| The initial juvenile movement phase represents the first stage of the multi-phase process of natal or juvenile dispersal and is particularly crucial as individuals encounter novel habitats and are highly vulnerable to mortality. For many amphibian species, juveniles represent the primary dispersal stage and therefore have a disproportionate influence on population dynamics and persistence. My objective was to investigate how alterations in forest habitat quality impact initial juvenile movement success and behavior. To this end, I conducted a mark-recapture study of juvenile Spotted Salamanders (Ambystoma maculatum) and Green Frogs (Lithobates clamitans) emerging from natal ponds within experimental forest arrays. Each array contained four treatment quadrants (2.11 ha each) containing a control, partial cut, burned clearcut, or unburned clearcut. I determined movement success and identified individual behaviors by analyzing the proportion of juvenile recaptured at drift fences located at 0 m, 20 m, and 50 m from the natal pond, in each quadrant.;The partial cut accounted for over half (53%) of the total Spotted Salamander recaptures in 2008, followed by the control and burned clearcut (20% each), and the unburned clearcut with the fewest (7%). Green Frogs also showed a significant effect of forest treatment, with 54% of recaptures occurring in the control followed by the partial cut (35%), burned clearcut (7%), and unburned clearcut (4%). While we recaptured significantly more Spotted Salamanders at 20 m than 50 m, there was no distance effect with Green Frogs. A significantly greater proportion of both Spotted Salamander and Green Frog juveniles initially moving through open-canopy habitats switched to forests. Nearly all recaptured salamanders originally released into partial cuts were recaptured there (97% treatment fidelity) and only 3% switched to other habitats, whereas in unburned clearcuts 61% switched habitats. Green Frog juveniles showed 96% and 68% fidelity to the control and partial cut, respectively. In clearcut treatments, 74% and 87% of Green Frogs switched to forest treatments from the burned and unburned treatments, respectively.;I next sought to identify how fine-scale habitat quality affected juveniles' decisions to cease moving away from their natal pond, select a refuge, and settle. By using experimental enclosures, I attempted to isolate the effects of forest canopy and microhabitat manipulations on salamander settling decisions relative to unmanipulated forest controls. I employed generalized linear mixed models to examine the effects of canopy cover (closed or open), microhabitat (control, compacted soils, high coarse woody debris, high burrow density), temperature (weekly mean °C), weekly total rainfall amount (cm), and body size (mass; g) on the probability of settling. The analyses for both species revealed strong effects of habitat quality on this key decision. Specifically, in the open canopy control, A. maculatum and A. annulatum had 10% and 30% decreased probability of settling, respectively, compared to the closed canopy control. Ambystoma annulatum were 24% less likely to settle in compacted soil. The responses to the increased refuge density appear to be species-specific. While microhabitat quality did not impact the settling probability of A. annulatum, for A. maculatum, the probability of settling increased 18% and 25%, respectively, under conditions of high burrow density and high coarse woody debris.;This study provides empirical evidence that initial juvenile movement is affected by habitat quality. By releasing thousands of individually marked juveniles, I was also able to record previously undescribed behaviors. This study increases our understanding of individual-level movement responses and provides valuable insights for better predicting patterns of movement at larger scales. |
