Viabilitat demogràfica i efecte dels canvis ambientals antropogènics en la distribució, dieta i condició física d'una població d'aufrany Neophron percnopterus en expansió = Demographic viability and effect of anthropogenic environmental changes in the distribution, diet and body condition of an expanding population of Egyptian Vulture Neophron percnopterus

[cat] En la present tesi s’avaluen les causes del creixement demogràfic de la població d’aufrany (Neophron percnopterus) a Catalunya, així com també s’estudia la influència dels canvis ambientals antropogènics, en especial dels abocadors, sobre la dieta, la condició física i la presència de contaminants dels individus de la població. En primer lloc, es du a terme un anàlisi demogràfic de l’aufrany a l’àrea d’estudi per a veure quins són els principals factors que han causat el seu augment poblacional. Els resultats, demostren que la població d’aufrany ha augmentat d’1 a 22 parelles entre els anys 1988 i 2012 i, que per explicar el creixement observat, ha estat necessària una elevada supervivència dels individus adults així com l’arribada d’individus d’altres àrees. A banda, s’estudia l’expansió poblacional de l’espècie per tal de veure quines són les característiques ambientals de les noves àrees de colonització, avaluant concretament la influència dels recursos alimentaris d’origen antròpic, definits amb el nom de Predictable Anthropogenic Food Subisdes (PAFS). Els resultats apunten que els PAFS tenen un paper important en la selecció territorial de l’aufrany, ja que els territoris de cria estan situats més a prop dels abocadors del que s’esperaria a l’atzar. Tot i així, altres factors ambientals com les zones rocoses orientades al sud, la urbanització i la proximitat a conespecífics també tenen importància en la selecció dels territoris. A més, per tal d’avaluar quin és l’ús que les parelles d’aufrany fan dels abocadors s’analitza la dieta dels polls de la població. Per a fer-ho, es comparen dues metodologies, l’anàlisi d’isòtops estables i l’anàlisi de restes convencional. Els resultats obtinguts amb els dos mètodes coincideixen en que el consum de restes d’abocador pot arribar a ser elevat en algunes parelles (al voltant d’un 50 %). Un cop coneguda la dieta dels individus, la següent qüestió que s’aborda és quina influència té el fet d’alimentar-se en abocadors sobre la seva condició física. Els resultats indiquen que la proporció de la dieta que prové d’abocadors és el factor principal que afecta els indicadors fisiològics dels individus. Els polls alimentats a partir de residus humans presenten nivells més baixos d’algunes vitamines i carotens, els quals tenen funcions importants com a defenses antioxidants, propietats immunoestimulants i finalitats ornamentals. A més a més, els polls alimentats en abocadors, semblen estar més ben alimentats i experimentar menys períodes de dejú que els individus que no utilitzen aquests recursos. Finalment, s’analitzen les concentracions de diferents famílies de contaminants; metalls, compostos organoclorats (Ocs), èters difenílics polibromats (PBDEs) i substàncies perfluorades (PFAS) en els individus de la població així com la seva influència en la fisiologia dels individus. La major part dels nivells detectats de contaminants es troben per sota el límit de detecció o són, en general, baixos. Així, tot i que l’acumulació de contaminants en polls d’aufrany a l’àrea d’estudi no sembla estar causant greus efectes negatius sobre la seva fisiologia, si que es detecta que els individus de les zones més humanitzades, presenten uns nivells de PFAS més elevats. Aquesta tesi aporta informació rellevant en dos sentits. En primer lloc, perquè descriu el cas particular de l’augment demogràfic d’una espècie amenaçada que es troba en declivi a gran part de la seva distribució mundial; el coneixement de les causes que han provocat aquesta tendència positiva, podria ser molt útil per a la conservació de l’aufrany en d’altres àrees on està disminuint. En segon lloc, perquè s’avalua quines són les implicacions d’alimentar-se en abocadors. En un món antropitzat on els escenaris de la distribució dels recursos estan canviant constantment, aportar coneixement sobre la influència dels abocadors pot ser clau per a dissenyar mesures de gestió futures de les espècies amenaçades o plaga que utilitzen aquests punts.[eng] The Egyptian Vulture (Neophron percnopterus) is an endangered scavenger species that in recent years has experienced a population growth and an expansion of its range in Catalonia (NE of Iberian Peninsula). In this thesis the demographic and environmental factors that could have caused this increase are studied. Population models showed that, to explain the observed population growth, it has been needed a high adult survival and the arrival of immigrants from other populations. Also, it was assessed the influence of predictable anthropogenic food subsides, specifically landfills, to the distribution, diet and body condition of individuals of our study population. First, it was observed that occupied territories were located closer landfills than expected by chance, so the location of these installations are determining the distribution of breeding pairs. After, it was assessed the contribution of food from landfills to Egyptian Vulture diet using both conventional analyses and stable isotope analysis. Results showed that that both methods provide similar contributions of food from landfills in this species’ overall diet, and also a high proportion of food derived from landfills (nearly 50%) was detected in some breeding pairs. The next step was to determine the influence of diet from landfills to the body condition of nestlings, using morphometrical and physiological approaches. It was found that the contribution of landfills to the diet was the main factor that explained body condition of individuals, especially for its effect to the antioxidant metabolism. Also, nestlings that fed in landfills seem to be better fed. Finally, concentrations of different families of Persistent Organic Pollutants and metals were analysed in nestlings of our population and it was found that levels of pollutants were in general low, so they not appear as susceptible to cause detrimental effects to nestlings’ physiology. Overall, this thesis contributes to the knowledge of conservation status of Egyptian Vulture in Catalonia and it can be useful to assess the influence of landfills to vulture species

Assessing the applicability of stable isotope analysis to determine the contribution of landfills to vultures' diet

Human activities cause changes to occur in the environment that affect resource availability for wildlife. The increase in the human population of cities has led to a rise in the amount of waste deposited in landfills, installations that have become a new food resource for both pest and threatened species such as vultures. In this study we used stable isotope analysis(SIA)and conventional identification of food remains from Egyptian Vultures (Neophron percnopterus) to assess the applicability of SIA as a new tool for determining the composition of the diets of vultures, a group of avian scavengers that is threatened worldwide. We focused on an expanding Egyptian Vulture population in NE Iberian Peninsula to determine the part played by landfills and livestock in the diet of these species, and aimed to reduce the biases associated with conventional ways of identifying food remains. We compared proportions of diet composition obtained with isotope mixing models and conventional analysis for five main prey. The greatest agreement between the two methods was in the categories `landfills' and `birds' and the greatest differences between the results from the two methods were in the categories `livestock', `carnivores' and `wild herbivores'. Despite uncertainty associated to SIA, our results showed that stable isotope analysis can help to distinguish between animals that rely on waste and so present enriched levels of δ 13C than those that feed on the countryside. Indeed, a high proportion of food derived from landfills (nearly 50%) was detected in some breeding pairs. Furthermore we performed GLMM analyses that showed that high values of δ 13C in Egyptian Vulture feathers (a proxy of feeding in landfills) are related with high levels of humanization of territories. This method has the potential to be applied to other threatened vulture species for which there is a lack of information regarding resources they are consuming, being especially important as the main causes of vultures decline worldwide are related to the consumption and availability of food resources

Assessing the applicability of stable isotope analysis to determine the contribution of landfills to vultures' diet

Human activities cause changes to occur in the environment that affect resource availability for wildlife. The increase in the human population of cities has led to a rise in the amount of waste deposited in landfills, installations that have become a new food resource for both pest and threatened species such as vultures. In this study we used stable isotope analysis(SIA)and conventional identification of food remains from Egyptian Vultures (Neophron percnopterus) to assess the applicability of SIA as a new tool for determining the composition of the diets of vultures, a group of avian scavengers that is threatened worldwide. We focused on an expanding Egyptian Vulture population in NE Iberian Peninsula to determine the part played by landfills and livestock in the diet of these species, and aimed to reduce the biases associated with conventional ways of identifying food remains. We compared proportions of diet composition obtained with isotope mixing models and conventional analysis for five main prey. The greatest agreement between the two methods was in the categories `landfills' and `birds' and the greatest differences between the results from the two methods were in the categories `livestock', `carnivores' and `wild herbivores'. Despite uncertainty associated to SIA, our results showed that stable isotope analysis can help to distinguish between animals that rely on waste and so present enriched levels of δ 13C than those that feed on the countryside. Indeed, a high proportion of food derived from landfills (nearly 50%) was detected in some breeding pairs. Furthermore we performed GLMM analyses that showed that high values of δ 13C in Egyptian Vulture feathers (a proxy of feeding in landfills) are related with high levels of humanization of territories. This method has the potential to be applied to other threatened vulture species for which there is a lack of information regarding resources they are consuming, being especially important as the main causes of vultures decline worldwide are related to the consumption and availability of food resources

Assessing the applicability of stable isotope analysis to determine the contribution of landfills to vultures’ diet

<div><p>Human activities cause changes to occur in the environment that affect resource availability for wildlife. The increase in the human population of cities has led to a rise in the amount of waste deposited in landfills, installations that have become a new food resource for both pest and threatened species such as vultures. In this study we used stable isotope analysis (SIA) and conventional identification of food remains from Egyptian Vultures (<i>Neophron percnopterus</i>) to assess the applicability of SIA as a new tool for determining the composition of the diets of vultures, a group of avian scavengers that is threatened worldwide. We focused on an expanding Egyptian Vulture population in NE Iberian Peninsula to determine the part played by landfills and livestock in the diet of these species, and aimed to reduce the biases associated with conventional ways of identifying food remains. We compared proportions of diet composition obtained with isotope mixing models and conventional analysis for five main prey. The greatest agreement between the two methods was in the categories ‘landfills’ and ‘birds’ and the greatest differences between the results from the two methods were in the categories ‘livestock’, ‘carnivores’ and ‘wild herbivores’. Despite uncertainty associated to SIA, our results showed that stable isotope analysis can help to distinguish between animals that rely on waste and so present enriched levels of δ ¹³C than those that feed on the countryside. Indeed, a high proportion of food derived from landfills (nearly 50%) was detected in some breeding pairs. Furthermore we performed GLMM analyses that showed that high values of δ ¹³C in Egyptian Vulture feathers (a proxy of feeding in landfills) are related with high levels of humanization of territories. This method has the potential to be applied to other threatened vulture species for which there is a lack of information regarding resources they are consuming, being especially important as the main causes of vultures decline worldwide are related to the consumption and availability of food resources.</p></div

Percentage of the contribution of landfills in the diet of Egyptian Vulture nestlings estimated with Bayesian mixing models (SIMMR).

<p>Data of each territorial pair but different year is represented with the same number. Boxes represent the credible interval of 50% and error bars the credible interval of 95% obtained with SIMMR.</p

Isotopic values (δ ¹³C and δ ¹⁵N) of Egyptian Vulture nestlings in Catalonia (n = 60) and main sources of food (mean ± SD).

<p>Same symbols correspond to the isotopic values of nestlings from the same territory but different years.</p

Proportion of diet of Egyptian Vulture represented by main prey categories obtained by stable isotope analysis and conventional identification of food remains.

<p>Medians, quartiles and outliers of each prey category are represented in the boxplot.</p

Isotopic values of each source of food considered in the Bayesian isotopic mixing models.

<p>Isotopic values of each source of food considered in the Bayesian isotopic mixing models.</p

Distribution of breeding pairs (yellow circles) and landfills (green symbols) located inside our study area and considered for diet analysis.

<p>Grey gradient represent altitudes from 0 m (white) to 3000 m (black). Two important cities are also represented.</p

Results of comparison of conventional methods and isotope analysis for the diet of Egyptian Vulture in Catalonia during the period 2012–2014.

<p>(a) Probability of difference below 0 between stable isotope analysis and conventional analysis for main prey of Egyptian Vulture. (b) Mean differences between stable isotope analysis and conventional methods in estimates of the main prey of Egyptian Vulture. Standard errors of the differences are represented.</p