Movement Patterns of Adult and Juvenile Rana sylvatica (LeConte) and Ambystoma maculatum (Shaw) in Three Restored Seasonal Pools in Maine

نویسندگان

  • DANIEL VASCONCELOS
  • ARAM J. K. CALHOUN
چکیده

—Research on amphibian movement patterns can aid in strengthening amphibian conservation strategies. Yet for many species, there remain substantial gaps in our knowledge of such movement patterns. From 1999–2002, we documented movement patterns to and from breeding pools of both adult and juvenile Rana sylvatica LeConte (Wood Frog) and Ambystoma maculatum Shaw (Spotted Salamander) by using drift fence arrays at three restored vernal pools in Maine to lend insight into conservation strategies for these two species. Adults and juveniles of both species exhibited nonrandom movement at breeding pools directed preferentially from and toward closed-canopy forested habitat. Marked male, female, and juvenile R. sylvatica were recaptured at 30 m, 150 m, and 300 m from the pool in the surrounding terrestrial environment. Most terrestrial recaptures occurred within the forested wetland habitat to the north of the pool. Median snout–vent lengths (SVL) of recaptured juvenile R. sylvatica were progressively larger at greater distances from the pool. Number of juveniles emerging from the pool was positively correlated with number of juveniles recaptured two days later at 30 m, four days later at 150 m, and six days later at 300 m. Male R. sylvatica were 98% faithful to their breeding pools from 2001–2002, whereas female R. sylvatica were 88% faithful. Male and female A. maculatum were 100% faithful to their breeding pools during the same period. Both species’ (adult and juvenile) nonrandom movement toward forest upon leaving breeding pools suggests that quality of adjacent terrestrial habitat is relevant to both juvenile and adult pool-breeding amphibians. High levels of pool fidelity observed in these two species emphasize the importance of conserving vernal pools and mitigating for poollosses on-site if the nonbreeding habitat is still available. Correlations between amphibian migrations and weather variables varied between years and species, suggesting emigration, immigration, and dispersal may be associated other environmental variables in conjunction with temperature and precipitation. However, heightened activity of both species (adults and juveniles) in response to temperature and precipitation can inform the timing of monitoring efforts and conservation strategies aimed at protecting migration routes. Research on amphibian movement patterns, includingorientationduringmigration, terrestrial travel distances, breeding pool fidelity, and migratory response to weather variables, can aid in strengthening amphibian conservation strategies in several ways. Recent research has shown that conserving landscapes with small, isolated wetlands is necessary for maintaining poolbreeding amphibian populations (Gibbs, 1993, 2000; Semlitsch and Bodie, 1998). Empirical evidence is emerging on importance of quality of terrestrial habitats adjacent to breeding pools (Semlitch, 2002; Regosin et al., 2003a, Calhoun et al., in press). Documentation of amphibian terrestrial movement to and from breeding pools provides information on the quality and extent of terrestrial habitat used by different species of pool-breeding amphibians. Last, breeding amphibians are potentially easiest to monitor and most vulnerable to vehicular traffic during peak migration events. Studies of effects of weather cues on amphibiansmay help predict peak events whenmonitoring and conservation efforts would be most effective. Rana sylvatica and Ambystoma maculatum have been the focus of a number of amphibian movement studies. For R. sylvatica, studies have examined orientation of dispersing juveniles (deMaynadier and Hunter, 1999), terrestrial travel distances of adults (Bellis, 1965), and juveniles (Berven and Grudzien, 1990), breeding pool fidelity (Berven and Grudzien, 1990), wintering habitat (Regosin et al., 2003a), and response to weather variables during the nonbreeding season (Heatwole, 1961; Bellis, 1962, 1965). Studies on A. maculatum have examined orientation of adults at breeding pools (Shoop, 1965; Douglas and Monroe, 1981; Kleeberger and Werner, 1983; Stenhouse, 1985; Phillips and 2 Present address: 22 Meadowlark Drive #2, Ithaca, New York 14850, USA; E-mail: danv@alumni. umass.edu Journal of Herpetology, Vol. 38, No. 4, pp. 551–561, 2004 Copyright 2004 Society for the Study of Amphibians and Reptiles

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تاریخ انتشار 2005