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The influence of predator threat on the timing of a life-history switch point: predator-induced hatching in the southern leopard frog (Rana sphenocephala)

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We tested the hypotheses that potential egg predators, crayfish Procambarus nigrocinctus and dytiscid Cybister sp. larvae, would accelerate the timing of hatching and that a larval predator, dragonfly naiad Anax junius, would delay hatching in the southern leopard frog (Rana sphenocephala). We also tested the hypothesis that differences in response would be proportional to predator lethality. Our results indicate that our hypotheses were partially supported. The presence of an efficient egg predator (crayfish) induces hatching faster than a less efficient predator (dytiscid larvae). However, the presence of a larval predator (naiads) did not delay hatching. Eggs that developed in the presence of egg predators produced hatchlings that were shorter (total length) than those reared in the presence of larval predators or those reared in the absence of predators. We suggest that earlier hatching times should decrease vulnerability to egg predators but result in shorter hatchlings.

Nous avons éprouvé les hypothèses selon lesquelles des prédateurs potentiels des oeufs, l'écrevisse Procambarus nigrocinctus et la larve de dytique Cybister sp., font anticiper le moment de l'éclosion chez la grenouille léopard du sud (Rana sphenocephala), et un prédateur des larves, la larve de la libellule Anax junius, retarde l'éclosion. Nous avons aussi vérifié l'hypothèse qui veut que les différences de réaction varient en proportion du caractère létal du prédateur. Nos résultats appuient en partie ces hypothèses. La présence d'un prédateur efficace (écrevisse) suscite l'éclosion plus rapidement que celle d'un prédateur moins efficace (larve de dytique). Cependant, la présence d'un prédateur des larves (larve de libellule) ne retarde pas l'éclosion. Les oeufs qui se développent en présence de prédateurs des oeufs produisent des larves néonates plus courtes (en longueur totale) que ceux élevés en présence de prédateurs des larves ou en l'absence de prédateurs. Nous croyons que les éclosions devancées réduisent la vulnérabilité aux prédateurs des oeufs, mais elles entraînent la production de larves néonates plus courtes.[Traduit par la Rédaction]

Document Type: Research Article

Publication date: September 1, 2003

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  • Published since 1929, this monthly journal reports on primary research contributed by respected international scientists in the broad field of zoology, including behaviour, biochemistry and physiology, developmental biology, ecology, genetics, morphology and ultrastructure, parasitology and pathology, and systematics and evolution. It also invites experts to submit review articles on topics of current interest.
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