Pathogenic fungi are increasingly associated with epidemics in wildlife populations and represent a significant threat to global biodiversity. Snake fungal disease is an emerging disease caused by the fungus, Ophidiomyces ophiodiicola, and appears to be widespread in the eastern United States. Yet an evaluation of field diagnostics, and an understanding of the population-level consequences of the disease, are lacking. First, I evaluated the use of clinical signs to predict the presence of O. ophiodiicola across season and snake habitat affiliation (aquatic or terrestrial) and I compared two sampling methods to see if collection method impacts PCR result. Overall, snakes with clinical signs had a higher probability of testing positive regardless of season or habitat association. However, terrestrial snakes had a lower overall probability of testing positive for O. ophiodiicola compared to aquatic snakes. I found no significant difference between sampling methods. Second, I used Passive Integrated Transponder (PIT) telemetry, and multistate capture-mark-recapture modelling to determine if SFD affects the short-term survival, movement, and behavior of wild snakes. I found no difference in short-term survival for snakes with SFD. Snakes with SFD spend more time surface-active and have lower permanent emigration and temporary immigration rates than snakes without SFD.

Carcharias taurus is listed as Critically Endangered along the east coast of Australia and there is concern about their status globally. The use of traditional tag–recapture methods to monitor the east coast C. taurus population have been discontinued due to tag–biofouling and injuries that relate to tag attachment. In the current study, captive and wild C. taurus were used to assess whether spots present on their flanks were suitable natural tags for individual shark recognition. Photographic images of seven captive sharks taken at monthly intervals for 13 months and at three years after the start of the study indicated that their spot number, position and relative size did not change over this period. Similarly, eighty–nine wild sharks photographically re–identified at least 23 months after their initial identification (and in one case after 14 years) confirmed long–term spot–pattern retention. Photographic recaptures of individual C. taurus provided information about their temporal and spatial distribution and movement patterns along the Australian east coast in relation to maturity, sex and reproductive condition. A total of 930 sharks were photo–identified between 2004 and 2008 at 23 aggregation sites between Wolf Rock and Montague Island. Of these, 479 were females (271 mature, 208 immature) and 452 were males (288 mature, 60 sub–adults, 104 juveniles). The distribution of pregnant C. taurus was seasonally and temporally distinct from all other sharks. Visibly pregnant C. taurus were recorded at Wolf Rock (the most northern site) from February until October, although many sharks left during July. Pregnant C. taurus were also observed at North Moreton Island, Flat Rock and Fish Rock between June and November. Resting (mature, non–gravid) females and mature males were mostly observed at mid–southern sites from December to June, with northern counts increasing from June to November. The majority of immature sharks were recorded at mid–southern sites. Of 930 sharks identified between 2004 and 2008, 149 were identified at more than one site. On average, mature females moved 338 km (SD ± 465), mature males 340 km (SD ± 299), immature females 147 km (SD ± 98), sub–adult males 185 km (SD ± 216), and juvenile males 271 km (SD ± 237). The maximum rate of movement per day was 18.5 km for a mature female shark, 20.7 km for a mature male, 4.3 km for an immature female, 86 km for a sub–adult male and 4 km for a juvenile male. Mature males and mature non–pregnant females tended to move north from mid–winter and mate in late spring/early summer in warmer waters. From about mid–winter, pregnant females began to move from the warmer waters of their gestation areas to cooler southern waters to pup (probably from late spring to mid–summer). The movement patterns of immature sharks varied temporally, and were more limited spatially. Underwater censuses, photo–identification and acoustic tracking of individual C. taurus were used to investigate their reproductive periodicity, localised movements and behavioural segregation at Wolf Rock – the most northerly aggregation site on the east Australian seaboard. A biennial reproductive cycle was indicated for 18 of 28 females for which re–identifications spanned at least two mating and/or pregnancy events. Nine of the 28 sharks appeared to exhibit a triennial reproductive cycle. Male C. taurus were observed between July and January, but were absent between February and April. Scuba divers reported seeing some mating scars on individuals from mid–October, however fresh mating scars were predominately observed on photographs of individual C. taurus taken in November and December. Four acoustically–tagged mature female sharks remained within 500 m of the Wolf Rock aggregation site within a marine sanctuary zone for 78 – 90 % of the 11–15 day study period. A minimum population estimate of 930 individuals is provided from all sharks identified between 2004 and 2008. In addition, a Jolly–Seber (open model design) mark–recapture analysis on data obtained during four scheduled photo–identification surveys (conducted between July 2006 and February 2008 at 25 aggregation sites along the east coast of Australia) was used to estimate the size of this population. A maximum of 272 sharks (143 females and 129 males) were identified during any scheduled survey period. Model averaging across the highest rated JS models (Popan data formulation) resulted in an estimate of 756 males (95% CI = 590 – 922) and 1185 females (95% CI = 901 – 1469). The mark–recapture abundance estimate is considered preliminary and requires further model development to incorporate the heterogeneity in distribution and migration patterns within the C. taurus population. The occurrence of retained fishing gear and gear–related jaw injuries were quantified from the four scheduled photo–identification surveys along the east coast of Australia. A total of 673 sharks were identified with 119 occurrences of retained fishing gear or jaw injury recorded from 113 individual sharks. For sharks that were known by spot–patterns on both flanks, 29 % of females and 52 % of males were seen with retained fishing gear or a gear–related jaw injury. The largest numbers of identified sharks (222) during the surveys were seen at Fish Rock (off the New South Wales coast): 48 % of all sharks identified with retained fishing gear were first identified at this site. Fish Rock is a designated critical habitat for C. taurus, but most forms of line fishing, except fishing while anchored or moored with bait and/or wire trace line are permitted. Results from the surveys clearly demonstrated that C. taurus is susceptible to a large variety of fishing gear and fishing methods. Current protection measures for C. taurus appear insufficient at this site, particularly as large aggregations that include immature and mature sharks occur consistently throughout the year.

Background: Parasite evolution is hypothesized to select for levels of parasite virulence that maximise transmission success. When host population densities fluctuate, low levels of virulence with limited impact on the host are expected, as this should increase the likelihood of surviving periods of low host density. We examined the effects of Morogoro arenavirus on the survival and recapture probability of multimammate mice (Mastomys natalensis) using a seven-year capture-mark-recapture time series. Mastomys natalensis is the natural host of Morogoro virus and is known for its strong seasonal density fluctuations. Results: Antibody presence was negatively correlated with survival probability (effect size: 5-8% per month depending on season) but positively with recapture probability (effect size: 8%). Conclusions: The small negative correlation between host survival probability and antibody presence suggests that either the virus has a negative effect on host condition, or that hosts with lower survival probability are more likely to obtain Morogoro virus infection, for example due to particular behavioural or immunological traits. The latter hypothesis is supported by the positive correlation between antibody status and recapture probability which suggests that risky behaviour might increase the probability of becoming infected.

The topic of badgers in the UK is often a contentious one, dividing opinions and sparking political debate. On one hand, badgers represent an important part of the British ecosystem but on the other a wildlife reservoir of disease implicated in the transmission of bovine tuberculosis (TB) to livestock in the UK. This has prompted strong interest in their population dynamics and epidemiology. Using data from a long-term study of a naturally infected badger population in Woodchester Park, Gloucestershire, this thesis explores a range of capture-mark-recapture (CMR) models to further understand disease and demographic processes. The first section examines long term population dynamics, simultaneously estimating demographic rates alongside their drivers using integrated population models (IPMs). The findings provide new insight into badger demography, highlighting density-dependent mechanisms, vulnerabilities to changing climate and disease prevalence and subsequently how multi-factorial analyses are required to explain fluctuating badger populations. The following sections use multistate models to answer pertinent questions regarding individual disease dynamics, revealing rates of TB infection, progression and disease-induced mortality. A key finding was sex-differences in disease response, with males more susceptible to TB infection. After applying a survival trajectory analysis we suggest sex differences are due to male immune defence deficiencies. A comparative analysis demonstrated similarities between epidemiological processes at Woodchester Park to an unconnected population of badgers from a vaccine study, supporting its continued use as a model population. The final study in this thesis constructs an IPM to estimate disease and population dynamics and in doing so uncovers disease-state recruitment allocation rates, demographic and population estimates of badgers in varying health-states and predicts future dynamics. This model aims to encapsulate the more commonly held notion of populations as dynamic entities with numerous co-occurring processes, opening up avenues for future analyses within both the badger-TB system and possible extensions to other wildlife reservoir populations.

Infectious diseases are increasingly being recognised as significant threatening processes in conservation biology. Developing strategies to effectively manage infectious diseases in wildlife is, therefore, of the utmost importance to the maintenance of global biodiversity. The effective management of infectious diseases relies on understanding the ecology of the host, the epidemiological characteristics of the pathogen and the impacts of the pathogen on the host population. However, for most wildlife-disease systems this information remains poorly understood. This is particularly true for endangered species threatened by novel infectious agents as opportunities to observe and assess disease impacts and host-pathogen dynamics in the wild are limited. The Tasmanian devil (Sarcophilus harrisii), the world’s largest carnivorous marsupial, is threatened with extinction as a result of an epidemic of an emerging disease, a fatal infectious cancer known as Devil Facial Tumour Disease (DFTD). In this thesis I capitalised on a unique dataset from a population of Tasmanian devils where disease arrived part-way through an intensive longitudinal study, and utilised existing genetic samples collected prior to DFTD outbreak, to determine the impact of DFTD on the demography, population dynamics, genetic diversity and population genetic structure of wild Tasmanian devils. I then used this knowledge of the impacts of DFTD impacts in an unmanaged population to evaluate the effectiveness of a disease management trial involving the selective culling of infected individuals. I employed mark-recapture models to investigate the impact of DFTD on age-specific and sex-specific apparent survival rates, to examine the pattern of variation in infection rates (force of infection), and to investigate the impact of DFTD on population growth rate. I investigated demography, life-history traits and morphometric parameters of infected and uninfected individuals to determine the impacts of DFTD on age-structure and sex-structure, female fecundity and individual growth rates. I used this information to assess the population’s ability to respond to low population densities and to compensate for the detrimental impacts of DFTD. To determine the genetic consequences of disease-induced population decline I used microsatellite DNA to compare genetic diversity, population genetic structure and dispersal patterns in three Tasmanian devil populations prior to and following DFTD outbreaks. Capture-mark-recapture analyses revealed that the arrival of DFTD triggered an immediate decline in apparent survival rates of devils, the rate of which was predicted well by the increase in disease prevalence in the population over time. Transition rates of healthy individuals to the diseased class (the force of infection) increased in relation to disease prevalence, while the arrival of DFTD coincided with a marked and ongoing decline in the population growth rate. There was a significant change to the age structure following the arrival of DFTD. This shift to a younger population was caused by the loss of older individuals as a direct consequence of DFTD-driven declines in adult survival rates. Evidence of reproductive compensation in response to these disease impacts was observed via a reduction in the age of sexual maturity of females over time. However, widespread precocial breeding in devils was precluded by physiological and ecological constraints that limited the ability of one year olds to breed. Using temporally-replicated spatial genetic data, I found evidence of increased inbreeding following DFTD arrival and greater population genetic differentiation in post-disease populations. These changes appeared to be driven by a combination of selection and altered dispersal patterns of females in DFTD-affected populations. Comparison of demographic and epidemiological parameters indicative of disease progression and impact between the managed and unmanaged populations revealed that selective culling of infected individuals neither slowed the rate of disease progression nor reduced the population level impacts of this debilitating disease; with culling mortality simply compensating for disease mortality. This thesis provides one of the few direct empirical evaluations of the impact of an emerging wildlife disease epidemic on a wild population. This thesis revealed that infectious diseases can result in major demographic and genetic changes in host populations over relatively few generations and short time-scales. Results showing dramatic and ongoing population declines and very limited population compensation in DFTD-affected populations indicate that DFTD poses a significant extinction risk for wild devil populations. Hence, this study confirms that host-specific pathogens can pose a significant extinction risk for wild species, even in the absence of alternate reservoir hosts, a finding critical to our understanding of host-pathogen dynamics. My thesis also highlights the potential negative interplay between disease susceptibility and host genetic variability, which is of utmost importance to the management of novel wildlife epizootics and the conservation of threatened wildlife in general. The thorough understanding of the ecology and impacts of DFTD in the wild obtained in this study has provided a solid base from which to both rigorously assess the outcome of management strategies and also formulate recommendations for the management of this disease in the wild. The lack of evidence for successful control of the DFTD epidemic in a wild population during the first phase of a selective culling experimental adaptive management approach, points to the need to implement a multi-faceted disease management program when attempting to control a novel infectious disease in the wild. By drawing on the lessons learnt in this case study I show that it is possible to establish a set of general guidelines for the future management of infectious diseases in threatened wildlife.

Le fuligule milouin (Aythya ferina) est une espèce de canard plongeur répandue dans l’ensemble du Paléarctique. Montrant des signes de déclin de ses effectifs nicheurs en Europe depuis les années 2000, son statut de conservation IUCN a été réévalué de « Préoccupation Mineure » à « Vulnérable ». Etant une espèce chassée, la question du maintien de ces prélèvements cynégétiques est légitime. L’objectif de ce travail de thèse est donc de comprendre son fonctionnement démographique et les mécanismes sous-jacents à sa dynamique de population, pour proposer des mesures de gestion et de conservation. Pour cela, nous nous sommes attachés à estimer la tendance de ce déclin sur sa voie de migration nord-ouest européenne à partir des données de recensements de la mi-janvier. Puis, nous avons étudié la connectivité migratoire de cette voie de migration avec les autres voies préssuposées, afin de mieux comprendre l’origine de ce déclin. Enfin, nous avons estimé deux paramètres démographiques clés, la survie et le succès de nidification, pour les intégrer dans un cadre matriciel permettant d’estimer un taux de croissance asymptotique et comprendre quels sont les paramètres démographiques clés sur lesquels doivent reposer les actions de gestion. Il ressort de ce travail de thèse que le déclin du fuligule milouin est probalement dû surtout à une diminution de sa productivité en Europe de l’Est et en Russie. Le contrôle et la gestion de la productivité par l’Homme étant limités, uniquement des travaux de gestion autour des habitats liés à la nidification sont envisageables. Ces travaux pourraient être facilement menés en Europe mais beaucoup plus difficilement en Sibérie, principale aire de reproduction des milouins caractérisée par une vaste superficie et un fort isolement. Les taux de survie des oiseaux bagués en France sont plus faibles que pour les oiseaux bagués dans d’autres pays, potentiellement du fait d’une pression de chasse plus élevée. Amener le taux de survie en France au même niveau que dans les pays voisins (Suisse et Grande-Bretagne), par une modification de la réglementation sur la chasse, serait de nature à ramener le taux de croissance à l’équilibre. La mise en place de la gestion adaptative pourrait faciliter les objectifs de conservation fixés en adaptant annuellement ces prélèvements aux effectifs présents et aux connaissances dont on dispose. / The Common Pochard (Aythya ferina) is a regular diving duck species in the western Palearctic. However, a worrisome decline of its wintering population led to an up-listed IUCN status from “Least Concern” to “Vulnerable”. This species is still hunted in Europe despite this decline. Hence, one may wonder about the sustainability of its harvest. The aim of this work was to understand the population dynamics of this species, and the drivers of these mechanisms. For this purpose, we assessed the declining trend in northwestern Europe using the mid-january censuses. Then, we studied the migratory connectivity with the two others flyways, in order to better understand the origin of the decline. Finally, we assessed two main demographic parameters (survival rate and nesting success) and combined these into a matrix population model. This model allowed us to assess an asymptotic growth rate and to determine the key demographic parameters on which management actions should focus. The main results of this thesis indicate that the decrease in productivty in Europe and in Russia could have been the main reason of the decline. However, given the limited human action to improve Pochard productivity, only breeding habitat improvement could be considered. Such improvements could be easily considered in Europe, but not in Siberia, the main breeding region characterized by a large area and a strong geographic isolation. Survival rates were lower in France than in neighbouring countries, possibly owing to a greater hunting pressure. A more moderate hunting pressure could lead to higher survival rates, and a balanced growth rate. Setting up an adaptative harvest management scheme could help reaching defined management goals, by annually adapting hunting quotas to current knowledge and assessment of Pochard population size.

Prior to European settlement, black bear (Ursus americanus) were far less abundant in the state of California. Estimates from statewide harvest data indicate the California black bear population has tripled in the last 3 decades. Bears inhabit areas they formally never occurred (e.g., urban environments) and populations that were at historically low densities are now at high densities. Though harvest data are useful and widely used as an index for black bear population size and population demographics statewide, it lacks the ability to produce precise estimates of abundance and density at local scales or account for the numerous bears living in non-hunted areas. As the human population continues to expand into wildlife habitat, we are being forced to confront controversial issues about wildlife management and conservation. Habituated bears living in non-hunted, urban areas have been and continue to be a major concern for wildlife managers and the general public. My objective was to develop DNA-based capture-mark-recapture (CMR) survey techniques in wildland and urban environments in Mono County, California to acquire population size and density at local scales from 2010 to 2012. I also compared population density between the urban and wildland environment. To my knowledge, DNA-based CMR surveys for bears have only been implemented in wildland or rural environments. I made numerous modifications to the techniques used during wildland DNA-based CMR surveys to survey bears in an urban environment. I used a higher density of hair-snares than typically used in wildland studies, non-consumable lures, modified hair-snares for public safety, included the public throughout the entire process, and surveyed in the urban-wildland interface as well as the city center. These methods were efficient and accurate while maintaining human safety. I determined that there is likely a difference in population density between the urban and wildland environments. Population density was 1.6 to 2.5 times higher in the urban study area compared to the wildland study area. Considering the negative impacts urban environments can have on wildland bear populations, this is a serious management concern. The densities I found were similar to those found in other urban and wildland black bear populations. The baseline data acquired from this study can be used as part of a long-term monitoring effort. By surveying additional years, population vital rates such as apparent survival, recruitment, movement, and finite rate of population change can be estimated.

The evolution of extra-group paternity (EGP) is a contentious issue in evolutionary biology. This thesis examines the factors and adaptive benefits driving EGP in a high-density, group-living population of European badgers (Meles meles). To improve power to assign parentage, I isolated and characterised 21 new polymorphic microsatellite markers. I genotyped 83% of 1410 badger trapped 1987‒2010 using 35 autosomal microsatellite markers. Maternity and paternity were assigned at 80% confidence ca. 82% of individuals. 48% of paternities were extra-group, where 85% were attributable to neighbouring-group males and EGP was detected in 47% of litters; thus badger social group do not correspond with a breeding unit. I tested whether indirect genetic benefits explain these high EGP rates. (1) ‘Good-gene-as-heterozygosity Hypothesis’: Paternal heterozygosity, but not maternal or an individual’s own heterozygosity, associated positively with first-year survival probability. Under benign environmental conditions, cubs fathered by more heterozygous males had a higher first year survival probability. Despite this correlation, the EGP rate per litter correlated with neither average nor maximum within-group heterozygosity of candidate fathers. (2) Fitness benefit Hypothesis: Extra-group offspring (EGO) had lower first-year survival probability and lived 1.3 years less than within-group offspring (WGO). Female WGO produced more litters and offspring over their lifetime than female EGO, whereas male EGO produced more offspring than male WGO. (3) Inbreeding avoidance hypothesis: The EGP rate within a litter increased with greater average pair-wise relatedness between mothers and within-group candidate fathers. No inbreeding depression on first-year survival probability was detected, but small sample sizes limited statistical power. Socio-ecologically, at the litter level, EGP correlated negatively with the number of within-group candidate fathers, and positively with neighbouring-group candidate fathers. In conclusion, EGP in badgers may reduce inbreeding and be maintained in the population through a sex-specific antagonistic selection and indirect genetic benefits may occur when the total fitness benefits of producing extra-group sons outweigh the costs of producing extra-group daughters. These indirect genetic benefits only partially explain the evolution of promiscuity in European badgers, highlighting that evolutionary factors underlying promiscuity remain unclear.

New analytical and technological tools have the potential to yield unprecedented insights into the life histories of migratory species. I used Bayesian population models and Global Positioning System-acceleration tracking devices to understand the demographic mechanism and likely drivers underpinning the Greenland White-fronted Goose (Anser albifrons flavirostris) population decline. I used a 27-year capture-mark-recapture dataset from the main wintering site for these birds (Wexford, Ireland) to construct multistate models that estimated age- and sex-specific survival and movement probabilities and found no sex-bias in emigration or ‘remigration’ rates (chapter 2). These formed the foundation for an integrated population model, which included population size and productivity data to assess source-sink dynamics through estimation of age-, site-, and year-specific survival and movement probabilities, the results of which suggest that Wexford is a large sink and that a reduction in productivity (measured as recruitment rate) is the proximate demographic mechanism behind the population decline (chapter 3). Low productivity may be due to environmental conditions on breeding areas in west Greenland, whereby birds bred at youngest ages when conditions were favourable during adulthood and the breeding year (chapter 4), and possibly mediated by links with the social system, as birds remained with parents into adulthood, forfeiting immediate reproductive success, although a cost-benefit model showed the ‘leave’ strategy was marginally favoured over the ‘stay’ strategy at all ages (chapter 5). Foraging during spring does not appear to limit breeding, as breeding and non-breeding birds did not differ in their proportion of time feeding or energy expenditure (chapter 6). Two successful breeding birds were the only tagged individuals (of 15) to even attempt to nest, suggesting low breeding propensity has contributed to low productivity. Although birds wintering in Ireland migrated further to breeding areas than those wintering in Scotland, there were no differences in feeding between groups during spring migration (chapter 7). These findings suggest that Greenland White-fronted Geese are not limited until arrival on breeding areas and the increasingly poor environmental conditions there (chapter 8). More broadly, these findings demonstrate the application of novel tools to diagnose the cause of population decline.

Chez les espèces longévives, une relation inverse entre la variabilité des paramètres démographiques et leur élasticité (i.e. la contribution relative du paramètre au taux de croissance de la population) semble exister. La théorie de la canalisation environnementale permet d'expliquer une telle relation. Les paramètres ayant la plus haute élasticité auraient évolué de façon à être moins variable face aux variations environnementales afin d'optimiser la fitness individuelle et ainsi maximiser la croissance de la population. Afin de tester l'existence d'une telle hypothèse chez une espèce, il est nécessaire d'estimer les paramètres démographiques ainsi que leur contribution relative au taux de croissance. À l'aide des modèles les plus récents de capture-marquage-recapture, nous avons donc estimé les paramètres de survie juvénile et de reproduction chez la grande oie des neiges pour les comparer au taux de survie adulte, paramètre le plus élastique.Notre étude a montré que les paramètres de survie juvéniles et de probabilité de nicher étaient très variables, tel qu'attendu. Le taux de survie juvénile dépend des conditions environnementales, avec notamment un fort effet du parasitisme. En vermifugeant des individus, nous avons trouvé un effet négatif des parasites intestinaux sur la survie des oies juvéniles femelles mais pas sur celle des mâles, ce qui s'explique probablement par une différence d'investissement dans le système immunitaire en fonction du sexe chez les individus en croissance. La probabilité de nicher est également dépendante des conditions environnementales mais notre étude a également révélé l'existence de coûts associés à la reproduction. En effet, la probabilité de nicher l'année suivante était fortement réduite suite à une reproduction avec succès comparé aux individus qui avaient eu un échec. Par contre, parmi les individus qui nichent, ceux qui avaient du succès l'année précédente avaient plus de chance d'avoir à nouveau du succès l'année suivante que ceux qui avaient eu un échec, ce qui suggère une hétérogénéité dans la qualité des individus. En parallèle de ces estimations, nous avons montré que le taux de survie adulte était constant au cours du temps et indépendante du statut reproducteur l'année précédente. Finalement, nous avons également trouvé que la survie adulte ne différait pas entre 2 colonies situés à 800 km de distance dans l'Arctique canadien, ce qui suggère une absence de variabilité spatiale pour ce paramètre démographique. Notre étude a donc démontré la faible variabilité temporelle et spatiale du paramètre démographique le plus important pour le taux de croissance de la population, contrairement aux autres paramètres qui montrent une forte variabilité chez la grande oie des neiges. Notre étude permet donc d'appuyer la théorie de la canalisation environnementale des paramètres démographiques chez les espèces longévives. / In long-lived species, an inverse relationship apparently occurs between variability of demographic parameters and their elasticity (i.e. the relative contribution of a given parameter to the population growth rate). The environmental canalization theory has been proposed to explain such a relationship. Demographic parameters with the highest elasticity should have evolved in a way reducing their variability in presence of environmental variations in order to optimize individual fitness and hence to maximize the population growth rate.To test this hypothesis in a given species, demographic parameters and their elasticity need to be accurately estimated. Using advanced capture-mark-recapture models, we estimated juvenile survival and breeding probabilities in the greater snow goose and we compared their variability to adult survival, the parameter with the highest elasticity.Our study showed that both juvenile survival rate and breeding propensity were highly variable, as expected. The juvenile survival probability varied upon environmental conditions, with a strong impact of parasitism. An anthelmintic drug treatment applied to juveniles revealed a negative effect of intestinal parasites on survival of juvenile females but not males, which could be explained by a sex-differential investment in the immune system in growing individuals. We found that the breeding propensity also varied with environmental conditions but we also found some evidence for costs of reproduction. Breeding propensity in the following year was greatly reduced after a successful reproduction compared to birds that had a failed attempt. However, among birds that bred, those that had a success the year before were more likely to be successful again the following year than those that had failed, which suggests heterogeneity in individual quality. In those studies, we showed that adult survival was constant over time and independent of the breeding status the year before. Finally, we also found that adult survival did not differ between 2 breeding colonies distant of 800 km in the Canadian Arctic, which suggests an absence of spatial variability for this demographic parameter.We thus demonstrated a low temporal and spatial variability in the most important demographic parameter for population growth, which contrasts with the high variability of other parameters in the greater snow goose. Our study supports the environmental canalization theory as applied to demographic parameters in long-lived species.