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Diving behaviour and energetics in breeding little penguins (Eudyptula minor)
... However, when compared to RMR air of 3.8 W kg –1 (measured during the active phase in normally fed Humboldt penguins within their thermoneutral zone; Luna-Jorquera 1997), RMR water is only 1.6 × RMR air . This is quite low, as Bethge et al. (1997) reported that in little penguins Eudyptula minor RMR water at 10°C is 2.6 × RMR air . Simi- larly, Culik & Wilson (1991) reported that mean RMR water of Adélie penguins (4°C) amounts to 2.2 × RMR air . ...
... Differences between birds were not significant (p = 0.323) boldt penguins at sea (Luna-Jorquera & Culik 1999). However, slow speeds were also observed by Culik et al. (1994a) and Bethge et al. (1997), in pygoscelid and little penguins during similar experiments. According to these authors, gentoo penguins Pygoscelis papua, Adélie penguins Pygoscelis adeliae and chinstrap penguins P. antarctica observed in a 21 m long swim channel swam 21, 32 and 35% slower than measured in the wild, respectively, whereas little penguins swam 80% slower. ...
... Minimum COT cor of Humboldt penguins (at 1.5 m s –1 ) were between those of Adélie penguins (4.9 J [kg m] –1 at 2.2 m s –1 ) and gentoo penguins (7.6 J [kg m] –1 at 1.8 m s –1 ) (Culik et al. 1994a) (Table 4). In the much smaller little penguin, Bethge et al. (1997) found minimum COT of 11.1 J (kg m) –1 at 1.8 m s –1 . Although minimum COT in the channel occured at 1.5 m s –1 , we measured that Humboldt penguins in the wild prefer to travel at 1.7 m s –1 (Luna-Jorquera & Culik 1999). ...
As one of the elements for a model on the food requirements of Humboldt penguins Spheniscus humboldti we determined, via gas respirometry, metabolic rates while swimming and resting in water. During rest in water at 19 degrees C Humboldt penguins (mean body mass 3.6 kg) required 5.95 W kg(-1). This corresponds to a thermal conductance in water of 0.2975 W (kg degrees C)(-1) (at T-a 19 degrees C and assuming a Tb Of 39 degrees C). When swimming in a 20 m long channel, metabolism rose from 8 W kg(-1) at a speed of 0.6 ms(-1) to 23.1 W kg(-1) at 2.2 m s(-1). Transport costs (the cost to move 1 kg of body mass over a distance of 1 m) reached a minimum at 1.4 ms(-1) with 8.1 J (kg m)(-1), which corresponds to 0.89 J (Nm)(-1). We corrected for acceleration and deceleration in the channel to determine transport costs of free-ranging Humboldt penguins travelling at sea, which were calculated as 7 J (kg m)(-1) (0.71 J [Nm](-1)), at 1.7 m s(-1). Birds feeding chicks need to balance the costs of either (1) returning to the breeding island for the night and travelling back to the feeding grounds in the morning or (2) incurring increased thermoregulatory costs associated with resting at sea overnight. Simple calculations show that at water temperatures of 19 degrees C we expect Humboldt penguins to show a tendency to remain at sea overnight if foraging areas are >4 km from their island. In colder waters (12 degrees C), this distance increases to >9 km. Using previously published data on at-sea activity of Humboldt penguins, we found that foraging costs during chick rearing amount to 340 g anchovies d(-1). Finally, we present a general model to convert Humboldt penguin activity data at sea to food requirements.
... Consequently, chick growth depends on provisioning rates by the female. The picture is not complicated by gender differences in the foraging ecology of adult birds (Bethge et al. 1997, Clarke et al. 1998 During the brooding period, females make daily foraging trips, feeding at that time in the immediate vicinity of the colonies and spending the night ashore (Warham 1975, Tremblay & Cherel 2000 ). This behaviour permits characteristics of foraging trips to be recorded by fitting different females with TDRs at a high turnover rate. ...
... This behaviour permits characteristics of foraging trips to be recorded by fitting different females with TDRs at a high turnover rate. Previous work on the diving behaviour of penguins has often included just a few trips carried out by a relatively small number of birds (Bengtson et al. 1993, Croxall et al. 1993, Kooyman & Kooyman 1995, Bethge et al. 1997, Peters 1997). ...
... However, our main goal was to study foraging behaviour in contrasting marine environments, whatever the causes of the differences among them were. Temporal variation in penguin foraging ecology has been found using TDRs both within (Williams et al. 1992, Robinson & Hindell 1996, Bethge et al. 1997, Kirkwood & Robertson 1997b, Moore et al. 1999) and between (Watanuki et al. 1993, Hull 2000 ) seasons. Nevertheless, a comparison between 2 successive brooding periods in 1995 (Cherel et al. 1999) and 1996 (present study) using the same methodology showed little variation in the foraging behaviour of female rockhopper penguins from AMS. ...
The foraging ecology of rockhopper penguins was investigated at 3 sites marked by contrasting ecological conditions. The northern subspecies was studied at Amsterdam Island (AMS) in oceanic subtropical waters, and the southern subspecies at the Kerguelen Archipelago (KER) in a subantarctic coastal habitat and at the Crozet Archipelago (CRO) in subantarctic neritic waters. Dur- ing the brooding period, females from every site mainly made daily foraging trips lasting 11 to 12 h. A principal component analysis (PCA) on 22 variables of daily foraging trips reduced these variables to 3 principal components, which were related to diving mode (PC1), foraging effort (PC2) and vari- ation in diving behaviour (PC3). Overall, PC1 indicated that birds from AMS dived shallower, had shorter dive duration and bottom time, and were less active during less efficient dives than birds from KER and CRO. On the other hand, PC3 showed that birds from KER segregated from those of AMS and CRO by performing more uniform foraging trips with less variability in dive parameters. The PCA emphasised that most of the characteristics of daily trips and all the characteristics of foraging dives varied according to the study sites, thus stressing the importance of distinct environments in shaping the foraging behaviour of seabirds. Food loads, and accordingly chick growth, were lower at AMS, medium at CRO and higher at KER, while indices of foraging effort presented little variation. Birds at AMS fed mainly on the euphausiid Thysanoessa gregaria and on larger juvenile squids, while birds from CRO and KER preyed upon the subantarctic krill Euphausia vallentini. Diving strategies together with food loads and chick growth rates suggest that prey availability was low at AMS, intermediate at CRO and high at KER, which is in agreement with previous data on chlorophyll concentrations and zooplankton biomass. The study shows the complexity of foraging behaviour of penguins. It illustrates the importance of behavioural plasticity and suggests that it is a fundamental trait of the life history of seabirds living in highly variable environments.
... Wilson et al. 1992, Lovvorn et al. 1999, Lovvorn 2001). Using oxygen consumption rates of penguins while swimming horizontally at various speeds in shallow swim canals, some authors (e.g., Bethge et al. 1997) suggested that penguins swam at optimal swim speeds while maintaining minimum cost of transport (COT). However, the direct decision variables for the vertical movements of diving seabirds through water are those that affect regulation of stroke frequency rather than swim speed. ...
... (2), we sought optimal parameters a and K for 249Table 1 Speed (m s –1 ) b given output power strategies that minimize COT for a given target depth, assuming a BMR of 8.5 J s –1 . This is the same as that of 1.2 kg little penguins Eudyptula minor (Bethge et al. 1997). Note that total energetic cost in the model consists of energy used for mechanical work to transport, and for basal metabolism during transport. ...
... In the present model, we assumed that divers minimize their COT, or energy used per unit distance during diving. Several studies report that divers prefer swimming speeds where the COT is minimized (e.g., Bethge et al. 1997, Wilson et al. 2002), suggesting this assumption is realistic. However, it should be noted that minimizing this cost maximizes the energy or time spent for other activities during the dive cycle, such as feeding. ...
Diving animals have to counter both drag and buoyancy when moving through the water column. The magnitude of these forces depends upon an animal's swim speed and current depth. Feet, fins or flippers create a motivating force, and different stroke strategies give a variable level of output power, providing both fast swim speeds and reduced travel times to any given target depth. However, while feet, fins or flippers may confer a real advantage, they also create considerable drag and engen- der high metabolic (oxygen consumption) costs. Consequently, there should be an optimal relationship between output power and stroke frequency during diving. Here we develop diving models to predict the optimal pattern of stroke frequency during both the descent and ascent phase of divers in water, while maintaining a minimum cost of transport (COT, J kg -1 m -1 ). We also test predictions derived from these models using diving data for foot-propelled South Georgian shags Phalacrocorax georgianus diving to deeper than 80 m. Our predictions include: (1) output power (stroke frequency) should de- cline during the descent and ascent phases of a dive, but constant output power should be evident when the diving depth is shallow, (2) initial thrust for dives to deeper target depths should be smaller during the descent phase and greater during the ascent phase, and, (3) swim speed should be constant during the descent phase and should decrease first or remain constant, then increase during the ascent phase because of a declining output power strategy. Our empirical data on shags support only some of these predictions. Predictions (1) and (3) were supported by our observations, but Prediction (2) was not, possibly due to unknown but specific factors concerning diving seabirds. These findings suggest that diving seabirds adjust and control their stroke frequency pattern in order to minimize COT during diving, generating the observed changes in swimming speed.
... Measurement of speed in free-ranging penguins has shown that individuals swim at a roughly constant speed during the majority of their dives and during all travelling phases of dives (Wilson et al. 2002; Ropert-Coudert et al. 2001a; Bethge et al. 1997). Departures from this cruising speed have therefore been thought to reflect the encounter and pursuit of prey (Ropert-Coudert et al. 2000; Wilson et al. 2002) and, in keeping with this, Little Penguins have been observed to accelerate when capturing fish prey in both shallow and deep waters and when capturing either a solitary fish or one from a shoal (Schulz 1987; Cannell 1994). ...
... Therefore, measurement of changes of swimming speed of Little Penguins should help elucidate their foraging strategies and prey encounter rate. Since reliable swim speed recorders are generally too large for such a small animal (0.6–1.4 kg, but see Bethge et al. 1997), we used minute accelerometers that record simultaneously the body posture and the dynamic motion of animals (Yoda et al. 2001; Ropert- Coudert et al. 2004b, c; Watanuki et al. 2003) to determine flipper beat frequency as a proxy for acceleration. This study aimed to reconstruct the time/activity budget of free-ranging Little Penguins from Penguin Island, Western Australia as they foraged in the shallow waters of Comet Bay. ...
... Aside from this, nothing is known about prey encounter rates and the portion of underwater time devoted to feeding and travelling. Measurement of speed in free-ranging penguins has shown that individuals swim at a roughly constant speed during the majority of their dives and during all travelling phases of dives (Wilson et al. 2002; Ropert-Coudert et al. 2001a; Bethge et al. 1997). Departures from this cruising speed have therefore been thought to reflect the encounter and pursuit of prey (Ropert-Coudert et al. 2000; Wilson et al. 2002) and, in keeping with this, Little Penguins have been observed to accelerate when capturing fish prey in both shallow and deep waters and when capturing either a solitary fish or one from a shoal (Schulz 1987; Cannell 1994). ...
There is little information on the effort put into foraging by seabirds, even though it is fundamental to many issues in behavioural ecology. Recent researchers have used changes in the underwater cruising speed of penguins to allude to prey ingestion since accelerations are thought to reflect the encounter and pursuit of prey. In this study, we attached minute accelerometers, to determine flipper beat frequency as a proxy for prey pursuit, to Little Penguins Eudyptula minor foraging in shallow waters in Western Australia. During diving, Little Penguins flapped continuously and at a regular pace of 3.16Hz while descending the water column and throughout the bottom phase of most dives. However, the frequency and amplitude of wingbeats increased transitorily, reaching 3.5–5.5Hz, during some dives indicating prey pursuit. Pursuit phases lasted a mean of 2.93.3s and occurred principally during the bottom phases of dives (75.4%). Most dives in all birds (86%) had a clear square-shaped depth profile indicating feeding activity near the seabed in the shallow waters of the bays. Hourly maximum depth, time spent underwater, percentage of dives with pursuit events and catch per unit effort showed an overall increase from zero at ca. 0500h to a maximum during the hours around mid-day before decreasing to zero by 1900h. During pursuit phases, Little Penguins headed predominantly downward, probably using the seabed to assist them in trapping their prey. In the light of our results, we discuss depth use by Little Penguins and their allocation of foraging effort and prey capture success as a function of environmental conditions.
... In a subsequent study, Drabek (1997) compared and contrasted the heart morphology of these deep-diving penguin species with that of the little penguin (Eudyptula minor). The little penguin represents the smallest of all the penguin species and is known to be a brief, shallow diver (Bethge et al. 1997). Drabek reported that the little penguin heart is not larger than expected for its body mass and that the right ventricle relative to the heart and left ventricle is signi®cantly less muscularized than right ventricles in the larger, deeper-diving penguin species. ...
... e diverse and variable marine environments.Table 2 shows the few penguin species for which both heart data and diving capabilities are known. Since dive depths measured by capillary tubes tend to over-estimate maximum depths in comparison to dives measured with time-depth recorders (TDRs), the observed maximum depths listed were recorded with TDRs. Bethge et al. (1997) reported that the little penguin spent 60% of its time swimming, but only 16.4% of its time was spent diving. In contrast, Cherel et al. (1999) found that the rockhopper penguin spent an estimated 80±90% underwater (diving and swimming) when at sea, 69% of which was diving to ³3 m. The right ventricular hypertrophy we ®nd in the norther ...
... Since only dives ³3 m were taken into account, this value is underestimated , and the total time underwater (diving plus swimming between 3 m depth and the surface) may attain 80±90%. In contrast, the highest recorded value for total percentage of time spent underwater comes from Bethge et al. (1997) who reported that the little penguin spent 60% of itstimèàctive at sea'' (swimming plus diving), but only 16.4% of its time was spent diving. The rockhopper penguin exhibits both the higher percentage of foraging trips underwater and the higher diving rate among penguins. ...
We compared the heart morphology of the small, deep-diving northern rockhopper penguin to the hearts of small, shallow-diving
and large, deep-diving penguin species. The rockhopper penguin had a heart larger than expected for its body mass, and its
heart weight/body weight was significantly greater than in the larger Adélie penguin. We found the rockhopper's right ventricle
weight/heart weight to be significantly greater than this relationship in both the larger chinstrap and Adélie penguins. The
relationship of the right to left ventricular weights in the rockhopper heart is not different to that of the large, deepest-diving
emperor penguin. A larger heart in the rockhopper penguin might be related to its diving behavior and ecology if it contributes
to diving efficiency during foraging by increasing lung perfusion during surface recovery. This would lead to decreased surface
time.
... To calculate the rate of oxygen consumption while foraging we assumed that O 2 -consumption in the chamber was identical to the platypus's resting values at the water surface and subtracted the resting metabolism in the chamber from the total amount of oxygen consumed during the recovery period after each dive. (Culik and Wilson 1991; Bethge et al. 1997). Conversion into watts per kilogram was made assuming a conversion factor of 20.11 kJ l ±1 oxygen (Grant and Dawson 1978a). ...
... As swimming speed rises further, hydrodynamic drag, which increases roughly in proportion to the square of speed, becomes the predominant factor. The power to overcome hydrodynamic drag increases with the third power of speed (SchmidtNielsen 1995 ) which is why we used a third degree polynomial function to regress power input during subsurface swimming against speed (see for comparison Culik and Wilson 1994; Bethge et al. 1997; Borgwardt and Culik 1999) yielding P (DIVE) =236.14 v 3 ±167.84 v 2 +35.51 v+ P (REST)[water] where v=swim speed and P
RESTwater =power input during rest at the water surface (4.81 W kg ±1 ), (Fig. 2). ...
... Their low rates are also unexpected if we take into account that animals in their study temporarily swam on the water surface which is generally regarded as more costly for semiaquatic mammals (Williams 1989). Compared to swim ¯umes where animals have to maintain an unnatural position or a certain speed, the swim tank used in this study allowed the platypuses to select their own swimming speed and dive duration and to forage voluntarily while all activities and gaseous exchange could be closely monitored (see also Culik and Wilson 1991; Culik and Wilson 1994; Bethge et al. 1997). The derived foraging metabolic rate, P (FORAGE) , includes the costs of diving to the bottom of the tank (phase-1-behaviour), of the typical searching behaviour and food intake (phase-2) as well as of resurfacing after the dive (phase-3). ...
We measured the energy requirements of platypuses foraging, diving and resting in a swim tank using flow-through respirometry. Also, walking metabolic rates were obtained from platypuses walking on a conventional treadmill. Energy requirements while foraging were found to depend on water temperature, body weight and dive duration and averaged 8.48 W kg(-1). Rates for subsurface swimming averaged 6.71 W kg(-1). Minimal cost of transport for subsurface swimming platypuses was 1.85 J N(-1)m(-1) at a speed of 0.4 m s(-1). Aerobic dive limit of the platypus amounted to 59 s. Metabolic rate of platypuses resting on the water surface was minimal with 3.91 W kg(-1) while minimal RMR on land was 2.08 W kg(-1). The metabolic rate for walking was 8.80 W kg(-1) and 10.56 W kg(-1) at speeds of 0.2 m s(-1) and 0.3 m s(-1), respectively. A formula was derived, which allows prediction of power requirements of platypuses in the wild from measurements of body weight, dive duration and water temperature. Platypuses were found to expend energy at only half the rate of semiaquatic eutherians of comparable body sizes during both walking and diving. However, costs of transport at optimal speed were in line with findings for eutherians. These patterns suggest that underwater locomotion of semiaquatic mammals have converged on very similar efficiencies despite differences in phylogeny and locomotor mode.
... Increases in dive duration with increasing maximum dive depth were also found by Bengston et al. (1993) and seem to be a standard feature of penguin foraging behaviour (e.g. Gentoo Penguins (Williams et al. 1992, Wilson et al. 1996a), Adélie Penguins (Chappell et al. 1993), King Penguins (Kooyman et al. , Pütz 1994), Emperor Penguins A. forsteri (Kooyman & Kooyman 1995, Kirkwood & Robertson 1997), African Penguins Spheniscus demersus (), Humboldt Penguins S. humboldti (Luna & Culik 1999 ), Rockhopper Penguins Eudyptes chrysocome (Wilson et al. 1997), and Little Penguins Eudyptula minor (Bethge et al. 1997 ). Results from other species also suggest that dive and return-to-surface angles increase with increasing maximum dive depth which increases descent rate because swim speeds remain essentially constant (, Wilson et al. 1996a, R.P. Wilson unpubl. ...
... Of the congeners, the normal swim speed of Adélie Penguins is 2.2 m/s and that of Gentoo Penguins is only 1.8 m/s (Culik et al. 1994). Values for other species range from 1.8 m/s for Little Penguins (Bethge et al. 1997) to 2.2 m/s for King Penguins () (other values are summarized in ). It is perhaps worth pointing out that Culik et al. (1994) found the lowest cost of transport in Chinstrap Penguins to be at speeds of 2.4 m/s, again, the highest of the Pygoscelis species, and a figure that accords well with that found in our study. ...
The foraging behaviour of 20 Chinstrap Penguins Pygoscelis antarctica breeding at Ardley Island, King George Island, Antarctica was studied during the austral summers of 1991/2 and 1995/6 using stomach temperature loggers (to determine feeding patterns), depth recorders and multiple channel loggers. The multiple channel loggers recorded dive depth, swim speed and swim heading which could be integrated using vectors to determine the foraging tracks. Half the birds left the island to forage between 02h00 and 10h00. Mean time at sea was 10.6 h. Birds generally executed a looping type course with most individuals foraging within 20 km of the island. Maximum foraging range was 33.5 km. Maximum dive depth was 100.7 m although 80% of all dives had depth maxima less than 30 m. The following dive parameters were positively related to maximum depth reached during the dive: total dive duration, descent duration, duration at the bottom of the dive, ascent duration, descent angle, ascent angle, rate of change of depth during descent and rate of change of depth during ascent. Swim speed was unrelated to maximum dive depth and had mean values of 2.6,2.5 and 2.2 m/s for the descent, bottom and ascent phases of the dive. The sequence of maximum depths reached in a dive series was not random, tending to be concentrated at a particular depth, irrespective of whether the penguins were feeding at that depth or not. Generally, sequential dives to a specific depth were abruptly terminated by a single dive to another depth which was characteristic in having no bottom phase and unusually steep descent and ascent angles. The maximum depth reached during this dive was then adhered to in the next dive sequence. There were peaks in feeding activity between 06h00 and 09h00 and 14h00 and 22h00. Although foraging effort and relative success decreased around midnight when light intensity was lowest, birds did dive up to 22 m at this time, considerably deeper than sympatric Adélie P. adeliae or Gentoo P. papua Penguins. These findings indicate that, in accordance with their small body size, Chinstrap Penguins forage inshore close to the surface during the chick-rearing phase. Apparent short-comings in the volume of water searched compared to sympatric congeners can be made good by intense diving activity during the period at sea, with no inter-bout rests, higher swim speeds and an apparent ability to be able to forage at lower light intensities which enables Chinstrap Penguins to forage better under twilight conditions.
... Authors such as Ancel et al. (2000) have looked at metabolic rate as a function of swim speed using water flumes; others, such as Culik et al. (1991 Culik et al. ( , 1996), used a still-water swim channel to document how energy expenditure changes with speed in a suite of airbreathing diving animals ranging from penguins to beavers (e.g. Allers & Culik 1997, Bethge et al. 1997, Borgwardt & Culik 1999). However, all animals used in such experiments were obliged to swim underwater at shallow depths (around 0.5 m) so that buoyancy issues, which change substantially with depth in animals that contain appreciable body volumes of air, particularly birds (Wilson et al. 1992), could not be addressed. ...
... Data were collected from 34 Magellanic penguins Spheniscus magellanicus brooding small chicks at 3 colonies (San Lorenzo, 42° 04' S, 63° 21' W, n = 7 birds; Bahia Bustamante, 45° 10' S, 66° 30' W, n = 19; San Julian, 49° 16' S, 67° 42' W, n = 8) in Patagonia, Argentina between November 2006 and December 2008 inclusive. Birds were carefully removed from their nests before being equipped with multichannel archival tags, called daily diaries (DD; Wilson et al. 2008), using overlapping strips of Tesa tape (Wilson et al. 1997). The devices (max. ...
Depth-dependent buoyancy resulting from the compression of body-associated air is a major force modulating energy expenditure in diving seabirds, yet quantification of its effects in free- living animals is problematic. Between November 2006 and December 2008, we used multiple chan- nel loggers (daily diaries (DDs)); recording triaxial acceleration, depth and speed, during foraging of 34 Magellanic penguins Spheniscus magellanicus from 3 colonies in Argentina to derive a new proxy for energy expenditure, overall dynamic body acceleration (ODBA). Assuming ODBA to be linearly related to power, energy expenditure was highest during dive descent, nearer the surface and in those dives terminating at greater depths due to steeper descent angles. Swim speed during descent was invariant of maximum dive depth. Calculated energy expenditure during the bottom phase of the dive was invariant of depth, but energy expenditure of birds returning to the surface was lowest at any given depth for birds that had engaged in deeper dives due to the effects of buoyancy. Four birds, equipped with beak angle-measuring sensors as part of the DDs, captured 89% of their prey (nor- mally pelagic school fish) during fast passive ascents using buoyancy to aid in capture. Details from one of these birds showed that this passive ascent occurred at a mean velocity of 1.94 m s -1 for a mean of 2.02 s; ascent angles during such rushes were steeper when the bird was deeper, which was pre- sumed to reflect a response to the diminished buoyant force at greater pressures. Passive ascents during prey capture appear to be an important mechanism for Magellanic penguins to capture fast- moving prey with minimal energy expenditure.
... There are essentially 3 phases to foraging trips. Trips generally begin with a phase during which birds move rapidly and directly away from the nest site (e.g. Bethge et al. 1997, Gaston & Jones 1998, Weimerskirch 1998a), a behaviour which allows them to minimise time in zones where prey density is low (Birt et al. 1987, Irons 1998). At some point the behaviour changes substantially when active search begins. ...
... In a final phase, seabirds return rapidly and directly to the nest, with little deviation from a straight line course (e.g. Jouventin et al. 1994, Bethge et al. 1997, Bost et al. 1997 ). A consequence of this behaviour is that foraging tracks of nesting individuals are remarkably similar, even across groups, although the scales may differ substantially. ...
We examined how seabirds might be used to study marine environmental variables, which necessitates knowing location and the value of the variable to be studied. Five systems can potentially be used for determination of location: VHF (Very High Frequency) telemetry, PTT (Platform Terminal Transmitters) telemetry, GLS (Global Location Service) geolocation methods, dead reckoning and GPS (Global Positioning System), each with its own advantages with respect to accuracy, potential number of fixes and size. Temperature and light were used to illustrate potential difficulties in recording environmental variables. Systems currently used on seabirds for measurement of temperature respond slowly to environmental changes; thus, they may not measure sea surface temperature adequately when contact periods with water bodies are too short. Light can be easily measured for light extinction studies, but sensor orientation plays a large role in determining recorded values. Both problems can be corrected. The foraging behaviour of seabirds was also examined in order to identify those features which would be useful for determination of marine environmental variables at a variety of spatial and temporal scales. Area coverage by birds is highly dependent on breeding phase and tends to be concentrated in areas where prey acquisition is particularly enhanced. The identification of these sites may be of particular interest to marine biologists. 'Plungers' and 'divers' are potentially most useful for assessment of variables deeper within the water column, with some divers spending up to 90% of their time sub-surface. Few seabirds exploit the water column deeper than 20 m, although some divers regularly exceed 50 m (primarily penguins and auks), while 2 species dive in excess of 300 m. The wide-ranging behaviour of seabirds coupled, in many instances, with their substantial body size makes them potentially excellent carriers of sophisticated environmental measuring technology; however, the ethical question of how much the well-being of birds can, and should, be compromised by such an approach needs to be carefully considered.
... The longer dive duration in alcids cannot be explained by the simple oxygen store/usage hypothesis. Since hemoglobin concentration, blood volume, and myoglobin concentration in the pectoral muscles were similar in penguins and alcids, estimated oxygen stores in alcids (45–47 mL/kg; Croll et al. 1992; M. Kuroki, A. Kato, Y. Watanuki, Y. Niizuma, A. Takahashi, and Y. Naito, unpublished data) were similar to those in penguins (45–63 mL/kg; Culik et al. 1991, 1994, 1996; Kooyman et al. 1992; Kooyman and Ponganis 1994; Bethge et al. 1997). The mass-specific metabolic rate during diving in captivity was similar for alcids (13.3–17.0 ...
... W/kg; Croll et al. 1992; Croll and McLaren 1993) and penguins (9.6–20.0 W/kg; Culik et al. 1991, 1994, 1996; Kooyman et al. 1992; Kooyman and Ponganis 1994; Bethge et al. 1997). The enzyme systems in the pectoral muscles indicate that both penguins (Baldwin et al. 1984) and alcids (Davis and Guderley 1987) rely extensively on aerobic metabolism during diving, and this is also suggested by Butler and Jones (1997), although adaptations for anaerobic metabolism are found in some penguin muscles (Baldwin 1988). ...
Interspecific allometric equations for dive duration were calculated for two groups of wing-propelled divers: penguins, which specializing in diving, and alcids, which balance demands for aerial flying with those of diving. The equations for maximum dive duration (min) were 1.433M0.702 and 3.612M0.735 (where M is body mass in kilograms) for penguins (10 species) and alcids (9 species), respectively, hence did not support a simple oxygen store/usage hypothesis based on the prediction that the mass exponent of aerobic dive limit is close to 0.25. Equations for feeding dives were 0.569M0.712 and 1.094M0.391 in penguins (9 species) and alcids (10 species), respectively. The allometric exponent for the duration of feeding dives for penguins did not match the predicted value of 0.25, but that for alcids did not differ significantly from this value. Alcids exhibited a maximum dive duration 2.5 times longer than that for penguins after mass effects were controlled for. The size of oxygen stores and metabolic rates based on laboratory studies of penguins and alcids failed to explain the longer dive duration in alcids than in penguins.
... Arnott et al. 1999), the topography of the oceanic Xoor (Scolaro and Suburo 1991) and the light levels (Cannell and Cullen 1998; Ropert-Coudert et al. 2006) may also inXuence the maximum dive depths of predators. The maximum depth at which an air-breathing animal can dive also depends on a number of physiological and biomechanical variables such as haemoglobin binding capacity (Bethge et al. 1997) and buoyancy (Wilson et al. ...
... Arnott et al. 1999), the topography of the oceanic Xoor (Scolaro and Suburo 1991) and the light levels (Cannell and Cullen 1998; Ropert-Coudert et al. 2006) may also inXuence the maximum dive depths of predators. The maximum depth at which an air-breathing animal can dive also depends on a number of physiological and biomechanical variables such as haemoglobin binding capacity (Bethge et al. 1997) and buoyancy (Wilson et al. Communicated by G.F. Humphrey.1992 ...
Little Penguins, Eudyptula minor, breed in several small colonies in New Zealand and Australia. In this study, we compare the birds’ diving performances at
different sites situated throughout their breeding range. Environmental conditions and breeding success vary drastically amongst
colonies, but all birds feed on similar types of prey and face similar limitations on their foraging range. We examined several
diving parameters and calculated the proportion of foraging zone available during breeding to examine whether oceanographic
and geographic factors in the foraging zone can explain variations in diving behaviour and fledging success among the different
colonies. In colonies with high fledging success, Penguin Island and Oamaru, penguins made shallow dives <50m depth and had
lower diving effort. More than 90% of the foraging zone was in waters <50m depth in these colonies. Motuara Island also has
shallow waters with 95% <50m depth, but the fledging success was low. Phillip Island has only 42% of waters <50m and comparatively
low fledging success. Thus, penguins dived deeper and showed a higher diving effort in colonies with lower fledging success
(Motuara Island and Phillip Island), indicating that they were disadvantaged compared to conspecifics from other colonies
that dived shallower and with a lesser diving effort. We concluded that bathymetry is an important factor, but not the only
one, which influences fledging success.
... Knowledge of the foraging ecology and diving performance of penguins has been revolutionized over the last decade by the use of miniaturized electronic time±depth recorders (Wilson 1995). Because of their size-linked ability to carry attached loggers, their use has mainly been restricted to the largest (genus Aptenodytes) and medium-sized (genera Pygoscelis and Spheniscus) species , one exception being a recent work on the little penguin Eudyptula minor (Bethge et al. 1997). Crested penguins (genus Eudyptes) are the most abundant penguins , both in number of individuals and number of species. ...
... Our data on the dive durations of rockhopper penguin (Fig. 5) therefore indicate that these birds exceeded the estimated ADL in only 5% of the dives. Both the estimated behavioural ADL and frequency of anaerobic dives of rockhopper penguins are in general agreement with values obtained for the smallest and largest penguin species, namely the little (45 s and 2%) and the emperor (Aptenodytes forsteri: 8 min and 4%) penguins (Kooyman and Kooyman 1995; Bethge et al. 1997). More data are however needed on the behavioural ADL of medium-sized penguins for an accurate comparison among species. ...
The pattern and characteristics of diving in 14 female northern rockhopper penguins, Eudyptes chrysocome moseleyi, were studied at Amsterdam Island (37°50′S; 77°31′E) during the guard stage, using electronic time–depth recorders. Twenty-nine
foraging trips (27 daily foraging trips and two longer trips including one night) with a total of 16 572 dives of ≥3 m were
recorded. Females typically left the colony at dawn and returned in the late afternoon, spending an average of 12 h at sea,
during which they performed ∼550 dives. They were essentially inshore foragers (mean estimated foraging range 6 km), and mainly
preyed upon the pelagic euphausiid Thysanoessa gregaria, fishes and squid being only minor components of the diet. Mean dive depth, dive duration, and post-dive intervals were 18.4 m
(max. depth 109 m), 57 s (max. dive duration 168 s), and 21 s (37% of dive duration), respectively. Descent and ascent rates
averaged 1.2 and 1.0 ms−1 and were, together with dive duration, significantly correlated with dive depth. Birds spent 18% of their total diving time
in dives reaching 15 to 20 m, and the mean maximum diving efficiency (bottom time:dive cycle duration) occurred for dives
reaching 15 to 35 m. The most remarkable feature of diving behaviour in northern rockhopper penguins was the high percentage
of time spent diving during daily foraging trips (on average, 69% of their time at sea); this was mainly due to a high dive
frequency (∼44 dives per hour), which explained the high total vertical distance travelled during one trip (18 km on average).
Diving activity at night was greatly reduced, suggesting that, as other penguins, E. chrysocome moseleyi are essentially diurnal, and locate prey using visual cues.
... Thus, seabird feeding adaptations reflect a diverse array of foraging strategies and tactics as well (Morrison et al. 1990). In addition, foraging behaviour differs between sexes (e.g. Bethge et al. 1997; Kato et al. 2000) and age groups (e.g. Rutz et al. 2006; Daunt et al. 2007; Limmer and Becker 2009), as well as between breeding stages (i.e. ...
... This confirms a trend among central-place seabirds that face an increase in chicks' demand for food over the season, which in turn leads to greater diving effort (e.g. Williams and Rothery 1990; Bethge et al. 1997). Surprisingly, the hunting effort did not increase with chick age. ...
A complex interaction of biotic and abiotic factors influences animal foraging activity. It is often difficult to understand which factors may affect animals' foraging and how it is affected. For instance, whereas the effect of sexual dimorphism on foraging activity has been reported in several species, little is known of the complex interactions between variables acting at a finer scale, e.g. the variability of body mass within a sex. Evaluating the importance of these finer scale factors is also essential to the understanding of foraging behaviour. We propose here a simple approach by applying Principal Component Analysis (PCA) in a novel way to examine relationships between biotic and abiotic factors affecting foraging behaviour of top predators. We studied female little penguins (Eudyptula minor) of known age, carrying miniature accelerometers during the guard stage of breeding. Surprisingly, the body mass of the females did not influence any of the foraging parameters, but females foraging later in the breeding season dived shallower and more often, showing a strong correlation with laydate. Similarly, the diving effort of females was greater with increasing chick age within the same breeding stage. These results indicate that for female little penguin, the relationship between changes in prey availability and hunting effort can change at a fine scale, within a breeding stage. Therefore, any analysis of little penguin foraging behaviour during breeding should consider the timing in relation to the breeding season. We encourage researchers to develop the use of this PCA approach as it could help clarify the complexity of the underlying mechanisms determining foraging activity and we propose that it should be used as a first step of foraging behaviour analysis, before examining a particular relationship.
... Moreover, given the potential for substituting the heat of inefficiency for thermoregulation, lower efficiencies at higher contraction speeds or greater loads might have reduced impacts on total costs at cold temperatures (Hind & Gurney 1997; Chai et al. 1998). Nevertheless, a number of studies have shown that endotherms often choose to swim at certain speeds (Ponganis et al. 1990; Culik et al. 1991; Williams et al. 1993; Schmid et al. 1995; Allers & Culik 1997; Bethge et al. 1997; Pfeiffer & Culik 1998; Lovvorn et al. 2004; Watanuki et al. 2005). Work rates at these voluntary speeds presumably correspond to maximum aerobic efficiencies. ...
... Animals are expected to select speeds that minimize COT. Some species do choose to swim at speeds near their COT min (Culik et al. 1991; Williams et al. 1993; Bethge et al. 1997). However, birds and mammals in fluids often travel slower than the 'optimum' speed (Schmid et al. 1995; Allers & Culik 1997; Fish et al. 1997; Pennycuick 1997; Pfeiffer & Culik 1998; Luna-Jorquera & Culik 2000). ...
For diving endotherms, modelling costs of locomotion as a function of prey dispersion requires estimates of the costs of diving to different depths. One approach is to estimate the physical costs of locomotion (Pmech) with biomechanical models and to convert those estimates to chemical energy needs by an aerobic efficiency (eta=Pmech/Vo2) based on oxygen consumption (Vo2) in captive animals. Variations in eta with temperature depend partly on thermal substitution, whereby heat from the inefficiency of exercising muscles or the heat increment of feeding (HIF) can substitute for thermogenesis. However, measurements of substitution have ranged from lack of detection to nearly complete use of exercise heat or HIF. This inconsistency may reflect (i) problems in methods of calculating substitution, (ii) confounding mechanisms of thermoregulatory control, or (iii) varying conditions that affect heat balance and allow substitution to be expressed. At present, understanding of how heat generation is regulated, and how heat is transported among tissues during exercise, digestion, thermal challenge and breath holding, is inadequate for predicting substitution and aerobic efficiencies without direct measurements for conditions of interest. Confirming that work rates during exercise are generally conserved, and identifying temperatures at those work rates below which shivering begins, may allow better prediction of aerobic efficiencies for ecological models.
... Les Bethge et al. 1997). Il pourrait également jouer un rôle dans la ségrégation spatiale des zones d'alimentation (e.g. ...
L’océan Austral abrite encore des populations exceptionnelles de prédateurs marins (manchots, albatros, phoques…). Bien qu’activement étudiés, l’approche fonctionnelle des relations proies-prédateurs souffre encore d’un manque de connaissances chez les prédateurs marins. Etudier comment ces animaux utilisent les habitats est essentiel pour mieux comprendre leur écologie. Par ailleurs, dans une période où les écosystèmes sont soumis à d’importantes pressions d’origine anthropique (surpêche, pollutions, changement climatique), la connaissance de l’écologie d’une espèce est primordiale pour bien caractériser les aires à protéger. Le gorfou macaroni Eudyptes chrysoplophus est un oiseau marin pélagique et constitue l’espèce de manchot la plus abondante dans l’océan Austral (> 6 millions de couples). Au cours des 30 dernières années, les effectifs des populations de Géorgie du Sud et de l’île Marion ont fait face à une diminution drastique (> 30%). Actuellement, les populations de gorfou macaroni des Terres Australes et Antarctiques Françaises (archipel des îles Crozet et îles Kerguelen) abritent encore plus de 50% des effectifs mondiaux. Cependant, les comportements de recherche alimentaire de ces deux populations étaient jusqu’à présent encore mal connues. Au cours de cette thèse, nous avons étudié les stratégies de recherche alimentaire du gorfou macaroni, au cours de l’intégralité de son cycle de reproduction (incubation, élevage et crèche) de Kerguelen et Crozet, îles caractérisées par des environnements océanographiques contrastés. Les ajustements du comportement alimentaire face aux contraintes énergétiques liées à la reproduction et aux variations de la production biologique de leurs environnements ont été examinés en détail. Grace à des mesures biologiques d’origine télémétrique et/ou d’appareil embarqué (trajectoires, comportement de plongées) couplées à des données satellitaires (données environnementales), nous avons pu mettre en évidence l’existence : 1) d’un comportement de recherche alimentaire spécifique et de genre : sur les 2 sites étudiés, un ajustement similaire des déplacements, de l’effort d’approvisionnement, du régime alimentaire a été observé en réponse aux contraintes énergétiques imposées par la reproduction. En incubation, les deux sexes ciblent principalement les fronts océanographiques, les tourbillons et les zones filamentaires situées en eaux pélagiques au cours de longs trajets. En période d’élevage, les femelles s’approvisionnent plus près des côtes, majoritairement sur le plateau et au bord des talus afin de pouvoir alimenter régulièrement la progéniture. En crèche, les mâles ciblent à nouveau les structures frontales tandis que les femelles s’éloignent tout en restant inféodées aux talus. A l’aide de la littérature, nous avons pu observer que cette stratégie semble opérer à l’échelle de l’aire de répartition de l’espèce. 2) d’une plasticité phénotypique inattendue : l’approche comparative entre les îles Kerguelen et Crozet a permis d’étudier les points communs et les différences des stratégies d’approvisionnement entre les deux localités, liées aux conditions environnementales locales. Les deux populations semblent toutes deux très dépendantes des pics saisonniers de productivité primaire. En revanche, des variations d’éloignements à la colonie inter - site et intra – sexe plus importantes qu’attendues ont été observées mettant en évidence une flexibilité phénotypique insoupçonnée pour un prédateur marin pélagique. Cette étude est l’une des rares ayant couvert l’ensemble d’un cycle de reproduction chez les manchots. L’importante variabilité comportementale démontrée réitère le besoin impératif de prendre en compte l’intégralité d’un cycle pour mieux comprendre et définir les stratégies d’approvisionnement d’une espèce.
... This would allow them to increase levels of corticosterone secretion, which may help to support a high level of foraging activity (Astheimer et al., 1992) and a subsequent rapid weight gain after the moult. Another possibility is that naturally high corticosterone concentrations may provide an evolutionary advantage to little penguins because of their higher energetic requirements for foraging (Bethge et al., 1997) and smaller size, which result in a greater threat from terrestrial predators (Dann, 1992) relative to other penguins. Sampling little penguins at other life-history stages will illuminate seasonal patterns in the stress response and confirm whether little penguins demonstrate particularly high corticosterone secretion throughout their annual cycle. ...
Studies of physiology can provide important insight into how animals are coping with challenges in their environment and can signal the potential effects of exposure to human activity in both the short and long term. In this study, we measured the physiological and behavioural response of little penguins (Eudyptula minor) that were naïve to human activity over 30 min of capture and handling. We assessed relationships between corticosterone secretion, behaviour, sex and time of day in order to characterize the determinants of the natural stress response. We then compared the response of these naïve penguins with the responses of female little penguins that had been exposed to research activity (bimonthly nest check and weighing) and to both research activity (monthly nest check and weighing) and evening viewing by tourists. We found that corticosterone concentrations increased significantly over 30 min of capture, with naïve penguins demonstrating a more acute stress response during the day than at night. Penguins that had previously been exposed to handling at the research and research/ visitor sites showed elevated corticosterone concentrations and consistently more aggressive behaviour after 30 min com- pared with naïve birds, although there were no significant differences in baseline corticosterone concentrations. Our findings demonstrate that these little penguins have not habituated to routine capture, but rather mount a heightened physiological and behavioural response to handling by humans. Less invasive research monitoring techniques, such as individual identifica- tion with PIT tags and automatic recording and weighing, and a reduction in handling during the day should be considered to mitigate some of the potentially negative effects of disturbance. Given the paucity of data on the long-term consequences of heightened stress on animal physiology, our study highlights the need for further investigation of the relationship between the corticosterone stress response and fitness outcomes, such as breeding success and survival.
... Variation in either of these two parameters will alter predictions accordingly. Irrespective of the extent to which swim speed genuinely varies between male and female harbour seals, it is clear that speed is an important variable needed in discussions of niche partitioning, both inter-and intra-specifically, most particularly because the power required to swim underwater increases approximately as a cube of the swim speed (e.g., Boyd et al., 1995; Culik et al., 1996; Bethge et al., 1997). Higher swim speeds may take one gender away from minimum costs of transport, reducing dive duration, as observed here. ...
Colonial pinnipeds may be subject to substantial consumptive competition because they are large, slow-moving central place foragers. We examined possible mechanisms for reducing this competition by examining the diving behaviour of harbour seals (Phoca vitulina) after equipping 34 seals (11 females, 23 males) foraging from three locations; Rømø, Denmark and Lorenzenplate and Helgoland, Germany, in the Wadden Sea area with time-depth recorders. Analysis of 319,021 dives revealed little between-colony variation but appreciable inter-sex differences, with males diving deeper than females, but for shorter periods. Males also had higher vertical descent rates. This result suggests that males may have higher overall swim speeds, which would increase higher oxygen consumption, and may explain the shorter dive durations compared to females. Intersex variation in swim speed alone is predicted to lead to fundamental differences in the time use of three-dimensional space, which may help reduce consumptive competition in harbour seals and other colonial pinnipeds.
... In Australia, little penguins have small foraging ranges (<20 km; Collins et al. 1999) and are generalist consumers, eating a diversity of prey items including fish, cephalopods, and crustaceans, but concentrating on nutritionally valuable species such as pilchards (Sardinops sp.) and anchovies (Engraulis australis; Klomp & Wooller 1988;. A limited aerobic capacity and small gape size restrict little penguins to feeding on small, pelagic schooling fish, no deeper than ~70 m ( Bethge et al. 1997;Ropert-Coudert et al. 2006). Diet composition typically varies between penguin colonies as a consequence of their small foraging range and varying abundances of their preferred prey, which are influenced by local conditions such as ocean temperature and bathymetry (Gales & Pemberton 1990;Cullen et al. 1991;Chiaradia et al. 2007Chiaradia et al. , 2012. ...
At-sea shifts in food quality and availability can affect populations of marine birds; however, it is difficult to evaluate the impacts of changes in prey composition and availability without some baseline information on diet composition. The little penguin (Eudyptula minor) is a common inshore-feeding seabird in New Zealand and Australia. To date, only two dietary studies have been undertaken on the little penguin in New Zealand, at two widely separated locations. This study recorded diet of little penguins during the chick- rearing stage of breeding at three colonies in southern New Zealand. Sixty-nine stomach samples were acquired via the stomach flushing technique at Banks Peninsula, Oamaru, and Stewart Island. Prey composition differed between each site: (1) at Oamaru, Graham’s gudgeon (Grahamichthys radiata) occurred most frequently (100%) and contributed the most to meal mass (92.1%); (2) at Banks Peninsula arrow squid (Nototodarus sloanii) occurred most frequently (87.5%), but two fish species – slender sprat (Sprattus antipodum) (33.9%) and ahuru (Auchenoceros punctatus) (37.4%) – contributed most to meal mass; and (3) at Stewart Island arrow squid occurred most frequently (91.3%), and contributed most to meal mass (73.1%). Little penguins take a wide diversity of species, and may switch between species, probably in response to temporal variation in availability. In New Zealand, little penguins ate higher proportions of lower quality cephalopods than those in Australia. As top predators in the marine ecosystem, changes in little penguin diet may indicate changes occurring in the inshore marine ecosystem.
... gentoo penguins Pygoscelis papua, Volkman et al. 1980; Adélie penguins P. adeliae, Ainley & Emison 1972 ), and the larger sex usually dives deeper, presumably because of the allometry of diving capacities (e.g. little penguins Eudyptula minor Bethge et al. 1997, Halsey et al. 2006). Potential divergences in foraging areas between males and females have been suggested by stable isotope studies (e.g. ...
Sexual differences in at-sea behaviour of seabirds often derive from size dimorphism and may lead to both resource partitioning and diverging threats between the sexes. Spheniscids are one of the least dimorphic of the seabird families, and the most threatened. In many instances, diet differs between the sexes in penguins, but few studies have compared their foraging behaviour, partly because of the difficulty of identifying sexes in the field. We derived a discriminant function analysis that predicts the sex of African penguins Spheniscus demersus with >90 % confidence using only beak length and depth. We also deployed GPS-time-depth recorders on male and female penguins breeding on two of their largest colonies in South Africa over two consecutive breeding seasons and compared their at-sea behaviour. Foraging effort (time spent at sea, distance covered) varied more importantly with clutch mass and between years and colonies than between sexes. However, although maximum diving capabilities were similar, males dived deeper and longer on average than females. Females compensated by increasing their diving frequency, which resulted in similar volumes of water being explored, and foraged over larger foraging areas. There was also some spatial separation between sexes, though foraging range overlap differed markedly (35-83%) between years and islands, presumably reflecting prey availability and the need to minimise between-sex competition. The results suggest potential niche partitioning between the sexes in African penguins, but could also be a passive consequence of sexual dimorphism driven primarily by sexual selection. Female behaviour may make them more at risk from predation or oiling events, highlighting the possibility of sex-dependent vulnerability in this Endangered species.
... Underestimations of TADL have been suggested for many free-ranging seabirds (Croll et al. 1992; Kooyman & Ponganis 1998; Knower Stockard et al. 2005; Elliot et al. 2010; Ponganis et al. 2010). One reason suggested for this has been the overestimation of oxygen consumption rates during diving measured in shallow canals or swim tanks with high buoyancy effects (Croll & Maclaren 1993; Culik et al. 1994; Schmid et al. 1995; Bethge et al. 1997 ). Another possibility was hypothermia in the periphery, which reduces the metabolic rate during free-ranging dives (Butler & Jones 1997; Niizuma et al. 2007 ). ...
Alcids dive longer than are predicted by their body size alone, but the physiological mechanisms that explain their excellent diving capabilities are poorly understood. In this study, we estimated the oxygen stores of Rhinoceros Auklets Cerorhinca monocerata, medium-sized alcids that attained depths down to 62 m within 2.5 min. Hematocrit was 43.9±2.8%, hemoglobin concentration was 17.2±4.6 g·100 ml-1, and blood volume was 12.7±1.9% of their body mass. Myoglobin concentration in breast muscle (1.8±0.3 g·100 g-1) was higher than that in leg muscle (1.2±0.2 g·100 g-1). Rhinoceros Auklets have higher blood volume, hemoglobin and myoglobin concentrations, as do other flying/diving seabirds (other alcids and cormorants), than flying/non-diving seabirds (terns and kittiwakes). The oxygen store of Rhinoceros Auklets was estimated at 54.5 ml·kg-1. Using the average oxygen consumption rate of diving seabirds (1.01 ml·s 1·kg1), we calculated their theoretical aerobic dive limit (TADL) as 53.9 s. Nearly half of their dives (47.2%) exceeded their TADL, because an overestimation of their oxygen consumption rate during diving resulted in an underestimation of TADL.
... Although externally attached loggers potentially have an impact on the swimming ability, reducing speed (Wilson et al. 1986) and modifying the diving behavior of even large-sized penguins (Ropert-Coudert et al. 2000), the impact of the loggers on a bird's foraging behavior is reduced if certain precautions are followed (Ballard et al. 2001). Bethge et al. (1997), using loggers with a frontal area less than 2% of the bird's crosssection area, showed that overall the bird's swim speed was little affected by the presence of the device. Although devices may affect foraging parameters other than speed, the hydro-dynamically shaped loggers in our study were less than 2% of the bird's crosssection area. ...
Data on the diving activity of the Little Penguin (Eudyptula minor) as recorded by data loggers are few. We monitored the foraging parameters of free-ranging Little Penguins, breeding at Penguin Island, Western Australia, using a small, hydrodynamically shaped time-depth recorder. Data were obtained for one, two and three consecutive foraging trips of three, one and two birds, respectively. These data showed that individual Little Penguins presented distinct diving depths that are consistent from one trip to the next. Four birds exploited shallow depths, around 1-5 m, but two other birds always chose to dive deeper, to around 8-10 m. No trends could be established between the adult mass or the chick mass and the preferred diving depths. The causes and consequences of these individual diving strategies are discussed.
... This penguin breeds on offshore islands from the southwest coast of Western Australia, across the southern coast (including Tasmania) and up the eastern coast of mainland Australia as far north as South Solitary Island, and on to New Zealand and the Chatham Islands in the east (Marchant & Higgins 1990). It is the smallest species of penguin, averaging 30 cm in height and 1 kg in body mass, giving it a reduced swimming speed when compared to other penguin species (Bethge et al. 1997 ). This, coupled with the limited fasting and thermoregulatory capabilities of its chicks (foraging trips during the chick-guard phase of breeding typically last only 1 d; Chiaradia & Nisbet 2006 ) means that, during breeding , little penguins have a restricted foraging range in comparison to most seabirds (Dann & Norman 2006 ). ...
Knowledge of the foraging areas of top marine predators and the factors influencing them is central to understanding how their populations respond to environmental variability. While there is a large body of literature documenting the association of air-breathing marine vertebrates with areas of high marine productivity, there is relatively little information for species restricted to near-shore or continental-shelf areas. Differences in foraging range and diving behaviour of the little penguin Eudyptula minor were examined from 3 breeding colonies (Rabbit Island, Kanowna Island and Phillip Island) in central northern Bass Strait, southeast Australia, during the chick-guard stage using electronic tags (platform terminal transmitters, PTTs, and time-depth recorders, TDRs). Although there were large overall differences between individuals, the mean maximum foraging range (16.9 to 19.8 km) and mean total distance travelled (41.8 to 48.0 km) were similar between the 3 colonies, despite different bathymetric environments. Individuals from all 3 colonies selected foraging habitats within a narrow sea surface temperature (SST) range (16.0 to 16.4 degrees C). While there were significant differences in mean dive depths (5.4 to 10.9 m) and mean durations (13.2 to 28.6 s) between the different colonies, the mean diving effort (vertical distance travelled: 936.3 to 964.3 m h(-1)) was similar. These findings suggest little penguins from the 3 colonies employ relatively similar foraging efforts yet are plastic in their foraging behaviours.
... In general, males fed larger meals to the chicks than females during our 8 years of study. Sex-biased meal size may result from differences in diving behavior as males are able to dive deeper and longer than females (Bethge et al. 1997; Yorke et al. 2004). To avoid the confounding effect of sex and high/low contributor status, we analyzed separately pairs with mothers as the high contributors and pairs with fathers as the high contributors. ...
According to life-history theory, individuals optimize their decisions in order to maximize their fitness. This raises a conflict between parents, which need to cooperate to ensure the propagation of their genes but at the same time need to minimize the associated costs. Trading-off between benefits and costs of a reproduction is one of the major forces driving demographic trends and has shaped several different parental care strategies. Using little penguins (Eudyptula minor) as a model, we investigated whether individuals of a pair provide equal parental effort when raising offspring and whether their behavior was consistent over 8 years of contrasting resource availability. Using an automated identification system, we found that 72% of little penguin pairs exhibited unforced (i.e., that did not result from desertion of 1 parent) unequal partnership through the postguard stage. This proportion was lower in favorable years. Although being an equal pair appeared to be a better strategy, it was nonetheless the least often observed. Individuals that contributed less than their partner were not less experienced (measured by age), and gender did not explain differences between partners. Furthermore, birds that contributed little or that contributed a lot tended to be consistent in their level of contribution across years. We suggest that unequal effort during breeding may reflect differences in individual quality, and we encourage future studies on parental care to consider this consistent low and high contributor behavior when investigating differences in pair investment into its offspring. Copyright 2011, Oxford University Press.
... For many dimorphic species, the differences in foraging behavior between the sexes are continuations of size-related differences in foraging behavior that occur within each sex (e.g., Zavalaga et al. 2007). For example, larger marine animals can dive deeper, catch larger prey, or exclude smaller conspecifics from foraging areas (Halsey et al. 2006; mammals: Beck et al. 2003; Baird et al. 2005; Page et al. 2005; penguins: Bethge et al. 1997; Clarke et al. 1998; cormorants: Kato et al. 2000; Ishikawa and Watanuki 2002; Cook et al. 2007; boobies: Weimerskirch et al. 2006; albatrosses: Weimerskirch et al. 1997). Nonetheless, if sex-specific differences in foraging were driven by sex-specific differences in form through competition or efficiency, then, we would not expect there to be sex-specific differences in foraging in monomorphic animals. ...
The presence of sex-stereotyped behavior in monomorphic animals, where there are no sexual differences in form to account for sexual differences in function, is often attributed to intraspecific competition or to differential parental investment. The possibility that the use of different behavioral strategies by each parent may increase reproductive success for both partners through risk partitioning is seldom considered. We studied thick-billed murres (Uria lomvia), where the male exclusively feeds the offspring during the late chick rearing. During the period of biparental care, males fed on "risk-averse" prey (consistent across time and space; unitized risk = 0.29), whereas females fed on "risk-prone" prey (risk = 0.59). Males fed at night at 1 colony, during the day at 2 colonies, and there was no pattern at another colony. We suggest that these differences reflect the availability of risk-prone prey. Modeling suggested that mixed-risk pairs had higher success than "risky" or "riskless" pairs. Males accumulated reserves and reduced chick provisioning just prior to fledging. Thus, sex-specific patterns at 1 period (male-only care during postfledging) may have led to sex-specific patterns at earlier periods through the need for specialization in foraging habits and risk. We propose that risk partitioning may contribute to the prevalence of sex-specific behaviors in monomorphic animals and that patterns are likely context specific rather than species specific. Copyright 2010, Oxford University Press.
... Additionally, previous studies examined a number of band types (Petersen et al. 2005), differing in material and size depending on the species on which they were used. Little penguins (Eudyptula minor) are the smallest (900– 1,300 g) penguin species and are a suitable model for such investigations, because their diving energy requirements are greater than those of all other species of penguin (Bethge et al. 1997). The energetic expenditure of little penguins at sea increases from 3.1 3 FMR (field metabolic rate) to 5.2 3 FMR in late chick-rearing (Butler and Jones 1997). ...
Flipper banding has long been the primary method to identify individual penguins, despite studies indicating that it may be detrimental to breeding success and survival. Our objectives were to measure the effects that flipper bands may have on diving performance of little penguins to determine whether the bands may be detrimental. We studied short- and long-term direct effects of flipper banding on diving behavior of free-ranging little penguins (Eudyptula minor) by comparing diving behavior before and after banding and by comparing diving performance of unbanded birds to those that had carried flipper bands for several years, respectively. Recently banded birds displayed increases in multiple variables following banding. Long-term banded penguins did not exhibit differences to their unbanded counterparts in most variables examined. Our findings are useful to those considering or reviewing the use of bands in penguin study and management.
... During guard phase, breeding little penguins make one-day foraging trips since they alternate daily to attend small chicks of up to three weeks old [18]. Thus age-related differences in foraging performance would not be masked by foraging trip duration and sexual differences [19]. From November to December 2005 we equipped 19 breeding females with miniature accelerometers to monitor their foraging activity (M190-D2GT, Little Leonardo, Tokyo, Japan). ...
Age-related changes in breeding performance are likely to be mediated through changes in parental foraging performance. We investigated the relationship of foraging performance with age in female little penguins at Phillip Island, Australia, during the guard phase of the 2005 breeding season. Foraging parameters were recorded with accelerometers for birds grouped into three age-classes: (1) young, (2) middle age and (3) old females. We found the diving behaviour of middle-aged birds differed from young and old birds. The dive duration of middle age females was shorter than that of young and old birds while their dive effort (measure for dive and post-dive duration relation) was lower than that of young ones, suggesting middle-aged birds were in better physical condition than other ones. There was no difference in prey pursuit frequency or duration between age classes, but in the hunting tactic. Females pursued more prey around and after reaching the maximum depth of dives the more experienced they were (old > middle age > young), an energy saving hunting tactic by probably taking advantage of up-thrust momentum. We suggest middle age penguins forage better than young or old ones because good physical condition and foraging experience could act simultaneously.
... Here, oxygen use equates linearly with energy expenditure (Stahel and Nicol, 1987). In addition, there are good quality data on energy expenditure in penguins (Bethge et al., 1997; Culik et al., 1996; Culik et al., 1994; Luna-Jorquera and Culik, 2000) that lend credibility to the modelling exercise. ...
Animals respond to environmental variation by exhibiting a number of different behaviours and/or rates of activity, which result in corresponding variation in energy expenditure. Successful animals generally maximize efficiency or rate of energy gain through foraging. Quantification of all features that modulate energy expenditure can theoretically be modelled as an animal energetic niche or power envelope; with total power being represented by the vertical axis and n-dimensional horizontal axes representing extents of processes that affect energy expenditure. Such an energetic niche could be used to assess the energetic consequences of animals adopting particular behaviours under various environmental conditions. This value of this approach was tested by constructing a simple mechanistic energetics model based on data collected from recording devices deployed on 41 free-living Magellanic penguins (Spheniscus magellanicus), foraging from four different colonies in Argentina and consequently catching four different types of prey. Energy expenditure was calculated as a function of total distance swum underwater (horizontal axis 1) and maximum depth reached (horizontal axis 2). The resultant power envelope was invariant, irrespective of colony location, but penguins from the different colonies tended to use different areas of the envelope. The different colony solutions appeared to represent particular behavioural options for exploiting the available prey and demonstrate how penguins respond to environmental circumstance (prey distribution), the energetic consequences that this has for them, and how this affects the balance of energy acquisition through foraging and expenditure strategy.
At the Gannet Islands, Labrador, sympatric thick-billed murres (Uria lomvia (L., 1758)) and razorbills (Alca torda L., 1758) are slightly sexually dimorphic and have similar intersexual differences in parental roles females are the main meal providers and males are mostly involved in brooding and chick defence at the breeding site and at sea. The question is whether differences in parental roles influence the foraging behaviour patterns of males and females. Murre females foraged during twilight periods and dived shallower than males. In razorbills, although sex differences were not as clear, females also tended to dive shallower (<10m) and more often at twilight. Males of both species foraged during daylight hours and tended to dive deeper than females. Females of both species had shorter dive bouts (i.e., duration of a series of dives) even though the number of bouts and dives per day were equal between sexes. In both species, female dives were mostly shallower W-shaped dives, likely for capturing crustaceans at twilight. In contrast, males performed mostly deeper U-shaped dives for capturing mid-water species (e.g., capelin, Mallotus villosus (Mller, 1776)). Altogether, our results show that the two sympatric auks had relatively similar intersexual segregation in feeding time, depth, and prey. Sex differences in nest attendance, driven by differences in parental roles, seem to explain these findings.
A female Little Penguin Eudyptula minor breeding at Phillip Island, Australia dived to the exceptional depth of 66.7 m, as recorded by a depth and acceleration data logger in November 2005. The dive lasted 90 s and reached the maximum theoretical depth for a penguin of this size. The closest maximum depth recorded for 37 other birds was 57 m and very few penguins attained a depth of more than 50 m. Observations of flipper-beat activity, body angle and water temperature during the course of the dive highlight several outcomes of deep diving by Little Penguins and help explain how such deep dives are achieved.
Buoyancy is a major determinant of locomotory cost in diving animals. As seabirds have a large amount of air in their feathers and respiratory system, they should work hard against buoyancy to descend in the water column. Since buoyancy decreases with increasing hydrostatic pressure, shallow divers, especially, should work against buoyancy during both the descent and bottom phases of their dives. We deployed miniaturised depth and acceleration recorders on free-ranging, foot-propelled divers (great cormorants Phalacrocorax carbo) and flipper-propelled divers (little penguins Eudyptula minor) foraging in shallow waters, where both are positively buoyant. We monitored the diving strategies of the birds to assess how they manage to counteract buoyancy using 2 alternative locomotory modes. Cormorants decreased the stroke frequency and surge amplitude during descent and maintained constant swim speed. In contrast, penguins did not change their stroke frequency or heave amplitude; as a result, their swim speed increased during the descent phase. During the bottom phase, cormorants had a low stroke frequency and tilted towards the bottom, while penguins actively stroked in a horizontal position. Furthermore, intensive acceleration periods during the bottom phase were often recorded for penguins, but rarely for cormorants. Great cormorants and little penguins used different strategies to feed underwater. Great cormorants, having lower specific buoyancy, were less active than little penguins, thus adopting an energy-saving strategy. We conclude that both foot- and wing-propelled birds diving in shallow waters have developed efficient locomotory strategies to counteract buoyancy, these alternative characteristics being linked to different foraging niches.
The published literature on the effects of flipper‐bands on penguin ecology is reviewed. Six published studies show the following.
In Adélie Penguins Pygoscelis adeliae , flipper‐bands directly damaged flippers, increased swimming costs by 24%, decreased survival in the first year after banding by 28%, and may have accelerated decline of a dwindling colony by 3%.
Adult return rates to colonies among flipper‐banded Adélie, Chinstrap P. antarctica and Gentoo P. papua Penguins decreased by 8%, 12% and 25%, respectively, between single‐ and double‐banded penguins. Juvenile return rates among Gentoo Penguins were reduced by 10·5%. Return rates to the colony among double‐banded King Penguins Aptenodytes patagonicus were 31·3% and 6·7% lower than among single‐banded birds in the first and second years after banding, respectively, and single flipper‐banded birds showed annual survival rates 21·1% lower than those of birds fitted with subcutaneous transponders.
Among Royal Penguins Eudyptes schlegeli , there were no differences between chick growth, adult over‐winter survival and fledging success between flipper‐banded birds and birds fitted with transponders.
Adélie Penguin adult annual survival rates were lower among flipper‐banded birds than among unbanded birds.
On the basis of dive profiles for Adélie Penguins, it is estimated that increased swimming costs of 5% reduce prey contact time by 10%, and of 24% reduce prey contact time by 48%. These estimated ‘knock‐on’ or cumulative costs coupled with the survival and breeding costs shown by the majority of published field studies suggest that data collected on some flipper‐banded populations are biased.
The advantages and disadvantages of an alternative long‐term marking technique, subcutaneously implanted passively interrogated transponder tags, are discussed. Research projects currently testing transponders and flipper‐bands worldwide are listed.
The speed at which air-breathing marine predators that forage by diving should swim is likely to depend on a variety of factors that differ substantially from those relevant in animals for which access to oxygen is unlimited. We used loggers attached to free-living penguins to examine the speed at which three species swam during periods searching for prey and compared this to their speeds during actual prey pursuit. All penguin species appeared to travel at similar speeds around 2 m/s during normal commuting between the surface and feeding depths, which accords closely with minimum costs of transport. However, Adélie penguins, Pygoscelis adeliae, slowed down to feed, Magellanic penguins, Spheniscus magellanicus, speeded up and king penguins, Aptenodytes patagonicus, travelled at a variety of speeds, although mean speed did not change from normal commuting. Since energy expenditure, and therefore oxygen usage, in swimming animals increases with the cube of the speed, we hypothesized that prey escape speed (a function of prey size) and prey density would prove critical in determining optimum pursuit speeds in predators. Simple models of this type help explain why it is that some penguin species apparently benefit by increasing speed to capture prey while others benefit by decreasing speed.
Diving is believed to be very costly in cormorants (Phalacrocoracidae) when compared with other avian divers because of their poor insulation and less-efficient foot propulsion. It was therefore suggested that cormorants might employ a behavioural strategy to reduce daily energy expenditure by minimizing the amount of time spent in water. However, European shags (Phalacrocorax aristotelis) have been observed to spend up to 7 h day(-1) diving in water of around 5-6 degrees C. To gain a better understanding of the energetic requirements in European shags, we measured their metabolic rates when resting in air/water and during shallow diving using respirometry. To investigate the effects of water temperature and feeding status on metabolic rate, birds dived at water temperatures ranging from 5 to 13 degrees C in both post-absorptive and absorptive states. In parallel with respirometry, stomach temperature loggers were deployed to monitor body temperature. Basal metabolic rate (BMR) was almost identical to allometric predictions at 4.73 W kg(-1). Metabolic rate when resting on water, during diving and after feeding was significantly elevated when compared with the resting-in-air rate. During diving, the metabolic rate of post-absorptive shags increased to 22.66 W kg(-1), which corresponds to 4.8x BMR. Minimum cost of transport (COT) was calculated at 17.8 J kg(-1) m(-1) at a swim speed of 1.3 m s(-1). Feeding before diving elevated diving metabolic rate by 13% for up to 5 h. There was a significant relationship between diving metabolic rate and water temperature, where metabolic rate increased as water temperature declined. Thermal conductance when resting in air at 10-19 degrees C was 2.05 W m(-2) degrees C(-1) and quadrupled during diving (7.88 W m(-2) degrees C(-1)). Stomach temperature when resting in air during the day was 40.6 degrees C and increased during activity. In dive trials lasting up to 50 min, stomach temperature fluctuated around a peak value of 42.0 degrees C. Hence, there is no evidence that European shags might employ a strategy of regional hypothermia. The energetic costs during shallow diving in European shags are considerably lower than has previously been reported for great cormorants (Phalacrocorax carbo) and are comparable to other foot-propelled divers. The lower dive costs in shags might be the consequence of a more streamlined body shape reducing hydrodynamic costs as well as a greater insulative plumage air layer (estimated to be 2.71 mm), which reduces thermoregulatory costs. The latter might be of great importance for shags especially during winter when they spend extended periods foraging in cold water.
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