title: Ascent exhalations of Antarctic fur seals: a behavioural adaptation for breath-hold diving?
abstract: Novel observations collected from video, acoustic and conductivity sensors showed that Antarctic fur seals consistently exhale during the last 50-85% of ascent from all dives (10-160 m, n > 8000 dives from 50 seals). The depth of initial bubble emission was best predicted by maximum dive depth, suggesting an underlying physical mechanism. Bubble sound intensity recorded from one seal followed predictions of a simple model based on venting expanding lung air with decreasing pressure. Comparison of air release between dives, together with lack of variation in intensity of thrusting movement during initial descent regardless of ultimate dive depth, suggested that inhaled diving lung volume was constant for all dives. The thrusting intensity in the final phase of ascent was greater for dives in which ascent exhalation began at a greater depth, suggesting an energetic cost to this behaviour, probably as a result of loss of buoyancy from reduced lung volume. These results suggest that fur seals descend with full lung air stores, and thus face the physiological consequences of pressure at depth. We suggest that these regular and predictable ascent exhalations could function to reduce the potential for a precipitous drop in blood oxygen that would result in shallow-water blackout.
authors.affiliation: Sea Mammal Research Unit, University of St Andrews, Fife KY16 8LB, UK. s.hooker@st-andrews.ac.uk
authors.forename: Sascha K
authors.initials: SK
authors.lastname: Hooker
authors.forename: Patrick J O
authors.initials: PJ
authors.lastname: Miller
authors.forename: Mark P
authors.initials: MP
authors.lastname: Johnson
authors.forename: Oliver P
authors.initials: OP
authors.lastname: Cox
authors.forename: Ian L
authors.initials: IL
authors.lastname: Boyd
mesh_terms: D000222:Adaptation, Physiological; D000818:Animals; D000864:Antarctic Regions; D004242:Diving / Q000502:physiology*; D004553:Electric Conductivity; D045853:Exhalation / Q000502:physiology*; D005260:Female; D046069:Fur Seals / Q000502:physiology*; D008124:Locomotion / Q000502:physiology; D012623:Seawater / Q000032:analysis; D012965:Sodium Chloride / Q000032:analysis; D014741:Video Recording
chemical_list: D012965:Sodium Chloride
references.citation: J Exp Biol. 2003 Oct;206(Pt 19):3405-23
references.pmid: 12939372
references.citation: J Appl Physiol. 1961 Jul;16:583-6
references.pmid: 13696183
references.citation: Science. 2000 Apr 7;288(5463):133-6
references.pmid: 10753116
references.citation: Respir Physiol. 1970 May;9(2):287-97
references.pmid: 5445189
references.citation: Science. 1985 Aug 9;229(4713):556-8
references.pmid: 4023700
references.citation: Science. 1970 Jul 3;169(3940):82-4
references.pmid: 5447537
references.citation: Am J Physiol. 1973 Sep;225(3):593-600
references.pmid: 4726492
references.citation: Science. 1969 Dec 26;166(3913):1651-4
references.pmid: 5360592
references.citation: J Appl Physiol (1985). 1963 May 01;18(3):471-477
references.pmid: 31083864
references.citation: J Comp Physiol B. 1997 Jan;167(1):9-16
references.pmid: 9051904
references.citation: Annu Rev Physiol. 1998;60:19-32
references.pmid: 9558452
references.citation: Am J Physiol. 1999 Mar;276(3):H844-57
references.pmid: 10070067
references.citation: J Exp Biol. 2002 May;205(Pt 9):1189-97
references.pmid: 11948196
references.citation: J Exp Biol. 1999 Oct;202 (Pt 20):2819-22
references.pmid: 10504317
references.citation: Am J Physiol. 1972 Nov;223(5):1016-20
references.pmid: 4654334
references.citation: Physiol Rev. 1997 Jul;77(3):837-99
references.pmid: 9234967
references.citation: Am J Physiol. 1973 Dec;225(6):1467-71
references.pmid: 4760462
references.citation: Respir Physiol. 1973 Jan;17(1):1-10
references.pmid: 4688284
references.citation: J Exp Biol. 2003 May;206(Pt 9):1461-70
references.pmid: 12654885
references.citation: J Exp Biol. 2004 May;207(Pt 11):1953-67
references.pmid: 15107448