Disappearance rate of bovine fetuses at Grand Teton National Park, state elk feedgrounds and at the National Elk Refuge.

Authors(s): E. Williams

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Publication Date: 0000-00-00

Type: annual report

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Abstract: Objectives In order to accurately model the risks of transmission and the effects of management strategies on brucellosis in wildlife, additional data are needed. This study is designed to obtain data about how long an aborted fetus remains in the field after an abortion occurs (fetus disappearance rate). Data from this experiment will provide an estimate of the maximum time span of infectivity because the Brucella abortus bacteria may die before the fetus is consumed. The important question of bacterial survival in aborted fetuses is the subject of a different experiment. Estimates of maximum fetus infectivity time will allow better prediction of risks of transmission to bison, elk and livestock. This information is not only essential to model risks of transmission, but it also is needed to model any disease control program. Findings and Status This is an ongoing study with additional data still to be collected in 1998. Coyotes (Canis latrans) were the dominant scavenger at all locations. Bald eagles (Haliaeetus leucocephalus) and golden eagles (Aquila chrysaetos) and ravens (Corvus corax) also participated in scavenging, occasionally consuming entire fetuses. Black-billed magpies (Pica pica) were often the first species to scavenge, especially on the state feedgrounds.; We also documented elk and bison orally contacting fetuses on several occasions. On the state feedground we documented elk making several contacts with fetuses. One fetus was contacted by over 100 elk and another by over 150 elk. This is probably an underestimate of the true number of contacts because fetuses were not monitored constantly. We were unable to monitor most of the fetuses at the National Elk Refuge closely enough to document contacts with them. At Grand Teton National Park a few elk and bison were noted to have come close enough to fetuses to make contact. Again, it is quite possible that more contacts occurred which we were unable to document. Mean time for a fetus to disappear from the state feedgrounds was 46 hours, at the National Elk Refuge it was 26 hours and at Grand Teton National Park it was 61 hours. Assuming an exponential distribution, we estimated that 90% of the fetuses disappear from state feedgrounds within 105 hours (4.4 days), from the National Elk Refuge within 60 hours (2.5 days), and from Grand Teton National Park within 140 hours (5.8 days). An analysis of covariance (ANCOVA) revealed significant differences in disappearance time of fetuses between the state feedgrounds and the National Elk Refuge (p=.0164). Habitat type also made a significant difference in how quickly fetuses were scavenged (p=.0001). We found that fetuses disappeared fastest on grasslands, followed by forests, and lasted longest in sagebrush.

Keywords: Grand Teton National Park, National Elk Refuge, Jackson Hole, Teton County, habitat, animal, mammal, ungulate, disease, brucellosis, bovine, elk, wapiti, Cervus elaphus, Cervidae, livestock, bison, Bison bison, canine, Canidae, Canis, Canis latrans, predation, food, forage, scavenge, bird, Aves, raptor, eagle, bald eagle, golden eagle, raven, Haliaeetus leucocephalus, Aquila chrysaeto, Corvus corax, Corvidae, ornithology, magpie, black-billed magpie, Pica pica