Observations of Copulation of Free-Ranging American Marten

Abstract

Copulation in captive American marten (Martes americana) has been described (Ashbrook and Hanson 1930; Brassard and Bernard 1939; Markley and Bassett 1942), but we are aware of no accounts describing observations of copulation in free-ranging marten. On two occasions during summer 1987, while radio-tracking marten to study habitat selection (Raphael 1987), we observed freeranging marten and associated mating behavior. The study area is in the Sierra Madre range, 15 km south of Encampment, Wyoming. Elevations vary from 3240 to 3350 m. Lodgepole pine (Pinus contorta) and an understory of grouse whortleberry (Vaccinium scoparium) dominate on southerly slopes; Engelmann spruce (Picea engelmannii) and subalpine fir (Abies lasiocarpa) dominate on northerly slopes. While monitoring the radio signal of a male marten for several minutes on 22 July at 1530 MDT, we determined that he was active but not travelling. When 100 m from the animal, one of us (SEH) heard a sound like cats fighting. Moving closer to investigate, SEH observed two marten in what at first appeared to be an altercation. They were snarling, wrestling, kicking up soil and pine needles, and were unaware of the observer's presence within 30 m. The commotion settled momentarily and the female raised her tail. The male bit the female on the back of her neck and mounted her at 1600 MDT. She screamed immediately and growled intensely. He remained mounted for about 30 s, whereupon she twisted her body and broke his grasp. He ran about 4 m away but instantly returned, seized her neck, and remounted her for about 15 s until she struggled free and disappeared with the male in pursuit. After relocating the male, SEH observed the female in dense Vaccinium. She jumped upon a tree and after several minutes the male reappeared. He slowly circled the tree twice, maintaining a distance of 12 m from it. The male then spread out all four legs and lay flat on the ground panting. Over a 5-min interval he closed his eyes and seemed to doze off on two occasions. Finally he stood up and loped away. Copulation occurred in a l-m patch of bare soil. The surrounding forest was primarily lodgepole pine (basal area = 37 m2/ha) and subalpine fir (6 m2/ha). Average tree diameter (dbh) was 25 cm for pine and 14 cm for fir; canopy cover was 81%. A second observation of a different male occurred on 28 July at 1230 MDT. As in the previous observation, SEH first heard screaming and snarling. Two martens ran past and climbed up a lodgepole pine. Both martens walked out onto a branch and the male mounted the female. They copulated on the branch for about 2 min until they noticed the observer 50 m away. They then descended the tree, and ran away. We continued monitoring the male's radio signal for 2.5 hr. The male remained active, apparently running back and forth within the same timber stand the entire time. At 1510 MDT the signal indicated inactivity and at 1600 SEH located the male resting in a snag. The male descended the snag; about 10 min later the female also descended. The snag had a cavity in a high crotch where the pair of marten apparently were resting together. The timber stand, a 120-ha patch of old-growth lodgepole pine with an open canopy, was surrounded by five clearcuts about 150 m away. The lodgepole pine in which copulation occurred was 22 m tall with a diameter of 32 cm. Copulation occurred on a 15-cm branch 8 m above the ground. Two road graders were being operated about 400 m from the site at the time of copulation. Until the 1920's, mammalogists and naturalists speculated that the normal mating season of marten was in January and February (Seton 1929). Nelson (1922) was the first to report marten breeding in July and August, and his findings were supported by Ashbrook and Hanson (1927) and Walker (1929). Brassard and Bernard (1939) found that marten courtship may last as long as 15 days. Copulation of captive marten commonly lasts more than an hour and rarely occurs between 1000 MDT and 1500 MDT (Markley and Bassett 1942). Markley and Bassett (1942) also reported that individual marten will mate up to 15 times during a breeding season. Although they found that copulation always took place on the ground, they also stated, One might not expect that such would be the case with an animal of arboreal habit (Markley and Bassett 1942:610). Because nine of their adult