Using seed-tagging methods for assessing post-dispersal seed fate in rodent-dispersed trees

Seed tagging is widely used for tracking seeds during dispersal by seed-caching animals. No studies, however, have fully examined the effects of seed tagging on post-dispersal seed fate. We studied how two seed tagging techniques – thread-marking and wire tin-tagging – affected seed fate by placing tagged and untagged seeds in simulated seed sources and caches and comparing removal rates and fates, and by comparing seedling establishment between tagged and untagged seeds. Tagging had little effect on whether seeds were eaten or dispersed, though both marking methods significantly delayed seed removal by rodents. Both marking methods proved effective for retrieving removed seeds and their fates, but because rodents bit off thread not wire, wire tin-tagging yielded a much higher recovery rate and more accurate estimation of seed fate. We found little difference in dispersal distance between the tagging methods. Piercing of the cotyledons negatively affected seedling emergence in one of two seed species tested. Wire tin tags are a suitable alternative for tracking seeds where seed-caching rodents tend to cut or detach thread marks and yield results comparable to thread-marking. However, both seed tagging methods may underestimate seed dispersal and survival due to delayed removal and damage of the cotyledons by piercing.