Spatial ecology of Iberian lynx and abundance of European rabbits in southwestern Spain

Spatial ecology and diet of Iberian lynx (Lynx paradinus) and the abundance of its main prey, the European rabbit (Oryctolagus cuniculus), were studie d in southwestern Spain from December 1992 to December 1996 when a decline in rabbit populations occurred. Our objectives were to relate spatial ecolo gy of lynx to rabbit abundance, water availability, and protection from hum an disturbance. Rabbits were almost the bole prey of lynx; rabbit remains w ere 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 ha d 4.5 times fewer rabbits, and pine plantations 15-20 times fewer rabbits, than the Mediterranean scrubland. Abundance of rabbits in tile Mediterranea n 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 th e V ra) to 2-7/ha far from the Vera. Rabbit density was 3.5 times higher du ring spring thane during autumn. A decline in rabbit density occurred in 19 96 when numbers were 72-91% lower than the previous years. We mapped warren density in Mediterranean scrubland and pastureland to dete rmine intra-habitat (differences in spatial distribution of rabbits. Warren density, entrance density, and mean number of entrances per warren decline d significantly with distance from the Vera in the Mediterranean scrubland, following a negative exponential function (adj. r(2) ranging between 83 an d 97%). However, none of these variables showed any trend in relation to th e Vera in the pastureland. The lynx population contained three stable pairs of adults plus young raise d each year, some of which remained on the study area as subadults (older t han one year), The seasonal number of different lynx in the study area rang ed between 7 and 17. Average adult and young/subadult seasonal density was 0.77 (range 0.72-0.88) and 0.46 individuals/km(2) (range = 0.07-1.12),respe ctively We estimated home range and daily movements of lynx to determine changes th at might be due to sex, season, or changing prey density. On average, total lynx home range size was 7.3 km(2) for young, 9.5 km(2) for yl adult femal es, and 18.2 km(2) fo adult males. Mean bore areas (60% isopleth using the kernel approximation) were on average 15%, 10%, and 34% of total home range s of young, adult females, and adult males, respectively. Significant diffe rences 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. Da ily movements averaged 8.0 kill. Daily distance traveled was not affected b y sex-age class or season, but was different among years, with lynx traveli ng shorter distances in 1993 and 1996. Daily home range size averaged 1.46 km(2), mid 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 a mong 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 lentis cus 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 in 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 par ticularly accentuated when lynx moved through open habitats. Lynx appeared to respond to high human presence. as they were mainly located inside the N ational Park (82% of occasions), and when outside the Park they more freque ntly 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 d ensity within home ranges was 5.6/ha. The habitats that sustained more rabb its were Mediterranean scrubland (74.2% of total number of rabbits within h ome ranges) and ash stands (32.2% for 6 home ranges where these habitats we re available). Rabbit densities within core areas were similar to those fou nd in home ranges. Throughout the study period the lowest rabbit density es timated within home ranges was about I/ha in autumn 1996. The number of rab bits per Lynx ranged between 1,367 in spring 1994 and 73 in autumn 1996. Ra bbit 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 t herefore natural habitats must be favored over plantations and pastureland areas. The edges of the preferred habitats were also heavily used by rabbit s and consequently by lynx. The vegetation structure of the preferred habit ats was characterized by intermediate understory cover (25-35%), low tree c over, and large and frequent grasslands. The rabbit decline observed during tile 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 h ighest rabbit density (i.e., autumn and spring, respectively) were enough t o sustain tire lynx population. Other factors such as the presence of perma nent water sites and relatively low human presence are important components of quality lynx habitat.