Unlike many insects, burying beetles co-parent their young. It's actually kind of a beautiful love story, so let's get into it: The insects swarm over the carcasses of small animals and fight to the death – males fighting males and females fighting females. To the victors go the spoiled meat, and the result is the ultimate meet (meat?) cute. The lovers dig a hole, strip the dead animal of fur and feathers (with which they line their love nest) and then slather the meat in anti-microbial bodily secretions.
You know, just your typical first date.
"Parents of many species cooperate to rear offspring, but nevertheless there can be intense conflicts between males and females over mating rate or how much each sex should invest in raising the young," the authors, led by Sandra Steiger of the University of Ulm, wrote in the study. For males, it might make sense – in terms of energy expenditure – to move on and find a new mate to have even more offspring with, or at least to keep trying to produce a constant stream of new young with their current mate. But having as many kids as possible isn't always the best strategy. Sometimes it's best to focus on making sure that a few of them get the attention they need to survive to sexual maturity, ensuring that parental genes will live to see another generation.
That's the strategy burying beetles have evolved for, but that doesn't mean each individual male is going to instinctively cherish its offspring. And even selective female infertility isn't enough to really solve that problem: If males keep trying to mate with an infertile partner while she tries to raise the kids, he's wasting valuable time and energy that could have gone right to those offspring. That's where the anti-aphrodisiacs come in.
Most female animals that use pheromones to coordinate mating efforts use the chemical signals to broadcast their fertility – but the female burying beetle seems to do the exact opposite.
Don't feel too bad for those male burying beetles, by the way: This critical phase of parenting lasts just three days. Then it's back to business.