Dissertations / Theses on the topic 'Competitive feeding'

Cattle are social animals and frequently interact with other members of their social group, especially when access to food is limited. Despite considerable interest in the social behavior of cattle, no research has focused on assessing the relationship between competition and the feeding behavior of individual feedlot cattle housed in small groups. Forty-five British crossbred feedlot heifers (520.5 ± 32 kg BW) were used to determine how successful competitive interactions impacted an individual's ability to consume and gain access to feed in a competitive feeding environment. Heifers were randomly assigned to 3 pens of 15 animals. Pens were fitted with two radio frequency equipped feed tubs that monitored individual dry matter intake and bunk attendance duration. Cattle were fed a total mixed ration once daily consisting of barley silage, concentrate and mineral supplement at 0900, 1200 and 1500 and had ad libitum access to both feed and water. All competitive interactions at and around the feed tubs were monitored continuously from 0900 to 2200 on three separate days. Animals were considered successful if they either gained access to feed, or if they were already eating, they maintained their position. There was a positive relationship between the number of successful interactions displayed and dry matter intake (R² = 0.26, P = 0.0003), bunk attendance duration, (R² 0.45, P < 0.0001) and bunk attendance frequency (R² = 0.49, P < 0.0001). The strength of these relationships varied dramatically throughout the day and was strongest in the first hour after feed delivery between 0900 and 1000. Large variation between individuals suggests that different animals develop individual feeding strategies in competitive environments. Animals used competition, varied eating rate, and shifted feeding times to access feed. Although this study suggests that the success of an animal in competitive interactions at the feedbunk plays a role in its ability to access and consume feed, individual behavioral differences also play a significant role.
Land and Food Systems, Faculty of
Graduate

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Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico
Recently, capuchin monkeys (Cebus spp.) inhabitants of dry environments and with restriction of fleshy fruits, have been the subject of several studies regarding the use of instruments. During behaviour of using stones to crack open nuts there is evidence of selection of more effective hammers, as well as selection of anvils related to reducing the risk of predation. The aim of this study was to determine whether two groups of capuchin monkeys (C.flavius and and C.libidinosus) inhabitants of the Caatinga of Rio Grande do Norte make choice of hammers and anvils. The record of weight and location of stones indicated active choices of with what (choice of hammers) and where (selection of anvils) to crack open encapsulated seeds. The choice of hammers to break nuts depended on the type and degree of ripeness seed. Thus, smaller seeds were smashed with lighter hammers and larger seeds with heavier hammers. Still, C. flavius was the only species that presented a refinement in the choice of hammers that depended on the ripeness of seeds. For both species of capuchin monkeys studied, the nut-crack sites were not spread in accordance with the spatial distribution of seed-producing species, suggesting that the capuchin monkeys promote active choice of anvils. Thus, in environments with more escape routes through the trees, the nut-crack sites were found further apart than in regions that had less chance of escape through the trees. Also, there was a difference in the spacing of the anvils to depend on the type of seed: sites used to crack larger and more caloric seeds were found farther apart than the sites used to crack smaller and less caloric seeds, suggesting a pattern of avoiding direct competition. We conclude that the capuchin monkeys maximize energy savings and reduced risk of predation and the costs of food competition during the behaviour of using stones to crack open nuts
Recentemente, macacos prego (Cebus spp.) habitantes de ambientes secos e com restri??o de frutos carnosos, v?m sendo alvo de diversos estudos acerca do uso de instrumentos. Em atividades de quebra de sementes, h? ind?cios de escolhas eficientes de martelos, bem como de sele??o de bigornas para redu??o dos riscos de preda??o. O objetivo deste trabalho foi verificar se dois grupos de macacos prego (C. flavius e C. libidinosus) habitantes da caatinga do Rio Grande do Norte realizam escolhas de martelos e bigornas. O registro do peso e da localiza??o das pedras indicou escolhas ativas de com o que (escolha de martelos) e onde (sele??o de bigornas) quebrar sementes encapsuladas. O padr?o de escolha dos martelos para quebrar sementes dependeu da esp?cie e do estado de matura??o. Assim, sementes menores foram quebradas com martelos mais leves e sementes maiores com martelos mais pesados. Ainda, C. flavius foi a ?nica esp?cie que apresentou um refinamento na escolha de martelos que dependia do estado de matura??o de sementes. Para ambas as esp?cies de macacos prego estudadas, os s?tios de quebra n?o estavam dispostos de acordo com a distribui??o espacial das esp?cies produtoras de sementes, sugerindo que os macacos prego promovem escolha ativas de bigornas. Assim, em ambientes que havia maior chance de fuga atrav?s das ?rvores, os s?tios de quebra foram encontrados mais afastados entre si do que em regi?es que havia menor chance de fuga pelas ?rvores. Tamb?m, foi verificada diferen?a no espa?amento das bigornas a depender do tipo de semente: s?tios de quebra de sementes maiores e mais cal?ricas foram encontrados mais distantes entre si do que os s?tios de quebra de sementes menores e menos cal?ricas, sugerindo um padr?o de evitac?o de competi??o direta. Conclu?mos que os macacos prego maximizam os ganhos energ?ticos e reduziram os riscos de preda??o bem como os custos de competi??o por alimento durante o comportamento de uso de pedras para quebra de sementes

Since 2000, there has been a marked decline in the number of harbour seals in some regions around Britain; one possible contributing cause is competition for prey with sympatric grey seals. To explore one important aspect of this interaction, in this thesis the diet of harbour seals is estimated using analysis of hard prey remains recovered from faeces and compared with equivalent results for grey seals. To estimate coefficients to account for partial and complete digestion of hard prey remains, 100 whole prey feeding trials were conducted with six harbour seals and 18 prey species. Differences were found among prey species and between harbour and grey seals highlighting the importance of applying predator- and prey-specific digestion correction factors when reconstructing diet. In a comprehensive exploration of the diet of harbour seals around Britain, sandeel and flatfish dominated in the North Sea and large gadoids dominated on the Scottish west coast with seasonal pulses of pelagic prey. Variation in diet was linked to regional and seasonal differences in prey distribution and abundance. Sex-specific variation in harbour seal diet was examined in four regions. The main difference detected was in The Wash, where female diet quality was significantly higher than males in winter, which appeared to be driven by greater consumption of pelagic prey by female seals associated with seasonal energetic requirements of their annual life cycle. Comparison of the diet of harbour and grey seals revealed regional differences in diet composition, diversity and quality between the two species. However, there was no consistent pattern in this variation in relation to regional variation in harbour and grey seals population trajectories and no clear evidence for interspecific competition for prey. Future work should focus on an integrated investigation of prey abundance and distribution, and seal diet and foraging behaviour/distribution.

Laboratory experiments examined now aggressive behavior, use of space, activity and breathing frequency were affected by the number of fish competing for a concentrated, renewing, intermittent food source. Total aggression rate per fish and the proportion of long chases decreased in larger groups and increased during short periods in which food was unavailable. The proportional use of the area near the food source was maximal at intermediate group sizes suggesting that use of the feeding area was reduced by aggressive defense at low densities and by passive interference at high densities. Air-breathing frequency tended to be lower when food was available than when it was not, suggesting that gouramis reduce their use of atmospheric oxygen when it may result in loss of food to competitors. Group size affects the pattern of food competition more through economic resource defense than through passive interference.

Transition dairy cows are vulnerable to negative consequences of depressed feed intake due to a transient state of negative energy balance that predisposes them to disease after calving. Competition has been identified as one factor that can decrease feeding activity in mid-lactation cows, but the effects of competition on the transition cow are less well understood. The objective of this study was to test the effect of a competition on the behaviour and feed intake of transition cows. Standing behaviour, feeding behaviour and dry matter intake (DMI) was monitored from 1 wk before to 2 wk after calving for 110 Holstein dairy cows. Social behaviour was recorded in the week before calving. Cows were assigned to a competitive (2:1 cows:bin) or non-competitive (1:1 cow:bin) treatment at the start of the study. Treatment groups were balanced for parity and baseline feeding data, resulting in 8 primiparous and 10 multiparous cows per treatment. Competition dramatically increased the number of agonistic behaviours between cows at the feeder. Primiparous cows showed no change in either feeding or standing behaviour when fed in a competitive environment; however, they increased their total meal duration and within-meal intervals in the wk -1 before and wk +1 after calving. In wk -1 before calving, competitively fed multiparous cows increased the frequency of visits to the feeder but consumed less feed at each visit, resulting in decreased daily DMI. Throughout the experiment, multiparous cows fed competitively spent less time eating at each visit and ate at a faster rate, particularly during the 2 wk after calving. Multiparous cows on the competitive treatment also increased the time they spent standing (without eating) compared to cows on the non-competitive treatment. Feeding rate was negatively correlated with social status in multiparous cows. In summary, the results of this study indicate that restricting access to the feeder increases agonistic behaviours regardless of parity, and cows of different parity and social status respond differently in terms of feeding and standing behaviour.

Parasiten können den Energietransfer in Lebensgemeinschaften über trophische Kaskaden beeinflussen, indem sie Änderungen in den Konsumenten-Ressourcen-Interaktionen induzieren. In der vorliegenden Arbeit wurde die Rolle von Trematoden auf das Freßverhalten ihrer Wirte auf zwei trophischen Ebenen untersucht. Vier verschiedene Süßwasserschnecken-Trematoden-Systeme wurden verwendet, um zu testen, ob ein allgemeines Muster für die Auswirkung von Infektionen auf die Grazingaktivität von Schnecken auf das Periphyton nachgewiesen werden kann. Die Grazingraten auf Periphyton bei infizierten Schnecken entweder höher, niedriger oder ähnlich denen derjenigen von nicht infizierten Artgenossen. Augenparasiten können die Leistungsfähigkeit ihres Wirtes beeinträchtigen, was die Auswirkungen auf das Erkennen von Beutetieren, Raubtieren und Artgenossen hat. Mit Tylodelphys clavata experimentell infizierte Flussbarsche wurden mit zwei verschiedenen Beutetierarten eingesetzt, um das Fraßverhalten in Konkurrenz mit nicht infizierten Artgenossen zu untersuchen. Die Entfernung, aus der infizierte Fische die beiden Beutetierarten attackierten, war im Vergleich zu nicht infizierten Artgenossen signifikant kürzer. Die Tendenz war, dass nicht infizierte Fische mehr von den verfügbaren Beutetieren verzehrten. Um zu prüfen, ob der Fisch als Kompensation seine Beutepräferenz verändert, wurde die Beutezusammensetzung von Flussbarschen aus dem Müggelsees mittels Mageninhalts- und Stabilisotopenanalysen untersucht. Beide Methoden ergaben, dass sich die Fische mit zunehmender Intensität der Infektion selektiver ernährten, während sich geringer infizierte Fische Generalisten herausstellten. Die Ergebnisse dieser Studie bestätigen, dass Trematoden eine wichtige Rolle in Nahrungsnetzen spielen können, indem sie das Freßverhalten ihres Wirtes verändern. Darüber hinaus können Trematoden so die Stärke der Interaktion ihrer Wirte mit anderen Arten auf verschiedenen trophischen Ebenen beeinflussen.
Parasites can influence energy transfer through communities via trophic cascades by inducing alterations on consumer-resource interactions. This study evaluated the role of trematodes on their host’s feeding behaviour at two trophic levels. Four different freshwater snail–trematode systems were used to test whether a general pattern can be detected for the impact of infections on snail periphyton grazing activity. Mass-specific periphyton grazing rates of infected snails were higher, lower, or similar to rates of non-infected conspecifics. The variation across systems may result from differences on how the parasites use the resources of the snail and thus affect its energy budget. Eye parasites can impair their host’s sensory performance with important consequences for the detection of prey, predators and conspecifics. European perch experimentally infected with Tylodelphys clavata were used to evaluate their feeding behaviour under competition with non-infected conspecifics, for two different prey species (Asellus aquaticus and Daphnia magna). The distance at which infected fish attacked both prey species was significantly shorter in comparison to non-infected conspecifics. Additionally, infected fish had more unsuccessful attacks and there was a general tendency that non-infected fish consumed more of the available prey. To evaluate whether fish alter their prey preference as a compensatory mechanism, perch from Lake Müggelsee were sampled and their diet was evaluated using both stomach content and stable isotope analyses. Both methods indicated that with increasing infection intensity fish had a more selective diet, while less intensively infected fish appeared to be generalist feeders. The results from this study confirm that trematodes can play a relevant role within food webs by altering their hosts’ feeding behaviour. Furthermore, in this way trematodes can affect the interaction strengths of their hosts with other species at various trophic levels.

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Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior - CAPES
Group living animals, like most primates, benefit from a reduction in predation risk and an improvement in their potential to compete for food with other groups. However, gregariousness also increases intragroup food competition that can modulate within-group agonism and interindividual spatial patterns. We evaluated the influence of fruit availability and consumption (degree of frugivory) on the agonistic behavior and interindividual distance in two populations of Gray woolly monkeys living in forest fragments in southwestern Brazilian Amazonia. We recorded 165 intragroup agonistic interactions in a feeding context via the ?all occurrences? method and 3,549 records of spacing via scan sampling. Fruit consumption presented a direct relationship with agonistic and spacing behavior, whereas our estimate of fruit availability was a good predictor only for spacing. Woolly monkey selection of food patches composed of trees with diameter at breast height almost fourfold than that of the trees found in the phenology plots might explain the lack of relationship between fruit availability and agonism. The proportion of time (50%) that woolly monkeys had no nearby (<5 m) neighbors is compatible with a strategy of reducing intragroup fruit competition by managing interindividual distances. In sum, we presented the first evidence of aggressive intragroup feeding competition in Lagothrix cana and demonstrate the influence of fruit availability and consumption on some aspects of the social system of woolly monkeys.
Animais que vivem em grupo, como a maioria dos primatas, s?o beneficiados por uma redu??o no risco de preda??o e um aumento na possibilidade de defesa cooperativa dos recursos. Por?m, a vida em sociedade aumenta a competi??o intragrupo por alimento, a qual pode modular as intera??es agon?sticas e o espa?amento interindividual. Avaliamos a influ?ncia da disponibilidade de frutos e seu consumo (grau de frugivoria) no comportamento agon?stico e espa?amento interindividual de duas popula??es de macacos-barrigudos em fragmentos florestais na Amaz?nia brasileira. Registramos 165 intera??es agon?sticas intragrupo no contexto de alimenta??o via m?todo de ?todas as ocorr?ncias? e 3549 registros de espa?amento via m?todo de ?varredura instant?nea?. O consumo de frutos apresentou uma rela??o direta com o comportamento agon?stico e o espa?amento interindividual, enquanto a disponibilidade de frutos foi um bom preditor apenas do espa?amento. A explora??o pelos barrigudos de locais de alimenta??o com ?rvores com di?metro ? altura do peito quase quatro vezes maior do que as ?rvores monitoradas para a an?lise da disponibilidade de frutos pode explicar a aus?ncia de rela??o com o agonismo. A propor??o do tempo (50%) na qual os barrigudos estiveram sem vizinhos pr?ximos (<5 m) ? compat?vel com uma estrat?gia de redu??o da competi??o intragrupo por frutos via manuten??o do distanciamento interindividual. Em suma, apresentamos as primeiras evid?ncias de competi??o agressiva intragrupo para Lagothrix cana e demonstramos a import?ncia da disponibilidade e consumo de frutos em moldar alguns aspectos do sistema social dos barrigudos.

Studies focusing syntopic species help to understand how they partition resources and coexist. The objective of this work was to describe the social system, habitat use and diet of the hoary fox (Pseudalopex vetulus) and the crab-eating fox (Cerdocyon thous), in an area of cattle farms in Central Brazil. It is also reported a confrontation between the two species, observed during a study on the behavioral repertory of the hoary fox. Social system and habitat use were studied by direct observation of foxes in the field and diet, through scat analysis. Crab-eating foxes were found in pairs in 34 (59%) of 58 encounters and hoary foxes were solitary in 58 (84.0%) of 69 encounters, with no seasonal variation in the group size of both species. During one encounter of a crab-eating fox couple, the male vocalized to call the female that had remained behind. Hoary foxes were sighted in grazed pasture in a higher proportion (84%) than crab-eating foxes (67%) and they were never found in forest neither in swamp. Besides, both species were rarely seen together, and the only encounter registered ended in a conflict, with the crab-eating fox driving the hoary fox out. Twenty-seven taxa were identified in the diet of the two canids, with the crab-eating fox (n = 32 scats) consumed fruits, insects (mainly Orthoptera and Coleoptera) and vertebrates (most Cricetidae and Squamata) and the hoary fox (n = 23 scats) ate primarily termites (Isoptera). Results indicate that crab-eating fox couples keep more tight bonds than hoary fox couples. The coexistence of both species may be related to the detected differences in habitat use and diet.
Estudos enfocando espécies sintópicas ajudam a entender como elas partilham os recursos e coexistem. O objetivo deste trabalho foi descrever o sistema social, o uso do habitat e a dieta da raposa-do-campo (Pseudalopex vetulus) e do cachorro-do-mato (Cerdocyon thous), em uma área de fazendas de gado no Brasil Central. Também é relatado um confronto entre as duas espécies observado durante um estudo sobre o repertório comportamental da raposa-do-campo. O sistema social e o uso de habitat foram estudados a partir da observação direta dos animais no campo e a dieta, através da análise de fezes. Os cachorros-do-mato foram encontrados em duplas em 34 (59%) de 58 encontros e as raposas-do-campo estavam solitárias em 58 (84%) de 69 encontros, não havendo variação sazonal no tamanho de grupo das duas espécies. Durante um dos encontros de uma dupla de cachorro-do-mato, o macho vocalizou para chamar a fêmea que havia ficado para trás. As raposas-do-campo foram avistadas em pastagens em uma proporção maior (84%) que os cachorros-do-mato (67%) e nunca foram encontradas em florestas ou brejos. Além disso, as duas espécies raramente foram vistas juntas, sendo que o único encontro registrado terminou em conflito, com o cachorro-do-mato expulsando a raposa-do-campo. Vinte e sete táxons foram identificados na dieta dos dois canídeos. O cachorro-do-mato (n = 32 fezes) consumiu frutos, insetos (principalmente Orthoptera e Coleoptera) e vertebrados (a maioria Cricetidae e Squamata) e a raposa-do-campo (n = 23 fezes) se alimentou principalmente de cupins (Isoptera). Os resultados indicam que casais de cachorros-do-mato mantêm laços mais estreitos que casais de raposa-do-campo. A coexistência de ambas as espécies pode estar relacionada às diferenças detectadas no uso do habitat e na dieta.
Mestre em Ecologia e Conservação de Recursos Naturais

In der Studie wurde die Ernährung und die Verteilung von larvalen und juvenilen Stadien von Plötze (Rutilus rutilus (L.)) und Barsch (Perca fluviatilis L.) untersucht. Untersuchungsgewässer war der Feldberger Haussee, ein geschichteter eutropher Hardwassersee, der seit über 15 Jahren biomanipuliert wurde. Der Bestand an Barschen war in diesem Gewässer im gesamten Biomanipulationszeitraum sehr gering (&lt; 1% der Gesamtfischbiomasse). Längerfristig stabilisiert, aus wissenschafticher Sicht, eine hoher Bestand an piscivoren Barschen die Effekte der Biomanipulation. Ziel der Untersuchung war daher die Überprüfung der Hypothese, dass das Vorhandensein von Konkurrenz um die Ressource Zooplankton zwischen den juvenilen Barsch und Plötzen für den geringen Barschbestand verantwortlich ist (PERSSON &amp; GREENBERG 1990, PERSSON et al. 1991). Die Ergebnisse der Untersuchungen ließen sich in folgenden Punkten zusammenfassen: i) Der juvenile Barsch segregierte in der Hochsommer- bis Herbstperiode in eine spezielle Nahrungsnische. Die beiden Fischarten unterschieden sich deutlich bezogen auf die Art der bevorzugten Zooplankter (0+-Barsch vorwiegend Eudiaptomus, Diaphanosoma, Leptodora; 1+/2+-Plötzen fraßen Cladocerennahrung Bosmina und in hohen Anteilen auch Daphnia). Separation und Aufteilung der Zooplanktonresourcen konnte auch für die bevorzugte Größe der Zooplankter beobachtet werden. Die hohen Wachstumsraten und der gute Konditionszustand des juvenilen Barsches sowie das Fehlen von Wintermortalität ließen konkurrenzinduzierte Mortalität als Begründung für den geringen Bestand nicht glaubhaft erscheinen. ii) Die räuberbedingte saisonale Mortalität der juvenilen Barsche in der Hochsommer- bis Herbstperiode ließ sich bei den 0+-Barschen und 1+-Barschen jeweils auf bis zu 90% einschätzen. Dadurch wurde auch ein starker Jahrgang (wie 1997) innerhalb der ersten zwei Lebensjahre auf bis zu 99% reduziert. iii) Als Alternativhypothese wurde aus den Ergebnissen der Studie und den Bedingungen am Feldberger Haussee gefolgert, dass eine Kombination von langer zooplanktivorer Phase und einem hohen Bestand an effektiven pelagischen Piscivoren (wie Sander lucioperca L.) für den geringen Barschbestand verantwortlich ist
In the study the feeding behaviour and distribution of larval and juvenile stages of roach (Rutilus rutilus (L.)) and perch (Perca fluviatilis L.) was examined. The object of the study was the Lake Haussee, an stratified eutrophic hardwater lake that was biomanipulated for more than fifteen years. Over the whole period of biomanipulation the portion of perch population did not reach the level of one percent of the total fish biomass. From the scientific point of the view, a high biomass of piscivorous perch may stabilize the effects of biomanipulation in the long run. The aim of the study was to evaluate the hypothesis of strong competitive interaction between juvenile roach and perch for zooplankton, which could be responsible for the minor population of perch in lakes (PERSSON &amp; GREENBERG 1990, PERSSON et al. 1991). The results of the study can be summarised as follows: i) In the period of midsummer to autumn juvenile perch segregated to a special food niche. In comparison to 1+/2+-roach, which fed on cladocerans (e.g. Bosmina and a high portion of Daphnia), 0+-perch preferred Eudiaptomus, Diaphanosoma and Leptodora. Thus, partitioning and separation were also observed for size-selectivity. Furthermore, the high growth rates and the good state of condition of the young perch as well as the lack of winter mortality did not indicate a competitive-induced mortality in the Lake Haussee. ii) In the period of midsummer to autumn the predator-induced seasonal mortality of juvenile perch (groups like 0+/1+) was estimated nearly up to 90 percent. Thereby, also a strong age group (like 1997) of juvenile perch was reduced up to 99 percent within the first two years of life. iii) The results of this study supported an alternative hypothesis: the morphological conditions of Lake Haussee, a prolonged zooplanktivore period of juvenile perch in combination with a strong stock of an effective pelagic piscivore predator (like Sander lucioperca L.) are responsible for the low perch stock

In der Studie wurde die Ernährung und die Verteilung von larvalen und juvenilen Stadien von Plötze (Rutilus rutilus (L.)) und Barsch (Perca fluviatilis L.) untersucht. Untersuchungsgewässer war der Feldberger Haussee, ein geschichteter eutropher Hardwassersee, der seit über 15 Jahren biomanipuliert wurde. Der Bestand an Barschen war in diesem Gewässer im gesamten Biomanipulationszeitraum sehr gering (&lt; 1% der Gesamtfischbiomasse). Längerfristig stabilisiert, aus wissenschafticher Sicht, eine hoher Bestand an piscivoren Barschen die Effekte der Biomanipulation. Ziel der Untersuchung war daher die Überprüfung der Hypothese, dass das Vorhandensein von Konkurrenz um die Ressource Zooplankton zwischen den juvenilen Barsch und Plötzen für den geringen Barschbestand verantwortlich ist (PERSSON &amp; GREENBERG 1990, PERSSON et al. 1991). Die Ergebnisse der Untersuchungen ließen sich in folgenden Punkten zusammenfassen: i) Der juvenile Barsch segregierte in der Hochsommer- bis Herbstperiode in eine spezielle Nahrungsnische. Die beiden Fischarten unterschieden sich deutlich bezogen auf die Art der bevorzugten Zooplankter (0+-Barsch vorwiegend Eudiaptomus, Diaphanosoma, Leptodora; 1+/2+-Plötzen fraßen Cladocerennahrung Bosmina und in hohen Anteilen auch Daphnia). Separation und Aufteilung der Zooplanktonresourcen konnte auch für die bevorzugte Größe der Zooplankter beobachtet werden. Die hohen Wachstumsraten und der gute Konditionszustand des juvenilen Barsches sowie das Fehlen von Wintermortalität ließen konkurrenzinduzierte Mortalität als Begründung für den geringen Bestand nicht glaubhaft erscheinen. ii) Die räuberbedingte saisonale Mortalität der juvenilen Barsche in der Hochsommer- bis Herbstperiode ließ sich bei den 0+-Barschen und 1+-Barschen jeweils auf bis zu 90% einschätzen. Dadurch wurde auch ein starker Jahrgang (wie 1997) innerhalb der ersten zwei Lebensjahre auf bis zu 99% reduziert. iii) Als Alternativhypothese wurde aus den Ergebnissen der Studie und den Bedingungen am Feldberger Haussee gefolgert, dass eine Kombination von langer zooplanktivorer Phase und einem hohen Bestand an effektiven pelagischen Piscivoren (wie Sander lucioperca L.) für den geringen Barschbestand verantwortlich ist.
In the study the feeding behaviour and distribution of larval and juvenile stages of roach (Rutilus rutilus (L.)) and perch (Perca fluviatilis L.) was examined. The object of the study was the Lake Haussee, an stratified eutrophic hardwater lake that was biomanipulated for more than fifteen years. Over the whole period of biomanipulation the portion of perch population did not reach the level of one percent of the total fish biomass. From the scientific point of the view, a high biomass of piscivorous perch may stabilize the effects of biomanipulation in the long run. The aim of the study was to evaluate the hypothesis of strong competitive interaction between juvenile roach and perch for zooplankton, which could be responsible for the minor population of perch in lakes (PERSSON &amp; GREENBERG 1990, PERSSON et al. 1991). The results of the study can be summarised as follows: i) In the period of midsummer to autumn juvenile perch segregated to a special food niche. In comparison to 1+/2+-roach, which fed on cladocerans (e.g. Bosmina and a high portion of Daphnia), 0+-perch preferred Eudiaptomus, Diaphanosoma and Leptodora. Thus, partitioning and separation were also observed for size-selectivity. Furthermore, the high growth rates and the good state of condition of the young perch as well as the lack of winter mortality did not indicate a competitive-induced mortality in the Lake Haussee. ii) In the period of midsummer to autumn the predator-induced seasonal mortality of juvenile perch (groups like 0+/1+) was estimated nearly up to 90 percent. Thereby, also a strong age group (like 1997) of juvenile perch was reduced up to 99 percent within the first two years of life. iii) The results of this study supported an alternative hypothesis: the morphological conditions of Lake Haussee, a prolonged zooplanktivore period of juvenile perch in combination with a strong stock of an effective pelagic piscivore predator (like Sander lucioperca L.) are responsible for the low perch stock.

Nahrung ist eine der wichtigsten Ressourcen um die Tiere konkurrieren. Um die Anpassung von lebenden Organismen zu verstehen ist es daher von großem Interesse festzustellen, wie Individuen um solche limitierenden Ressourcen konkurrieren. Bei Säugetieren wird erwartet, dass Weibchen intensiver um Nahrungsressourcen konkurrieren als Männchen, da Weibchen im Allgemeinen geringere Fortpflanzungsraten haben, und ihre Fertilität und Fortpflanzung stärker durch ihren Ernährungszustand beeinflusst werden. Zusätzlich zu dem Einfluss von Nahrungsressourcen auf das Überleben und die Reproduktion von Individuen, schlagen sozio-ökologische Modelle vor, dass die Eigenschaften von Nahrungsressourcen die Nahrungskonkurrenz und sozialen Interaktionen zwischen Individuen und Gruppen beeinflussen, und so zu voraussagbaren Unterschieden in der Sozialstruktur von Weibchen führen. Die Validität dieser Modelle wird momentan diskutiert, da Modellvorhersagen und empirische Daten häufig voneinander abweichen. Es wird allerdings argumentiert, dass diese Unstimmigkeiten hauptsächlich daraus resultieren, dass Modellvorhersagen nur ungenau oder unvollständig überprüft und wichtige Faktoren, wie zum Beispiel konkurrenzreduzierende Mechanismen und Konkurrenz um andere limitierende Ressourcen, ausgelassen werden. Das Ziel dieser Doktorarbeit war, unser Verständnis der Zusammenhänge zwischen Nahrungseigenschaften, proximaten Mechanismen der Nahrungskonkurrenz und weiblicher Fitness zu erweitern, indem Aggression, Energieaufnahme und Reproduktion innerhalb einer Gruppe wilder Assam-Makaken (Macaca assamensis) mit Nahrungseigenschaften in Verbindung gebracht wurde. Um dieses Ziel zu erreichen, habe ich mehrere Faktoren berücksichtigt, von denen behauptet wurde, dass sie die Vorhersagekraft von sozio-ökologischen Modellen verbessern könnten. Dazu gehören Energieaufnahme und Fitness, sowie Nahrungskonkurrenz innerhalb einzelner Nahrungsquellen (food patches), konkurrenzreduzierende Mechanismen und Konkurrenz um Sicherheit. Ich habe die ultimaten Folgen der Nahrungskonkurrenz erforscht, in dem ich den Einfluss von Nahrungsverfügbarkeit auf die Energieaufnahme von Weibchen, sowie den Einfluss deren Ranges auf die Energieaufnahme, Aktivität und Reproduktion untersucht habe. Um einen Einblick in die proximaten Mechanismen der Nahrungskonkurrenz zu gewinnen, habe ich dann die Nahrungskonkurrenz innerhalb einzelner Nahrungsquellen untersucht, um den Einfluss von sozialen und ökologischen Faktoren auf die nahrungsbezogene Aggressionsrate zu erforschen. Zusätzlich habe ich Strategien untersucht, die Weibchen nutzen könnten um direkte Konflikte um Nahrung zu vermeiden. Des Weiteren habe ich untersucht, inwiefern die räumliche Verteilung von Individuen von der Gruppenaktivität und ökologischen Bedingungen abhängt, um zu beurteilen wie die Gruppe ihre Kohäsion anpassen könnte, um das beste mögliche Verhältnis zwischen Kosten und Nutzen des Lebens in einer Gruppe zu erreichen. Schlussendlich habe ich erforscht, wie Dominanzrang und Reproduktionszustand den Abstand eines Weibchen zum Mittelpunkt der Gruppe beeinflusst. Für diese Studie wurden Daten über eine Gruppe wilder Assam-Makaken im Phu Khieo Wildlife Sanctuary im Nordosten Thailands über zwei einjährige Beobachtungszeiträume erhoben (Zeitraum 1: Oktober 2007 bis September 2008; Zeitraum 2: Mai 2010 bis April 2011). Die Gruppe bestand aus insgesamt 53 Individuen, davon 12 adulte Weibchen (Zeitraum 1), bzw. aus insgesamt 49 Individuen, davon 15 adulte Weibchen (Zeitraum 2). Es wurden Fokusbeobachtungen von allen adulten Weibchen durchgeführt, und so insgesamt über 2100 Stunden Beobachtungen von Fressverhalten, Energieaufnahme, und Aktivitätsbudget erhoben, die durch Daten über Nahrungseigenschaften, weibliche Fortpflanzung, physische Verfassung und räumliche Positionen ergänzt wurden. Zusätzlich habe ich 355 Fokusbaumbeobachtungen durchgeführt, die simultane Beobachtungen aller Individuen beim Fressen in einem patch erlaubten und detaillierte Informationen über Ressourceneigenschaften, Aggressionen und die Gruppenzusammensetzung beim Fressen lieferten. Meine Studie zeigte, dass die Studienpopulation sich hauptsächlich frugivor ernährt und dass die Verfügbarkeit von Früchten sowohl die Energieaufnahme als auch die Empfängnisraten der Weibchen beeinflusst. Dies lässt darauf schließen, dass Nahrung tatsächlich eine limitierende Ressource ist. Der Einfluss des Ernährungszustandes auf die weibliche Fitness war besonders offensichtlich während der Stillperiode, welche als energieaufwändigster Teil des Reproduktionszyklus weiblicher Säugetiere betrachtet wird. Während dieses Zeitraums haben weibliche Assam-Makaken eine energiesparende Strategie verfolgt, und verlängerte Ruhezeiten gegen verkürzte Zeiten der Nahrungsaufnahme abgewogen. Der Grad, zu dem Weibchen in der Lage waren die Kosten der Laktation zu kompensieren, beeinflusste, ob sie in ausreichend guter physischer Verfassung blieben, um in der folgenden Paarungszeit erneut tragend zu werden. Dies weißt darauf hin, dass die Nahrungsverfügbarkeit während energetisch anspruchsvoller Perioden, wie z.B. der Hauptstillzeit, die weibliche Reproduktion beschränken kann. Trotz ihrer hauptsächlich frugivoren Ernährung und dem Fakt, dass Weibchen eine strikt lineare Dominanzhierarchie aufweisen, zeigen Weibchen überraschenderweise keine Rangabhängigkeit in der Energieaufnahme, des Aktivitätsbudgets oder der Reproduktion. Außerdem veränderte sich der Einfluss des Ranges eines Weibchen weder auf ihre Energieaufnahme noch auf ihre Aktivität, abhängig von der Gesamtverfügbarkeit von Früchten, Nahrungsqualität, Größe einer Nahrungsressource oder Dichte des meist verzehrten Nahrungstyps. Die Frequenz von nahrungsbezogener Aggression in Nahrungspatches erhöhte sich mit zunehmender Gruppengröße beim Fressen und abnehmender Anzahl von Futterstellen innerhalb des patches (patch size), während sie nicht durch ökologische Variablen, die den Wert von Ressourcen messen, beeinflusst wurde. Interessanterweise scheinen Weibchen mehrere Mechanismen zu nutzen, die direkte Konflikte vermeiden. Dazu gehören die Nutzung alternativer Futterstellen innerhalb von Nahrungspatches, das Speichern von Nahrung in Backentaschen und das Fressen in der Nähe von Individuen mit enger sozialer Bindung. Distanzen zwischen Individuen waren größer wenn die Gruppe fraß als wenn sie hauptsächlich ruhte, sozial interagierte oder sich bewegte. Dies beruht wahrscheinlich darauf, dass die Kosten auf Grund der Nahrungskonkurrenz mit der Nähe zunehmen. Unter den adulten Weibchen besetzten höherrangige Individuen zentralere Positionen innerhalb der Gruppe, während niederrangige Weibchen eher außen zu finden waren. Zusammenfassend vereint diese Doktorarbeit Erkenntnisse über die Zusammenhänge zwischen Ressourceneigenschaften, Verhaltensmechanismen der Nahrungskonkurrenz und Fitnesskonsequenzen in weiblichen Assam-Makaken, und gibt somit einen detaillierten Einblick in die sozialen und ökologischen Einflüsse auf Nahrungskonkurrenz und Fitness von Weibchen. Basierend auf Ressourceneigenschaften wurde vorhergesagt, dass Weibchen innerhalb der Gruppe direkte Nahrungskonkurrenz (contest competition) zeigen. Obwohl Weibchen Aggression im Zusammenhang mit Nahrung zeigen, waren die Aggressionsraten niedriger als vorhergesagt. Dies war wahrscheinlich bedingt durch den Fakt, dass Weibchen konfliktreduzierende Mechanismen nutzen, und dadurch, dass Aggressionsraten stärker durch die Größe eines Nahrungsquelles (patch size) und der Gruppengröße beim Fressen beeinflusst wurden, als durch die Dichte, die Qualität und die Verteilung der Nahrung. Weibchen haben keine Rangabhängigkeit in Hinsicht auf Energieaufnahme und Fitness gezeigt, die mit direkter Nahrungskonkurrenz innerhalb der Gruppe in Verbindung gebracht wird. Hier sind erneut die konkurrenzreduzierenden Mechanismen wichtig, da sie es niedrigrangigen Weibchen erlauben ihren Zugang zu Nahrungsressourcen zu verbessern. Dies könnte mit anderen Nachteilen verbunden sein. Niedrigrangige Weibchen besetzten zum Beispiel eher äußere Positionen, die voraussichtlich Störungen bei der Nahrungsaufnahme reduzieren, welche aber auch mit erhöhtem Prädationsrisiko verbunden sind. Dies deutet an, dass die Konkurrenz um sichere Positionen mit der Nahrungskonkurrenz interagiert und die individuelle Fitness beeinflussen kann. Um die interne Widerspruchsfreiheit von sozio-ökologischen Modellen grundlegend zu überprüfen, sind weitere Studien notwendig die detaillierte Messungen von Ressourceneigenschaften, Energieaufname und Fitness miteinbeziehen, und die konkurrenzvermeidenden Anpassungen und Konkurrenz um sonstige limitierende Ressourcen berücksichtigen.

碩士
國立中興大學
農業機械工程學系
89
In this research, the hydrophone is used to receive the sound-wave message from the cultivating tank in a water recirculating aquaculture system. The message is transmitted to a dynamic signal analyzer and then proceed the Fast Fourier Transform(FFT) to get the power spectrum characteristics of underwater sounds. The statistic test methods are applied to analyze the difference of the power spectrum characteristics under various underwater conditions. The results obtained can be described as follows: (1)The loudest sound of background noise comes from the water jet areator in the cultivating tank. When the water jet areator opened, the sound pressure would be enhanced for the frequencies between 0 and 1500Hz, and demonstrated a peak located at a frequency between 280 and 300Hz. (2)The schooling fish would influence on the sound-wave message measured.The effects may strengthen or weaken the background sound pressure due to fish swimming behaviors, and can reduce the sound pressure caused by the decay phenomenon. The sound pressure is enhanced for frequencies under 120Hz. However, the influence is only on the wave-peak and —valley as the frequency higher than 120Hz. (3)Two indexes, the root mean square(RMS) and the average sound pressure are obtained using statistic analysis methods are utilized to gauge the feeding competition of schooling eels. The root mean square(RMS) is computed for the full measured frequency range and for the subrange between 0 and 100Hz. The average sound pressure is calculated for the frequency range below 400Hz. (4)The result of the two stages feeding experiment indicates that the increases of the above two indexes are dropped as eels’ appetite decreasing. (5)The index of the average sound pressure in a frequency range between 0 and 400Hz is confirmed to be the criterion for the judgement of feeding stop using the way of several stages feeding model. The thresholds of this index for the cultivating tank A、B and C are about 2.0、1.5 and 2.0dB, respectively. (6)Comparing the results of different cultivating tank, a single background noise from one tank cannot be used for all the power spectrum analysis to evaluate scale of sound pressure changes due to feeding competition, yet should use the background noise of each cultivating tank accordingly.

Kleine blattfressende Primaten sind selten, da die Verarbeitung von Blättern oft umfangreiche Anpassungen des Verdauungsapparates und lange Retentionszeiten für die Fermentierung der Blattfasern erfordert. Dennoch basiert die Nahrung von Lepilemur leucopus (Weißfuß-Wieselmaki) auf Blättern trotz kleinem Körpergewichts (<1 kg). Um unser Verständnis darüber voranzutreiben wie kleine Blattfresser ihre Verhaltensstrategien anpassen um ihre Nahrungsbedürfnisse zu stillen, beabsichtigte ich zu untersuchen wie extrinsische (i.e. Nahrungsquantität und -qualität) und intrinsische Faktoren (i.e. Fortpflanzungsstatus) Strategien der Nahrungssuche, Nahrungswahl und soziale Interaktionen beeinflussen. Ich sammelte Daten bezüglich Aktivitätsmuster, Fressverhalten, sozialer Interaktionen und Streifverhalten in einer Population von L. leucopus in Berenty Reserve (Madagaskar) über einen kompletten Jahreszyklus. Ich erhob Daten zur Habitatstruktur und Phänologie des Dornenwaldes und sammelte Blattproben für die chemische Analyse des Nährstoffgehaltes. Es gab keine eindeutigen Anhaltspunkte, dass die saisonale Abnahme in der Nahrungsverfügbarkeit einen beträchtlichen Einfluss auf Fressverhalten oder soziale Interaktionen in L. leucopus hatte, vermutlich aufgrund der geringen Nahrungsselektivität und der Nutzung der am häufigsten im Wald vorkommenden Pflanzenarten, und Nahrungsstress stand wahrscheinlich eher mit Nahrungsqualität als -quantität in Verbindung. Nahrungsprotein scheint nur begrenzt zur Verfügung gestanden zu haben, da L. leucopus Protein- gegenüber nicht-Protein-Aufnahme über Jahreszeiten und Reproduktionsstadien hinweg priorisierte. Da Veränderungen hinsichtlich Aktivitätsmuster und sozialer Interaktionen nicht im Zusammenhang mit Nahrungsknappheit standen, scheinen Bottom-Up-Prozesse weniger wichtig als Top-Down-Prozesse für die Formgebung des sozialen Systems von L. leucopus zu sein. Die Ergebnisse unterstützen außerdem die Idee, dass quantitative Nahrungsknappheit während der Trockenzeit eine untergeordnet Rolle gegenüber Blattqualität als Selektionsdruck für blattfressende Primatenpopulationen spielt.

Folivores do not exhibit a direct relationship between group size and daily path length and are consequently believed to experience little feeding competition. However, previous studies lacked sufficient control for ecological variation and did not account for the underlying hierarchical structure inherent in closely related taxa (phylogeny). The present analysis examined daily path length and relative ranging cost in 37 primate species, including 18 folivores, while controlling for ecological variation and phylogeny. Group size effects on group spread, changes in activity budget, and infant to female ratios were similarly investigated as these have been found to indicate feeding competition in folivorous primates. Although relative ranging cost was a not a significant predictor of folivore group size, large groups traveled significantly farther per day, increased group spread per individual, and had lower infant to female ratios than small groups. Large groups spent more time feeding and less time resting than small groups; however, these trends were not significant. A strong phylogenetic signal was detected among species’ mean values for average group size (λ = 0.827). Because primate group size and behavior represent the combination of adapting to present-day environments and phylogenetic inertia, future comparative analyses of feeding competition should account for both current ecological conditions and the phylogenetic signals inherent in the taxa being compared. As suggested by the current study, folivorous primates may utilize a number of foraging strategies, other than increasing daily path length, to alleviate feeding competition. To better assess feeding competition, future research should include alternative correlates of feeding competition such as increased group spread, changes in activity budgets, and decreased female fecundity. The information gained from such research may improve our current interpretations of the ‘folivore paradox’ and redefine the competitive regime of leaf eating primates.
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Dissertação de Mestrado
This experience was conducted to test and analyse the pig behaviour and welfare in their competition for the facilities (feeders, drinkers and rooting machines), analysing as much as possible the drinking, feeding and rooting behaviours in two different pen sizes (single/double) and animal densities. Video observations during 3 months (January, February and March of 2007) were made in twelve pens with different number of animals to study behaviour measures in the different densities of 1.2, 1.8 and 2.4 m2 per animal. The observations follow the fattening period until the days before the slaughter. The results reached help to conclude that agonistic, interactive, inactive and sexual behaviours between pigs are generally higher in single pens, in the feeders and in the 1.2 density group. The drinkers were the facility where less behaviour was detected. The feeders are the facility where pigs are generally more aggressive and the total number of aggressive interactions in the feeders is also affected by group size and number of hoppers. The rooting machine beside some significant agonistic behaviour observed, promotes the socialization between pigs, and consequently is a good device to decrease or avoid behaviours of frustration and stress. The results reached in this trial are similar to other studies made before with growing pigs.

Beluga whales (Delphinapterus leucas) and narwhals (Monodon monoceros) are arctic specialists. Both species show philopatry to their summer grounds, though the reason for this site tenacity is not well understood. Aside from migration routes, little is known about other aspects of monodontid ecology, such as their mating and feeding ecology. An understanding of the feeding ecology of a species may provide some insights into their mating ecology, and vice versa. The purpose of this thesis is to relative testes mass and dietary biomarkers to gain insights in the mating and feeding ecology of both species, as well as possible links between the two. Relative testes and brain masses and body masses of odontocetes were collected from the literature and analysed for correlations between sexual size dimorphism (SSD), relative brain mass, and relative testes mass. Results indicate that odontocete species follow a pattern of increasing SSD with decreasing testes mass. An examination of reproductive tracts from belugas and narwhal collected across the Canadian arctic was performed to examine differences in beluga and narwhal mating systems. Belugas were found to have larger relative testes masses, and narwhal testes masses were correlated with tusk length, indicating that sperm competition may play a larger role in the beluga mating system than for narwhal, and narwhal tusks may be honest indicators of male fitness. Investigations of narwhal and beluga feeding ecology using dietary biomarkers were conducted. In the summer, belugas appear to be congregating and feeding in the estuary plume during the summer, as opposed to along ice floe edges in the spring. Spring diets are representative of diets consumed during the beluga mating season, and no sexual segregation in carbon isotopes or fatty acids was apparent. There was no evidence for sexual segregation in feeding habits outside the mating season, either. Conversely, narwhal showed some evidence of sexual segregation outside the mating season, and the sexes may be feeding in different food webs. Results suggest that belugas may have a more promiscuous mating system, while narwhals are more polygynous. Implications for conservation for both species are discussed.

Diet and female feeding competition was examined within two groups of free-ranging ringtailed lemurs (Lemur catta) at the Beza Mahafaly Special Reserve in southwestern Madagascar. The first group’s home range was located within a protected gallery forest, the second is in a degraded forest and human-occupied area. The diets of the females were found to vary between groups; females fed on different plant species, and those in the unprotected area frequently consumed human food scraps and domestic animal fecal matter. Contest and scramble competition were detected within both groups. Rates of feeding competition were found to increase according to the type of food being consumed; feeding on fruits and leaves correlated with increased competition in the reserve group, and feeding on human foods and animal fecal matter correlated with increased competition with the non-reserve group. These dietary and competitive differences highlight the need for continued, and possibly additional, protection of L. catta in this region.

Wie Tiere ein kollektives Handeln zur Revierverteidigung erreichen und wie sie Beziehungen zwischen benachbarten Gruppen aufbauen ist in letzter Zeit zu einem zentralen Thema in der Verhaltensforschung geworden. Die Stärke einer Gruppe kann von mehreren Faktoren beeinflusst werden, sowohl auf der Gruppen- als auch auf der Individuenebene. In dieser Dissertation untersuchte ich verschiedene Aspekte der Beziehungen zwischen acht Gruppen von Larvensifakas im Westen Madagaskars. Von 2012 bis 2014 wurden detaillierte Verhaltensdaten, ökologische und demographische Daten aufgenommen, um einerseits die Faktoren zu untersuchen, die die individuelle Teilnahme beeinflussen und anderseits die Prädiktoren zu identifizieren, die den positiven Ausgang einer Zwischengruppenbegegnung vorhersagen. Faktoren wie Geschlecht, Alter, Anwesenheit von Jungtieren, Fortpflanzungsstadien und zahlenmäßige Gewinnchancen wurden als mögliche Prädiktoren für die individuelle Teilnahme an Begegnungen zwischen Gruppen getestet. In der Untersuchung der Prädiktoren für den Ausgang bestimmte ich den Einfluss einer zahlenmäßigen Überlegenheit und des Ortes der Begegnung. Zusätzlich ermittelte ich die saisonalen Schwankungen in der Verfügbarkeit von Nahrung im Forschungsgebiet und wie sich diese Saisonalität auf die Nahrungszusammensetzung und die Energieaufnahme der männlichen und weiblichen Sifakas auswirkt. Meinen Ergebnissen zufolge beteiligen sich beide Geschlechter an der Verteidigung der Gruppe. Der bedeutendste Anreiz für die Teilnahme war die effektive Größe der gegnerischen Gruppe (Anzahl der Individuen, die sich an der Auseinandersetzung beteiligen). Trittbrettfahren war häufig: Während sich bei den Männchen vor allem Tiere mit niedrigem Rang weniger beteiligten, waren es bei den Weibchen vor allem diejenigen mit unselbstständigen Jungtieren. Der Ort der Begegnung war ein essentieller Prädiktor für die Chance einen Konflikt zu gewinnen, im Gegensatz zur zahlenmäßigen Überlegenheit. Die Saisonalität hatte einen signifikanten Einfluss auf die Ernährung beider Geschlechter. Interessanterweise war die Nahrung der Weibchen von höherer Qualität als die der Männchen, was wahrscheinlich mit den für die Weibchen höheren Kosten der Fortpflanzung zusammenhängt. Im Gegensatz zu den meisten Primatenweibchen sind weibliche Sifakas stark an der Gruppenverteidigung beteiligt. Soziale Dominanz, körperliche Kraft und die hohen Kosten der Fortpflanzung in einem Lebensraum mit extremen saisonalen Klimaschwankungen gehören zu den Faktoren, die mit der, in meiner Studie beobachteten hohen Beteiligung von Weibchen an Gruppenbegegnungen zusammenhängen. In dieser Studie waren die variablen Umstände einer Begegnung, wie deren Ort und die effektive Größe der gegnerischen Gruppe, die wichtigsten Prädiktoren für die Teilnahme an einer Gruppenbegegnung und für deren Ausgang. Diese Ergebnisse unterstützen die Hypothese, dass andere Faktoren als eine zahlenmäßige Überlegenheit entscheidend für die Teilnahme an einer Gruppenbegegnung und deren Ausgang sein können. Demzufolge müssen ökologische und individuelle Eigenschaften einbezogen werden, um ein besseres Verständnis der Beziehungen zwischen Gruppen zu erreichen.

A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg in fulfillment of the requirements for the degree of Masters in Science. Johannesburg, August 2016.
Resource selection by herbivores is driven by processes operating across a multitude of spatial scales and is influenced by a variety of biotic and abiotic environmental conditions and resources across the landscape. Spatial scales levels are crucial in habitat selection studies because they affect the interpretation of results and what may appear important at one level may not be relevant at another. Decisions made by animals at these levels can influence animal movements and hence the spatial distribution of populations. In this way, the use of resources across different scales by individual and groups of animals can be linked to population performance as a whole. Within home ranges, habitat use is mostly influenced by variation of food resources and water availability together with competition and predation risk. The study aimed to determine sable home range extent and habitat use and to test how predation, competition and other environmental factors influenced the selection of areas within these home ranges, in the thriving sable population of the Gorongosa National Park (GNP), Mozambique. Two adult females, one per herd, were fitted with GPS collar providing 5 hours interval GPS coordinates over a year, which were used to determine the annual and seasonal home ranges extents. Home ranges were then overlaid with vegetation map to analyse habitat use. Contrary to expectation, sable home ranges in this study were larger than those found in previous studies. The herds did not limit their habitat use to woodlands, using also open grasslands, drainage lines and bottomlands that retained green grasses during the dry season. Both herds expanded their ranges during the dry season, searching for those areas that still retained green grasses and searching for remaining water sources. For the resources selection within home ranges, I used the same GPS collar coordinates to fit seasonal logistic regression models with biotic factors (predation risk and competition) and with environmental variables (distance from water, distance from roads, elevation, slope, NDVI, vegetation types and landscape). Results show that sable were less prevalent in areas with high predation risk, but herds differed in prevalence with competitors, one herd favouring areas with high reedbuck concentrations and the other favouring low concentrations. Effects of environmental variables were different between seasons and between herds, being distance from water, distance from roads, greenness and elevation the most influential environmental. Both herds, however, avoided low elevation areas during the wet season, probably in order to avoid areas flooded during this period. As conclusion, predation risk and competition influenced selection within home ranges by sable in the GNP, despite low densities of potential competitors and lions. Nevertheless, this influence seems to not be enough yet to limit the success of the population. The herds also showed evidences of being affected by dry season, as demonstrated by the home ranges expansions during this period. With increase of herbivores population other that sable, and consequently increase competition and decrease of availability of resources, this could lead to reduction of growths percentages of the sable population in the park in the future.
MT2018

Tese de doutoramento em Biociências, na especialidade de Ecologia, apresentada ao Departamento de Ciências da Vida da Faculdade de Ciências e Tecnologia da Universidade de Coimbra
A competição interespecífica é um importante mecanismo controlador da evolução das espécies, uma vez que pode moldar o comportamento dos indivíduos e, em última instância, afectar as suas dinâmicas populacionais. Espécies com uma longa história de coevolução, que sejam potenciais competidoras, desenvolveram alguns mecanismos que permitiram a sua coexistência especial, tal como a partição dos recursos ecológicos utilizados e a territorialidade heterospecífica. A competição interespecífica pode ocorrer também entre espécies que iniciaram o contacto há relativamente pouco tempo, como é o caso das espécies nativas e das exóticas introduzidas pelos humanos. Apesar da importância da competição interespecífica na estruturação das comunidades, esta tem sido relativamente pouco estudada. A escassez de conhecimento acerca da competição interespecífica realça a necessidade do aumento do estudo acerca da agressividade e das relações de dominância entre espécies muito distantes do ponto de vista taxonómico. Consequentemente, eu decidi elaborar um estudo acerca da competição comparando a sua intensidade entre conspecíficos e espécies taxonomicamente-distantes. Como principais espécies em estudo, seleccionei duas espécies de aves Passeriformes taxonomicamente-distantes, o pisco-de-peito-ruivo (Erithacus rubecula; Familia Muscicapidae) e a toutinegra-de-barrete (Sylvia atricapilla; Familia Sylviidae), duas espécies potencialmente competidoras por habitat e alimento. Para analisar as interacções com uma espécie recentemente introduzida, também realizei algumas experiências com o rouxinol do Japão (Leiothrix lutea; Familia Timaliidae), uma espécie exótica, nativa da Ásia, e que é um potencial competidor das duas primeiras espécies. O principal objectivo da tese foi procurar provas de competição entre essas espécies. Uma vez encontradas, também tentei compreender as adaptações ecológicas e comportamentais que contribuem para reduzi-la. Os objectivos detalhados foram: (1) analisar as semelhanças no uso de habitat entre o pisco-de-peito-ruivo e a toutinegra-de-barrete em coexistência e isolamento com o objectivo de verificar existência de segregação no uso de habitat; (2) quantificar os níveis de agressividade no pisco-de-peito-ruivo e na toutinegra-de-barrete relativamente aos conspecíficos e heterospecíficos, quando competem por alimento; (3) identificar as vantagens adaptativas potenciais do rouxinol do Japão durante o seu processo de estabelecimento numa comunidade de espécies nativas através do estudo de características morfológicas e comportamentais; (4) estudar a dominância comportamental do rouxinol do Japão sobre espécies nativas de Passeriformes num contexto alimentar; (5) testar o uso do canto do pisco-de-peito-ruivo e da toutinegra-de-barrete como sinal agressivo para os heterospecíficos utilizando playbacks do canto de diferentes espécies nos seus territórios, incluindo um competidor nativo, competidor exótico e não-competidor. Eu obtive provas complementares de competição interspecífica entre as espécies estudadas. Os principais resultados foram: (a) ocorrência de segregação de habitat entre o pisco-de-peito-ruivo e a toutinegra-de-barrete, (2) a obtenção de níveis relativamente altos de agressividade heterospecífica entre essas duas espécies, (c) uma grande sobreposição de nicho morfológico entre o rouxinol do Japão e – principalmente – o pisco-de-peito-ruivo, (d) dominância comportamental do rouxinol do Japão sobre as espécies nativas em contexto alimentar, e (e) o uso do canto pelo pisco-de-peito-ruivo e a toutinegra-de-barrete como sinal agressivo aos heterospecíficos. Estes resultados são relativamente inovadores, uma vez que: (i) encontrei apenas outros dois estudos considerando a hipótese da competição interespecífica como estando na origem da divergência de habitat entre espécies taxonomicamente distantes; (ii) obtive resultados de características morfológicas potencialmente vantajosas de uma espécie colonizadora dentro de uma comunidade de aves, o que constitui um tópico pouco estudado; (iii) do meu conhecimento, esta tese poderá incluir o primeiro estudo experimental onde a clara dominância de uma espécie exótica de ave sobre espécies nativas foi confirmada em contexto alimentar. A principal conclusão desta tese é que a competição interespecífica pode ocorrer entre espécies taxonomicamente distantes e que esta é passível de ser medida. Através do uso do pisco-de-peito-ruivo e da toutinegra-de-barrete como espécies modelo para o estudo da competição interespecífica, demonstrei que espécies distantes que coevoluíram e coexistem nos meus habitats podem apresentar importantes níveis de agressividade heterospecífica – por vezes tão intensa como a que ocorre entre conspecifícos – e desenvolveram alguns mecanismos de modo a evitar a competição interespecífica, como seja a segregação de habitat. Demonstrei também que o rouxinol do Japão é dominante sobre as espécies nativas, tal como o pisco-de-peito-ruivo e a toutinegra-de-barrete, o que poderá contribuir para explicar o seu rápido estabelecimento na Europa. Este trabalho destaca (1) o papel importante da competição pelo uso do espaço entre espécies que coevoluiram, mas que são taxonomicamente distantes e (2) a capacidade das espécies nativas lidarem com uma espécie competidora alienígena.
Interspecific competition is an important mechanism contributing to the evolution of species as it can shape the behaviour of individuals, and ultimately affect population dynamics. Species with a long-term coevolution history, which are potential competitors, developed some mechanisms which allow their spatial coexistence, such as resource partitioning or interspecific territoriality. Interspecific competition can occur not only among species with a long-term coevolution, but also between species which have a relatively recent contact, such as the case of native species and species introduced by humans. Despite the relevance of interspecific competition on the evolution of species and structuring of communities, it has been relatively neglected. The lack of knowledge about interspecific competition highlights the need to increase the research on aggression and dominance relationship between distantly related species. Therefore, I decided to conduct a study on competition comparing its intensity between conspecifics and distantly related species. As main study species, I selected two distantly related passerine species, the robin (Erithacus rubecula; Family Muscicapidae) and the blackcap (Sylvia atricapilla; Family Sylviidae), that are potential competitors for habitat and feeding resources. To analyse the interactions with a recently-introduced species, I also conducted some experiments with the red-billed leiothrix (Leiothrix lutea; Family Timaliidae), an exotic species introduced from Asia, which is a potential competitor with the first two species. The main objective of this thesis was to found evidence of competition between these species and, once found, I also tried to understand the ecological and behavioural adaptations that can contribute to reduce it. The detailed objectives were: (1) to analyse similarities in the habitat used by the robin and blackcap in coexistence and in isolation aiming to test the existence of habitat shifting between them; (2) to quantify the levels of aggressiveness in the robin and the blackcap towards conspecifics and heterospecifics, while competing for food; (3) to identify the potential competitive advantages of the red-billed leiothrix during the establishment process in a community of native passerines by collecting morphological and behavioural data; (4) to study the behavioural dominance of red-billed leiothrix over native passerines in a feeding context; (5) to test the use of singing behaviour by the robin and the blackcap as an aggressive signal towards heterospecifics using song playbacks of different species in their natural territories, including native competitors, exotic-competitors and non-competitor species. I found complementary evidences of interspecific competition among the study species. The main results of the thesis were: (a) the occurrence of habitat shifting between the robin and the blackcap, (b) the relatively high levels of heterospecific aggression between the robin and the blackcap, (c) a high overlap of the morphological niche between the leiothrix and (mainly) the robin, (d) behavioural dominance of the leiothrix over native species in feeding context, and (e) the use of song by the robin and the blackcap as a signal of aggressiveness towards some heterospecifics. These results are relatively novel since: (i) I found only two studies considering the hypothesis of interspecific competition as being in the origin of habitat divergence between distantly related species; (ii) I found a possible advantageous effect of morphological traits of a colonizer species within a bird community which was seldom studied; (iii) to the best of my knowledge, I conducted the first experimental work where clear dominance by an exotic bird species over native rivals was confirmed in a feeding context. The main conclusion of this thesis is that interspecific competition can occur between distantly related species and that it is possible to measure it. By using the robin and the blackcap as models to study interspecific competition, I demonstrated that distantly related species which coevolved and coexist in the same habitats can show important levels of heterospecific aggression – sometimes as intense as among conspecifics – and developed some mechanisms to reduce interspecific competition, such as habitat shift. I also demonstrated that the leiothrix is dominant over native species, such as the robin and the blackcap, which perhaps contributes to justify why it is becoming established so rapidly in Europe. This work highlights (1) the important role of interspecific competition in the use of space between distantly related species that coevolved, and (2) the ability of the native species to deal with a newcomer competing species.