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Differences in Breathing Ecology

Cetaceans are tied to the surface by the necessity to breathe but require submersion for other activities such as to feed, travel, communicate, socialize, mate, or to avoid predators. To optimize these two contrary situations, whales generally exhibit two phases; a) respiration period with a series of blows and short dive intervals in-between; and b) longer diving periods when they remain submerged at different depths and for different durations (graph 1).

In the late Eighties Ned Lynas hypothesized that the respiration patterns visible at the surface reflect the whales’ different activities at depth. From the numerous respiration data samples he had collected of all rorqual whale species we focused on the minke whales for this study.

Breathing interval samples of at least 25 minutes duration collected from 1995 – 1998 were analyzed. Based on visual observations they were categorized into the following three different activities, which also show significantly different respiration patterns as shown in this study.

Travelling

Traveling aims to maximize distance covered with minimum hydrodynamic drag. Reducing time at the air-water interface and remaining at depths less than three times the body diameter enhances hydrodynamic performance. Traveling minke whales show the longest surfacing intervals.

Surface Feeding

Minke whales performing visible feeding behaviours at the air-water interface have a very erratic surfacing pattern, as air-acquisition is no longer a limiting factor when feeding so close to the surface of the water.

Feeding at Depth

This behaviour is visually recognizable by the distinct surface geometry high numbers of repetitive respirations, strong dorsal arches and long dive durations as well as re-submerging in the same place (Ned Lynas, unpubl.). The breathing patterns of minke whales feeding at depth, is clearly defined by long dive intervals and repetitive and closely clustered respiration surfacings.

An understanding of the respiration behaviour of whales is central for a variety of studies such as a) breathing and foraging ecology, b) calculating metabolic rates, c) understanding the probability of detecting whales, and d) to increase reliability of “cue counting” census surveys for population estimates. Additionally, it serves as a tool for assessing reactions of whales to the potential disturbance from whale watching boats.

 

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