Lower Apparent Survival Research Articles

Rainfall and population dynamics of Grey Pileated Finch Coryphospingus pileatus (Aves: Passeriformes) in a Neotropical dry forest

AbstractIn tropical dry environments rainfall periodicity may affect demographic parameters, resulting in fluctuations in bird abundance. We used capture–recapture data for the Grey Pileated Finch from a Neotropical dry forest to evaluate the hypothesis that intra‐ and inter‐annual survival, individuals entrance and population abundance, are related to local rainfall. Sampling occurred across 3 years, with individuals captured, tagged and evaluated for age and presence of brood patch every 14 days. Using the POPAN formulation, we generated demographic models to evaluate study population temporal dynamics. Best‐fit models indicated a low apparent annual survival in the first year (16%) compared to other years (between 47 and 62%), with this low value associated with an extreme drought. The abundance of juveniles at each capture occasion was significantly dependent on the accumulated precipitation in the previous 14 days, and the juvenile covariate was a strong predictor of the intra‐annual entrance probability (natality). Individuals entrance during the reproductive period corresponded to 53, 52 and 75% of total ingress for each year, respectively. The trend in sampled population size indicated positive exponential growth (Ninitial = 50, Nlast = 600), with intra‐annual fluctuations becoming progressively more intense. Low survival was relevant during population decline at study onset, while at study end intense Individuals entrance promoted rapid population growth. Thus, the indirect effects of rainfall and the combined effect of two demographic rates operated synergistically on the immediate population abundance of Grey Pileated Finch, an abundant bird in a Neotropical dry forest.

Drivers of demographic decline across the annual cycle of a threatened migratory bird

Migratory species are rapidly declining but we rarely know which periods of the annual cycle are limiting for most species. This knowledge is needed to effectively allocate conservation resources to the periods of the annual cycle that best promote species recovery. We examined demographic trends and response to human footprint for Canada warblers (Cardellina canadensis), a threatened Neotropical migrant, using range-wide data (1993–2016) from the Monitoring Avian Productivity and Survivorship (MAPS) program on the breeding grounds. Declines in abundance were steepest in the eastern breeding region, followed by the western region. Breeding productivity did not decline in any region. In contrast, we observed declining recruitment in all regions, low apparent survival in the east and west, and a decline in apparent survival in the east. Abundance declined with increasing disturbance around MAPS stations. Between 1993 and 2009, the human footprint index on the breeding range increased by 0.11% in contrast to a 14% increase on the wintering range. Landscape-scale disturbance on the breeding grounds may influence abundance in some regions; however, the observed trends in demography and footprint suggests limitation during the non-breeding period as the likely driver of overall declines, particularly for eastern populations.

Extreme drought alters frequency and reproductive success of floaters in Willow Flycatchers

ABSTRACT Changes in habitat quality, including those caused by extreme events like droughts and floods, could alter costs and benefits of territoriality and thereby the prevalence and reproductive consequences for individuals capable of breeding that do not do so (floaters). We studied floating behavior in a population of Southwestern Willow Flycatchers (Empidonax traillii extimus) in central Arizona during one year of extreme drought, one year of lake inundation, and three years of near average precipitation. In all years, most floaters were second year (SY) males, and most subsequently settled outside of the patch where they were detected in the floating year, suggesting that floaters did not “queue” at high-quality territories in order to achieve higher reproductive success in subsequent years. Instead, cohorts that floated in non-drought years had lower apparent survival and lower reproductive success compared to territorial birds. In the extreme drought year, however, the number of floaters was 1.5 t...

Spatial and temporal drivers of avian population dynamics across the annual cycle.

Untangling the spatial and temporal processes that influence population dynamics of migratory species is challenging, because changes in abundance are shaped by variation in vital rates across heterogeneous habitats and throughout the annual cycle. We developed a full-annual-cycle, integrated, population model and used demographic data collected between 2011 and 2014 in southern Indiana and Belize to estimate stage-specific vital rates of a declining migratory songbird, the Wood Thrush (Hylocichla mustelina). Our primary objective was to understand how spatial and temporal variation in demography contributes to local and regional population growth. Our full-annual-cycle model allowed us to estimate (1) age-specific, seasonal survival probabilities, including latent survival during both spring and autumn migration, and (2) how the relative contribution of vital rates to population growth differed among habitats. Wood Thrushes in our study populations experienced the lowest apparent survival rates during migration and apparent survival was lower during spring migration than during fall migration. Both mortality and high dispersal likely contributed to low apparent survival during spring migration. Population growth in high-quality habitat was most sensitive to variation in fecundity and apparent survival of juveniles during spring migration, whereas population growth in low-quality sites was most sensitive to adult apparent breeding-season survival. These results elucidate how full-annual-cycle vital rates, particularly apparent survival during migration, interact with spatial variation in habitat quality to influence population dynamics in migratory species.

Apparent survival, territory turnover and site fidelity rates in Northern Goshawk Accipiter gentilis populations close to the northern range limit

ABSTRACTCapsule: Mark–recapture data suggest low apparent survival and sex- and population-specific site fidelity and territory turnover in adult Northern Goshawks Accipiter gentilis breeding in northern Europe.Aims: To understand how species cope with global environmental change requires knowledge of variation in population demographic rates, especially from populations close to the species’ northern range limit and from keystone species such as raptors. We analyse apparent survival and breeding dispersal propensity of adult Northern Goshawks breeding in northern Europe.Methods: We used long-term mark–recapture data from two populations in Finland, northern Europe, and Cormack–Jolly–Seber models and binomial generalized linear models to investigate sex- and population-specific variation in apparent survival, territory turnover and site fidelity.Results: We report low apparent survival (53–72%) of breeding adult Goshawks. Breeding dispersal propensity was higher in females than males, especially in northern Finland, contrasting with previous studies that suggest high site fidelity in both sexes.Conclusion: Low apparent survival in females may be mainly due to permanent emigration outside the study areas, whereas in males the survival rate may truly be low. Both demographic aspects may be driven by the combination of sex-specific roles related to breeding and difficult environmental conditions prevailing in northern latitudes during the non-breeding season.

The plight of a plover: Viability of an important snowy plover population with flexible brood care in Mexico

Shorebird populations often rely on wetland habitats, for which they are considered important indicators of ecosystem health. Populations residing at low latitudes remain vastly understudied in comparison with populations from high latitudes. Here we use detailed behavioural and demographic observations during all life stages in combination with stage specific modelling to predict the population trajectory of a snowy plover (Charadrius nivosus) population at Bahía de Ceuta, Sinaloa, Mexico. In North America this shorebird is threatened, with many monitored populations declining. Our stochastic matrix model for the Ceuta population, which closely matched our field observations, suggests that the population is a sink with a 99.8% probability of going extinct within 25years. Low apparent adult survival, which declined over time presumably because of poor reproductive success and/or permanent emigration in response to habitat degradation, had the largest impact on the population trajectory. We recommend urgent habitat management actions to address volatile water levels and hence increase reproductive success of this species at this important breeding site. Acknowledging the relative effects of flexible brood care on individual fitness and population dynamics presents an intriguing dilemma for conservation. We found that the flexible parental care system of snowy plovers affected chick survival: broods deserted by polyandrous females early after hatching had significantly lower survival than broods not deserted or those deserted late. Overall, deserting females raised fewer fledglings in this population than females that cared. Taken together, our study reveals unsustainable variation in local vital rate dynamics. To understand how this population contributes to regional source-sink dynamics, future research should evaluate the importance of immigration and emigration among neighbouring populations.

First demographic estimates for endangered Florida bonneted bats suggest year-round recruitment and low apparent survival

First demographic estimates for endangered Florida bonneted bats suggest year-round recruitment and low apparent survival

Low Apparent Survival and Heterogeneous Movement Patterns of Invasive Blue Catfish in a Coastal River

AbstractBlue CatfishIctalurus furcatuswere purposefully introduced into freshwater tributaries to Chesapeake Bay in the past, and populations have subsequently spread to new areas, negatively impacting native communities and causing concern for resource managers. To aid development of management strategies, we implemented a multiyear (2012–2015) tagging study of invasive Blue Catfish in a 40‐km stretch of the Potomac River to estimate survival and assess movement patterns. Blue Catfish (N= 1,237) were captured by electrofishing and double‐tagged to allow us to estimate tag retention rates; we used reward tags to increase reporting rates. Recaptured fish (N= 104; 8.4% return rate) were at large for between 2 and 1,208 d. Tag retention rates were 0.88 (SE = 0.045) after 1 year and declined to 0.31 (SE = 0.107) after 2.7 years. The mean minimum distance moved by fish was 24.1 km (range = 0.0–112.6 km). Most (63%) fish displayed downriver movements, but distance moved was unrelated to fish size or days at large. Greater distances were observed among fish that moved downriver (34.4 km) than those that moved upriver (6.7 km). These results suggest high variability in movement behaviors for Blue Catfish inhabiting the tidal Potomac River from freshwater reaches to estuarine habitats. We estimated an annual apparent survival rate of 0.56 (SE = 0.057; Brownie tag‐return model) across the study period. This survival rate is lower than survival rates reported from their native range. Long‐distance movements of Blue Catfish in the Potomac River indicate that robust, large‐scale control measures will be needed to reduce population abundance and minimize negative impacts of this species on native communities.

Population Trends, Survival, and Sampling Methodologies for a Population of Rana draytonii

Abstract Estimating population trends provides valuable information for resource managers, but monitoring programs face trade-offs between the quality and quantity of information gained and the number of sites surveyed. We compared the effectiveness of monitoring techniques for estimating population trends of Rana draytonii (California Red-legged Frog) at Point Reyes National Seashore, California, USA, over a 13-yr period. Our primary goals were to: 1) estimate trends for a focal pond at Point Reyes National Seashore, and 2) evaluate whether egg mass counts could reliably estimate an index of abundance relative to more-intensive capture–mark–recapture methods. Capture–mark–recapture (CMR) surveys of males indicated a stable population from 2005 to 2009, despite low annual apparent survival (26.3%). Egg mass counts from 2000 to 2012 indicated that despite some large fluctuations, the breeding female population was generally stable or increasing, with annual abundance varying between 26 and 130 individuals....

Forbidden fruit: human settlement and abundant fruit create an ecological trap for an apex omnivore.

Habitat choice is an evolutionary product of animals experiencing increased fitness when preferentially occupying high-quality habitat. However, an ecological trap (ET) can occur when an animal is presented with novel conditions and the animal's assessment of habitat quality is poorly matched to its resulting fitness. We tested for an ET for grizzly (brown) bears using demographic and movement data collected in an area with rich food resources and concentrated human settlement. We derived measures of habitat attractiveness from occurrence models of bear food resources and estimated demographic parameters using DNA mark-recapture information collected over 8years (2006-2013). We then paired this information with grizzly bear mortality records to investigate kill and movement rates. Our results demonstrate that a valley high in both berry resources and human density was more attractive than surrounding areas, and bears occupying this region faced 17% lower apparent survival. Despite lower fitness, we detected a net flow of bears into the ET, which contributed to a study-wide population decline. This work highlights the presence and pervasiveness of an ET for an apex omnivore that lacks the evolutionary cues, under human-induced rapid ecological change, to assess trade-offs between food resources and human-caused mortality, which results in maladaptive habitat selection.

Survival of Sooty Falcons (Falco concolor) breeding in Oman

Although the Middle East supports a high level of avian biodiversity, the ecology of relatively few species that use the region has been studied in detail. Despite its restricted breeding distribution in the Middle East, and apparent unfavorable conservation status, little is known about the population ecology of the Sooty Falcon (Falco concolor), one of only two falcon species that breeds in the boreal summer. We applied multi-state models to capture–mark–recapture data collected during 2007–2014 in the Sultanate of Oman to estimate, for the first time, the probabilities of capture, age-specific breeding probabilities, and state-specific apparent survival for Sooty Falcon. Capture probability for breeding adults (±1SE) was 0.443 ± 0.088. Annual apparent survival probability for pre-breeders and for breeding adults was 0.570 ± 0.048 and 0.656 ± 0.069, respectively. The probability that 2-, 3-, and 4-year-old falcons returned as breeders was 0.065 ± 0.036, 0.159 ± 0.069, and 0.339 ± 0.211, respectively. In 2013, we radio-tagged five fledgling falcons, and monitored their fates using satellite-based tracking. All initiated their first migration and survived for 48 days following radio-tagging, but four of the five birds died by 70 days post-tagging; only one survived >100 days. Our results suggest that only about 12 % of fledglings survive to the average age of first breeding (~3.8 years), and that most of first-year mortality occurs during their first migration or soon after they reach their destination. Low apparent survival of pre-breeders could result in low recruitment to the breeding population, and population declines. A comprehensive population-level assessment is urgently needed to accurately determine the status of Sooty Falcons, and to devise flyway-scale conservation plans.

Apparent survival of North Atlantic right whales after entanglement in fishing gear

The impacts of human activities on cryptic marine species can be difficult to assess. The North Atlantic right whale is an endangered species numbering just over 500 individuals. Entanglement in fishing gear is one documented source of injury and mortality, but population-level effects have been difficult to quantify. We used documented entanglements, long-term population studies and mark-recapture statistical techniques to evaluate the effect of these events on North Atlantic right whale survival. Estimates were based on 50 individuals observed carrying entangling gear between 1995 and 2008, and compared to 459 others that were never observed with gear during the same period. Entangled adults had low initial apparent survival (0.749, 95% CI: 0.601–0.855), but those that survived the first year achieved a survival rate (0.952, 95% CI: 0.907–0.977) that was more comparable to unaffected adult females (0.961, 95% CI: 0.941–0.974) and males (0.986, 95% CI: 0.975–0.993). Juveniles had a post-entanglement survival rate that was comparable to the initial survival of entangled adults (0.733, 95% CI: 0.532–0.869) and lower than un-impacted juveniles (0.978, 95% CI: 0.969–0.985). Of three entanglement characteristics examined, health impacts were most predictive of subsequent survival, but the entanglement configuration and the resulting injuries also appeared to affect outcome. When the entanglement configuration was assessed as high risk, human intervention (disentanglement) improved the survival outcome. This is the first mark–recapture estimate of entanglement survival for any whale species. The results indicate the need for continued mitigation efforts for this species, as well as for a better understanding of entanglement impacts in other baleen whale populations.

The Osprey reintroduction in Central Italy: dispersal, survival and first breeding data

Capsule Sex-biased dispersal and an age-dependent effect in survival rate accounted for the pattern of first settlement and reproduction in a newly reintroduced Osprey population.Aims We estimate the survival of translocated individuals, describe juvenile movements and evaluate the success of first breeding events to document the re-establishment of an Osprey breeding population.Methods Between 2006 and 2010, 32 fledgling Ospreys were reintroduced via hacking techniques in Maremma Regional Park, Italy. We evaluated the effects of age on survival through multistate capture-mark-recapture analyses. Movements were investigated by radiotracking and using records of resightings.Results Survival was high for juveniles after the release (0.87), markedly decreased during the first winter (0.26), and improved again in subsequent years (annual apparent survival of 0.69 for immatures and 0.93 for adults). Mean distance covered in initial dispersal was greater for females (246.2 km) than for males (38.7 km).Conclusion Our results provided information on dispersal and survival rate of reintroduced Ospreys in a Mediterranean area. Despite low apparent survival in the first year, the high survival rates found in immatures and adults suggested favourable conditions for this new population. The study of demographic parameters is important for calibrating management actions aimed at the establishment of a self-sustaining Osprey population.

Apparent survival of adult Burrowing Owls that breed in Canada is influenced by weather during migration and on their wintering grounds

Understanding factors that influence the survival of endangered migratory species is critical for making informed management decisions, yet this understanding relies on long-term recapture datasets for species that are, by definition, rare. Using 3 geographically widespread (Saskatchewan, Alberta, and Manitoba, Canada) and long-term (6–15 yr) mark–recapture datasets, we quantified spatial and temporal variation in apparent annual survival and recapture probabilities of Burrowing Owl (Athene cunicularia), an endangered species that breeds in Canada. We then examined how large-scale weather patterns during migration (storms) and on the wintering and breeding grounds (precipitation), in addition to prey irruptions on the breeding grounds, influenced apparent survival of Burrowing Owls. Female Burrowing Owls had lower apparent survival than males in all 3 study areas. Storms during fall migration and above-average precipitation on the wintering grounds were associated with reduced apparent survival of Burrowing Owls in the longest-running study area, Saskatchewan; in Alberta and Manitoba, there were few correlations between apparent survival of Burrowing Owls and weather or prey irruptions. Increases in stochastic events such as storms during migration or precipitation on the wintering grounds could have adverse consequences on the already small Burrowing Owl population in Canada. Local management actions that focus solely on improving adult apparent survival within Canada are likely insufficient for mitigating susceptibility of adults to inclement weather or other factors outside the breeding season, underscoring the need for management of this species across multiple jurisdictions within North America.

The Whiskered Tern Chlidonias hybrida expansion in Poland: the role of immigration

AbstractThe Whiskered Tern population in Poland has rapidly increased from 40 breeding pairs in 1990 to over 1,600 in 2007, with strongest local population in the Upper Vistula River Valley. Owing to rather low pre-breeding and adult apparent survival rates estimated for this population (0.54 and 0.80, respectively) and a delay in accession to reproduction (recruitment completed at age 3), matrix modelling indicated an intrinsic growth rate ofλcalc = 1.02. Observed growth rates of both the Polish and the Upper Vistula River Valley populations wasλobs = 1.29. Using the deterministic population projection matrix including immigrant class, we estimated that, on average, 44 immigrants should enter the Upper Vistula River Valley population annually to match the observed growth. With survival rates increased (ΦP = 0.63,ΦB = 0.90) as to mimic no emigration and reduced dispersal, the estimated number of immigrants was only eight, indicating that substantial emigration rates are likely. A majority of the breeding sites were recorded in man-made water bodies. Colonisation has started in the southeast and proceeded towards the northwest. The strong, stable population in western Ukraine may explain high numbers of immigrants that could originate from there. Other factors favouring quick colonisation of Poland include availability of suitable breeding sites, the wide flexibility of the species with respect to breeding habitat, plentiful food, and high breeding success in the Upper Vistula River Valley. It also seems likely that westward shifts in both breeding and wintering ranges could add to the strong population increases in Eastern Europe.

Estimates of abundance and apparent survival of coastal dolphins in Port Essington harbour, Northern Territory, Australia

Context Three dolphin species occur in coastal waters of monsoonal northern Australia: the Australian snubfin (Orcaella heinsohni), humpback (Sousa sp.) and the bottlenose (Tursiops sp.). Their overall population size and trends are poorly known, and their conservation status has been difficult to resolve, but can be expected to deteriorate with likely increased development pressures. Aims We sought to provide an estimate of abundance, and apparent survival, of the three dolphin species at the largely undeveloped harbour of Port Essington (325 km2), Northern Territory, with repeated sampling over a 2.9-year period. Given increasing obligations to undertake population assessments for impact studies at proposed development sites, we assess the strengths and limitations of a systematic sampling program. Methods We used photo-identification data collected during systematic boat-based transect surveys undertaken from 2008 to 2010 and Pollock’s robust capture–recapture design model. Key results Total abundance estimates for the three species were variable across different sampling periods. The estimated number of individuals in the sampled area varied per sampling episode from 136 (s.e. 62) to 222 (s.e. 48) for snubfin, from 48 (s.e. 7) to 207 (s.e. 14) for humpbacks and from 34 (s.e. 6) to 75 (s.e. 9) for bottlenose dolphins. Apparent survival was estimated for snubfin at 0.81 (s.e. 0.11), humpbacks at 0.59 (s.e. 0.12) and bottlenose at 0.51 (s.e. 0.17) per annum. Key conclusions (1) The values derived here provide some of the only estimates of local population size for these species across monsoonal northern Australia; (2) population-size estimates varied considerably among seasons or sampling episodes; (3) the low apparent survival probabilities indicated that many individuals may move at scales larger than the study area; (4) density of snubfin and humpback dolphins in the present study area exceeded the few other estimates available for these species elsewhere in Australia. Implications The present study provided the first baseline estimates of abundance and apparent survival for three coastal dolphin species in monsoonal northern Australia. Such information is becoming increasingly important as development pressures intensify in coastal areas. Sampling protocols for future monitoring and impact assessment need an enhanced consideration of seasonality and scale issues.

Experimental support for food limitation of a short‐distance migratory bird wintering in the temperate zone

The Winter Food Limitation Hypothesis (WFLH) states that winter food abundance is a dominant source of population limitation of migratory birds. Evidence is accumulating that long-distance migratory birds wintering in tropical climates have high overwinter survival probabilities and that winter food limitation mainly affects their fitness nonlethally by limiting energetic reserves necessary for successful reproduction. In contrast, the relative roles of direct mortality vs. indirect effects caused by food limitation have not been investigated thoroughly on short-distance migratory birds wintering in temperate zones, where they face thermal challenges. We performed the first test of the WFLH for a temperate migratory bird in the wild on the Swamp Sparrow (Melospiza georgiana), with a replicated plot-wide food supplementation experiment. In contrast to tropical, but consistent with other temperate-wintering migrants, Swamp Sparrows on unmanipulated plots showed relatively low apparent survival across the winter. Following food addition, birds (1) immigrated to experimental plots, which subsequently supported approximately 50% higher abundances, (2) experienced increases of within-season apparent survival of 8-10%, depending on age/sex class, and (3) had higher-scaled mass index values, all supporting winter food limitation. The last two findings are interrelated because birds with higher scaled mass had higher survival probabilities, further supporting direct effects of winter food limitation. Food limitation of fat reserves might also have indirect effects on reproductive success by limiting migration timing and survival during migration. Increases in scaled mass were higher in females, suggesting that they are disproportionately affected by food limitation, possibly through competition. Based on Robust Design Modeling, we found no support for emigration prior to food addition, indicating that our estimates of mortality are unbiased.

Apparent survival of Snowy Plovers (Charadrius nivosus) varies with reproductive effort and year and between sexes

Abstract. Life history theory predicts a tradeoff between reproductive effort and survival, which suggests that some management practices aimed at increasing productivity may compromise population growth. We analyzed a 10-year data set of 225 individually marked Snowy Plovers (Charadrius nivosus), a threatened shorebird, to determine whether individual reproductive effort was correlated with low apparent survival. Most adults resided in the population an average of 2 years (range: 1–10 years), during which females laid 3–60 eggs, and both males and females invested considerable time in incubation and brooding. Apparent survival varied annually and was higher for males than for females. Contrary to theory, we found no evidence that increased reproductive effort, either current or cumulative, compromised survival. Instead, apparent survival was correlated positively with incubation time, which may be related to either high-quality individuals having high reproductive rates and high survival or permanent emi...

Survival rates in West African savanna birds

Despite widespread interest in life histories and the comparison of parameters between tropical and temperate regions, there are still relatively few multispecies studies assessing annual survival in Afrotropical species. We used data from systematic mist-netting of savanna birds in Nigeria, between 2001 and 2008, to estimate survival for 40 Afrotropical bird species. Best-supported models were those incorporating constant survival (27 of 40) or the effects of transience (13 of 40). Survival ranged from 0.269 to 0.948 (mean ± SE = 0.64 ± 0.02), varied within and between families, and showed a positive relationship with mass in passerines. Survival was highest in the insectivorous Malaconotidae (0.79 ± 0.13) and lowest in the granivorous Estrildinae (0.51 ± 0.04). This pattern was also evident in a comparison of survival between guilds (highest in insectivores and lowest in granivores) suggesting that these species encounter seasonal starvation risks or exhibit a seasonal response to water availability, i.e. emigration from the study area leading to reduced site fidelity and lower apparent survival. Our estimates of adult survival are higher than those previously obtained from this site, comparable with those from other Afrotropical studies (i.e. >0.60) and higher than those from temperate zones (0.53 ± 0.01, n = 79).

Photographic mark–recapture analysis of local dynamics within an open population of dolphins

Identifying demographic changes is important for understanding population dynamics. However, this requires long-term studies of definable populations of distinct individuals, which can be particularly challenging when studying mobile cetaceans in the marine environment. We collected photo-identification data from 19 years (1992-2010) to assess the dynamics of a population of bottlenose dolphins (Tursiops truncatus) restricted to the shallow (<7 m) waters of Little Bahama Bank, northern Bahamas. This population was known to range beyond our study area, so we adopted a Bayesian mixture modeling approach to mark-recapture to identify clusters of individuals that used the area to different extents, and we specifically estimated trends in survival, recruitment, and abundance of a "resident" population with high probabilities of identification. There was a high probability (p= 0.97) of a long-term decrease in the size of this resident population from a maximum of 47 dolphins (95% highest posterior density intervals, HPDI = 29-61) in 1996 to a minimum of just 24 dolphins (95% HPDI = 14-37) in 2009, a decline of 49% (95% HPDI = approximately 5% to approximately 75%). This was driven by low per capita recruitment (average approximately 0.02) that could not compensate for relatively low apparent survival rates (average approximately 0.94). Notably, there was a significant increase in apparent mortality (approximately 5 apparent mortalities vs. approximately 2 on average) in 1999 when two intense hurricanes passed over the study area, with a high probability (p = 0.83) of a drop below the average survival probability (approximately 0.91 in 1999; approximately 0.94, on average). As such, our mark-recapture approach enabled us to make useful inference about local dynamics within an open population of bottlenose dolphins; this should be applicable to other studies challenged by sampling highly mobile individuals with heterogeneous space use.