By Jim White, Associate Director, Land and Biodiversity
Later winter and spring is the time that most amphibians begin to make their way from winter hibernation sites (often called brumation sites for cold-blooded animals) to nearby wetlands to breed. However, under the cover of darkness one kind of salamander usually gets a head-start by breeding in late November and December. In anticipation of this early amphibian activity, Nate Nazdrowicz and I headed to southern Delaware on Thanksgiving eve in search of breeding Eastern Tiger Salamanders. Our mission was to collect life history data on this rare species for the Delaware Natural Heritage Program. As we drove south, we hoped that the relatively small amount of rain that had fallen lately would be enough to begin to fill the vernal pools in which the salamanders breed.
We arrived in Sussex County after dark and were excited to find shallow water in the first pool; however, after thorough searching, we found no sign of salamanders. A little discouraged, we visited a second, much smaller pool and were immediately rewarded with the sight of several egg masses that were laid by female Tiger Salamanders. The clear, gelatinous egg masses each contained up to a hundred eggs. We could tell from the condition of the eggs that they were laid recently, possibly within the last few days. Unfortunately, we couldn’t find any adult salamanders, so after counting the egg masses and measuring water depth and temperature, we headed to another pool.
The third pool, like the first, was relatively large and contained water that was approximately 10 inches deep. Wading into the clear water, it wasn’t long before we saw several adult Tiger Salamanders swimming lazily along the bottom. So as not to disturb possible egg masses, we moved carefully through the pond, capturing the adults with dip nets as we went. After catching 13 males and 3 females we quickly measured each individual (they measure between 7 and 9 inches), took a few photos, and then immediately released them back into the pool.
The fact that we found no egg masses in the third pool led us to believe that the adult salamanders we had seen had very recently entered the pool and had not yet mated. However, we knew that mating and egg-laying would take place soon and the cycle of Tiger Salamander life would continue. In February or March, the eggs will hatch into aquatic larvae, and the larval salamanders will metamorphose into subadults in July or early August, at which time they will crawl out of the pool to live in the surrounding woodlands. We knew that by this time next year, some of the eggs that are being laid here this fall will have developed into adults that may return to this very same pool to breed, and thus continue the cycle.
After leaving the pools that night, the long drive home was made much easier by the fact that we had just successfully witnessed the beginning of the breeding season of one of the rarest animals in Delaware–the Eastern Tiger Salamander.