Use of Olfactory Cues by Newly Metamorphosed Wood Frogs (Lithobates sylvaticus) during Emigration Viorel D. Popescu 1,2 , Bekka S. Brodie 3 , Malcolm L. Hunter 1 , and Joseph D. Zydlewski 4 Juvenile amphibians are capable of long-distance upland movements, yet cues used for orientation during upland movements are poorly understood. We used newly metamorphosed Wood Frogs (Lithobates sylvaticus) to investigate: (1) the existence of innate (i.e., inherited) directionality, and (2) the use of olfactory cues, specifically forested wetland and natal pond cues during emigration. In a circular arena experiment, animals with assumed innate directionality did not orient in the expected direction (suggested by previous studies) when deprived of visual and olfactory cues. This suggests that juvenile Wood Frogs most likely rely on proximate cues for orientation. Animals reared in semi-natural conditions (1500 l cattle tanks) showed a strong avoidance of forested wetland cues in two different experimental settings, although they had not been previously exposed to such cues. This finding is contrary to known habitat use by adult Wood Frogs during summer. Juvenile Wood Frogs were indifferent to the chemical signature of natal pond (cattle tank) water. Our findings suggest that management strategies for forest amphibians should consider key habitat features that potentially influence the orientation of juveniles during emigration movements, as well as adult behavior. U NDERSTANDING the movements of migrants and dispersers and identifying habitats selected during the movements to and from breeding ponds is critical for identifying conservation strategies for pond- breeding amphibians (Semlitsch, 2008). Orientation and navigation play important roles in guiding amphibian movements in both the aquatic and terrestrial environments (Sinsch, 2006). Amphibians rely on a multisensory orienta- tion system (Ferguson, 1971) that uses a wide variety of mechanisms, including path integration, beaconing, pilot- age, compass orientation, and true navigation (Sinsch, 2006). Orientation during the transition between the aquatic and terrestrial stages (i.e., immediately post-meta- morphosis) raises particularly interesting questions because of the change in locomotion, the availability of cues, as well as the potential carryover of sources of information between the larval and juvenile life stages (Hepper and Waldman, 1992). For example, orientation information acquired during the larval stage was found to influence American Bullfrog (Lithobates catesbeianus) movements during the onset of emigration in the terrestrial environment (Good- year and Altig, 1971). Migratory movements of adult amphibians toward breed- ing ponds and overwintering sites are well understood and have been shown to rely on a multitude of cues that are used in a hierarchical manner depending on the relative availability of cues (Dall’antonia and Sinsch, 2001). Olfac- tion plays an important part in adult orientation, with odors being used as directional cues for both short-distance orientation toward mates and long-distance homeward orientation (Tracy and Dole, 1969; McGregor and Teska, 1989). Adult breeding migrations were found to be guided by the chemical signature of the breeding ponds in both anurans (Forester and Wisnieski, 1991; Sanuy and Joly, 2009) and urodeles (Hershey and Forester, 1980; Joly and Miaud, 1993). In contrast to the adult life stage, juvenile movements and orientation remain largely unstudied, despite their long- distance emigration and dispersal abilities (Cushman, 2006). Migrating juveniles are hypothesized to have a narrow perception range and consequently rely on proximate cues for orientation in the upland habitat (Rothermel and Semlitsch, 2002; Rothermel, 2004; Popescu and Hunter, 2011). Because natal experience is linked to habitat selection at later life stages (Davis and Stamps, 2004), the ability to recognize the chemical signature of the natal pond is thought to play a prominent role for juvenile orientation during emigration movements (Hepper and Waldman, 1992). The behavioral responses to natal pond odors are species-specific (i.e., reflect the species’ affinity to aquatic or terrestrial environments), change during ontogeny, and exhibit high individual variability (Shakhparonov and Ogurtsov, 2003; Arhipova et al., 2005). The imprinting of specific odors in anurans can occur during the embryonic stage, as well as during two distinct stages of larval development (Gosner 19–21 and 31–41), and the discrimi- nation between imprinted and novel odors during the aquatic stage is maintained during the early terrestrial stage (Ogurtsov and Bastakov, 2001). Despite the strong evidence for the use of breeding/natal pond odors for orientation, little is known about the use of other olfactory cues during movements in the terrestrial environment. For the juvenile stage of our study organism, the vernal pool-breeding Wood Frog (Lithobates sylvaticus), previous research conducted in Maine, USA found evidence that forested wetlands attracted a substantial segment of the local juvenile cohort, and that directionality during emi- gration movements might be genetically inherited (Vascon- celos and Calhoun, 2004; Patrick et al., 2007). The attraction to forested wetlands has conservation implications because forested wetlands are a scarce resource in some landscapes. Also, anthropogenic changes in land use have the potential Copeia cope-12-03-08.3d 16/6/12 18:50:14 424 Cust # CE-11-062R1 1 Department of Wildlife Ecology, University of Maine, 5755 Nutting Hall, Orono, Maine 04469; E-mail: (VDP) dvpopescu@berkeley.edu; and (MLH) mhunter@maine.edu. Send reprint requests to VDP. 2 Present address: Department of Environmental Science, Policy and Management, University of California, Berkeley, 130 Mulford Hall #3114, Berkeley, California 94720-3114. 3 Department of Biological Sciences, Simon Fraser University, 8888 University Drive, Burnaby, BC V5A 1S6, Canada; E-mail: bbrodie@sfu.ca. 4 U.S. Geological Survey, Maine Cooperative Fish and Wildlife Research Unit, 5755 Nutting Hall, Orono, Maine 04469; E-mail: jzydlewski@usgs.gov. Submitted: 4 May 2011. Accepted: 28 February 2012. Associate Editor: J. D. Litzgus. F 2012 by the American Society of Ichthyologists and Herpetologists DOI: 10.1643/CE-11-062 Copeia 2012, No. 3, 424–431