Identifying individual possums using their oral bacteria

Abstract

The New Zealand Brushtail possum, Trichosurus vulpecula, poses a threat to native forest and fauna. Furthermore, possums constitute both reservoir and vector for bovine tuberculosis. To better monitor possum ecology, new ways of population monitoring and management are required. Objectives: The aims of this study were (i) to determine whether possums can be individually identified by the bacteria they leave when biting Waxtags™; and (ii) to determine how long after biting can bacteria be recovered from Waxtags™. Methods: Eight possums from two locations were sampled by swabbing the central incisors and culturing the bacteria on Mitis-Salivarius agar (selective for streptococci). DNA was isolated from individual bacterial colonies and amplified by arbitrarily-primed polymerase chain reaction with OP A-2 as primer. The amplicons were separated by agarose electrophoresis and compared. Following biting by a human, plain and sugar-coated Waxtags™ were tied to trees (outside) and sampled at three, five and seven day intervals. Streptococci were cultured and the number of colonies compared. Results: Of the eight possums sampled, only two (one from each geographical location) had distinct dominant amplicon profiles. Three possums from each location shared dominant amplicon profiles. Possums from the same location possessed similar amplicon profiles but there were no similarities between possums from different locations. Streptococci were recovered from sugar-coated Waxtags™ after seven days, but from plain Waxtags™ streptococci could not be recovered after three days. Conclusions: Possums from the same geographical region harbor streptococci with indistinguishable DNA profiles and therefore cannot be identified by this method. However, possums from different locations have distinct streptococcal DNA profiles and this may aid in identifying animals from separate ranges. Sugar-covered Waxtags ™ offer an opportunity to monitor possum activities over extended periods and could provide a more cost effective method of population monitoring.