Landscape heterogeneity provides co-benefits to predator and prey.

Predator populations are imperiled globally, due in part to changing habitat and trophic interactions. Theoretical and laboratory studies suggest that heterogeneous landscapes containing prey refuges acting as source habitats can benefit both predator and prey populations, although the importance of heterogeneity in natural systems is uncertain. Here, we tested the hypothesis that landscape heterogeneity mediates predator-prey interactions between the California spotted owl (Strix occidentalis occidentalis)-a mature forest species-and one of its principal prey, the dusky-footed woodrat (Neotoma fuscipes)-a younger forest species-to the benefit of both. We did so by combining estimates of woodrat density and survival from live trapping and very high frequency tracking with direct observations of prey deliveries to dependent young by owls in both heterogeneous and homogeneous home ranges. Woodrat abundance was ~2.5 times higher in owl home ranges (14.12 km2 ) featuring greater heterogeneity in vegetation types (1805.0 ± 50.2 SE) compared to those dominated by mature forest (727.3 ± 51.9 SE), in large part because of high densities in young forests appearing to act as sources promoting woodrat densities in nearby mature forests. Woodrat mortality rates were low across vegetation types and did not differ between heterogeneous and homogeneous home ranges, yet all observed predation by owls occurred within mature forests, suggesting young forests may act as woodrat refuges. Owls exhibited a type 1 functional response, consuming ~2.5 times more woodrats in heterogeneous (31.1/month ± 5.2 SE) versus homogeneous (12.7/month ± 3.7 SE) home ranges. While consumption of smaller-bodied alternative prey partially compensated for lower woodrat consumption in homogeneous home ranges, owls nevertheless consumed 30% more biomass in heterogeneous home ranges-approximately equivalent to the energetic needs of producing one additional offspring. Thus, a mosaic of vegetation types including young forest patches increased woodrat abundance and availability that, in turn, provided energetic and potentially reproductive benefits to mature forest-associated spotted owls. More broadly, our findings provide strong empirical evidence that heterogeneous landscapes containing prey refuges can benefit both predator and prey populations. As anthropogenic activities continue to homogenize landscapes globally, promoting heterogeneous systems with prey refuges may benefit imperiled predators.

Older forests function as energetic and demographic refugia for a climate-sensitive species.

More frequent and extreme heat waves threaten climate-sensitive species. Structurally complex, older forests can buffer these effects by creating cool microclimates, although the mechanisms by which forest refugia mitigate physiological responses to heat exposure and subsequent population-level consequences remain relatively unexplored. We leveraged fine-scale movement data, doubly labeled water, and two decades of demographic data for the California spotted owl (Strix occidentalis occidentalis) to (1) assess the role of older forest characteristics as potential energetic buffers for individuals and (2) examine the subsequent value of older forests as refugia for a core population in the Sierra Nevada and a periphery population in the San Bernardino Mountains. Individuals spent less energy moving during warmer sampling periods and the presence of tall canopies facilitated energetic conservation during daytime roosting activities. In the core population, where tall-canopied forest was prevalent, temperature anomalies did not affect territory occupancy dynamics as warmer sites were both less likely to go extinct and less likely to become colonized, suggesting a trade-off between foraging opportunities and temperature exposure. In the peripheral population, sites were more likely to become unoccupied following warm summers, presumably because of less prevalent older forest conditions. While individuals avoided elevated energetic expenditure associated with temperature exposure, behavioral strategies to conserve energy may have diverted time and energy from reproduction or territory defense. Conserving older forests, which are threatened due to fire and drought, may benefit individuals from energetic consequences of exposure to stressful thermal conditions.

Using the ecological significance of animal vocalizations to improve inference in acoustic monitoring programs.

Recent bioacoustic advances have facilitated large-scale population monitoring for acoustically active species. Animal sounds, however, can of information that is underutilized in typical approaches to passive acoustic monitoring (PAM) that treat sounds simply as detections. We developed 3 methods of extracting additional ecological detail from acoustic data that are applicable to a broad range of acoustically active species. We conducted landscape-scale passive acoustic surveys of a declining owl species and an invasive congeneric competitor in California. We then used sex-specific vocalization frequency to inform multistate occupancy models; call rates at occupied sites to characterize interactions with interspecific competitors and assess habitat quality; and a flexible multivariate approach to differentiate individuals based on vocal characteristics. The multistate occupancy models yielded novel estimates of breeding status occupancy rates that were more robust to false detections and captured known habitat associations more consistently than single-state occupancy models agnostic to sex. Call rate was related to the presence of a competitor but not habitat quality and thus could constitute a useful behavioral metric for interactions that are challenging to detect in an occupancy framework. Quantifying multivariate distance between groups of vocalizations provided a novel quantitative means of discriminating individuals with ≥20 vocalizations and a flexible tool for balancing type I and II errors. Therefore, it appears possible to estimate site turnover and demographic rates, rather than just occupancy metrics, in PAM programs. Our methods can be applied individually or in concert and are likely generalizable to many acoustically active species. As such, they are opportunities to improve inferences from PAM data and thus benefit conservation.

Uso de la Importancia Ecológica de las Vocalizaciones Animales para Mejorar la Inferencia en los Programas de Monitoreo Acústico Resumen Los avances bioacústicos recientes han facilitado el monitoreo a gran escala de poblaciones de especies acústicamente activas. Sin embargo, los sonidos de animales pueden transmitir cantidades sustanciales de información que queda utilizada insuficientemente en las estrategias comunes de monitoreo acústico pasivo (MAP) que tratan a los sonidos como simples detecciones. Desarrollamos tres métodos de extracción de detalles ecológicos adicionales de los datos acústicos que son aplicables a una gama amplia de especies acústicamente activas. Realizamos censos acústicos pasivos a escala de paisaje para una especie de búho en declinación y para un competidor congenérico invasivo en California. Después utilizamos la frecuencia de vocalizaciones específicas por sexo para orientar los modelos multiestado de ocupación; las tasas de llamados en sitios ocupados para caracterizar las interacciones con los competidores interespecíficos y evaluar la calidad de su hábitat; y una estrategia multivariada flexible para diferenciar a los individuos con base en sus características vocales. Los modelos multiestado de ocupación brindaron estimaciones novedosas para las tasas de ocupación por estado reproductivo que fueron más sólidas ante las detecciones falsas y capturaron el número de asociaciones de hábitat más sistemáticamente que los modelos de estado único agnósticos al sexo. La tasa de llamados estuvo relacionada con la presencia de un competidor pero no con la calidad del hábitat y por lo tanto podría constituir una medida conductual útil para las interacciones que son difíciles de detectar en un marco de trabajo de ocupación. La cuantificación de la distancia multivariada entre los grupos de vocalizaciones proporcionó un medio cuantitativo novedoso para discriminar a los individuos con ≥20 vocalizaciones y una herramienta flexible para balancear los errores del tipo I y del tipo II. Por lo tanto, parecer que hay posibilidad de estimar las tasas demográficas y de rotación, en lugar de sólo las medidas de ocupación, en los programas MAP. Nuestros métodos pueden aplicarse individualmente o de manera conjunta y es probable poder generalizarlas para muchas especies acústicamente activas. Dicho así, son oportunidades para mejorar las inferencias de los datos MAP y por lo tanto, beneficiar a la conservación.

Range-wide genetic differentiation among North American great gray owls (Strix nebulosa) reveals a distinct lineage restricted to the Sierra Nevada, California.

Investigations of regional genetic differentiation are essential for describing phylogeographic patterns and informing management efforts for species of conservation concern. In this context, we investigated genetic diversity and evolutionary relationships among great gray owl (Strix nebulosa) populations in western North America, which includes an allopatric range in the southern Sierra Nevada in California. Based on a total dataset consisting of 30 nuclear microsatellite DNA loci and 1938-base pairs of mitochondrial DNA, we found that Pacific Northwest sampling groups were recovered by frequency and Bayesian analyses of microsatellite data and each population sampled, except for western Canada, showed evidence of recent population bottlenecks and low effective sizes. Bayesian and maximum likelihood phylogenetic analyses of sequence data indicated that the allopatric Sierra Nevada population is also a distinct lineage with respect to the larger species range in North America; we suggest a subspecies designation for this lineage should be considered (Strix nebulosa yosemitensis). Our study underscores the importance of phylogeographic studies for identifying lineages of conservation concern, as well as the important role of Pleistocene glaciation events in driving genetic differentiation of avian fauna.

Blood parasites in owls with conservation implications for the Spotted Owl (Strix occidentalis).

The three subspecies of Spotted Owl (Northern, Strix occidentalis caurina; California, S. o. occidentalis; and Mexican, S. o. lucida) are all threatened by habitat loss and range expansion of the Barred Owl (S. varia). An unaddressed threat is whether Barred Owls could be a source of novel strains of disease such as avian malaria (Plasmodium spp.) or other blood parasites potentially harmful for Spotted Owls. Although Barred Owls commonly harbor Plasmodium infections, these parasites have not been documented in the Spotted Owl. We screened 111 Spotted Owls, 44 Barred Owls, and 387 owls of nine other species for haemosporidian parasites (Leucocytozoon, Plasmodium, and Haemoproteus spp.). California Spotted Owls had the greatest number of simultaneous multi-species infections (44%). Additionally, sequencing results revealed that the Northern and California Spotted Owl subspecies together had the highest number of Leucocytozoon parasite lineages (n = 17) and unique lineages (n = 12). This high level of sequence diversity is significant because only one Leucocytozoon species (L. danilewskyi) has been accepted as valid among all owls, suggesting that L. danilewskyi is a cryptic species. Furthermore, a Plasmodium parasite was documented in a Northern Spotted Owl for the first time. West Coast Barred Owls had a lower prevalence of infection (15%) when compared to sympatric Spotted Owls (S. o. caurina 52%, S. o. occidentalis 79%) and Barred Owls from the historic range (61%). Consequently, Barred Owls on the West Coast may have a competitive advantage over the potentially immune compromised Spotted Owls.