Spatial Dispersion and Agonistic Contacts of Male Bush Crickets in the Biotope

Authors


Fachbereich Biologie-Zoologie, Philipps-Universität, Lahnberge, D-3550 Marburg/Lahn

Goldsmith's College, Department of Biology, Rachel McMillan Building, Creek Road, Deptford, London SE 8 3BU, England.

Abstract

Abstract and Summary

This study concerns the acoustic behaviour of the bush cricket Tettigonia cantans Fuess. (Orthoptera: Tettigoniidae). Natural habitats with different population densities of stable singers have been selected. The dispersion patterns of singing males and the sound levels neighbouring insects receive from each other were investigated. The behavioural patterns of an established male elicited by the song of a conspecific were analysed and related to the population densities of constant singers in their biotope. The competition between males and its possible effect on female behaviour have been discussed.

Constantly singing males clump in areas with dense vegetation and within these clumps they are regularly spaced. Males seem to space themselves according to the song intensities (72–87 dB SPL) they receive from each other.

Between close neighbours rivalry behaviour is expressed either by males producing alternating songs, or in an approach towards a constantly singing insect, or in an aggressive encounter. Of these three behaviour patterns aggressive encounters are most common in high-density populations. Rivalry does not influence the dispersion pattern of the males. A hypothesis is inferred from observations on female behaviour that rivalry itself constitutes an attractive stimulus for females.

Zusammenfassung

Rivalenverhalten und Verteilung konstant singender Männchen der Laubheuschrecke Tettigonia cantans sind im Freiland untersucht worden. Dazu wurden unterschiedlich dichte Populationen gewählt.

Konstant singende Männchen treten in Arealen mit dichter Vegetation gehäuft auf, sind aber innerhalb soldier Ansammlungen regelmäßig verteilt. Offenbar verteilen sich die Männchen nach gleichen Schalldruckpegeln (72–87 dB) im Gesang der Nachbarn.

Das Rivalenverhalten kann in abwechselndem Singen eng benachbarter Männchen bestehen, in bloßer Annäherung an einen konstanten Sänger oder kann eine aggressive Begegnung einschließen. Besonders in dichten Populationen kennzeichnen agonistische Kontakte das Rivalenverhalten. Das Rivalenverhalten beeinträchtigt jedoch nicht das regelmäßige Verteilungsmuster der Männchen.

Beobachtungen an Weibchen lassen vermuten, daß das Rivalenverhalten selbst einen stimulierenden Einfluß auf Phonotaxis und Auswahlverhalten der Weibchen ausübt.

Ancillary