Continuous, deep diving in female northern elephant seals, Mirounga angustirostris

The free-ranging dive pattern of seven adult female northern elephant seals (Mirounga angustirostris) was obtained with time–depth recorders during the first 14 – 27 days at sea following lactation. The instruments were recovered and mass gain at sea determined when the animals returned to the rookery at Año Nuevo, California, to molt. The seals gained a mean of 76.5 ± 13.9 kg during a mean of 72.6 ± 5.0 days at sea. The mean dive rate was 2.7 ± 0.2 dives/h and diving was virtually continuous during the entire period at sea. Mean dive duration was 19.2 ± 4.3 min with the longest submersion lasting 48 min. Mean surface interval between dives was 2.8 ± 0.5 min, so that only 14.4% of the recorded time at sea was spent on the surface. Surface intervals did not vary with the duration of preceding or succeeding dives. Modal dive depth for each female was between 350 and 650 m. The maximum dive depth was estimated at 894 m, a depth record for pinnipeds. The deep, nearly continuous dive pattern of female northern elephant seals differs from the dive pattern of other pinnipeds and appears to serve in foraging, energy conservation, and predator avoidance.

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Prolonged, continuous, deep diving by northern elephant seals

Canadian Journal of Zoology ◽

10.1139/z89-355 ◽

1989 ◽

Vol 67 (10) ◽

pp. 2514-2519 ◽

Cited By ~ 68

Author(s):

Burney J. Le Boeuf ◽

Yasuhiko Naito ◽

Anthony C. Huntley ◽

Tomohiro Asaga

Keyword(s):

Dive Depth ◽

Dive Duration ◽

Mirounga Angustirostris ◽

Steady State Condition ◽

Elephant Seals ◽

Deep Diving ◽

Physiological Processes ◽

Northern Elephant Seals ◽

Extended Surface ◽

The Mean

An earlier study showed that female northern elephant seals (Mirounga angustirostris) dive deeply and continuously during the first 1–3 weeks at sea following lactation. We report that this dive pattern is maintained for the entire 2½-month period at sea. Time–depth recorders were attached to six adult females at Año Nuevo, California; three instruments recorded continuously and three instruments recorded every 3rd day at sea. The mean dive rate was 2.5–3.3 dives per hour, with a mean of < 3.5 min on the surface between dives. This resulted in females spending 83–90% of the time at sea underwater. Interruption of continuous diving, characterized by extended surface intervals with a mean of 51.9 ± 65.5 min, was rare, following only 0.42% of the dives. Modal dive duration per female was in the range 17.1–22.5 min. The longest dive was 62 min and was followed by a surface interval of < 2.6 min. Modal dive depth per female was in the range 500–700 m; three females had dives that exceeded 1000 m, with the deepest dive estimated at 1250 m. Deep diving to 500 m or more was always preceded by a descending-staircase pattern of initially shallow to increasingly deeper dives. The continuous, deep diving pattern of this pelagic seal is evidently a steady-state condition. This has important implications for understanding diving adaptations and the physiological processes underlying them.

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Heart rates and abdominal temperatures of free-ranging South Georgian shags, Phalacrocorax georgianus

Journal of Experimental Biology ◽

10.1242/jeb.200.4.661 ◽

1997 ◽

Vol 200 (4) ◽

pp. 661-675 ◽

Cited By ~ 12

Author(s):

R M Bevan ◽

I L Boyd ◽

P J Butler ◽

K Reid ◽

A J Woakes ◽

...

Keyword(s):

Heart Rate ◽

Dive Depth ◽

Dive Duration ◽

Diving Behaviour ◽

The South ◽

Data Logger ◽

Heart Rates ◽

The Mean ◽

Free Ranging ◽

Mean Heart Rate

The South Georgian shag (Phalacrocorax georgianus) shows a remarkable diving ability comparable to that of penguins, yet nothing is known of the physiology of these birds. In this study, heart rates and abdominal temperatures were recorded continuously in four free-ranging South Georgian shags using an implanted data-logger. A timedepth recorder was also attached to the back of the implanted birds to record their diving behaviour. The diving behaviour of the birds was essentially similar to that reported in other studies, with maximum dive durations for individual birds ranging between 140 and 287 s, and maximum depths between 35 and 101 m. The birds, while at the nest, had a heart rate of 104.0±13.1 beats min-1 (mean ± s.e.m.) and an abdominal temperature of 39.1±0.2 °C. During flights of 221±29 s, heart rate and abdominal temperature rose to 309.5±18.0 beats min-1 and 40.1±0.3 °C, respectively. The mean heart rate during diving, at 103.7±13.7 beats min-1, was not significantly different from the resting values, but the minimum heart rate during a dive was significantly lower at 64.8±5.8 beats min-1. The minimum heart rate during a dive was negatively correlated with both dive duration and dive depth. Abdominal temperature fell progressively during a diving bout, with a mean temperature at the end of a bout of 35.1±1.7 °C. The minimum heart rate during diving is at a sub-resting level, which suggests that the South Georgian shag responds to submersion with the 'classic' dive response of bradycardia and the associated peripheral vasoconstriction and utilisation of anaerobic metabolism. However, the reduction in abdominal temperature may reflect a reduction in the overall metabolic rate of the animal such that the bird can remain aerobic while submerged.

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Heart rates of northern elephant seals diving at sea and resting on the beach.

Journal of Experimental Biology ◽

10.1242/jeb.200.15.2083 ◽

1997 ◽

Vol 200 (15) ◽

pp. 2083-2095 ◽

Cited By ~ 25

Author(s):

R D Andrews ◽

D R Jones ◽

J D Williams ◽

P H Thorson ◽

G W Oliver ◽

...

Keyword(s):

Heart Rate ◽

Dive Depth ◽

Dive Duration ◽

Cardiac Response ◽

Elephant Seals ◽

Heart Rates ◽

Data Loggers ◽

Long Duration ◽

Northern Elephant Seals ◽

Instantaneous Heart Rate

Heart rates of northern elephant seals diving at sea and during apnoea on land were monitored to test whether a cardiac response to submergence is an important factor in their ability to make repetitive, long-duration dives. Seven juvenile northern elephant seals were captured at Año Nuevo, CA, instrumented and translocated to release sites around Monterey Bay. Heart rate and dive depth were recorded using custom-designed data loggers and analogue tape monitors during the seals' return to Año Nuevo. Heart rates during apnoea and eupnoea were recorded from four of the seals after they hauled out on the beach. Diving patterns were very similar to those of naturally migrating juveniles. The heart rate response to apnoea at sea and on land was a prompt bradycardia, but only at sea was there an anticipatory tachycardia before breathing commenced. Heart rate at sea declined by 64% from the surface rate of 107 +/- 3 beats min-1 (mean +/- S.D.), while heart rate on land declined by 31% from the eupnoeic rate of 65 +/- 8 beats min-1. Diving heart rate was inversely related to dive duration in a non-linear fashion best described by a continuous, curvilinear model, while heart rate during apnoea on land was independent of the duration of apnoea. Occasionally, instantaneous heart rate fell as low as 3 beats min-1 during diving. Although bradycardia occurs in response to apnoea both at sea and on land, only at sea is heart rate apparently regulated to minimise eupnoeic time and to ration oxygen stores to ensure adequate supplies for the heart and brain not only as the dive progresses normally but also when a dive is abnormally extended.

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Oxygen minimum zone: An important oceanographic habitat for deep-diving northern elephant seals, Mirounga angustirostris

Ecology and Evolution ◽

10.1002/ece3.3202 ◽

2017 ◽

Vol 7 (16) ◽

pp. 6259-6270 ◽

Cited By ~ 10

Author(s):

Yasuhiko Naito ◽

Daniel P. Costa ◽

Taiki Adachi ◽

Patrick W. Robinson ◽

Sarah H. Peterson ◽

...

Keyword(s):

Oxygen Minimum Zone ◽

Mirounga Angustirostris ◽

Elephant Seals ◽

Deep Diving ◽

Northern Elephant Seals ◽

Minimum Zone ◽

Oxygen Minimum

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Maternal aggression in northern elephant seals: the effect of the pup

Canadian Journal of Zoology ◽

10.1139/z88-244 ◽

1988 ◽

Vol 66 (7) ◽

pp. 1693-1698 ◽

Cited By ~ 7

Author(s):

Christine A. Ribic

Keyword(s):

Mirounga Angustirostris ◽

Maternal Aggression ◽

Arrival Date ◽

Elephant Seals ◽

Aggressive Encounter ◽

Early Arrival ◽

Northern Elephant Seals ◽

The Mean ◽

Breeding Seasons

Female northern elephant seals (Mirounga angustirostris) were observed for three breeding seasons on Southeast Farallon Island to determine the effect of the pup on maternal aggression. For females that lost their pups before weaning them, the mean percentage of aggressive encounters started and won decreased after the death of the pup. A higher percentage of females moved away at the end of an aggressive encounter from females that ultimately weaned their pups than from females that ultimately lost their pups. There was, however, no difference between the two categories in mean percentage of aggressive encounters started and won. Among females that weaned pups in all three seasons, individuals did not win more encounters but differed in percentage of females that moved away and in mean percentage of aggressive encounters started as they aged. A number of variables were associated with an increased probability that a female would successfully wean her pup: early arrival date, having a high percentage of females that moved away, and a high mean percentage of aggressive encounters won. Raising a pup in an area of high female density or where animals had access to the beach were associated with a decreased probability of weaning a pup.

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Foraging and fasting can influence contaminant concentrations in animals: an example with mercury contamination in a free-ranging marine mammal

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2017.2782 ◽

2018 ◽

Vol 285 (1872) ◽

pp. 20172782 ◽

Cited By ~ 7

Author(s):

Sarah H. Peterson ◽

Joshua T. Ackerman ◽

Daniel E. Crocker ◽

Daniel P. Costa

Keyword(s):

Life History ◽

Mercury Contamination ◽

Mirounga Angustirostris ◽

Elephant Seals ◽

Northern Elephant Seals ◽

Large Fluctuations ◽

Before And After ◽

Blood Mercury ◽

Annual Life History ◽

Free Ranging

Large fluctuations in animal body mass in relation to life-history events can influence contaminant concentrations and toxicological risk. We quantified mercury concentrations in adult northern elephant seals ( Mirounga angustirostris ) before and after lengthy at sea foraging trips ( n = 89) or fasting periods on land ( n = 27), and showed that mercury concentrations in blood and muscle changed in response to these events. The highest blood mercury concentrations were observed after the breeding fast, whereas the highest muscle mercury concentrations were observed when seals returned to land to moult. Mean female blood mercury concentrations decreased by 30% across each of the two annual foraging trips, demonstrating a foraging-associated dilution of mercury concentrations as seals gained mass. Blood mercury concentrations increased by 103% and 24% across the breeding and moulting fasts, respectively, demonstrating a fasting-associated concentration of mercury as seals lost mass. In contrast to blood, mercury concentrations in female's muscle increased by 19% during the post-breeding foraging trip and did not change during the post-moulting foraging trip. While fasting, female muscle mercury concentrations increased 26% during breeding, but decreased 14% during moulting. Consequently, regardless of exposure, an animal's contaminant concentration can be markedly influenced by their annual life-history events.

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Extreme hypoxemic tolerance and blood oxygen depletion in diving elephant seals

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.00247.2009 ◽

2009 ◽

Vol 297 (4) ◽

pp. R927-R939 ◽

Cited By ~ 68

Author(s):

Jessica U. Meir ◽

Cory D. Champagne ◽

Daniel P. Costa ◽

Cassondra L. Williams ◽

Paul J. Ponganis

Keyword(s):

Metabolic Rate ◽

Resting Metabolic Rate ◽

Oxygen Depletion ◽

Dive Duration ◽

Aerobic Metabolism ◽

Mirounga Angustirostris ◽

Dissociation Curve ◽

Elephant Seals ◽

Store Depletion ◽

Northern Elephant Seals

Species that maintain aerobic metabolism when the oxygen (O2) supply is limited represent ideal models to examine the mechanisms underlying tolerance to hypoxia. The repetitive, long dives of northern elephant seals ( Mirounga angustirostris) have remained a physiological enigma as O2 stores appear inadequate to maintain aerobic metabolism. We evaluated hypoxemic tolerance and blood O2 depletion by 1) measuring arterial and venous O2 partial pressure (Po2) during dives with a Po2/temperature recorder on elephant seals, 2) characterizing the O2-hemoglobin (O2-Hb) dissociation curve of this species, 3) applying the dissociation curve to Po2 profiles to obtain %Hb saturation (So2), and 4) calculating blood O2 store depletion during diving. Optimization of O2 stores was achieved by high venous O2 loading and almost complete depletion of blood O2 stores during dives, with net O2 content depletion values up to 91% (arterial) and 100% (venous). In routine dives (>10 min) PvO2 and PaO2 values reached 2–10 and 12–23 mmHg, respectively. This corresponds to So2 of 1–26% and O2 contents of 0.3 (venous) and 2.7 ml O2/dl blood (arterial), demonstrating remarkable hypoxemic tolerance as PaO2 is nearly equivalent to the arterial hypoxemic threshold of seals. The contribution of the blood O2 store alone to metabolic rate was nearly equivalent to resting metabolic rate, and mean temperature remained near 37°C. These data suggest that elephant seals routinely tolerate extreme hypoxemia during dives to completely utilize the blood O2 store and maximize aerobic dive duration.

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Respiration and heart rate at the surface between dives in northern elephant seals

Journal of Experimental Biology ◽

10.1242/jeb.203.21.3265 ◽

2000 ◽

Vol 203 (21) ◽

pp. 3265-3274 ◽

Cited By ~ 8

Author(s):

B.J. Le Boeuf ◽

D.E. Crocker ◽

J. Grayson ◽

J. Gedamke ◽

P.M. Webb ◽

...

Keyword(s):

Heart Rate ◽

Mirounga Angustirostris ◽

Digital Audio ◽

Adult Males ◽

Elephant Seals ◽

Diving Depth ◽

Surface Time ◽

Northern Elephant Seals ◽

Audio Tape Recorder ◽

Free Ranging

All underwater activities of diving mammals are constrained by the need for surface gas exchange. Our aim was to measure respiratory rate (fb) and heart rate (fh) at the surface between dives in free-ranging northern elephant seals Mirounga angustirostris. We recorded fb and fh acoustically in six translocated juveniles, 1.8-2. 4 years old, and three migrating adult males from the rookery at Ano Nuevo, California, USA. To each seal, we attached a diving instrument to record the diving pattern, a satellite tag to track movements and location, a digital audio tape recorder or acoustic datalogger with an external hydrophone to record the sounds of respiration and fh at the surface, and a VHF transmitter to facilitate recovery. During surface intervals averaging 2.2+/−0.4 min, adult males breathed a mean of 32.7+/−5.4 times at a rate of 15. 3+/−1.8 breaths min(−)(1) (means +/− s.d., N=57). Mean fh at the surface was 84+/−3 beats min(−)(1). The fb of juveniles was 26 % faster than that of adult males, averaging 19.2+/−2.2 breaths min(−)(1) for a mean total of 41.2+/−5.0 breaths during surface intervals lasting 2.6+/−0.31 min. Mean fh at the surface was 106+/−3 beats min(−)(1). fb and fh did not change significantly over the course of surface intervals. Surface fb and fh were not clearly associated with levels of exertion, such as rapid horizontal transit or apparent foraging, or with measures of immediately previous or subsequent diving performance, such as diving duration, diving depth or swimming speed. Together, surface respiration rate and the duration of the preceding dive were significant predictors of surface interval duration. This implies that elephant seals minimize surface time spent loading oxygen depending on rates of oxygen uptake and previous depletion of stores.

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Drift diving in female northern elephant seals: implications for food processing

Canadian Journal of Zoology ◽

10.1139/z97-004 ◽

1997 ◽

Vol 75 (1) ◽

pp. 27-39 ◽

Cited By ~ 102

Author(s):

Daniel E. Crocker ◽

Burney J. Le Boeuf ◽

Daniel P. Costa

Keyword(s):

Body Fat ◽

Average Rate ◽

Metabolic Cost ◽

Late Gestation ◽

Mirounga Angustirostris ◽

Elephant Seals ◽

Northern Elephant Seals ◽

Before And After ◽

Free Ranging ◽

Active Swimming

We tested predictions from the hypothesis that northern elephant seals, Mirounga angustirostris, drift during the bottom segment of some dives (called C dives) using oxygen saved from reduced locomotion to process food. Sixteen free-ranging dive records were obtained with microcomputer dive recorders attached to 13 adult females from Año Nuevo, California, during biannual foraging trips when they were in early or late stages of gestation; swim speed was recorded throughout one dive record. Body composition was measured before and after trips to sea. C dives with a bout length of 2 – 10 dives and a mean duration similar to those of other dive types made up 6.3 ± 1.9% of the dives recorded. Swim speed was near or below the recorder stall speed (0.22 m/s) during the second, drift segment of these dives. The rate of vertical depth change while drifting varied little within bouts, was initially significantly correlated with the ratio of fat to lean body mass at departure, and changed systematically as the seals fed while at sea. Females in early gestation, with initial mean body fat of 24%, drifted down at a mean rate of 0.31 ± 0.04 m/s; females in late gestation, with mean body fat approaching 36%, drifted up at an average rate of 0.17 ± 0.05 m/s. The frequency, duration, and temporal pattern of drift dives were correlated with foraging behavior, supporting the hypothesis that drifting while diving is associated with the metabolic cost of processing food. This study provides indirect support for the hypothesis that elephant seals suspend active swimming on certain dives, during which a greater proportion of oxygen stores is allocated to the processing of food, without interrupting the seals' normal pattern of continuous diving and allowing them to remain within their aerobic dive limit.

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