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Despite encounter rates being a key component of kill rate, few studies of large carnivore predation have quantified encounter rates with prey, the factors that influence them, and the relationship between encounter rate and kill rate. The study’s primary motivation was to determine the relationship between prey density and encounter rate in understanding the mechanism behind the functional response. Elk (Cervus elaphus Linnaeus, 1758) population decline and variable weather in northern Yellowstone National Park provided an opportunity to examine how these factors influenced wolf (Canis lupus Linnaeus, 1758) encounter rates with elk. We explored how factors associated with wolf kill rate and encounter rate in other systems (season, elk density, elk group density, average elk group size, snow depth, wolf pack size, and territory size) influenced wolf–elk encounter rate in Yellowstone National Park. Elk density was the only factor significantly correlated with wolf–elk encounter rate, and we found a nonlinear density-dependent relationship that may be a mechanism for a functional response in this system. Encounter rate was correlated with number of elk killed during early winter but not late winter. Weak effects of snow depth and elk group size on encounter rate suggest that these factors influence kill rate via hunting success because kill rate is the product of hunting success and encounter rate.

We analyzed the leadership behavior of breeding and nonbreeding gray wolves (Canis lupus) in three packs during winter in 1997–1999. Scent-marking, frontal leadership (time and frequency in the lead while traveling), initiation of activity, and nonfrontal leadership were recorded during 499 h of ground-based observations in Yellowstone National Park. All observed scent-marking (N = 158) was done by breeding wolves, primarily dominant individuals. Dominant breeding pairs provided most leadership, consistent with a trend in social mammals for leadership to correlate with dominance. Dominant breeding wolves led traveling packs during 64% of recorded behavior bouts (N = 591) and 71% of observed travel time (N = 64 h). During travel, breeding males and females led packs approximately equally, which probably reflects high parental investment by both breeding male and female wolves. Newly initiated behaviors (N = 104) were prompted almost 3 times more often by dominant breeders (70%) than by nonbreeders (25%). Dominant breeding females initiated pack activities almost 4 times more often than subordinate breeding females (30 vs. 8 times). Although one subordinate breeding female led more often than individual nonbreeders in one pack in one season, more commonly this was not the case. In 12 cases breeding wolves exhibited nonfrontal leadership. Among subordinate wolves, leadership behavior was observed in subordinate breeding females and other individuals just prior to their dispersal from natal packs. Subordinate wolves were more often found leading packs that were large and contained many subordinate adults.

The acceptance of an unfamiliar male wolf (Canis lupus) into a wolf pack after the recent death of the pack's alpha male was observed and filmed at close range in Yellowstone National Park, Wyoming, U.S.A. A 2½-year-old dispersing male from a neighboring pack was accepted as a new pack member over the course of a 6-h interaction. This observation involved stereotyped behaviors and canid body posturing in association with dominance/submission, play solicitation, and courtship. Although documented before via radiotelemetry, this interaction marks the first direct observation of a wild wolf pack accepting and incorporating a strange wolf as a breeder and pack leader.

Transmitters were implanted in three adult, one yearling, and one kit beaver (Castor canadensis) in northern Minnesota and upper Michigan to determine if core body temperature (Tb) declined in winter. Beaver Tb and activity were automatically recorded from late autumn through early spring. In late October through early November, mean daily Tb of adults was 36.3 °C (range 34.5–37.6 °C), with a mean daily Tb fluctuation of 1.4 °C. From fall to winter adult beaver Tb declined at a mean rate of 0.01 °C/day, and the mean daily winter (17 November – 15 April) Tb was 35.3 °C (range 32.5–38.8 °C). Mean daily winter Tb fluctuation was 2.5 °C. In early March, mean adult daily Tb began increasing at a rate of 0.03 °C/day. Tb and activity were positively correlated, except for the kit beaver, which did not undergo a significant Tb decline during winter. The yearling beaver Tb declined at a slower rate than adult Tb, and its Tb was intermediate between that of the kit and the three adults. Continued body growth in winter in young beavers is probably enhanced by high body temperature. For adult beavers, reduced body temperature in winter may be an adaptation that facilitates survival during extreme resource scarcity.

Bovet claims that Smith et al. (D.W. Smith, R.O. Peterson, T.D. Drummer, and D.S. Sheputis, 1991. Can. J. Zool. 69: 2178–2182) and Dyck and MacArthur (A.P. Dyck and R.A. MacArthur, 1992. Can. J. Zool. 70: 1668–1672) analyzed their data on activity and body temperature of beavers (Castor canadensis) incorrectly because they ignored the likelihood that northern beavers in winter have activity rhythms with periods >24 h. The analysis by Smith et al. was in fact appropriate for demonstrating seasonal changes in body temperature and its correlation with activity. These are important issues because researchers have obtained conflicting results and because seasonal changes in activity and body temperature have implications for colony energetics in the context of food-hoarding behavior and social organization.

Novel RNA polymerase activities (termed type II reaction) can be found in toluene-treated Escherichia coli with Ca2+, Fe2+, or endogenously bound cations, probably Mg2+. These activities are distinguishable from the well characterized DNA-dependent RNA polymerase (type I reaction) by: (i) their divalent cation requirements, i.e., the classical enzyme is activated by exogenously added Mn2+, Mg2+, or Co2+ ions; (ii) their relative resistance to inhibition by actinomycin D, rifampicin, and streptolydigin; (iii) their selective synthesis of low molecular weight RNA; (iv) their sensitivity to inhibition by arabinonucleoside 5′-triphosphates or deoxyribonucleoside 5′-triphosphates; and (v) the strict requirement for ATP in Ca2+ and bound cation-activated reactions. The Ca2+-activated and endogenous RNA polymerase activities are inhibited by orthophosphate. The properties of the type II RNA polymerase(s) are compared with those of polynucleotide phosphorylase, the dnaG gene product, and the RNA polymerase described by Ohasa and Tsugita.