Comparative diving patterns of pinnipeds and seabirds

General ecological information resulting from modern dive studies has been limited because analyses and conclusions are study- and species-specific. I n this work, a series of unrelated divers was studied and compared using th e same analytical procedures. More than 230 000 dives from 12 species were analyzed, and similar to 140 000 of these dives were classified according t o dive shape. The species included one cormorant, three penguins, two eared seals, five true seals, and a walrus. Dive profiles could generally be cha racterized as one of four shapes: square, V, skewed right, or skewed left. In light of this, a universal shape classification protocol was developed t hat also offers potential solutions for "on board" memory limitations and t ransmission constraints for archival time-depth recorders and satellite-lin ked time-depth recorders; Comparisons of dive data recorded with different sample intervals indicated the need for a standardization relative to mean dive duration (i.e., an equal number of data points per dive). Comparative analyses across these dive types and the different species revealed that sq uare dives were always, and by far, the most abundant dive type, usually fo llowed by V dives, and then the skewed dives. The percentage of time that t he animals spent at the bottom of square dives (similar to 50%), as well as the variation in depth during this bottom time (similar to 15%) were also quite uniform across species, indicating that similar foraging patterns wer e being used, at least relative to the shape of dives. Observed differences across species revealed that larger divers generally dived deeper and long er than did smaller ones, although fur seals and walrus were exceptions, wi th more limited diving performance than expected based on body size. Also, smaller divers had a tighter coupling between dive depth and duration than did larger ones, indicating that they may be more duration limited. Few oth er dive variables (e.g., the rate at which dive duration increases with dep th, the percentage of dives within each dive type, the percentage of bottom time. the coefficient of variation of depth during bottom time, and the me an wiggle distance per depth during square dives) were affected by body siz e, but instead physical (water depth) and ecological (type of prey) constra ints appeared to play major roles. Analyses using calculated aerobic dive l imit (cADL) indicated that generic calculations are problematic and that es timates of diving metabolic rate can drastically influence cADL and resulta nt findings. However, even using crude estimators, comparisons of cADL acro ss dive types indicated that square dives and V dives most often exceeded t he cADL for large and small divers, respectively. This indicates that squar e dives and V dives may be the pre dominant foraging dive types for larger and smaller divers, respectively, as animals would be expected to push thei r limits most during this activity. However, the abundance of square dives within the small divers (>60%) indicates that these dives may have a foragi ng role as well. Functional analyses of the determined dive types were in g eneral agreement with those from previous work indicating that the various dive types have foraging (benthic and pelagic), traveling, exploring, resti ng, and processing functions. However, for most species, except Weddell sea l and southern elephant seal (rare but likely important), skewed dives were rare and are likely to be of little importance to these animals' diving re gimes. Overall similarities in the dive patterns of the various species sug gest that these animals exploit the aquatic environment in a similar way.