Is it possible to do a pregnancy test on free-ranging cetaceans?
The health of a given population resides, for the most part, in its ability to reproduce itself. The capacity to evaluate the gestation rate of adult females can therefore reveal a great deal about a given population. Measuring progesterone concentrations in blubber is a promising “pregnancy test” for cetaceans. Could this technique be useful for studying St. Lawrence harbour porpoises and beluga whales?
To go through the looking glass
Researchers are able to take small pieces of blubber from free-ranging cetaceans using biopsy darts. Studies on certain cetacean species have revealed that even blubber samples of less than one gramme are sufficient to measure progesterone concentrations, thus revealing whether or not a female is gestating.
In order to determine if this type of sampling could be useful for studying two threatened species of St. Lawrence cetaceans, the harbour porpoise and the beluga whale, blubber progesterone concentrations were measured on the carcasses of 38 beluga whales (27 females and 11 males) and 31 harbour porpoises (21 females and 10 males).
This project has confirmed that blubber samples of between 0.25 g and 1.0 g are sufficient to measure the progesterone concentrations of these species. For beluga whales, it appears that the analysis of a sample from the superficial blubber layer (that which makes up a biopsy sample) is sufficient. For the harbour porpoise, while the internal layer is richer in hormones, the superficial layer also gave satisfactory results. This information confirms that biopsy sampling, as conducted on St. Lawrence beluga whales, is an effective technique for taking usable samples for the measurement of progesterone concentrations.
Comparisons between males and females, and between gestating females and non-gestating females, were conclusive. The measurement of progesterone concentrations in the blubber of harbour porpoises and beluga whales obtained through biopsy sampling is therefore a reliable technique for determining if a female of either of these species is gestating.
It is possible to conduct pregnancy tests on free-ranging female beluga whales and harbour porpoises.
Fisheries and Oceans Canada’s threatened species research program
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