High-frequency hearing sensitivity does not systematically imply aversion to ultrasounds in large terrestrial mammals

ABSTRACT

Crop damage and vehicle collisions caused by wild ungulates require effective deterrents. Many commercial acoustic devices use ultrasonic signals, presenting them as aversive to these animals. However, unconvincing results reported in previous studies using (non-frequency modulated) ultrasounds bring their effectiveness as deterrent signals into question. Here, we explored the deterrent effectiveness of ultrasounds in several large mammalian species that are expected to perceive these high frequencies. Specifically, we tested the effect of different ultrasonic signals on red deer, peccaries, and wolves. Animals were exposed to sequences of nine acoustic signals in the 20–30 kHz frequency range, and to a lower-pitched signal (2–3 kHz). While red deer showed no aversion to ultrasonic signals (inaudible for humans), lower frequency (audible for humans) modulations increased aversive responses. Conversely, peccaries showed strong flight responses to several ultrasonic signals. Wolves also reacted to ultrasounds but did not flee. Our study confirms that ultrasonic signals are not suitable for deterring European red deer. However, our results suggest that their effectiveness in other species should be systematically tested, without assuming that their hearing frequency range is a reliable predictor of their behavioural responses to ultrasonic signals.

KEYWORDS:

• Wildlife – vehicle collisions
• acoustic deterrence
• ultrasounds
• red deer
• peccary
• wolf

Acknowledgements

A special thanks to Christophe Audureau and Charly Binaud, from the zoological reserve of La Haute-Touche, who contributed to field work. We thank Léo Papet and Léo Perrier who provided technical support, Nicolas Boyer who build the playback devices, and Florian Eneau for second-coding the behavioural responses.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Author contributions

AT, DR, and YL conceived the idea. AT created acoustic signals and analysed animal behaviours. AT and CV conducted the playback experiments. AT and LP analysed the data. AT and DR wrote the original draft of the paper and led the revisions, and all authors critically reviewed several versions of the manuscript.

Ethical statement

The experiment was conducted under the zoological reserve of La Haute-Touche’s experimental Agreement n° 36145002. The animals were never restrained while the sound was being sent and the enclosures were chosen so that they always had the opportunity to avoid the signal.

Additional information

Funding

AT and this work, including experimental costs, were funded by the French railway company SNCF, and the ANRT under the contract number CIFRE 2021-0011. This PhD is co-managed by Claire Chaufour and Yannick Matillon (SNCF VOYAGEURS), Anne Petit (SNCF RESEAU) and Patryk Dec (SNCF). DR was also supported by a grant from the French National Research Agency (’SCREAM’, ANR-21-CE28-0007-01). NM and DR were also supported by the Institut universitaire de France and LP by Pôle emploi.