Cricket calling

Issue 15, June 1999

Male variable field crickets (Gryllus lineaticeps), see Figure 1, produce calls (chirps) to attract females. Males that are able to chirp faster, or for longer, may do better (i.e. attract females sooner or attract more females) than males that can't chirp at such a high rate or can't sustain their rate of calling. It may be that males that feed well can chirp faster and for longer than males that don't feed well and two researchers* in California set out to test this.

Figure 1. A typical cricket (the variable cricket looks very similar).

The study was carded out in the lab using male variable field crickets that been reared in identical conditions. The males were pairs of full-sibling brothers that had reached sexual maturity within a day of each other. The two brothers were randomly allocated to one of two different feeding regimes. Both sets of males received the same mass of food each day (25 g) but one male had food of a higher nutritive status than the other. They fed on the foods for 8 days and had their mass recorded each day. Eight days after the feeding regime started the testing began. The researchers put each pair of animals in an arena and recorded their calling behaviour in response to a tape recording of male crickets chirping. The researchers recorded the number of chirps produced by each of the test pairs of males and also their rate and duration of chirping.

* Wagner, W. E. and Hoback, W. W. 1999. Nutritional effects on male calling behaviour in the variable field cricket. Animal Behaviour, 57, 89 - 95.

1. In this research on variable field crickets, the participants were cricket males who were brothers. The researchers stated that, "We randomly chose one brother of each pair to be placed on a high-nutrition feeding regime, and placed the other brother on a low-nutrition feeding regime." Why did they randomly allocate the animals to the two feeding regimes? (2)
2. What might be an advantage in an experiment like this in using crickets that were brothers? (1)

Figure 2. The effect of the nutrition regime on the change in mean male body mass. - graph goes here


3. Figure 2 shows how the different feeding regimes affected the change in the mass of the crickets during the experiments. What does the graph suggest and why was this an important aspect of this study? (2)

Figure 3. The effect of the feeding regime on the proportion of males calling.


4. Figure 3 shows how the different feeding regimes influenced the proportion of males who were calling during the period of observation. What interpretation can be placed on the findings? (2)
5. What type of graph has been used in Figures 2 and 3? (1)
6. A paired t-test was used by the researchers when they analysed the data shown in Figure 2. Why was this an appropriate test to use in the analysis? (2)
7. The males on the high-nutrition feeding regime called at a higher chirp rate than did males on the low-nutrition feeding regime - the former called at a mean chirp rate of 109.6 chirps/s and the latter at a mean chirp rate of 59.8 chirps/s. Under what condition is the mean usually used in preference to the median as a central tendency measure? (1)
8. Females, it seems, choose a mate partly on the basis of his chirp rate, those males with higher chirp rates are preferred. Why do you think that the chirp rate is a good indicator to a female of the quality of a male? (2)