Breeding Frequency and Success of Eastern Spadefoots, Scaphiopus Holbrookii, in Southern Illinois

  • John G. Palis Palis Environmental Consulting
Keywords: Breeding frequency, breeding season, breeding success, Eastern Spadefoot, Illinois, Scaphiopus holbrookii


The Eastern Spadefoot, Scaphiopus holbrookii, an anuran that ranges widely across eastern North America, exhibits latitudinal variation in breeding activity. In the southern United States, Eastern Spadefoots breed any time of year, whereas further north breeding activity is restricted to the warmer months. In the Midwest, Eastern Spadefoots are described as breeding any time meteorological conditions are favorable between March and September. I examined this commonly held belief at a southern Illinois sinkhole from 1996 to 2012. Eastern Spadefoots bred (oviposited) 26 times, up to three times per year, during 12 of 17 years (70.5%). Breeding occurred from March through July, but most frequently (69.2%) during April and May. Most (92.3%) breeding events occurred during months of above-average precipitation. Recruitment of juveniles followed seven breeding events (in April and May only) in 5 of 17 years and was dependent upon rainfall subsequent to breeding activity. Observations of breeding activity suggest that Eastern Spadefoots in the Midwest breed most often in spring, coincident with favorable meteorological conditions, and that breeding success may be reliant on rainfall subsequent to breeding.
Zoology and Entomology