Acoustic tags show only transient behavioural effects in young grey seals

Animal-borne acoustic transmitters operating at 69 kHz appear to cause only short-lived behavioural changes in young grey seals, with no detectable effect on survival during their first year at sea, according to a study of weaned Atlantic grey seal pups published in the journal Animal Biotelemetry. The findings address a long-standing ethical concern that has limited the use of acoustic telemetry in pinnipeds: whether the tags’ ultrasonic signals, audible to the animals underwater, might disturb or harm the very individuals researchers are trying to follow.

Acoustic telemetry is widely used to remotely monitor the behaviour and survival of aquatic animals because the tags are relatively affordable, miniature and have extended battery life. Yet its use in pinnipeds has remained limited, partly because of worries about potential auditory disturbance, and the authors note that little scientific evidence has existed on this question. To fill the gap, the team equipped 130 weaned Atlantic grey seal pups (Halichoerus grypus) with satellite transmitters between 2023 and 2025, monitoring their behaviour and survival through their first year at sea, the most vulnerable life stage. Approximately half of the animals, 68 seals, were also fitted with a 69 kHz acoustic transmitter that produced a low-power signal lasting three to five seconds, with a source level of 147 dB re 1 µPa @ 1 m in water, emitted on average every 120 seconds.

Compared with the control group, the acoustically tagged seals did not show a higher probability of hauling out, a behaviour that could indicate avoidance of the acoustic signals, which were only audible to the tagged animals underwater. There was, however, one measurable difference: while at sea, the acoustically tagged seals allocated a higher proportion of their time to widespread movement than the control group, which the authors interpret as a prolonged exploration phase. That difference began to diminish by the third week at sea, suggesting the effect faded with time.

Although this behavioural difference may support the presence of sub-lethal effects, overall survival did not differ between the two groups during this sensitive life stage. Taken together, the results indicate that the effects of 69 kHz acoustic telemetry may be transient, acting primarily through early behavioural pathways. The authors caution that the underlying mechanism causing the effect of the acoustic pings on seal behaviour to attenuate remains unknown. The study suggests that animal-borne 69 kHz acoustic telemetry could be used to study grey seal ecology over long time periods, while emphasising that, as with any telemetry method, its use requires weighing scientific benefits against potential consequences.

The research was released as an early-access, peer-reviewed accepted article, citable under a permanent DOI and subject to further edits before the final version of record. For researchers considering acoustic tags for seals, the practical message is that the common 69 kHz frequency produced no detectable survival cost in this large field experiment, and the one observed behavioural difference was temporary. The authors frame the work as evidence to inform ethical assessments rather than a blanket endorsement, noting that decisions about deploying such tags should still balance the scientific value of the data against the potential consequences for the tagged animals.

Subject of Research: Effects of 69 kHz animal-borne acoustic telemetry on the behaviour and survival of young Atlantic grey seals

Article Title: Potential effects of animal-borne 69 kHz acoustic telemetry on pinniped behaviour and survival in the wild

Article References: Irani, A. I., Bordeleau, X., den Heyer, C. E., Blanchet, F. G., Flemming, J. M., Lidgard, D., Mongrain, S., Hammill, M. O., & Pelletier, F. (2026). Potential effects of animal-borne 69 kHz acoustic telemetry on pinniped behaviour and survival in the wild. Animal Biotelemetry. https://doi.org/10.1186/s40317-026-00505-w

Image Credits: AI Generated

DOI: 10.1186/s40317-026-00505-w

Keywords: acoustic telemetry, grey seals, pinnipeds, animal-borne tags, 69 kHz, biotelemetry, wildlife tracking, haul-out behaviour, first-year survival, sub-lethal effects, Halichoerus grypus, ethics