Air-breathing diving animals are capable of maintaining activity during prolonged dives fuelled by on-board oxygen stores. Leatherback turtles (Dermochelys coriacea) perform the deepest and longest dives among sea turtles, and are among the most prolific air-breathing divers. Here we report the longest dive duration for D. coriacea during an extremely deep dive (1186 m) that lasted 86.5 minutes. This dive duration exceeded previously published calculated aerobic dive limits by almost two-fold and extends our knowledge of the diving capacity of this species.

Solitary wild bottlenose dolphins and man frequenting the same small areas makes boat interaction more or less inevitable. Here we provide the first quantified data about solitary bottlenose dolphin diving behaviour in the presence and absence of boats. Over 110 hours were spent observing a solitary bottlenose dolphin within a 6 km2 bay on the north-western coast of Spain from April to August 2005. A generalized linear mixed model explaining 77.3% of the variability of duration of dives indicated that the animal did not vary its diving activity in function of the presence of boats. However, the length of dives was related with the behavioural events prior to dive. Dolphin activity was characterized by mean dive intervals (mean = 62.6 seconds) related to a predominance of foraging behaviour. Because of the frequent presence of boats and the manner in which they moved, the dolphin may have become accustomed to their presence. The data reported here could be used to implement precautionary management proposals that take into account the potential effects of boat presence on bottlenose dolphins.

We compared, for the first time the foraging ecology of both sexes of the blue-eyed Crozet shag (Phalacrocorax melanogenis), using ventrally attached time depth recorders to investigate differences in time-budget and diving behaviour between the sexes during the chick-rearing. Males were the only ones to dive over 55 m. Females dived mostly between 15 and 35 m, a zone poorly used by males. Females foraged mostly in the morning and males in the afternoon. Females also spent one hour longer diving per day compared to males. There were differences in diving strategies and diet, indicating that both sexes targeted essentially the same prey, but of different sizes, males specializing in bigger fish. Although the relationship between sexual dimorphism and diving depth was positive (larger animals diving deeper), evidence suggests that body size (in terms of oxygen storage capacity) is not sufficient to explain so many differences in foraging ecology. Instead, we propose prey size (possibly driven by a limitation of prey handling ability in relation to beak size) could be an essential factor in shaping the male/female behavioural segregation in the Crozet shag; future studies should concentrate on this particular aspect.

Time-depth recorders were used to investigate the diving performance and behaviour of two bimodally respiring turtle species, Rheodytes leukops and Emydura macquarii, known to have a high and low reliance on aquatic respiration, respectively. Significant differences in diving performance between R. leukops and E. macquarii were observed in the number of dives/day (39.3±5.38 vs 112.2±11.73 dives/day; mean±se), mean dive length (33.1±7.33 min vs 9.6±2.26 min) and maximum dive length (623±104.74 min vs 67.1±8.14 min), respectively. Differences in diving performance between R. leukops and E. macquarii are attributed to the species' reliance (or lack thereof) upon aquatic respiration. Rheodytes leukops displayed a weak bimodal pattern of increased surfacing frequency in the early morning (05:00–07:00) and late afternoon (14:00–18:00), while E. macquarii displayed a strong bimodal pattern of elevated surfacing frequency over similar time periods. Daily patterns of increased surfacing frequency for both species failed to correlate with fluctuating aquatic Po2 levels or water temperature, and may instead be explained by the heightened activity levels of both species during twilight.

The foraging behaviour of Brünnich's guillemots Uria lomvia was studied in a high-arctic fjord system (Kongsfjorden) in western Spitsbergen. The physical oceanographic characteristics of the water change from the head of the fjord and westward into the Greenland Sea, and are reflected in the vertical profiles of water temperatures in different parts of the area. Nine chick-rearing Brünnich's guillemots were instrumented with temperature-depth recorders, which generated vertical temperature profiles of the dives. These were compared to synoptic measurements of the water temperature characteristics of the region. This method was used to locate the foraging areas of the Brünnich's guillemots and to study the foraging site fidelity of individual birds. The results showed that only three of the nine birds foraged outside Kongsfjorden during the study period, and only 26 of the 186 dive bouts (14%) were conducted outside the fjord, 48–58 km from the colony. Most dives were probably made only a few kilometres from the colony. The data indicate that the birds showed strong fidelity to foraging areas at spatial scales of 1–20 km. However, the birds sometimes moved between feeding areas characterized by different vertical temperature profiles. The guillemots made 2229 dives during the study period and spent c. 10% of their time under water. The diving depth averaged 45 m, and the dive duration averaged 97 s. The deepest dive recorded was 136 m and lasted 196 s. We did not find any diel rhythm in the diving depths of the Brünnich's guillemots. Also, we found no diel pattern in diving frequency. These findings contradict the predominance of night-time diving observed in studies of guillemots undertaken further south.

The foraging behaviour of Cape clawless otters Aonyx capensis was investigated. Factors included: duration of dives, recovery times, processing times, hunting success, per cent time at the surface, and time foraging before each catch. Observations were made during the day on solitary adult A. capensis in a marine environment in False Bay, South Africa. There were significant differences in duration of unsuccessful dives, recovery times, and processing times as well as successful dives with various depths. Aonyx capensis prefer hunting at depths of 0.5–1.5 m. This is despite having a higher hunting success, catching larger, more energy-rich prey (fish), and shortest time foraging per catch, at depths of 1.5–2.5 m. Some of the data presented support the optimal breathing hypothesis, which predicts that both surface and dive times should increase for dives of greater depths. However, diving efficiency does not decrease with increasing depth, and percentage time at the surface does not increase with increasing depth. These are contrary to the optimal breathing hypothesis.