Abstract
In many socially monogamous species, both sexes seek copulation outside the pair bond in order to increase their reproductive success. In response, males adopt counter-strategies to combat the risk of losing paternity. However, no study so far has tried to experimentally prove the function of behaviour for paternity assurance. Introducing a potential extra-pair partner during the female fertile period provides a standardised method to examine how pair members respond immediately (e.g. increase mate guarding or copulation frequency) or long term (e.g. later parental investment and paternity uncertainty). In this study on a socially monogamous passerine species, we experimentally confronted pairs of reed warblers with a conspecific male (caged male simulating an intruder) during egg-laying. Our results revealed that occurrence of an intruder during that period triggered aggression against the intruder, depending on the presence of the female. The male territory owner also attacked the female partner to drive her away from the intruder. Thus territory defence in reed warblers also serves to protect paternity. The increase in paternity uncertainty did not affect later paternal investment. Paternal investment was also independent of the actual paternity losses. In females, the experiment elicited both, immediate and long-term responses. E.g. female copulation solicitations during the intruder experiment were only observed for females which later turned out to have extra-pair chicks in their nest. In relation to long term response females faced with an intruder invested later less in offspring feeding, and had less extra-pair chicks in their nests. Extra-pair paternity also seems to be affected by female quality (body size). In conclusion female reed warblers seem to seek extra-pair fertilizations but we could demonstrate that males adopt paternity assurance tactics which seems to efficiently help them to reduce paternity uncertainty.
Highlights
In many socially monogamous species, both sexes frequently seek copulations outside the pair bond to increase their reproductive success [1]
Most studies try to detain the partner during the fertile period and have found support for the importance of mate guarding as a paternity guard [30,31,32]
The female may interpret this on one hand as her male partner has deserted or was killed which may induce females to seek for new mates
Summary
In many socially monogamous species, both sexes frequently seek copulations outside the pair bond to increase their reproductive success [1]. In this study we experimentally simulated an increased risk of paternity uncertainty in a passerine bird species namely the reed warbler (Acrocephalus scirpaceus) by confronting a pair with an extra male for two 20minute sessions during the fertile period of the female and to examine their immediate response (e.g. reaction against the intruder and the female mate, or female extra-pair behaviour) and long-term consequences (e.g. adjustment of offspring feeding investment). We want to examine (i) how males and females react when experimentally confronted with an intruder during the female fertile period, (ii) whether this has any consequences on their later parental investment, and (iii) whether it affects paternity uncertainty For this reason each experimental pair was confronted with a conspecific male on two consecutive days for 20 min when egg-laying started (one or two eggs in the nest)
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
