Spawning behaviour of Engystomops pustulatus (Anura: Leptodactylidae)

ABSTRACT

Foam nests have evolved independently in several amphibian groups as an adaptive response to prevent predation and desiccation in dry environments. Nests are normally laid on ponds, or in underground galleries, humid forest leaf litter or terrestrial bromeliads. They are built when males or females beat a foam precursor associated with the egg masses extruded by the female. The spawning process requires the synchronic actions of the mating pair to obtain a hemispheric nest that protects the offspring. Herein, we describe the spawning behaviour of Engystomops pustulatus based on videos from 13 nesting couples from the lowlands of western Ecuador. Three variables were measured as indicators of male effort: duration of mixing events, duration of resting periods, and number of kicks per mixing event. We consider that not only male physical effort but also female behaviour influences nest structure. We suggest that nest building requires prolonged and intense physical activity by the male as well as the female’s steady position during spawning and female’s oviposition site selection. Nest building has two phases. In the first phase, the duration of resting periods, the duration of mixing events, and the number of kicks increase and are highly variable. During the second phase the three variables stabilise until the end. The volume of the nest increased mainly during the second phase. In four nesting events we observed kicking movements by the female. To our knowledge, this is the first time that female kicking has been observed in leptodactylid frogs. The function of this behaviour is unknown but our observations suggest that it may be triggered by insufficient male effort. Traditionally, female mate choice in Engystomops has been explained under models of indirect benefits exclusively. We argue that the prolonged male activity during nesting could influence female fitness directly. This will allow the operation of sexual selection via direct benefits.

KEYWORDS:

• Engystomops
• foam nest
• kicking
• mixing events
• spawning

Acknowledgements

Frogs used in this study were collected under permits issued by The Ecuadorian Ministerio de Ambiente, No. 004-IC-FAU-DPF and 006-IC-FAU-DBAP/MA. Nicole Butler, Umar Kombo Sarah Papworth and Tom Pell provided helpful comments in earlier drafts of this manuscript. Special thanks to Adriana Argoti, Pamela Arias, and Isabel Narváez for field assistant and to Paula Peña for taking care of frogs kept in captivity.

Disclosure statement

No potential conflict of interest was reported by the authors.

Supplementary material

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Additional information

Funding

This work was supported by the Dirección General Académica, Pontificia Universidad Católica del Ecuador grant to SR.