Investigating species incidence over habitat fragments of different areas—a look at error estimation

The use of incidence functions and their error structure is explored as a means of interpreting patterns present in fragmented systems. Incidence functions describe the probability of a species' presence on a fragment. The only information required for an incidence function is presence/absence data for a number of fragments of known size. Methods are developed for establishing prediction bounds on the incidence function. The example developed uses data from mammals on isolated mountaintops. Distributions of number of species expected on a fragment predicted the actual number of species well, but prediction of identities of species on small fragments was poor. Although the number of species expected on an assembly of small fragments compared to a single large fragment of the same total area was nearly always equal, the identity of species differed. Species with large area requirements were never found on any number of small fragments; species which occurred with a medium probability over most fragments had a higher probability of being present in an assembly of small fragments than on a single large fragment.     

SOCIAL BEHAVIOUR AND MASS MORTALITY IN THE BASAL CERATOPSIAN DINOSAUR PSITTACOSAURUS (EARLY CRETACEOUS, PEOPLE'S REPUBLIC OF CHINA)

Abstract:  An exceptionally preserved herd of the ceratopsian dinosaur Psittacosaurus was recovered from the Lujiatun Beds of the Lower Cretaceous Yixian Formation, Liaoning Province, north-east China. This specimen provides the earliest direct evidence of post-nestling gregarious behaviour in this important dinosaur clade. The sediment in which the skeletons occur represents a lahar (volcanic mudflow), indicating that the six individuals present were entombed simultaneously during a catastrophic mass mortality event. Reconstruction of the herd age profile shows it was composed of offspring from at least two clutches, revealing that group fidelity in these dinosaurs extended beyond time spent together in the nest. This demonstrates that sociality appeared much earlier in ceratopsian evolution than is generally acknowledged and that such behaviour preceded the evolution of the elaborate horns and frills seen in derived ceratopsids.     

Noninvasive Estimation of Black Bear Abundance Incorporating Genotyping Errors and Harvested Bear

ABSTRACT Estimating black bear (Ursus americanus) population size is a difficult but important requirement when justifying harvest quotas and managing populations. Advancements in genetic techniques provide a means to identify individual bears using DNA contained in tissue and hair samples, thereby permitting estimates of population abundance based on established mark-capture-recapture methodology. We expand on previous noninvasive population-estimation work by geographically extending sampling areas (36,848 km²) to include the entire Northern Lower Peninsula (NLP) of Michigan, USA. We selected sampling locations randomly within biologically relevant bear habitat and used barbed wire hair snares to collect hair samples. Unlike previous noninvasive studies, we used tissue samples from harvested bears as an additional sampling occasion to increase recapture probabilities. We developed subsampling protocols to account for both spatial and temporal variance in sample distribution and variation in sample quality using recently published quality control protocols using 5 microsatellite loci. We quantified genotyping errors using samples from harvested bears and estimated abundance using statistical models that accounted for genotyping error. We estimated the population of yearling and adult black bears in the NLP to be 1,882 bears (95% CI = 1,389-2,551 bears). The derived population estimate with a 15% coefficient of variation was used by wildlife managers to examine the sustainability of harvest over a large geographic area.     

Population Dynamics and Behavior of Bighorn Sheep with Infectious Keratoconjunctivitis

ABSTRACT Introduced disease is a major mortality factor in some populations of bighorn sheep (Ovis canadensis). Epizootics of infectious keratoconjunctivitis (IKC) and contagious ecthyma occurred in bighorn sheep in the Silver Bell Mountains of south-central Arizona, USA, from 1 December 2003 to 31 March 2004. Our objectives were to 1) investigate the influence of the epizootic on abundance and demographics and 2) examine how IKC affected the mortality, behavior, and movements of clinically affected animals. Morbidity was 39%, and all sex and age classes were affected. The population declined 23%, with most mortality in the adult female (1 M, 11 F) segment of the population. Of the diseased animals that were marked (n = 27), 44% recovered and 44% died. Predation (50%) and starvation (33%) were the primary causes of mortality of diseased bighorn sheep. Bighorn sheep that were infected spent less time feeding and moved less than noninfected animals during the epizootic. Managers might be able to minimize losses of infected animals through predator control. To minimize losses to starvation, managers should refrain from any activity that disturbs infected animals (including treatment) because disturbances increase energy expenditures and expose infected animals to injury.     

Survival of Breeding Pacific Common Eiders on the Yukon-Kuskokwim Delta,Alaska

ABSTRACT Populations of Pacific common eiders (Somateria mollissima v-nigrum) breeding in Alaska, USA, have declined markedly over the past 40 years. We studied survival of adult female Pacific common eiders using capture—recapture of nesting hens at 3 sites on the Yukon-Kuskokwim Delta (YKD), Alaska from 1994 to 2004. We used data consisting of 268 recapture events from 361 uniquely marked individuals to investigate temporal, geographic, and environmental variation in adult female survival. Our results suggest apparent annual survival of adult eiders from the YKD was high (0.892, SE = 0.022) and spatially and temporally invariant (σ² = 0.005), a pattern consistent with other long-lived marine birds. Moreover, our results suggest adult survival may be functionally fixed for Pacific common eiders, and at the present, adult survival may be relatively unresponsive to environmental or management perturbations. Our data did not support hypothesized variation in survival relative to mortality factors such as predation on breeding grounds, physiologic costs of reproduction, and wintering conditions. Although changes in adult survival likely have a large potential effect on prospective population growth, our results suggest viable management actions aimed at increasing survival may be extremely limited.     

Rapid Homogenization of Multiple Sources: Genetic Structure of a Recolonizing Population of Fishers

Abstract: Fishers (Martes pennanti) were extirpated from much of southern Ontario, Canada, prior to the 1950s. We hypothesised that the recent recolonization of this area originated from an expansion of the population in Algonquin Provincial Park, which historically served as a refuge for fishers. To test this hypothesis, we created a sampling lattice to encompass Algonquin and the surrounding area, and we collected contemporaneous DNA samples. We sampled fishers from each of 35 sites and genotyped them at 16 microsatellite loci. Using a Bayesian assignment approach, with no a priori geographic information, we inferred 5 discrete genetic populations and used genetic population assignment as a means to cluster sites together. We concluded that the Algonquin Park fisher population has not been a substantial source for recolonization and expansion, which has instead occurred from a number of remnant populations within Ontario, Quebec, and most recently from the Adirondacks in New York, USA. The genetic structure among sampling sites across the entire area revealed a pattern of isolation-by-distance (IBD). However, an examination of the distribution of genetic structure (F_ST/1^- F_ST) at different distances showed higher rates of gene flow than predicted under a strict IBD model at small distances (40 km) within clusters and at larger distances up to 100 km among clusters. This pattern of genetic structure suggests increased migration and gene flow among expanding reproductive fronts.     

Estimating abundance of introduced Chinese muntjac Muntiacus reevesi and native roe deer Capreolus capreolus using portable thermal imaging equipment

• 1 Managing the conservation impacts of deer requires knowledge of their numbers. However, estimating densities in forested areas is problematic, with pellet‐group‐based methods subject to error and uncertainty in estimating defecation and decay rates in addition to sampling variance. Use of thermal imaging equipment allows direct census by distance sampling.
• 2 Densities of introduced Chinese muntjac Muntiacus reevesi and native roe deer Capreolus capreolus were estimated in 12.8 km² of conifer forest in eastern England by thermal imaging distance transects. Estimated density of introduced muntjac (±95% confidence intervals [CI]: 20 ± 8 km⁻²) exceeded that of native roe deer (16 ± 6 km⁻²); 95% CI of c. 40% were achieved in 10 days of fieldwork.
• 3 Density estimates were not sensitive to the number of width bands applied during analysis. Detectability functions differed, with narrower effective strip widths (ESW) for muntjac (74 m) than roe deer (123 m). Thus, it is important to discriminate between species when censusing mixed assemblages. Detectability and ESW also differed among plantation growth stages. Stratification by habitat may therefore improve accuracy of density estimates but would require additional survey effort.

     

Determinants of preferred intertidal feeding habitat for Eastern Curlew: A study at two spatial scales

Abstract Broadscale habitat use by Eastern Curlews (Numenius madagascariensis) in their non‐breeding range in eastern Australia was assessed using low tide surveys on feeding grounds, where 60 skilled volunteers made repeated counts of the birds on intertidal flats, across 41% (9500 ha) of the intertidal habitat within Moreton Bay, Australia. We analysed 32 defined sections of intertidal flat, of roughly equal area (mostly 200–400 ha), which varied greatly in their curlew density (2–47 birds per 100 ha) and also in substrate and other environmental features. Sites with the least resistant substrates had densities three times those with the most resistant substrates. Of 10 environmental characteristics measured for each site, substrate resistance was the best predictor of curlew density (r² = 0.45). Characteristics that were poor predictors included distance to the nearest roost, level of human disturbance and distance to urban settlement. For a finer‐scale assessment, microhabitat use and feeding behaviour were recorded during low tide within 12 intertidal flats, which varied in size (23–97 ha), substrate, topography and other features. Across all flats, curlews strongly preferred to feed relatively close (0–50 m) to the low‐water line. They fed on a variety of substrates (including sand, sandy‐mud, mud and seagrass) in broadly similar proportions to their occurrence in the habitat. There was a statistically significant preference for sand, although its magnitude was not strong. These results indicate that curlews select habitat most strongly at a between‐flat rather than within‐flat scale.