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Body composition and energy metabolism of moulting eudyptid penguins
Comp.Biochem. Phgsiul.. 1911,
Vol.
56A. pp. 27 ro 30. Pergamon
Press.
BODY COMPOSITION OF MOULTING A. J. Fitzpatrick
WILLIAMS,
W. R.
Printed in GrealBritain
AND ENERGY METABOLISM EUDYPTID PENGUINS
SIEGFRIED, A.
E.
BURGER AND
A.
BERRUTI
Institute, University of Cape Town, Rondebosch 7700, South Africa (Receioed
11 March
1976)
Abstract-l.
Penguins fast during the annual moult. Moulting macaroni penguins, Eudyptes chrysolopenguins, E. chrysocome, were analysed for protein, fat and water content. 2. Fat reserves declined by 38 g/day and were exhausted after 34 days in macaroni penguins. In rockhopper penguins fat reserves declined by 33 g/day and were exhausted after 28 days. 3. Energy consumption of moulting macaroni and rockhopper penguins was 387 kcal/day and 338 kcal/day respectively. 4. Macaroni and rockhopper penguins would need to consume about 16 kg and 11 kg of crustaceans respectively in order to accumulate sufficient food reserves for moulting.
phus, and rockhopper
of integument and carcase were oven-dried to constant weight. Additional aliquots of each portion were analysed for lipid and protein content, using standard methods: cold hexane extraction for lipids (Dreosti & Wiechers, 1962), and Kjeldahl for protein (Grodzinski et al., 1975). Weights of water, fat and protein were calculated for the integument and carcase portions, and these were summed for whole body values.
INTRODUCIION
Adult penguins have an annual moult during which the entire plumage is renewed. The moult lasts 2-5 weeks, depending on the species concerned (Stonehouse, 1967). All species spend the entire duration of the moult ashore, on land or on ice. Penguins do not feed while moulting, and subsist on reserves of food accumulated during a pre-moult foraging period. In the eudyptid penguins, adults leave their breeding sites and go to sea immediately after their young have fledged. Four to five weeks elapse before these adults return to moult (Warham 1963, 1971). This paper deals with changes in weight and body composition of moulting macaroni penguins, Eudyptes chrysolophus, and rockhopper penguins, E. chrysocome, at Marion Island (46” 54’ S, 37” 45’ E) in the southern Indian Ocean. An examination of the birds’ energy demands during the moult-fast, related to the quantity of food required during the pre-moult period, leads to a discussion of particular processes associated with moult.
RESULTS
Body weight and composition
Within 24 hr of their arrival ashore, pre-moulting macaroni and rockhopper penguins averaged 59058 (5350-62OOg N = 10) and 35968 (2945395Og N = 9) respectively. The mean daily loss in whole body wt was 105g for macaroni and 82g for rockhopper penguins during their moult-fast (Fig. 1). The absolute quantities of fat, protein and water contained in the whole bodies of the penguins declined progressively during the mot&-fast. The decline was fairly regular for fat and water, but less so for protein content (Figs. 2, 4 & 6).
MATERIALS AND METHODS
.
Twenty-five adults of each species were individually marked while they were rearing chicks during JanuaryFebruary 1974. Towards the end of the pre-moult foraging period, breeding sites were surveyed daily for the marked birds returning to moult. Ten macaroni and 9 rockhopper penguins were captured when first sighted ashore, within 24 hr of their arrival. These birds were kept outdoors in poultry exhibition cages (50 x 50 x 50 cm), until culled or released. Each bird was weighed at capture and daily thereafter. Weights were taken to the nearest 10 g on Pesola balances while the penguins were held in stout plastic sacks. Among the captive birds, 6 macaroni and 9 rockhopper penguins were culled and sexed during their moult-fast. The specimens were wrapped in plastic sacks and kept deep frozen until processed in the laboratory in South Africa. Thawed birds were weighed and then separated into 2 portions: the integument, consisting of feathers, skin and subdermal fat; and the carcase. Each portion was weighed, minced and blended until thoroughly homogenised. A number of random aliquots were taken (see Brisbin, 1968). Aliquots
Macaroni penguin Rockhopper penguin
-do ---oJo
5
5
IOOO-
.t.
I
5
I
IO
I
15
1
20
I
25
I
30
Days Fig. 1. Decline in whole body wt of macaroni and rockhopper penguins during the moult-fast. 27
A. J.
28 Macaroni penguin -mbo Rockhopper penguin ---obo
WILLIAMS et al
0I p
Macaroni penguin -*do Rockhopper penguin ___~~oy
0
250-
5
IO
15
20
25
30
0 . 3:
Fig. 4. Decline in total protein content of macaroni and rockhopper penguins during the moult-fast.
Fig. 2. Decline in total fat content of macaroni and rock-
hopper penguins during the moult-fast.
Pre-moult macaroni and rockhopper penguins contained on average 1296 g and 937 g of fat respectively (Fig. 3); representing 21$/ and 26% respectively of whole body wt. The calculated mean daily loss of fat amounted to 38g and 33 g and fat stores were exhausted after 34 days and 28 days in the captive macaroni and rockhopper penguins respectively. In the rockhopper penguin, subdermal fat reserves exceeded fat deposits in other parts of the body; and they were utilized at a relatively faster rate (Fig. 3). Pre-moult macaroni and rockhopper penguins contained on average 1187g and 739 g of protein respectively (Fig. 4); representing 20% of the whole body wts for both species. The calculated mean daily loss of protein amounted to 11.5 g and 10.9 g for macaroni and rockhopper penguins respectively. However, the calculation makes no allowance for protein lost through the shedding of old feathers and the sheaths of new feathers.
Integument A Carcase - - - A
Fig. 3. Decline in fat content of integument and carcase of rockhopper penguins during the mot&-fast.
In the rockhopper penguin, the protein content of the integument started declining after having remained constant during the first 15 days of the moult-fast (Fig. 5). Presumably, the decline was initiated through the shedding of the feathers and sheaths. Loss of protein from the carcase averaged 7 g/day, with maximum losses occurring after the 15th day of the moult-fast (Fig. 5). Macaroni and rockhopper penguins drink readily during the moult-fast, from freshwater pools when available, and by scooping water off their own backs and flippers during rain (personal observation). Nevertheless, penguins lose considerable quantities of water while fasting. Water formed 55% of the whole body wt of pre-moult macaroni penguins and SSo/, 34 days later, having declined by 54g/day. In rockhopper penguins, water constituted 52% of the whole body wt of the birds at arrival and 46% 28 days later, having declined by 38 g/day (Fig. 6). Energy consumption
The mean daily energy requirements of moulting macaroni and rockhopper penguins amounted to 387 kcal/day and 338 kcal/day respectively (Table 1). These values are 1.6 and 2.1 x higher than the standard metabolic rates (SMR) of the 2 species respectively, based on the formula for calculating SMR in non-passerine birds (Lasiewski & Dawson, 1967).
Fig. 5. Decline in protein content of integument and carcase of rockhopper penguins during the moult-fast.
Body composition and energy metabolism of moulting eudyptid penguins Macaroni penguin -mloE Rockhopper penguin ___.~o~
I
I
I
I
I
I
5
IO
15
20
25
30
Days
Fig. 6. Decline in total water content of macaroni and rockhopper penguins during the moult-fast.
DISCUSSION
During their pre-moult foraging period at sea, macaroni and rockhopper penguins feed predominantly on planktonic crustaceans (personal observation). Similarly, a number of whales build up substantial fat reserves whilst feeding on planktonic crustaceans (Brodie, 1975). The amounts of food required by whales producing known reserves of fat were calculated by Brodie as follows: P = S/(E)(L), where E = efficiency of transfer, L = lipid % of prey, P = total prey required in g, and S = total lipid stored in g. For krill, Euphusia superba, the whales’ principal prey, Brodie assigned a 4% lipid content (wet wt); and efficiency of transfer was set at 75%. If we assume that the crustaceans consumed by the penguins have a similar composition to that of E. superha, we can use Brodie’s formula for solving P as 4320 g and 3 123 g of crustacean food for macaroni and rockhoppcr penguins respectively. Whilst accumulating their fat reserves, pre-moulting penguins must also build up protein for later conversion into feathers. Brodie (1975) suggests that whales are able to satisfy all their additional energy requirements by using the protein contained in the prey necessary for accumulation of fat reserves. Protein content of krill ranges from 14 to 17% (Sidhu et al., 1970; Moiseev, 1970). The calorific
yield of protein from crustaceans consumed by macaroni and rockhopper penguins for lipid storage would be 1814 kcal (4320 x 0.14 x 3.0) and 1311 kcal (3123 x 0.14 x 3.0) respectively, assuming a conversion efficiency of 7.5%. Since captive macaroni penguins use 884 kcal and rockhopper penguins 717 kcal of body protein during moult (Table l), there appears to be more than adequate protein available in the food consumed for fat reserves. In addition to the food required for accumulating reserves for the moult-fast, the penguins must meet the costs of body maintenance, migration between the feeding and moulting sites, and especially the cost of presumed accelerated feeding activity. Assuming that the penguins’ mean energetic cost at sea is 5 x SMR, which seems reasonable for a swimming and diving bird (Prange & Schmidt-Nielsen, 1970), during a 32-day pre-moult period (Warham, 1963, 1971), macaroni and rockhopper penguins would expend 37,760 kcal and 25,920 kcal respectively for maintenance and activity alone. Since the assimilable calorific value of 1 kg of crustaceans is 3270 kcal (deduced from Brodie’s, 1975 formula), a macaroni penguin would require about 11.5 kg of crustacean food to meet this cost, and its total food intake would amount to 16 kg of crustaceans during the 32-day premoult period. A rockhopper penguin, by similar deduction, would require a total of 11 kg of crustacean food in the same period. Female macaroni penguins are capable of bringing 50&6OOg of semi-digested crustacean food to their chicks every 3 or 4 days (personal observation). Four days of feeding and travelling between feeding and breeding grounds would cost a female parent 4720 kcal, assuming a mean metabolic rate 5 x that of SMR. This cost could be met by 1.4 kg of crustacean food. If the female does capture 2 kg of crustacean food in 4 days, including travelling time, it seems reasonable to expect that a macaroni penguin is capable of capturing 16 kg of crustaceans during a 30-day pre-moulting foraging period. A fasting penguin may approach terminal starvation when its energy reserves are exhausted. After completion of the moult, those penguins which still possess fat and protein reserves will best be able to survive journeys to foraging areas. In the yellow-eyed penguin, Megudyptes antipodes, birds below a low critical wt at the end of moult had little chance of survival (Richdale, 1957). If we adopt a post-moult minimum reserve of fat sufficient for 2 days of seagoing activity at 5 x SMR, then the “safe” moult
Table 1. Mean daily fat, protein and energy consumption rockhopper penguins
Macaroni penguin Rockhopper penguin
38 33
in moulting macaroni and
Protein
Fat g/day
29
k&/day* 361 313
gidayt 6.5 6.4
SMRQ:
kcaljdayf 26 25
kcaljday 236 162
* 9.5 kcal/g fat (Petrusewicz & Macfadyen, 1970). t Loss of bid feathers deducted. For macaroni 170g and for rockhopper 125 g, on basis of a 5 kg Adelie penguin having 195 g of feathers (Johnson & West, 1973). $4.0 kcal/g protein (Petrusewicz & Macfadyen, 1970). 0 Lasiewski & Dawson (1967), using body weights of 4.6 & 2.7 kg for macaroni and rockhopper penguins respectively (Prevost & Mougin, 1970).
30
A. J. WILLIAMSet al.
period for macaroni and rockhopper penguins is 28 and 23 days respectively. There is little published information on moult periods in penguins. Richdale (1957) cites 23 days for rockhopper penguins, but this was based on birds moulting well away from their breeding grounds and may be abnormal. He gives 19-26 days for macaroni penguins at Edinburgh Zoo. Warham (1963) gives 31 days at the moult period for rockhopper penguins, but does not say now he derived this figure. Royal penguins, Eudyptes (chrysobphus) schlegeli, moult in 24-29 days (Warham, 1971). Penny (1967) found a wide range in the moult period of the Adelie penguin, Pygoscelis adeliae, with captives taking longer than free-living birds to complete the moult. Although penguins are physiologically well adapted to fasting (Johnson & West, 1973) fasts are nevertheless periods of strain. Fasting birds must have sufficient fat reserves, and at the same time they must enter the fast with body muscles in good condition. During fasting, muscle proteins are used to provide blood glucose for maintenance of the central nervous system (Kety, 1957; Sokoloff, 1960), and glucogenic amino acids for oxaloacetate formation (Gorman & Milne, 1971). The moulting penguin must, in addition to coping with normal fasting stresses, meet increased metabolic demands for thermoregulation and for feather formation. The combination of increased vascularisation of the integument, at a time of reduced feather insulation efficiency, is presumed to lead to an increased energy requirement for thermoregulation (Stonehouse, 1967). Feather formation requires selective protein mobilisation. The total protein required for feather growth is probably set by its cystine content. This amino acid is present in feather keratin at much higher concentrations than in body tissues (Newton, 1968). An intake of 1%19 mg of cystine daily can prevent the loss of 65 g of muscle protein in the domestic fowl (Ackerson & Blish, 1925). Selective mobilisation of cystine during fasting may be particularly taxing. Also, moult in penguins is very concentrated. Many passerines take from 40 to > 100 days to complete a full body moult (Payne, 1972). Migratory passerines moult in fewer days than related resident species, but this concentration is accompanied by a substantial increase in the metabolic rate (Wallgren, 1954). Penguins may also undergo fasts during the breeding season, and in macaroni and rockhopper penguins these fasts are usually some days longer than the moult-fast (Warham, 1963, 1971). Moult induced loss of body wt is 37450/, for 5 penguin species, including the rockhopper penguin (Richdale, 1957). In other avian species wt losses of 43450/, occur only during terminal starvation (Hanson, 1962). In penguins, percentage wt loss during moult is not greater than losses during breeding season fasts. However, the loss in wt during moult is from a higher initial body wt and occurs during a shorter period.
Acknowledgements-The study was supported logistically and financially by the Antarctic Division of the South African Department of Transport. Additional sponsorship was provided by the South African Scientific Committee for Antarctic Research and the University of Cape Town.
We thank John Cooper, Jane Dowle, Trudy Harcus and Ann Moore for technical assistance. REFERENCES ACKERSON C. W. & BLISHM. J. (1925)The effect of cystine on the endogenous metabolism of moulting hens. P&t. Sci. 5, 162-165. BRISBINI. L. (1968) A determination of the caloric density and major body components of large birds. Ecology 49. 792-794. BRODIEP. F. (1975) Cetacean energetics, an overview of intra-specific size variation. Ecology 56. 152-161. DREOSTIG. M. & WIECHERSS. G. (1962) The determination of oil in press cake. F.I.R.I. Annual Report No. 16, 89-91. GORMANM. L. & MILNE H. (1971) Seasonal changes in the adrenal steroid tissues of the Common eider Somateria mollisimo and its relation to organic metabolism in normal and oil-polluted birds. Ibis 113, 218-228. GRODZINSKIW., KLEKOWSKIR. Z. & DUNCANA. (1975) Methods for Ecological Bioenergetics. p. 367 I.B.P. Handbook No. 24, Blackwell, Oxford. HANSIN H. C. (1962) The dynamics of condition factors in Canada geese and their relation to seasonal stresses. Arctic Inst. N. America. Technical paper 12, 148. JOHNSONS. R. & WEST G. C. (1973) Fat content, fatty acid composition and estimates of energy metabolism of Adelie penguins (Pygoscelis adeliae) during the early breeding season fast. Camp. Biochem. Physiol. 45B, 709-7 19. KETY S. S. (1957) The Metabolism of the Central Nervous System (Edited by RICHTERD.). Pergamon Press, Oxford. LASIEWSKI R. C. & DAWSONW. R. (1967) A re-examination of the relation between standard metabolic rate and body weight in birds. Condor 69, 13-23. MOISEEVP. A. (1970) Some aspects of the commerical use of the krill resources of the Antarctic seas. In Antarctic Ecoloav (Edited bv HOLDGATEM. W.) Vol. 1. L nn. L 213-2-<6. Academic Press, New York. ’ NEWTONI. (1968) The temperatures, weights, and body composition of molting Bullfinches. Condor 70, 323-332. PAYNER. B. (1972) Mechanisms and control of moult. In Auian Biology (Edited by FARNERD. S. & KING J. R.), Vol. II. pp. 103-155. Academic Press, New York. PENNY R. L. (1967) Molt in the Adelie penguin, Auk 84, 61-71.
PETRUSEWICZ K. & MACFADYL:N A. (1970) Productivity of Terrestrial Animals, Principals and Methods, p, 190, I.B.P. Handbook No. 13. Blackwell, Oxford. PRANCEH. D. & SCHMIDT-NIELSEN K. (1970) The metabolic cost of swimming in ducks. J. exp. Biol. 53, 76-3777.
RICHDALEL. E. (1957) A Population Study of Penguins, p. 195, Clarendon Press, Oxford. SIDHU G., MONTGOMERY W., HOLLOWAYG., JOHNSONA. & WALKER D. (1970) Biochemical composition and nutritive value of krill (Euphausiu superba Dana). J. Food Agric. 21, 293-296.
SOK~LOFFL. (1960) Metabolism of the central nervous system in vivo. In Handbook of Phvsioloav (Edited bv FIELD J.). Vol. III. pp. 1843-l 864. _Ame&& Physiological Society, Washington D.C. STONEHOUSE B. (1967) The general biology and thermal balance of penguins. Adu. &ol. Res. 4, 731-196. WALLGRENH. A. (1954) Energy metabolism of two species of the genus Emheriza ascorrelated with distribution and migration. Actu 2001. Fenn. 84, l-l 10. WARHAMJ. (1963) The rockhopper penguin, Eudyptes chrysocome, at Macquarie island. Auk 80, 229-256. WARHAMJ. (1971) Aspects of breeding behaviour in the Royal penguin, Eudyptes chrysolophus schlrgeli. Notornis 18, 91-115.
Vol.
56A. pp. 27 ro 30. Pergamon
Press.
BODY COMPOSITION OF MOULTING A. J. Fitzpatrick
WILLIAMS,
W. R.
Printed in GrealBritain
AND ENERGY METABOLISM EUDYPTID PENGUINS
SIEGFRIED, A.
E.
BURGER AND
A.
BERRUTI
Institute, University of Cape Town, Rondebosch 7700, South Africa (Receioed
11 March
1976)
Abstract-l.
Penguins fast during the annual moult. Moulting macaroni penguins, Eudyptes chrysolopenguins, E. chrysocome, were analysed for protein, fat and water content. 2. Fat reserves declined by 38 g/day and were exhausted after 34 days in macaroni penguins. In rockhopper penguins fat reserves declined by 33 g/day and were exhausted after 28 days. 3. Energy consumption of moulting macaroni and rockhopper penguins was 387 kcal/day and 338 kcal/day respectively. 4. Macaroni and rockhopper penguins would need to consume about 16 kg and 11 kg of crustaceans respectively in order to accumulate sufficient food reserves for moulting.
phus, and rockhopper
of integument and carcase were oven-dried to constant weight. Additional aliquots of each portion were analysed for lipid and protein content, using standard methods: cold hexane extraction for lipids (Dreosti & Wiechers, 1962), and Kjeldahl for protein (Grodzinski et al., 1975). Weights of water, fat and protein were calculated for the integument and carcase portions, and these were summed for whole body values.
INTRODUCIION
Adult penguins have an annual moult during which the entire plumage is renewed. The moult lasts 2-5 weeks, depending on the species concerned (Stonehouse, 1967). All species spend the entire duration of the moult ashore, on land or on ice. Penguins do not feed while moulting, and subsist on reserves of food accumulated during a pre-moult foraging period. In the eudyptid penguins, adults leave their breeding sites and go to sea immediately after their young have fledged. Four to five weeks elapse before these adults return to moult (Warham 1963, 1971). This paper deals with changes in weight and body composition of moulting macaroni penguins, Eudyptes chrysolophus, and rockhopper penguins, E. chrysocome, at Marion Island (46” 54’ S, 37” 45’ E) in the southern Indian Ocean. An examination of the birds’ energy demands during the moult-fast, related to the quantity of food required during the pre-moult period, leads to a discussion of particular processes associated with moult.
RESULTS
Body weight and composition
Within 24 hr of their arrival ashore, pre-moulting macaroni and rockhopper penguins averaged 59058 (5350-62OOg N = 10) and 35968 (2945395Og N = 9) respectively. The mean daily loss in whole body wt was 105g for macaroni and 82g for rockhopper penguins during their moult-fast (Fig. 1). The absolute quantities of fat, protein and water contained in the whole bodies of the penguins declined progressively during the mot&-fast. The decline was fairly regular for fat and water, but less so for protein content (Figs. 2, 4 & 6).
MATERIALS AND METHODS
.
Twenty-five adults of each species were individually marked while they were rearing chicks during JanuaryFebruary 1974. Towards the end of the pre-moult foraging period, breeding sites were surveyed daily for the marked birds returning to moult. Ten macaroni and 9 rockhopper penguins were captured when first sighted ashore, within 24 hr of their arrival. These birds were kept outdoors in poultry exhibition cages (50 x 50 x 50 cm), until culled or released. Each bird was weighed at capture and daily thereafter. Weights were taken to the nearest 10 g on Pesola balances while the penguins were held in stout plastic sacks. Among the captive birds, 6 macaroni and 9 rockhopper penguins were culled and sexed during their moult-fast. The specimens were wrapped in plastic sacks and kept deep frozen until processed in the laboratory in South Africa. Thawed birds were weighed and then separated into 2 portions: the integument, consisting of feathers, skin and subdermal fat; and the carcase. Each portion was weighed, minced and blended until thoroughly homogenised. A number of random aliquots were taken (see Brisbin, 1968). Aliquots
Macaroni penguin Rockhopper penguin
-do ---oJo
5
5
IOOO-
.t.
I
5
I
IO
I
15
1
20
I
25
I
30
Days Fig. 1. Decline in whole body wt of macaroni and rockhopper penguins during the moult-fast. 27
A. J.
28 Macaroni penguin -mbo Rockhopper penguin ---obo
WILLIAMS et al
0I p
Macaroni penguin -*do Rockhopper penguin ___~~oy
0
250-
5
IO
15
20
25
30
0 . 3:
Fig. 4. Decline in total protein content of macaroni and rockhopper penguins during the moult-fast.
Fig. 2. Decline in total fat content of macaroni and rock-
hopper penguins during the moult-fast.
Pre-moult macaroni and rockhopper penguins contained on average 1296 g and 937 g of fat respectively (Fig. 3); representing 21$/ and 26% respectively of whole body wt. The calculated mean daily loss of fat amounted to 38g and 33 g and fat stores were exhausted after 34 days and 28 days in the captive macaroni and rockhopper penguins respectively. In the rockhopper penguin, subdermal fat reserves exceeded fat deposits in other parts of the body; and they were utilized at a relatively faster rate (Fig. 3). Pre-moult macaroni and rockhopper penguins contained on average 1187g and 739 g of protein respectively (Fig. 4); representing 20% of the whole body wts for both species. The calculated mean daily loss of protein amounted to 11.5 g and 10.9 g for macaroni and rockhopper penguins respectively. However, the calculation makes no allowance for protein lost through the shedding of old feathers and the sheaths of new feathers.
Integument A Carcase - - - A
Fig. 3. Decline in fat content of integument and carcase of rockhopper penguins during the mot&-fast.
In the rockhopper penguin, the protein content of the integument started declining after having remained constant during the first 15 days of the moult-fast (Fig. 5). Presumably, the decline was initiated through the shedding of the feathers and sheaths. Loss of protein from the carcase averaged 7 g/day, with maximum losses occurring after the 15th day of the moult-fast (Fig. 5). Macaroni and rockhopper penguins drink readily during the moult-fast, from freshwater pools when available, and by scooping water off their own backs and flippers during rain (personal observation). Nevertheless, penguins lose considerable quantities of water while fasting. Water formed 55% of the whole body wt of pre-moult macaroni penguins and SSo/, 34 days later, having declined by 54g/day. In rockhopper penguins, water constituted 52% of the whole body wt of the birds at arrival and 46% 28 days later, having declined by 38 g/day (Fig. 6). Energy consumption
The mean daily energy requirements of moulting macaroni and rockhopper penguins amounted to 387 kcal/day and 338 kcal/day respectively (Table 1). These values are 1.6 and 2.1 x higher than the standard metabolic rates (SMR) of the 2 species respectively, based on the formula for calculating SMR in non-passerine birds (Lasiewski & Dawson, 1967).
Fig. 5. Decline in protein content of integument and carcase of rockhopper penguins during the moult-fast.
Body composition and energy metabolism of moulting eudyptid penguins Macaroni penguin -mloE Rockhopper penguin ___.~o~
I
I
I
I
I
I
5
IO
15
20
25
30
Days
Fig. 6. Decline in total water content of macaroni and rockhopper penguins during the moult-fast.
DISCUSSION
During their pre-moult foraging period at sea, macaroni and rockhopper penguins feed predominantly on planktonic crustaceans (personal observation). Similarly, a number of whales build up substantial fat reserves whilst feeding on planktonic crustaceans (Brodie, 1975). The amounts of food required by whales producing known reserves of fat were calculated by Brodie as follows: P = S/(E)(L), where E = efficiency of transfer, L = lipid % of prey, P = total prey required in g, and S = total lipid stored in g. For krill, Euphusia superba, the whales’ principal prey, Brodie assigned a 4% lipid content (wet wt); and efficiency of transfer was set at 75%. If we assume that the crustaceans consumed by the penguins have a similar composition to that of E. superha, we can use Brodie’s formula for solving P as 4320 g and 3 123 g of crustacean food for macaroni and rockhoppcr penguins respectively. Whilst accumulating their fat reserves, pre-moulting penguins must also build up protein for later conversion into feathers. Brodie (1975) suggests that whales are able to satisfy all their additional energy requirements by using the protein contained in the prey necessary for accumulation of fat reserves. Protein content of krill ranges from 14 to 17% (Sidhu et al., 1970; Moiseev, 1970). The calorific
yield of protein from crustaceans consumed by macaroni and rockhopper penguins for lipid storage would be 1814 kcal (4320 x 0.14 x 3.0) and 1311 kcal (3123 x 0.14 x 3.0) respectively, assuming a conversion efficiency of 7.5%. Since captive macaroni penguins use 884 kcal and rockhopper penguins 717 kcal of body protein during moult (Table l), there appears to be more than adequate protein available in the food consumed for fat reserves. In addition to the food required for accumulating reserves for the moult-fast, the penguins must meet the costs of body maintenance, migration between the feeding and moulting sites, and especially the cost of presumed accelerated feeding activity. Assuming that the penguins’ mean energetic cost at sea is 5 x SMR, which seems reasonable for a swimming and diving bird (Prange & Schmidt-Nielsen, 1970), during a 32-day pre-moult period (Warham, 1963, 1971), macaroni and rockhopper penguins would expend 37,760 kcal and 25,920 kcal respectively for maintenance and activity alone. Since the assimilable calorific value of 1 kg of crustaceans is 3270 kcal (deduced from Brodie’s, 1975 formula), a macaroni penguin would require about 11.5 kg of crustacean food to meet this cost, and its total food intake would amount to 16 kg of crustaceans during the 32-day premoult period. A rockhopper penguin, by similar deduction, would require a total of 11 kg of crustacean food in the same period. Female macaroni penguins are capable of bringing 50&6OOg of semi-digested crustacean food to their chicks every 3 or 4 days (personal observation). Four days of feeding and travelling between feeding and breeding grounds would cost a female parent 4720 kcal, assuming a mean metabolic rate 5 x that of SMR. This cost could be met by 1.4 kg of crustacean food. If the female does capture 2 kg of crustacean food in 4 days, including travelling time, it seems reasonable to expect that a macaroni penguin is capable of capturing 16 kg of crustaceans during a 30-day pre-moulting foraging period. A fasting penguin may approach terminal starvation when its energy reserves are exhausted. After completion of the moult, those penguins which still possess fat and protein reserves will best be able to survive journeys to foraging areas. In the yellow-eyed penguin, Megudyptes antipodes, birds below a low critical wt at the end of moult had little chance of survival (Richdale, 1957). If we adopt a post-moult minimum reserve of fat sufficient for 2 days of seagoing activity at 5 x SMR, then the “safe” moult
Table 1. Mean daily fat, protein and energy consumption rockhopper penguins
Macaroni penguin Rockhopper penguin
38 33
in moulting macaroni and
Protein
Fat g/day
29
k&/day* 361 313
gidayt 6.5 6.4
SMRQ:
kcaljdayf 26 25
kcaljday 236 162
* 9.5 kcal/g fat (Petrusewicz & Macfadyen, 1970). t Loss of bid feathers deducted. For macaroni 170g and for rockhopper 125 g, on basis of a 5 kg Adelie penguin having 195 g of feathers (Johnson & West, 1973). $4.0 kcal/g protein (Petrusewicz & Macfadyen, 1970). 0 Lasiewski & Dawson (1967), using body weights of 4.6 & 2.7 kg for macaroni and rockhopper penguins respectively (Prevost & Mougin, 1970).
30
A. J. WILLIAMSet al.
period for macaroni and rockhopper penguins is 28 and 23 days respectively. There is little published information on moult periods in penguins. Richdale (1957) cites 23 days for rockhopper penguins, but this was based on birds moulting well away from their breeding grounds and may be abnormal. He gives 19-26 days for macaroni penguins at Edinburgh Zoo. Warham (1963) gives 31 days at the moult period for rockhopper penguins, but does not say now he derived this figure. Royal penguins, Eudyptes (chrysobphus) schlegeli, moult in 24-29 days (Warham, 1971). Penny (1967) found a wide range in the moult period of the Adelie penguin, Pygoscelis adeliae, with captives taking longer than free-living birds to complete the moult. Although penguins are physiologically well adapted to fasting (Johnson & West, 1973) fasts are nevertheless periods of strain. Fasting birds must have sufficient fat reserves, and at the same time they must enter the fast with body muscles in good condition. During fasting, muscle proteins are used to provide blood glucose for maintenance of the central nervous system (Kety, 1957; Sokoloff, 1960), and glucogenic amino acids for oxaloacetate formation (Gorman & Milne, 1971). The moulting penguin must, in addition to coping with normal fasting stresses, meet increased metabolic demands for thermoregulation and for feather formation. The combination of increased vascularisation of the integument, at a time of reduced feather insulation efficiency, is presumed to lead to an increased energy requirement for thermoregulation (Stonehouse, 1967). Feather formation requires selective protein mobilisation. The total protein required for feather growth is probably set by its cystine content. This amino acid is present in feather keratin at much higher concentrations than in body tissues (Newton, 1968). An intake of 1%19 mg of cystine daily can prevent the loss of 65 g of muscle protein in the domestic fowl (Ackerson & Blish, 1925). Selective mobilisation of cystine during fasting may be particularly taxing. Also, moult in penguins is very concentrated. Many passerines take from 40 to > 100 days to complete a full body moult (Payne, 1972). Migratory passerines moult in fewer days than related resident species, but this concentration is accompanied by a substantial increase in the metabolic rate (Wallgren, 1954). Penguins may also undergo fasts during the breeding season, and in macaroni and rockhopper penguins these fasts are usually some days longer than the moult-fast (Warham, 1963, 1971). Moult induced loss of body wt is 37450/, for 5 penguin species, including the rockhopper penguin (Richdale, 1957). In other avian species wt losses of 43450/, occur only during terminal starvation (Hanson, 1962). In penguins, percentage wt loss during moult is not greater than losses during breeding season fasts. However, the loss in wt during moult is from a higher initial body wt and occurs during a shorter period.
Acknowledgements-The study was supported logistically and financially by the Antarctic Division of the South African Department of Transport. Additional sponsorship was provided by the South African Scientific Committee for Antarctic Research and the University of Cape Town.
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