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1. Predation on parasites is a common interaction with multiple, concurrent outcomes. Free-living stages of parasites can comprise a large portion of some predators' diets and may be important resources for population growth. Predation can also reduce the density of infectious agents in an ecosystem, with resultant decreases in infection rates. While predator-parasite interactions likely vary with parasite transmission strategy, few studies have examined how variation in transmission mode influences contact rates with predators and the associated changes in consumption risk. To understand how transmission mode mediates predator-parasite interactions,we examined associations between an oligochaete predator Chaetogaster limnaei that lives commensally on freshwater snails and nine trematode taxa that infect snails. Chaetogaster is hypothesized to consume active (i.e. mobile), freeliving stages of trematodes that infect snails (miracidia), but not the passive infectious stages (eggs); it could thus differentially affect transmission and infection prevalence of parasites, including those with medical or veterinary importance.Alternatively, when infection does occur, Chaetogaster can consume and respond numerically to free-living trematode stages released from infected snails (cercariae). These two processes lead to contrasting predictions about whether Chaetogaster and trematode infection of snails correlate negatively ('protective predation') or positively ('predator augmentation').3. Here, we tested how parasite transmission mode affected Chaetogaster-trematode relationships using data from 20,759 snails collected across 4 years from natural ponds in California. Based on generalized linear mixed modelling, snails with more Chaetogaster were less likely to be infected by trematodes that rely on active transmission. Conversely, infections by trematodes with passive infectious stages were positively associated with per-snail Chaetogaster abundance. 4. Our results suggest that trematode transmission mode mediates the net outcome of predation on parasites. For trematodes with active infectious stages, predatory Chaetogaster limited the risk of snail infection and its subsequent pathology (i.e. castration). For taxa with passive infectious stages, no such protective effect was observed. Rather, infected snails were associated with higher Chaetogaster

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This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

Although the effects of shifting fire regimes on bird populations have been recognized as important to ecology and conservation, the consequences of fire for trophic interactions of avian species – and raptors in particular – remain relatively unknown. Here, we found that within national parks with long‐standing (40+ years) fire management programmes, California Spotted Owls Strix occidentalis occidentalis consumed predominantly Woodrats Neotoma spp. and Pocket Gophers Thomomys spp.; however, in contrast to our predictions, when their territories experienced more extensive and frequent fire, Spotted Owls consumed proportionally more Flying Squirrels Glaucomys oregonensis. We hypothesize this finding could have been driven by either changes to prey abundance following fires (e.g. increases in flying squirrels) or changes to prey availability (e.g. shifts in forest structure or flying squirrel spatial distribution that increased predation upon them by owls). Our work thus demonstrates that fire may have unexpected consequences for the trophic interactions of raptor species and provides valuable information for the conservation of Spotted Owls in fire‐prone forest landscapes.

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Species worldwide have begun to shift their range boundaries in response to climate change and other anthropogenic causes, with population declines at the trailing edge of a species' range often foreshadowing future changes in core parts of the range. Therefore, we analyzed a 30‐year (1991–2019) data set for the California spotted owl (Strix occidentalis occidentalis) near its southern range boundary in southern California, USA, that included the largest regional population (San Bernardino Mountains) to estimate trends in territory occupancy and reproduction. We then assessed how these demographic rates were affected by habitat, wildfire, fuel treatments, and climate. Mean occupancy declined from 0.82 to 0.39 during our study, whereas reproductive output showed no temporal trends ( truex ¯ = 0.65 young/occupied territory). Territory extinction (extirpation) rates were relatively low in territories with more large trees (≥50 cm dbh), and colonization increased strongly with large tree density for low‐elevation territories within the shrub‐woodland ecotype but not for higher‐elevation territories within mixed‐conifer forest. High‐severity wildfire had an adverse effect on occupancy: territory extinction rates steadily increased with the amount of high‐severity fire within an owl territory during the previous 10 years, while colonization declined to nearly zero when ≥40% of a territory burned at high‐severity during the previous 10 years. The effects of high‐severity fire were unlikely to be confounded with post‐fire fuel treatments, which primarily consisted of the removal, burning, or scattering of brush and small trees and snags (<40.6 cm dbh) and affected much smaller areas than high‐severity fire. Of the 40 territories that received fuel treatments within 10 years of a fire, only 3 of them had post‐fire fuel treatments that affected >5% of the territory, whereas average area burned at high severity for all 40 territories was 17%. Fuel treatments intended to modify fire behavior and reduce the likelihood of large, high‐severity fires led to increases in territory extinction and colonization such that their net effect on occupancy was minimal. Our simulations of occupancy dynamics indicated that high‐severity fire accounted for 9.6% of the observed decline in occupancy, whereas fuel treatments effectively accounted for none of the decline. Spotted owl reproductive output was lower at territories where fuel treatments occurred, but low‐ to moderate‐severity fire resulted in much larger, population‐level reductions in reproductive output (141 fewer young) from 2006–2019 than treatments (19 fewer young). Thus, the benefits of fuel treatments that reduce fire occurrence and severity appear to outweigh potential short‐term costs to spotted owls and their habitat. Because high‐severity fire only explained a modest amount of the long‐term occupancy decline and much of the decline occurred in the 1990s before large fires occurred, additional factors are likely adversely affecting the owl population and merit fur...