Soins maternels chez l'ours brun scandinave dans un contexte de chasse intensive

Les soins parentaux (principalement maternels) permettent d’améliorer la valeur adaptative des jeunes, mais ils sont coûteux pour les parents. La durée de la période de soins maternels présente toutefois une grande variabilité inter et intraspécifique, ce qui suggère qu’elle peut être ajustée. Comme la durée des soins maternels peut influencer les taux de reproduction individuels et populationnels, identifier les causes de la variation dans ce trait est pertinent d’un point de vue évolutif, écologique et démographique. L’objectif de cette thèse était d’étudier les soins maternels chez l’ours brun (Ursus arctos) et les causes de la variation dans leur durée. Cet objectif a été réalisé en se basant sur les données issues du suivi à long-terme (>30 ans) de l’ours brun en Suède, où la durée des soins maternels est variable (1,5 ou 2,5 ans) et le contexte de forte pression de chasse entraîne de nombreux effets indirects (p. ex. changements comportementaux) sur la population. Premièrement, mes résultats montrent que les soins maternels ne seraient pas distribués de façon homogène entre les jeunes d’une même portée puisque seuls les plus petits oursons avaient une masse réduite dans les grandes portées. Les femelles transféreraient ainsi le coût de la reproduction à certains de leurs oursons et maintiendraient un investissement stable dans les plus gros oursons, selon une tactique de reproduction conservatrice. Deuxièmement, mes résultats montrent que les déterminants de la durée des soins maternels étaient contexte-dépendants. En effet, à l’échelle de la Suède, la durée des soins maternels était causée directement par la taille de portée, la masse et l’âge de la mère, mais pas par la masse des jeunes. Toutefois, la durée des soins maternels n’était affectée directement que par la masse des jeunes dans le nord et par l’âge de la mère dans le sud. La différence s’expliquerait par les différentes pressions environnementales, dont la rudesse du climat et l’intensité de la chasse réglementée, sévissant dans les deux populations. Troisièmement, mes résultats montrent que les femelles fournissant de longs soins maternels (c.-à-d. 2,5 ans) avaient des comportements d’évitement des mâles, notamment en sélectionnant la proximité aux habitations humaines, durant la période de reproduction. Les mâles peuvent forcer la séparation de groupes familiaux, forcer le retour en œstrus des femelles et ainsi devenir, plus rapidement, les géniteurs de la prochaine portée. L’évitement des mâles durant la période à haut risque pourrait être une tactique maternelle pour minimiser les risques de rencontres agressives avec des mâles qui pourraient se solder par un sevrage hâtif et ainsi continuer les soins maternels. Quatrièmement, mes résultats montrent que la réglementation de la chasse interdisant de tuer des membres de groupes familiaux procurait artificiellement un bénéfice en survie aux femelles prodiguant des soins maternels longs. La réglementation de la chasse sélectionnerait ainsi artificiellement pour de plus longs soins maternels dans la population. De façon générale, mes recherches apportent une importante contribution à notre compréhension jusqu’alors très limitée des déterminants de la durée des soins maternels. Ma thèse souligne aussi l’importance de considérer le contexte environnemental dans l’évaluation des tactiques de reproduction maternelles

De la naissance au sevrage : influence des conditions environnementales et des caractéristiques individuelles chez le phoque commun (Phoca vitulina) du St-Laurent

Chez les mammifères, la date de naissance et les soins maternels peuvent moduler les chances de survie de la progéniture. Cette étude visait à évaluer l’impact des facteurs environnementaux (e.g. climat, océanographie, disponibilité des ressources alimentaires) et individuels (e.g. sexe de la progéniture) sur la phénologie des naissances, la croissance pré-sevrage et l’apport alimentaire lacté des chiots phoque commun du Saint-Laurent. Une méta-analyse sur 7 cohortes a révélé un impact positif de la température de l’eau à l’hiver sur les dates de mise-bas et une corrélation positive entre le succès d’élevage et l’abondance de hareng. L’étude montre différents patrons d’utilisation de l’espace pour l’allaitement et des soins maternels biaisés en faveur des mâles que nous expliquons par leur dépense énergétique et leur sollicitation supérieures aux femelles. Ce mémoire montre la sensibilité du phoque commun aux changements environnementaux et l’importance des considérations comportementales dans l’établissement du bilan énergétique des chiots allaités.In mammals, birth date and maternal care can affect offspring survival probabilities. This project aimed to assess the impact of environmental (e.g. climate, oceanography and food availability) and individual (e.g. offspring sex) factors on birth phenology, pre-weaning growth and milk intake in the St. Lawrence harbour seal. A meta-analysis on 7 cohorts revealed a positive impact of water temperature during winter on birth dates and a positive correlation between rearing success and herring abundance. This study revealed different patterns of space utilisation for nursing and biased maternal cares towards males that we explain by their greater energy expenditure and solicitation compared to females. This study shows the harbour seal sensitivity to environmental change and the importance of behavioural considerations when assessing the energy budget of pups during lactation

Stomach temperature records reveal nursing behaviour and transition to solid food consumption in an unweaned mammal, the harbour seal pup (Phoca vitulina)

Knowledge of milk transfer from mother to offspring and early solid food ingestions in mammals allows for a greater understanding of the factors affecting transition to nutritional independence and pre-weaning growth and survival. Yet studies monitoring suckling behaviour have often relied on visual observations, which might not accurately represent milk intake. We assessed the use of stomach temperature telemetry to monitor suckling and foraging behaviour in free-ranging harbour seal (Phoca vitulina) pups during lactation. Stomach temperature declines were analysed using principal component and cluster analyses, as well as trials using simulated stomachs resulting in a precise classification of stomach temperature drops into milk, seawater and solid food ingestions. Seawater and solid food ingestions represented on average 15.361.6% [0-40.0%] and 0.760.2% [0-13.0%], respectively, of individual ingestions. Overall, 63.7% of milk ingestions occurred while the pups were in the water, of which 13.9% were preceded by seawater ingestion. The average time between subsequent ingestions was significantly less for seawater than for milk ingestions. These results suggest that seawater ingestion might represent collateral ingestion during aquatic suckling attempts. Alternatively, as solid food ingestions (n = 19) were observed among 7 pups, seawater ingestion could result from missed prey capture attempts. This study shows that some harbour seals start ingesting prey while still being nursed, indicating that weaning occurs more gradually than previously thought in this species. Stomach temperature telemetry represents a promising method to study suckling behaviour in wild mammals and transition to nutritional independence in various endotherm species

The interplay between hunting rate, hunting selectivity, and reproductive strategies shapes population dynamics of a large carnivore

© The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in van de Walle, J., Pelletier, F., Zedrosser, A., Swenson, J. E., Jenouvrier, S., & Bischof, R. The interplay between hunting rate, hunting selectivity, and reproductive strategies shapes population dynamics of a large carnivore. Evolutionary Applications, (2021): 1-19, https://doi.org/10.1111/eva.13253.Harvest, through its intensity and regulation, often results in selection on female reproductive traits. Changes in female traits can have demographic consequences, as they are fundamental in shaping population dynamics. It is thus imperative to understand and quantify the demographic consequences of changes in female reproductive traits to better understand and anticipate population trajectories under different harvest intensities and regulations. Here, using a dynamic, frequency-dependent, population model of the intensively hunted brown bear (Ursus arctos) population in Sweden, we quantify and compare population responses to changes in four reproductive traits susceptible to harvest-induced selection: litter size, weaning age, age at first reproduction, and annual probability to reproduce. We did so for different hunting quotas and under four possible hunting regulations: (i) no individuals are protected, (ii) mothers but not dependent offspring are protected, (iii) mothers and dependent offspring of the year (cubs) are protected, and (iv) entire family groups are protected (i.e., mothers and dependent offspring of any age). We found that population growth rate declines sharply with increasing hunting quotas. Increases in litter size and the probability to reproduce have the greatest potential to affect population growth rate. Population growth rate increases the most when mothers are protected. Adding protection on offspring (of any age), however, reduces the availability of bears for hunting, which feeds back to increase hunting pressure on the nonprotected categories of individuals, leading to reduced population growth. Finally, we found that changes in reproductive traits can dampen population declines at very high hunting quotas, but only when protecting mothers. Our results illustrate that changes in female reproductive traits may have context-dependent consequences for demography. Thus, to predict population consequences of harvest-induced selection in wild populations, it is critical to integrate both hunting intensity and regulation, especially if hunting selectivity targets female reproductive strategies.JVdW and FP were funded by the Natural Sciences and Engineering Research Council of Canada. JVdW was also funded by the Fonds de Recherche du Québec—Nature et Technologies. This is scientific paper number 305 from the Scandinavian Brown Bear Research Project, which is funded by the Swedish Environmental Protection Agency, the Norwegian Directorate for Nature Management, and the Austrian Science Fund. This research was funded through the 2015-2016 BiodivERsA COFUND, with the national funders ANR (ANR-16-EBI3-0003), NCN (2016/22/Z/NZ8/00121), DLR-PT (01LC1614A), UEFISCDI (BiodivERsA3-2015-147-BearConnect (96/2016), and RCN (269863 and 286886). SJ acknowledges support of NSF OPP #1840058

Can hunting data be used to estimate unbiased population parameters? A case study on brown bears

Quantifying temporal changes in harvested populations is critical for applied and fundamental research. Unbiased data are required to detect true changes in phenotypic distribution or population size. Because of the difficulty of collecting detailed individual data from wild populations, data from hunting records are often used. Hunting records, however, may not represent a random sample of a population. We aimed to detect and quantify potential bias in hunting records. We compared data from a long-term monitoring project with hunting records of brown bears ( Ursus arctos ) in Sweden and investigated temporal trends (1996–2013) in the ratio of yearlings to adult females, yearling mass and adult female mass. Data from hunting records underestimated the decline in yearling and adult female mass over time, most likely owing to the legal protection of family groups from hunting, but reflected changes in the ratio of yearlings to adult females more reliably. Although hunting data can be reliable to approximate population abundance in some circumstances, hunting data can represent a biased sample of a population and should be used with caution in management and conservation decisions

Proximity to humans is associated with longer maternal care in brown bears

In the sexual conflict over the duration of maternal care, male mammals may improve their reproductive success by forcing early mother–offspring separation in species where lactation supresses estrus. However, when individual females benefit from continuing to care for their current offspring, they should adopt counter-strategies to avoid separation from offspring. Here, we tested whether spatial segregation from adult males and proximity to humans during the mating season could be associated with longer maternal care in the Scandinavian brown bear (Ursus arctos). Using resource selection functions (RSFs), we contrasted habitat selection patterns of adult males and those of adult females with yearlings that either provided 1.5 years of maternal care (“short-care females”) or continued care for an additional year (“long-care females”) during the mating season, the period when family break-ups typically occur. Males and short-care females had similar habitat selection patterns during the mating season. In contrast, habitat selection patterns differed between males and long-care females, suggesting spatial segregation between the two groups. In particular, long-care females used areas closer to human habitations compared with random locations (defined here as selection), whereas males used areas further to human habitations compared with random locations (defined here as avoidance). Our results show a correlation between habitat selection behavior and the duration of maternal care. We suggest that proximity to humans during the mating season may represent a female tactic to avoid adverse interactions with males that may lead to early weaning of offspring

The impact of boldness on demographic rates and life-history outcomes in the wandering albatross.

Differences among individuals within a population are ubiquitous. Those differences are known to affect the entire life cycle with important consequences for all demographic rates and outcomes. One source of among-individual phenotypic variation that has received little attention from a demographic perspective is animal personality, which is defined as consistent and heritable behavioural differences between individuals. While many studies have shown that individual variation in individual personality can generate individual differences in survival and reproductive rates, the impact of personality on all demographic rates and outcomes remains to be assessed empirically. Here, we used a unique, long-term, dataset coupling demography and personality of wandering albatross (Diomedea exulans) in the Crozet Archipelago and a comprehensive analysis based on a suite of approaches (capture-mark-recapture statistical models, Markov chains models and structured matrix population models). We assessed the effect of boldness on annual demographic rates (survival, breeding probability, breeding success), life-history outcomes (life expectancy, lifetime reproductive outcome, occupancy times), and an integrative demographic outcome (population growth rate). We found that boldness had little impact on female demographic rates, but was very likely associated with lower breeding probabilities in males. By integrating the effects of boldness over the entire life cycle, we found that bolder males had slightly lower lifetime reproductive success compared to shyer males. Indeed, bolder males spent a greater proportion of their lifetime as non-breeders, which suggests longer inter-breeding intervals due to higher reproductive allocation. Our results reveal that the link between boldness and demography is more complex than anticipated by the pace-of-life literature and highlight the importance of considering the entire life cycle with a comprehensive approach when assessing the role of personality on individual performance and demography

Offspring mass variation in tree swallows : a case of bet‐hedging?

The evolution of reproductive strategies is affected by the ability of organisms to deal with future environmental conditions. When environments are temporally unpredictable, however, it is difficult to anticipate optimal offspring phenotype. Diversification of offspring phenotypes, a strategy called diversified bet‐hedging, may allow parents to maximize their fitness by reducing between‐year variation in reproductive success. The link between diversification of offspring phenotypes and individual reproductive success, however, has rarely been documented empirically. We used an eight‐year dataset (1215 broods, 870 females) on individually marked tree swallows ( Tachycineta bicolor ) to assess whether intra‐brood mass variation was compatible with a diversified bet‐hedging strategy. Intra‐brood mass variation was weakly, but significantly repeatable within females, suggesting consistent individual differences. Greater intra‐brood mass variation, however, was not associated with reduced between‐year variation in reproductive success or increased female reproductive success. Moreover, contrary to diversified bet‐hedging expectations, fledging success of large broods was greater when hatchlings had similar rather than variable masses. Our results suggest that intra‐brood mass variation may not result from diversified bet‐hedging, but rather from complex interactions between environmental, brood, and maternal characteristics

Indirect effects of bear hunting : a review from Scandinavia

Harvest by means of hunting is a commonly used tool in large carnivore management. To evaluate the effects of harvest on populations, managers usually focus on numerical or immediate direct demographic effects of harvest mortality on a population's size and growth. However, we suggest that managers should also give consideration to indirect and potential evolutionary effects of hunting (e.g., the consequences of a change in the age, sex, and social structure), and their effects on population growth rate. We define “indirect effects” as hunting-induced changes in a population, including human-induced selection, that result in an additive change to the population growth rate “lambda” beyond that due to the initial offtake from direct mortality. We considered 4 major sources of possible indirect effects from hunting of bears: (1) changes to a population's age and sex structure, (2) changes to a population's social structure, (3) changes in individual behavior, and (4) human-induced selection. We identified empirically supported, as well as expected, indirect effects of hunting based primarily on >30 years of research on the Scandinavian brown bear (Ursus arctos) population. We stress that some indirect effects have been documented (e.g., habitat use and daily activity patterns of bears change when hunting seasons start, and changes in male social structure induce sexually selected infanticide and reduce population growth). Other effects may be more difficult to document and quantify in wild bear populations (e.g., how a younger age structure in males may lead to decreased offspring survival). We suggest that managers of bear and other large carnivore populations adopt a precautionary approach and assume that indirect effects do exist, have a potential impact on population structure, and, ultimately, may have an effect on population growth that differs from that predicted by harvest models based on direct effects alone