Dryad
Published January 24, 2023 | Version v1
Dataset Open

Humpback whale adult females and calves balance acoustic contact with vocal crypsis during periods of increased separation

Creators

  • 1. University of Queensland

Description

  1. Acoustic communication is important for animals with dependent young, particularly when they are spatially separated. Maternal humpback whales (Megaptera novaeangliae) use acoustic calling to help minimise the risk of separation from their young calves during migration.
  2. These pairs also use acoustic crypsis to minimise detection by males. How they balance a restricted active space with the need to maintain acoustic contact during periods of separation is not yet understood.
  3. Here, we analysed movement metrics of tagged adult female-calf pairs during migration to identify two behavioural states, 'resting/milling' and 'travelling'. When travelling, these pairs dived synchronously and exhibited little to no spatial separation. Alternatively, adult females had significantly longer dive durations (p < 0.01) when resting, and while they spent prolonged times at depth, calves would surface several times independently. This demonstrated that these pairs are frequently separated during periods of rest.
  4. We then determined if the call rates and acoustic levels of these pairs increased with more frequent separation, finding that both adult females and calves significantly increased their call rates, but not levels, when resting.
  5. We also found that adult female-calf pairs have a restricted active space, with less than 15% of calls estimated to be detectable beyond 2 km. However, as with call level, detection distance did not differ significantly between the two behavioural states.
  6. In summary, adult female-calf pairs maintain successful communication during periods of separation by calling more frequently rather than by producing louder calls. This strategy aids in maintaining acoustic contact while simultaneously limiting detectability by conspecifics.

Notes

Please see the README document for information regarding the data spreadsheets.

Files

README.pdf

Files (12.5 MB)

Name Size Download all
md5:df0adc91b7e56ced2b1c6d30f7144f16
70.3 kB Download
md5:a3b10b3b090b9512a1d40b5baa0c5e8f
12.1 MB Download
md5:dbc77aabd2fd94c378fb06dc4b160793
25.6 kB Download
md5:05f36775e0783936df9809813a843c1a
24.0 kB Download
md5:0c8863c7140e50acdd45bf16d0f9f045
229.3 kB Preview Download