Summary. Plains

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SUMMARYThe caging, feeding and handling in our laboratory of 4 unusual hystricomorph rodents are described. These animals are: the wild guinea-pigs, or cuis (Cavia aperea and Galea musteloides), the degu (Octodon degus), and the plains viscacha (Lagostomus maximus).The species were obtained for investigation of their reproduction and some details of this are given. 83Although the domestic guinea-pig (Cavia porcellus) has been bred in captivity for over 400 years, other members of the rodent sub-order Hystricomorpha have received very little attention.The care and management of 4 laboratory hystricomorph species (chinchilla, agouti, acouchi and African porcupine) were described by Weir (1967). Since 1967 four more species, the wild guinea-pig (Cavia aperea), the cuis (Galea musteloides), the degu (Octodon degus), and the plains viscacha (Lagostomus maximus), have been kept successfully in this Institute.Only the degu has previously been kept under laboratory conditions. This paper describes the methods of husbandry used and the breeding characteristics of the species. All 4 have a vaginal closure membrane which becomes perforate only at oestrus and parturition; in this respect they resemble the guinea-pig and all other hystricomorphs (except the coypu) so far investigated. WILD GUINEA-PIG (Cavia aperea)This cavy (Fig. I), which rarely weighs more than I kg, is widely distributed throughout Argentina, Uruguay and Brazil. Its natural habitat is open grassland, where it nests and makes paths in the taller vegetation, and feeds in the more open areas at dawn and dusk. The present colony was derived from 2 females and I male caught by the author in Entre Rios Province of Argentina in August 1967.

Agoutis (Dasyprocta aguti) were investigated in the laboratory for comparison of their reproductive characteristics with those of other hystricomorphs. A vaginal closure membrane was present and the length of the oestrous cycle averaged 34\m=.\2\ m=+-\ 2\m=.\1 days. The ovaries and reproductive tracts of these animals, together with specimens obtained post mortem were studied and some correlations with physiological condition attempted. The ovary of the agouti is characterized by the presence of large numbers of accessory corpora lutea and by the extensive interstitial tissue which appears to replace completely the stroma of other mammals. Patches of 'immature testis tubules' were found in the ovaries of several animals.shall,

The breeding characteristics of three species of wild guineapig (F. Caviidae) are reported. Cavia aperea, Galea musteloides and Microcavia australis were studied in Argentina in the field and in outdoor pens, and laboratory colonies of the two former species were also established in England. Pens of domestic guinea-pigs (Cavia porcellus) and of C. aperea \m=x\C. porcellus hybrids were maintained in Argentina for comparisons with C. aperea. C. aperea and G. musteloides gave birth in every month but there was a breeding peak in spring (September to December). Microcavia had a more restricted breeding season ; in the field study area, births occurred only between August and April. Gestation length in C. aperea was variable but the mode was at 61 days, while the modes of Galea and Microcavia were much shorter at 53 and 54 days, respectively. All three species exhibited a post-partum oestrus and Galea may experience a lactation anoestrus. Oestrous cycle lengths in C. aperea and Galea varied considerably but the mean length in Cavia was 20\m=.\6\m=+-\0\m=.\8 days and in Galea it was 22\m=.\3\m=+-\1 \ m=. \ 4 days; in the latter species, the presence of a male in the same cage was necessary for the induction of oestrus. Average litter size was 2\m=.\2for C. aperea, 2\m=.\6for Galea and 2\m=.\8for Microcavia. In the Argentine colonies, the age at first conception in C. aperea and Galea varied with the time of year of birth, but this variation was not maintained under the more equable laboratory conditions.