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Grey seals use anthropogenic signals from acoustic tags to locate fish: evidence from a simulated foraging task.

Stansbury AL, Götz T, Deecke VB, Janik VM - Proc. Biol. Sci. (2015)

Bottom Line: Anthropogenic noise can have negative effects on animal behaviour and physiology.During these controls, the acoustically tagged box was generally found significantly faster than the control box.Our results show that animals learn to use information provided by anthropogenic signals to enhance foraging success.

View Article: PubMed Central - PubMed

Affiliation: Sea Mammal Research Unit, School of Biology, University of St Andrews, Fife KY16 8LB, UK.

ABSTRACT
Anthropogenic noise can have negative effects on animal behaviour and physiology. However, noise is often introduced systematically and potentially provides information for navigation or prey detection. Here, we show that grey seals (Halichoerus grypus) learn to use sounds from acoustic fish tags as an indicator of food location. In 20 randomized trials each, 10 grey seals individually explored 20 foraging boxes, with one box containing a tagged fish, one containing an untagged fish and all other boxes being empty. The tagged box was found after significantly fewer non-tag box visits across trials, and seals revisited boxes containing the tag more often than any other box. The time and number of boxes needed to find both fish decreased significantly throughout consecutive trials. Two additional controls were conducted to investigate the role of the acoustic signal: (i) tags were placed in one box, with no fish present in any boxes and (ii) additional pieces of fish, inaccessible to the seal, were placed in the previously empty 18 boxes, making possible alternative chemosensory cues less reliable. During these controls, the acoustically tagged box was generally found significantly faster than the control box. Our results show that animals learn to use information provided by anthropogenic signals to enhance foraging success.

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Related in: MedlinePlus

Waveform and spectrogram display of a Vemco V9 coded fish tags, emitting an intermittent 8-pulse, 69 kHz signal (source level 151 dB SPL re 1 µPa).
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RSPB20141595F2: Waveform and spectrogram display of a Vemco V9 coded fish tags, emitting an intermittent 8-pulse, 69 kHz signal (source level 151 dB SPL re 1 µPa).

Mentions: In the learning experiment, each seal was released into the 20 box array where two pseudo-randomly chosen boxes contained a fish. During each trial, the tagged and untagged fish were placed into two separate boxes, balanced such that throughout the course of the 20 trials every location was baited once with a tagged and once with an untagged fish. One of these, the ‘tagged fish’ treatment, also contained two Vemco V9–2H coded fish tags which emitted an intermittent 69 kHz signal (source level 151 dB SPL re 1 µPa, figure 2). Each signal consisted of an 8-pulse emission unique to each tag (interval between pulses ranged from 0.25 to 0.6 s), which on average resulted in a tag signal in the pool every 13 s (s.d.: 8 s, measured over a 1 h period). To monitor the tag signal, all sessions were audio recorded using a Lumbertek TS150 hydrophone and Edirol R44 recorder (sampling rate 192 kHz, 24 bit). The other box only contained a fish without tags and did not emit any sound. The seal was free to visit and revisit the boxes in any order. When the seal retrieved the tagged fish, the tags stayed in the box and continued to emit signals until the trial ended except in 18% of all trials in which the reed switch was set to turn off one or both of the tags after the fish was retrieved. Turning off tags only occurred at the start of our experiments when we did not know how seals would react to continuing tag sounds. Once we saw no reactions to the continuing tag signals, we left tags active after fish retrieval. The trial was ended by removing the seal from the test pool, either 5 min after the seal had found both fish or after 1 h if both fish were not found. Nine seals took part in 20 of these learning trials, while one animal had only 19 trials. Each seal took part in up to eight trials per day, with successive trials being a minimum of 15 min and maximum of 48 h apart.Figure 2.


Grey seals use anthropogenic signals from acoustic tags to locate fish: evidence from a simulated foraging task.

Stansbury AL, Götz T, Deecke VB, Janik VM - Proc. Biol. Sci. (2015)

Waveform and spectrogram display of a Vemco V9 coded fish tags, emitting an intermittent 8-pulse, 69 kHz signal (source level 151 dB SPL re 1 µPa).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4262164&req=5

RSPB20141595F2: Waveform and spectrogram display of a Vemco V9 coded fish tags, emitting an intermittent 8-pulse, 69 kHz signal (source level 151 dB SPL re 1 µPa).
Mentions: In the learning experiment, each seal was released into the 20 box array where two pseudo-randomly chosen boxes contained a fish. During each trial, the tagged and untagged fish were placed into two separate boxes, balanced such that throughout the course of the 20 trials every location was baited once with a tagged and once with an untagged fish. One of these, the ‘tagged fish’ treatment, also contained two Vemco V9–2H coded fish tags which emitted an intermittent 69 kHz signal (source level 151 dB SPL re 1 µPa, figure 2). Each signal consisted of an 8-pulse emission unique to each tag (interval between pulses ranged from 0.25 to 0.6 s), which on average resulted in a tag signal in the pool every 13 s (s.d.: 8 s, measured over a 1 h period). To monitor the tag signal, all sessions were audio recorded using a Lumbertek TS150 hydrophone and Edirol R44 recorder (sampling rate 192 kHz, 24 bit). The other box only contained a fish without tags and did not emit any sound. The seal was free to visit and revisit the boxes in any order. When the seal retrieved the tagged fish, the tags stayed in the box and continued to emit signals until the trial ended except in 18% of all trials in which the reed switch was set to turn off one or both of the tags after the fish was retrieved. Turning off tags only occurred at the start of our experiments when we did not know how seals would react to continuing tag sounds. Once we saw no reactions to the continuing tag signals, we left tags active after fish retrieval. The trial was ended by removing the seal from the test pool, either 5 min after the seal had found both fish or after 1 h if both fish were not found. Nine seals took part in 20 of these learning trials, while one animal had only 19 trials. Each seal took part in up to eight trials per day, with successive trials being a minimum of 15 min and maximum of 48 h apart.Figure 2.

Bottom Line: Anthropogenic noise can have negative effects on animal behaviour and physiology.During these controls, the acoustically tagged box was generally found significantly faster than the control box.Our results show that animals learn to use information provided by anthropogenic signals to enhance foraging success.

View Article: PubMed Central - PubMed

Affiliation: Sea Mammal Research Unit, School of Biology, University of St Andrews, Fife KY16 8LB, UK.

ABSTRACT
Anthropogenic noise can have negative effects on animal behaviour and physiology. However, noise is often introduced systematically and potentially provides information for navigation or prey detection. Here, we show that grey seals (Halichoerus grypus) learn to use sounds from acoustic fish tags as an indicator of food location. In 20 randomized trials each, 10 grey seals individually explored 20 foraging boxes, with one box containing a tagged fish, one containing an untagged fish and all other boxes being empty. The tagged box was found after significantly fewer non-tag box visits across trials, and seals revisited boxes containing the tag more often than any other box. The time and number of boxes needed to find both fish decreased significantly throughout consecutive trials. Two additional controls were conducted to investigate the role of the acoustic signal: (i) tags were placed in one box, with no fish present in any boxes and (ii) additional pieces of fish, inaccessible to the seal, were placed in the previously empty 18 boxes, making possible alternative chemosensory cues less reliable. During these controls, the acoustically tagged box was generally found significantly faster than the control box. Our results show that animals learn to use information provided by anthropogenic signals to enhance foraging success.

Show MeSH
Related in: MedlinePlus