The diving behaviour of mammal-eating killer whales (Orcinus orca): variations with ecological not physiological factors

Mammal-eating killer whales (Orcinus orca (L., 1758)) are a rare example of social predators that hunt together in groups of sexually dimorphic adults and juveniles with diverse physiological diving capacities. Day–night ecological differences should also affect diving as their prey show diel variation in activity and mammal-eating killer whales do not rely on echolocation for prey detection. Our objective was to explore the extent to which physiological aerobic capacities versus ecological factors shape the diving behaviour of this breath-hold diver. We used suction-cup-attached depth recorders (Dtags) to record 7608 dives of 11 animals in southeast Alaska. Analysis of dive sequences revealed a strong bout structure in both dive depth and duration. Day–night comparisons revealed reduced rates of deep dives, longer shallow dives, and shallower long-duration dives at night. In contrast, dive variables did not differ by age–sex class. Estimates of the aerobic dive limit (cADL) suggest that juveniles exceeded their cADL during as much as 15% of long dives, whereas adult males and females never exceeded their cADL. Mammal-eating killer whales in this area appear to employ a strategy of physiological compromise, with smaller group members diving nearer their physiological limits and large-bodied males scaling down their physiological performance

Water flux and estimated metabolism of free-ranging gentoo and macaroni penguins at South Georgia

Water turnover rates were measured in gentoo and macaroni penguins breeding sympatrically on South Georgia Island. At the time of this study, adult male macaronis were attending the nest while female macaronis and both sexes of adult gentoos were making regular foraging trips to sea and returning to feed their chicks. Both species feed principally on krill, Euphausia superba, although gentoos also feed on fish. The average water turnover rate in 2 fasting male macaronis was 12.5 ml·kg-1·day-1 with a half-time for water turnover of 36 days. The mean water flux rate in feeding birds was 155 ml·kg-1·day-1 in gentoos and 184 ml·kg-1·day-1 in macaronis. The half-times for water turnover were 2.8 days, and 2.6 days, respectively. The average metabolic rate of fasting macaronis calculated from water turnover rates was 5.6 W·kg-1 or 1.8 x the standard metabolic rate (SMR). In order to calculate prey consumption and average daily metabolic rate (ADMR) from water flux rates in feeding birds, it was assumed that a) the only sources of water are from metabolism and performed water in the diet and b) the composition of the diet is known. Based on the type of prey consumed, the calculated ADMR was 7.1 W·kg-1 or 2.6×SMR (n=5) for gentoos and 9.1 W·kg-1 or 2.9×SMR (n=3) for macaronis. The ADMR of female macaronis making regular trips to sea was 1.6 x greater than the fasting metabolism of males brooding the chick

Diving depths and energy requirements of king penguins

During 4- to 8-day periods at sea, half of 2595 dives of three king penguins were more than 50 meters and two dives exceeded 240 meters. The at-sea metabolic rate, estimated from the turnover of tritiated water, was 2.8 times the standard metabolic rate and requires about 2.5 kilograms of squid per day. Ten percent or less of the dives may result in prey capture

Indirekte Tierbeobachtung mit elektronischen Instrumenten: Biotelemetrie

Wikelski M, Trillmich F. Indirekte Tierbeobachtung mit elektronischen Instrumenten: Biotelemetrie. In: Naguib M, ed. Methoden der Verhaltensbiologie. Heidelberg: Springer; 2006: 175-179

Diving behavior and energetics during foraging cycles in king penguins

King Penguins are the second largest of all diving birds and share with their congener, Emperor Penguins, breeding habits strikingly different from other penguins. Our purpose was to determine the feeding behavior, energetics of foraging and the prey species, and compare these to other sympatric species of subantarctic divers. We determined: (1) general features of foraging behavior using time—depth recorders, velocity meters, and radio transmitters, (2) energetics by doubly labeled water, (3) food habits and energy content from stomach lavage samples, and (4) resting and swimming metabolic rate by oxygen consumption measurements. The average foraging cycle was ≈6 d, during which the mass gain of 30 birds was ≈2 kg. When at sea, the birds exhibit a marked pattern of shallow dives during the night, whereas deep dives of >100 m only occurred during the day. Maximum depth measured from 34 birds and 18 537 dives was 304 m, and maximum dive duration from 23 birds and 11 874 dives was 7.7 min. The frequency distribution of dive depth was bimodal, with few dives between 40 and 100 m. Overall, swim velocities when a bird was at sea averaged 2.1 m/s (N = 5), while descent and ascent rates of change in depth averaged 0.6 m/s for dives 150 m (N = 90). Night feeding dives occurred at a rate of ≈20 dives/h, and deep dives occurred at a rate of ≈5 dives/h. The energy consumption rate while resting ashore was 3.3 W/kg (N = 3) or 1.6 times the predicted standard metabolic rate (SMR). The average energy consumption rate while away from the colony was 10 W/kg (N = 8) or 4.6 x SMR, compared to 4.3 x SMR estimated from a time—energy budget. The latter value is based on an average metabolic rate of 4.2 W/kg for three birds while resting in 5°C water and 9.6 W/kg while swimming at 2 m/s, which was extrapolated from the average of three birds swimming at 1 m/s. The average energy intake based on 9 stomach content samples was nearly 24.6 kJ/g dry mass. The main prey by number are myctophid fish of the species Krefftichthys anderssoni and Electrona carlsbergi. It was concluded that: (1) feeding begins ≈28 km from the colony, (2) prey is pursued night and day through its vertical movements, (3) vertical distribution of the prey is reflected closely by diving habits of the birds, (4) deep—diving, for unknown reasons, is an important component of foraging success, (5) diving capacities of King Penguins are remarkable compared to other birds and many pinnipeds, and (6) calculated foraging energetics can be closely estimated from time—energy budgets