Temperature, turbulence, oxygen, and notonectid predators (Anisops calcaratus) were studied experimentally as possible factors influencing crest growth in six different forms of the Daphnia carinata complex. Predators were the most potent influence, inducing crest development in four of the morphs. Temperature had only a secondary effect which may have been indirect. When the notonectids were partitioned off from the Daphnia in the same container, crest development still resulted, suggesting that the stimulus was a water-soluble secretion from the predator. If the notonectids were starved this secretion was either not produced or was ineffective. Experiments showed that predators could induce crest development in adult daphnids that were initially uncrested and that a sustained stimulus from the predator was necessary if crested juvenile Daphnia were to produce crested adults. Under experimental conditions, daphnids with a crest were less susceptible to notonectid predation (mainly because of superior evasion powers) than were those without one. Results of a regression analysis of field data were broadly consistent with experimental results, especially in indicating that predation was a potent factor influencing crest development, and the distribution and abundance of morphs.

G rant J. and Hawley A. 1996. Some observations on the m ating behaviour of captive American pine martens Martes americana. Acta Theriologica 41: 4 3 9 -4 4 2 .Four male and 8 female captive pine martens Martes americana (Turton, 1806) were observed for signs of mating. Behavioural changes associated with the breeding season began in mid-June. Subjective observation indicated that the frequency of abdominal scent marking and body contact between males and females increased from June through July and decreased during A ugust. Aggression between females in creased markedly during the breeding season. The animals emitted diverse vocaliza tions, including a throaty chuckle that was associated with breeding and that was indistin guishable by observers from a call emitted when fem ales appeared to be consoling young kits. Copulation was observed on 4 occasions during July in one pair o f m artens, and was typical of that described for M artes species in general. Two individual copulatory acts were timed and lasted 5 and 14.5 min, respectively. The female appeared to control the timing and duration of copulation and seemed in one instance to actively solicit the attention of the male.