Not yet. We plan to implement downloadable updates in one of the future releases. Previous customers of the CD-ROM will get a discount or one free update (the procedure is not clear yet). The current version on the CD-ROM can be updated already though, but such updates will probably require a complete version of the database (because we add so much new data to each new release). Keep an eye on this page or the CD-ROM page for future developments.
A similar database exists for amphibians, namely Darrel Frost's Amphibian species of the World. However, he doesn't produce a CD-ROM yet.