Breeding Habitat Segregation of Wood Frogs and American Toads: The Role of Interspecific Tadpole Predation and Adult Choice

In western North Carolina, adult wood frogs and American toads often occur syntopically but segregate with respect to breeding habitat. American toads arrive at breeding ponds 4-10 wk after wood frogs and typically select breeding sites that lack wood frog tadpoles. In an experiment conducted in sem...

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Bibliographic Details
Published in:Copeia 1994-08, Vol.1994 (3), p.691-697
Main Authors: Petranka, James W., Hopey, Mark E., Jennings, Barton T., Baird, Shannon D., Boone, Sarah J.
Format: Article
Language:English
Subjects:
Amphibians
Breeding
Breeding sites
Bufo americanus
Eggs
Freshwater
Frogs
Ponds
Predation
Predators
Rana sylvatica
Tadpoles
Toads
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Summary:In western North Carolina, adult wood frogs and American toads often occur syntopically but segregate with respect to breeding habitat. American toads arrive at breeding ponds 4-10 wk after wood frogs and typically select breeding sites that lack wood frog tadpoles. In an experiment conducted in seminatural ponds, adult toads completely avoided ovipositing in ponds with wood frog tadpoles. Additional experiments strongly suggest that predation of wood frog tadpoles on toad eggs and larvae is the primary reason for the evolution of adult avoidance behavior in toads. In one set of experiments, toad eggs and hatchlings suffered complete mortality within two days after being placed in artificial ponds containing natural densities of wood frog tadpoles. Similar mortality occurred when eggs and hatchlings were introduced into natural breeding sites. In one experiment in which 2000 toad hatchlings were added to natural ponds, all were killed and consumed within 45 min by wood frog tadpoles. Although tadpoles of most anurans are considered to be microphagous suspension feeders that occupy lower trophic levels of food chains, a growing body of evidence indicates that many tadpoles can temporarily shift feeding modes to become upper level, macrophagous predators. Because facultative predators such as wood frog tadpoles often reach far higher densities in ponds than do top predators, their role in structuring aquatic communities via opportunistic predation may be more important than previously realized.
ISSN:0045-8511
1938-5110
DOI:10.2307/1447185