Abstract: In recent years evidence has been accumulating that personalities are not only found in humans but also in a wide range of other animal species. Individuals differ consistently in their behavioural tendencies and the behaviour in one context is correlated with the behaviour in multiple other contexts. From an adaptive perspective, the evolution of animal personalities is still a mystery, because a more flexible structure of behaviour should provide a selective advantage. Accordingly, many researchers view personalities as resulting from constraints imposed by the architecture of behaviour (but see ref. 12). In contrast, we show here that animal personalities can be given an adaptive explanation. Our argument is based on the insight that the trade-off between current and future reproduction often results in polymorphic populations in which some individuals put more emphasis on future fitness returns than others. Life-history theory predicts that such differences in fitness expectations should result in systematic differences in risk-taking behaviour. Individuals with high future expectations (who have much to lose) should be more risk-averse than individuals with low expectations. This applies to all kinds of risky situations, so individuals should consistently differ in their behaviour. By means of an evolutionary model we demonstrate that this basic principle results in the evolution of animal personalities. It simultaneously explains the coexistence of behavioural types, the consistency of behaviour through time and the structure of behavioural correlations across contexts. Moreover, it explains the common finding that explorative behaviour and risk-related traits like boldness and aggressiveness are common characteristics of animal personalities.

Abstract: Management of grazed grasslands for production and/or conservation objectives requires a thorough understanding of the choices of feeding sites by herbivores, and of the biological processes involved. Most models of the feeding strategies of herbivores are based on the principle that optimising the intake of energy (or some nutrient) is the primary goal of foragers but other selective forces, such as parasitism, could be important. Gastrointestinal parasites (including cyathostome nematodes) have powerful effects on the fitness of herbivores and may act as a major selection pressure favouring host behaviour that reduces the risk of encountering parasites. Among large herbivores, horses have perhaps the most marked tendency to select particular feeding sites within grasslands. We test here: (1) whether horses select feeding patches with relatively low parasite densities and (2) if their choice is affected by their parasite load. We used 10 two-year old saddle-horses and three periods. In the first period, the horses were under natural parasitism which varied strongly among individuals; in the second period they were all dewormed, and in the third, a sub-set of the horses was experimentally infected with cyathostome larvae. Ninety-eight percent of the infective larvae in the pasture were found <1 m from faeces. The main determinant of the choice of feeding patch by horses was the availability of patches of different parasite risk and grass height. Controlling for availability, the horses used tall grasses (>16 cm) less than expected, whether the grass was contaminated or not, and they selected for short patches >1 m from faeces, where the risk of encountering parasites was low. These results suggest that selection of feeding sites by horses is driven by an interaction between their nutritional and anti-parasite strategies: the horses avoid the patches of tall grass which are generally of low quality and areas contaminated by parasite larvae which leads them to prefer the patches of short grass far from faeces. The parasite status of the horses at the time of the experiment had no effect on their feeding choices. However, before concluding that the challenge by cyathostomes has no effect on the selection of feeding sites in horses, it will be necessary to test whether the history of parasitism of the individuals, rather than the current status, is important.

Abstract: A cross-sectional seroepidemiologic study was carried out between 1985 and 1990 in 1,567 heterosexual intravenous drug users who had been seen at the AIDS Regional Reference Center in Palermo, Italy, to evaluate the rate of human immunodeficiency virus type 1 (HIV-1) seroprevalence in this group and its long-term trend. Sixty serum samples collected from drug users in 1980 and 1983, before the founding of the Center (1985), were tested as well. Some demographic and behavioral risk factors were studied in a subgroup of intravenous drug users enrolled in 1985, 1987, and 1990 for their possible association with HIV-1. These factors were also studied in relation to hepatitis B virus infection, since both viruses share the same modes of spread. These drug users had a higher prevalence of markers for hepatitis B virus than of HIV-1 antibodies, and the prevalence rates in sera collected declined over time for both infections. The presence of both antibodies to HIV-1 and markers for hepatitis B virus was independently associated with the age of the drug user, the duration of drug use, and the year of serum collection. Antibodies to HIV-1 were observed more frequently in females than in males. No relation was found between education or employment status and the presence of HIV-1 antibodies or hepatitis B virus markers. Although new HIV-1 infections still occur, the decline in seroprevalence observed at the end of the 1980s might be related to modifications in social behavior among newer drug users, partial exhaustion of the susceptible population, and increasing risk awareness in more experienced users.

Abstract: Horses are a highly social species living in complex social systems which should require them to memorise and generalise social experiences and distinguish between familiar and unfamiliar conspecifics. In the main part of my thesis I concentrated on the specific conflict situation of a horse being introduced into a new social group, and investigated its behaviour and stress level. Horses were either introduced (1) immediately, (2) after an observation period, or (3) together with an integration horse after an observation period. Additionally, in the second part of my thesis I arranged several experiments to elaborate additional aspects which could affect the behaviour of horses during introductions. In this study I could describe a simplified method for measuring stress through the analysis of faecal GCMs in horses. An enzyme immunoassay (EIA) for 11-oxoaetiocholanolone using 11-oxoaetiocholanolone-17-CMO: BSA (3?,11-oxo-A EIA) as antigen showed high amounts of immunoreactive substances. The new assay increases the accuracy of the test and lowers the expenses per sample; also storing of samples at room temperature after collection is less critical. This is a big advantage both in the field of wildlife management of equids and in the field of equestrian sports (chapter 1). Comparing the different introduction techniques, the introduction with an integration horse led to significantly less total interactions and lower levels of aggression than the introduction of single horses, both immediately and after several days of observing the new group. Additionally, by observing the behaviour of the horses during everyday sociality I could develop a formula describing the interrelationship between expected aggression level and enclosure size per horse. The curve takes an exponential shape. Starting from a space allowance of 300 m2 and more per horse, the amount of aggressions per hour approaches zero. For the reduction of aggression levels and injury risks in socially kept horses I recommend an enclosure size of at least 300 m2 per horse (chapter 2). I further investigated the stress level of the introduced animals. Horses which were immediately introduced did not show elevated faecal GCMs. In contrast, horses which were introduced after an observation period had slightly elevated values 2 and 3 days after the introduction. For horses introduced together with an integration horse faecal GCMs were significantly above the baseline value on the day of introduction and 1 day after it. These differences between introduction techniques indicate that the introduction event itself is not as stressful as previously assumed. Rather standing together with an integration horse and not being able to integrate immediately into the complete group elicits stress in horses (chapter 3). In the commentary of chapter 4 several studies are discussed which failed to demonstrate social learning in horses. It is argued that they did not consider important aspects which could have an influence, such as the dominance status or the social background of the horses (chapter 4). In chapter 5 a social feeding situation was investigated. The social rank as well as the position of conspecifics affected the feeding strategy of horses. Domestic horses used social cognition and strategic decision making in order to decide where to feed. When possible they tended to return to the same, continuously supplied feeding site and switched to an ?avoidance tendency? in the presence of dominant horses or when another horse was already feeding there (chapter 5). One possibility to recognize group members is through olfactory recognition. In chapter 6 it is shown that horses are able to distinguish their own from their conspecifics? faeces. In addition, they paid most attention to the faeces of those group members from which they received the highest amount of aggressive behaviour (chapter 6). Horses show cognitive abilities because they are able to use humans as local enhancement cues when searching for food, independently of their body posture or gaze consistency when the persons face them. Moreover, they seem to orientate on the attention of familiar persons more than of unfamiliar persons (chapter 7). Altogether, the results of this thesis provide further support for the view that horses show good conflict resolution strategies. They are perfectly able to deal with the conflict situation of being introduced to new group members, and the introduction event itself is not as stressful as previously assumed. It is rather suggested that standing together with an integration horse and not being able to integrate immediately into the complete group elicits stress in horses. All additional experimental set-ups could demonstrate that horses are well capable of social cognition.

Abstract: Ziel: Überprüfung der Tiergerechtheit von in der Bauweise unterschiedlichen
Futterabrufstationen für Pferde in Gruppenhaltung anhand ethologischer
und physiologischer Parameter. Material und Methoden: In 32
Offenlaufställen (452 Pferde) mit computergesteuerten Abrufstationen
für Kraftfutter und Heu erfolgten kontinuierliche Direktbeobachtungen
für je einen 24-Stunden-Tag (Tortenstückverfahren). Erfasst wurden: Aufenthaltsdauer,
Besuchshäufigkeit, Droh- und Meideverhalten im Fütterungsbereich,
Blockaden sowie Herzfrequenz und Integumentverletzungen.
Ergebnisse: Eine Durchlaufstation reduzierte die Zahl der Auseinandersetzungen
im Fütterungsbereich signifikant. Ansonsten erhöhten die
für das fressende Pferd tiergerechten Varianten (Fressstand mit Eingangssperre,
ohne Austreibehilfe) Besuchshäufigkeit und Aufenthaltsdauer und
steigerten somit auch die Anzahl an Drohgesten je Tier und Tag. Insgesamt
betrachtet kann jedoch die Anzahl an sozionegativen Interaktionen
im Fütterungsbereich der Abrufstationen als relativ gering eingestuft
werden. Die Herzfrequenz lag im Warteareal bei den meisten Pferden im
physiologischen Bereich (45,1 ± 12,42 Schläge/min), erhöhte sich jedoch
in der Abrufstation um ca. 20 Schläge/min. Einige Tiere zeigten möglicherweise
stressbedingt kurzfristig auffallend hohe Werte (&#8805; 100 Schläge/
min). Integumentverletzungen im Zusammenhang mit dem Fütterungssystem
traten nicht auf. Der wichtigste Einflussfaktor auf die Untersuchungskriterien
war der Betrieb (Fläche, Konzeption, Management).
Schlussfolgerung: Durchlaufstationen sind pferdegerechter als Rücklaufstationen.
Nicht tiergerecht sind Stationen mit stromführender Austreibehilfe.
Weitere bauliche Unterschiede der derzeitigen Futterabrufstationen
dürften eher von untergeordneter Bedeutung sein, vor allem da
Flächengebot und Konzeption der Offenstallanlage sowie das Management
die überprüften Kriterien zur Tiergerechtheit maßgeblich beeinflussen.
Untersuchungen zur Abklärung der Ursache für die vereinzelt aufgetretenen
sehr hohen Herzfrequenzwerte sollten durchgeführt werden.
Objective: Comparison with regard to animal welfare of different automatic
feeding systems for hay and concentrate in group housing systems
for horses using parameters of ethology and physiology. Material and
methods: Parameters of research comprised: duration of stay, frequency
of visit, threatening behaviour with and without risk of injury, and avoiding
behaviour as well as heart rate and injuries of the integument. 452
horses were observed at the feeding area of 32 run-out-sheds. Every group
of horses was continuously observed following the pie chart system for
24 hours. Results: The “walk-through” station significantly reduced the
number of conflicts in the feeding area, whereas those systems which are
appropriate for the feeding horses (feeding station with access barrier and
without stimulation device by electric shock) led to a higher frequency of
visits and a longer duration of stay resulting in more threatening gestures.
However, the number of negative interactions in the feeding area of the
feeding systems can all together be classified as relatively insignificant.
The heart rate was within the physiological range (45.1 ± 12.42 beats/min)
in the waiting area, but increased by approximately 20 beats/min on average
within the feeding station. Some horses showed a very high heart rate
(&#8805; 100 beats/min) while entering the feeding station, possibly stress-related.
There were no injuries of the integument associated with the feeding
systems. The most important factor of the observation criteria was the
individual group housing system with its different dimensions, conception
and management. Conclusion: “Walk-through” stations are better than
”walk-back” stations with regard to animal welfare. Likewise, automatic
feeding stations with a current-carrying stimulation device are not supportive
of good welfare. The other differences between the constructions
of feeding stations of present systems are probably of less importance, particularly
as it was shown that the stable (management, stable area, conception)
had a significant influence on the surveyed parameters. Investigations
to obtain information on the cause for the sporadic occurrence of
very high heart rate values should be undertaken.]