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We examined the degree and cause of intraspecific synchrony in population dynamics between 29-42 populations for each of seven mammalian species. Regions containing multiple populations with similar dynamics were identified using cluster analysis. Two explanations for the observed synchrony were evaluated, dispersal and the Moran effect, a spatially correlated density independent perturbation, such as weather, which occurs across populations. Populations synchronized by dispersal are expected to exhibit a negative relationship between synchrony and distance, while populations synchronized by a Moran effect must have a similar density-dependent structure (DDS). To distinguish between these hypotheses we used autoregressive modeling to determine the DDS of each population, and cross-correlation to estimate the degree of synchrony between populations. Dispersal alone was assumed to be responsible for synchrony in populations with a significant negative synchrony-distance (S-D) relationship and heterogeneous DDS. We assumed that a Moran effect ould have produced synchrony in populations with homogeneous DDS and non-significant S-D relationship. It was not possible to assign synchrony to a single factor in regions with a homogeneous DDS and a significant S-D relationship, and we excluded the possibility of a Moran effect in regions with heterogeneous DDS and a non-significant S-D relationship. Using these criteria, we identified dispersal as synchronizing populations within one region each of ermine, lynx, mink and red fox and in two regions of muskrat. A Moran effect may have synchronized one region of ermine, fisher, lynx, and mink, although we were unable to identify a causative factor. One lynx and one mink region showed characteristics of both dispersal and Moran-based synchrony, and 9 regions of synchrony could not be assigned to either factor. These results show that by examining the DDS and the S-D relationship we were able to determine the factors most likely responsible for synchronized population dynamics in 10 of 21 cases. Possible cases of Moran-based synchrony do not appear to be common, occurring in only 18.2% of these regions. It should also be noted that just as correlation does not imply causation, presence of homogeneous DDS does not indicate a Moran effect, only its possible occurrence.

Elk (Cerous elaphus nelsoni) that summer in Grand Teton National Park (GTNP) are part of the migratory Jackson Elk Herd. They are fed in winter on the National Elk Refuge (NER) and have been hunted in portions of GTNP since 1950 to control population size. However, the number of elk in the Jackson Elk Herd has grown from about 8,000 in 1984 to >16,000 in 1997. We captured and radiocollared 164 newborn calves during 1990-92 to quantify juvenile mortality and its role in regulating the Jackson Elk Herd. Elk captured in GTNP (5.9 elk/km 2 ) and on adjacent national forest lands of lower elk densities (2.4 elk/km 2 ) were radiomonitored through May 1994. Mortality of calves was similar during summer (15.2%), fall (15.3%), and winter (16.5%) 1990-92. Most deaths resulted from predation, hunting, and winter mortality associated with increased precipitation, duration of winter, and epizootic disease. Survival of calves supplementally fed in winter exceeded survival of calves not fed (P = 0.039). All but 1 of 16 deaths of elk ≥1 year old (n = 122) resulted from hunting. Early-born calves experienced higher winter survival (P = 0.02) than late-born calves. Annual calf survival (x = 0.579) was inversely related to birth date (P 0.47). Because much of the variation in juvenile survival was density independent, we recommend management that reduces the dependence of elk on supplemental feed and increases harvests of female elk.

The escape hypothesis predicts a greater probability of survival for seeds that are dispersed farther away from an isolated parent plant. This hypothesis was examined for Panicum miliaceum L., an annual grass that grows as an agrestal weed or as a crop. The patterns of seeds and mature offspring surrounding each of twenty parent plants were mapped. For those cases involving a large sample size, the average distance of the mature offspring from the parent plant was significantly (p