Spatial ecology of the Iberian lynx and abundance of european rabbit in southwestern Spain

Spatial ecology and diet of Iberian lynx (Lynx pardinus) and the abundance of its main prey, the European rabbit (Oryctolagus cuniculus), were studied in southwestern Spain from December 1992 to December 1996 when a decline in rabbit populations occurred. Our objectives were to relate spatial ecology of lynx to rabbit abundance, water availability, and protection from human disturbance. Rabbits were almost the sole prey of lynx; rabbit remains were present in 99.2% (n = 1,171) of feces analyzed. Rabbit abundance and density in 6 different habitats were estimated by line transect sampling. Rabbits were more abundant in Mediterranean scrubland, closely followed by ash stands. Pastureland and lentiscus in plantations had 4.5 times fewer rabbits, and pine plantations 15-20 times fewer rabbits, than the Mediterranean scrubland. Abundance of rabbits in the Mediterranean scrubland was not spatially uniform, as density for 1994 and 1995 varied from 42-55/ha in the area close to the edge of the marsh (locally called the Vera) to 2-7/ha far from the Vera. Rabbit density was 3.5 times higher during spring than during autumn. A decline in rabbit density occurred in 1996 when numbers were 72-91% lower than the previous years. We mapped warren density in Mediterranean scrubland and pastureland to determine intra-habitat differences in spatial distribution of rabbits. Warren density, entrance density, and mean number of entrances per warren declined significantly with distance from the Vera in the Mediterranean scrubland, following a negative exponential function (adj. r2 ranging between 83 and 97%). However, none of these variables showed any trend in relation to the Vera in the pastureland. The lynx population contained three stable pairs of adults plus young raised each year, some of which remained on the study area as subadults (older than one year). The seasonal number of different lynx in the study area ranged between 7 and 17. Average adult and young/subadult seasonal density was 0.77 (range = 0.72-0.88) and 0.46tex-math>$\text{individuals}/{\rm km}^{2}$ (range = 0.07-1.12), respectively. We estimated home range and daily movements of lynx to determine changes that might be due to sex, season, or changing prey density. On average, total lynx home range size was $7.3\ {\rm km}^{2}$ for young, $9.5\ {\rm km}^{2}$ for adult females, and $18.2\ {\rm km}^{2}$ for adult males. Mean core areas (60% isopleth using the kernel approximation) were on average 15%, 10%, and 34% of total home ranges of young, adult females, and adult males, respectively. Significant differences were found for home range and core area sizes among sex-age classes, but neither season nor year affected home range size or core area size. Daily movements averaged 8.0 km. Daily distance traveled was not affected by sex-age class or season, but was different among years, with lynx traveling shorter distances in 1993 and 1996. Daily home range size averaged $1.46\ {\rm km}^{2}$, and again only varied by year. Lynx daily movements were associated with permanent, artificial water sites. Habitat use by lynx was remarkably constant, with no differences detected among sex-age classes, active or inactive locations, seasons, or years. The habitat most frequently used was Mediterranean scrubland (53% of locations), and both it and ash stands were the only habitats preferred by lynx; pine and eucalyptus plantations were avoided, and marsh, pastureland and lentiscus in plantations were neither preferred or avoided. When lynx were found in the non-preferred habitats, on most occasions (78%) animals were closer than 300 m from the edge of one of the two preferred habitats, whereas on only 4% of occasions were animals further than 1 km. This behavior was particularly accentuated when lynx moved through open habitats. Lynx appeared to respond to high human presence, as they were mainly located inside the National Park (82% of occasions), and when outside the Park they more frequently used the areas that were farther from a tourist village. We used a Geographical Information System (GIS) to estimate average rabbit density and number of rabbits within lynx home ranges. On average, rabbit density within home ranges was 5.6/ha. The habitats that sustained more rabbits were Mediterranean scrubland (74.2% of total number of rabbits within home ranges) and ash stands (32.2% for 6 home ranges where these habitats were available). Rabbit densities within core areas were similar to those found in home ranges. Throughout the study period the lowest rabbit density estimated within home ranges was about 1/ha in autumn 1996. The number of rabbits per lynx ranged between 1,367 in spring 1994 and 73 in autumn 1996. Rabbit density within home ranges, core areas, and the trapping area were not correlated with range size (P's > 0.2). Lynx and rabbits preferred the least human-transformed scrubland habitats; therefore natural habitats must be favored over plantations and pastureland areas. The edges of the preferred habitats were also heavily used by rabbits and consequently by lynx. The vegetation structure of the preferred habitats was characterized by intermediate understory cover (25-35%), low tree cover, and large and frequent grasslands. The rabbit decline observed during the study did not affect lynx spatial behavior or reproduction. Therefore, rabbit densities as low as 1 and 4.6/ha for the times of the lowest and highest rabbit density (i.e., autumn and spring, respectively) were enough to sustain the lynx population. Other factors such as the presence of permanent water sites and relatively low human presence are important components of quality lynx habitat.Peer reviewe