Distribution and Abundance of Fallow Deer Leks at Point Reyes National Seashore, California
By Gary M. Fellers and Michael Osbourn
Only two species of ungulates (hoofed mammals) are native to Marin County, tule elk (Cervis elaphus nannodes) and Columbian black-tailed deer (Odocoileus hemionus columbianus). In the 1940s, European fallow deer (Dama dama) obtained from the San Francisco Zoo were released at Point Reyes. When Point Reyes National Seashore was established in 1962, fallow deer were well established within the boundaries of the National Seashore. The fallow deer population was estimated to be 500 in 1973 (Wehausen, 1973) and that number increased to 860 by 2005 (National Park Service, unpubl. data).
Fallow deer have an unusual mating system. During the fall mating season (or rut), male fallow deer establish areas known as leks where they display to potential mates (Hirth, 1997). This behavior is unique among deer and elk, but it is similar to breeding systems used by grouse and a few other birds and mammals. Formation of leks in ungulates decreases the number of aggressive encounters in which dominant males are involved when the local male density becomes too high, because the spatial stability of territories in leks reduces the number of aggressive encounters between males (Hovi et al., 1996; Pélabon et al., 1999).
A fallow deer lek is typically an area of about 100–150 m2 and typically includes two to five males. Using their hooves and antlers, each male clears away most or all of the vegetation and digs a rutting pit that he defends throughout the breeding season.
Stenström et al. (2000) described rutting pits in a Swedish population of fallow deer:
"Pits are large patches of bare soil found at the center of mating stands where most of the rutting activities take place. . . . Scrapes are small patches of bare soil found throughout the areas of deer activity. Only bucks showed any interest in scrapes. Within a 10 day period half the scrapes were rescraped at least once. Larger scrapes were more frequently rescraped than smaller ones. Frayings, i.e., removal of bark and subsequent scent marking on bushes and small trees close to scrapes, also had a positive effect on the frequency of rescraping. . . . fallow deer bucks in our study do not seem to mark territorial boundaries, rather the intensity of markings tends to decrease with distance from the rutting pit suggesting that scraping may instead be used in male status signaling."
Establishing and defending a rutting pit is energetically expensive. Apollonio et al. (1989) concluded that: "Body condition appears to be an important determinant of male copulatory success, because only males in superior condition could defend a lek territory for up to two weeks. Males do not feed while defending lek territories. Foraging ability during the year probably determines condition at the onset of the rut. Females appear to choose mates at least partially on the basis of location, preferring males located near traditional routes. Females may ultimately select mates in the best body condition."
In the fall of 2005, we initiated a study of the leks in two study sites at Point Reyes National Seashore. The goal of this work was to determine the distribution and size of fallow deer leks, and to evaluate the impact of both the leks and the associated rutting pits on the soil and vegetation.