Abstract Interactions between ants and aphids range from mutualistic to antagonistic. Understanding the ecological basis for such interactions requires understanding the costs and benefits to the aphids of ant-tending. Such an analysis is not simple, because ants can simultaneously have positive and

Status of the Colorado River population of the endangered Colorado squawfish Ptychocheilus lucius (recently renamed the Colorado pikeminnow) was investigated by (1) estimating adult numbers, (2) evaluating frequency of reproduction and recruitment, (3) identifying trends via changes in size structur

Behavior of Baetis bicaudatus (Ephemeroptera; Baetidae) was video taped in a western Colorado, USA stream to identify the specific stimuli eliciting noncontact responses to predatory stoneflies (Kogotus modestus; Plecoptera; Perlodidae). In situ behavioral and feeding trial experiments were also con

The mode of inheritance of the 15 electrophoretically different α-naphthyl acetate-specific esterases found in five population samples of Drosophila montana collected near Gothic, Colorado, was delineated by mating a strain which exhibited no esterase activity to 237 wild-caught flies, and analyzing

These are the first results to directly link the range of worker sizes to a component of colony fitness in a natural setting.

Evapotranspiration (ET) is a key component of the water balance, which influences hydrometeorology, water resources, carbon and other biogeochemical cycles, and ecosystem diversity. This study aims to investigate the spatio-temporal variations of ET at the East River watershed in Colorado and analyz

This study evaluated the relations between eggshell conductance to water vapor ($$G_{H_{2}O}$$), daily water loss ($$\dot{M}_{H_{2}O}$$), embryonic water content near pipping, and hatching success in red-winged blackbird eggs under conditions of natural incubation. All embryos hatched successfully o

Concentration-discharge (C-Q) relationships have been widely used as “hydrochemical tracers” to determine the variability in riverine solute exports across event, seasonal, annual, and decadal time scales. However, these C-Q relationships are limited to investigating solute transport dynamics at ind

Plasma melatonin concentrations were measured throughout bouts of hibernation in marmots maintained in a short photoperiod (light-dark 8:16) and ambient temperature of 5 or 15 degrees C. Melatonin concentration was also measured in two animals maintained in constant darkness. As an animal entered hi

In the last few years there has been an explosion of information concerning electrophoretic variation at enzyme loci. These data are being increasingly employed in attempts to elucidate biosystematic and phylogednetic relationships. As the evolutionary role of these allozyme polymorphisms is not wel

Emitting alarm calls may directly benefit individuals if callers have an increased chance of surviving, if calling increases the caller’s status, or if calling functions through reciprocity. Although previous studies have examined the costs and benefits of alarm calling, few have examined how an ind

Abstract. Measuring soil and snow temperature with high vertical and lateral resolution is critical for advancing the predictive understanding of thermal and hydro-biogeochemical processes that govern the behavior of environmental systems. Vertically resolved soil temperature measurements enable the

Abstract Ecological communities often show changes in populations and their interactions over time. To date, however, it has been challenging to effectively untangle the mechanisms shaping such dynamics. One approach that has yet to be fully explored is to treat the varying structure of empirical co

The first evidence of age-dependent mortality in a population of hummingbirds is shown, and Hummingbirds are seen to be model subjects for the study of longevity in nature.

Abstract Recent reports of insect declines have caused concern among scientists and the public. Declines in insect abundance and biomass are ubiquitous across many climatic zones and have been largely attributed to anthropogenic land use intensification and climate change. However, there are few exa

Numbers of Broad-tailed Hummingbirds (Selasphorous platycercus) captured each summer from 1979-1989 at the Rocky Mountain Biological Laboratory were quite variable, ranging from 115 (1981) to 348 (1989), with new birds usually outnumbering returning (previously banded) birds. Capture numbers were ne

Abstract Fear and anxiety may be adaptive responses to life-threatening situations, and animals may communicate fear to others vocally. A fundamental understanding of fear inducing sounds is important for both wildlife conservation and management because it helps us understand how to design repellen

Dispersal rates for freshwater invertebrates are often inferred from population genetic data. Although genetic approaches can indicate the amount of isolation in natural populations, departures from an equilibrium between drift and gene flow often lead to biased gene flow estimates. I investigated t

Adriana A. Maldonado- Temporal variation in environmental conditions affects population growth directly via its impact Chaparro,1,2,3* Daniel T. on vital rates, and indirectly through induced variation in demographic structure and phenotypic Blumstein,1,4 Kenneth B. Armitage5 trait distributions. We