Physiological and behavioral ecology of juvenile Weddell seals€¦ · J. WARD TESTA, MICHAEL A....
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Kooyman, G.L. 1981. Weddell seal: Consummate diver. Cambridge, United Kingdom: Cambridge University Press. Kooyman, G.L. 1989. Diverse divers. In G.L. Kooyman (Ed.), Physiolo- gy and behavior (Zoophysiology series 23). Berlin: Springer-Verlag. Kooyman, G.L., L.A. Wahrenbrock, M.A. Castellini, R.W. Davis, and E.E. Sinnett. 1980. Aerobic and anaerobic metabolism during vol- untary diving in Weddell seals: Evidence of preferred pathways from blood chemistry and behavior. Journal of Comparative Phys- iology, 138,335-346. Persson, S.G.B., L. Ekman, G. Lydin, and G. Tufuesson. 1973. Circula- tory effects of splenectomy in the horse. I. Effect on red-cell distri- bution and variability of hematocrit in the peripheral blood. Zen- tralblattfur Veterinaermedizin, 20(6), 441-455. Qvist, J., R.D. Hill, R.C. Schneider, K.J. Falke, G.C. Liggins, M. Guppy, R. Elliott, P.W. Hochachka, and W.M. Zapol. 1986. Hemoglobin concentrations and blood gas tensions of free-diving Weddell seals. Journal ofApplied Physiology, 61(4), 1560-1569. Turner, A.W., and V.E. Hodgetts. 1959. The dynamic red cell storage function of the spleen in sheep. I. Relationship to fluctuations of jugular hematocrit. Australian Journal of Experimental Biology, 37, 399-420. Wittenberg, B.A., J.B. Wittenberg, and P.R.B. Caldwell. 1975. Role of myoglobin in the oxygen supply to red skeletal muscle. Journal of Biological Chemistry, 250(23), 9038-9043. Physiological and behavioral ecology of juvenile Weddell seals J. WARD TESTA, MICHAEL A. CASTELLINI, and LORRIE D. REA, Institute of Marine Science, University ofAlaska, Fairbanks, Alaska 99775-1080 T he long-term emphasis of this project has been the under- standing of mechanisms and causes of population change in seals and other large mammals. In recent years, the fate of juvenile animals has surfaced as a key factor to be understood in relation to declining pinniped populations in the Northern Hemisphere. This project attempts to integrate information on the physiological and behavioral development of juvenile Weddell seals in relation to their ecology and survival. It was motivated, in part, by the need for comparative studies to similar work being conducted by our laboratories on North - ern Hemisphere pinnipeds that are showing significant popu- lation declines. In 1992, we continued population studies of Weddell seals in Erebus Bay and McMurdo Sound (77 045'S 166030'E). The adult population was estimated at 258 [standard error (SE)=171 males and 595 (SE=8) females, a population that was somewhat smaller than in the previous two seasons (Matsuki and Testa 1991; Schreer and Testa 1992). Such changes can result from interannual variation in population size or sighta- bility in a given year (Testa and Siniff 1987). Pup production, however, was only 349 pups, compared to the range of 390-440 over the last 10 years. Pup mortality was also higher (9 percent) than normal (5 percent; Thomas and DeMaster 1983). This decline in reproduction continues to follow a pat- tern of lower reproduction during El Niño—Southern Oscilla- tion (ENSO) events reported by Testa et al. (1991). Necropsies were performed and assessment of the causes of pup mortali- ty will be reported elsewhere. Our work on Weddell seal physiology was divided into two major sections: development of diving physiology and nutritional physiology. In both cases, we took measurements from over 20 pups from soon after birth in October until the pups dispersed in February. We investigated several compo- nents of the development of diving physiology, including changes in oxygen-carrying capacity in the blood as moni- tored by the relative number of red blood cells [hematocrit (Hct)] and the concentration of hemoglobin (Hb) in whole blood. We found that Weddell pups followed normal patterns of mammalian development: they had high Hct immediately after birth, a period of decline for several weeks, and then a slow increase up to juvenile levels. This pattern is unlike that seen in another excellent pinniped diver, the elephant seal (Mirounga angustirostris), whose Hct levels are high immedi- ately after birth and then continue to increase without a peri- od of postnatal decline (Castellini, Castellini, and Kretzmann 1990). We are testing whether the pattern of Hct and Hb changes correlates with changes in diving and breath-hold activity. We also began work on development of apnea pat- terns and heart-rate changes that occur during development, but most of that work will be conducted during the 1993-1994 season. Finally, we conducted a series of experi - ments looking at development of pressure tolerance in blood cells. These tests examined the metabolic rate of red blood cells under pressures simulating deep dives. Weddell seal cells showed small changes with pressure, and these tests are now being conducted on terrestrial mammals for compar- isons. Nutritional studies were conducted on many of the same pups to determine when Weddell seal pups become nutri- tionally independent from their mothers. There were four major objectives. First, we monitored the growth of pups (length, girth, weight) to follow changes in body condition during the nursing period and afterward. We are conducting identical work on other pinniped species to look at compara- tive patterns. Second, we followed the hydration state of the animals to check for alterations in body water that may occur at the point of weaning. Third, we used a series of blood chemistries that react to feeding and fasting states to test for nutritional status. All of these tests have been utilized by our laboratory on other pinnipeds and usually indicate whether animals are fed, fasting, or starving (Castellini and Rea 1992). Preliminary results suggest that Weddell seal pups undergo ANTARCTIC JOURNAL - REVIEW 1993 155
Transcript of Physiological and behavioral ecology of juvenile Weddell seals€¦ · J. WARD TESTA, MICHAEL A....
Kooyman, G.L. 1981. Weddell seal: Consummate diver. Cambridge,United Kingdom: Cambridge University Press.
Kooyman, G.L. 1989. Diverse divers. In G.L. Kooyman (Ed.), Physiolo-gy and behavior (Zoophysiology series 23). Berlin: Springer-Verlag.
Kooyman, G.L., L.A. Wahrenbrock, M.A. Castellini, R.W. Davis, andE.E. Sinnett. 1980. Aerobic and anaerobic metabolism during vol-untary diving in Weddell seals: Evidence of preferred pathwaysfrom blood chemistry and behavior. Journal of Comparative Phys-iology, 138,335-346.
Persson, S.G.B., L. Ekman, G. Lydin, and G. Tufuesson. 1973. Circula-tory effects of splenectomy in the horse. I. Effect on red-cell distri-bution and variability of hematocrit in the peripheral blood. Zen-
tralblattfur Veterinaermedizin, 20(6), 441-455.Qvist, J., R.D. Hill, R.C. Schneider, K.J. Falke, G.C. Liggins, M. Guppy,
R. Elliott, P.W. Hochachka, and W.M. Zapol. 1986. Hemoglobinconcentrations and blood gas tensions of free-diving Weddellseals. Journal ofApplied Physiology, 61(4), 1560-1569.
Turner, A.W., and V.E. Hodgetts. 1959. The dynamic red cell storagefunction of the spleen in sheep. I. Relationship to fluctuations ofjugular hematocrit. Australian Journal of Experimental Biology, 37,399-420.
Wittenberg, B.A., J.B. Wittenberg, and P.R.B. Caldwell. 1975. Role ofmyoglobin in the oxygen supply to red skeletal muscle. Journal ofBiological Chemistry, 250(23), 9038-9043.
Physiological and behavioral ecology of juvenile Weddell sealsJ. WARD TESTA, MICHAEL A. CASTELLINI, and LORRIE D. REA, Institute of Marine Science,
University ofAlaska, Fairbanks, Alaska 99775-1080
The long-term emphasis of this project has been the under-standing of mechanisms and causes of population change
in seals and other large mammals. In recent years, the fate ofjuvenile animals has surfaced as a key factor to be understoodin relation to declining pinniped populations in the NorthernHemisphere. This project attempts to integrate informationon the physiological and behavioral development of juvenileWeddell seals in relation to their ecology and survival. It wasmotivated, in part, by the need for comparative studies tosimilar work being conducted by our laboratories on North -ern Hemisphere pinnipeds that are showing significant popu-lation declines.
In 1992, we continued population studies of Weddellseals in Erebus Bay and McMurdo Sound (77 045'S 166030'E).The adult population was estimated at 258 [standard error(SE)=171 males and 595 (SE=8) females, a population that wassomewhat smaller than in the previous two seasons (Matsukiand Testa 1991; Schreer and Testa 1992). Such changes canresult from interannual variation in population size or sighta-bility in a given year (Testa and Siniff 1987). Pup production,however, was only 349 pups, compared to the range of390-440 over the last 10 years. Pup mortality was also higher(9 percent) than normal (5 percent; Thomas and DeMaster1983). This decline in reproduction continues to follow a pat-tern of lower reproduction during El Niño—Southern Oscilla-tion (ENSO) events reported by Testa et al. (1991). Necropsieswere performed and assessment of the causes of pup mortali-ty will be reported elsewhere.
Our work on Weddell seal physiology was divided intotwo major sections: development of diving physiology andnutritional physiology. In both cases, we took measurementsfrom over 20 pups from soon after birth in October until thepups dispersed in February. We investigated several compo-nents of the development of diving physiology, includingchanges in oxygen-carrying capacity in the blood as moni-tored by the relative number of red blood cells [hematocrit
(Hct)] and the concentration of hemoglobin (Hb) in wholeblood. We found that Weddell pups followed normal patternsof mammalian development: they had high Hct immediatelyafter birth, a period of decline for several weeks, and then aslow increase up to juvenile levels. This pattern is unlike thatseen in another excellent pinniped diver, the elephant seal(Mirounga angustirostris), whose Hct levels are high immedi-ately after birth and then continue to increase without a peri-od of postnatal decline (Castellini, Castellini, and Kretzmann1990). We are testing whether the pattern of Hct and Hbchanges correlates with changes in diving and breath-holdactivity. We also began work on development of apnea pat-terns and heart-rate changes that occur during development,but most of that work will be conducted during the1993-1994 season. Finally, we conducted a series of experi -ments looking at development of pressure tolerance in bloodcells. These tests examined the metabolic rate of red bloodcells under pressures simulating deep dives. Weddell sealcells showed small changes with pressure, and these tests arenow being conducted on terrestrial mammals for compar-isons.
Nutritional studies were conducted on many of the samepups to determine when Weddell seal pups become nutri-tionally independent from their mothers. There were fourmajor objectives. First, we monitored the growth of pups(length, girth, weight) to follow changes in body conditionduring the nursing period and afterward. We are conductingidentical work on other pinniped species to look at compara-tive patterns. Second, we followed the hydration state of theanimals to check for alterations in body water that may occurat the point of weaning. Third, we used a series of bloodchemistries that react to feeding and fasting states to test fornutritional status. All of these tests have been utilized by ourlaboratory on other pinnipeds and usually indicate whetheranimals are fed, fasting, or starving (Castellini and Rea 1992).Preliminary results suggest that Weddell seal pups undergo
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several days of fasting after they are weaned. Finally, we fol-lowed general veterinary blood examination procedures on allseal pups to look for obvious changes in blood condition thatmight indicate stress, disease, or metabolic alterations thatoccurred either over time or in various groups of seals.
Time-depth recorders (TDRs) and satellite-linked TDRs(SLTDRs) were employed to study the diving behavior of bothpups and yearlings in McMurdo Sound. Preliminary resultsindicate that pup diving capabilities developed rapidly afterweaning at 6 weeks of age, and within a few weeks, pups werecapable of reaching the same depths as yearlings. Overwintermovements and diving behavior of pups have been moni-tored since January 1993 through the Argos data-collectionand location system.
We thank Ama! Ajmi, John Blake, Stephen Lewis, andBrad Scotton for field assistance from 5 October to 20 Decem-ber 1992, and Brian Fadely and Kate Wynne for their assis-tance from 1 January to 12 February 1993. This work was sup-ported by National Science Foundation grant OPP 91-19885.
References
Castellini, J.M., M.A. Castellini, and M.B. Kretzmann. 1990. Circulato-ry water balance in suckling and fasting northern elephant sealpups. Journal of Comparative Physiology, 160(B), 537-542.
Castellini, M.A., and L.D. Rea. 1992. The biochemistry of natural fast-ing at its limits. Experientia, 48(6), 575-582.
Matsuki, M., and J.W. Testa. 1991. Population ecology and satellitetelemetry of Weddell seals (Leptonychotes weddellii) in McMurdoSound. Antarctic Journal of the U.S., 26(5), 185-186.
Schreer, J.F., and J.W. Testa. 1992. Population ecology of Weddellseals in McMurdo Sound. Antarctic Journal of the U.S., 27(5), 152.
Testa, J.W., and D.B. Siniff. 1987. Population dynamics of Weddellseals (Leptonychotes weddelli) in McMurdo Sound, Antarctica.Ecological Monographs, 57(2), 149-165.
Testa, J.W., G. Oehlert, D. Ainley, J.L. Bengtson, D.B. Siniff, R.M. Laws,and D.R. Rounsevell. 1991. Temporal variability in antarctic marineecosystems: Periodic fluctuations in the phocid seals. CanadianJournal of Fisheries and Aquatic Sciences, 48(4), 631-639.
Thomas, J.A., and D.P. DeMaster. 1983. Parameters affecting survivalof Weddell seal (Leptonychotes weddelli) pups to weaning. Canadi-an Journal of Zoology, 61, 2078-2083.
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