How about a fluorescent marker?
Would Tetracycline work in hair?
Hilary S_W
.
Hilary Le Q. Stuart-Williams Ph.D.
(Climate, behaviour study and ecology using stable isotopes)
Research Officer - Stable Isotope Laboratory
School of Environmental Sciences, University of East Anglia
Norwich NR4 7TJ, England
Telephone 01603 593837 (Work), 01603 507719 (Fax)
01603 503430 (Home)
More data at : www.uea.ac.uk/~sil/