Hainan frilled treefrogs adjust spectral traits to increase competitiveness when perceiving conspecific disturbance odours

Chemical communication is regarded as the most ancient and widespread form of communication, playing a crucial role in various individual activities such as foraging, mating and defence. Nevertheless, chemical communication in anurans (i.e. frogs and toads) has received less attention, as individual decision making in male–male competition and female choice is predominantly influenced by acoustic signals. In recent years, there has been increasing evidence indicating that chemical cues can affect male–male competition behaviours in anuran species, including aggression and call activity. However, few studies have investigated whether chemical cues affect the spectral traits of acoustic signals, which are important for attracting potential mates. In the present study, we investigated variation in the dominant frequency of advertisement calls in Hainan frilled treefrogs, Kurixalus hainanus, comparing the calls of males vocalizing alone to those in the presence of conspecific odours. Our results showed that males with a higher dominant frequency significantly decreased their frequency when exposed to conspecific odours, while those with a lower frequency increased it. Further analysis revealed that the dominant frequency of advertisement calls during the stimulus period was closer to the average level than that during the spontaneous period, a trend observed only in the disturbance odour group. This adjustment may serve to maintain attractiveness to females in the face of potential predation risk. Overall, our study provides evidence that conspecific chemical cues affect the spectral traits of frog vocalizations and has an implication for understanding how males balance survival and reproduction by adjusting their calling strategies.