Peak Mating and Breeding Period of the Humpback Whale —(Megaptera novaeangliae) in Okinawa Island, Japan

Although detailed knowledge on breeding ecology of humpback whales is required for developing effective and sustainable whale watching programs in breeding areas, the breeding ecology of this species is still poorly understood. Hence, we examine the migratory timing of humpback whales in Okinawa that is one of their breeding ground, distinguishing the reproductive status (male, female, or female with a calf), group compositions (singleton, pair, or whales more than three) and group types (singer or competitive group) in order to assess the peak period of breeding activities. A total of 1192 days of photo-identification surveys were conducted from 1991 to 2012 and a total of 7366 humpback whales were sighted during the surveys. Among them, 1284 whales were sex-determined (848 males, 147 females and 289 females with a calf), 1138 singletons, 1416 pairs and 710 groups of more than three whales were observed. Females without calves tended to occur from late January to late February, which was the beginning of the breeding season and male-female pairs were observed most frequently during this period. The peak occurrence of competitive group which was considered a mating-related behavior group, formed by females and males, was also observed during this period. These results indicated that humpback whales peak mating period in Okinawa occurred between late January and late February. Females with a calf tended to increase from mid-February toward the end of the breeding season maintaining a high sighting per unit effort (SPUE) value in late March. We, therefore, suggested that the peak time of birthing and newborn care was probably that period in Okinawa. These findings extended our knowledge on the reproductive ecology of humpback whales in Okinawan waters.

Contrasting female mate preferences for red coloration in a fish

Understanding how animals select their mates requires knowing the factors that shape mate preferences.Recent theoretical and empirical considerations suggest that female mating status can influence the degree to which a female engages in mate choice,with virgin females predicted to be less choosy than mated females.In this study,we investigated mate choice in both virgin and mated females in the pygmy halfbeak Dermogenys collettei.Halfbeaks are small,live-bearing,internally fertilizing freshwater fish that live in mixed-sex groups where females have ample opportunity to engage in mate choice.Using a dichotomous choice assay,we quantified and contrasted in virgin and mated females mate preferences for differences in male body size,beak size,and area of yellow and red coloration.We also examined how mating status influenced the amount of time a female associated with the first male encountered and the relative amount of time a female associated with each male.We demonstrate that mate preferences of female halfbeaks are driven primarily by the size of red coloration present on males.Females showed contrasting preferences based on mating status,with virgin females preferentially associating with drab males whereas mated females preferentially associate with males possessing large areas of red.Contrary to expectations,female mating status did not influence how females associate with the first males encountered or how females biased their association time among males.Although the precise drivers of these effects need further studying,our finding highlights a possible explanation for how variation in male ornamentation can be maintained.