The battle of the sexes may begin as early as conception

Wed, 04 Dec 2024 06:00:00 GMT

Mathieu Douhard, Eric Baubet, and Marlène Gamelon: Read the article

Mammalian adult females generally live longer than males in the wild, but it is poorly known whether sex differences in prenatal mortality occur, and if so, in what direction. Douhard et al. found a higher embryonic mortality for females than for males in a wild boar population.

The battle of the sexes is occurring within the female body. Previously it was thought that sex ratio at conception and prenatal mortality (embryos missing the implantation window) are biased toward males. Therefore, male embryos were thought to be in excess at conception and experience higher prenatal mortality. A new study by Mathieu Douhard, Eric Baubet, and Marlène Gamelon on French wild boar (Sus scrofa) challenges these classical predictions in wild mammals.

In mammals, prenatal sex ratio prior to implantation is difficult to study. Embryos experiencing prenatal mortality are often reabsorbed by the mother’s body, making it impossible to know if and how many eggs were ovulated. However, female wild boars do not reabsorb the corpus luteus, the outer shell that remains in the mother’s ovary after releasing a mature egg. The authors determined sex ratio of prenatal mortality by dissecting wild boar ovaries, counting the corpora lutea, and comparing this number to the sex ratio of fetuses. Sex ratio at conception was determined using litters with no embryonic mortality. These techniques yielded shocking results.

This study found that sex ratio at conception was not only balanced, but that female rather than male embryos experienced higher prenatal mortality, contradicting classical predictions. The female bias in prenatal mortality was especially skewed in larger litters and was independent of food availability or the mother’s body mass. The authors hypothesize that female embryos develop slower than males after conception, therefore missing the narrow implantation window. This study opens the doors to questioning long-standing predictions of prenatal sex ratio and embryonic mortality and the implications it may have on prenatal competition.

Julia Dovi is a master’s student in the Department of Ecology and Evolution at Stony Brook University. She is passionate about research on animal responses to stress associated with climate change and the genetic mechanisms underlying changes in behavior. She enjoys traveling, playing the piano, and hitting the dance floor.

“Wasted Efforts Impair Random Search Efficiency and Reduce Choosiness in Mate-Pairing Termites”

Tue, 19 Nov 2024 06:00:00 GMT

by Nobuaki Mizumoto (水元惟暁), Naohisa Nagaya (永谷直久), and Ryusuke Fujisawa (藤澤隆介)

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Mizumoto et al. reveal that limited energy reduces termite search efficiency but that they compensate for it by lowering partner selectivity. Their study shows animals can't always achieve optimal search strategies, but can adjust their decision-making accordingly...

Imagine you are searching for a soulmate, and you have only a few days remaining to live with a declining energy reserve… Sound stressful? Welcome to the life of termites following their dispersal flights. A new study performed by Dr. Nobuaki Mizumoto and colleagues finds that termites (Reticulitermes speratus) are choosy when they initiate mate searches, but rapidly shift strategies as their energy supplies start to dwindle, settling on the first available partner. The study highlights how diminishing reserves can change search strategies, changing the choosy termite into the pragmatic partner. The work fills in an unexplored gap in search theory by considering the internal condition of the searcher.

Following termite dispersal flights, reproductive individuals shed their wings and search for a mate on foot with limited energy. In general, random search theory predicts that animals searching for mates should ideally maximize their encounter rate. However, this research shows that internal states—such as energy depletion—can push real-world behavior away from optimal searching toward a more flexible strategy.

The researchers monitored termite movement on a specialized omnidirectional "servosphere" treadmill and recorded how search patterns shifted over several days. Immediately following flights, termites were speedy and efficient, pausing very little. By the third day, though, the researchers noticed they had slowed considerably and took frequent breaks. To see how these changes affected encounter rates, researchers ran simulations that showed that termites in the low-energy mode had a lower chance of finding an ideal mate, settling instead for any partner as time passed. Additionally, long searches had fitness costs beyond the energetic ones; termites that searched for longer had reduced survival and lower offspring output than those that paired quickly.

Traditional models for the study of animal search strategies have often assumed that the animals are always behaving optimally. However, this study illustrates how a flexible switch between strategies can help animals cope with internal constraints. By considering the internal state of the individuals, the study provides a more realistic and naturalistic understanding of how animals balance survival and mate choice. The researchers were happy to be able to share these perspectives, especially after an unexpected loss of data and further recovery using data recovery services, underscoring the importance of data backup in science.

By showing how internal energy reserves can influence mate search and choice, termites provide a really fascinating example of real-world search behavior that adapts to both internal and external pressures. Termites remind us that when time runs out, and survival and reproduction get priority, the ideal partner is simply the one you happen to be lucky enough to find.

Purbayan Ghosh is a PhD student working in the lab of Prof. Stephen Pratt at Arizona State University, USA. His research focuses on how behavior and physiology come together during nest site selection in the rock crevice nesting ant Temnothorax rugatulus. When not looking at ants, he enjoys travelling to new places, hiking, playing sports, or hunting down the best food spots in the town.

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The battle of the sexes may begin as early as conception

“Wasted Efforts Impair Random Search Efficiency and Reduce Choosiness in Mate-Pairing Termites”