Recreational shooters kill millions of small mammals each year and scavengers that ingest the carcasses can be poisoned if lead bullets are used. Less toxic bullets exist, but their performance and potential risk to deposit lead in carcasses is understudied. In May 2016, shooters controlled populations of Columbian ground squirrels (Urocitellus columbianus) at ranches in Idaho and Montana, USA, by shooting them with .17 HMR (Hornady Magnum Rimfire), .22 LR (long rifle), and .223 Rem (Remington) rifles with expanding and nonexpanding lead and nonlead bullets. We recorded whether bullets instantly incapacitated ground squirrels and then counted the number of bullet fragments in each carcass to estimate concentrations of residual lead. All types of lead bullets left lead in at least one-third of the Columbian ground squirrels. Unexpectedly, estimated concentrations of lead in carcasses did not differ between expanding and nonexpanding bullets within the .17 HMR and .22 LR calibers, partially because of the high variability in fragmentation. The greatest estimated concentrations of lead were in Columbian ground squirrels shot with expanding ammunition in .17 HMR and .223 Rem, which had an average of 23.6 mg and 91.2 mg Pb/carcass, respectively. Nonlead bullets incapacitated similar to lead bullets. Our results indicate that nonlead bullets eliminate the risk of additional lead exposure to scavengers while maintaining the lethality of lead bullets.

Scavengers are subsidized by the remains of hunting worldwide. Although most studies focus on carcasses of large mammals, small mammals that have been shot likely provide a significant food subsidy as well, particularly in parts of the western United States. Millions of small mammals are estimated to be shot each year for damage control and recreation, many being left in the field. Despite this prevalence of carrion, and the potential for scavengers to ingest residual lead from bullet fragments, the fate of these carcasses is largely unknown. We deployed remote cameras to observe which scavengers consumed shot ground squirrels (Urocitellus spp.) and black‐tailed prairie dogs (Cynomys ludovicianus) in 8 locations across Montana, USA. At least 5 species of mammals and 9 species of birds scavenged, including burrowing owls (Athene cunicularia). Scavengers fully consumed 66% of carcasses and partially consumed 9%. Carcasses lasted an average of 24.5 hours before the first scavenger arrived. Of carcasses that were scavenged, mammals ate 16% and birds ate 84%, with corvids and raptors consuming an equal number of carcasses. Common ravens (Corvus corax) and black‐billed magpies (Pica hudsonia) visited the most carcasses and often arrived first. Scavengers consumed only 9% of the carcasses that were partially concealed by being inside a burrow. Overall, our results indicate that a diverse scavenger community consumes shot ground squirrels and black‐tailed prairie dogs, and consequently, may be exposed to lead from bullet fragments. © 2019 The Wildlife Society.

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Invasive plants are often associated with greater productivity and soil nutrient availabilities, but whether invasive plants with dissimilar traits change decomposer communities and decomposition rates in consistent ways is little known. We compared decomposition rates and the fungal and bacterial communities associated with the litter of three problematic invaders in intermountain grasslands; cheatgrass (Bromus tectorum), spotted knapweed (Centaurea stoebe) and leafy spurge (Euphorbia esula), as well as the native bluebunch wheatgrass (Pseudoroegneria spicata). Shoot and root litter from each plant was placed in cheatgrass, spotted knapweed, and leafy spurge invasions as well as remnant native communities in a fully reciprocal design for 6 months to see whether decomposer communities were species‐specific, and whether litter decomposed fastest when placed in a community composed of its own species (referred to hereafter as home‐field advantage–HFA). Overall, litter from the two invasive forbs, spotted knapweed and leafy spurge, decomposed faster than the native and invasive grasses, regardless of the plant community of incubation. Thus, we found no evidence of HFA. T‐RFLP profiles indicated that both fungal and bacterial communities differed between roots and shoots and among plant species, and that fungal communities also differed among plant community types. Synthesis. These results show that litter from three common invaders to intermountain grasslands decomposes at different rates and cultures microbial communities that are species‐specific, widespread, and persistent through the dramatic shifts in plant communities associated with invasions.

Predation rates were measured for two Acanthamoeba castellanii strains feeding on metal-tolerant and metal-sensitive strains of Pseudomonas putida and compared with cellular thermodynamic data. Predation rates by A. castellanii strain ATCC 30010 correlated with cell volume of the prey. To explore whether this observation could be environmentally relevant, pseudomonad species were isolated from a pristine and a metal-contaminated river and were paired based on phylogenetic and physiological relatedness. Then, cellular thermodynamics and predation rates were measured on the most similar pseudomonad pair. Under cadmium stress, the strain from contaminated river sediments, Pseudomonas sp. CF150, exited metabolic dormancy faster than its pair from pristine sediments, Pseudomonas sp. N9, but consumed available resources less efficiently (more energy was lost as heat). Predation rates by both strains of ameba were greater on Pseudomonas sp. CF150 than on Pseudomonas sp. N9 at the highest cadmium concentration.