Intraspecific Variation In Home Range Size Research Articles

Variation in diet, prey selectivity and home-range size of Eurasian lynx Lynx lynx in Switzerland

To analyse the factors responsible for the interplay of Eurasian lynx Lynx lynx predation and home-range size, we reviewed patterns of lynx predation in Switzerland by comparing the prey spectrum of lynx in five studies performed in the following study areas: the northwestern Alps, where lynx were studied both in the 1980s and 1990s, the central Alps, the Jura Mountains, and northeastern Switzerland. We then compared home-range size of female lynx with two indirect measures of prey abundance, roe deer Capreolus capreolus and chamois Rupicapra rupicapra harvested per km2 and habitat suitability for roe deer and chamois as derived from a GIS model. Lynx diets were similar among sites. Roe deer and chamois made up 90% of prey items in all five studies. Comparing the proportion of roe deer and chamois in the diet with availability, Manly's preference indices indicated selective predation in all studies. Roe deer were preferred over chamois in all areas except in the Jura Mountains where relatively few chamois were present. Predation was least selective in northeastern Switzerland, where the initial phase of recolonisation by lynx was studied. Variation in prey availability is often identified as an important factor explaining intraspecific variation in home-range size. Due to differences in roe deer and chamois abundance from one study area to another, we expected female lynx home ranges to decrease with increasing prey abundance. The predictors for Minimum Convex Polygon (MCP) and Kernel home-range estimators differed. MCP home-range sizes were best explained by the interactions of study with the number of locations per lynx, roe deer harvested per km2, and good roe deer habitat, whereas Kernel home-range sizes were best explained by the interactions of study with good roe deer habitat, good chamois habitat, and the interaction of good roe deer and chamois habitat plus an additive effect of the study. Contrary to our expectations, there was no simple correlation of prime roe deer and chamois habitat nor between the number of roe deer and chamois harvested per km2 and the size of female lynx home ranges. The comparison of the five studies suggested that this expectation may only be valid if lynx populations are close to carrying capacity (e.g. the Jura Mountains and the northwestern Alps in the 1990s). For predictions of home-range size both habitat (spatial factor) and the status and dynamic of the predator/prey populations (temporal factor) need to be taken into account.

HOME-RANGE AND ACTIVITY PATTERNS OF THE SOUTH AMERICAN SUBTERRANEAN RODENT CTENOMYS TALARUM

Subterranean rodents are characterized by limited individual mobility and patchy distribution of local populations, all of which have been related to the great evolutionary diversification of this group. Because of their secretive habits, radiotracking becomes an essential tool to collect data systematically on characteristics of their space use, rate of movement, and daily patterns of activity. Compared to other subterranean species, the ctenomyids exhibit more activity above the surface. Despite this, a previous study showed that only 25% of the captive individuals analyzed presented rhythmic bouts of activity associated with light‐dark cycles. In our study, we used radiotelemetry to explore quantitatively the home-range dynamics and daily movements of the South American Talas tuco-tuco (Ctenomys talarum). As expected, the home ranges of males were larger than those of females. However, intraspecific variation in home-range size also was observed between 2 different study sites, possibly reflecting differences in body size and soil characteristics between the study sites. Rhythmicity in activity patterns was confirmed to be polymorphic in this species, as previously observed in captivity, and daily activity was mostly concentrated in the diurnal period. We suggest that the present study will contribute to generating important insights into home-range dynamics and daily patterns of activity of free-living subterranean rodents.

Intraspecific Variation in Home-Range Size in Some Anolis Lizards

Intraspecific variation in home-range area is investigated using observations on 896 individuals in four Anolis species distributed over 16 sites in the Bahamas. A. sagrei, a highly terri- torial, polygynous species, typically has smaller home ranges than the three more arboreal species; areas are as small or smaller than recorded for any other lizard. Adult males have larger home ranges than adult females. Adult male home-range area, relative to that of females, in all species but distichus, is over twice as great as expected from relative energetic requirements. Subadult-male ranges are especially variable, possibly indicating variation from a territorial to a wide-ranging, nonterritorial strategy. In sagrei, but not the other species, home-range area increases more strongly with body size in males than females; one female sagrei regression is significantly negative. Regressions of two other species frequently have negative slopes. The rate of increase in home-range area with body size for sagrei males, but not the other species, is similar to the rate for interspecific lizard regressions. Variation about the regression line in most cases is high. Within a sex and site, home-range area is unrelated to relative growth rate or to survival. In the largest sagrei data sets, the number of adult females within an adult male's home range is significantly related to both the male's home-range area and his body size. Home-range area in classes of sagrei is inversely related to density of the same and other classes; in adult females and subadult males the relation is strongest using density of all conspecifics; in adult males it is strongest using adult male density. In two other species, the relation frequently is not inverse, especially in subadults.