Ethogram of Yangtze finless porpoise calves (Neophocaena phocaenoides asiaeorientalis).

Underwater behavioral patterns of one Yangtze finless porpoise (Neophocaena phocaenoides asiaeorientalis) calf in captivity and those performed on the water surface by two calves in semi-natural environment were focally followed and continuously recorded until one year postpartum to construct the ethogram. The results indicate that 1) the three calves could display diverse and active behavioral patterns; 2) soon after birth, patterns critical for survival appeared first; 3) playful and social patterns predominated the ethogram; 4) most of the patterns were alike across age classes; 5) most of the patterns appeared at the calves' early life stage. It is possible that the above characteristics are adaptively shaped by the aquatic and social life of this subspecies.

Variation in sexual behaviors in a group of captive male Yangtze finless porpoises (Neophocaena phocaenoides asiaeorientalis): motivated by physiological changes?

Most male mammals in temperate regions demonstrate seasonal sexual behaviors that coincide with seasonal variations in gonadal activities and androgen hormones. The Yangtze finless porpoise is a temperate freshwater cetacean species and an obvious seasonal breeder. To investigate the relationship between sexual behavior and gonadal activity in this animal, testicular size (volume) and structure (ultrasonogram pixel intensity) of two adult male porpoises (AF, AB) and one sub-adult male (TT) were longitudinally monitored from November 2008 to November 2009. Serum testosterone concentration was also monitored during the same period. Variations in the frequency of sexual behavior in AF and AB had similar, but seasonal trends. Their testicular size and pixel intensity also varied seasonally. Testicular size increased in March, peaked from April through June, and decreased gradually from August through September, whereas testicular pixel intensity started to increase in early February. The frequency of sexual behavior was positively correlated with testicular volume and pixel intensity (P = 0.000018 and P = 0.00012, respectively) in AF. Serum testosterone concentrations also varied. The sub-adult male porpoise, TT, was undergoing puberty, as evidenced by its marked increase in testicular volume, testicular pixel intensity, and serum testosterone concentrations from the beginning of 2009. Interestingly, TT exhibited the highest frequency of sexual behavior, most of which was same-sex pairing. However, its oversexed behavior neither quantitatively correlated with its smaller testicular volume (P = 0.61) nor with its testicular pixel intensity (P = 0.69).