Recapture Analysis Research Articles

Spotted! Computer-aided individual photo-identification allows for mark-recapture of invasive spotted lanternfly (Lycorma delicatula).

The spotted lanternfly is an invasive pest for which we lack individual movement data due in part to the difficulty posed by individual identification. We developed a computer-aided method to identify individual adult spotted lanternfly using wing spot patterns from photos processed in the software I3S and demonstrated the method's accuracy with lab and field validations. Based on 176 individuals in the lab, we showed that digitizing the spots of one wing allowed a 100% reliable individual identification. The errors due to user input and the variation in the angle of the image were largely negligible compared to inter-individual variations. We applied this method in the context of a mark-recapture experiment to assess the feasibility of this method in the field. We initially identified a total of 84 unique spotted lanternflies, 31 of which were recaptured after four hours along with 49 new individuals. We established that the analysis of recaptures can possibly be automated based on scores and may not require systematic visual pairwise comparison. The demonstration of the effectiveness of this method on relatively small sample sizes makes it a promising tool for field experimentation as well as lab manipulations. Once validated on larger datasets and in different contexts, it will provide ample opportunity to collect useful data on spotted lanternfly ecology that can greatly inform management.

Drivers of large carnivore density in non‐hunted, multi‐use landscapes

AbstractProtected areas serve as population strongholds for many large carnivores, with multi‐use landscapes along their borders forming the front‐lines of wildlife conservation. Understanding large carnivore population dynamics within working landscapes is difficult where anthropogenic mortality is high and unregulated. This study focused on working ranches, where killing jaguars (Panthera onca) and their prey was prohibited, to gain insight into jaguar population potential across multi‐use landscapes. Faced with forest fragmentation, presence of domestic livestock, and dynamic land‐use practices, we expected jaguar populations in working landscapes to be predominantly male and transient, with low cub production, and inflated population densities in remnant forest patches, versus protected areas where we expected native forest habitat and stable jaguar territories. Using camera traps and spatial‐capture recapture analyses, we observed that male jaguars demonstrated larger‐scale movements and were more detectable than females (0.07 ± 0.01 SE vs. 0.02 ± 0.01 SE) in both working and protected landscapes. Female jaguars in ranches traveled farther than females in parks. Carnivore density increased with forest cover and wild prey activity, decreased with domestic prey activity, and was marginally higher in ranches (4.08 individuals/100 km2 ± 0.73 SE) than in parks (3.59 individuals/100 km2 ± 0.64 SE). Females outnumbered males in both landscapes (2.20–2.60 females/100 km2vs. ~1.60 males/100 km2), although local male density reached up to 11.00 males/100 km2in ranches (vs. 3.50 males/100 km2in parks). While overall jaguar density was patchier in protected areas ( = 0.69 parks, 0.54 ranches), inter‐annual patchiness was higher within ranches (Moran'sI = 0.49–0.60 ranches, 0.69–0.70 parks), reflecting changes in cattle management. Despite major habitat alterations, working landscapes can support carnivore densities equivalent to (or exceeding that of) unmodified forest habitat, provided that wildlife‐tolerant ranching practices are maintained.

Breastfeeding and Risk of Late-Onset Group B Streptococcal Disease.

Group B Streptococcus (GBS) is a major contributor to neonatal sepsis worldwide. Late-onset group B Streptococcus disease (LOGBS) and its risk factors remain poorly understood. The isolation of GBS from breast milk has been described in cases of LOGBS. This potential association has raised concerns for mothers and clinicians regarding the safety of ongoing breastfeeding. In this study, we aimed to investigate whether exposure to breast milk is associated with increased risk of LOGBS. A case-control study of LOGBS was conducted across 4 hospital networks in Victoria, Australia, including the 2 major tertiary pediatric centers in the state, to evaluate 11 years of data (2007-2017). Cases were captured initially from microbiology databases and recaptured with International Classification of Diseases discharge coding. Each case patient was matched with 4 controls to assess feeding status. Patients were matched for chronological age, gestation, discharge status, recruitment site, and calendar year. We identified 92 cases of LOGBS: 73 cases on initial capture and 76 cases on the recapture analysis. Case patients were matched with 368 controls: 4 controls to each patient. Seventy-two patients were exposed to breast milk at the time of LOGBS (78.3%), compared with 274 controls (74.5%; odds ratio 1.2 [95% confidence interval 0.7-2.3]). Breastfeeding was not associated with increased risk of LOGBS. Breast milk should not be tested for GBS during a first episode of LOGBS.

Canada goose gosling survival of the Atlantic Flyway Resident Population

ABSTRACTGosling losses account for the majority of summer mortality for Canada geese (Branta canadensis), but survival at this stage can be difficult to estimate because of their small size, precocial behavior, and the land cover in which they live. Previous methods of measuring gosling survival often used individual markers, which can bias estimates when not accounting for total brood loss or emigration. We estimated gosling survival of Canada geese in the Atlantic Flyway Resident Population (AFRP) in New Jersey, USA, during 2009–2010 through use of marked parents and young to incorporate total and partial brood losses. The proportion of marked parents who lost their entire brood occurring during the first 3 weeks after hatch and prior to banding was 0.316. Gosling survival that accounted for partial brood loss was 0.461 ± 0.027 (SE), and was most influenced by nest density and the percent agriculture land use within 215 m of the nest site. The gosling survival estimate incorporating total and partial brood losses during this study was 0.315 ± 0.018. Acquiring current reproductive vital rates will assist in understanding the dynamics of recruitment as a function of population size. The above information, in combination with nest survival and annual survival estimates from band recovery and recapture analyses, has been used to inform a population model for Canada geese in the AFRP. © 2018 The Wildlife Society.

Daily Mass Changes in Landbirds During Migration Stopover on the South Shore of Lake Ontario

AbstractAssigning conservation priorities to areas used by birds during migration requires information on the relative quality of areas and habitats. The rate at which migratory birds replenish energy reserves during stopover may be used as an indicator of stopover-site quality. We estimated the rate of mass gain of 34 landbird species during stopover at a near-shore terrestrial site on the south shore of Lake Ontario in New York during 12 migration seasons from 1999 to 2004. The average rate of mass gain was estimated by relating a measure of condition to time of capture (hour after sunrise) with linear regression. Data from 25,385 captures were analyzed. Significantly positive rates of mass change were detected for 20 of 30 species during spring migration and 19 of 21 species during autumn migration. No significantly negative trends were detected in either season. Daily rates of mass gain across all species averaged 9.84% of average lean body weight during spring migration and 9.77% during autumn migration. Our regression estimates were significantly greater than estimates from traditional analyses that examine mass changes in recaptured birds. Analyses of mass changes in recaptured birds revealed a mean daily change of −0.68% of average lean mass in spring and 0.13% in autumn. Because of sampling biases inherent in recapture analyses, the regression approach is likely more accurate when the assumptions of the method are met. Similar studies in various habitats, landscapes, and regions are required to prioritize conservation efforts targeting migratory stages of the annual cycle.Cambios de Peso Diarios de Aves Terrestres durante las Paradas Migratorias en la Costa sur del Lago Ontario

Effects of Backpack Radio Tags on Tawny Owls

Radiotelemetry is an important tool in many studies of bird behavior and ecology. Additionally, long-lived radio tags, mounted as backpacks, enable survival to be estimated with higher precision and less sampling bias than studies based on band returns (Kenward 1993; Kenward et al. 1999, 2000). Any tag will inevitably increase the energetic costs of flight due to the additional weight and aerodynamic drag (Pennycuick et al. 1989), but due to their larger size and weights, backpack radio tags have higher potential for affecting the birds negatively than leg bands or radio tags attached to the tail feathers (Calvo and Furness 1992). In backpack mounts, the harness may also increase energy expenditures during flight due to friction between harness and plumage (Gessaman and Nagy 1988), as well as decrease agility and increase heat loss through distortion of the plumage. Poorly fitting mounts may cause abrasions, and birds might become tangled in vegetation (e.g., examples in Foster et al. 1992). Special concerns about application of radio tags is required in studies of fledgling birds; backpack tags are more difficult to attach because extra slack in the harness is required to enable further growth, and wings are not fully developed at fledging, which may augment the effect of the weight load of the transmitter. Juveniles are therefore likely to be more sensitive to tag effects than adults. Accordingly, any study drawing inferences about demographic parameters from radiotagged individuals should address the potential influence of the tags on their estimates, especially if backpacks are used. Despite the limited number of field studies addressing tag problems, several have found radiotagging to have a negative influence on reproductive success (e.g., Foster et al. 1992, Marzluff et al. 1997, Gregory et al. 2003, Phillips et al. 2003), survival (e.g., Longcore et al. 1991, Reynolds et al. 2004), or both (e.g., Paton et al. 1991, Paquette et al. 1997; see Calvo and Furness [1992] for a review of tag-effects in studies published before 1991). Particular concerns have been raised about the effects of backpack tags on owls because all 3 studies (Paton et al. 1991, Foster et al. 1992, Petty et al. 2004) testing the effects of backpack tags on demographic parameters have found significant negative effects. Foster et al. (1992) found lower reproductive success of tagged individuals in 9 of 10 studies of spotted owls (Strix occidentalis) in Oregon, USA, and Washington, USA—4 of these differences being significant—although backpack tags did not appear to affect survival. In California, Paton et al. (1991) found female spotted owl survival affected negatively by backpack tags in 1 of 2 years, and there were negative effects on reproductive success in both of 2 succeeding years. As a consequence, capture– recapture data obtained from radiotagged individuals have been discarded from demographic analyses on spotted owls (Forsman et al. 1996, Franklin et al. 1996). Petty et al. (2004) reported that juvenile tawny owls in England fitted with backpack tags prior to fledging having substantially lower recruitment probability than a control group of untagged juveniles, as tested with capture–mark– recapture analysis. Based on this result and a review of published information about survival and recruitment rates of juvenile tawny owls and spotted owls with radio tags, they strongly opposed using backpack tags on juveniles in any Strix species before the impact of tags have been further investigated. Herein, I evaluate the effects of backpack radio tags on body mass, survival, and reproduction of adult tawny owls, surveyed over 6 breeding seasons (1998–2003) in Denmark. Based on data from a single year, I also assess the effects of backpack tags on survival of fledged juveniles as compared with an untagged control group.

MODELING DISPERSAL WITH CAPTURE–RECAPTURE DATA: DISENTANGLING DECISIONS OF LEAVING AND SETTLEMENT

Increasing habitat fragmentation has led population ecologists to consider dispersal as a key process for population functioning and persistence. However, due to logistic and methodological problems, dispersal rates within fragmented populations have rarely been estimated, leaving many unanswered questions about the role of dispersal and the factors affecting dispersal. Recently developed multistrata capture–recapture models allow the estimation of dispersal probabilities from the analysis of recaptures or recoveries of marked individuals. Despite their undoubted efficiency at estimating dispersal rates, their contribution to the investigation of dispersal processes at the individual level is presently limited by a lack of flexibility in their parameterization. In this paper, a new parameterization of these models is presented in which the probability of leaving the site of origin and the probability that an emigrant settles on a given recipient site are modeled separately. This parameterization is then used to address the influence of local perturbations on site fidelity and settlement decisions of emigrants in a subdivided population of Black-headed Gulls, Larus ridibundus. The parameterization introduced here accurately describes dispersal probabilities whenever they result from a two-step decision-making process (i.e., when choice of a settlement site only occurs after a decision has been made to leave the current site). Furthermore, this parameterization permits investigators to disentangle hypotheses about these two components of dispersal behavior. Corresponding Editor: P. Legendre.