Abstract
In some species males increase their reproductive success by forcing females to copulate with them, usually by grasping the female or pinning her to the ground to prevent her from escaping. Here we report an example of males coercing copulation by trapping a female in a confined space. During mate-searching, female Uca mjoebergi fiddler crabs visit males and choose whether or not to enter their burrow for inspection. Males typically enter the burrow first and we found that 71% of females will follow him down and 54% decide to stay and mate. However, some males use an alternative tactic where he will wait for the female to enter the burrow first, after which he traps her inside. Although a significantly lower percentage of females will enter a burrow following this behaviour (41%), upon entry 79% females that enter will become trapped and almost all of these females (90%) produce a clutch of eggs. Our observations suggest that males are able to gain fertilisations from females that may not have remained in the burrow by trapping them and coercing them to mate.
Highlights
Our preliminary observations suggested that females were less likely to enter a burrow when the male stepped aside, which was in line with a previous study on another fiddler crab, U. lactea perplexa, which displays this mating system [15]
The size of the female did not relate to her decision to enter the burrow in response to the male’s behaviour (χ 2 = 2.39, P = 0.12), and there was no significant interaction between female body size and male mating tactic (χ 2 = 0.01, P = 0.93)
We found that the mating tactic performed by a male crab as a female approaches his burrow has a significant effect on the probability that the female will enter the burrow and a marginally significant effect on whether she will remain in the burrow to mate
Summary
We determined whether male body size related to the type of mating tactic used because we hypothesized that a specific subset of males perform the alternative ‘step aside’ tactic We predicted that these males would be significantly smaller in body size (and have smaller, less attractive claws [35]) than males entering the burrow first, to allow them to have mating opportunities that they may not have otherwise had [2, 3]. In relation to this we predicted that males that step aside would perform this behaviour consistently over time. Fertilisation success by checking for the production of an egg clutch for a subset of females that were trapped or entered burrows by choice
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
