Easter egg hunt

When I was a child, it was an annual family tradition to participate in an Easter egg hunt in my aunt and uncle's back yard, where dyed eggs were stashed among the landscaping. It's been more than 20 years since my sisters and cousins and I competed for chocolate prizes, and I have rarely rekindled those fond memories, until today when ESF con bio undergrad Tom Maigret and I undertook egg mass surveys among the newly constructed Heiberg pools. I am amazed and ecstatic at what we found.

Before I report our numbers, let me confess that I have maintained a worry about the vulnerability of my dissertation research to the cooperation of animals that we know exist in decent numbers across the landscape, but may be fickle by taking a year off from reproductive activities if the weather is uncooperative (which there were suggestions might be the case with this late and, at times, dry spring), or by entirely ignoring the newly constructed pools, instead preferring their pre-existing oviposition sites. My worry is gone.

Recall that within the pre-existing ponds within the 24-hexagon landscape, 60 wood frog egg masses were observed in both 2009 and 2010. In contrast, 4 spotted salamander egg masses were observed in 2009, and 165 masses in 2010. I have not yet surveyed these pre-existing habitats, but among the 39 constructed pools we counted 131 wood frog and 34 spotted salamander egg masses! There are masses in all hexagons except for the single pool in Hexagon 14, and nine pools lacked egg masses of either species. Wood frog egg masses were observed in 29 pools, and ten pools contained spotted salamander egg masses. Only a single pool contained just spotted salamander egg masses.  As Jim Curatolo told me in a conversation last week, in his experience, wood frogs colonize new pools more quickly than spotted salamanders. This may be due to one or a number of factors, such as their relatively greater vagility, or perhaps their social advantage of vocal communication. A single male wood frog that finds a new pool and commences calling to draw in females may also attract other males in the vicinity. Silent salamanders have no comparable ability to exhibit mob mentality. Also, it is possible that philopatry is more pronounced in spotted salamanders relative to wood frogs. Finally, population trend differences in the two species may see the wood frog population surging, while spotted salamander population is static or declining, or less spotteds are emerging to breed this year after their banner year in 2010.

This begs the question: from where did all these wood frogs come?! Is there indeed a population surge occurring? Or is there a carrying capacity for egg masses according to the size and number of available aquatic habitats? While bigger ponds do have a tendency to have more egg masses, it is unknown how this effect occurs: do density effects in the aquatic habitat actually dictate the number of females that return upon maturing, or do adults exercise choice in avoiding aquatic habitats with many masses when there are other options available that will be less crowded for their offspring? In cases where options do not exist, it is hard to imagine animals foregoing breeding if only crowded conditions are available, either waiting for better, less crowded conditions the next year, or even better, for USC to augment the amount of habitat available!

It will be very interesting to see what is the pattern in the pre-existing pools, which I hope I can survey on Monday....

Jim Arrigoni, SUNY-ESF