Animals and sex

Seychelles giant tortoises moan when they mate. The male tortoise appears to enjoy himself, judging by his moans. But what about his female mate? Biologist Justin Gerlach, who runs a breeding center for giant tortoises in the Republic of Seychelles, observes their behavior daily.

If they are kept in small enclosures, Gerlach said, the females can't get away - and the males are constantly harassing them. "So the females are very nervous, difficult to approach," Gerlach said.

It seems as if the male tortoises are constantly forcing the females to have sex. But are they really being forced? Do female animals feel anything during sex?

Gray area

Probably not much, says biologist Sebastian Baldauf, who has researched sexual selection, or how animals choose their mates, at the University of Bonn.

Baldauf told DW that for a variety of animal species, the sexual act probably doesn't matter. "But no one really knows - this is a gray area," he added.

Scientific studies do exist. But it has proven difficult to measure what happens in the brains of female animals during sex - whether they experience pleasure or pain. Researchers can only deduce possible sensations from their behavior.

'Like business'

There are several scientific theories for why orgasm evolved in humans, including the notion that pleasure incentivizes reproductive activity, thus ensuring the species continues.

It's been proposed that among our closest relatives - the great apes - females may also feel pleasure during sex. Researchers have established that the vagina of some great ape females contracts during sex.

And female bonobos make a specific call during sex. But this may simply be behavior that fulfills a specific purpose, such as stimulating the male to provide more sperm, Baldauf said.

He added that it's not clear whether this would really reflect a form of arousal, or rather a way to "stimulate the males to ensure that the chosen partner, who can bring benefits, can actually have offspring."

In any case, mating ensures that animals - males and females alike - spread their genes. While the search for a suitable partner to have offspring can often take a long time, the sexual act is typically fast and simple, according to Baldauf.

"With animals, sex is more like business," he said. For both genders, it's about having the most and best offspring. "So when two such partners meet, the male is keen to transfer his sperm and the female to receive it," he added.

Anthropomorphizing sexual selection

We humans often falsely interpret the behavior of female animals during or shortly before sex. One example is freshwater shrimp. With this domestic type of crustacean, the larger male grabs the female during the mating season and holds it, often for two to three weeks, until the female is ready for fertilization. During the entire time, the female fights the male in an effort to push it aside.

But Baldauf said that what looks like a defensive move on the part of the female is actually a process of sizing up the partner - whether or not he is strong enough to hold onto her. Through this defensive maneuver, the female selects a mate that guarantees strong offspring.

"So it's not a case of rape or unwanted sexual activity as it may appear, but rather true sexual selection to ensure a desired trait," Baldauf said.

Female Seychelles giant tortoises appear to select the best males by constantly "pushing" themselves around before sex, says Gerlach.

"It's true for some males that the females really don't want him," Gerlach said. "But it does seem there needs to be a bit of effort from the male," he added. The females actually want him to make an effort, so they are not being too easy, Gerlach said.

Fortunately for rare species like giant tortoises, the males don't have to put up with a long drawn out fight to get the perfect female tortoise.

Author: Brigitte Osterath / jb

Editor: Anke Rasper