You just don't understand sexual cannibalism

We call those deadly spiders with the red hourglass shapes on their abdomens "black widows" because they eat their mates as part of the sex act. But black widows are far from the only spiders who sexually cannibalize, and some insects and fish do it too. It's just a natural part of some animals' reproductive process. So why use a term like "widow" for a creature who has no notion of marriage, and who is part of a species that evolved to eat or be eaten during sex? That's what British biologist Emily Burdfield-Steele and her colleagues wanted to find out.

Their hypothesis was that people, including scientists, were grossly misunderstanding spider reproduction because they couldn't stop anthropomorphizing the creatures involved. Instead of seeing a natural spider sex act, they kept seeing "widows" and "male sacrifices." Those are decidedly human ideas. To find out whether this anthropocentric bias was pervasive, the biologists conducted a survey of 47 scientific papers about sexual cannibalism, to see how the act was described. Not surprisingly, they discovered a lot of non-scientific (and inaccurate) terms like "rapacious" and "voracious" attributed to the females; the males were called "unwilling" and "suicidal" in some cases. They created a fascinating chart of the most popular human-centric terms used to describe the spidery experience of sexual cannibalism.

You just don't understand sexual cannibalism

Click to enlarge. In their paper published earlier this month in Animal Behavior, the researchers describe what you're seeing in this chart:

Frequency of terms used when describing male and female behaviour of sexually cannibalistic species considered separately for (a) studies in which cannibalism occurs before and/or during copulation (26 papers) and (b) studies in which cannibalism occurs only during and/or after copulation (17 papers), excluding reviews. See the appendices for references and excluded words. The frequency for each sex is the number of articles the term appears in, in the context of describing behaviour. Words were also classified by three independent observers as active (a), reactive (re) or neutral (n). Terms marked with an asterisk were classified differently by at least two of the parties and so could not be given an overall classification.

It's fascinating to see how the females are more often described as "attacking" or "predatory" if they eat their mates before or during sex, versus afterwards. Maybe eating somebody after sex doesn't strike us as being quite so aggressive?

In ScienceNOW, the researchers explain the trouble with this kind of language:

They found, for example, that female sexual cannibals were described with overwhelmingly negative language. Twenty-three of the studies used the words "aggressive" and "attack" to describe female behavior. Other common labels included "predatory," "voracious," and "rapacious." The most typical words for male behavior, meanwhile, were "escape," "sacrifice," and "avoid." These passive words were used to describe even those species in which the males were actively trying to get away.

"The word 'sacrifice' implies a level of nobility, like they're doing something selfless. But even for the males that are allowing themselves to be eaten, it's not selfless at all," Burdfield-Steel says. If his partner has better nutrition, she will lay more eggs, and the male will pass along more of his genes.

"The problem with these words is that they make moral judgments about the behavior of the animal," Burdfield-Steel says. "It might seem to human eyes vicious to eat your mate, but that is just the spider being the spider."

Another interpretation of these results, Burdfield-Steel says, is that this choice of language accurately portrays what is going on. Rather than reflecting the human femme fatale stereotype, female sexual cannibals really could be predatory and voracious. Without searching for this potential bias in their studies of sexual cannibalism, however, researchers will never know which is true, she says.

"I have sympathy for efforts to remove biases in science so was pleased to see this paper," says Patricia Gowaty, an evolutionary biologist at the University of California, Los Angeles. "That said, I think the authors missed an important point." One of the main goals of animal behavior research, she says, is to operationally define behaviors so that another scientist not involved with the research could read the definitions and use them to replicate the experiment and quantify the movements and actions of the animals. Many of the words identified by Burdfield-Steel and colleagues, such as "voracious," can't really be operationally defined.

The problem isn't the sexual stereotypes implied by these words, Gowaty says, but that other scientists can't apply them to observe the same behaviors. Scientists should avoid them because they are imprecise, not because of any potential bias. "I wonder what in the world some of these words are doing in any scientific paper."

When it comes to sex, even scientists get a little too poetic ā€” and anthropecentric ā€” to reach rational conclusions.