Jeffrey A. Manning

Environmental DNA (eDNA) sampling is a powerful method for detecting aquatic species at low densities. However, eDNA may remain close to the source in lentic systems, decreasing the effectiveness of eDNA surveys. We conducted cage experiments with salamanders and simultaneous detailed hydrologic and wind measurements to investigate the influence of the physical environment on detection patterns of eDNA in ponds. We found much higher detection rates in the surface layer than at depth, and that aquatic vegetation reduced detection of eDNA produced in open water by 80%–94%. Within the surface mixed layer, detection rates were highest close to the source in the direction of water flow in the bottom half of the layer, and detections farthest from the source occurred when velocities in this sublayer were high. Detections were near zero even close to the source when this sublayer was flowing fast and away from the sampling point. The direction of water flow in this lower half of the surface mixed layer was negatively correlated with wind direction for most of the study. These spatial and temporal dynamics indicate that eDNA transport processes in ponds are highly complex. Sampling away from aquatic vegetation, in the surface mixed layer, and upwind of potential sources, in addition to sampling at many locations within a pond and considering temporal patterns, may improve detection of rare pond species. This work contributes to a growing body of literature characterizing the variability of eDNA detection in lentic systems.

Ponds are characterized by high biodiversity, intense biogeochemical cycling, and susceptibility to anthropogenic impacts. Yet few studies have quantified the water velocities responsible for vertical mixing or lateral transport in ponds. We used high‐resolution observations of velocity to examine mixing and transport during summer in a 50‐m‐long, 2.7‐m‐deep temperate pond. Many observed transport and mixing processes resembled those found in larger stratified lakes. A surface mixed layer was observed, whose depth ranged between ~ 1 m at night and < 0.3 m during the day. Turbulence was usually sufficient to vertically mix the surface layer in 4–12 min, but no turbulence was observed in the hypolimnion. Persistent (2.5‐h‐averaged) currents usually flowed downwind near the surface and returned upwind near the mixed layer base. Surface currents were proportional to windspeed, with root‐mean‐squared speed of (persistent hypolimnion currents were much weaker). Superposed on persistent currents were 30‐ to 100‐min‐period fluctuations resulting from internal seiches. These fluctuations were comparable in magnitude to more persistent currents in the mixed layer and dominated in the hypolimnion. Seiches did not advect particles far across the pond, but did contribute to production of mixed layer turbulence. Seiches also contributed to shear dispersion, which was sufficient to mix near‐surface tracers across the pond in 2–4 d. Theory suggests that hypolimnion bottom boundary layers were laminar during the downslope phase of seiche motion, but became turbulent during the upslope phase as near‐bed water flows created unstable stratification.

Social behaviour is thought to be a major component of survival, reproduction, and resilience of populations. Thus, it is a key component in management and conservation of wild populations. In polygynous breeding species, group size influences the reproductive success of males and females, and hence it is essential to understand the environmental and demographic factors that shape the phenology of group size within populations. Here, we investigate harem size and its determinants using a 15‐year dataset of annual harem size phenology‐based metrics from a reintroduced population of wild Przewalski horses in Hortobágy National Park, Hungary. From the initial reintroduction of 21 animals in 1997, the population grew to 174 animals in 2012. During that same period, the number of harems increased from three to 23. Despite the 8‐fold increase in population size, harem sizes remained stable, and variability among harems within years decreased. The annual phenological cycle of harem size was not consistent over the 15‐year period, and the associated annual phenology‐based metrics varied differently over the years. The best predictors of our phenology‐based harem size metrics were adult sex ratio, annual adult mortality and annual mean number of harems, with some evidence that mean age of harem stallions and drought severity were contributing factors. Our findings reveal that complex interactions between demography, climate, and harem size can emerge in social animals. Taken together, our results demonstrate that intrinsic population processes can regulate group size even in the presence of non‐stationary climatic conditions during periods of growth in human‐introduced, semi‐free ranging animal populations.

Sampling fecal droppings (scat) to genetically identify individual animals is an established method for monitoring mammal populations and could be highly useful for monitoring reptile populations. Whereas existing protocols for obtaining DNA from reptile scat focus on analyses of whole, fresh scat deposited during animal handling, the collection of scat naturally deposited by reptiles in situ, as required for non‐invasive population monitoring, requires protocols to extract highly degraded DNA. Using surface swabs from such scats can reduce PCR inhibition and increase genotyping success. We report on three related but independently designed studies of DNA analyses from scat swabs of herbivorous reptiles under natural desert conditions: two free‐ranging desert tortoise species (Agassiz's desert tortoise, Gopherus agassizii, California, US, and Morafka's desert tortoise, G. morafkai, Arizona, US) and the common chuckwalla (Sauromalus atar) (Arizona, US, and Sonora, MX). We analyzed samples from both tortoise species with the same set of 16 microsatellites and chuckwalla samples with four mtDNA markers; studies also varied in swab preservation medium and DNA extraction method. Microsatellite amplification success per sample, defined as ≥9 loci with amplification, was 15% for the study of Agassiz's desert tortoise and for the study of 42% Morafka's desert tortoise. For chuckwallas, we successfully amplified and sequenced 50% of samples. We recovered fragments up to 400 bp for tortoises and 980 bp for chuckwallas from scat swab samples. This study indicates that genotypes can successfully be obtained from swabs of scat from herbivorous reptiles collected in the field under natural environmental conditions and emphasizes that repeat amplifications are necessary for the genetic identification of individuals from non‐invasive samples.

The western distinct population segment of yellow‐billed cuckoo (Coccyzus americanus; western cuckoo) has been extirpated from most of its former breeding range in the United States because of widespread loss and degradation of riparian cottonwood (Populus spp.)‐willow (Salix spp.) forests. Restoration and management of breeding habitat is important to the recovery of this federally threatened species, and identification of high‐quality breeding habitat can help improve the success of recovery. In 2005, the Lower Colorado River Multi‐Species Conservation Program, a long‐term, multi‐agency effort, was initiated to maintain and create wildlife habitat within the historical floodplain of the lower Colorado River (LCR) for federally endangered and threatened species, including western cuckoos. We conducted an empirical, multi‐scale field investigation from 2008–2012 to identify habitat characteristics selected by nesting western cuckoos along the LCR. Multiple logistic regression models revealed that western cuckoos selected nest sites characterized by increased densities of small, native, early successional trees measuring 8–23 cm diameter at breast height, and lower diurnal temperature compared to available habitat in restoration and natural forests. Nesting cuckoos selected sites with increased percent canopy closure, which was also important for nest success in restoration sites along the LCR. Our results show habitat components selected by nesting western cuckoos in restoration and natural riparian forests and can help guide the creation, enhancement, and management of riparian forests with habitat conditions necessary to promote nesting of western cuckoos. © 2021 The Wildlife Society.

Ecological and social factors underpinning the inequality of male mating success in animal societies can be related to sex ratio, sexual conflict between breeders, effects of nonbreeders, resource dispersion, climatic conditions, and the various sequential stages of mating competition that constitute the sexual selection process. Here, we conducted an individual‐based study to investigate how local resource availability and demography interact with annual climate conditions to determine the degree of male mating inequality, and thus opportunity for sexual selection across two sequential reproductive episodes (harem and subsequent mate acquisition) in a naturally regulated (feral) horse population in Sable Island National Park Preserve, Canada. Using a 5‐year, spatially explicit, mark‐resight dataset and hierarchical mixed‐effects linear modeling, we evaluated the influence of adult sex ratio (ASR) on mating success and then tested for effects of freshwater availability, density, unpaired male abundance, and precipitation during each breeding season. Unpaired male abundance, freshwater availability, and ASR differed in their effects on male mating success according to year and selection episode. Opportunity for sexual selection in males associated with harem acquisition increased with ASR, and unpaired male abundance further explained weather‐related interannual variation after accounting for ASR. In contrast, once a harem was secured, ASR had little effect on male mating inequality in regard to acquiring additional females, while interannual variation in mating inequality increased with decreasing freshwater availability. Our findings show that local demography, resource availability, and weather effect opportunity for sexual selection in males differently depending on selection episode, and can attenuate or accentuate effects of ASR.

Summary: The polygyny threshold (PT) is a critical transition point in the sexual selection process for many organisms in natural populations, characterizing when females choose to mate with an already mated male over an unmated one to improve fitness. Understanding its causes and consequences is therefore of high interest. While both theoretical and empirical work suggest that the degree of polygyny within a species is plastic and a function of male inequality, the functional relationship between underlying availability of resources occupied by breeding males under variable climatic conditions and the dynamics of PTs across space and time has received less attention. Here, we use a standardized measure of male mating inequality as the culmination of female mate choices to analyse how spatially dynamic PTs in a naturally regulated feral horse (Equus ferus caballus) population emerge along a geographic gradient in a known, limiting resource (freshwater) each year from variable climatic conditions. Polygyny threshold distance from permanent freshwater increased with increasing precipitation during the breeding season of each year, suggesting a relationship between annual resource availability and female mate choice. The mechanism by which climatic conditions underpin the spatial dynamics of PTs was likely through precipitation providing ephemeral freshwater sources across the study area that effectively weakened the gradient in availability of permanent freshwater, thereby providing mating males that occupied home ranges far from permanent water with access to this limiting resource and enabling them to attract and retain females. Increased precipitation also coincided with a decreased proportion of males in the population that experienced sexual selection pressure attributed to female mate choice in relation to the acquisition and/or defence of freshwater sources. Climatic conditions caused spatial shifts in PTs annually along the geographic gradient in resource availability. Our findings reveal that such environmental gradients may either buffer or amplify impacts of climatic variation on selection pressure operating in natural populations, and emphasize the importance of integrating spatially explicit PTs with atmospheric fluctuations when predicting the effect of climatic change on selection processes within populations that occupy environmental gradients.