We examined demographics, dispersal, sex-related behaviour, group structure, and genetic similarities of female feral pigs Sus scrofa on the Chaparral Wildlife Management Area in southern Texas from June 1993 to December 1995. Cumulative and seasonal ranges and core areas were calculated for 18 female pigs representing three distinct sounders. Simultaneous pairs of radio locations were used to assess behavioural associations among pigs, and DNA ®ngerprinting was used to determine genetic similarity. Behavioural and spatial associations largely corresponded to genetic relationships. Similarity of behavioural dendrograms to genetic dendrograms indicated that genetic relationships of feral pigs played a role in observed population structure. A single discrepancy between genetic and behavioural dendrograms suggested two animals dispersed to an adjacent sounder. Also, one sounder appeared to have been created by ®ssion from a larger, adjacent sounder. Factors that are important keys in understanding the association between genetics and behaviour of feral pigs include dispersal, climate, habitat quality, population densities, and sex-related behaviour.

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We examined demographics, dispersal, sex-related behaviour, group structure, and genetic similarities of female feral pigs Sus scrofa on the Chaparral Wildlife Management Area in southern Texas from June 1993 to December 1995. Cumulative and seasonal ranges and core areas were calculated for 18 female pigs representing three distinct sounders. Simultaneous pairs of radio locations were used to assess behavioural associations among pigs, and DNA ®ngerprinting was used to determine genetic similarity. Behavioural and spatial associations largely corresponded to genetic relationships. Similarity of behavioural dendrograms to genetic dendrograms indicated that genetic relationships of feral pigs played a role in observed population structure. A single discrepancy between genetic and behavioural dendrograms suggested two animals dispersed to an adjacent sounder. Also, one sounder appeared to have been created by ®ssion from a larger, adjacent sounder. Factors that are important keys in understanding the association between genetics and behaviour of feral pigs include dispersal, climate, habitat quality, population densities, and sex-related behaviour.

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Recent advances in the statistical analysis of microsatellite data permit calculation of sex-specific dispersal rates through sexand age-specific comparisons of genetic variation. This approach, developed for the analysis of data derived from codominant autosomal markers, should be applicable to a sexspecific marker such as mitochondrial DNA. To test this premise, we amplified a 449 bp control region DNA sequence from the mitochondrial genome of the collared peccary (Pecari tajacu), and estimated intra-class correlations among herds sampled from three Texas populations. Analyses on data partitioned by breeding group showed a clear signal of malebiased dispersal; sex-specific fixation indices associated with genetic variation among social groups within populations yielded values for females (F GP ¼ 0.91), which were significantly larger than values for males (F GP ¼ 0.24; P ¼ 0.0015). The same general pattern emerged when the analyses were conducted on age classes (albeit nonsignificantly), as well as categories of individuals that were predicted a posteriori to be dispersers (adult males) and philopatric (adult females and all immatures). By extending a previously published methodology based on biparentally inherited markers to matrilineally inherited haploid data, we calculated sex-specific rates of contemporary dispersal among social groups within populations (m # ¼ 0.37). These results support the idea that mitochondrial DNA haplotype frequency data can be used to estimate sex-specific instantaneous dispersal rates in a social species.

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A fundamental challenge in population ecology is determining the causes of variation in animal abundance. Biological invasions by nonnative species are increasing, especially due to anthropogenic influences. Introduced species alter factors that influence populations, including resource distribution and abundance, predation, and competition. Feral pigs (Sus scrofa), the most widespread exotic ungulate in the world, have had an adverse effect on most ecosystems where they have been introduced. In the United States, the range of feral pigs overlaps with collared peccaries (Tayassu tajacu) in the thornscrub savanna of southern Texas, presenting the possibility of competition between these ecologically similar species. We studied two adjacent peccary populations, one sympatric with feral pigs and one allopatric to pigs, to determine the influence feral pigs have on native collared peccaries. Demography and landscape use of peccaries were compared between treatments. The peccary population on the pig-absent site had 5-8-fold higher densities, larger herd and group sizes, and smaller range and core area sizes than the population on the pig-present site. Reproductive rates and habitat selection did not vary between populations. These differences suggested negative competitive influences of pigs on peccaries. However, differences at the landscape scale, i.e., fragmentation, between treatment areas suggested an alternative, or compounding, factor affecting population variability in collared peccaries.