Spatial Dynamics and Breeding Ecology in the Cicada Cystosoma saundersii: The Interaction Between Distributions of Resources and Intraspecific Behaviour

(1) The population dynamics of adults of Cystosoma saundersii are examined with special emphasis on the spatial dynamics of males and on the mating success associated with contrasting patterns of reproductive behaviour.

(2) More males spend longer periods on, and attract more females to, smaller bushes (<8 m3) than larger bushes (>8 m3).

(3) The spatial arrays of males are clumped independently of the distributions of the bushes from which they sing. Bushes were given relative weightings based on male preferences for different size classes of bushes. The inclusion of these weighting factors did not affect the above conclusion.

(4) Males who share bushes space out so that they are 1.0 to 1.5 m apart.

(5) The spatial arrays of males were found to depend, to a certain extent, on the distribution of males on the previous night.

(6) Females select males only on the basis of their acoustic displays. The most successful males at obtaining matings were those which appeared to enhance the propagation of their songs by adopting several behavioural strategies. These strategies include the selection of smaller bushes; singing at a height which is maximally efficient for transmitting their song frequency; and by singing in close proximity to other males. Males occurred in pairs, trios and other multiples in bushes more frequently than would be expected in random distributions. Such males attract more females per capita than do isolated males.

(7) The probability of attracting a female is independent of the amount of time a male has already been singing. Thus the most successful males are those which adopt the patterns of behaviour outlined above for the longest time (2-3 weeks).