Tuesday, April 19, 2016

Arlington's Amphibian Resurgence

A male Spring Peeper Treefrog calls from an Arlington pond

     Arlington County, Virginia is very urbanized. Due to loss of wetlands (including vernal pools) and heavy development, half the frog and toad species that used to live in Arlington are now gone. The remaining species are often in small, isolated populations, in only a handful of locations. Frogs and toads are excellent bio-indicators if environmental health. Since they consume plant material when young and then switch to a predatory diet, they can build up toxins in both diets. Since they can also absorb chemicals and pollutants through their skins in all stages of life, they are also very sensitive to changes in the environment. So loss of frogs and toads can point to an unhealthy environment and their declines can serve as a warning about the state of the habitat.
     Conversely, their presence can often be a clue to healthy, clean water and their return perhaps signaling improving conditions. This is why we are happy that the frog and toad populations have been expanding in our Arlington parks. Take for example the current status of American toads, which during our surveys from 2005 to 2008 were found to be restricted to one wild location. We now have them in 6 additional places. Similar successes in expansion of range have happened for our Bulllfrog, Green Frog, and Spring Peeper Treefrog populations.

American Toads calling. 
     In addition to having cleaner water and preserving our wetlands, the control and management of invasive plant species has allowed the habitats to support more insect food. Native plants that have also been making comebacks support more insect prey than the exotic invasive plants (and these insects then feed so many more animals such as most of our bird and all our bat species).
     Some of our frogs needed a bit more help in getting established. Such was the case for our Wood Frogs which are dependent on mostly fish-free vernal ponds and mature woodlands. For the longest time Arlington only had two places where they bred. In time, the population from Long Branch Nature Center eventually made it into Glencarlyn Park on its own. But since these frogs need mature woods and vernal ponds that may not be close to one another, we assisted in establishing new populations.
     Now these efforts have to be carefully considered. First of all you need the right habitat with established woodlands and fish free vernal pools. They need to have enough invertebrate prey to sustain them. We felt we had a couple of locations where we had controlled invasives, had mature forest, and could provide the wetlands they needed to reproduce. During the last year of service from our Americorps volunteers, they helped us create some vernal pools in one of our Natural Resource Conservation Areas. An Eagle Scout project provided similar service in another park that contained another Natural Resources Conservation Area.
     With these things in place, we decided it was worth the effort to try and establish new colonies of Wood Frogs. But another concern was the potential introduction of two new diseases (Chytrid and Ranavirus) which were affecting amphibian populations. Luckily for us, the pond we used for stock was tested for these diseases. It ended up being part of two studies, mostly through the Smithsonian, and eventually came up as being clean.

Wood Frog egg masses in an Arlington pond

     Now we have more breeding populations of these woodland frogs. We've recently tried to create additional vernal pools, in locations where we hope the existing frogs can expand their range. We've also made efforts or plan on creating more ponds on the opposite side of such existing barriers as creeks and roads that make their migrations to the breeding pools very dangerous. Despite such programs as our "Stop the Stomp" volunteers helping to guide them across roads, we want to provide them with pools closer to locations so they need not make these dangerous journeys. As our habitat for these amphibians improve, they do so for many other animals as well. Hopefully Arlington will continue to make strides in providing habitat for the return of many other animals and plants such as these frogs.
     Here's a short video of one of these successful efforts:


  1. Always enjoy your posts, but especially this one. This is exciting news - glad to see the hard work is making a difference!

  2. Thank you for your blogging and Facebooking. I learn so much from your posts!

  3. Thanks Alonso, this is heartening

  4. Thanks folks for all your kind comments!