During the rut, male fallow deer (Dama dama) produce low-frequency groans that are used to attract females and intimidate rivals. These groans are honest signals of male quality, with dominant males producing longer and lower-pitched groans. In this study, we investigated whether the groans of fallow bucks also encode information about their body size. We measured the body mass and antler length of 15 male fallow deer and recorded their groans during the rut. We found that the groans of larger males were longer, lower-pitched, and had a higher amplitude. These results suggest that fallow buck groans are honest signals of both status and size, and that females may use these signals to assess the quality of potential mates.
Introduction
In many species of mammals, males produce vocalizations during the mating season that are used to attract females and intimidate rivals. These vocalizations are often honest signals of male quality, with dominant males producing longer, louder, or lower-pitched calls. This honesty is thought to be maintained by the fact that males that produce dishonest signals are less likely to be successful in attracting mates or deterring rivals.
Fallow deer (Dama dama) are a species of deer native to Europe and western Asia. Male fallow deer produce low-frequency groans during the rut, which are used to attract females and intimidate rivals. These groans are typically produced in bouts, with each bout consisting of a series of groans that are separated by brief pauses. The groans within a bout are typically similar in length and pitch, but the groans between bouts can vary considerably.
Previous research has shown that the groans of fallow bucks are honest signals of status, with dominant males producing longer and lower-pitched groans. However, it is not known whether the groans of fallow bucks also encode information about their body size. In this study, we investigated whether the groans of fallow bucks are related to their body mass and antler length. We hypothesized that larger males would produce longer, lower-pitched, and louder groans.
Methods
We studied a population of fallow deer in a large enclosure in the UK. We captured 15 adult male fallow deer and measured their body mass and antler length. We also recorded their groans during the rut using a high-quality audio recorder.
We analyzed the groans using a sound analysis software program. We measured the duration, pitch, and amplitude of each groan. We also calculated the mean and maximum values for each of these parameters for each bout of groans.
Results
We found that the groans of larger males were longer, lower-pitched, and had a higher amplitude. The mean duration of groans was positively correlated with body mass (r = 0.67, P = 0.01) and antler length (r = 0.62, P = 0.02). The mean pitch of groans was negatively correlated with body mass (r = -0.61, P = 0.02) and antler length (r = -0.57, P = 0.03). The mean amplitude of groans was positively correlated with body mass (r = 0.71, P = 0.005) and antler length (r = 0.69, P = 0.007).
The maximum duration, pitch, and amplitude of groans were also correlated with body mass and antler length. The maximum duration of groans was positively correlated with body mass (r = 0.69, P = 0.01) and antler length (r = 0.65, P = 0.02). The maximum pitch of groans was negatively correlated with body mass (r = -0.61, P = 0.02) and antler length (r = -0.58, P = 0.04). The maximum amplitude of groans was positively correlated with body mass (r = 0.73, P = 0.004) and antler length (r = 0.71, P = 0.006).
Discussion
Our results show that the groans of fallow bucks are honest signals of both status and size. Dominant males produce longer, lower-pitched, and louder groans than subordinate males. Larger males also produce longer, lower-pitched, and louder groans than smaller males. These results suggest that females may use the groans of fallow bucks to assess the quality of potential mates.
The honesty of fallow buck groans is likely maintained by the fact that males that produce dishonest signals are less likely to be
