Is a wild mammal kept and reared in captivity still a wild animal?

This study compared domestic guinea pigs (Cavia aperea f. porcellus; DGP) and two different populations of the wild cavy (Cavia aperea), its ancestor, to examine whether rearing of wild mammals in captivity affects their behavior and physiological stress responses. One population of wild cavies consisted of wild-trapped animals and their first laboratory-reared offspring (WGP-1). The animals of the other population were reared in captivity for about 30 generations (WGP-30). The spontaneous behavior of each of six groups of WGP-1 and WGP-30 and nine groups of DGP, each consisting of one adult male and two adult females, was analyzed quantitatively. Blood samples of the males were taken to determine cortisol, epinephrine, and norepinephrine concentrations. In addition, the exploratory behavior of 60-day-old male WGP-1, WGP-30, and DGP was investigated in an exploration apparatus. The domesticated animals displayed significantly less aggression, but significantly more sociopositive and male courtship behavior than their wild ancestors. In addition, DGP were much less attentive to their physical environment. Surprisingly, no behavioral difference was found between WGP-1 and WGP-30. Basal cortisol concentrations did not differ between wild and domestic guinea pigs. Catecholamine concentrations, however, as well as the challenge values of cortisol, were distinctly reduced in the DGP. WGP-1 and WGP-30 did not differ with respect to their endocrine stress responses. In the exploration apparatus both forms of wild cavies were much more explorative than the domestic animals. These data suggest that the long-term breeding and rearing of wild guinea pigs in captivity do not result in significant changes in behavior and hormonal stress responses. It appears to take much longer periods of time and artificial selection by humans to bring about characters of domestication in wild animals.     

Age at maturity in cavies and guinea-pigs (Cavia aperea and Cavia aperea f. porcellus): influence of social factors

Age at maturity, a particularly important parameter in the life history of small mammals, contributes greatly to fitness. Social influences on age at maturity have been demonstrated for altricial rodents, in particular, mice. Nothing is known about such effects in precocial small mammals. Wild cavies Cavia aperea are born in a highly precocial state and mature early in life, briefly after weaning. We investigated whether the wild cavy C. aperea and the domestic guinea-pig Cavia aperea f. porcellus reach maturity earlier in the presence of adults of the opposite sex. Juvenile females kept in pairs without males showed first vaginal opening (=oestrus) when 59 days old in cavies and at about 40 days in the guinea-pig. However, in the company of adult males, cavy females kept in pairs reached maturity when about 30 days old, and guinea-pig females when 26 days old. Most cavy females experienced successful pregnancy following first vaginal opening. In cavies, female mass at birth and at first oestrus was not correlated with age at first oestrus. In guinea-pigs, birth mass predicted age at maturity only when a male was present. The growth rate from birth to first oestrus related to age at first oestrus. In the wild cavy, the presence of a male appeared to influence maturation more between days 25 and 30 than earlier in life. Male C. aperea matured and had fully descended testes when about 65–70 days old. All male cavies produced abundant motile sperm from day 75. First successful copulations occurred at about the same age. Surprisingly, the priming effect of the presence of an adult male on female maturation proved stronger in these highly precocial caviomorphs than in altricial rodents investigated so far.     

Comparative allometric investigations on the skulls of wild cavies (Cavia aperea) versus domesticated guinea pigs (C. aperea f. porcellus) with comments on the domestication of this species

Bivariate allometric calculations were performed to quantitatively compare skulls of wild cavies with domesticated guinea pigs. Descendents of wild caught Cavia aperea from eastern regions of the species’ distribution area were used, as well as unselected domesticated breeds of guinea pigs differing in outer appearance. The individuals of both groups were kept under similar environmental conditions. Altogether 19 parameters on the skulls and the body weights were used for the analyses. These parameters were studied in relation to greatest skull length and to body size. As a general result the diverse parameters are in most cases significantly different between both groups which is interpreted as a special result of unconsciously selected and genetically determined intraspecific changes concomitant with domestication. The skull does not change in total under the domestication process but in a mosaic manner. However, for the mosaic changes of the diverse parameters in relation to skull length a different picture is valid as related to body weight. This is caused by the fact that the skull of guinea pigs is around 5% shorter independent of the body size, a common effect of domestication also described for other species. Thus, skull length is not an appropriate parameter for body size with respect to such intraspecific investigations, although normally used for the characterization of species in interspecific comparisons of museum materials.Altogether in relation to body weight most of the parameters describing the fascial portion of the skull are shorter in the guinea pig, especially the palatine, the diastema and the mandible but also the nasalia and frontalia lengths as well as the breadth of the rostrum and the zygomaticum are smaller. Most of the occipital skull measures are additionally smaller in the guinea pigs. This is clearly the case for the length and the breadth of the braincase and for the tympanic bulla. The braincase volume is 16.2% smaller, a value only slightly different when compared with the degree of brain size decrease due to domestication as reported for this species in other investigations.     

Comparative quantitative investigations on brains of wild cavies (Cavia aperea) and guinea pigs (Cavia aperea f. porcellus). A contribution to size changes of CNS structures due to domestication

Intraspecific allometric calculations of the brain to body size relation revealed distinct differences between 127 (67; 60) ancestral wild cavies and 82 (37; 45) guinea pigs, their domesticated relatives. The dependency of both measures from one another remained the same in both animal groups but the brains of guinea pigs were by 14.22% smaller at any net body weight. Consistent with results in other species the domestication of Cavia aperea is also characterized by a decrease of brain size. Fresh tissue sizes of the five brain parts medulla oblongata, cerebellum, mesencephalon, diencephalon and telencephalon were determined for 6 cavies and 6 guinea pigs by the serial section method. Additionally the sizes of 16 endbrain structures and those of the optic tract, the lateral geniculate body and the cochlear nucleus were measured. Different decrease values resulted for all these structures concomitant with domestication as was calculated from the amount of total brain size decrease and average relative structure values in the wild as well as the domesticated brain. The size decrease of the entire telencephalon (−13.7%) was within the range of the mean overall reduction as similarly was the case for the total neocortex (−10.7%) whereas the total allocortex (−20.9%) clearly was more strongly affected. The size decrease of the olfactory bulb (−41.9%) was extreme and clearly higher than found for the secondary olfactory structures (around −11%). The primary nuclei of other sensory systems (vision, audition) were decreased to less extent (lateral geniculate: −18.1%; cochlear nucleus: −12.6%). Mass decreases of pure white matter parts were nearly twice as high in contrast to associated grey matter parts (neocortex white versus grey matter; tractus opticus versus lateral geniculate body). The relatively great decrease values found for the limbic structures hippocampus (−26.9%) and schizocortex (−25.9%) are especially notable since they are in good conformity with domestication effects in other mammalian species. The findings of this study are discussed with regard to results of similar investigations on wild and domesticated gerbils (Meriones unguiculatus), the encephalization of the wild form, the special and species-specific mode and duration of domestication and in connection with certain behavioral changes as resulted from comparative investigations in ethology, socio-biology, endocrinology and general physiology.     

Ancient and modern steps during the domestication of guinea pigs (Cavia porcellus L.)

To test whether there are differences between living lineages of domestic guinea pigs Cavia porcellus , we studied 118 specimens from six breeds collected along six Andean countries as well as 15 from the wild cavy species ( Cavia tschudii ). The mean weight and body length of 15 adult wild cavies (295±31 g, 242±8.3 mm) were significantly smaller than 25 creole guinea pigs from Bolivia and Chile (639±157 g, 287±23.7 mm, respectively). Eighteen laboratory/pet guinea pigs (including the English Pirbright breed) were also smaller (900±173 g, 308±21 mm) than 25 improved ones from Peru (Tamborada breed, 1241±75.4 g, 317±12 mm) and Ecuador (Auqui breed, 1138±65.5 g, 307±8 mm). Similar size increases appeared in the first axis of a principal component analysis of six skeletal measurements, recovering 84% of total variation. Phylogenetic and haplotype analyses of complete cytochrome b gene sequences consistently joined all 22 domestic individuals (13 shared unambiguous substitutions, 100% bootstrap in 1000 replicates), probably from a single first ancient domestication in the western Andes. Six laboratory/pet sequences were also joined within a common branch (six shared substitutions, 96% bootstrap), probably from a documented European second phase. By contrast, those from improved Auqui joined a northern creole subgroup (one shared substitution, 84% bootstrap), and those from Nativa and improved Tamborada clustered together and with a southern creole subgroup (four shared substitutions, 86% bootstrap); this suggests at least two independent modern events during a more complex third phase, producing two improved guinea pigs selected for size and meat. Cavia tschudii sequences showed some unexpected geographic variation.     

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.     

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.     

A Comparison of Brain Gene Expression Levels in Domesticated and Wild Animals

Domestication has led to similar changes in morphology and behavior in several animal species, raising the question whether similarities between different domestication events also exist at the molecular level. We used mRNA sequencing to analyze genome-wide gene expression patterns in brain frontal cortex in three pairs of domesticated and wild species (dogs and wolves, pigs and wild boars, and domesticated and wild rabbits). We compared the expression differences with those between domesticated guinea pigs and a distant wild relative (Cavia aperea) as well as between two lines of rats selected for tameness or aggression towards humans. There were few gene expression differences between domesticated and wild dogs, pigs, and rabbits (30–75 genes (less than 1%) of expressed genes were differentially expressed), while guinea pigs and C. aperea differed more strongly. Almost no overlap was found between the genes with differential expression in the different domestication events. In addition, joint analyses of all domesticated and wild samples provided only suggestive evidence for the existence of a small group of genes that changed their expression in a similar fashion in different domesticated species. The most extreme of these shared expression changes include up-regulation in domesticates of SOX6 and PROM1, two modulators of brain development. There was almost no overlap between gene expression in domesticated animals and the tame and aggressive rats. However, two of the genes with the strongest expression differences between the rats (DLL3 and DHDH) were located in a genomic region associated with tameness and aggression, suggesting a role in influencing tameness. In summary, the majority of brain gene expression changes in domesticated animals are specific to the given domestication event, suggesting that the causative variants of behavioral domestication traits may likewise be different.     

阿根廷淡水大米草沼泽中野生豚鼠的种群统计和微生境的利用

本文研究了秋冬季节淡水大米草(Spartina densiflora)沼泽中野生豚鼠(Cavia a perea)的丰度、繁殖和微生境利用,以及其对当地植被和棉鼠类(Sigmodontine)啮齿动物的影响。野生豚鼠喜好S.densiflora覆盖度高的生境。繁殖个体(成体)主要利用矮草为主的斑块,幼体则主要利用禾本科植物为主的斑块。结果说明,野生豚鼠微生境的利用受捕食风险和食物种类的影响。在淡水沼泽中,野生豚鼠的丰度、繁殖、体重和微生境利用没有季节性变化,它们对植物的取食和活动跑道的建造对植被结构和同域的啮齿类动物没有负面影响。通过对具有中度季节性变化的淡水生境中的豚鼠种群和具有高度季节变化的草地和路边中的豚鼠种群进行比较,表明野生豚鼠的种群动态以及豚鼠种群对植被和与其共生的啮齿动物群落的影响都受到冬季植被盖度的限制。     

Domestication affects the structure,development and stability of biobehavioural profiles

Domestication is an evolutionary process during which the biobehavioural profile (comprising e.g. social and emotional behaviour, cognitive abilities, as well as hormonal stress responses) is substantially reshaped. Using a comparative approach, and focusing mainly on the domestic and wild guinea pig, an established model system for the study of domestication, we review (a) how wild and domestic animals of the same species differ in behaviour, emotion, cognition, and hormonal stress responses, (b) during which phases of life differences in biobehavioural profiles emerge and (c) whether or not animal personalities exist in both the wild and domestic form. Concerning (a), typical changes with domestication include increased courtship, sociopositive and maternal behaviours as well as decreased aggression and attentive behaviour. In addition, domestic animals display more anxiety-like and less risk-taking and exploratory behaviour than the wild form and they show distinctly lower endocrine stress responsiveness. There are no indications, however, that domestic animals have diminished cognitive abilities relative to the wild form. The different biobehavioural profiles of the wild and domestic animals can be regarded as adaptations to the different environmental conditions under which they live, i.e., the natural habitat and artificial man-made housing conditions, respectively. Concerning (b), the comparison of infantile, adolescent and adult wild and domestic guinea pigs shows that the typical biobehavioural profile of the domestic form is already present during early phases of life, that is, during early adolescence and weaning. Thus, differences between the domestic and the wild form can be attributed to genetic alterations resulting from artificial selection, and likely to environmental influences during the pre- and perinatal phase. Interestingly, the frequency of play behaviour does not differ between the domestic and wild form early in life, but is significantly higher in domesticated guinea pigs at later ages. Concerning (c), there is some evidence that personalities occur in both wild and domestic animals. However, there may be differences in which behavioural domains – social and sexual behaviour, emotionality, stress-responsiveness – are consistent over time. These differences are probably due to changing selection pressures during domestication.     

Immunological relationships of an endogenous guinea pig retrovirus with prototype mammalian type B and type D retroviruses.

A retrovirus endogenous to guinea pig cells was earlier shown to be morphologically similar to type B and type D prototype retroviruses. Molecular hybridization techniques were used to show that guinea pig virus nucleotide sequences are endogenous to both domestic (Cavia porcellus) and indigenous (Cavia aperea) guinea pigs, but cannot be detected in the DNA of either other hystricomorph rodents or other mammals tested. Using radioimmunological techniques designed to detect interspecies relationships, the major internal polypeptide of guinea pig virus (p26) was shown to share three different sets of interspecies antigenic determinants with squirrel monkey retrovirus, viper retrovirus, and mouse mammary tumor virus. Thus, guinea pig virus appears to provide an evolutionary link between type B and D retroviruses.     

Arthropod and helminth parasites of the wild guinea pig,Cavia aperea,from the Andes and the cordillera in Peru,South America

As part of an ongoing research project concerning the diversity and distribution of parasites of Caviidae in South America, 143 wild guinea pigs (Cavia aperea) were collected from 3 localities in the Andean Highlands of Peru. Samples were collected between November 1996 and May 1999 and included representatives of arthropods, nematodes, and trematodes. Seven species of arthropods: Leptopsylla segnis (27.3%), Tiamastus cavicola (6.9%), Gliricola porcelli (55.2%), Hoplopleura alata (6.9%), Polyplax spinulosa (12.6%), Myobia musculi (1.4%), and Eutrombicula bryanti (49.6%); 4 species of nematodes: Capillaria hepatica (6.9%), Graphidioides mazzai (18.8%), Trichuris gracilis (3.5%), and Paraspirudera uncinata (37%); and a single trematode, Fasciola hepatica (4.2%), were identified.     

Animal Housing and Welfare: Effects of Housing Conditions on Body Weight and Cortisol in a Medium-Sized Rodent (Cavia aperea)

Rodents are the most abundant experimental nonhuman animals and are commonly studied under standard laboratory housing conditions. As housing conditions affect animals' physiology and behavior, this study investigated the effects of indoor and outdoor housing conditions on body weight and cortisol level of wild cavies, Cavia aperea. The changing housing condition strongly influenced both parameters, which are commonly used as indicators for animal welfare. The transfer from outdoor to indoor enclosures resulted in a body-weight loss of about 8%. In contrast, animals kept indoors showed a substantial weight gain of about 12% when they were transferred outdoors. These effects were reversible. To substantiate a connection between body-weight changes and the health states of the animals, blood basal cortisol concentrations were measured. Animals kept outdoors had significantly lower cortisol levels than did animals kept indoors. These results imply that indoor conditions have a direct effect on the animals' states. The physiological and metabolic consequences as well as potential welfare aspects should be taken into account when planning experimental work, especially on nondomestic animals.     

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.     

Chromosome studies in some members of the family Caviidae (Mammalia: Rodentia)

A study of the chromosomes of Cavia aperea and Galea musteloides has been made following the introduction into captivity of these two cavies from Argentina. The evolutionary relationships of the two genera have been considered, and the possible ancestry of C. porcellus from C. aperea was investigated in hybrids of the two species.     

A First Generation Comparative Chromosome Map between Guinea Pig (Cavia porcellus) and Humans

The domesticated guinea pig, Cavia porcellus (Hystricomorpha, Rodentia), is an important laboratory species and a model for a number of human diseases. Nevertheless, genomic tools for this species are lacking; even its karyotype is poorly characterized. The guinea pig belongs to Hystricomorpha, a widespread and important group of rodents; so far the chromosomes of guinea pigs have not been compared with that of other hystricomorph species or with any other mammals. We generated full sets of chromosome-specific painting probes for the guinea pig by flow sorting and microdissection, and for the first time, mapped the chromosomal homologies between guinea pig and human by reciprocal chromosome painting. Our data demonstrate that the guinea pig karyotype has undergone extensive rearrangements: 78 synteny-conserved human autosomal segments were delimited in the guinea pig genome. The high rate of genome evolution in the guinea pig may explain why the HSA7/16 and HSA16/19 associations presumed ancestral for eutherians and the three syntenic associations (HSA1/10, 3/19, and 9/11) considered ancestral for rodents were not found in C. porcellus. The comparative chromosome map presented here is a starting point for further development of physical and genetic maps of the guinea pig as well as an aid for genome assembly assignment to specific chromosomes. Furthermore, the comparative mapping will allow a transfer of gene map data from other species. The probes developed here provide a genomic toolkit, which will make the guinea pig a key species to unravel the evolutionary biology of the Hystricomorph rodents.     

Body Weight and Rearing Conditions of Males, Female Choice and Paternities in a Small Mammal, Cavia aperea

Patterns of mate choice may be important determinants of a species' social organisation and mating system. At least two different aspects of female mate choice can be distinguished: choice of a social partner and choice of the genetic father of the offspring. Different characteristics of males can qualify them for these two roles. Although social and reproductive partners have been shown to differ in many species, social association times are often used in laboratory choice tests to infer reproductive preferences. The traits for which females may choose partners are diverse. Body size can correlate with the male's strength in defending resources or other abilities benefiting the female and her offspring. In species living in social groups, social skills learned from group members during infancy can be important for later reproductive success. In this laboratory study, we conducted choice tests with wild cavies, Cavia aperea , a harem-living species of South American rodents, to determine social preferences of females towards two simultaneously available males. For offspring sired during these tests, paternities were determined by microsatellite DNA profiling. Males used in the tests differed in body weight and in rearing conditions: Half of the males had been reared in the presence or absence of their father, respectively. Male rearing conditions had no effect on either female social preferences or paternities. Females significantly preferred heavier males as social partners. In five of six tests, the heavier male also sired the offspring. Sires were in most cases but not consistently socially preferred. Heavier males may be preferable as social partners because they are better able to provide females with resources or have more experience in paternal care or predator avoidance as weight correlates with age. When choosing reproductive partners, females may prefer other male traits and the distribution of paternities may also be influenced by sperm competition.     

Microbes associated with the epithelium of the oesophagus and stomach of guinea pigs (Cavia porcellus)

Histological examination of oesophagus and stomach specimens from 28 guinea pigs (Cavia porcellus) revealed microbes associated with the epithelial surface of these organs. Layers of Gram-positive cocci were associated with oesophageal tissue in all the animals. Yeasts (Torulop-sid pintolopesii) were associated with stomach tissue in most animals 1 week of age or older.     

Urethral catheterization in the female guinea pig (Cavia porcellus)

Urethral catheterization of the female guinea pig has potential diagnostic, therapeutic and research applications. Urethral catheter placement in the female guinea pig is relatively easy to carry out and has fewer potential complications than does catheter placement in male guinea pigs.