Dichotomous Choice Experiment Research Articles

Shoal Choice in Swordtails when Preferences Conflict

AbstractIndividuals obtain a range of benefits from aggregating with others. Evidence suggests that group size and the phenotypic characteristics of potential group mates are both important attributes influencing the grouping decisions of prospective group members. Their interaction, however, remains poorly understood. Here we investigate, in a series of dichotomous choice experiments, what happens when a preference with respect to group size is pitted against a preference for assorting on the basis of body size in swordtail fish. When controlled for body size, we found that swordtails preferred to associate with a larger shoal. When controlled for group size, we found that swordtails preferred to associate with similar‐sized fish. However, when offered the choice between a single size‐matched shoaling partner and four dissimilar‐sized shoal mates, we found that females associated randomly. Our results suggest that, depending on context, group size and body size may be equally important in guiding the aggregating decisions of swordtails. Future studies will likely offer valuable insights into shoaling behaviour by considering how, and under what circumstances, different grouping preferences might be prioritized.

Female mate preference based on male orange spot patterns in the feral guppy Poecilia reticulata in Japan

It is known that females prefer males with larger and/or brighter orange spots in many populations of the guppy Poecilia reticulata. However, female preference for male orange spots varies among populations and changes within several years when they are introduced into new habitats with different environment. Guppies were introduced into Okinawa, Japan, more than 20 years ago and were subjected to natural and sexual selection for a long period. The female preference for orange spot patterns of males was examined by the dichotomous choice experiment for a feral guppy population of the Hiji River, Okinawa. We chose full-sibling males as a pair of stimulus males that were simultaneously presented to a test female, because sibling males should resemble each other. To create different orange spot patterns between stimulus males, one male of the stimulus male pair was fed carotenoid-supplement food such as algae and another male was fed low-carotenoid food. High-carotenoid-treatment males showed not only brighter coloration of orange spots but also larger spots than other males as a result of this dietary-manipulation. In the dichotomous choice experiment, females preferred the high-carotenoid-treatment males. In addition, logistic regression analysis clarified that brighter coloration of male orange spots was the most important factor for female mate preference. This finding suggests indirect benefits of female preference for male orange spot patterns if the male foraging ability for algae were heritable.

Female preference for nest size in the stream goby Rhinogobius sp DA.

Females of the stream goby Rhinogobius sp. DA with paternal care favor males courting in fast water currents, whereby they mate males of high parental ability. Here we examined female choice of male nest size of this goby in laboratory. The dichotomous choice experiment clearly indicated that females prefer large nests. Spawning at large nests seems to improve egg survival rates in natural habitats in this goby. We discuss the possibility of multiple criteria in mate choice of this goby.

FEMALE MATE PREFERENCE IS FOR MALE TOTAL LENGTH, NOT TAIL LENGTH IN FERAL GUPPIES

AbstractExaggerated male traits can evolve either directly by female choice of males with those traits or indirectly by female preferences for related traits. In this study, we tested whether female choice was based upon male tail length or total length in a feral guppy population in Okinawa, Japan. In this population, about 30% of the males had elongated sword-like tails, and even swordless males had longer tails than females. A series of dichotomous female choice experiments revealed that female guppies chose mates by total length, not by tail length itself. This is inconsistent with the handicap principle. Tail elongation of male guppies may have evolved as a male mating strategy to enhance their attraction to females, mediated by female preference for longer male total length. However, only one-third of the males developed pronounced sword-like tails. This suggests that there are some costs for tail elongation or trade-offs between multiple sexually selected traits. Alternatively, tail elongation may be a deceptive male strategy with frequency-dependent success.