Internal structure and patterns of contraction in the geographic range of the Iberian lynx

Abstract

We use reports obtained in a field survey to characterize the internal structure, and to reconstruct the strong contraction in the geographic range of the Iberian lynx Lynx pardinus during a 35-yr period. Lynx were distributed in one large central population surrounded by smaller peripheral ones. Abundance was autocorrelated, attained high values only in a few scattered sites mostly within the central population, and increased from west to east along major mountain chains. Abundance and occupancy were positively related. The strength of range contraction was similar in both large and small populations. We were able to date two peaks of local extinction, which were accompanied by many events of population fragmentation. We also identified five areas where local extinctions aggregated in space. Lynx relative abundance appeared to be site-specific, and the probability of local extinction decreased with increasing abundance. We suggest that sublethal deterministic factors operating with similar intensity all over the range, rather than in progression from a focal point, best explain the observed trajectory of contraction. Two factors that meet such characteristics may have had an outstanding role in lynx decline. One of them is myxomatosis, an introduced viral disease that decimated rabbits Oryctolagus cuniculus, the staple prey of the lynx. The other is related to the changes in land use prompted by extensive human emigration from the countryside 40 yr ago. Other stochastic or superimposed deterministic factors may have accounted for regional aggregation of local extinctions. The identification of these factors is very important to reverse the lasting decline of this endangered felid.