Abstract

A male and a female harbour porpoise, by-caught in the same pound net, were brought to the Fjord and Belt Centre, Kerteminde, Denmark, in April 1997 and kept there for research purposes in a semi-natural environment. They were estimated to be 2-3 years old and immature. This offered a unique opportunity to study the transition from puberty to reproductive maturity in terms of behaviour and physiological changes.

A combination of different methods were used: on line behavioural recordings using a behaviour study software; analyses of video recordings, recordings of acoustic activity through click detectors, radio immunoassay titration of plasma testosterone, progesterone and estrogen, cytological analysis on vaginal and prepucial smears, body temperature monitoring, and ultrasound imaging of genital tracts.

With findings supporting each other, each of the techniques shed a different light on the maturation process, the appearance and development of sexual behaviour and the relative responsiveness of the participants. Vaginal cytology revealed that intromission became successful in the summer of 1998, although mating attempts had been ongoing since September 1997, but without resulting in a diagnosed pregnancy. The pubertal male of a reproductively highly summer seasonal species using the first winter to "test" himself may or may not be an artefact of captivity.