H. crucifer Photo by USGS (Public Domain)
Back in April I wrote about my spring observations on our local amphibians. Neither spring peepers (Hyla crucifer) nor wood frogs (Rana sylvatica) were very abundant in Western Pennsylvania this year. Low winter snow fall totals (thanks, El Nino!) led to a very small spring snow melt. When these low melt volumes were coupled with a much lighter than average spring rainfall, the wetlands and vernal pools on which these frogs rely for reproduction became both very reduced in size and also fleetingly transient. Gray tree frogs (Hyla versicolor), though, were out in force at night trilling both in the spring and on through the summer. These tree frogs may be somewhat less picky than peepers or wood frogs in choosing their breeding ponds, and, so, may have been less impacted by the low volume of the seasonal pools.
Photo by D. Sillman
Out at Todd Nature Reserve pond, both bull frogs (Lithobates catesbeianus or Rana catesbeiana) and green frogs (Lithobates clamitans or Rana clamitans ) were very abundant and active this year. Their populations seemed unchanged from previous years. The water level of the Todd pond was high in spite of the dry winter and spring, and these frogs showed little sign of environmental stress.
A sixth amphibian that made a late appearance in our field was the American
Photo by Scrumshus, Wikimedia Commons
toad (Anaxyrus americanus, formerly Bufo americanus). For years, large “bufo” individuals have inhabited our garden and flower beds turning up unexpectedly when we were pulling weeds or digging potatoes. When Deborah and I taught “Kids in College” summer classes at Penn State we could count on going out the night before the class sessions started and turning up a large, mature American toad usually lurking in our front flower bed. The kids really loved watching these toads eat insects in the lab and they were wonderful living foci for so many interesting biological and natural history discussions! American toads can live for up to thirty years, so I like to think that all of our Kids in College years might just have featured a single, very gregarious individual who regularly summered in our front flower bed!
Anyway, early in August an army of small, immature American toads showed up in Izzy’s side yard! They were just a bit smaller than the end of my thumb, and they hopped about furiously (and randomly) whenever Izzy put her nose to the squirming grass! The adult toads must have found the slow, shallow stream down at the bottom of the field (and each other!) and created a bumper crop of tadpoles which developed into little toads. The tiny toadlets are now spreading out from their freshwater nursery and were gobbling up any insects that stumbled into their paths. A very small percentage of them will survive to late fall when they will dig down into the leaf litter and soil to hibernate their way through the winter. They will reach reproductive maturity after two or three years of wandering, eating, and digging and will then find their mating puddle or pond and start the cycle all over again. These truly wonderful toads just need some cover (woods or gardens), insects and other invertebrates to eat and a reliable source of clean water for mating.
Last year we went on a salamander hunt in Harrison Hills Park, but we didn’t find any in spite of the abundance of perfect, amphibian habitats throughout the park. This year was so warm and dry that we didn’t even go out and look.
Photo by D. Sillman
I have occasionally seen salamanders in the persistently wet drain at the bottom of my driveway, but this year due to re-construction of the driveway retaining wall and also our very dry April through July, I saw no salamanders at all until the first day of October! Deborah and I were out moving a few of the rocks we had placed on the landscaping cloth to hold it and its covering pine mulch in place. We lifted up a rock to re-position it when this fellow pictured above wiggled out into view. He was as fine a northern slimy salamander (Plethodon glutinosus) as you could ever expect to see! After he posed for a few pictures he dove back under some of the undisturbed rocks. I hope that he sleeps well this winter and finds a mate so that they can fill up my driveway drain with eggs!
This past May the results of a major U. S. Geological Survey study on global amphibian populations was published in the journal Science Reports. David Miller a Penn State assistant professor of wildlife biology and Staci Amburgy, a Penn State doctoral candidate in ecology were both important participants in this study. Their findings include a very precise estimate of the rate of the world-wide decline in amphibians (populations are shrinking at a rate of 3.79% per year!), and an analysis of the causes of this observed decline (chytrid fungal infections, urbanization and agriculture (causing habitat loss), pesticide pollution, and climate change). The report also noted that the rates of amphibian decline are different in different parts of the world, and that the relative significance of the causal agents of these declines are also different in different places. In the United States, for example, amphibian numbers are declining most rapidly in the Rocky Mountains (primarily due to the effects of pesticides) and on the West Coast(primarily due to the effects of climate change).
There are 7000 known (living) species of amphibians. They have existed on Earth for three hundred million years. They were the first truly terrestrial vertebrates! In the last twenty years, 168 amphibian species have gone extinct and 2469 species have declining population numbers (of these declining species 1856 are under the threat of extinction). In North America there are 440 amphibian species, and 41 of these have either gone extinct or are critically endangered and another 107 are threatened by or vulnerable to extinction.
If we look at the amphibians here in Western Pennsylvania we see in miniature the problems facing amphibian species around the world. Our salamanders have succumbed to the stresses of habitat destruction and, possibly, acid rain. Our spring peepers and wood frogs have declined because of habitat destruction (especially the human generated landscape erasure of their vital vernal pools). Our great generalists (the American toads) and large pond dwellers (bullfrogs and green frogs) are hanging in there, but I am sure are in some decline because of habitat degradation and water pollution.
The Spring sounds empty without the choruses of the peepers, and woods seem less alive without the thrashing and “quacking” of the wood frogs. Everyone needs to do more to help these species survive!