Oecologia (Berl) (1982) 54:55 57 Oecologia , 9 Springer-Verlag 1982 Microhabitat Use by European Rabbits (Oryctolagus cuniculus) in Central Chile: Are Adult and Juvenile Patterns the Same ? Javier A. Simonetti and Eduardo R. Fuentes Instituto de Ciencias Bio16gicas, Pontificia Universidad Cat61ica de Chile, Casiiia 114-D, Santiago, Chile Summary. Rabbits (Oryctolagus cuniculus) have been recently introduced to central Chile; adult rabbits have been previously reported to exhibit a release in their use of microhabitats due to lack of effective predation upon them. This paper shows that kittens and juvenile rabbits do not exhibit the same micro- habitat use pattern as adults, in spite of the very low predation pressure upon them. These results suggest that small rabbits are ecologically comparable to native rodents. Introduction The European rabbit (Oryctotagus c~miculus), native to the Medi- terranean Basin, has been recently introduced to central Chile (Greer 1965). Here, rabbits have been documented to exhibit a release in their spatial use of the Chilean matorral when com- pared with their Spanish counterparts (Jaksi6 etal. 1979a). Whereas in Spain rabbits tend to restrict their foraging activities to the neighborhood of protecting bushes, in the Chilean mator- ral rabbits are more active in the open spaces between shrubs (Jaksi6 et al. 1979a); this behavioral pattern of rabbits in Chile contrasts with that exhibited by native rodents, which are re- stricted to areas beneath or near bushes (Jaksi6 et al. 1979a; J.A. Simonetti and E.R. Fuentes unpublished). In addition, fecal and pellet analyses show that predators in Chile eat very few rabbits compared with either native small mammals, or with similar predators in Spain (Simonetti and Otaiza 1980; Jaksi6 and Soriguer 1981). Thus, in central Chile rabbits behave as if there were no effective predators and hence the observed microhabitat use (Jaksi6 et al. 1979 b; Fuentes and Jaksi6 1980 ; Jaksi6 and Sori- guer 1981). Since Jaksi6 et al. (1979a) worked only with adult animals, the following question is pertinent: do small juvenile rabbits exhibit a similar microhabitat use pattern as adults? In this contribution we report the microhabitat utilization patterns of adult versus juvenile rabbits in the Chilean matorral. ReIative predation levels upon kittens (80 g body weight), juve- nile (530 g) and adult rabbits (1,300 g) are also documented and related to their habitat preferences. Methods We used the same study site as Jaksi6 et al. (1979a), at Los Dominicos (20 Km E of Santiago) and also counted fecal pellets as a measure of relative microhabitat use (see Bartholomew Offprint requests to." J.A. Simonetti 1970). Direct observations has shown that the diameter of fecal pellets is positively correlated with the size, and presumably age, of the animals producing them (r=0.41, P< 0.02). 16 14 o 12 -0 lO e~ _o 8 e- ~6 4 $ .0 2 E = 0 0 10 20 30 40 50 percent distance between shrubs A E E u~ 0~ N r r E 12 10 + 76 56 88 + lio ,o, + 119 102 54 § 11o 159 ; . . . . . do ' ' t6o 20 40 b percent distance between shrubs Fig. 1 a, b. Rabbit feces versus distance from shrubs, a Kittens and juveniles (less than 530 g body weight). Ordinate is number of feces found in 625 cm z rectangles. Distance between shrubs ranges from 6 to 15 m (X=9.8 m). Vertical bars equal two standard errors. N=9 for each sampling point. 50% distance between shrubs is the midpoint between two contiguous shrubs. The animals are slightly larger than large specimens of the native rodent Octodon degus. See text for discus- sion. b Mean size of fecal pellets. Mean _+ two standard errors and sample size for each point are shown. 100% distance between shrubs is the maximal distance between the nearest neighboring shrubs. Notice that larger feces are progressively more flequent at larger distances from the nearest shrub. See text for discussion. 0029-8549/82/0054/0055/$01.00