The Herpetological Journal

pp. 173-180
Authors: Leskovar, Christoph & Sinsch, Ulrich

Abstract: The suitability of harmonic direction finding for tracking of dispersing juvenile natterjack (Bufo calamita) and green toads (B. viridis) was evaluated in laboratory and field experiments. In a first step, dipole reflector tags were developed which combined low mass, small size and large detection range. The average mass was 114 mg, wire antenna length 42 mm and detection range usually varied between 2.5 m and 12.5 m –occasionally reaching 26 m – as assessed using a commercial portable scanning device RECCO 5000. In toads that had a snout-vent length of 22-24 mm, the mass of the reflector tag did not exceed 10% of the toad's body mass. Tags were externally attached by glueing to the dried dorsal skin of the toadlet. In a replicated laboratory experiment, almost all tags were shed 36 hr to 48hr after attachment. In 2001, 417 juveniles toads were equipped with reflector tags and their dispersal was studied in a natural habitat (Urmitz, Rhineland-Palatinate, Germany). The recovery rate of reflector tags was similar in B. calamita (35.9%, n=33) and in B. viridis (31.6%, n=103). The maximum distances between release and recovery site were 588 m in B. calamita and 665 m in B. viridis. Results obtained suggest that this new method is better suited for monitoring the migratory activity and habitat use of small terrestrial anurans than passive tagging systems presently in use, such as microtags and passive integrated transponders (PIT). Nevertheless, detection range is still too small to rival active monitoring systems such as radiotransmitters which remain unsuitable for small anurans.

Keywords: BUFO VIRIDIS, PASSIVE TRACKING SYSTEM, POSTMETAMORPHIC DISPERSAL, BUFO CALAMITA