|dc.description.abstract||Sexual behavior in the field crickets, Gryllus veletis and G. pennsylvanicus , was
studied in outdoor arenas (12 m2) at high and low levels of population density in 1983 and
1984. Crickets were weighed, individually marked, and observed from 2200 until 0800
hrs for at least 9 continuous nights. Calling was measured at 5 min intervals, and
movement and matings were recorded hourly. Continuous 24 hr observations were also
conducted,·and occurrences of aggressive and courtship songs were noted.
The timing of males searching, calling, courting, and fighting for females should
coincide with female movement and mating patterns. For most samples female movement
and matings occurred at night in the 24 hr observations and were randomly distributed with
time for both species in the 10 hr observations. Male movement for G. veletis high
density only was enhanced at night in the 24 hr observations, however, males called more
at night in both species at high and low densities. Male movement was randomly
distributed with time in the 10 hr observations, and calling increased at dawn for the G.
pennsylvanicus 1984 high density sample, but was randomly distributed in other samples.
Most courtship and aggression songs in the 24 hr observations were too infrequent for
statistical testing and generally did not coincide with matings.
Assuming residual reproductive value, and costs attached to a male trait in terms of
future reproductive success decline with age, males should behave in more costly ways
with age; by calling and moving more with age. Consequently, mating rates should
increase with age. Female behavior may not change with age. G. veletis , females moved
more with age at both low density samples, however, crickets moved less with age at high
density. G. pennsylvanicus females moved more with age in the 1984 low density
sample, whereas crickets moved less with age in the 1983 high density sample. For both
species males in the 1984 high density samples called less with age. For G.
pennsylvanicus in 1983 calling and mating rates increased with age. Mating rates
decreased with age for G. veletis males in the high density sample. Aging may not affect
cricket behavior. As population density increases fewer calling sites become available, costs of
territoriality increase, and matings resulting from non-calling behavior should increase.
For both species the amount of calling and in G. veletis the distance travelled per night was
not different between densities. G. pennsylvanicus males and females moved more at low
density. At the same deneity levels there were no differences in calling, mating, and,
movement rates in G. veletis , however, G. pennsylvanicus males moved more at high
density in 1983 than 1984. There was a positive relationship between calling and mating
for the G. pennsylvanicus low density sample only, and selection was acting directly to
increase calling. For both species no relationships between movement and mating success
was found, however, the selection gradient on movement in the G. veletis high density
population was significant. The intensity of selection was not significant and was probably
due to the inverse relationship between displacement and weight.
Larger males should call more, mate more, and move less than smaller males.
There were no correlations between calling and individual weight, and an inverse
correlation between movement and size in the G. veletis high density population only. In
G. pennsylvanicus , there was a positive correlation between individual weight and mating,
but, some correlate of weight was under counter selection pressure and-prevented
significance of the intensity of selection. In contrast, there was an inverse correlation in the
G.·veletis low density B sample. Both measures of selection intensities were significant
and showed that weight only was under selection pressures. An inverse correlation
between calling and movement was found for G. veletis at low density only.
Because males are territorial, females are predicted to move more than males,
however, if movement is a mode of male-male reproductive competition then males may
move more than females. G. pennsylvanicus males moved more than females in all
samples, however, G. veletis males and females moved similar distances at all densities.
The variation in relative mating success explained by calling scores, movement, and
weight for both species and all samples were not significant In addition, for both species
and all samples the intensity of selection never equalled the opportunity for selection.||en_US