Male sand gobies are likely to cannibalize slower developing eggs they are guarding so that they spend less time taking care of the brood and can mate again, according to a study by scientists in Finland published in the most recent issue of the journal Biology Letters.
Male sand gobies breed sequentially with two females and then take care of the brood until they hatch.
Hope Klug and Kai Lindstrm spawned sand gobies in an aquarium, and then observed the male goby, keeping track of the eggs laid by each female.
They found that mean egg size was positively correlated with mean egg development time, suggesting that larger eggs take longer to develop, and that male gobies that had partially consumed their clutches showed a significant preference for the larger eggs laid by the second female they spawned with.
The authors write reference for the larger eggs of female 2 is potentially associated with decreasing the duration of parental care. Larger eggs took longer to develop and the eggs of female 2 were already slightly behind those of female 1.
Thus, the larger eggs of female 2 would probably hatch later and require a longer duration of care than female 1 s eggs and the smaller eggs of female 2.
Consuming the larger eggs of female 2 potentially allows a male to decrease time spent caring for the current brood, thereby allowing the male to re-enter the mating pool sooner. In this system, nest sites are limited, and simply abandoning the current brood is unlikely to allow a male to re-enter the mating pool quickly.
For more information, see the paper: Klug, H and K Lindstrm (2008) Hurry-up and hatch: selective filial cannibalism of slower developing eggs. Biology Letters 4, pp. 160"162.