Survivorship and the influence of varying spatial environmental factors on Spotted Salamander, Ambystoma maculatum, egg masses in northern Alabama

Background/Question/Methods

In this study we wanted to compare spotted salamander, Ambystoma maculatum, egg survivorship throughout vernal pools in the Cumberland Plateau in northern Alabama.  A total of 24 temporary wetlands were classified to three types based on the amount of canopy cover in the landscape and surrounding the wetlands: open canopy (pools with no canopy trees within 3 meters of the wetland edge), forested (pools surrounded by forests as well as trees within the pool basin), and perimeter canopy (pools in an open area but surrounded by canopy trees).  Vernal pools were surveyed biweekly between December and May from 2008 through 2011. This projected was executed over three field seasons.  During this time we sampled spotted salamander egg masses using two timed visual encounter surveys.  During each visual encounter survey, a gps unit was used to log each transect within the vernal pool.  Each egg mass was identified down to species, tallied, and each egg counted.  Biweekly surveys were executed until no spotted salamander embryos were noted during the surveys.  At least four rounds were completed for each wetland.  A round was completed if the wetland’s entire basin had been sampled.  In addition to spotted salamander egg data, we also took data on the wetland hydroperiod and area.  The following wetland environmental measurements were also taken: soil and water temperature, water pH, dissolved oxygen concentration, and canopy cover.  Landscape variables were calculated using ArcGIS 10 and ERDAS 10 at three buffer distances to represent juvenile and adult salamander migration distances.  The three distances used were 75 meters, 115 meters, and 200 meters.  Multiple linear regression was used to examine the relationship between the spotted salamander egg numbers and densities, pool conditions, and landscape parameters. 

Results/Conclusions

2,168 egg masses were counted over three field seasons.   The most egg masses came from perimeter canopy wetlands, followed by closed and open canopy vernal pools.  Perimeter canopy vernal pools accounted for 43.43% of total egg masses surveyed and monitored.  Egg mass survivorship varied among wetland canopy types.  Wetland hydroperiod and area varied among wetland types, with perimeter wetlands having the longest hydroperiod and largest area followed by open and forest wetlands.