How animals protect themselves from sexual aggression in the wild

When news of sexual abuse increases, women respond. Social networks fill with videos and tweets from people who seek to educate others on the problem. In human beings, education is the best strategy when it comes to reducing aggression.

But we are not the only ones who have to fight this phenomenon. Sexual coercion is a frequent practice in nature too. It occurs when males force females into situations that will make it more likely they will mate with them, or less likely they will mate with other males. This coercion can take different forms: intimidation, punishment, harassment, and even forced copulation.

For the males that practice it, sexual coercion is an adaptive strategy that improves their chances of reproducing, but for the females the aggression often involves injuries and energy expenditure because it reduces the time they can devote to finding food, while also generating physiological stress and increasing mortality.

For this reason, females have developed various strategies to fight against male aggression. Here are six striking examples:

Synchronized swimming among dolphins

Group sexual aggression is rare, documented only in humans, several other primates and bottlenose dolphins (Tursiops spp.). A number of long-term studies have shown that male dolphins form stable alliances with other males in order to coerce females. Biting, hitting, chasing and threats are frequent until they get what they want.

In Shark Bay, western Australia, female dolphins have often been observed practicing a behavior known as contact swimming, in which one dolphin rests its pectoral fin against another and they swim in sync, sometimes for long periods of time. A paper published in 1996 proposed that contact swimming was a type of cooperation between females to boycott male harassment, as it was often initiated in environments in which they were being exposed to such aggression.

Chickens and moose manipulation

Females of many animal species produce loud noises during copulation. The function of these noises is still being debated, but some researchers suggest it may be a strategy used to manipulate males.

Female chickens and Alaskan moose frequently suffer forced copulation. When this happens and they know there is another dominant male nearby, they produce loud noises to attract him. In this way they manage to generate competition between the two males and rid themselves of the unwanted encounter.

Baboons shorten their menstrual cycle

Chacma baboons (Papio ursinus) live together in large groups. When a female ovulates, the area around the vagina fills with blood and swells noticeably for several days. During this period, males often coerce females into mating.

A recent study has shown that the duration of the swelling is variable and that, when there are many males in the group and the coercion is intense, the females shorten this period, thus reducing the number of aggressions. Since coercion begins before ovulation, it could be the stress experienced by the females that causes the swelling to last less time.

Fishy group strategy

Poeciliids (Poeciliidae), a group of freshwater fish with internal fertilization, are a prime case of sexual conflict. Males can perform one copulation per minute. On the other hand, females do not need so much activity, since a couple of sexual encounters are enough to fertilize all their eggs. This creates an imbalance in which the males constantly disturb and harass the females, who prefer to spend their time looking for food.

These fish form schools to escape predators, as synchronized movements make it difficult to focus on any one individual. Female poeciliid fish use this same strategy to get away from males. The larger the school, the better. Moreover, smaller females will sometimes attach themselves to larger females, as these are more attractive to males.

Frogs that croak to scare off unwanted advances

Frogs are one of the animals most affected by sexual coercion. Males perform amplexus, in which he approaches the female from behind and embraces her dorsally with his front legs, limiting her movements to the point of strangling her. The amplexus can last for several days with no chance of escape.

It has been discovered that there is a species of frog, however, called the Pelophylax nigromaculatus, whose females croak loudly when there is a male nearby, scaring him away. This is a very effective strategy against sexual coercion, but why does it work? Females without eggs vocalize more frequently than those with eggs. It is possible that the males interpret these vocalizations as a signal that the females have no eggs to fertilize and are therefore not worth the bother.

Orangutans seek protection from older males

Orangutans are the only primate in which forced copulation is frequent. Several factors contribute to this situation: a very marked sexual dimorphism, a semi-solitary lifestyle, long periods between the birth of offspring (between six and nine years) and the fact that the ovulation period, unlike in baboons, has no outward signs.

Adult males that have already developed all their secondary sexual characteristics, such as long hair and cheek ridges, attract receptive females with long calls. However, immature adults are not so successful and only manage to copulate by force. In this case, the female’s strategy is to approach a more mature male to keep the immature male at bay. The protection is temporary. When the threat is over, females prefer to feed alone, since adult males ingest a lot of food.

It is striking that many of these strategies avoid social isolation, as if nature is emphasizing the importance of having a strong social network.

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