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Predator odors often repel prey species. In the present experiments, we investigated whether changes in the diet of a predator, the coyote (Canis latrans) would affect the repellency of its urine. Furthermore, because predator odors have a high sulfur content, reflecting large amounts of meat in the diet, we investigated the contribution of sulfurous odors to repellency. Our results were consistent with the hypothesis that diet composition and sulfurous metabolites of meat digestion are important for the repellency of predator odors to potential prey.

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The effects of different social living conditions on estrogen excretion and on the ovarian cycle of saddle back tamarins were investigated. Urinary estrogens were monitored as indices of ovarian cyclicity in groups of adult females living under the following experimental conditions: (1) five parous females, each living with an adult castrated male (in one of the females plasma estradiol and progesterone were also measured); (2) five adult daughters living with their families. Each daughter was then removed from her family and paired with a vasectomized male. After pairing, scent marks collected from the family were introduced daily to one of the daughters and her mate. Scent exposure was then discontinued and hormone excretion measured for several weeks. The remaining four daughters were not exposed to family scent. The females living with castrated males showed urinary estrogen cycles of an average length of 17.5 1.0 days. The plasma estrogen cycle was of the same length. The females studied under condition 2 showed low, noncycling estrogen levels while living in their families. They responded to pairing with a n increase in the level of urinary estrogens, and four out of five showed regular estrogen cyclicity. The fifth female exposed to family scent marks after pairing also showed an increase in urinary estrogens. However, as long as scent transfer was maintained, no cycle was observed. Estrogen excretion increased again, and cyclicity commenced when scent transfer was discontinued. It is concluded that ovarian estrogen production is suppressed and cyclicity does not occur as long as daughters live in their families. Release from suppression and perhaps stimulation by the male cause a rapid increase in estrogen levels and the onset of cyclicity. Chemical stimuli produced by the family, perhaps particularly by the mother, may be involved in reproductive suppression.

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The frequencies per time unit of scent marking, aggressive threat, attacking another monkey and fighting it, were recorded in three Callithrix jacchus groups under different conditions: I-A: In undisturbed situations. I-B: In the presence of strange males and immediately following encounters with these males. I-C: In the presence of strange females and immediately following encounters with these females. II-A: When a new perch was introduced into the monkeys’ cage. II-B: When a perch, scent marked previously by strange conspecifics, was introduced into the monkeys’ cage. The results, especially the role of pheromones in sexual, territorial and social behavior of Callithrix jacchus are discussed.