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Quelques données sur la dynamique de population chez Octodon degus (Rongeur Hystricomorphe) du Chili central

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Title: Quelques données sur la dynamique de population chez Octodon degus (Rongeur Hystricomorphe) du Chili central
Author: Le Boulengé, Eric; Fuentes, Eduardo R.
Abstract: This paper reviews data on the population ecology of Octodon degus, an hystricomorph rodent endemic to Chile. It is based upon personal field observations as well as on data from the literature. Field work was carried out on two sites located at « Los Dominicos » , 20 km east from Santiago, using capture-recapture methods. The first site (A) is covered by a moderately dense stand of various trees and shrubs. The second site (B) is more open, with grasslands crossed by a line of Muehlenbeckia hastulata. Grid size was 2400 m2 on site A and 600 m2 on site B. For density estimations an area 25 m wide in site A, and 13 m wide in site B, was added to the trapping areas around the grid, corresponding to the average distance between successive captures of the species in the two habitats. On site A, population density varied from 49 individuals/ha in February to 39 individuals/ha at the end of March and 73 indi viduals/ha in October-November. The lowest densities are pro bably to be found in June- July, at the onset of the reproductive season. On site B, densities ranged from 259 individuals/ha in February to 192 individuals/ha in April. On both sites the monthly disappearance rate was about 40 % during the period from end of the summer to the following spring. Some data are also given on sex-ratio and age-ratio. Octodon degus, a diurnal grass-eater, can withstand neither high temperatures nor high altitude, but appears to be well adapted to life in grasslands. It lives in small social groups within a complex network of tunnels and paths, centered upon a stable burrow system located under a pile of rocks or shrubs. In summer time, when water is scarce, the Octodon supplement their vegeta rian diet with fresh droppings of cattle or horses, or with bark of Acacia caven. Birds of prey apparently exert a strong predation pressure upon the Octodon populations, and some of the morphological, physiological and behavioural characteristics of the species are probably adaptive in this context. Such might be the case for the observation posture and alarm call of the adults, the sharpness of vision for objects located above the animal, and the autotomy of the tail.
Publisher: Société nationale de protection de la nature et d'acclimatation de France, Paris (FRA)
Date: 1978

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