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

John G. Palis

Abstract


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.

Keywords


Breeding frequency, breeding season, breeding success, Eastern Spadefoot, Illinois, Scaphiopus holbrookii

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