival but had no significant effect on weight or development time. Inbreeding resulted in a small but significant change in two of the six call parameters measured. We then tested if inbreeding affects call trait combinations that are important to females by using the results of a previous selection analysis to compare the multivariate attractiveness of the calls of inbred and outbred males. There was no difference. We conclude that the courtship call of T. commodus is not a reliable signal of aspects of male quality that are affected by inbreeding (which generally reduces fitness‐enhancing traits). It might, however, signal components of male fitness that are not affected by changes in heterozygosity.     

Some Behavioural Changes Associated with the Guinea-pig Oestrous Cycle

This paper describes some behaviour patterns of the guinea-pig, Cavia porcellus, which vary systematically with the oestrous cycle. Oestrus is characterised by an increase in locomotion, and scent-marking, as well as by greater interest in conspecifics. All of these are behaviours known to increase at oestrus in other rodent species. The significance of these changes for the social organisation of this species is discussed.     

Chemical communication in Cavia: Responses of wild (C. aperea), domestic (C. porcellus) and F1 males to urine

Urine preferences of wild (Cavia aperea), domestic (C. porcellus), and F₁ adult male guinea pigs were investigated. Males of all three types preferred female urine to male urine regardless of donor type. When given a choice between female urine of each type, males preferred conspecific urine. In choices between male urine of the three types, a conspecific preference was evident for wild and domestic but not f₁ subjects. These data indicate that a loss of distinctive male and female odours has not occurred as a result of domestication. However, the urine odours of wild and domestic types have diverged. The possible effects of previous individual experience on the preferential response is discussed.     

The most ancient caviine rodent (Hystricognathi,Cavioidea) comes from the late Miocene of Northwest Argentina (South America)

The family Caviidae is one of the most diverse groups among South American hystricognath rodents and is represented by three main living lineages: Caviinae (cavies), Dolichotinae (maras) and Hydrochoerinae (capybaras). Caviinae includes the smaller forms of caviids represented by the extant Microcavia, Cavia and Galea. They are distributed in a wide range of environments throughout South America. In addition, three other genera from the late Miocene–Pliocene (Dolicavia, Palaeocavia and Neocavia) are recognised in high latitudes. In northwestern Argentina, the fossil forms of Caviinae have been poorly studied and for most of them there is no precise stratigraphic information. We describe and evaluate the phylogenetic affinities of the most ancient caviine from the Chiquimil Formation, Catamarca province, northwestern Argentina (9.14–7.14 ma). According to the morphological analysis of the mandibular and dental morphology and the results of the phylogenetic analysis, we assigned the new species tentatively to genus Palaeocavia. The phylogenetic position of the new species suggests an earlier origin for the lineage Palaeocavia + Cavia and for the entire clade Caviinae.     

Vocalizations of chicks and juveniles and the development of adult calls in the Aldabra White-throated rail Dryolimnas cuvieri aldabranus (Aves: Rallidae)

Calls were recorded from eggs, chicks and juveniles of the Aldabra White-throated rail Dryolimnas cuvieri aldabranus. A sonagraphic analysis was made of these calls, their behavioural contexts described and probable functions suggested. Three calls, the twitter, tiuu and contented peep were produced by chicks in the egg. All three calls may be derived from the basic peep first recorded some 36 hours before hatching. Shortly after hatching two more calls, the distress call and the alarm call, can be elicited from the rail chicks. Contented peeps and twitters are restricted to the repertoire of young rails. Song was first heard from wild rail chicks at the age of ten days and may develop from the contented peep. Three adult calls, the 'mp yeah, 'mptiuu and 'mpclick appear at the age of three months and six months later the adult vocal repertoire is completed by the appearance of 'mps, toks, purrs and nest-defence squeals. With the exception of the 'mp, all adult calls can be derived from the vocalizations of chicks and juveniles.     

Über Fibrillärstrukturen im Nebennierenmark von Haus und Wildmeerschweinchen (Cavia aperea f. porcellus L. und Cavia aperea tschudii Fitzinger)

Zusammenfassung Im Nebennierenmark von adulten Wildmeerschweinchen (Cavia aperea tschudii) und Hausmeerschweinchen (Cavia aperea f. porcellus) werden bisher unbekannte intrazelluläre Fibrillenstrukturen nachgewiesen. Licht- und elektronenmikroskopische Befunde zeigen, daß in bestimmten Markzellen Filamentbündel in Gruppen auftreten, die durch das Perikaryon bis zur Zellperipherie zu verfolgen sind. Sie fasern in der Nähe des Plasmalemms auf und bilden desmosomenähnliche Kontaktflächen. Die Einzelfilamente sind ca. 70–100 Å dick. Beim Chinchilla konnten im Mark keine Filamentstränge festgestellt werden, beim Haus- und Wildmeerschweinchen kommen sie in unterschiedlicher Häufigkeit vor.

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Intracellular fibrils in the adrenal medulla of domesticated and wild guinea pigs (Cavia aperea f. porcellus L. and Cavia aperea tschudii fitzinger)

Summary By light and electron microscopic observations intracellular fibrils were found in the adrenal medulla of adult wild (Cavia aperea tschudii) and domesticated guinea pigs (Cavia aperea f. porcellus). In certain cells of the adrenal medulla bundles of filaments can be traced from the perinuclear region into the periphery of the cells. Near the plasma membrane they split apart and attach to the desmosome-like regions. The individual filaments are about 70–100 Å in diameter. In adrenal medullary cells of chinchilla no fibrillar strands were observed, in wild and domesticated guinea pigs they occur in different numbers.

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Die Untersuchung wurde mit dankenswerter Hilfe der Deutschen Forschungsgemeinschaft durchgeführt.     

Preliminary observations on squirrel monkey (Saimiri oerstedi) vocalizations in Costa Rica

This study was an initial attempt to analyze quantitatively vocalizations from the Central American squirrel monkey, Saimiri oerstedi. Vocalizations were recorded in the wild at P. N. Corcovado (S. o. oerstedi). and at P. N. Manuel Antonio (S. o. citrinellus). Additional recordings were made from captive individuals of both subspecies. The acoustic structure of analyzed vocalizations resembled most closely the vocal repertoire of South American Saimiri with the “gothic arch” phenotype, in agreement with the prominent gothic arch facial pattern of S. oerstedi. New structural subtypes of the twitter (“dog-tooth twitter”) and the chuck (“bent-mast chuck”) not previously found in an extensive library of South American Saimiri sound spectrograms were documented. Calls used by older infants when socially separated and when approaching an adult male were essentially identical (sharing typical “isolation peep” structural features) but had significantly different duration and peak frequency. Analysis of recordings from an escaped captive female calling outside her compound over a 3-day period indicated the presence of numerous structural intermediates between typical chuck, twitter, and peep calls.     

Vocal repertoire ontogeny of the captive Asian house shrew Suncus murinus suggests that the male courtship call develops from the caravanning call of the young

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.     

Instituting Dark-Colored Cover to Improve Central Space Use Within Guinea Pig Enclosure

Domestic guinea pigs (Cavia aperea f. porcellus) in laboratories have been shown to actively avoid the centers of their cages. This experiment tested a novel, dark-colored “shader” placed over the central portion of a cage. Based on the observed behavior of wild guinea pig species, it was hypothesized that utilization of the central portion of the cage would increase when the shader was present. Eleven male and 11 female albino, 3-week-old Hartley guinea pigs (Crl:HA) experienced the control and treatment conditions in a crossover study design. They spent more time in central cage sections when the shader was present and spent more time in and around the food hopper when the shader was absent (p < .001). Differences between sexes included increased inactivity in males versus females (p < .05) and a difference in time spent in a corner section of the cage (p < .001), likely associated with location in the room. We concluded that the presence of a shader increased utilization of cage space, which appeared to provide a similar increase in space utilization as structural enrichments.