The same entomological criteria used in estimating time of death for humans are applicable for deceased wildlife. Necrophilous insects associated with animal carcasses can provide wildlife law enforcement with valuable information necessary for postmortem interval estimation, and ultimately, to incriminate poachers. The purpose of this research was twofold: to establish species composition, faunal succession patterns, and species and life stage interactions of necrophilous insects associated with three wildlife species; and to identify new methods of evaluating succession patterns using statistical measures.
Twenty-one large vertebrate carcasses were monitored throughout decomposition in a mixed flatwood forest in East Baton Rouge Parish, LA during the spring and fall of 1999, and winter of 2000. Each seasonal experiment included one Louisiana black bear (a threatened species), two white-tailed deer, two American alligators, and two swine (experimental standard). Fresh carcasses were sampled simultaneously for necrophilous arthropods manually and by pitfall traps. Manual sampling contributed qualitative observational data regarding decomposition patterns and species interactions not easily revealed using pitfall traps alone and represented typical entomological collections recovered during criminal investigations.
Principle component analysis reduced the complete pitfall trap dataset (451,036 specimens representing 438 taxa) to a statistically manageable size, and regression analysis (Proc Mixed, SAS Institute) determined that season, animal type, and stage of decomposition were significant for species composition. Three discriminant analyses determined which taxa were most discriminating for animal type: Proc StepDisc identified 50 taxa, Proc Discrim determined that these taxa were more discriminating for alligator, and Proc CanDisc identified species assemblages per animal type and illustrated that alligator and bear were more unique than deer and swine carrion. Canonical correlation analysis (Proc CanCorr) tested daily time trends in arthropod activity in relation to days of decomposition.
Two diversity tests were conducted for these data, Shannonís diversity index and Pielouís J test of species evenness. Season was significant for both species diversity and evenness, while stage of decomposition was significant for only Pielouís J, and animal type was never significant. Results from this project further our understanding of the carrion habitat and provide baseline data to wildlife law enforcement agencies for prosecuting poachers.