Would you be willing to risk it all for the chance to reproduce? The logical answer would be no. All mating comes with costs and benefits but for some species the costs are far greater. There is no better example of this than in the springbok mantis, or Miomantis caffra. Females of this particular species are known to take part in precopulatory sexual cannibalism. This means that females will eat males of their own species regardless of their mating status. This is a common occurrence as over 60% of intersexual encounters (between a male and a female) result in cannibalism. This begs the question, how is this species able to reproduce? Female springbok mantises are facultative parthenogens, meaning that they can produce offspring asexually. Because females have little use for males as a mating partner, they would prefer to utilize them as a tasty snack. Therefore, males must adapt their behavior to successfully mate with females in order to pass on their genes. Based on the knowledge that springbok mantises eat males in the absence of copulation, Burke et al. investigated whether males modify their mating approach in the presence of male competition and/or prey.
Much like humans, female springbok mantises prioritize their food, often distracting them from outside stimuli. In their study, “Increased male mating success in the presence of prey and rivals in a sexually cannibalistic mantis”, Burke et al. manipulated factors such as presence of prey and male competition, to account for different environmental conditions that males might encounter when approaching a female. In preparation of the experiment, females were fed the night before with five houseflies to remove hunger as a variable. For the first two treatments, females were placed into mesh enclosures in the presence of 40 prey (houseflies) or in the absence of the prey. Burke and colleagues conducted two additional treatments where they introduced male competition. For these treatments there were two males and one female in the presence and absence of prey, respectively. One male was always placed in the enclosure first, and after the first male’s placement, a second male was placed on the opposite side of the cage. It is also relevant to note that temperature was controlled for, being kept at 13-20℃ to ensure the houseflies were not overactive or inactive.
This experiment was created to test three different hypotheses. The first was that the male mantises would adapt to the feeding behavior of the females by approaching them more often and more quickly in the presence of prey. The second hypothesis from Burke et al. predicted that male-male competition would increase a male’s motivation to mate. They believed that male competition, coupled with the presence of prey, would result in the fastest matings. Finally, they hypothesized that male competition in the absence of prey would increase the degree of cannibalism.
Interestingly, the results of this study support the first and second hypotheses, but not the third. In fact, mating was initiated more quickly and more often in the presence of prey. When flies were available, females spent their time hunting, and were distracted from their male suitors. The males used this foraging behavior of the females to their advantage in their approach; the males ignored the prey completely and focused solely on both visual and pheromonal cues from the female. Furthermore, when an additional male was added, mating occurred at a greater and faster rate than any other treatment. In the absence of prey, when male competition was both present and absent, mating occurred at a much lower rate. However, out of 76 trials, cannibalism only occured twice. No relation between treatment and cannibalism was identified. This could be explained by the short length of the trials, or the fact that females had been fed the night before.
In the world of science it is well known that females of many different species, more specifically springbok mantises, will engage in cannibalistic activities following copulation, to provide necessary nutrients and fuel to produce offspring. However, this study is exciting because it explores cannibalistic tendencies of a species prior to mating. In this case, females have little use for males, which creates an environment where their food approaches them on a silver platter. The idea of understanding how a group of male individuals, in this case springbok mantises, can change their approach to a situation for greater success, is a very useful tool. This understanding of the adaptive behaviors of a species can help scientists predict how they will adapt to the ever changing world that we live in today, as we face issues such as climate change. Ultimately, this study could help us develop new ways to protect this species, and many others like it.
References:
Burke, N. W., Holwell, G. I. (2021). Increased male mating success in the presence of prey and rivals in a sexually cannibalistic mantis. Behavioral Ecology. 32(4):574–579. doi:10.1093/beheco/arab022.
