You know what they say: the louder the calls, the smaller the balls. OK, so maybe they don't say that, but they could start following research published Thursday in Current Biology. The Salt Lake Tribune reports researchers discovered the smaller a howler monkey's testicles, the deeper and louder his mating call. According to a University of Utah press release, primatologist Leslie Knapp believes this is because the loudest monkeys spent so much energy developing the hyoid bones in their vocal boxes, other, uh, areas were unable to grow as much. Researchers also found the quieter, larger-balled monkeys lived in groups with multiple males, while the louder, smaller-balled males lived with harems of females, the Tribune reports.
Knapp tells the Tribune her "calls-and-balls paper" is the first study to show a trade off of benefits between pre-mating and post-mating. Basically a louder voice means less competition to reproduce, but bigger testicles mean more sperm and a greater chance at reproduction. “They are different solutions to the same problem,” Knapp says in the press release. While Knapp would only relate the study to humans in that women prefer deep voices and men with deep voices have more sexual partners, the Daily Dot goes further, saying the study is evidence men with small balls overcompensate when it comes to women. "I am not a scientist, but the parallels between obnoxious men who catcall, mansplain, and heckle, and these screeching simians is alarming," writes Ziwe Fumudoh. (A man quit his job to push his huge testicle across the US.)