François Sarrazin

How Predictability of Feeding Patches Affects Home Range and Foraging Habitat Selection in Avian Social Scavengers

Feeding stations are commonly used to sustain conservation programs of scavengers but their impact on behaviour is still debated. They increase the temporal and spatial predictability of food resources while scavengers have supposedly evolved to search for unpredictable resources. In the Grands Causses (France), a reintroduced population of Griffon vultures Gyps fulvus can find carcasses at three types of sites: 1. “light feeding stations”, where farmers can drop carcasses at their farm (spatially predictable), 2. “heavy feeding stations”, where carcasses from nearby farms are concentrated (spatially and temporally predictable) and 3. open grasslands, where resources are randomly distributed (unpredictable). The impact of feeding stations on vulture’s foraging behaviour was investigated using 28 GPS-tracked vultures. The average home range size was maximal in spring (1272±752 km2) and minimal in winter (473±237 km2) and was highly variable among individuals. Analyses of home range characteristics and feeding habitat selection via compositional analysis showed that feeding stations were always preferred compared to the rest of the habitat where vultures can find unpredictable resources. Feeding stations were particularly used when resources were scarce (summer) or when flight conditions were poor (winter), limiting long-ranging movements. However, when flight conditions were optimal, home ranges also encompassed large areas of grassland where vultures could find unpredictable resources, suggesting that vultures did not lose their natural ability to forage on unpredictable resources, even when feeding stations were available. However during seasons when food abundance and flight conditions were not limited, vultures seemed to favour light over heavy feeding stations, probably because of the reduced intraspecific competition and a pattern closer to the natural dispersion of resources in the landscape. Light feeding stations are interesting tools for managing food resources, but don’t prevent vultures to feed at other places with possibly high risk of intoxication (poison).

Estimating effects of adult male mortality on grizzly bear population growth and persistence using matrix models

We radio monitored a hunted, sexually segregated grizzly bear (Ursus arctos) population and an unhunted, unsegregated population for demographics and constructed a stage- and age-classified matrix model to test for the effects of adult male mortality and resulting sexual segregation on population growth and persistence. Population parameters in the model were adult female survival, subadult female survival, offspring survival, probability of litter sizes, and probability of unsuccessful pregnancy. The last three parameters were affected by adult male mortality and segregation, the others were not. We compared population growth with and without effects of hunting by holding adult female and subadult female survival constant and by using hunted and unhunted values for offspring survival, litter size, and pregnancy. Population growth (Lambda) showed the greatest elasticity for adult survival, subadult survival, offspring survival, litter size, and unsuccessful pregnancy, in that order. This corresponds with observed anti-infanticide tactics (sexual segregation) by adult females to maximize their fitness. The hunted population decreased at a rate of 0.99 whereas the simulated, unhunted population increased at a rate of 1.05. The hunted population was much more susceptible to population extinction. Under demographic stochasticity mean time to extinction was 32 years in the hunted population and 110 years in the unhunted population. Under environmental stochasicity mean time to extinction was 21 years in the hunted population and 43 years in the unhunted population. We suggest that sexual segregation caused by hunting resident adult males can result in population decline and can even contribute to rapid population extinctions when numbers are small.

Roles of survival and dispersal in reintroduction success of Griffon vulture (Gyps fulvus).

The success of reintroduction programs greatly depends on the amount of mortality and dispersal of the released individuals. Although local environmental pressures are likely to play an important role in these processes, they have rarely been investigated because of the lack of spatial replicates of reintroduction. In the present study, we analyzed a 25-year data set encompassing 272 individuals released in five reintroduction programs of Griffon Vultures (Gyps fulvus) in France to examine the respective roles of survival and dispersal in program successes and failures. We use recent developments in multi-strata capture-recapture models to take into account tag loss in survival estimates and to consider and estimate dispersal among release areas. We also examined the effects of sex, age, time, area, and release status on survival, and we tested whether dispersal patterns among release areas were consistent with habitat selection theories. Results indicated that the survival of released adults was reduced during the first year after release, with no difference between sexes. Taking into account local observations only, we found that early survival rates varied across sites. However when we distinguished dispersal from mortality, early survival rates became equal across release sites. It thus appears that among reintroduction programs difference in failure and success was due to differential dispersal among release sites. We revealed asymmetrical patterns of dispersal due to conspecific attraction: dispersers selected the closest and the largest population. We showed that mortality can be homogeneous from one program to another while, on the contrary, dispersal is highly dependent on the matrix of established populations. Dispersal behavior is thus of major interest for metapopulation restoration and should be taken into account in planning reintroduction designs.

How cheap is soaring flight in raptors? A preliminary investigation in freely-flying vultures.

Measuring the costs of soaring, gliding and flapping flight in raptors is challenging, but essential for understanding their ecology. Among raptors, vultures are scavengers that have evolved highly efficient soaring-gliding flight techniques to minimize energy costs to find unpredictable food resources. Using electrocardiogram, GPS and accelerometer bio-loggers, we report the heart rate (HR) of captive griffon vultures (Gyps fulvus and G. himalayensis) trained for freely-flying. HR increased three-fold at take-off (characterized by prolonged flapping flight) and landing (>300 beats-per-minute, (bpm)) compared to baseline levels (80–100 bpm). However, within 10 minutes after the initial flapping phase, HR in soaring/gliding flight dropped to values similar to baseline levels, i.e. slightly lower than theoretically expected. However, the extremely rapid decrease in HR was unexpected, when compared with other marine gliders, such as albatrosses. Weather conditions influenced flight performance and HR was noticeably higher during cloudy compared to sunny conditions when prolonged soaring flight is made easier by thermal ascending air currents. Soaring as a cheap locomotory mode is a crucial adaptation for vultures who spend so long on the wing for wide-ranging movements to find food.

Integration of demography and genetics in population restorations

Abstract By definition, restoration projects involve small populations, which are subject to demographic, genetic, and environmental stochasticities. Besides its fundamental interest for ecology, the integration of these stochastic factors in population viability models is required to make such models more realistic. In this paper, we report previous attempts to integrate population dynamics and population genetics, two disciplines that are generally treated as separate fields. We then evaluate their potential interactions in the context of population restoration. In the first part, we investigate the interactions among stochastic factors of extinction and various species characteristics, such as growth rate, generation length, and mating system. In the second part, we discuss how demographic and genetic models can be used to compare the relative efficiencies of different reintroduction and reinforcement strategies in different environments. For that purpose, we examine spatial and temporal aspects of release, as well as the number and type of individuals to release. In many cases, these comparisons uncover opposite effects among the genetic and demographic factors that antagonistically influence short- and long-term viabilities. Choosing an appropriate restoration strategy should therefore involve the integration of different disciplines in population viability analyses.

Genetic variation in a network of natural and reintroduced populations of Griffon vulture (Gyps fulvus) in Europe

It is generally considered that limiting the loss of genetic diversity in reintroduced populations is essential to optimize the chances of success of population restoration. Indeed, to counter founder effect in a reintroduced population we should maximize the genetic variability within the founding group but also take into account networks of natural populations in the choice of the reintroduction area. However, assessment of relevant reintroduction strategies requires long-term post-release genetic monitoring. In this study, we analyzed genetic data from a network of native and reintroduced Griffon vulture (Gyps fulvus) populations successfully restored in Southern Europe. Using microsatellite markers, we characterized the level of genetic diversity and degree of genetic structure within and among three native colonies, four captive founding groups and one long-term monitored reintroduced population. We also used Bayesian assignment analysis to examine recent genetic connections between the reintroduced population and the other populations. We aimed to assess the level of fragmentation among native populations, the effectiveness of random choice of founders to retain genetic variability of the species, the loss of genetic diversity in the reintroduced population and the effect of gene flow on this founder effect. Our results indicate that genetic diversity was similar in all populations but we detected signs of recent isolation for one native population. The reintroduced population showed a high immigration rate that limited loss of genetic diversity. Genetic investigations performed in native populations and post-released genetic monitoring have direct implications for founder choice and release design.

Evolution in the Anthropocene

Taking account of the evolutionary effects of human actions is crucial for humans and nonhumans Most current conservation strategies focus on the immediate social, cultural, and economic values of ecological diversity, functions, and services (1). For example, the Intergovernmental Platform on Biodiversity and Ecosystem Services (2) mostly addresses the utilitarian management of biodiversity from local to global scales. However, besides urgent diagnosis and actions (3, 4), processes that occur over evolutionary time scales are equally important for biodiversity conservation. Strategizing for conservation of nature at such long time scales will help to preserve the function—and associated services—of the natural world, as well as providing opportunities for it to evolve. This approach will foster a long-term, sustainable interaction that promotes both the persistence of nature and the wellbeing of humans.

Post-Release Dispersal in Animal Translocations: Social Attraction and the “Vacuum Effect”

Animal translocations are human-induced colonizations that can represent opportunities to contribute to the knowledge on the behavioral and demographic processes involved in the establishment of animal populations. Habitat selection behaviors, such as social cueing, have strong implications on dispersal and affect the establishment success of translocations. Using modeling simulations with a two-population network model (a translocated population and a remnant population), we investigated the consequences of four habitat selection strategies on post-translocation establishment probabilities in short- and long-lived species. Two dispersal strategies using social cues (conspecific attraction and habitat copying) were compared to random and quality-based strategies. We measured the sensitivity of local extinctions to dispersal strategies, life cycles, release frequencies, remnant population and release group sizes, the proportion of breeders and the connectivity between populations. Our results indicate that social behaviors can compromise establishment as a result of post-release dispersal, particularly in long-lived species. This behavioral mechanism, the “vacuum effect”, arises from increased emigration in populations that are small relative to neighboring populations, reducing their rate of population growth. The vacuum effect can drive small remnant populations to extinction when a translocated group is large. In addition, the magnitude of the vacuum effect varies non-linearly with connectivity. The vacuum effect represents a novel form of the behaviorally mediated Allee effect that can cause unexpected establishment failures or population extinctions in response to social cueing. Accounting for establishment probabilities as a conditional step to the persistence of populations would improve the accuracy of predicting the fates of translocated or natural (meta)populations.

Intra-specific competition in foraging Griffon Vultures Gyps fulvus: 2. The influence of supplementary feeding management

Capsule Young vultures have better access to food resources at supplementary feeding sites where carcasses are fewer and less predictable, and placed further from colonies. Aims To investigate the impact of the management of supplementary feeding sites on foraging and feeding behaviour in Griffon Vultures Gyps fulvus. Methods With focal and scan sampling we studied whether group size, group composition and foraging behaviour differed between collective ‘heavy’ feeding sites (sites close to colonies, supplied regularly with many carcasses) and individual ‘light’ feeding sites (sites further from colonies, supplied irregularly with few carcasses). Results Total group size was proportional to food mass deposited and did not differ between sites in summer. At heavy feeding sites adults arrived sooner than young, so they had better access to viscera of high energy content, while young individuals could only eat later on the scraps. However, at light feeding sites young vultures arrived earlier and in larger proportions. Intra-specific competition was strong and adults were generally dominant over younger birds. Conclusions Young birds foraged preferentially at light feeding sites where the competition was lower, allowing a better access to high-quality food. Favouring light feeding sites is an adequate solution for managing vulture populations in areas in which sanitary laws permit carcasses to be placed at feeding sites.

Does sex matter in reintroduction of griffon vultures Gyps fulvus

M. Bose´, P. Le Gouar, C. Arthur, J. Lambourdie`re, J.P. Choisy, S. Henriquet, P. Lecuyer, M. Richard,C. Tessier and F. SarrazinAbstract In small populations of monogamous speciessex ratio bias and sex-skewed demographic traits couldlead to higher extinction probabilities than in othermating systems. Therefore a knowledge of bias in sexratio, mortality and movement would be useful todetermine the optimal strategy for sampling foundersprior to reintroduction. We used molecular sexing to sexwild-hatched cohorts of two colonies (one native andone reintroduced) and four released groups of griffonvultures Gyps fulvus in France. In wild-hatched cohortsthe sex ratio was not different from equilibrium what-ever the year. Similarly no bias was detected in the sexratio of founding stocks. Recoveries, recaptures, move-ments and philopatry were not skewed according tosex in wild-hatched and released groups. Our studyrevealed that no sex bias occurred during the griffonvulture life cycle (i.e. birth, death and movement).Consequently, random sampling may be appropriate toconstitute founding stock in reintroduction programmesfor monomorphic vultures.Keywords Founding stock, France, griffon vulture,Gyps fulvus, molecular sexing, mortality, reintroduction,sex ratio.IntroductionThe proportion of males and females, i.e. sex ratio, is animportant factor of success for a newly foundedpopulation (Sarrazin & Legendre, 2000). According toFisher’s (1930) and Trivers’ (1972) theories on sexualselection, equilibrated sex ratio at birth is expected inmonogamous species (Cockburn et al., 2002) but differ-ential pressures on sexes could occur and lead toskewed mortality or dispersal (Gowaty, 1993; Bradshawet al., 2003). Sex ratio among sexually mature individualsis often male biased for monogamous species (Bessa-Gomes et al., 2004). Moreover, for monogamous species,stochastic fluctuations of sex ratio in a small populationcould lead to higher extinction probability than in othermating systems (Legendre et al., 1999) and could affecteffective population size by increasing reproductivevariance among individuals (Anthony & Blumstein,2000). Biased sex-ratio may also cause an Allee effect,mostly because of limited mate finding (Stephens S Engen et al., 2003).Therefore, the optimal sex ratio among sexuallymature individuals required to maximize reintroductionsuccess with monogamous species is 1:1 because thisratio will maximize population growth rate (Legendre,2004). For example, re-establishment of the monoga-mous white tailed sea eagle Haliaeetus albicilla inScotland was slow because chance differences in thenumbers of males and females led to a significantnumber of individuals failing to form pairs (Greenet al., 1996). Unequivocal identification of the sex ofindividuals appears essential in reintroduction projects(Griffiths & Tiwari, 1995; IUCN, 1998) but, when select-ing founders, sex may be uncertain for young of mostspecies and also for adults of monomorphic species. Insuch cases the strategy usually adopted is to collectindividuals randomly from wild populations, hopingfor a balanced sex ratio in the founding group. However,this strategy implies that sex ratio at birth and indemographic traits such as mortality and dispersal isnot skewed.