1. The use of stable isotope analysis (SIA) in ecological research has dramatically increased in recent years largely because it allows researchers to investigate ecological questions that have been previously difficult to address. 2. Ecological applications of SIA include estimating fundamental niche space and overlap, evaluating trophic or species level interactions, and investigating food web structure. Increasingly, researchers have been incorporating SIA in studies of animal migration, disease transmission, diet composition, nutrient assimilation, and body condition among others. 3. Studies using SIA to evaluate the ecology of terrestrial insects have lagged behind other taxonomic groups. This poor representation of stable isotope studies in publications likely stems from a lack of familiarity of entomologists with this technique. 4. An improved understanding of SIA, as well as the advantages and disadvantages specifically related to insect research, will benefit the field of entomology. In addition, insect-model systems provide unique opportunities for entomologists to incorporate SIA in their research to advance our knowledge of insect biology and the stable isotope ecology of insects. 5. We provide background information on stable isotopes, explain sources of isotopic variation, describe the processes of how isotopes are differentially routed and incorporated into an individual's tissues, explain the principles that influence isotopic fractionation and discrimination, highlight different methods and advancements in SIA, review innovative stable isotope studies, and provide an overview of common mistakes, considerations, and future directions entomologists can explore.

Effective wildlife management often relies on estimates of animal density, and cue counting is a viable estimation strategy.A key component of density estimation from dung, a form of cue counting, is estimation of the persistence time, t ^, of dung piles. However, differences between observers on what constitutes a dung pile may alter subsequent density estimates.Additionally, many researchers studying white-tailed deer (Odocoileus virginianus) have substituted for t ^the number of days between the date in which 98% of deciduous trees shed leaves in autumn and field sampling. To address these 2 concerns, we compared 3 methods for estimating t ^of whitetailed deer pellet groups: (1) a common modelling approach based on observations from a single observer (single-observer method), (2) a method that accommodates interobserver variation on the status of dung during field surveys (interobserver method), and (3) the days elapsed since 98% of deciduous trees shed autumn leaves (leaf-off method). We then applied these 3 t ^estimates to distance-sampling data on pellet groups from white-tailed deer that we collected along transects during 3 sampling seasons from 2019-2021 in westcentral Indiana. We estimated habitat-and year-specific deer densities. Persistence probability of pellet groups varied across habitats and years, positively with age and number of pellets, and negatively with precipitation and temperature. In several instances, we found strong or marginal differences between densities estimated using the leaf-off method and the other

Resource allocation to growth, reproduction, and body maintenance varies within species along latitudinal gradients. Two hypotheses explaining this variation are local adaptation and counter‐gradient variation. The local adaptation hypothesis proposes that populations are adapted to local environmental conditions and are therefore less adapted to environmental conditions at other locations. The counter‐gradient variation hypothesis proposes that one population out performs others across an environmental gradient because its source location has greater selective pressure than other locations. Our study had two goals. First, we tested the local adaptation and counter‐gradient variation hypotheses by measuring effects of environmental temperature on phenotypic expression of reproductive traits in the burying beetle, Nicrophorus orbicollis Say, from three populations along a latitudinal gradient in a common garden experimental design. Second, we compared patterns of variation to evaluate whether traits covary or whether local adaptation of traits precludes adaptive responses by others. Across a latitudinal range, N. orbicollis exhibits variation in initiating reproduction and brood sizes. Consistent with local adaptation: (a) beetles were less likely to initiate breeding at extreme temperatures, especially when that temperature represents their source range; (b) once beetles initiate reproduction, source populations produce relatively larger broods at temperatures consistent with their local environment. Consistent with counter‐gradient variation, lower latitude populations were more successful at producing offspring at lower temperatures. We found no evidence for adaptive variation in other adult or offspring performance traits. This suite of traits does not appear to coevolve along the latitudinal gradient. Rather, response to selection to breed within a narrow temperature range may preclude selection on other traits. Our study highlights that N. orbicollis uses temperature as an environmental cue to determine whether to initiate reproduction, providing insight into how behavior is modified to avoid costly reproductive attempts. Furthermore, our results suggest a temperature constraint that shapes reproductive behavior.

Rationale:Differences in stable isotope composition between an animal and its diet are quantified by experimentally derived diet-tissue discrimination factors.Appropriate discrimination factors between consumers and prey are essential for interpreting stable isotope patterns in ecological studies. While available for many taxa, these values are rarely estimated for organisms within the carrion food web. Methods:We used a controlled-diet stable isotope feeding trial to quantify isotopic diet-tissue discrimination factors of carbon (δ 13 C values) and nitrogen (δ 15 N values) from laboratory-reared Nicrophorus americanus raised on carrion. We used exoskeleton samples of beetle elytra (wing covers) to determine diet-tissue discrimination factors using a continuous flow isotope ratio mass spectrometer equipped with an elemental analyzer. We also measured the isotopic compositions of five species of co-occurring, wild-caught burying beetles and evaluated feeding relationships.Results: We found differences in stable carbon discrimination between carrion sources (mammalian and avian) and lab-reared beetles, but no difference in stable nitrogen discrimination. Values for δ 13 C did not differ among wild-caught burying beetle species, but values for δ 15 N were significantly different for the three species with overlapping breeding seasons. Furthermore, wild-caught burying beetles within our study area do not appear to use avian carrion resources to rear their young. Conclusions:This study informs future interpretation of stable isotope data for insects within the carrion food web. In addition, these results provide insight into carrion resources used by co-occurring burying beetle species in situ. We also demonstrated that independent of adult food type, the larval food source has a significant impact on the isotopic signatures of adult beetles, which can be estimated using a minimally invasive elytra clipping.

Negative economic impacts resulting from wildlife disrupting livestock operations through depredation of stock are a cause of human-wildlife conflict. Management of such conflict requires identifying environmental and non-environmental factors specific to a wildlife species' biology and ecology that influence the potential for livestock depredation to occur. Identification of such factors can improve understanding of the conditions placing livestock at risk. Black vultures (Coragyps atratus) have expanded their historical range northward into the midwestern United States. Concomitantly, an increase in concern among agricultural producers regarding potential black vulture attacks on livestock has occurred. We estimated area with greater or lesser potential for depredation of domestic cattle by black vultures across a 6-state region in the midwestern United States using an ensemble of small models (ESM). Specifically, we identified landscape-scale spatial factors, at a zip code resolution, associated with reported black vulture depredation on cattle in midwestern landscapes to predict future potential livestock depredation. We hypothesized that livestock depredation would be greatest in areas with intensive beef cattle production close to preferred black vulture habitat (e.g., areas with fewer old fields and early successional vegetation paired with more direct edge between