Dishonest signals give misleading information about an animal’s size, intention, and quality. In animal communication, dishonest signals are maintained if they are rarely made or used in aggressive contests. However, when dishonest signals are commonly used in a population, they are theoretically challenging to explain. In the Pavi cristatus peafowl, male peacocks perform specialized copulation calls without the presence of females, while the males are clearly not attempting to copulate. Since the solo hoots are made when females are out of view, they may be considered dishonest signals of male mating attempts. Dakin and Mongomerie (2014) hope to elucidate the functions of the hoot call in both males and females by using field observations and experimental playback to test the functions of a potentially deceptive call.
Dakin and Mongomerie (2014) observed peacock behavior in four different zoos between 2007 and 2010, including the Assiniboine Park Zoo, the Toronto Zoo, the Los Angeles Arboretum, and the Bronx Zoo. They observed peacocks during their lekking periods. Lekking is a term that refers to male peacocks assembling and engaging in competitive displays of their feathers. Dakin and Mongomerie (2014) recorded the interactions of male peacocks during their displays and all of their hoot calls. Additionally, to determine whether the hoot call is a signal of mating success in males, the copulation attempts, successful copulations, and both attempt hoots and solo hoots were documented. Next, a playback experiment was used to determine whether a hoot call would attract females independent of male behavior. Three different calls were used: the hoot call, the keow, and the ka. The keow is given by males when their trains are not erect, while the ka call is given by males that are displaying their trains or are beginning to do so when females are not present.
The results from their field observations demonstrated that only 31% of the hoots were solo hoots that were generally given by males with erect trains when they were not attempting to copulate with a female. Males were almost never solo hooting when females were nearby, for only 3 out of 80 solo hoots were given in the presence of females. Interestingly, after comparing female visitation statuses before and after solo hooting, Dakin and Mongomerie (2014) found that males were more likely to attract at least one female visitor following a solo hoot than the immediately preceding period. Playback experiments confirmed their results from the field observations. Playback calls of the solo hoot had significantly more females approach the speaker after the playback than before (Figure 1).
Peacocks use the hoot call when attempting to copulate, and these calls can be heard at a distance and thus signals to other individuals that a male has attempted to copulate with another female visitor. The authors argue that solo hoots, on the other hand, are a form of deception due to three reasons: (i) females are rarely in view when males give solo hoot calls, (ii) the hoot generally indicates a copulation attempt has taken place, and (iii) although total number of hoot calls are related to male mating success, solo hoots are dishonest in this context.
The results on the hoot calls of the peacock are still preliminary, and future research is necessary to follow-up on many of the authors’ observations. For instance, a large percentage of males in this study were never seen solo hooting, and the authors attribute this observation to operant conditioning. If hoot calls encourage females to visit and this experience is rewarding to males, then solo hooting may be a reinforced behavior resulting from previous experiences. Additionally, the trade offs to responding to a dishonest signal have not yet been explored in female peacock populations.
This study advances our knowledge of the acquisition of dishonest signals and proposes reward-based learning as a mechanism for utilizing deceptive calls. Peacocks may be able to learn new behaviors based off previous experiences and apply these new behaviors to increase their likelihood to mate. Furthermore, peacocks can pose new questions about the maintenance of dishonest signals, since dishonest signals are commonly used in peacock populations but without the presence of females. I’m curious about how these behaviors are passed on from different generations and whether paternal peacocks will teach their offspring these deceptive signals to increase their fitness.
Dakin, R., Montgomerie, R. (2014). Deceptive copulation calls attract female visitors to peacock leks. The American Naturalist DOI: 10.1086/675393