Abstract
The harbour porpoises kept at the Fjord & Bælt since April 1997 offer a unique opportunity to gain a better understanding of the reproductive function in harbour porpoises, especially in terms of physiological cycle and concomitant behavioural traits. A study was initiated in 1997 with the following aims: 1) characterising the annual reproductive cycle in terms of behaviour and endocrine activity; 2) finding the most suitable techniques for a longitudinal investigation of the reproductive function, in particular with respect of the small size of the species; 3) ensuring a precise monitoring of the reproductive state of the Fjord & Bælt porpoises; 4) evaluating the best techniques for a vertical assessment of the reproductive state in wild harbour porpoises; 5) providing comparative basis for toxicological studies.Three harbour porpoises have participated in the study: a male and a female estimated 1-2 years old at their arrival at the Centre in 1997, and a one-year old female. The different methods for investigating their reproductive function include techniques not previously used with harbour porpoises, such as behavioural observation, measurement of sexual hormones in blood and other matrices, vaginal cytology, body temperature, and ultrasound scanning of testes and ovaries. These methods are discussed in terms of practicality and invasiveness. Selected examples of the preliminary results obtained are reported.Projects have concentrated on the sexual behaviour of the adult male and female (frequency, initiative, courtship behaviours) and their hormonal correlates, as well as on the interaction of the juvenile with the 2 adult animals. Behavioural sexual activity is very seasonal (peaking at the end of July and August), as is the testosterone cycle (levels increasing from less than 1 ng/ml to 30 ng/ml in May) and the development of the testis (peaking in July-August). Progesterone and oestrogen levels vary between less than 1 to 17 ng/ml and less than 0.1 to 1.8 ng/ml respectively, but infrequent blood sampling precluded obtaining a detailed picture of the ovarian cycle. We are attempting to measure sexual hormones in saliva and eye secretion. Successful matings have been confirmed by the presence of sperm on vaginal smears in 4 consecutive summers, but no pregnancy has occurred yet.
Highlights
Studies on reproduction in harbour porpoises have long been limited to point sampling on dead animals
In the framework of a long-term monitoring, invasiveness and induced stress are factors important to consider. For some techniques these can, be reduced by training the animals in voluntary husbandry behaviours (VHB), i.e., training them to co-operate so sampling can be performed without physical restraint
A much higher level of progesterone (42 ng/ml) was observed in a wild female accompanied by a calf in April 1999 (Desportes, unpubl. data). These results provide the first range of values for oestrogen and progesterone levels in harbour porpoises
Summary
Studies on reproduction in harbour porpoises have long been limited to point sampling on dead animals (e.g. for Danish strandings: MøhlHansen 1954, Andersen et al.1992, Sørensen and Kinze 1994, Lockyer and Kinze 2003). Hormonal values have not been reported for harbour porpoises, and are available only for one phocoenid species, the Dall’s porpoise Phocoenoides dalli (Temte and Spielvogel 1985, Subramanian et al 1987, Temte 1990). Serious concerns have been expressed that toxins may cause reproductive failure in harbour porpoises, and may be contributing to the apparent decline of some populations The effect of toxins on reproductive capabilities is very difficult to investigate without a thorough understanding of the reproductive events; physiological, anatomical as well as behavioural
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