Abundance estimation of long-diving animals using line transect methods.

Line transect sampling is one of the most widely used methods for estimating the size of wild animal populations. An assumption in standard line transect sampling is that all the animals on the trackline are detected without fail. This assumption tends to be violated for marine mammals with surfacing/diving behaviors. The detection probability on the trackline is estimated using duplicate sightings from double-platform line transect methods. The double-platform methods, however, are insufficient to estimate the abundance of long-diving animals because these animals can be completely missed while the observers pass. We developed a more flexible hazard probability model that incorporates information on surfacing/diving patterns obtained from telemetry data. The model is based on a stochastic point process and is statistically tractable. A simulation study showed that the new model provides near-unbiased abundance estimates, whereas the traditional hazard rate and hazard probability models produce considerably biased estimates. As an illustration, we applied the model to data on the Baird's beaked whale (Berardius bairdii) in the western North Pacific.

Localization of aquaporin-2, renal morphology and urine composition in the bottlenose dolphin and the Baird's beaked whale.

This study examined the distribution pattern of aquaporin-2 (AQP2), relative medullary thickness (RMT) and urine properties in the bottlenose dolphin Tursiops truncatus and Baird's beaked whale Berardius bairdii. Immunohistochemical studies revealed that AQP2 was localized in the collecting tubules/ducts of both species' renicules, as in terrestrial mammals. The collecting ducts with AQP2 were thinner and arranged more densely in the dolphin than in the whale. RMT values in the renicule were moderate in both species, but were significantly higher in the dolphin (6.0 +/- 0.9) than the whale (4.9 +/- 0.7). Urine of the bottlenose dolphin is comparatively concentrated (osmolality: 1715.7 +/- 279.4 mOsm kg(-1), Na(+): 490.1 +/- 87.9 mmol l(-1), Cl(-): 402.7 +/- 79.6 mmol l(-1), K(+): 80.7 +/- 25.8 mmol l(-1), urea nitrogen: 703.5 +/- 253.9 mmol l(-1)), while urine of the dead Baird's beaked whale is less concentrated (osmolality: 837.5 +/- 293.8 mOsm kg(-1), Na(+): 192.9 +/- 81.5 mmol l(-1), Cl(-): 159.9 +/- 71.4 mmol l(-1), K(+): 44.3 +/- 29.5 mmol l(-1), urea nitrogen: 270.7 +/- 120.3 mmol l(-1)). These data suggest it is possible that the differences in these renal morphological features may be related in some way to the difference in urine composition between the species, although further studies are necessary.