Monarch butterflies in one of the reserves of Michoacn (Mexico).Getty Images

Spring is the time when the sex lives of many animals awaken and strategies begin. Male monarchs spray females with aphrodisiac powder and drag them to the ground, writes David Barrie in his work. The most incredible trips (Review, 2020). This powder is the set of chemical pheromones that butterflies use to differentiate themselves. It is a necessary technique to be noticed in the middle of a very dense forest hundreds of meters away, explains Zackary Graham, researcher at the School of Life Sciences of the Arizona State University (United States) and specialist in insects and crayfish.

In the animal world, everyone does everything possible so that it is their sperm that reaches the females egg

Elisa P. Bads, from the University of Groningen (Holland)

Other species are based on sexual dimorphism, that is, on physical differences based on sex, to attract their partners without having to resort to powders aphrodisiacs. Males take advantage of their appearance to attract the attention of females, such as turkeys with their great feathers, newts with their colors and crests, or elk with their antlers. On several occasions, the largest and strongest specimen is the one that seduces the female because it ensures a better offspring.

The Graham Research Team has published a study in the journal Biology Letters about a little-known species that also uses its physical advantages to get a mate: narwhals (Monodon monoceros). Most of the previous hypotheses indicate that the tusk that comes out of their forehead is used to hunt, fight and drive away predators. Although this idea is not ruled out, Graham wanted to go further when he saw that the females did not have one.

Thanks to a collection of data on the behavior of 245 adult narwhals over 35 years, the researchers confirm that these animals use their tusks to demonstrate to other males that they are better and stronger and attract females. If they have a long tusk, it means that their body is proportionally large. And there is the key: Females are more attracted to those that are larger because it indicates more and better quality sperm, explains Graham.

Something similar happens with squid and cuttlefish. The male consorts of some species of squid (Family Loliginidae) are larger than females and use their large size, physical strength, and aggressive skin color to scare off potential competitors while standing guard. Sometimes, they can have half of the body that is directed towards the female with the coloration romantic and the other half with the coloring aggressive, Explains Fernando ngel Fernndez-lvarez, expert in cephalopods and researcher at the Ryan Institute and in the School of Natural Sciences of the National University of Ireland (Galway). However, victory is never assured. An even bigger male can always come along and eject the other, supplant him and begin to copulate with the female.

Some females, depending on the species, have several places where the male can deposit his sperm: near the exit of the oviduct and near the mouth, through the seminal receptacle of the oral membrane. This curious morphology allows them to have eggs from different males. The squids called sneakers (the males more rogues) are the ones who take advantage of this curious feature. These specimens are the same size as the female and give off a similar color to her, so the dominant male, who stands guard, does not perceive them as a threat. However, these small animals approach the female and inoculate their sperm in the oral reproduction zone thanks to a head to head copulation, says Fernndez-lvarez. All this, without the consort noticing.

Squids and cuttlefish are not the only ones to accumulate sexual partners. In the world of birds, polygamy exists more than is believed. Since the 1990s, thanks to genetics, scientists have shown that some socially monogamous birds have copulations outside the nest to ensure good offspring. The objective is to find the best female or the best male to reproduce with quality. This is what Elisa Prez Bads, a researcher at the University of Groningen (Holland) and lead author of a study published in the journal Evolution on the behavior of the tit, a small species with a very striking blue and yellow plumage.

These birds have a very high reproductive rate, of about eight or nine chicks per year, and can take care of up to 16 children in a single nest. The sexual life of this species outside this time is very calm, even non-existent. It is such a strong investment to take care of your children that the rest of the year they are calmer, looking for food and resting to recover all that they have lost. They change their plumage to be beautiful the following spring, says Bads. Both the male and the female, if they are not satisfied with the quality of the eggs or if they see another with a more showy plumage, they can change partners. But in general, it is the female who is going to flutter in search of a male, the most handsome one, the one with the best territory and there she will build her nest, adds the expert.

Frogs and toads use sound to attract females. They go towards the specimen with the most powerful or frequent songs, signs of the good quality of the males genes. A curious thing highlighted by Ignacio De la Riva, an expert researcher on amphibians from the National Museum of Natural Sciences of the Higher Council for Scientific Research, is that, in certain species, there are male satellites that take advantage of the musical qualities of others. Instead of wasting energy singing, these specimens stay quiet near another male that emits sound. When the female approaches, he intercepts her and attempts to mate with her.

The bog lizard, the reptile with the largest land distribution in the world, plays rock, paper or scissors, according to a study published in the journal Biological Science. Patrick Fitze, one of the authors of the work and researcher at the MNCN-CSIC, explains that the species is divided into three colors determined by the alleles (orange, yellow and white) and each one has its territory. For the female, the most interesting thing is to mate with the less frequent color so that her children do not have to compete with the rest of the lizards of the same aspect. If the majority are oranges, it will go for yellow, when yellow multiplies, it will go for white, and then again for orange. And the game begins again, again and again. In this species there are also males sneakers They enter the territory of the other to mate with the females. We have called it rock, paper or scissors because each specimen can choose which strategy to use even if its genetics determine it, explains the researcher.

The strategies of animals to reproduce are numerous and varied. The list is long. Forced copulations can also occur, although uncommon, as does the cat, which uses the spines of its penis to drag and remove the sperm of the previous male, says Elisa P. Bads. In the animal world, everyone does everything possible so that it is their sperm that reaches the females egg, she concludes.

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The polygamy of birds, the adultery of squids and other sexual strategies of animals - Pledge Times

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