Sunday, March 8, 2009

Frog and Toad Survey

Pretty soon the weather will warm up and frogs and toads will start their mating calls, and I'll get to listen! Um, not in a weird fetish kind of way, but as a volunteer for an annual frog and toad survey through the city of Ann Arbor's Natural Area Preservation.

The word survey always makes me feel like I should be asking the little critters about their TV preferences and views on the global economic situation, but instead I am monitoring their populations in Ann Arbor parks and natural areas. The survey is in its 15th year and the data volunteers collect is used to track populations over time (click for a species richness map).

You sign up for a route, which consists of several sites, where you go to listen at least once a month from March through June, for the types and amounts of frog and toad species calling. Temperatures have to be at least 45 degrees, without extreme wind or rain, or the anurans won't be calling. The survey is done after dark, based solely on sound. (The calls are unique and easily distinguishable, and they give you a CD to listen to ahead of time to familiarize yourself with the calls, but it's a shame I don't also see the cute froggies as well.) Since frogs (many of which are only the size of a thumbnail) have many diurnal predators, they wait to call until night.

Only male frogs call, as they are trying to attract a mate. You don't try to count the exact number of individuals calling, but assign a frequency code to each species you hear: 0=no calls, 1=more than one individual calling, but with no overlap in calls, 2=multiple individuals calling with overlap, or 3=a whole chorus calling so individual voices are not distinguishable.

Wood frogs and spring peepers are the earliest frogs calling in my area, and they both have a kind of "antifreeze" in their blood glucose that keeps them from freezing over winter. The wood frog only calls for maybe one to two weeks, whereas the spring peeper can continue through summer.

The frogs and toads in my area, in order from early to late calling, are:
  • Wood frog (Rana sylvatica)
  • Northern spring peeper (Pseudacris crucifer)
  • Western Chorus Frog (Pseudacris triseriata triseriata)
  • Blanchard's cricket frog (Acris crepitans blanchardi, rare)
  • Northern leopard frog (Rana pipiens)
  • Pickerel frog (Rana palustris)
  • Gray tree frog (Eastern-Hyla versicolor and Cope's-Hyla chrysoscelis)
  • Green frog (Rana clamitans melanota, one of my favorite calls, banjo-like)
  • Bull frog (Rana catesbeiana)
  • Eastern American toad (Bufo americanus, also present in a vernal pond outside my yard)
I'll post updates after each run, and possibly put up sound files of the frogs calling. Ribbit ribbit, as it were.

Thanks also for your well wishes in response to my previous post. I'm happy to say I'm feeling better and more alert now! Zog good! :)


  1. Monica, This is fascinating! I know I wouldn't be able to tell the difference between a toad and a frog croak, let alone the different species. If you are able to post sound files later, that would be so interesting. I just hope you don't run into any law enforcement officials on your frog runs...might be a little hard to explain what you're doing--peeping on the peepers?:)

    Glad you're feeling better; there have been a lot of viruses going around. It's no fun to be sick!

  2. I could do this, sound fascinating. I listen to the peepers each evening. What do they do with the data? Glad you're feeling better.

  3. Monica:Wishing you a speedy recovery from your discomfort!
    I enjoy listening to the call of the frogs..during mating season..I miss having them in my pond..the racoons seem to get them!!
    I was at the Desert Botanical G. and had you on my shoulder..I'll show and tell next week! Feel better..hugs aNNa xo

  4. SPring! this is such a wonderful sign!
    kari & kijsa

  5. Zog, Monica, it sounds like you are from Ork! Nano nano. So glad you are better now. Hyuck, that is great. Anyway, how cool to listen for these frog and toads and ID them. At offspring Semi's yesterday we could hear lots of them. And those were and still are some of my favorite children's books too.

  6. What a lot of frogs and toads you have in your area. We have two ponds for wildlife and our frogs and newts will be out and about soon.

    If you'd like to watch little videos of them they are at the right-hand side of the blog page :)

  7. Monica, Wow! I love the peepers. This project sounds wonderful...I do know that the loss of amphibians are good indicators of bad environmental news! I don't seem to be able to attract frogs and toads to this garden....maybe toads are here and I haven't noticed them. (I've already found my prince charming so ...) have fun and keep warm and dry out there...gail...glad you are feeling better!

  8. Fascinating topic......

    Our frogs and toads are in decline mainly due to habitat loss. People are encouraged to put ponds in their garden if they can.

  9. Love to read about another frog lover. I am trying to do Frog Watch this year as it is so important. I have been listening to a frog call CD in the car..LOL...

  10. I missed your previous post, Monica . . . and am glad you are feeling better. Hope it was one of those annoying things that happen when we are run down at the end of winter and that you will be fine from now on . . . and energised . . . and full of life . . . and spring!

    But your post . . . it's the first time I've ever wished I could take part in a survey. Sitting there listening in the dusk and dark sounds wonderful.

    We don't have frogs round where I live, just crickets and grasshoppers in the summer . . . and they go on and on and on . . . (I wouldn't want to survey them!) but frogs! And the photos of them look charming.


  11. A most interesting post Monica. The survey sounds a most worthwhile project. Glad to hear that you are on the mend.

  12. Monica, can you TELL the difference between all those calls?? I love the Spring Peepers! They're such a sign that Spring has arrived. :-)

  13. Rose,
    Actually, it's quite easy to tell the differences among calls once you've listened to the CD over and over. Plus, some frogs call way earlier int he season than others, so you only have maybe 5 suspects at any given time. I was all worried about it the first year I did it, but it was a lot easier than I thought!

    They use the data to monitor the numbers and locations of frogs over time. In general, populations are declining, but an area abundant in frogs is a good sign indicating large varieties of other animals as well.

    I've been eagerly following your desert photo updates and wish I had been there to meet you!

    Kari & Kijsa,
    Thanks for stopping by. Are your names Finnish?

    Zog stereotypical caveman from Gary Larson not Mork & Mindy but easy mistake! ;-) I turn non-verbal and Zoglike when I'm sick or very tired. And I like not only retro items but also expressions!

    Hi! I'll be right over to your site. There is also a salamander survey, which is done by sight and not calls, but I haven't done that. There are nine species of salamanders in Michigan, though I've only ever seen one (they hide!), and one newt, the eastern newt (Notophthalmus viridescens), which is small and yellowy and very cute; check it out here!

    Yep, abundance of frogs indicates a great natural environment, lack of frogs means something may be wrong with the area. But that's more the case for natural areas, not backyards. A lot of frogs and toads mate in vernal pools, so if you're not near one, you won't hear them.

    The same thing is true here about habitat loss. I get American toads who breed in a vernal pond right behind my house, but I've only rarely seen them in my garden. They must go into the natural area bordering my yard when the pond dries up.

    Yep, I listened to a similar CD in the car for a long time before doing the survey the first time. It was actually EASIER IDing them in real life than it was from the CD because you have directional cues in real life!

    I'll link to more frog photos later in the season, as I report on hearing each kind. Stay tuned! :)

    ~ Monica

  14. Monica,

    We have a special pond about 2 hours from here in the North Carolina Sandhills. The pond is called 17 Frog Pond. It can dry up entirely and has no fish. The reason for the name is during a good night in May one can ID up to 17 species of frogs and toads in one night, pretty amazing. Our best effort in one night has gotten 11 or 12 species. The Barking Tree Frogs are amazing, several hundred can be seen in one night everyone different than the last. been going out there for years hoping to see a Carolina Gopher Frog and Pine Barrens Treefrog, heard both but never saw one.

  15. Hi Monica, I just found your blog, and I love it!