Sneaking versus fighting: Alternative reproductive tactics in the New Zealand giraffe weevil (Lasiorhynchus barbicornis)

Christina Painting *1, Thomas Buckley 2, Robert Hoare 2, Gregory Holwell 1

1 University of Auckland, Private Bag 92019, Auckland Mail Centre 1142, Auckland 1010, NZ
2 Landcare Research, 231 Morrin Road, Auckland, 1072, New Zealand

Males of many animal species possess enlarged body structures that are used as weapons during contests with male conspecifics. Generally males with the largest weapon or body size have the competitive advantage during these contests. In some species where there is high natural size variation, smaller males have evolved alternative behaviours that do not rely on the use of weaponry to gain access to females for copulation. Males of the New Zealand giraffe weevil (Lasiorhynchus barbicornis) have an elongated rostrum which is used as a weapon to fight other males for access to females for reproduction. However, due to extreme size variation in this species where there can be a six-fold difference in body length of adult males, it is expected that smaller males will be less successful at defending females than larger males, and will therefore adopt alternative behaviours during mate searching and copulation. I will discuss the results from a series of focal animal observations conducted in January and February 2011 which revealed sneaking behaviours conducted by the smallest males. Alternatively males would defend females by guarding them both pre- and post-copulation, and use aggressive behaviours to fend off other male intruders.  I will discuss the probability in relation to body size of sneaking or fighting to secure access to females, and explore the factors that affect these conditional behaviours.  

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