Temporal Patterns of Mating Activity in Alpine Newts, Ichthyosaura alpestris

Abstract

Many amphibians in temperate zones need to time their reproduction in spring carefully, as they need to find a partner, mate, and oviposit in good time to ensure that their offspring metamorphose before the terrestrial phase starts. Therefore, embracing as many mating opportunities as possible, especially early in the mating period, would be advantageous. Here we examine the temporal pattern of mating activity in Alpine Newts, Ichthyosaura alpestris. Males exhibit a highly complex courtship ritual, during which both olfactory and visual signals play a prominent role. The aim of this ritual is a close coordination between the movements of the male and the courted female, a prerequisite for successful spermatophore transfer. We observed mating activity in a large, group aquarium with a natural photoperiod. We recorded the number of mating pairs at every full hour over the course of 4 d, during light and dark conditions. We observed most courtship behavior during light conditions when males were able to guide females properly with visual cues to the spermatophore. Although greatly reduced, we also found some mating activity in dark conditions on the first experimental day; however, mating activity decreased drastically during the following dark phases. Our findings demonstrate that Alpine Newt males that have access to females over several days use mating opportunities predominantly during light conditions, when visual cues can be utilized optimally. Although olfactory cues might be important during mating, our data suggest that visual cues may confer an adaptive advantage during mate choice. ZUSAMMENFASSUNG.-Viele Amphibien in gemäßigten Klimazonen mü ssen ihre Paarungsaktivitäten im Frü hling zeitlich sorgfältig einteilen, da sie rechtzeitig einen Partner finden, sich verpaaren und Eier legen mü ssen, um sicherzustellen, dass ihre Nachkommen vor Beginn der Landphase die Metamorphose abgeschlossen haben. Aufgrund dessen wäre es vorteilhaft vor allem am Anfang der Paarungszeit so viele Paarungsmö glichkeiten wie mö glich wahrzunehmen. Hier untersuchen wir das zeitliche Muster der Paarungsaktivität von Bergmolchen, Ichthyosaura alpestris. Die Männchen zeigen ein hö chst komplexes Balzritual, bei dem sowohl olfaktorische als auch visuelle Signale eine wichtige Rolle spielen. Der Zweck dieses Rituals ist eine enge Koordination zwischen den Bewegungen des Männchens und des umworbenen Weibchens, was die Voraussetzung fü r einen erfolgreichen Spermatophorentransfer ist. Wir beobachteten die Paarungsaktivität in einem großen Gruppenaquarium, welches naturnahe Bedingungen und eine natü rliche Photoperiode aufwies. Wir dokumentierten die Anzahl der Paare zu jeder vollen Stunde ü ber vier Tage, bei hellen und dunklen Lichtbedingungen. Das meiste Balzverhalten beobachteten wir unter hellen Lichtbedingungen, währenddessen es den Männchen mö glich war, die Weibchen mit visuellen Signalen zur Spermatophore zu fü hren. Obwohl stark reduziert, beobachteten wir auch eine Paarungsaktivitä t unter dunklen Lichtbedingungen am ersten Ve...

A Female Color Ornament Honestly Signals Fecundity

“…Males probably enter the breeding season with a limited number of sperm because spermiogenesis is most likely completed during autumn and spermatozoa are stored until the next breeding season as described for smooth newts, Lissotriton vulgaris (see Verrell et al, 1986). During the mating season in early spring, Alpine newts gather in often crowded ponds, where high mating activity and scramble competition is observable at any time of the day (e.g., Blab and Blab, 1981;Lüdtke and Foerster, 2019). When courting a single female, males may sequentially deposit several spermatophores (Halliday, 1977;Maag, 2013;pers.…”

“…ad libitum three times a week. Before we transferred the females into special oviposition aquaria, we placed males and females together into a large-group aquarium for four days to ensure insemination as described in Lüdtke and Foerster (2019). We randomly divided the newts into three groups with 36 individuals and a 50:50 sex ratio.…”