Fitness matters not size in the world of cockroach courting

In the world of cockroach courting, fitness matters much more than size – the males with the most energetic courtship displays get the female partner, rather than the big, strong ones, a new study has shown. As far as the female cockroach is concerned, the fitter the better.

Sophie L. Mowles of Anglia Ruskin University and Natalie M. Jepson from the University of Nottingham explained in the journal PLOS ONE how they investigated the courtship displays of Byrsotria fumigata – the Cuban burrowing cockroach.

In order to attract a female, the male Cuban borrowing cockroach performs a ‘wing-raising’ ritual, which involves the repeated lowering and flaring of its wings.

A courting male Cuban burrowing cockroach (Byrsotria fumigata) performing a full wing raise. As far as the female is concerned, those that can do it the most vigorously are more likely to attract her. (Image: journals.plos.org/plosone)

The most energetic wing-raisers had the greatest success

The researchers found the insects that produced the most energetic displays were much more likely to attract a female. In fact, the successful wooers performed the wing-raising on average four times more vigorously compared to their counterparts that didn’t.

They used a specially-built racetrack to measure how much energy the male cockroaches were expending during their ring-raising display to attract a mate.

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The males that had been vigorously flaring and lowering their wings in the courtship display managed lower top speeds and shorter distances on the racetrack compared to the controls (males that had not taken part), thus demonstrating that courtship used up energy and depleted cockroach stamina.

Study leader, Dr. Mowles, a Lecturer in Animal & Environmental Biology at Anglia Ruskin University’s Department of Life Sciences, said:

“This is the first time these techniques have been used to demonstrate how a dynamic, repeated courtship display can affect future performance.”

“Our experiments show that the courtship display significantly fatigues the male cockroach, and it’s the energy expended during the display, rather than other factors such as size of the male, that is used by females to inform their mating decisions.”

“Signs of male stamina are clearly important to the females, presumably as it ensures they pass good genes on to their offspring. The females will want to ensure their offspring have high physical fitness, providing them with the ability to evade predators, defeat rivals and attract females themselves.”

Courtship displays in many species often involve dynamic repetitive actions and as such, signals of stamina in courtship may be more widespread in the animal kingdom than previously thought, the authors suggest.

Citation: “Physiological Costs of Repetitive Courtship Displays in Cockroaches Handicap Locomotor Performance,” Sophie L. Mowles and Natalie M. Jepson. PLOS ONE. 25 November, 2015. DOI: 10.1371/journal.pone.0143664.